1. An electric multi-mode steer-by-wire system, comprising:

a steering wheel unit for a driver to manipulate an input steering action, comprising: the steering wheel, the torque angle sensor, the road sensing motor reducing mechanism, the electromagnetic clutch, the torsion bar, the steering driving shaft, the upper transmission shaft, the pin, the first steering universal joint, the second steering universal joint and the lower transmission shaft, wherein the road sensing reducing mechanism adopts a worm and gear type reducing mechanism;

the steering execution unit is used for executing the steering action of the vehicle wheels, and comprises: the steering system comprises left and right steering wheels, a first steering execution motor mechanism, a second steering execution motor mechanism, a steering gear, a first lead screw position sensor, a second lead screw position sensor, a first electromagnetic switch valve, a second electromagnetic switch valve and an oil tank; the upper end of the steering gear is connected with the steering wheel unit, the left end and the right end of the steering gear are respectively connected with the first steering executing motor mechanism and the second steering executing motor mechanism, the first steering executing motor mechanism and the second steering executing motor mechanism are respectively connected with the left steering wheel and the right steering wheel through steering tie rods, the cores of the first steering executing motor mechanism and the second steering executing motor mechanism are both hollow motor and lead screw nut motion conversion mechanisms, and the first electromagnetic switch valve and the second electromagnetic switch valve are respectively connected with an oil pipe of the oil tank and can control whether the oil way is communicated with the oil tank or not;

the mode selection and display unit is used for manual steering mode selection and state display and comprises three mode selection buttons and a central control screen, wherein the three mode selection buttons are respectively as follows: an I button, a II button and a III button;

and the electronic control unit is used for receiving a state signal and sending a control command, is respectively connected with the road sensing motor, the torque and angle sensor, the electromagnetic clutch, the first steering executing motor mechanism, the second steering executing motor mechanism, the first lead screw position sensor, the second lead screw position sensor, the first electromagnetic switch valve, the second electromagnetic switch valve and the three mode selection button signal lines, and is connected with the CAN communication line of the central control screen.

2. An electric multi-mode steer-by-wire system according to claim 1, wherein said one electric multi-mode steer-by-wire system is automatically controlled by said electronic control unit based on vehicle dynamics and steer-by-wire actuator failure conditions, or is manually operated by a driver to implement three steering modes:

mode one, namely a wire control independent steering mode of each wheel;

mode two, namely the steer-by-wire trapezoidal steering mode;

mode three, i.e., electric power steering mode;

the second mode and the third mode play a role in the first mode for the failure protection backup, and the third mode also plays a role in the second mode for the failure protection backup.

3. An electric multi-mode steer-by-wire system according to claim 1, wherein in said steering wheel unit, said road sensing motor is connected to said upper drive shaft through said road sensing motor reduction gear, said upper drive shaft upper end is connected to said torsion bar and said lower end of said steering drive shaft through said pin, said torque angle sensor is mounted on said steering drive shaft, said upper end of said steering drive shaft is connected to said steering wheel, said upper end of said upper drive shaft is connected to said upper end of said electromagnetic clutch through said first steering universal joint, and said lower end of said electromagnetic clutch is connected to said lower drive shaft through said second steering universal joint.

4. An electric, multi-mode steer-by-wire system of claim 1, wherein said first and second steering actuator motor mechanisms comprise:

the first motor shell is connected with the steering gear through a bolt;

the second motor shell is connected with the steering gear through a bolt;

the first motor end cover is connected with the first motor shell through a bolt;

the second motor end cover is connected with the second motor shell through a bolt;

the first motor stator is fixed on the inner wall of the first motor shell;

the second motor stator is fixed on the inner wall of the second motor shell;

the central inner hole of the first motor rotor is provided with threads and is connected to the first motor shell through a bearing support;

the central inner hole of the second motor rotor is provided with threads and is connected to the second motor shell through a bearing support;

the first lead screw is internally provided with a hollow hydraulic cavity with a small hole at the bottom, the outer cylinder of the first lead screw is processed with threads and is matched with the first motor rotor to form a sliding lead screw pair mechanism, so that the rotation of the first motor rotor is converted into the translation of the first lead screw;

the inner part of the second lead screw is a hollow hydraulic cavity with a small hole at the bottom, the outer cylinder of the second lead screw is processed with threads and is matched with the second motor rotor to form a sliding lead screw pair mechanism, so that the rotation of the second motor rotor is converted into the translation of the second lead screw;

a first O-ring seal disposed within the first lead screw for sealing an internal hydraulic chamber of the first lead screw;

a second O-ring seal disposed within the second lead screw for sealing an internal hydraulic chamber of the second lead screw;

the first oil hoop is fixed on a small hole at the bottom of the first lead screw, so that the internal hydraulic chamber of the first lead screw is connected with a pipeline of the first electromagnetic switch valve;

and the second oil hoop is fixed on a small hole at the bottom of the second lead screw, so that the internal hydraulic chamber of the second lead screw is connected with the pipeline of the second electromagnetic switch valve.

5. An electric multi-mode steer-by-wire system of claim 1, wherein said steering gear comprises:

the steering gear shell is used for accommodating parts of the steering gear assembly, two ends of the steering gear shell are respectively connected with the first motor shell and the second motor shell to form two chambers, and a moving space is reserved for the first lead screw and the second lead screw when the first lead screw and the second lead screw move and contract;

the steering gear shaft is arranged on the inner wall of the steering gear shell through a bearing, the upper end of the steering gear shaft is mechanically connected with the lower transmission shaft through a universal joint and transmits steering torque, and a gear is machined in the middle of the steering gear shaft;

the end cover is fixedly connected with the steering gear shell through a bolt;

a seal ring installed between the end cap and the steering gear shaft to seal grease;

a steering gear shaft nut connected to the steering gear shaft by a screw pair;

the end cover nut is connected with the steering gear shell through a thread pair;

a rack support seat;

the rack is in supporting connection with the steering gear shell through the rack supporting seat and the bushing, is in meshing transmission with the gear in the middle of the steering gear shaft, and is respectively sealed with two ends of the first lead screw and the second lead screw to form a hydraulic cylinder;

the adjusting screw plug is screwed into the steering gear shell in a threaded manner, and compresses the rack supporting seat through a compression spring to eliminate a transmission gap of a rack and pinion;

and the adjusting plug screw locking nut is used for locking the adjusting plug screw.

6. An electric multi-mode steer-by-wire system mode switching method, comprising:

step one, performing system self-inspection, and recording failure states of a motor I and a motor II;

reading the state of a driver mode selection signal;

step three, judging whether the driver selects the mode; if not, jumping to the step six;

step four, judging whether the mode selection signal is a mode one; if yes, jumping to the step six;

judging whether the mode selection signal is in a second mode; if not, jumping to the seventh step;

step six, judging the following conditions according to the failure states of the first motor and the second motor and the state of the driver mode selection signal:

if the first motor and the second motor are not invalid and the mode selection state of the driver is off or the mode one, jumping to the step eight;

if one motor is not in failure and the mode selection state of the driver is off or the mode II, jumping to the step seven;

if the first motor and the second motor are both invalid and the mode selection state of the driver is off, jumping to the step ten;

if the first motor and the second motor are both invalid and the mode selection state of the driver is the mode two, jumping to the step fourteen;

if the first motor fails and the mode signal selected by the driver is the first mode, jumping to the step twelve;

if the motor II fails and the mode signal selected by the driver at present is the mode I, jumping to the step thirteen;

step seven, judging whether the previous cycle is in the mode one, and judging the following conditions:

if so, jumping to the step eleven and then adjusting to the step nine if the mode selection state of the driver is not the mode three;

if not, and the mode selection state of the driver is not the mode three, directly jumping to the step nine;

if yes, and the mode selection state of the driver is a mode three, jumping to the step eleven and then adjusting to the step ten;

if not, and the mode selection state of the driver is the mode three, directly jumping to the step ten;

step eight, entering a mode one processing subprogram;

step nine, entering a mode two processing subprogram;

step ten, entering a mode three processing subprogram;

step eleven, entering an angle compensation centering subprogram;

step twelve, outputting a prompt instruction that 'the mode selection cannot be completed when the motor fails, and the mode is switched or the maintenance is required in time';

step thirteen, outputting a prompt instruction that the motor II fails to complete the selection of the first mode and requires the mode to be switched or the maintenance to be carried out in time;

step fourteen, outputting a prompt instruction that the first motor and the second motor fail to complete the selection of the second mode, and please switch the modes or maintain in time;

and step fifteen, ending and returning.

7. An electric multi-mode steer-by-wire system mode switching method according to claim 6, wherein said mode-one processing subroutine is:

step one, switching off an electromagnetic clutch;

step two, opening the first electromagnetic switch valve and the second electromagnetic switch valve;

reading steering wheel rotation angle and torque signals;

respectively generating a left steering wheel steering angle signal and a right steering wheel steering angle signal according to the steering dynamics requirement of the whole vehicle and the current vehicle state;

step five, respectively calculating according to the angular transmission ratio relation of the steering executing motor mechanisms to obtain the corner control instructions of the left steering executing motor and the right steering executing motor;

step six, respectively transmitting the rotation angle control instruction of the steering execution motor to the first motor and the second motor, and feeding back the state signals of the first motor and the second motor to step four;

seventhly, the left steering wheel and the right steering wheel finish independent steering respectively, and wheel rotation angle state signals are fed back to the third step respectively;

the routine is ended.

8. The electric multi-mode steer-by-wire system mode switching method of claim 6, wherein the mode two processing subroutine is:

step one, switching off an electromagnetic clutch;

step two, closing the first electromagnetic switch valve and the second electromagnetic switch valve;

reading steering wheel rotation angle and torque signals;

generating a common steering wheel steering angle signal according to the steering dynamics requirement of the whole vehicle and the current vehicle state;

calculating according to the angular transmission ratio relation of the steering execution motor mechanism to obtain a corner control instruction of the current effective steering execution motor;

step six, transmitting the rotation angle control instruction of the effective steering execution motor to the effective steering execution motor, and feeding back state signals of the motor I and the motor II;

seventhly, the left steering wheel and the right steering wheel finish steering together according to a steering trapezoidal relation, and a wheel corner state signal is fed back to the third step;

the routine is ended.

9. The electric multi-mode steer-by-wire system mode switching method according to claim 6, wherein the mode three processing subroutine is:

step one, engaging an electromagnetic clutch;

step two, closing the first electromagnetic switch valve and the second electromagnetic switch valve;

reading steering wheel rotation angle and torque signals;

looking up a table according to the current vehicle speed and the current steering wheel torque signal to generate a steering power-assisted signal;

calculating to generate a current control instruction of the road sensing motor according to the required steering power-assisted signal and the speed ratio of the speed reducing mechanism of the road sensing motor;

step six, transmitting the current control instruction of the road sensing motor to the road sensing motor, and feeding back a state signal of the road sensing motor to step four;

step seven, the road sensing motor power-assisted driver operates the left steering wheel and the right steering wheel according to the steering trapezoidal relation to complete steering, and the turning angle state of the wheels is fed back to step three;

the routine is ended.

10. An electric multi-mode steer-by-wire system mode switching method according to claim 6, wherein the angle compensation vs. neutron routine is:

step one, closing a failure side electromagnetic switch valve, and closing the electromagnetic switch valve at one end with a smaller wheel rotation angle if no failure motor exists;

reading a wheel corner signal of the wheel at the failure side or the side with a smaller wheel corner, and calculating the wheel corner of the other side through a steering trapezoidal geometric relationship;

step three, calculating a target rotation angle control instruction of the non-failure side or the side with larger rotation angle of the steering execution motor according to the angular transmission ratio relation of the steering execution motor mechanism;

opening the electromagnetic switch valve on the non-failure side or the side with larger rotation angle;

step five, inputting a target corner control command to the steering motor on the non-failure side or the side with larger corner;

step six, judging whether the wheel corner is the same as the target corner control instruction or not, and if the wheel corner is different from the target corner control instruction, returning to the step three;

step seven, closing the electromagnetic switch valve on the non-failure side or the side with larger rotation angle;

the routine is ended.

Background

Nowadays, the wire control technology is increasingly popularized, and the application of the wire control technology in the field of vehicle steering is increasingly wide. As a key technology for guaranteeing the active safety and the operation stability of energy-saving and new energy automobiles and intelligent networked automobiles, the steer-by-wire system can improve the safety performance of the automobiles, removes mechanical connections such as steering columns and the like, and completely avoids the damage of the steering columns to drivers in the event of collision; the intelligent steer-by-wire system can judge whether the operation of the driver is reasonable according to the running state of the automobile, and make corresponding adjustment, so that the driving characteristics and the maneuverability are improved, the road feel of the driver is improved, and the comfort of the automobile is enhanced. The drive-by-wire steering system cancels all mechanical connection between a steering wheel unit and a steering execution unit, a control system judges the driving intention of a driver according to a sensor sensing signal, a steering power source is only provided by a steering motor, and road information can be obtained by a road feel simulation motor, so that sufficient road sensing is provided for the driver, and meanwhile, the interference and driving fatigue caused by unnecessary road bumping transmitted to the steering wheel by the road feel simulation motor are avoided. In addition, the steer-by-wire system can freely design the force and angle transmission characteristics of the automobile steering, so the contradiction between lightness and flexibility in the design of the transmission ratio of the steering system can be fundamentally solved, and the arrangement space of the cab can be greatly optimized by the saved part of steering operation mechanisms. At present, a steer-by-wire system without mechanical connection better meets the technical requirements of unmanned driving and automatic parking of intelligent vehicles, and provides an optimal solution for realizing advanced technologies such as automatic driving, unmanned driving, intelligent auxiliary driving and the like. However, the steering executing part of the existing steer-by-wire system still keeps the traditional steering trapezoid structure of the steering device to realize geometric steering movement, and the corner decoupling of the left wheel and the right wheel cannot be realized; and only rely on the redundant backup of electronic system, lack the redundant backup structure of machinery, the mode of operation is single, can't continue to accomplish the action of turning to under the condition that the electric electronic element of system is invalid, there is the risk of failure, influence the security of the whole steer-by-wire.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides an electric multi-mode steer-by-wire system and a mode switching method thereof, wherein the system belongs to a novel distributed steer-by-wire structure and can automatically realize three steering working modes, namely an independent steer-by-wire wheel mode, a steer-by-wire trapezoidal steering mode and an electric power steering mode, by an electronic control unit control system according to a vehicle dynamic state and a steer-by-wire actuator fault failure state or a driver manually realizes the three steering working modes by operating three mode selection buttons; the system realizes the problem of coupling of left and right wheel steering angles in the steering system, simultaneously realizes the redundant backup of the steering system structure, can still ensure to smoothly complete the steering action under the condition that electronic elements or electrical equipment of the system fails, and greatly improves the safety of the steer-by-wire system.

The technical scheme of the invention is as follows by combining the attached drawings of the specification:

an electric multi-mode steer-by-wire system comprises a steering wheel unit I, an electronic control unit II, a steering execution unit III and a mode selection and display unit IV;

the steering wheel unit I is used for a driver to operate and input steering action and consists of a steering wheel (38), a torque and angle sensor (4), a road sensing motor (1), a road sensing motor speed reducing mechanism (A), an electromagnetic clutch (15), a torsion bar (6), a steering driving shaft (7), an upper transmission shaft (8), a pin (5), a first steering universal joint (14), a second steering universal joint (16) and a lower transmission shaft (17); the road sensing motor speed reducing mechanism (A) adopts a worm and gear speed reducing mechanism;

the steering execution unit III is used for executing wheel steering actions and consists of a left steering wheel, a right steering wheel (39), a first steering execution motor mechanism (B), a second steering execution motor mechanism (C), a steering gear (D), a first lead screw position sensor (40), a second lead screw position sensor (41), a first electromagnetic switch valve (42), a second electromagnetic switch valve (43) and an oil tank (44); the upper end of the steering gear (D) is connected with the steering wheel unit I, the left end and the right end of the steering gear (D) are respectively connected with the first steering executing motor mechanism (B) and the second steering executing motor mechanism (C), the first steering executing motor mechanism (B) and the second steering executing motor mechanism (C) are respectively connected with the left steering wheel (39) and the right steering wheel (39) through a steering tie rod, the cores of the first steering executing motor mechanism (B) and the second steering executing motor mechanism (C) are both hollow motors and lead screw nut motion conversion mechanisms, the first electromagnetic switch valve (42) and the second electromagnetic switch valve (43) are respectively connected with the oil pipe of the oil tank (44), and whether the oil way is communicated with the oil tank (44) or not can be controlled;

the mode selection and display unit IV is used for manual steering mode selection and state display and comprises three mode selection buttons (75) and a central control screen (74), wherein the three mode selection buttons (75) are respectively: an I button, a II button and a III button;

the electronic control unit II is used for receiving state signals and sending control instructions, and is respectively connected with the road sensing motor (1), the torque and rotation angle sensor (4), the electromagnetic clutch (15), the first steering executing motor mechanism (B), the second steering executing motor mechanism (C), the first lead screw position sensor (40), the second lead screw position sensor (41), the first electromagnetic switch valve (42), the second electromagnetic switch valve (43) and the three mode selection buttons (75) through signal lines and connected with the CAN communication line of the central control screen (74).

Preferably, the electric multi-mode steer-by-wire system can be automatically realized by the electronic control unit II according to the dynamic state of the vehicle and the failure state of the steer-by-wire actuator, or the driver can manually realize three steering operation modes by operating the three mode selection buttons (75):

mode one, namely a wire control independent steering mode of each wheel;

mode two, namely the steer-by-wire trapezoidal steering mode;

mode three, i.e., electric power steering mode;

the second mode and the third mode play a role in the first mode for the failure protection backup, and the third mode also plays a role in the second mode for the failure protection backup.

Preferably, in the steering wheel unit I, the road sensing motor (1) passes through road sensing motor reduction gears (A) with go up transmission shaft (8) and link to each other, go up transmission shaft (8) upper end and pass through pin (5) with torsion bar (6) with turn to driving shaft (7) lower extreme and link to each other, install torque angle sensor (4) turn to on driving shaft (7), turn to driving shaft (7) upper end with steering wheel (38) link to each other, go up transmission shaft (8) lower extreme and pass through first turning universal joint (14) with electromagnetic clutch (15) upper end links to each other, electromagnetic clutch (15) lower extreme passes through second turning universal joint (16) with lower transmission shaft (17) link to each other.

Preferably, the first steering actuator motor mechanism (B) and the second steering actuator motor mechanism (C) include: a first motor housing (71) connected to the steering gear (D) by a bolt; a second motor housing (72) connected to the steering gear (D) by a bolt; a first motor end cover (69) connected to the first motor housing (71) by bolts; a second motor end cap (70) coupled to the second motor housing (72) by bolts; a first motor stator (26) fixed to an inner wall of the first motor housing (71); a second motor stator (34) fixed on the inner wall of the second motor shell (72); the central inner hole of the first motor rotor (24) is processed with threads and is connected to the first motor shell (71) through a bearing support; the central inner hole of the second motor rotor (32) is processed with threads and is connected to the second motor shell (72) through a bearing support; the first lead screw (27) is internally provided with a hollow hydraulic chamber with a small hole at the bottom, the outer cylinder of the first lead screw is processed with threads and is matched with the first motor rotor (24) to form a sliding lead screw pair mechanism, so that the rotation of the first motor rotor (24) is converted into the translation of the first lead screw (27); the inner part of the second lead screw (35) is a hollow hydraulic cavity with a small hole at the bottom, the outer cylinder of the second lead screw is processed with threads and is matched with the second motor rotor (32) to form a sliding lead screw pair mechanism, so that the rotation of the second motor rotor (32) is converted into the translation of the second lead screw (35); a first O-ring seal (28) disposed inside the first lead screw (27) for sealing an internal hydraulic chamber of the first lead screw (27); a second O-ring seal (36) disposed inside the second leadscrew (35) for sealing an internal hydraulic chamber of the second leadscrew (35); the first oil hoop (63) is fixed on a small hole at the bottom of the first lead screw (27) to realize the pipeline connection between an internal hydraulic chamber of the first lead screw (27) and the first electromagnetic switch valve (42); and the second oil hoop (64) is fixed on a small hole at the bottom of the second lead screw (35) to realize the pipeline connection of the internal hydraulic chamber of the second lead screw (35) and the second electromagnetic switch valve (43).

Preferably, the steering gear (D) includes: the steering gear shell (22) is used for accommodating each part of the steering gear (D) assembly, and two ends of the steering gear shell are respectively connected with the first motor shell (71) and the second motor shell (72) to form two chambers which are used for reserving a moving space for the first lead screw (27) and the second lead screw (35) to move and contract; the steering gear shaft (20) is arranged on the inner wall of the steering gear shell (22) through a bearing, the upper end of the steering gear shaft is mechanically connected with the lower transmission shaft (17) through a universal joint and transmits steering torque, and a gear is machined in the middle of the steering gear shaft; an end cover (51) fixedly connected to the steering gear housing (22) by a bolt; a seal ring (56) installed between the end cap (51) and the steering gear shaft (20) to seal grease; a steering gear shaft nut (54) connected to the steering gear shaft (20) by a thread pair; an end cap nut (55) connected to the steering housing (22) by a thread pair; a rack support base (57); the rack (21) is in supporting connection with the steering gear shell (22) through the rack supporting seat (57) and a bushing, is in meshing transmission with a gear in the middle of the steering gear shaft (20), and is respectively sealed with two ends of the first lead screw (27) and the second lead screw (35) to form a hydraulic cylinder; an adjusting screw plug (58) which is screwed into the steering gear shell (22) and presses the rack supporting seat (57) through a pressing spring so as to eliminate a rack-and-pinion transmission gap;

an adjusting plug lock nut (61) for locking the adjusting plug (58).

A mode switching method of an electric multi-mode steer-by-wire system is used for a mode switching main control program of three steering modes, a steer-by-wire independent steering mode (mode one) control subprogram of each wheel, a steer-by-wire trapezoidal steering mode (mode two) control subprogram and an electric power steering mode (mode three) control subprogram, and the specific processes are respectively as follows:

the mode switching main control program of the three steering modes is as follows:

step one, performing system self-inspection, and recording failure states of a motor I and a motor II;

reading the state of a driver mode selection signal;

step three, judging whether the driver selects the mode; if not, jumping to the step six;

step four, judging whether the mode selection signal is a mode one; if yes, jumping to the step six;

judging whether the mode selection signal is in a second mode; if not, jumping to the seventh step;

step six, judging the following conditions according to the failure states of the first motor and the second motor and the state of the driver mode selection signal:

if the first motor and the second motor are not invalid and the mode selection state of the driver is off or the mode one, jumping to the step eight;

if one motor is not in failure and the mode selection state of the driver is off or the mode II, jumping to the step seven;

if the first motor and the second motor are both invalid and the mode selection state of the driver is off, jumping to the step ten;

if the first motor and the second motor are both invalid and the mode selection state of the driver is the mode two, jumping to the step fourteen;

if the first motor fails and the mode signal selected by the driver is the first mode, jumping to the step twelve;

if the motor II fails and the mode signal selected by the driver at present is the mode I, jumping to the step thirteen;

step seven, judging whether the previous cycle is in the mode one, and judging the following conditions:

if so, jumping to the step eleven and then adjusting to the step nine if the mode selection state of the driver is not the mode three;

if not, and the mode selection state of the driver is not the mode three, directly jumping to the step nine;

if yes, and the mode selection state of the driver is a mode three, jumping to the step eleven and then adjusting to the step ten;

if not, and the mode selection state of the driver is the mode three, directly jumping to the step ten;

step eight, entering a mode one processing subprogram;

step nine, entering a mode two processing subprogram;

step ten, entering a mode three processing subprogram;

step eleven, entering an angle compensation centering subprogram;

step twelve, outputting a prompt instruction that 'the mode selection cannot be completed when the motor fails, and the mode is switched or the maintenance is required in time';

step thirteen, outputting a prompt instruction that the motor II fails to complete the selection of the first mode and requires the mode to be switched or the maintenance to be carried out in time;

step fourteen, outputting a prompt instruction that the first motor and the second motor fail to complete the selection of the second mode, and please switch the modes or maintain in time;

and step fifteen, ending and returning.

Preferably, the "angle compensation versus neutron procedure" in the eleventh step is as follows:

step one, closing a failure side electromagnetic switch valve, and closing the electromagnetic switch valve at one end with a smaller wheel rotation angle if no failure motor exists;

reading a wheel corner signal of the wheel at the failure side or the side with a smaller wheel corner, and calculating the wheel corner of the other side through a steering trapezoidal geometric relationship;

step three, calculating a target rotation angle control instruction of the non-failure side or the side with larger rotation angle of the steering execution motor according to the angular transmission ratio relation of the steering execution motor mechanism;

opening the electromagnetic switch valve on the non-failure side or the side with larger rotation angle;

step five, inputting a target corner control command to the steering motor on the non-failure side or the side with larger corner;

step six, judging whether the wheel corner is the same as the target corner control instruction or not, and if the wheel corner is different from the target corner control instruction, returning to the step three;

step seven, closing the electromagnetic switch valve on the non-failure side or the side with larger rotation angle;

the routine is ended.

Preferably, the control subroutine for the steer-by-wire independent-each-wheel mode (the mode one) is as follows:

step one, switching off an electromagnetic clutch;

step two, opening the first electromagnetic switch valve and the second electromagnetic switch valve;

reading steering wheel rotation angle and torque signals;

respectively generating a left steering wheel steering angle signal and a right steering wheel steering angle signal according to the steering dynamics requirement of the whole vehicle and the current vehicle state;

step five, respectively calculating according to the angular transmission ratio relation of the steering executing motor mechanisms to obtain the corner control instructions of the left steering executing motor and the right steering executing motor;

step six, respectively transmitting the rotation angle control instruction of the steering execution motor to the first motor and the second motor, and feeding back the state signals of the first motor and the second motor to step four;

seventhly, the left steering wheel and the right steering wheel finish independent steering respectively, and wheel rotation angle state signals are fed back to the third step respectively;

the routine is ended.

Preferably, the steer-by-wire trapezoidal steering mode (the mode two) control subroutine is as follows:

step one, switching off an electromagnetic clutch;

step two, closing the first electromagnetic switch valve and the second electromagnetic switch valve;

reading steering wheel rotation angle and torque signals;

generating a common steering wheel steering angle signal according to the steering dynamics requirement of the whole vehicle and the current vehicle state;

calculating according to the angular transmission ratio relation of the steering execution motor mechanism to obtain a corner control instruction of the current effective steering execution motor;

step six, transmitting the rotation angle control instruction of the effective steering execution motor to the effective steering execution motor, and feeding back state signals of the motor I and the motor II;

seventhly, the left steering wheel and the right steering wheel finish steering together according to a steering trapezoidal relation, and a wheel corner state signal is fed back to the third step;

the routine is ended.

Preferably, the electric power steering mode (the mode three) control subroutine is as follows:

step one, engaging an electromagnetic clutch;

step two, closing the first electromagnetic switch valve and the second electromagnetic switch valve;

reading steering wheel rotation angle and torque signals;

looking up a table according to the current vehicle speed and the current steering wheel torque signal to generate a steering power-assisted signal;

calculating to generate a current control instruction of the road sensing motor according to the required steering power-assisted signal and the speed ratio of the speed reducing mechanism of the road sensing motor;

step six, transmitting the current control instruction of the road sensing motor to the road sensing motor, and feeding back a state signal of the road sensing motor to step four;

step seven, the road sensing motor power-assisted driver operates the left steering wheel and the right steering wheel according to the steering trapezoidal relation to complete steering, and the turning angle state of the wheels is fed back to step three;

the routine is ended.

Compared with the prior art, the invention has the beneficial effects that:

1. the electric multi-mode steer-by-wire system can realize three steering working modes, namely a steer-by-wire independent steering mode of each wheel, a steer-by-wire trapezoidal steering mode and an electric power-assisted steering mode. The first two of these are steer-by-wire modes, i.e. the steering wheel is completely mechanically decoupled from the steered wheels; the latter is a conventional electric power-assisted mechanical steering mode, i.e. the steering wheel is mechanically connected to the steering actuation unit and the steering wheel.

2. The electric multi-mode steer-by-wire system and the mode switching method thereof can automatically complete the safe switching of three steering working modes under the condition that key components of the steer-by-wire system fail, improve the redundancy safety of the steer-by-wire system and enhance the continuous driving service capability under the failure protection.

3. The electric multi-mode steer-by-wire system and the mode switching method thereof can manually complete the safe switching of three steering working modes according to the requirement of a driver on the flexible steering of the automobile under the condition of normal driving working, provide more choices for the driver and greatly enrich the driving pleasure.

4. The electric multi-mode steer-by-wire system coaxially integrates the steering driving motor and the steering gear assembly, greatly reduces the space occupied by the steer-by-wire mechanism and provides space for the arrangement of other parts on the vehicle.

5. According to the electric multi-mode steer-by-wire system and the mode switching method thereof, the display screen and the mode selection switch thereof which are specially used for displaying the steering state/fault information are added, so that the man-machine interaction capability and the user decision permission in the field of chassis control are increased.

Drawings

The invention will be further described with reference to the following drawings and examples of embodiments, which are intended to illustrate, but not to limit the invention.

FIG. 1: the invention relates to a structural composition block diagram of an electric multi-mode steer-by-wire system

FIG. 2: the invention relates to a mechanical structure diagram of an electric multi-mode steer-by-wire system

FIG. 3: in the electric multi-mode steer-by-wire system according to the present invention, a steering structure diagram

FIG. 4: in the electric multi-mode steer-by-wire system of the present invention, the structure diagram of the speed reducing mechanism of the road feel motor

FIG. 5: in the electric multi-mode steer-by-wire system, the appearance structure chart of the shell of the steering gear

FIG. 6: in the mode switching method of the electric multi-mode steer-by-wire system, the invention adopts a logic flow chart of a main program

FIG. 7: in the mode switching method of the electric multi-mode steer-by-wire system, the invention adopts a mode-subprogram logic flow chart

FIG. 8: in the mode switching method of the electric multi-mode steer-by-wire system, the logic flow chart of the mode two subprogram

FIG. 9: in the mode switching method of the electric multi-mode steer-by-wire system, the logic flow chart of the three-mode subprogram

FIG. 10: in the mode switching method of the electric multi-mode steer-by-wire system, the logic flow chart of an angle compensation centering subprogram

In the figure:

i-steering wheel unit, II-electronic control unit, III-steering execution unit, IV-mode selection and display unit

A-road sensing motor speed reducing mechanism, B-first steering executing motor mechanism, C-second steering executing motor mechanism, D-steering gear road sensing motor (1), reducer upper shell (2), first deep groove ball bearing (3), torque and corner sensor (4), pin (5), torsion bar (6), steering driving shaft (7), upper transmission shaft (8), worm wheel (9), reducer lower shell (10), second deep groove ball bearing (11), key (12), spacer bush (13), first steering universal joint (14), electromagnetic clutch (15), second steering universal joint (16), lower transmission shaft (17), third steering universal joint (18), second bolt (19), steering gear shaft (20), rack (21), steering gear shell (22), third deep groove ball bearing (23), first motor rotor (24), The steering wheel comprises a fourth deep groove ball bearing (25), a first motor stator (26), a first lead screw (27), a first O-shaped sealing ring (28), a first rack bushing (29), a first bolt (30), a fifth deep groove ball bearing (31), a second motor rotor (32), a sixth deep groove ball bearing (33), a second motor stator (34), a second lead screw (35), a second O-shaped sealing ring (36), a second rack bushing (37), a steering wheel (38), left and right steering wheels (39), a first lead screw position sensor (40), a second lead screw position sensor (41), a first electromagnetic switch valve (42), a second electromagnetic switch valve (43), an oil tank (44), a seventh deep groove ball bearing (45), a third bolt (46), a coupler (47), an eighth deep groove ball bearing (48), a worm (49), a fourth bolt (50), an end cover (51), a ninth deep groove ball bearing (52), A tenth deep groove ball bearing (53), a steering gear shaft nut (54), an end cover nut (55), a first sealing ring (56), a rack supporting seat (57), an adjusting screw plug (58), a spring (59), a gasket (60), an adjusting screw plug locking nut (61), a seventh bolt (62), a first oil hoop (63), a second oil hoop (64), a second sealing ring (65), a third sealing ring (66), a fifth bolt (67), a sixth bolt (68), a first motor end cover (69), a second motor end cover (70), a first motor shell (71), a second motor shell (72), an ECU (73), a central control screen (74), and three mode selection buttons (75)

Detailed Description

Exemplary embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

The technical scheme of the invention is as follows by combining the attached drawings of the specification:

as shown in fig. 1, an electric multi-mode steer-by-wire system is composed of a steering wheel unit I, an electronic control unit II, a steering execution unit III and a mode selection and display unit IV;

as shown in fig. 2, the steering wheel unit I is composed of a steering wheel (38), a torque angle sensor (4), a road sensing motor (1), a road sensing motor reduction gear (a), an electromagnetic clutch (15), a torsion bar (6), a steering driving shaft (7), an upper transmission shaft (8), a pin (5), a first steering universal joint (14), a second steering universal joint (16) and a lower transmission shaft (17); the road sensing motor speed reducing mechanism (A) adopts a worm and gear speed reducing mechanism.

As shown in fig. 2 and 4, the road sensing motor speed reducing mechanism (a) is composed of a coupling (47), a seventh deep groove ball bearing (45), an eighth deep groove ball bearing (48), a worm (49), a worm wheel (9), a first deep groove ball bearing (3), a second deep groove ball bearing (11), a speed reducer upper shell (2) and a speed reducer lower shell (10); an output shaft of the road sensing motor (1) is coaxially connected with a worm (49) through a coupler (47), the worm (49) is supported and fixed on a lower shell (10) of the speed reducer through a seventh deep groove ball bearing (45) and an eighth deep groove ball bearing (48), a worm wheel (9) is in meshing transmission with the worm (49), the worm wheel (9) is connected onto an upper transmission shaft (8) through a key (12), the upper end of the worm wheel (9) is limited through a shaft step, and the lower end of the worm wheel (9) is limited through a spacer bush (13) and a second deep groove ball bearing (11); the upper transmission shaft (8) is respectively supported and fixed on the upper shell (2) and the lower shell (10) of the speed reducer through a first deep groove ball bearing (3) and a second deep groove ball bearing (11).

As shown in fig. 2, the road sensing motor (1) is fixedly connected to the lower shell (10) of the speed reducer through a third bolt (46), and the lower shell (10) of the speed reducer and the upper shell (2) of the speed reducer are fixedly connected together through a seventh bolt (62); the lower end of a steering driving shaft (7) is sleeved at the upper end of a torsion rod (6), a gap is reserved between the steering driving shaft (7) and the torsion rod (6) along the radial direction, the upper end of an upper transmission shaft (8) is sleeved at the lower end of the torsion rod (6), a gap is reserved between the upper transmission shaft (8) and the torsion rod (6) along the radial direction, the steering driving shaft (7) and the torsion rod (6) and the upper transmission shaft (8) and the torsion rod (6) are respectively connected through a pin (5), so that the torque of the steering driving shaft (7) is elastically transmitted to the upper transmission shaft (8) through the torsion rod (6) to provide relative torsional deformation for a torque corner sensor (4), and the input torque of a steering wheel (38) is measured; the upper end of the upper transmission shaft (8) is supported and connected to the inner wall of the upper shell (2) of the speed reducer through a first deep groove ball bearing (3), and the lower end of the upper transmission shaft (8) is supported and connected to the inner wall of the lower shell (10) of the speed reducer through a second deep groove ball bearing (11); the road sensing motor (1) is connected with a road sensing motor speed reducing mechanism (A) and then is in meshing transmission with a steering driving shaft (7), and a torque corner sensor (4) is arranged on the steering driving shaft (7) and used for measuring the corner and the torque input by a steering wheel (38); the upper end of a steering driving shaft (7) is connected with a steering wheel (38), the lower end of the steering driving shaft (7) is connected with the upper end of an upper transmission shaft (8) through a torsion bar (6), the lower end of the upper transmission shaft (8) is connected with one end of an electromagnetic clutch (15) through a first steering universal joint (14), and the other end of the electromagnetic clutch (15) is connected with a lower transmission shaft (17) through a second steering universal joint (16).

As shown in fig. 1 and 2, the steering actuator unit III is composed of left and right steering wheels (39), a first steering actuator motor mechanism (B), a second steering actuator motor mechanism (C), a steering gear (D), a first lead screw position sensor (40), a second lead screw position sensor (41), a first electromagnetic switch valve (42), a second electromagnetic switch valve (43), and an oil tank (44). The core of the first steering executing motor mechanism (B) and the second steering executing motor mechanism (C) is a motion conversion mechanism of a hollow motor and a screw nut, and the first steering executing motor mechanism (B) and the second steering executing motor mechanism (C) comprise a first motor shell (71), a second motor shell (72), a first motor stator (26), a second motor stator (34), a first motor rotor (24), a second motor rotor (32), a first lead screw (27), a second lead screw (35), a fifth bolt (67), a sixth bolt (68), a first motor end cover (69), a second motor end cover (70), a first oil hoop (63), a second oil hoop (64), a first O-shaped sealing ring (28), a second O-shaped sealing ring (36), a first bolt (30), a second bolt (19), a third deep groove ball bearing (23), a fourth deep groove ball bearing (25), A fifth deep groove ball bearing (31) and a sixth deep groove ball bearing (33). The first motor shell (71) and the second motor shell (72) are respectively connected with two ends of a steering gear shell (22) of a steering gear (D) through a first bolt (30) and a second bolt (19); the first motor end cover (69) and the second motor end cover (70) are respectively connected with a first motor shell (71) and a second motor shell (72) through a fifth bolt (67) and a sixth bolt (68); the first motor stator (26) is fixed on the inner wall of the first motor shell (71), and the second motor stator (34) is fixed on the inner wall of the second motor shell (72); the first motor rotor (24) and the second motor rotor (32) are respectively supported on a first motor shell (71) and a second motor shell (72) through a third deep groove ball bearing (23), a fourth deep groove ball bearing (25), a fifth deep groove ball bearing (31) and a sixth deep groove ball bearing (33), the surfaces of hollow inner cylinders in the first motor rotor (24) and the second motor rotor (32) are processed into threaded structures, the sliding screw rod pairs are respectively connected with a first screw rod (27) and a second screw rod (35) to realize a motion conversion function, and the rotation of the motor rotors can be converted into the translation of the screw rods; a first lead screw position sensor (40) and a second lead screw position sensor (41) are respectively fixed at the outer ends of a first motor end cover (69) of the first steering actuating mechanism and a second motor end cover (70) of the second steering actuating motor mechanism and used for detecting the telescopic translation distance of a first lead screw (27) and a second lead screw (35) penetrating out of a central hole, so that the actual rotating angle of a left steering wheel and a right steering wheel is calculated according to the transmission ratio of the wheel-side steering transmission mechanism; threaded holes are processed in the centers of the outer end parts of the first lead screw (27) and the second lead screw (35) respectively and are used for installing ball head pins respectively and connecting with the ball heads of knuckle arms of the left and right steering wheels (39) through a steering tie rod respectively to drive the two steering wheels to deflect integrally or independently, so that the function of converting the translation of the lead screw into the rotation of the left and right steering wheels around respective main pins of the left and right steering wheels is realized; the interiors of the first lead screw (27) and the second lead screw (35) are hollow structures, controllable and closed hydraulic chambers (also called hydraulic cylinders) filled with hydraulic oil are formed at the two ends of the interior of the steering gear (D) respectively, and sealing is achieved through a first O-shaped sealing ring (28) and a second O-shaped sealing ring (36) respectively; the outer ends of the first lead screw (27) and the second lead screw (35) are provided with small oil holes for respectively fixing an oil hoop (63) and an oil hoop (64) in a threaded mode, the hydraulic chambers in the lead screws are respectively connected with an oil tank (44) through the first oil hoop (63) and the second oil hoop (64) through oil pipes, and the middles of the hydraulic chambers are respectively connected with a first electromagnetic switch valve (42) and a second electromagnetic switch valve (43) in series. Opening and closing of the first electromagnetic switch valve (42) and the second electromagnetic switch valve (43) can control whether a hydraulic chamber formed by the first lead screw (27) and one end of the steering gear (D) and a hydraulic chamber formed by the second lead screw (35) and the other end of the steering gear (D) are communicated with the oil tank (44), so that whether the first lead screw (27) is fixedly connected with one end of the steering gear (D) or not and whether the second lead screw (35) is fixedly connected with the other end of the steering gear (D) or not are achieved.

As shown in fig. 3, the steering gear (D) is composed of a fourth bolt (50), an end cap (51), a ninth deep groove ball bearing (52), a tenth deep groove ball bearing (53), a steering gear shaft nut (54), an end cap nut (55), a seal ring (56), a rack support seat (57), a first rack bushing (29), a second rack bushing (37), an adjusting plug screw (58), a compression spring (59), a gasket (60), an adjusting plug screw locking nut (61), a steering gear shaft (20), a rack (21) and a steering gear housing (22). A gear is processed in the middle of the steering gear shaft (20), the steering gear shaft is installed on the inner wall of the steering gear shell (22) through a ninth deep groove ball bearing (52) and a tenth deep groove ball bearing (53), and the upper end of the steering gear shaft is mechanically connected with the lower transmission shaft (17) through a third steering universal joint (18) and transmits steering torque; the end cover (51) is fixedly connected to the steering gear shell (22) through a fourth bolt (50) and used for limiting a ninth deep groove ball bearing (52); the sealing ring (56) is arranged between the end cover (51) and the steering gear shaft (20) and plays a role in sealing lubricating grease in the steering gear; the steering gear shaft nut (54) is connected with the steering gear shaft (20) through a thread pair and used for locking a tenth deep groove ball bearing (53) arranged on the steering gear shaft (20); the end cover nut (55) is connected with the steering gear shell (22) through a thread pair and is used for screwing in the tenth deep groove ball bearing (53) for limiting; two ends of the steering gear shell (22) are respectively connected with a first motor shell (71) and a second motor shell (72) through bolts; the rack (21) is in meshing transmission with the steering gear shaft (20) and is connected with the steering gear shell (22) through a first rack bushing (29), a second rack bushing (37) and a rack support seat (57) so as to play a role in supporting and guiding; two ends of the rack (21) are respectively inserted into inner holes of the first lead screw (27) and the second lead screw (35), and two controllable and closed hydraulic chambers (visible as hydraulic cylinders) are formed between the end surfaces of the rack and the first lead screw (27) and the second lead screw (35) through sealing rings. When the oil in the hydraulic chamber is sealed, the rack (21) and the lead screw are synchronously linked; when oil in the hydraulic chamber can flow in and be discharged at will, the rack (21) and the lead screw realize relative independent movement. Furthermore, a gasket (60) is arranged between the rack (21) and the rack supporting seat (57) to reduce the movement friction between the rack and the rack supporting seat; the adjusting screw plug (58) is in threaded connection with the side wall of the steering gear shell (22) below the rack supporting seat (57), and two ends of the compression spring (59) are respectively installed in a spring installation groove on the top surface of the adjusting screw plug (58) and a spring installation groove on the top surface of the rack supporting seat (57) and used for compressing the rack supporting seat and eliminating the transmission clearance of a gear-rack pair; the lower ends of the adjusting screw plug locking nut (61) and the adjusting screw plug (58) are connected through threads.

As shown in fig. 1, 2 and 5, the steering gear housing (22) is a cast aluminum housing with thick ends and thin middle, the middle is used for accommodating main parts of the rack and pinion steering gear (D), the left end and the right end are respectively and coaxially connected with a first motor housing (71) and a second motor housing (72) through a first bolt (19) and a second bolt (30) to form a left cavity and a right cavity, and the left cavity and the right cavity are used for leaving a moving space for moving and shrinking a first lead screw (27) and a second lead screw (35).

In the electronic control unit II, a core component ECU (73) is respectively connected with signal lines of a road sensing motor (1), a torque rotation angle sensor (4), an electromagnetic clutch (15), a first lead screw position sensor (40), a second lead screw position sensor (41), a first electromagnetic switch valve (42), a second electromagnetic switch valve (43), a first steering executing motor mechanism (B) and a second steering executing motor mechanism (C). The ECU receives a torque corner signal of a steering wheel (38) collected by a torque corner sensor (4), and then judges the steering intention of a driver; the ECU receives signals of a first lead screw position sensor (40) and a second lead screw position sensor (41), obtains an actual rotation angle signal of a steering wheel, corrects an output execution motor operation control signal according to a torque rotation angle signal of a steering wheel directly detected by a torque rotation angle sensor (4), and realizes correction of the actual rotation angle of the steering wheel; the ECU sends a clutch control signal to an electromagnetic clutch (15) to control the separation or combination of the electromagnetic clutch, and further controls the connection or disconnection of a mechanical structure between a steering wheel unit I and a steering execution unit III; the ECU respectively sends corresponding motor operation control signals to the road sensing motor (1), the first steering executing motor mechanism (B) and the second steering executing motor mechanism (C) to control the operation state and torque output of the road sensing motor (1), the first steering executing motor mechanism (B) and the second steering executing motor mechanism (C), and meanwhile, the road sensing motor (1), the first steering executing motor mechanism (B) and the second steering executing motor mechanism (C) also feed back real-time operation state signals including rotating speed and torque to the ECU to realize closed-loop control and regulation of the road sensing motor (1), the first steering executing motor mechanism (B) and the second steering executing motor mechanism (C).

The mode selection and display unit IV consists of three mode selection buttons (75) and a central control screen (74), a driver can send a signal to the ECU through the buttons so as to manually select the current steering mode, and if the driver presses the I button, the driver intends to control the steering system to operate in a mode I; if the driver presses the II button, the fact that the driver intends to control the steering system to operate in the mode II is indicated; if the driver presses the III button, the indication is that the driver intends to control the steering system to operate in mode three; if none of the three buttons are pressed, this means that the driver has not intentionally initiated the human steering mode selection, i.e. the human driving mode selection state is off. The ECU displays the current working mode on the central control screen through CAN communication, and fault information is also displayed on the central control screen through CAN communication.

The electric multi-mode steer-by-wire system can be automatically realized by an electronic control unit II control system according to the vehicle dynamic state and the failure state of a steer-by-wire actuator, or three steering working modes, namely a steer-by-wire independent steering mode, a steer-by-wire trapezoidal steering mode and an electric power steering mode, are artificially realized by three mode selection buttons in a driver operation mode selection and display unit IV and are respectively replaced by a mode I, a mode II and a mode III. The first two of these are steer-by-wire modes, i.e. the steering wheel is completely mechanically decoupled from the steered wheels, where mode one is also known as distributed steer-by-wire and mode two is also known as traditional steer-by-wire; the latter is the traditional electric power-assisted mechanical steering mode, namely the steering wheel is mechanically connected with the steering execution unit and the steering wheel, the mode two and the mode three play a role in failure protection backup, and the mode three also plays a role in failure protection backup for the mode two, so that the system reliability of the steer-by-wire is greatly improved.

The memory in the electronic control unit II of the electric multi-mode steer-by-wire system according to the present invention stores the above three mode switching control methods, and the specific main program logic flow is shown in fig. 6, and the execution steps are as follows:

the method comprises the following steps: and (5) self-checking the system, and recording the failure states of the first motor and the second motor.

Step two: the driver mode selection signal state in the mode selection and display unit IV is read.

Step three: judging whether the driver selects a mode or not; if not, jumping to the step six.

Step four: judging whether the mode selection signal is a mode one; and if so, jumping to the step six.

Step five: judging whether the mode selection signal is a mode two; and if not, jumping to the step seven.

Step six: according to the failure states of the first motor and the second motor which are self-checked by the system and the state of the driver mode selection signal, judging the following conditions:

if the first motor and the second motor are not invalid and the mode selection state of the driver is off or the mode one, jumping to the step eight;

if one motor is not in failure and the mode selection state of the driver is off or the mode II, jumping to the step seven;

if the first motor and the second motor are both invalid and the mode selection state of the driver is off, jumping to the step ten;

if the first motor and the second motor are both invalid and the mode selection state of the driver is the mode two, jumping to the step fourteen;

if the first motor fails and the mode signal selected by the driver is the first mode, jumping to the step twelve;

if the motor II fails and the mode signal selected by the driver at present is the mode I, jumping to the step thirteen;

step seven: judging whether the previous cycle is a mode one, and judging the following conditions:

if so, jumping to the step eleven and then adjusting to the step nine if the mode selection state of the driver is not the mode three;

if not, and the mode selection state of the driver is not the mode three, directly jumping to the step nine;

if yes, and the mode selection state of the driver is a mode three, jumping to the step eleven and then adjusting to the step ten;

if not, and the driver mode selection state is mode three, directly jumping to step ten.

Step eight: enter mode one process subroutine.

Step nine: enter mode two processing subroutine.

Step ten: and entering a mode three-processing subprogram.

Step eleven: the angle compensation centering subroutine is entered.

Step twelve: and sending a prompt instruction that the motor fails to complete the selection of the first mode and please switch the modes or maintain in time to the mode selection and display unit IV.

Step thirteen: and sending a prompt instruction that the motor II fails to complete the selection of the first mode and please switch the modes or maintain in time to the mode selection and display unit IV.

Fourteen steps: and sending a prompt instruction that the first motor and the second motor fail to complete the selection of the second mode and please switch the modes or maintain in time to the mode selection and display unit IV.

Step fifteen: and ending and returning.

The following describes a specific procedure flow by taking an example that the driver selects the mode two, and the last cycle is the mode one, and the motor is not failed.

The procedure starts:

entering the step one;

entering the step two;

entering a third step, wherein the judgment of the third step is yes;

step four is entered, and the judgment of step four is no;

entering the step five, and judging that the step five is yes;

entering the step six, and jumping to the step seven after judging;

entering a seventh step, wherein the seventh step is judged to be yes;

entering the step eleven;

entering the ninth step;

and ending the program and returning.

The processing flows of the mode one processing subprogram, the mode two processing subprogram, the mode three processing subprogram and the angle compensation pair subprogram are specifically as follows:

mode one processing subroutine: as shown in fig. 7, the process begins, step one, switching off the electromagnetic clutch; step two, opening a first electromagnetic switch valve and a second electromagnetic switch valve; step three, the ECU reads a steering wheel angle and a torque signal; step four, the ECU respectively generates two steering wheel steering angle signals according to the steering dynamics requirement of the whole vehicle and the current vehicle state; step five, respectively calculating according to the angular transmission ratio relation of the steering executing motor mechanisms to obtain the corner control instructions of the left steering executing motor and the right steering executing motor; step six, the two signals are respectively transmitted to a left steering executing motor and a right steering executing motor, and the two steering executing motors feed back respective motor state signals to step four; seventhly, completing independent steering of the left steering wheel and the right steering wheel respectively, and feeding back the wheel rotation angle state to the third step respectively; the routine is ended.

Mode two processing subroutine: as shown in fig. 8, the process begins, step one, switching off the electromagnetic clutch; step two, closing the first electromagnetic switch valve and the second electromagnetic switch valve; step three, the ECU reads a steering wheel angle and a torque signal; generating a common steering wheel steering angle signal by the ECU according to the steering dynamics requirement of the whole vehicle and the current vehicle state; step five, calculating according to the angular transmission ratio relation of the steering executing motor mechanism to obtain a corner control command signal of the current effective steering executing motor (the effective steering executing motor refers to the steering executing motor without the failure state); step six, transmitting the signals to effective steering executing motors (if the left and right steering executing motors are not invalid, the driving of the steering executing motor on one side can be determined according to the steering resistance load, or the driving of the effective steering executing motors on the two sides can be controlled according to the same turning angle signal, and the motor feedback motor state signals are transmitted to step four; seventhly, the left steering wheel and the right steering wheel complete steering together according to the steering trapezoidal relation, and the turning angle state of the wheels is fed back to the third step; the routine is ended.

Mode three processing subroutine: as shown in fig. 9, the process begins, step one with the electromagnetic clutch engaged; step two, closing the first electromagnetic switch valve and the second electromagnetic switch valve; step three, the ECU reads a steering wheel angle and a torque signal; looking up a table by the ECU according to the current vehicle speed and the current steering wheel torque signal to generate a steering power-assisted signal (the prior art is not repeated); fifthly, calculating according to the required power-assisted steering signal and the speed ratio of the speed reducing mechanism of the road sensing motor to generate a current control command signal of the road sensing motor; step six, transmitting the command signal to a road sensing motor to generate an assistance torque, and feeding back a motor state signal to step four by the motor; seventhly, under the assistance action of the road sensing motor, a driver operates a steering wheel to drive left and right steering wheels to complete mechanical steering according to the steering trapezoidal relation, and the turning angle state of the wheels is fed back to the third step; the routine is ended.

Angle compensation versus neutron program: as shown in fig. 10, the process starts, step one, the failure side electromagnetic switch valve is closed, and if there is no failure motor, the electromagnetic switch valve at the end with the smaller wheel rotation angle is closed; step two, the ECU reads the corner signals of the wheel at the failure side or the wheel at the side with smaller corner and calculates the corner of the wheel at the other side through the steering trapezoid geometric relationship; step three, calculating a target rotation angle control instruction of the steering execution motor on the non-failure side or the side with larger rotation angle according to the angular transmission ratio relation of the steering execution motor mechanism; opening the electromagnetic switch valve on the non-failure side or the side with larger rotation angle; inputting target corner control instruction information to a steering motor on the non-closed side (the non-closed side is the non-failure side or the side with a larger corner) of the electromagnetic switch valve; step six, judging whether the wheel angle is the same as a target angle control instruction calculated by the ECU, and if the wheel angle is different from the target angle control instruction calculated by the ECU, returning to the step three; if yes, entering a seventh step; seventhly, closing the electromagnetic switch valve on the non-failure side or the side with larger rotation angle; the routine is ended.

The invention relates to an electric multi-mode steer-by-wire system and a mode switching method thereof, and specifically the working principle of the working states of three working modes and the working mode switching thereof is as follows:

firstly, the specific working process of the wire control independent steering mode of each wheel is as follows:

under normal working conditions, a driver rotates a steering wheel to send a steering operation signal, a torque angle sensor detects a torque angle signal of the steering wheel and sends the acquired steering wheel torque angle signal to an ECU (73), the ECU (73) receives the corresponding steering wheel torque angle signal, processes the steering wheel torque angle signal and outputs an execution motor operation control signal, the execution motor control signal is respectively sent to a first steering execution motor mechanism (B) and a second steering execution motor mechanism (C), the first motor rotor (24) and the second motor rotor (32) are controlled to respectively output respective driving torques outwards, the driving torques of the motor rotors are converted into linear motion forces of a screw rod through a sliding screw rod pair, steering wheels at two ends are swung through an automobile steering tie rod and a steering knuckle arm, and at the moment, a first electromagnetic switch valve (42) and a second electromagnetic switch valve (43) are in an open state, so that the hydraulic chambers at the two ends are communicated with the oil tank (44), the linear thrust of the lead screw can enable hydraulic oil to freely circulate between the hydraulic cylinders at the two ends and the oil tank, the first lead screw (27) and the second lead screw (35) can freely and independently move without resistance, and independent steering of each wheel by wire is realized, and the working mode is the working mode when the steering-by-wire system normally works.

At the moment, the ECU (73) receives signals of the first lead screw position sensor (40) and the second lead screw position sensor (41) to obtain an actual steering signal of a steering wheel, and corrects an output execution motor operation control signal according to a torque angle signal of a steering wheel directly detected by the torque angle sensor (4) to realize the correction of the actual steering of the steering wheel; meanwhile, the road sensing motor (1), the first steering executing motor mechanism (B) and the second steering executing motor mechanism (C) feed back real-time running state signals including rotating speed and torque to the ECU (73), so that closed-loop control and adjustment of the road sensing motor (1), the first steering executing motor mechanism (B) and the second steering executing motor mechanism (C) are realized.

As shown in figure 1, when the left wheel and the right wheel implement normal wire control independent steering control, the ECU (73) receives and processes the information of the road surface, outputs the operation control signal of the road sensing motor, sends the operation control signal of the road sensing motor to the road sensing motor (1), controls the road sensing motor (1) to output road sensing simulation torque outwards, controls the road sensing motor (1) to output the road sensing simulation torque to the road sensing motor speed reducing mechanism (A), in the road sensing motor speed reducing mechanism (A), the output end of the control road sensing motor (1) drives the worm (49) to rotate, the worm (49) drives the worm wheel (9) to rotate, further drives the upper transmission shaft (8) to rotate, and drives the torsion bar (6), the steering driving shaft (7) and the steering wheel (38) to rotate in turn, and finally the road simulation signal expressed by the road sensing simulation torque is fed back to the driver through the steering wheel (38), and realizing road feel simulation.

Furthermore, as shown in fig. 1, when the left and right wheels perform normal steer-by-wire independent control, the ECU (73) controls the electromagnetic clutch to be disengaged so that there is no mechanical connection between the steering wheel unit I and the steering actuator unit III;

switching from the normal independent steering mode of each wheel by wire to the trapezoidal steering mode by wire control during failure backup:

when a vehicle is steered, if one steering motor is damaged, the control of the independent steering mode of each wheel by wire is switched to the control of the trapezoidal steering mode by wire control. When the steering angle of the left wheel and the right wheel is in failure, the steering angle needs to be switched to the steering-by-wire trapezoidal steering control, and the steering angle of the left wheel and the right wheel needs to strictly meet the steering angle relation determined by the steering trapezoid, so that the steering angle of the single wheel needs to be adjusted in the switching process, and the switching from independent steering to the steering trapezoid of the front wheel is met. The specific embodiment is as follows: when the steering motor of one wheel fails, the electromagnetic switch valve of the failed end is closed, the electromagnetic switch valve of the normally working end is kept open, the rotation angle of the wheel of the failed end is calculated through the lead screw position sensor of the failed end, the rotation angle of the wheel of the normally working end is calculated through the steering trapezoid by taking the rotation angle as a standard, the rotation angle is adjusted through the normally working steering motor, and the electromagnetic switch valve of the normally working end is closed after the target rotation angle is reached, so that the switching process is completed.

Secondly, the specific working process of the steer-by-wire trapezoidal steering mode is as follows:

when only one of the first steering executing motor mechanism (B) and the second steering executing motor mechanism (C) is a steering executing motor mechanism which normally works, the steering system enters a steering-by-wire trapezoidal steering mode under failure backup. At the moment, a driver rotates a steering wheel to send a steering operation signal, a torque corner sensor detects a torque corner signal of the steering wheel and sends the collected torque corner signal of the steering wheel to an ECU (73), the ECU (73) receives the corresponding torque corner signal of the steering wheel, processes the torque corner signal and outputs an execution motor operation control signal, the execution motor control signal is respectively sent to an effective steering execution motor mechanism to control an effective motor rotor to output driving torque outwards, the driving torque of the motor rotor is converted into force of linear motion of a lead screw through a sliding lead screw pair, steering wheels at two ends are swung through an automobile steering tie rod and a steering knuckle arm, at the moment, a first electromagnetic switch valve (42) and a second electromagnetic switch valve (43) are in a closed state, namely a first lead screw (27) and a second lead screw (35) are fixedly connected with a rack (21) due to incompressibility of hydraulic oil, the effective steering actuating motor mechanism can transmit force to the failure steering actuating motor mechanism through the action of the rack (21), so that the steering wheels at two ends swing, and the failure backup steering process is realized.

Particularly, under the condition that the normal steering working condition is switched to the failure backup steering working condition, because the control strategy of independent steering of each wheel by wire is executed under the normal steering working condition, the control strategy of trapezoidal steering by wire under the failure backup steering working condition follows the traditional steering trapezoidal geometric steering rule, and the rotating angles of the outer wheels are usually different under the condition that the inner wheels have the same rotating angle under the control of two steering modes, the electromagnetic switch valve on the side with the failure needs to be closed firstly when the two working conditions are switched, and the rotating angle of the steering wheel on the side with the normal working is adjusted through the geometric relation of the steering trapezoids according to the rotating angle of the wheel on the side with the failure, so that the trapezoidal steering strategy by wire under the failure is met.

In the steer-by-wire trapezoidal steering mode, the ECU (73) controls the electromagnetic clutch to be separated, so that no mechanical connection exists between the steering wheel unit I and the steering execution unit III;

the left and right wheel linear control steering trapezoidal mode during failure backup is switched to the traditional electric power steering mode under complete failure:

because the trapezoidal steering relation of left and right wheel steering is all satisfied to drive-by-wire trapezoidal steering mode and traditional electric power steering, only need to engage electromagnetic clutch this moment to use as the power-assisted steering motor with the way feel motor.

Thirdly, the specific working process of the electric power steering mode is as follows:

when the first steering executing motor mechanism (B) and the second steering executing motor mechanism (C) can not work, the steering system enters a traditional electric power-assisted steering mode, and the mode is a common steering mode of the traditional automobile. At the moment, an ECU (73) controls to combine an electromagnetic clutch (15), a steering wheel steering rod system formed by sequentially connecting a steering wheel (38), a steering driving shaft (7), a torsion rod (6) and an upper transmission shaft (8) is mechanically connected with a steering gear (D) and a steering gear shaft (20) through the electromagnetic clutch (15) between a steering wheel unit I and a steering execution unit III, a driver operates the steering wheel (38) to jointly output driving torque through the steering wheel steering rod system under the rotation assistance of a road sensing motor speed reducing mechanism (A), and then a steering execution unit III including the steering gear drives left and right wheels to rotate according to the steering trapezoid geometrical relationship under the action of a steering trapezoid formed by the steering gear, a steering cross rod and a steering knuckle arm. At the moment, the first electromagnetic switch valve (42) and the second electromagnetic switch valve (43) are in a closed state, namely the first lead screw (27) and the second lead screw (35) are fixedly connected with the rack (21) due to incompressibility of hydraulic oil, and steering driving torque of the steering wheel is converted into force for pushing the steering wheel to rotate through the gear-rack transmission pair, so that the steering trapezoidal steering process of a driver with left and right wheels is realized.

Particularly, when the two motors fail simultaneously, the two electromagnetic switch valves and the electromagnetic clutch are closed simultaneously and the road sensing motor is used as a power-assisted motor. Because the working condition is a dangerous working condition and needs to be maintained immediately when the working condition appears, the design can ensure that the vehicle is still in a controllable state.