1. A creep control method, characterized by comprising:

s1, acquiring the current running information of the vehicle in real time;

s2, judging whether the vehicle enters a crawling mode or not according to the current running information of the vehicle, and if so, jumping to S3;

s3, controlling the output torque of the motor to change from the current torque to a target torque so as to change the vehicle speed from the current vehicle speed to a target crawling vehicle speed, wherein the target crawling vehicle speed can be set;

controlling the output torque of the motor to change from the current torque to the target torque comprises the following steps:

feedforward control, calculating a feedforward torque according to the current vehicle speed and the road gradient;

feedback control, calculating a feedback torque according to a current vehicle speed difference, wherein the current vehicle speed difference is a difference value between the target crawling vehicle speed and the current vehicle speed, the feedback control includes proportional control and integral control, the feedback torque includes a proportional feedback torque calculated by the proportional control and an integral feedback torque calculated by the integral control, the proportional control is activated when the vehicle enters the crawling mode, the integral control is activated under a preset condition, and the preset condition includes:

the current master cylinder pressure is less than Ps and the current vehicle speed difference is less than Δ Vs, where Ps and Δ Vs are calibratable.

2. The creep control method according to claim 1,

the formula for calculating the proportional feedback torque is as follows: u1(k) ═ kp · e (k), where u1(k) is the proportional feedback torque at time k, kp is the proportionality coefficient, e (k) is the current vehicle speed difference Δ V at time k;

when the delta V is more than or equal to-delta V1 and less than or equal to delta V1, the value of kp is kp1, the value of delta V1 is more than 0, and the value of kp1 is more than 0;

when the delta V1< delta V2 or-delta V2< delta V < -delta V1, the value of kp is kp2, kp2 is positively correlated with the absolute value of delta V, and kp2 is greater than kp 1;

wherein, the delta V1, the delta V2, the kp1 and the kp2 can be calibrated;

the integral feedback torque is calculated by the formula:where u2(k) is the integrated feedback torque at time k, ki is the integration coefficient,the sum of the current vehicle speed difference delta V from the ith moment to the kth moment;

when delta V is more than or equal to-delta V3 and less than or equal to delta V3, the values of ki are ki1, delta V3>0 and ki1> 0;

when delta V3 is not more than delta V < delta V4 or-delta V4< delta V < -delta V3, the value of ki is ki2, ki2 is in positive correlation with the absolute value of delta V, and ki2 is greater than ki 1;

wherein, the delta V3, the delta V4, the ki1 and the ki2 can be calibrated.

3. The creep control method according to claim 1, wherein in step S2, the creep mode includes a first creep mode and a second creep mode;

judging whether the vehicle enters a crawling mode according to the current running information of the vehicle, wherein the judging step comprises the following steps:

judging whether the vehicle slips or not when the vehicle is judged to enter a crawling mode according to the current running information of the vehicle;

if the vehicle does not skid, the vehicle enters the first crawling mode;

if the vehicle slips, the vehicle enters the second crawling mode;

in the step S3, in the step S,

the target crawling speed comprises a first target crawling speed and a second target crawling speed, the first target crawling speed corresponds to the first crawling mode, the second target crawling speed corresponds to the second crawling mode, and the second target crawling speed is smaller than the first target crawling speed;

the target torque includes a first target torque corresponding to the first target creep vehicle speed and a second target torque corresponding to the second target creep vehicle speed.

4. The creep control method according to any one of claims 1 to 3, wherein the step S3 further includes: judging whether the vehicle exits the crawling mode or not according to the current running information of the vehicle, if so, controlling the output torque of the motor to change from the current torque to a request torque so as to change the current vehicle speed of the vehicle to a request vehicle speed, and responding to the current driving requirement by the request vehicle speed;

and in the preset time after the self-triggering quitting of the crawling mode, the variation of the output torque of the motor is delta T, the delta Tmin is not less than the delta T and not more than the delta Tmax, and the delta Tmin and the delta Tmax can be calibrated.

5. A creep control apparatus, comprising:

the acquisition module is used for acquiring the current running information of the vehicle in real time;

the first judgment module is used for judging whether the vehicle enters a crawling mode or not according to the current running information of the vehicle;

the first torque control module is used for controlling the output torque of the motor to change from the current torque to a target torque when the vehicle enters the crawling mode so as to change the vehicle speed from the current vehicle speed to a target crawling vehicle speed, and the target crawling vehicle speed can be set;

the first torque control module includes:

the feedforward control module is used for calculating feedforward torque according to the current vehicle speed and the road gradient;

the feedback control module is used for calculating feedback torque according to the current vehicle speed difference, the current vehicle speed difference is a difference value between the target crawling vehicle speed and the current vehicle speed, the feedback control module comprises a proportional control module and an integral control module, the feedback torque comprises proportional feedback torque obtained by calculation of the proportional control module and integral feedback torque obtained by calculation of the integral control module, the proportional control module is activated when a vehicle enters the crawling mode, the integral control module is activated under a preset condition, and the preset condition comprises:

the pressure of the current brake master cylinder is smaller than Ps, and the current vehicle speed difference is smaller than Vs, wherein Ps and Vs can be calibrated.

6. The creep control apparatus according to claim 5, wherein the proportional feedback torque is calculated by the formula: u1(k) ═ kp · e (k), where u1(k) is the proportional feedback torque at time k, kp is the proportionality coefficient, e (k) is the current vehicle speed difference Δ V at time k;

when the delta V is more than or equal to-delta V1 and less than or equal to delta V1, the value of kp is kp1, the value of delta V1 is more than 0, and the value of kp1 is more than 0;

when the delta V1< delta V2 or-delta V2< delta V < -delta V1, the value of kp is kp2, kp2 is positively correlated with the absolute value of delta V, and kp2 is greater than kp 1;

wherein, the delta V1, the delta V2, the kp1 and the kp2 can be calibrated;

the integral feedback torque is calculated by the formula:where u2(k) is the integrated feedback torque at time k, ki is the integration coefficient,the sum of the current vehicle speed difference delta V from the ith moment to the kth moment;

when delta V is more than or equal to-delta V3 and less than or equal to delta V3, the values of ki are ki1, delta V3>0 and ki1> 0;

when delta V3 is not more than delta V < delta V4 or-delta V4< delta V < -delta V3, the value of ki is ki2, ki2 is in positive correlation with the absolute value of delta V, and ki2 is greater than ki 1;

wherein, the delta V3, the delta V4, the ki1 and the ki2 can be calibrated.

7. The creep control apparatus according to claim 5, wherein the creep mode includes a first creep mode and a second creep mode;

the first judging module comprises:

the first judgment module is used for judging whether the vehicle enters a crawling mode or not according to the current running information of the vehicle;

the second first judgment module is used for judging whether the vehicle slips or not according to the current running information of the vehicle;

if the vehicle enters the crawling mode and does not slip, the vehicle enters the first crawling mode;

if the vehicle enters the crawling mode and the vehicle slips, the vehicle enters the second crawling mode;

the target crawling speed comprises a first target crawling speed and a second target crawling speed, the first target crawling speed corresponds to the first crawling mode, the second target crawling speed corresponds to the second crawling mode, and the second target crawling speed is smaller than the first target crawling speed;

the target torque includes a first target torque corresponding to the first target creep vehicle speed and a second target torque corresponding to the second target creep vehicle speed.

8. The creep control apparatus according to any one of claims 5 to 7, further comprising:

the second judgment module is used for judging whether the vehicle exits the crawling mode or not according to the current running information of the vehicle;

the second torque control module is used for controlling the output torque of the motor to be changed from the current torque to the requested torque when the vehicle exits the crawling mode, so that the current vehicle speed of the vehicle is changed to the requested vehicle speed, and the requested vehicle speed responds to the current driving requirement;

and in the preset time after the self-triggering quitting of the crawling mode, the variation of the output torque of the motor is delta T, the delta Tmin is not less than the delta T and not more than the delta Tmax, and the delta Tmin and the delta Tmax can be calibrated.

9. A vehicle, characterized in that the vehicle comprises:

one or more processors;

storage means for storing one or more programs;

when executed by the one or more processors, cause the one or more processors to implement the crawling control method of any of claims 1-4.

10. A computer-readable storage medium on which a computer program is stored, the program, when being executed by a processor, implementing the crawling control method according to any one of claims 1 to 4.

Background

During the driving of the vehicle, particularly in urban areas, it is sometimes necessary to enter a creep mode. When entering into the creep mode, the output torque of the motor is switched, and the switching of the torque can directly influence the driving feeling of a driver. Compare in traditional fuel vehicle, pure electric vehicles's motor's speed governing scope is wide, generally adopts single reduction gear, and transmission system has gear clearance, consequently, changes when pure electric vehicles get into the mode of crawling and produces the impact. Therefore, when the vehicle enters the crawling mode, the output torque of the motor needs to be adjusted, so that driving stability is guaranteed, and visual feeling of a driver is improved.

Disclosure of Invention

The invention aims to provide a crawling control method, a crawling control device, a vehicle and a storage medium, which can ensure driving stability and improve visual feeling of a driver when the vehicle enters a crawling mode.

In a first aspect, a creep control method is provided, including:

s1, acquiring the current running information of the vehicle in real time;

s2, judging whether the vehicle enters a crawling mode or not according to the current running information of the vehicle, and if so, jumping to S3;

s3, controlling the output torque of the motor to change from the current torque to a target torque so as to change the vehicle speed from the current vehicle speed to a target crawling vehicle speed, wherein the target crawling vehicle speed can be set;

controlling the output torque of the motor to change from the current torque to the target torque comprises the following steps:

feedforward control, calculating a feedforward torque according to the current vehicle speed and the road gradient;

feedback control, calculating a feedback torque according to a current vehicle speed difference, wherein the current vehicle speed difference is a difference value between the target crawling vehicle speed and the current vehicle speed, the feedback control includes proportional control and integral control, the feedback torque includes a proportional feedback torque calculated by the proportional control and an integral feedback torque calculated by the integral control, the proportional control is activated when the vehicle enters the crawling mode, the integral control is activated under a preset condition, and the preset condition includes:

the current master cylinder pressure is less than Ps and the current vehicle speed difference is less than Δ Vs, where Ps and Δ Vs are calibratable.

In a second aspect, there is provided a creep control apparatus comprising:

the acquisition module is used for acquiring the current running information of the vehicle in real time;

the first judgment module is used for judging whether the vehicle enters a crawling mode or not according to the current running information of the vehicle;

the first torque control module is used for controlling the output torque of the motor to change from the current torque to a target torque when the vehicle enters the crawling mode so as to change the vehicle speed from the current vehicle speed to a target crawling vehicle speed, and the target crawling vehicle speed can be set;

the first torque control module includes:

the feedforward control module is used for calculating feedforward torque according to the current vehicle speed and the road gradient;

the feedback control module is used for calculating feedback torque according to the current vehicle speed difference, the current vehicle speed difference is a difference value between the target crawling vehicle speed and the current vehicle speed, the feedback control module comprises a proportional control module and an integral control module, the feedback torque comprises proportional feedback torque obtained by calculation of the proportional control module and integral feedback torque obtained by calculation of the integral control module, the proportional control module is activated when a vehicle enters the crawling mode, the integral control module is activated under a preset condition, and the preset condition comprises:

the pressure of the current brake master cylinder is smaller than Ps, and the current vehicle speed difference is smaller than Vs, wherein Ps and Vs can be calibrated.

In a third aspect, a vehicle is provided, the vehicle comprising:

one or more processors;

storage means for storing one or more programs;

when the one or more programs are executed by the one or more processors, the one or more processors are caused to implement the crawling control method as described above.

In a fourth aspect, there is provided a computer-readable storage medium having stored thereon a computer program which, when executed by a processor, implements the creep control method as described above.

Compared with the prior art, in the embodiment of the invention, when the vehicle enters the crawling mode, the feedforward control and the feedback control are adopted to adjust the output torque of the motor. The feedforward control mainly considers the influence of the current vehicle speed and the road gradient on the vehicle running state. The feedback control mainly considers the influence of the current vehicle speed difference on the vehicle running state. The feedback control adopts PI control, namely proportional control and integral control are included. And the proportional control realizes the quick adjustment of the speed of the vehicle from the current speed of the vehicle to the target crawling speed of the vehicle. The proportional control is activated when the vehicle is in the creep mode. However, the simple proportional control has an adjustment error, so that the steady-state vehicle speed cannot accurately reach the target crawling vehicle speed, and the integral control and the proportional control are combined, so that the vehicle speed adjustment error can be effectively reduced, and the control accuracy is improved. However, the integral control is prone to overshoot, which causes problems with bouncing or vehicle jerking. Therefore, in the embodiment of the invention, the current vehicle speed difference and the pressure of the brake master cylinder are used as the preset conditions for activating the integral control, namely the integral control is activated at the later stage of the crawling control, so that the torque adjusting precision can be ensured, the problems of vehicle bouncing and vehicle cocking can be solved, the impact generated by a transmission system in the speed changing process is reduced, the vehicle is stably transited from the current state to the crawling mode, the driving stability is improved, and the subjective feeling of a driver is improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the contents of the embodiments of the present invention and the drawings without creative efforts.

Fig. 1 is a flowchart of a crawling control method according to an embodiment of the present invention;

fig. 2 is a relationship diagram of the scaling factor kp and the current vehicle speed difference Δ V according to the first embodiment of the present invention;

fig. 3 is a diagram of a relationship between an integral coefficient ki and a current vehicle speed difference Δ V according to a first embodiment of the present invention;

FIG. 4 is a flowchart of a crawling control method according to a second embodiment of the present invention;

fig. 5 is a schematic diagram of a crawling control device according to a third embodiment of the present invention;

fig. 6 is a schematic view of a vehicle according to a fifth embodiment of the present invention.

Detailed Description

Example one

Fig. 1 is a flowchart of a creep control method according to an embodiment of the present invention, which is applicable to determining whether a vehicle enters a creep mode, and controlling torque output of a motor when the vehicle enters the creep mode, so that the vehicle smoothly and accurately changes from a current vehicle speed to a target creep vehicle speed, thereby reducing impact generated by a vehicle transmission system during speed regulation, avoiding a vehicle speed overshoot phenomenon, improving driving stability, and improving subjective driving experience of a user. The creep control method may be executed by a creep control device, which may be implemented in software and/or hardware, and may be configured in a vehicle, particularly in an electric vehicle.

As shown in fig. 1, the creep control method of the present embodiment includes:

and S1, acquiring the current running information of the vehicle in real time.

The current running information of the vehicle includes a current vehicle speed, an opening degree of an accelerator pedal, a pressure of a master cylinder, a gear, an EPB signal, a vehicle malfunction signal, a wheel speed of a driving wheel, a wheel speed of a non-driving wheel (if any), a longitudinal acceleration of a vehicle body, and the like.

The vehicle comprises a vehicle control unit, a driving motor, a motor control unit arranged in the driving motor, a wheel speed sensor, an accelerator pedal position sensor, a gear sensing module, an electronic parking sensing module, a brake master cylinder pressure sensor, a vehicle body longitudinal acceleration sensing module and the like.

The wheel speed sensor is used for measuring the current rotating speed of the output shaft of the motor so as to determine the current vehicle speed. The accelerator pedal position sensor is used for detecting the position of an accelerator pedal so as to obtain the opening degree of the accelerator pedal. The gear sensing module is used for detecting a gear signal to determine a current gear, such as a P gear, an N gear or a D gear. The electronic parking sensing module is used for detecting the current EPB signal so as to judge that the EPB system is in an unlocking or locking state. The brake master cylinder pressure sensor is used for measuring the pressure of the brake master cylinder. The vehicle body longitudinal acceleration sensing module is used for measuring the longitudinal acceleration of a vehicle body. The wheel speed sensor, the accelerator pedal position sensor, the gear sensing module, the electronic parking sensing module, the brake master cylinder pressure sensor and the vehicle body longitudinal acceleration sensing module are respectively and electrically connected with the input end of the whole vehicle controller. And the output end of the vehicle control unit is electrically connected with the input end of the motor control unit. The output end of the motor control unit is electrically connected with the driving motor.

Optionally, the signal transmission between the vehicle Controller and each sensor, the sensing module, or the motor control unit may be performed through a Controller Area Network (CAN) bus, a Local Interconnect Network (LIN) bus, a hard line, or the like in the vehicle. Illustratively, an accelerator pedal position sensor hardwires a detected position signal of an accelerator pedal to the vehicle control unit. The gear sensing module, the electronic parking sensing module, the brake master cylinder pressure sensor and the vehicle body longitudinal acceleration sensing module respectively send respective measured information to the vehicle control unit through the CAN bus.

And S2, judging whether the vehicle enters a crawling mode or not according to the current running information of the vehicle, and if so, jumping to S3.

When the current running information of the vehicle meets all the following conditions, the vehicle enters a crawling mode:

the current vehicle speed V is less than Vs1, and Vs1 can be calibrated; illustratively, Vs1 may be set empirically, such as 8km/h-12 km/h;

the opening degree of an accelerator pedal is less than a%, and a can be calibrated; illustratively, a has a value of 1 to 5, preferably a has a value of 2;

the gear is D gear or R gear;

the pressure of the brake master cylinder is less than bbar, and b can be set; illustratively, b is 0.2;

unlocking the EPB;

the vehicle has no driving prohibition obstacle.

When the above conditions are all satisfied, the creep mode is activated.

S3, controlling the output torque of the motor to change from the current torque to a target torque so that the vehicle speed changes from the current vehicle speed to a target creep vehicle speed, wherein the target creep vehicle speed can be set;

controlling the output torque of the motor to change from the current torque to the target torque comprises the following steps:

feedforward control, calculating a feedforward torque according to the current vehicle speed and the road gradient;

feedback control, calculate feedback torque according to current vehicle speed difference, current vehicle speed difference is the difference of target crawl speed of a motor vehicle and current speed of a motor vehicle, and feedback control includes proportional control and integral control, and proportional control activates when the vehicle gets into the mode of crawling, and integral control activates under the preset condition, and the preset condition includes:

the current master cylinder pressure is less than P and the current vehicle speed difference is less than Δ Vs, where P and Δ Vs are calibratable.

The target crawling speed can be calibrated according to the road condition and by combining with design experience. The target torque corresponds to the target creep vehicle speed, i.e., the target torque is determined according to the target creep vehicle speed. Illustratively, the value range of the target creep vehicle speed Vc is 3 Km/h-8 Km/h.

Specifically, the control of the output torque of the motor to change from the current torque to the target torque includes feedforward control and feedback control.

The feedforward control mainly considers the influence of the current vehicle speed and the road gradient on the vehicle running state. The feedforward torque is calculated by the feedforward control. The feedforward torque calculated according to the feedforward control includes a vehicle speed feedforward torque and a gradient feedforward torque. The vehicle speed feedforward torque can be obtained by looking up a table according to the current vehicle speed, the table is stored in the whole vehicle controller in advance, and the table can be obtained by calibration according to design experience. The gradient feedforward torque can be obtained by looking up a table according to the gradient of the road surface, the table is also stored in the whole vehicle controller in advance, and the table can be obtained by calibration according to design experience. The calculation formula of the road surface gradient is as follows:

where θ is the road surface gradient, a_senThe longitudinal acceleration of the vehicle body is measured by a vehicle body longitudinal acceleration sensing module;is the actual longitudinal acceleration of the vehicle body, and V is the current vehicle speed.

It will be appreciated that when the vehicle is travelling on a level road, the road slope is 0 ° and the slope feedforward torque is also zero.

Optionally, in order to reduce the influence caused by the noise and the vehicle speed shake of the vehicle body longitudinal acceleration sensing module, the longitudinal acceleration a of the vehicle body is subjected to_senLow-pass filtering is carried out, and the longitudinal acceleration a of the vehicle body is measured_senActual longitudinal acceleration with respect to the vehicle bodyThe difference value of (a) is low-pass filtered to ensure the accuracy of the slope calculation.

The feedback control mainly considers the influence of the current vehicle speed difference on the vehicle running state. The feedback control adopts PI control, namely proportional control and integral control are included. Correspondingly, the feedback torque includes a proportional feedback torque calculated by the proportional control and an integral feedback torque calculated by the integral control.

And the proportional control realizes the quick adjustment of the speed of the vehicle from the current speed of the vehicle to the target crawling speed of the vehicle. The proportional control is activated when the vehicle is in the creep mode. However, the simple proportional control has an adjustment error, so that the steady-state vehicle speed cannot accurately reach the target crawling vehicle speed, and the integral control and the proportional control are combined, so that the vehicle speed adjustment error can be effectively reduced, and the control accuracy is improved. However, the integral control is liable to cause an overshoot phenomenon. For example, when the vehicle enters a creep mode from a starting stage, if integral control is activated at an initial stage of the creep control, torque calculated by the integral control is too large, so that the vehicle speed is overshot, and a vehicle leaping phenomenon is easy to occur when the vehicle speed is close to a target creep vehicle speed; in addition, since the force of the driver depressing the brake pedal is still large at the initial stage of the creep control, that is, the pressure of the master cylinder is still large, and if the integral control is activated at this time, the torque calculated by the integral control is too large after the brake pedal is completely released, and a sudden change in torque occurs, and the vehicle runs up. It is understood that the problem of bouncing or vehicle cocking described above may also occur if the integral control is activated at the early stage of the creep control for the case where the vehicle changes from the high speed to the creep mode. Therefore, in the embodiment, the integral control is activated at the later stage of the crawling control, so that the torque adjusting precision can be ensured, the problems of vehicle leaping and vehicle rising can be solved, the impact generated by the transmission system in the speed changing process is reduced, the vehicle is enabled to be stably transited to the crawling mode from the current state, the driving stability is improved, and the subjective feeling of a driver is improved.

Specifically, in the present embodiment, the preset conditions for activating the integral control according to the current vehicle speed difference Δ V and the pressure of the brake master cylinder include: the current master cylinder pressure is less than Ps and the current vehicle speed difference is less than Δ Vs, where Ps and Δ Vs are calibratable. When the current driving information of the vehicle satisfies the preset condition, indicating that the initial adjustment phase of the creep control is finished, the integral mode may be activated.

The formula for calculating the proportional feedback torque is as follows: u1(k) ═ kp · e (k), where u1(k) is the proportional feedback torque at time k, kp is the proportionality coefficient, and e (k) is the current vehicle speed difference Δ V at time k.

As shown in fig. 2, the value of kp is related to the current vehicle speed difference Δ V.

When the delta V is more than or equal to-delta V1 and less than or equal to delta V1, the value of kp is kp1, the value of delta V1 is more than 0, and the value of kp1 is more than 0;

when the delta V1< delta V2 or-delta V2< delta V < -delta V1, the value of kp is kp2, kp2 is positively correlated with the absolute value of delta V, and kp2 is greater than kp 1;

wherein, the delta V1, the delta V2, the kp1 and the kp2 can be obtained by calibration according to experience.

It can be understood that, in the initial stage of the activation of the creep mode, that is, in the initial stage of the torque adjustment, only the proportional control is activated, the current vehicle speed difference Δ V is large, in order to ensure the adjustment speed, the value of kp is kp2, and kp2 is positively correlated with the absolute value of the current vehicle speed difference Δ V, so that a large proportional feedback torque is obtained, and the vehicle speed is enabled to be rapidly close to the target creep vehicle speed from the current vehicle speed. Along with the continuous approaching of the output torque of the motor to the target creep torque, the current vehicle speed difference delta V is continuously reduced, and the value of kp is smaller kp1 in order to ensure the adjustment precision.

The integral feedback torque is calculated by the formula:where u2(k) is the integrated feedback torque at time k, ki is the integration coefficient,is the sum of the current vehicle speed differences deltav from the i-th time to the k-th time.

As shown in fig. 3, the value of ki is related to the current vehicle speed difference Δ V.

When delta V is more than or equal to-delta V3 and less than or equal to delta V3, the values of ki are ki1, delta V3>0 and ki1> 0;

when delta V3< delta V4 or-delta V4< delta V < -delta V3, the value of ki is ki2, ki2 is positively correlated with the absolute value of delta V, and ki2> ki 1;

wherein, the delta V3, the delta V4, the ki1 and the ki2 can be calibrated.

The integral control is activated when the current vehicle speed difference Δ V is small. And at the initial stage of the integral control activation, ki2 with the larger value of ki value, ki2 is positively correlated with the absolute value of the current vehicle speed difference delta V, and the value of ki2 is continuously reduced along with the continuous reduction of the absolute value of the current vehicle speed difference delta V. As the current vehicle speed gets closer to the target creep vehicle speed, ki takes the value of ki1, which is a smaller value, to avoid overshoot.

Alternatively, the target torque is limited by a maximum torque and a minimum torque, i.e., the target torque should be no less than the minimum torque and the target torque is no greater than the maximum torque to ensure that the vehicle is in creep mode. The maximum torque and the minimum torque may be empirically calibrated. And when the calculated target torque is larger than the maximum torque, controlling the output torque of the motor to be the maximum torque. And controlling the output torque of the motor to be the minimum torque when the calculated target torque is less than the minimum torque.

According to the technical scheme of the embodiment, when the vehicle enters the crawling mode, the output torque of the motor is adjusted by adopting feedforward control and feedback control. The feedforward control mainly considers the influence of the current vehicle speed and the road gradient on the vehicle running state. The feedback control mainly considers the influence of the current vehicle speed difference on the vehicle running state. The feedback control adopts PI control, namely proportional control and integral control are included. And the proportional control realizes the quick adjustment of the speed of the vehicle from the current speed of the vehicle to the target crawling speed of the vehicle. The proportional control is activated when the vehicle is in the creep mode. However, the simple proportional control has an adjustment error, so that the steady-state vehicle speed cannot accurately reach the target crawling vehicle speed, and the integral control and the proportional control are combined, so that the vehicle speed adjustment error can be effectively reduced, and the control accuracy is improved. However, the integral control is prone to overshoot, which causes problems with bouncing or vehicle jerking. Therefore, in the embodiment, the integral control is activated at the later stage of the crawling control, so that the torque adjusting precision can be ensured, the problems of vehicle leaping and vehicle rising can be solved, the impact generated by the transmission system in the speed changing process is reduced, the vehicle is enabled to be stably transited to the crawling mode from the current state, the driving stability is improved, and the subjective feeling of a driver is improved.

Example two

Fig. 4 is a flowchart of the creep control method in the present embodiment. On the basis of the above embodiments, the present embodiment further optimizes the creep control method.

As shown in fig. 4, the creep mode includes a first creep mode and a second creep mode. Specifically, the step of judging whether the vehicle enters the crawling mode or not according to the current running information of the vehicle comprises the following steps:

judging whether the vehicle slips or not when the vehicle enters a crawling mode according to the current running information of the vehicle;

if the vehicle does not slip, the vehicle enters a first crawling mode;

if the vehicle slips, the vehicle enters a second creep mode.

Correspondingly, the target crawling speed comprises a first target crawling speed and a second target crawling speed, the first target crawling speed corresponds to the first crawling mode, the second target crawling speed corresponds to the second crawling mode, and the second target crawling speed is smaller than the first target crawling speed; the target torques include a first target torque corresponding to the first target creep vehicle speed and a second target torque corresponding to the second target creep vehicle speed.

When the vehicle enters a first crawling mode, the output torque of the motor is controlled to be changed from the current torque to a first target torque, so that the vehicle speed is changed from the current vehicle speed to a first target crawling vehicle speed;

controlling the output torque of the motor to change from the current torque to a first target torque includes:

feedforward control, calculating a feedforward torque according to the current vehicle speed and the road gradient;

and feedback control, namely calculating feedback torque according to the current vehicle speed difference, wherein the current vehicle speed difference is the difference value between the target crawling vehicle speed and the current vehicle speed, the feedback control comprises proportional control and integral control, and the feedback torque comprises proportional feedback torque calculated by the proportional control and integral feedback torque calculated by the integral control.

When the vehicle enters a second crawling mode, the output torque of the motor is controlled to be changed from the current torque to a second target torque, so that the vehicle speed is changed from the current vehicle speed to a second target crawling vehicle speed;

controlling the output torque of the motor to change from the current torque to a second target torque, comprising:

feedforward control, calculating a feedforward torque according to the current vehicle speed and the road gradient;

and feedback control, namely calculating feedback torque according to the current vehicle speed difference, wherein the current vehicle speed difference is the difference value between the target crawling vehicle speed and the current vehicle speed, the feedback control comprises proportional control and integral control, and the feedback torque comprises proportional feedback torque calculated by the proportional control and integral feedback torque calculated by the integral control.

Considering the driving condition in rainy and snowy weather, the road surface adhesion coefficient is reduced, and the vehicle is easy to skid. And setting the second target crawling speed to be smaller than the first target crawling speed, and controlling the steady state speed to be the second target crawling speed when the vehicle slips, so that the vehicle is separated from slipping, and the driving safety is improved. Illustratively, the value range of the first target creep vehicle speed Vc1 is 6 Km/h-8 Km/h; the value range of the second target crawling vehicle speed Vc2 is 3 Km/h-5 Km/h.

The method for determining whether the vehicle skids comprises the following steps:

if the vehicle is a two-wheel drive vehicle, the measured rotating speed n of the driving wheel can be respectively obtained_{Drive the}And measured speed n of non-driven wheel_Non-driven. If the vehicle slips, the measured rotational speed n of the drive wheel_{Drive the}And measured speed n of non-driven wheel_Non-drivenNot equal. If the vehicle does not slip, the measured speed n of the drive wheel_{Drive the}And measured speed n of non-driven wheel_Non-drivenEqual or less difference.

Where s is the slip ratio of the driving wheel and n_Non-drivenFor measuring the rotational speed of the non-driven wheel, n_{Drive the}Is the measured rotational speed of the drive wheel. When s is>s1, wheel slip is indicated. s1 can be calibrated.

If the vehicle is a four-wheel drive vehicle, the vehicle can be judged through the wheel acceleration alphaWhether the wheel is slipping. In particular, if α>α₁Then wheel slip, α₁And (4) calibration can be carried out. If the wheel acceleration α remains stable, it can be further determined by the following equation:

where s is a slip ratio of the driving wheel, V' is a product of a wheel angular velocity w of the front wheel or the rear wheel and a rolling radius of the wheel, and V is a current vehicle speed, i.e., an actual speed of the vehicle. When s > s2, wheel slip is indicated. S2 may be calibrated.

Optionally, the creep control method of the present embodiment further includes: and judging whether the vehicle exits the crawling mode or not according to the current running information of the vehicle, if so, controlling the output torque of the motor to change from the current torque to the request torque so as to change the current vehicle speed of the vehicle to the request vehicle speed, and responding to the current driving requirement by the request vehicle speed.

The output torque variation of the motor is delta T within a preset time after the creep mode is exited by triggering, the delta Tmin is not more than the delta T is not more than the delta Tmax, and the delta Tmin and the delta Tmax can be calibrated.

For various reasons, the vehicle may exit the creep mode at any time after entering the creep mode, so the current driving information of the vehicle should be acquired in real time, and whether the vehicle is going to exit the creep mode or not should be judged in real time.

When the current running information of the vehicle meets one of the following conditions, the vehicle exits the crawling mode:

the current vehicle speed V is greater than Vs2, and Vs2 can be calibrated;

the opening degree of an accelerator pedal is not less than a%, and a can be calibrated; illustratively, a has a value of 1 to 5, preferably a has a value of 2;

the gear is changed into P gear or N gear;

the vehicle has a travel-prohibited obstacle.

When one of the above conditions is met, the vehicle exits the creep mode and the vehicle responds to the current driving demand.

The output torque of the motor is controlled to change from the current torque to a requested torque so that the vehicle changes from a current vehicle speed to a requested vehicle speed, the requested vehicle speed being responsive to the current driving demand. The requested torque corresponds to a requested vehicle speed. In order to avoid impact caused by too fast change of the output torque of the motor when the creep mode is exited and influence the subjective driving feeling of a driver, the change rate of the output motor of the motor is controlled, specifically, the output torque of the motor is changed by delta T within a preset time after the creep mode is exited by triggering, the delta Tmin is less than or equal to the delta Tmax, and the delta Tmin and the delta Tmax can be calibrated according to design experience.

The technical scheme of this embodiment, when the vehicle got into the mode of crawling, further whether skid according to the vehicle to the mode of crawling is first mode of crawling and the mode of crawling of second respectively, and to the mode of crawling of second when the vehicle skidded, its corresponding target crawls the speed of a motor vehicle and is lower, makes the vehicle break away from and skids, improves driving safety. In addition, after the vehicle enters the crawling mode, whether the vehicle is to exit the crawling mode is judged in real time, the change rate of an output motor of the motor is controlled when the vehicle exits the crawling mode, and impact is generated due to the fact that the output torque of the motor changes too fast when the vehicle exits the crawling mode, so that subjective driving feeling of a driver is affected.

EXAMPLE III

The embodiment provides a crawling control device, which can execute the crawling control method provided by any embodiment of the invention, and has corresponding functional modules and beneficial effects of the execution method.

As shown in fig. 5, the creep control apparatus includes:

and the acquisition module is used for acquiring the current running information of the vehicle in real time. The acquisition module may include the sensors and sensing modules mentioned in the first embodiment, such as a wheel speed sensor, an accelerator pedal position sensor, a gear position sensing module, an electronic parking sensing module, a master cylinder pressure sensor, a vehicle body longitudinal acceleration sensing module, and the like.

The first judgment module is used for judging whether the vehicle enters a crawling mode or not according to the current running information of the vehicle.

And the first torque control module is used for controlling the output torque of the motor to be changed from the current torque to the target torque when the vehicle enters the crawling mode so as to change the vehicle speed from the current vehicle speed to the target crawling vehicle speed, and the target crawling vehicle speed can be set.

The first torque control module includes:

the feedforward control module is used for calculating feedforward torque according to the current vehicle speed and the road gradient;

the feedback control module is used for calculating feedback torque according to the current vehicle speed difference, the current vehicle speed difference is a difference value between the target crawling vehicle speed and the current vehicle speed, the feedback control module comprises a proportional control module and an integral control module, the feedback torque comprises proportional feedback torque obtained by calculation of the proportional control module and integral feedback torque obtained by calculation of the integral control module, the proportional control module is activated when the vehicle enters a crawling mode, the integral control module is activated under a preset condition, and the preset condition comprises:

the pressure of the current brake master cylinder is smaller than Ps, and the current vehicle speed difference is smaller than Vs, wherein Ps and Vs can be calibrated.

Specifically, the formula for calculating the proportional feedback torque is as follows: u1(k) kp · e (k), where u1(k) is the proportional feedback torque at the k-th time, kp is the proportional coefficient, and e (k) is the vehicle speed difference at the k-th time;

setting the current vehicle speed difference as delta V;

when the delta V is more than or equal to-delta V1 and less than or equal to delta V1, the value of kp is kp1, the value of delta V1 is more than 0, and the value of kp1 is more than 0;

when the delta V1< delta V2 or-delta V2< delta V < -delta V1, the value of kp is kp2, kp2 is positively correlated with the absolute value of delta V, and kp2 is greater than kp 1;

wherein, the delta V1, the delta V2, the kp1 and the kp2 can be calibrated;

the integral feedback torque is calculated by the formula:where u2(k) is the integrated feedback torque at time k, ki is the integration coefficient,the sum of the current vehicle speed differences from the ith moment to the kth moment;

when delta V is more than or equal to-delta V3 and less than or equal to delta V3, the values of ki are ki1, delta V3>0 and ki1> 0;

when delta V3 is not more than delta V < delta V4 or-delta V4< delta V < -delta V3, the value of ki is ki2, ki2 is in positive correlation with the absolute value of delta V, and ki2 is greater than ki 1;

wherein, the delta V3, the delta V4, the ki1 and the ki2 can be calibrated.

Optionally, the crawling mode comprises a first crawling mode and a second crawling mode;

the first judging module comprises:

the first judgment module is used for judging whether the vehicle enters a crawling mode or not according to the current running information of the vehicle;

the first judgment module II is used for judging whether the vehicle slips or not according to the current running information of the vehicle;

if the vehicle enters the crawling mode and does not slip, the vehicle enters a first crawling mode;

if the vehicle enters the crawling mode and the vehicle slips, the vehicle enters a second crawling mode;

the target crawling speed comprises a first target crawling speed and a second target crawling speed, the first target crawling speed corresponds to a first crawling mode, the second target crawling speed corresponds to a second crawling mode, and the second target crawling speed is smaller than the first target crawling speed; the target torques include a first target torque corresponding to the first target creep vehicle speed and a second target torque corresponding to the second target creep vehicle speed.

Optionally, the system further comprises a second judging module, configured to judge whether the vehicle exits the crawling mode according to current driving information of the vehicle;

the second torque control module is used for controlling the output torque of the motor to be changed from the current torque to the requested torque when the vehicle exits the crawling mode, so that the current vehicle speed of the vehicle is changed to the requested vehicle speed, and the requested vehicle speed responds to the current driving requirement;

the output torque variation of the motor is delta T within a preset time after the creep mode is exited by triggering, the delta Tmin is not more than the delta T is not more than the delta Tmax, and the delta Tmin and the delta Tmax can be calibrated.

The crawling control device provided by the embodiment can execute the crawling control method provided by any embodiment of the invention, and has corresponding functional modules and beneficial effects of the execution method.

Example four

Based on the first embodiment, the second embodiment and the third embodiment, the present embodiment provides an execution strategy of the crawling control method in several driving states.

In one embodiment, the electric automobile is stationary on a flat road, the vehicle has no fault, the road condition is good, and the road surface is a flat road. The driver puts the gear into the D gear, slightly lifts the brake, and does not step on the accelerator pedal. And the vehicle control unit judges that the vehicle enters a first crawling mode. And the feedforward control module is activated to obtain feedforward torque. The feedforward control module calculates the feedforward torque according to the current vehicle speed as the road surface is a flat road. Only the proportional control module in the feedback control module is activated, the current vehicle speed difference is large, kp takes a large value and is reduced along with the reduction of the current vehicle speed difference, the target vehicle speed is quickly approached, the integral control module is not activated, and vehicle leaping is avoided. The target torque is the sum of the feedforward torque and the proportional feedback torque. And the target torque is limited by the maximum torque and the minimum torque and then is sent to the motor control unit, the motor control unit controls the output torque of the driving motor to be the currently calculated target torque, and the output torque is finally transmitted to the wheels through the single-stage speed reducer.

Along with the progress of crawling control, current vehicle speed difference reduces, and integral control module in the feedback control module activates, and proportional control module and integral control module calculate simultaneously promptly, guarantee coefficient kp and coefficient ki and change gradually along with the change of current vehicle speed difference, the output torque of dynamic adjustment motor, finally maintain more stable speed of a motor. And after the currently calculated target torque passes through the maximum torque and the minimum torque limit, the currently calculated target torque is sent to the motor control unit.

In another embodiment, the electric automobile is stationary on a flat road, the vehicle has no fault, the road surface is a flat road, and the road adhesion coefficient of the road surface is low due to rain and snow conditions. And starting the D gear of the electric automobile on the flat road to enter a crawling control mode. At the moment, whether the wheel slips or not is judged according to the collected wheel speed signal, the wheel acceleration signal, the actual vehicle speed and other signals. And if the wheels slip, entering a second crawling control mode and maintaining the vehicle in a safe state. And the feedforward control module is activated, and the proportional control module in the feedback control module is activated. The feedforward control module calculates the feedforward torque according to the current vehicle speed as the road surface is a flat road. And the integral control module is not activated because the second target vehicle speed is smaller, the current vehicle speed difference is smaller, kp is kept unchanged within a certain range. The target torque calculated by the feedforward control module and the feedback control module ensures the crawling starting of the vehicle on a low-level road.

Along with the progress of crawling control, the current speed difference of the vehicle is reduced, an integral control module in the feedback control module is activated, namely the proportional control module and the integral control module calculate simultaneously. Because the current vehicle speed difference is small, the coefficient kp and the coefficient ki are kept unchanged within a certain range. The target torque calculated by the feedforward control module and the feedback control module ensures that the vehicle runs on a low-level road in a crawling mode.

In another embodiment, the electric automobile is static on a slope, the vehicle has no fault, the road condition is good, and the road surface has a slope. And (5) the driver puts the gear into the gear D and slightly lifts the brake. The electric vehicle enters a creep control mode. And the feedforward control module is activated to obtain feedforward torque. And the feedforward control module calculates the feedforward torque according to the current vehicle speed and the road surface gradient. Only the proportional control module of the feedback control module is activated. Because the current vehicle speed difference is large, kp takes a large value. And an integral control module in the feedback control module is not activated, so that bouncing is prevented. The target torque calculated by the feedforward control module and the feedback control module ensures the crawling starting of the vehicle on a high-attachment slope.

Along with the progress of crawling control, the current speed difference of the vehicle is reduced, an integral control module in the feedback control module is activated, namely the proportional control module and the integral control module calculate simultaneously. The coefficient kp and the coefficient ki are varied in real time with the current vehicle speed difference. The target torque calculated by the feedforward control module and the feedback control module ensures that the vehicle runs on a low-level road in a crawling mode.

In another embodiment, the electric automobile is static on a slope, the vehicle has no fault, the road adhesion coefficient is low due to rain and snow conditions, and the road has a slope. And starting the slope D gear of the electric automobile to enter a crawling control mode. At the moment, whether the wheel slips or not is judged according to the collected wheel speed signal, the wheel acceleration signal, the actual vehicle speed and other signals. And if the wheels slip, entering a second crawling module and maintaining the vehicle in a safe state. And the feedforward control module is activated to obtain feedforward torque. And the feedforward control module calculates the feedforward torque according to the current vehicle speed and the road surface gradient. Only the proportional control module of the feedback control module is activated. And because the second target vehicle speed is smaller, the current vehicle speed difference is smaller, and kp is kept unchanged within a certain range. The integral control module in the feedback control module is not activated. The target torque calculated by the feedforward control module and the feedback control module ensures the crawling starting of the vehicle on a low-attachment slope.

Along with the progress of crawling control, the current speed difference of the vehicle is reduced, an integral control module in the feedback control module is activated, namely the proportional control module and the integral control module calculate simultaneously. The coefficient kp and the coefficient ki are both kept constant within a certain range. The target torque calculated by the feedforward control module and the feedback control module ensures that the vehicle runs in a crawling manner on a low-attachment slope.

In another embodiment, the electric vehicle is on level roads, the vehicle is in D gear, the crawling mode is entered, and the driver steps on the accelerator pedal. In the transient process, the electric automobile quits the crawling control in a short time, in the preset time, the variation of the output torque of the motor is delta T, delta Tmin is not less than delta T and not more than delta Tmax, the impact is avoided, the torque is gradually transited to the acceleration mode, the torque is sent to the motor control unit, and the comfort of crawling to the acceleration process can be guaranteed.

In another embodiment, after the electric automobile slides for a period of time at a high speed on a flat road, the creep control entry condition is met, and the electric automobile enters the creep mode. During the transient process, the feedforward control module is activated, and the proportional control module in the feedback control module is activated. The feedforward control module calculates the feedforward torque according to the current vehicle speed as the road surface is a flat road. The coefficient kp is dynamically adjusted with the current vehicle speed difference, while the integral control module is temporarily inactive. Because the coasting generally needs negative torque for energy recovery, the output torque is switched to the torque output of the creep control from the driver demand, and the output torque is limited by the maximum torque and the minimum torque, so that the comfort of switching from the high-speed coasting mode to the creep mode is ensured.

In another embodiment, the electric vehicle enters the creep control mode on a flat road, and a driving prohibition fault suddenly occurs. The current driving cycle only warns the driver through the instrument and does not actually limit the driving of the vehicle so as to ensure that the vehicle can drive into a safety zone, and the vehicle controller is forbidden to drive after being awakened again after sleeping.

EXAMPLE five

Fig. 6 is a schematic structural view of the vehicle in the present embodiment. FIG. 6 illustrates a block diagram of an exemplary vehicle 412 suitable for use in implementing embodiments of the present invention. The vehicle 412 shown in fig. 6 is only an example and should not impose any limitation on the functionality and scope of use of embodiments of the present invention.

As shown in fig. 6, the vehicle 412 is represented in the form of a general-purpose terminal. The components of the vehicle 412 may include, but are not limited to: a vehicle body (not shown), one or more processors 416, a memory device 428, and a bus 418 that connects the various system components, including the memory device 428 and the processors 416.

Bus 418 represents one or more of any of several types of bus structures, including a memory device bus or memory device controller, a peripheral bus, an accelerated graphics port, and a processor or local bus using any of a variety of bus architectures. By way of example, such architectures include, but are not limited to, Industry Standard Architecture (ISA) bus, Micro Channel Architecture (MAC) bus, enhanced ISA bus, Video Electronics Standards Association (VESA) local bus, and Peripheral Component Interconnect (PCI) bus.

The vehicle 412 typically includes a variety of computer system readable media. Such media may be any available media that is accessible by vehicle 412 and includes both volatile and nonvolatile media, removable and non-removable media.

Storage 428 may include computer system readable media in the form of volatile Memory, such as Random Access Memory (RAM) 430 and/or cache Memory 432. The vehicle 412 may further include other removable/non-removable, volatile/nonvolatile computer system storage media. By way of example only, storage system 434 may be used to read from and write to non-removable, nonvolatile magnetic media (not shown in FIG. 6, commonly referred to as a "hard drive"). Although not shown in FIG. 6, a magnetic disk drive for reading from and writing to a removable, nonvolatile magnetic disk (e.g., a "floppy disk") and an optical disk drive for reading from or writing to a removable, nonvolatile optical disk such as a Compact disk Read-Only Memory (CD-ROM), Digital Video disk Read-Only Memory (DVD-ROM) or other optical media may be provided. In these cases, each drive may be connected to bus 418 by one or more data media interfaces. Storage 428 may include at least one program product having a set (e.g., at least one) of program modules that are configured to carry out the functions of embodiments of the invention.

A program/utility 440 having a set (at least one) of program modules 442 may be stored, for instance, in storage 428, such program modules 442 including, but not limited to, an operating system, one or more application programs, other program modules, and program data, each of which examples or some combination thereof may comprise an implementation of a network environment. The program modules 442 generally perform the functions and/or methodologies of the described embodiments of the invention.

The vehicle 412 may also communicate with one or more external devices 414 (e.g., keyboard, pointing terminal, display 424, etc.), with one or more terminals that enable a user to interact with the vehicle 412, and/or with any terminals (e.g., network card, modem, etc.) that enable the vehicle 412 to communicate with one or more other computing terminals. Such communication may occur via input/output (I/O) interfaces 422. Also, the vehicle 412 may communicate with one or more networks (e.g., a Local Area Network (LAN), Wide Area Network (WAN), and/or a public Network, such as the internet) via the Network adapter 420. As shown in FIG. 6, the network adapter 420 communicates with the other modules of the vehicle 412 over the bus 418. It should be appreciated that although not shown in the figures, other hardware and/or software modules may be used in conjunction with the vehicle 412, including but not limited to: microcode, end drives, Redundant processors, external disk drive Arrays, RAID (Redundant Arrays of Independent Disks) systems, tape drives, and data backup storage systems, among others.

The processor 416 executes various functional applications and data processing by executing programs stored in the storage device 428, for example, implementing a crawling control method provided by an embodiment of the present invention, the method including:

s1, acquiring the current running information of the vehicle in real time;

s2, judging whether the vehicle enters a crawling mode or not according to the current running information of the vehicle, and if so, jumping to S3;

s3, controlling the output torque of the motor to change from the current torque to a target torque so that the vehicle speed changes from the current vehicle speed to a target creep vehicle speed, wherein the target creep vehicle speed can be set;

controlling the output torque of the motor to change from the current torque to the target torque comprises the following steps:

feedforward control, calculating a feedforward torque according to the current vehicle speed and the road gradient;

feedback control, calculating feedback torque according to the current vehicle speed difference, wherein the current vehicle speed difference is the difference value between the target crawling vehicle speed and the current vehicle speed, the feedback control comprises proportional control and integral control, the feedback torque comprises proportional feedback torque obtained by proportional control calculation and integral feedback torque obtained by integral control calculation, the proportional control is activated when the vehicle enters a crawling mode, the integral control is activated under a preset condition, and the preset condition comprises:

the current master cylinder pressure is less than Ps and the current vehicle speed difference is less than Δ Vs, where Ps and Δ Vs are calibratable.

EXAMPLE six

The present embodiment provides a computer-readable storage medium on which a computer program is stored, the program, when executed by a processor, implementing a crawling control method according to an embodiment of the present invention, the method including:

s1, acquiring the current running information of the vehicle in real time;

s2, judging whether the vehicle enters a crawling mode or not according to the current running information of the vehicle, and if so, jumping to S3;

s3, controlling the output torque of the motor to change from the current torque to a target torque so that the vehicle speed changes from the current vehicle speed to a target creep vehicle speed, wherein the target creep vehicle speed can be set;

controlling the output torque of the motor to change from the current torque to the target torque comprises the following steps:

feedforward control, calculating a feedforward torque according to the current vehicle speed and the road gradient;

feedback control, calculating feedback torque according to the current vehicle speed difference, wherein the current vehicle speed difference is the difference value between the target crawling vehicle speed and the current vehicle speed, the feedback control comprises proportional control and integral control, the feedback torque comprises proportional feedback torque obtained by proportional control calculation and integral feedback torque obtained by integral control calculation, the proportional control is activated when the vehicle enters a crawling mode, the integral control is activated under a preset condition, and the preset condition comprises:

the current master cylinder pressure is less than Ps and the current vehicle speed difference is less than Δ Vs, where Ps and Δ Vs are calibratable.

Computer storage media for embodiments of the invention may employ any combination of one or more computer-readable media. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.

A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated data signal may take many forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may also be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

Computer program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C + + or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or terminal. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a Local Area Network (LAN) or a Wide Area Network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet service provider).