1. The automatic control method of the hydraulic motor of the pure electric loader is characterized by comprising the following steps:

1) judging the operation stage of the loader according to the state of the loader;

2) when the materials are contacted with the bucket, judging the difficulty degree of the operation according to the material attributes;

3) determining the operation stage and the operation difficulty degree of the stage to obtain the required power range [ P ] of the hydraulic system in the current stage_min，P_max]；

4) Determining a rotating speed range according to the current motor torque and the power range:

wherein, P_minThe minimum required power, w, of the hydraulic motor; p_maxThe maximum required power of the hydraulic motor, w; t is the current torque, Nm, of the hydraulic motor; n is_minThe minimum required rotating speed of the hydraulic motor is rad/s;

n_maxthe maximum required rotating speed of the hydraulic motor is rad/s;

5) according to the magnitude of the motor torque, on the basis of motor efficiency MAP data, a binary Lagrange interpolation method is adopted to obtain the mapping relation of the motor efficiency along with the rotating speed under the current torque;

6) setting a reference displacement Y of the hydraulic cylinder_refRecording the measured displacement of the hydraulic cylinder at the initial moment as Y_iniThe measured displacement of the hydraulic cylinder at any moment is recorded as Y_mesRecording the actual displacement of the hydraulic cylinder as Y;

Y_ref＝v_ref×t；

Y＝Y_mes-Y_ini；

in the formula, v_refThe average speed of the hydraulic cylinder which is ideally extended or retracted is m/s;

7) will refer to the hydraulic cylinder displacement Y_refDifference dY from actual cylinder displacement Y (dY ═ Y)_refY) and the current torque T of the motor are taken as two inputs of the fuzzy controller 1 to carry out fuzzy control to obtain the rotating speed N1 of the motor;

8) performing fuzzy control by using an absolute value dN (dN ═ N2-N1|) of a rotation speed difference between the motor rotation speed N2 with the highest efficiency corresponding to the current torque T and the motor rotation speed N1 and an efficiency difference d η (d η ═ η (N2, T) - η (N1, T)) as two input quantities of the fuzzy controller 2 to obtain a motor rotation speed increment δ N;

9) calculating the final expected rotating speed N of the motor by N1 and a rotating speed increment delta N;

N＝N1+k×δN；

in the formula, k is an incremental rotation speed coefficient, and when N2 is more than or equal to N1, k is 1; when N2 < N1, k is-1.

2. The automatic control method for hydraulic motor of pure electric loader according to claim 1, wherein in step 5, the efficiency η (n, T) at any intersection of rotation speed and torque can be determined according to four points (n) nearest to n and T in the MAP data of motor efficiency₁，T₁)，(n₂，T₁)，(n₁，T₂)，(n₂，T₂) Calculating the efficiency to obtain the motor rotating speed N2 with the highest efficiency in the rotating speed range determined in the step 4;

point (n, T)₂) Treatment efficiency eta (n, T)₂) Calculating the formula:

point (n, T)₁) Treatment efficiency eta (n, T)₁) Calculating the formula:

the efficiency at point (n, T) can be based on point (n, T)₁) And a point (n, T)₂) The treatment efficiency calculation formula is as follows:

3. the automatic control method for the hydraulic motor of the pure electric loader according to claim 1, wherein in step 7, the specific implementation method is as follows:

the hydraulic cylinder displacement difference dY and the motor torque T are used as fuzzy input quantities, and the motor speed N1 is used as a fuzzy output quantity;

three fuzzy sets are used to describe the cylinder displacement difference dY: negative large NB, small S, positive large PB;

three fuzzy sets are used to describe the motor torque T: small S, medium C and large B;

five fuzzy sets are used for describing the motor speed N1: minimum VS, small S, medium C, large B, maximum VB.

4. The automatic control method for the hydraulic motor of the pure electric loader according to claim 1, wherein the fuzzy controller output of the step 7 is a motor speed N1, and the motor speed value takes the load size and the hydraulic system output into consideration and does not take the efficiency of the working point of the hydraulic motor into consideration.

5. The automatic control method for the hydraulic motor of the pure electric loader according to claim 1, wherein in step 8, the specific implementation method is as follows:

the absolute value dN of the rotation speed difference and the efficiency difference d eta are used as fuzzy input quantities, and the motor rotation speed delta N is used as a fuzzy output quantity;

three fuzzy sets are used to describe the absolute value dN of the rotational speed difference: small S, medium C and large B;

three fuzzy sets are used to describe the efficiency difference d η: small S, medium C and large B;

five fuzzy sets are adopted to describe the motor speed increment delta N: minimum VS, small S, medium C, large B, maximum VB.

Background

The traditional diesel loader has the problems of poor emission, high energy consumption, low efficiency and the like during operation. In addition, the diesel loader adopts an engine to drive the traveling system and the hydraulic system simultaneously, and the two systems are in a highly coupled state. The driver can not independently drive one of the accelerator and the gear shifting or braking, which can cause the efficiency of the loader in the process of digging and unloading to be low, thereby affecting the efficiency of the whole cycle work. Meanwhile, the driver lacks intuitive feeling on the working state of the hydraulic system of the loader, and the violent action of the driver on the control handle can cause the hydraulic system to be in an overflow state for a long time during the operations of digging, lifting and the like, so that additional energy loss is caused.

The efficient zero-pollution pure electric loader which is driven by the double motors to separate the traveling system from the hydraulic system is an effective solution. The loader often adopts an accelerator pedal and a brake pedal to control the walking motor, but a driver has difficulty in simultaneously controlling the hydraulic motor through the pedals.

At present, a method that a hydraulic motor outputs fixed rotating speed or fixed power is commonly adopted in a pure electric loader, but the method cannot fully utilize the advantages of a wide rotating speed range and a wide high-efficiency interval of the motor, and cannot adjust the rotating speed of the motor according to the load, so that unnecessary energy loss is caused. Researchers at home and abroad also propose a method for adjusting the rotating speed of the hydraulic motor according to the operation intention of a driver on devices such as a bucket cylinder operating lever, a movable arm cylinder operating lever, a steering wheel and the like. The method has higher requirements on the experience of a driver, and the operation of the driver directly influences the energy consumption and the output of the hydraulic system. Particularly, under the heavy-load working condition, the external pressure is high, the required flow is low, the action speed of the hydraulic cylinder is low, and drivers with little experience work at high speed to improve the speed of the hydraulic cylinder, so that the hydraulic motor works at high speed, and great overflow loss is caused.

The invention aims to provide an automatic control strategy of a hydraulic motor, which comprehensively considers the required power and flow of a hydraulic system and considers the efficiency characteristic of the motor, aiming at a pure electric loader with double motors. The method can dynamically adjust the output rotating speed of the hydraulic motor according to the external load change in the operation stage, and has the output and energy consumption of the hydraulic system. The output flow of the hydraulic pump is matched with the actual system requirement, the energy loss of the system is reduced under the condition that the output is not reduced, and the overall operation efficiency of the hydraulic system is improved.

Disclosure of Invention

The embodiment of the invention aims to provide an automatic control method for a hydraulic motor of a pure electric loader, and aims to solve the problems that the output flow of a hydraulic pump is matched with the requirement of an actual system, the energy loss of the system is reduced under the condition of not reducing the output, and the overall operation efficiency of a hydraulic system is improved.

The embodiments of the present invention are implemented such that,

the hydraulic system of the pure electric loader mainly comprises a constant delivery pump, a hydraulic motor, a multi-way valve, a steering control valve, a rotary bucket oil cylinder, a movable arm oil cylinder and a steering oil cylinder;

the multi-way valve comprises a rotating bucket control valve and a movable arm control valve, when the rotating bucket control valve is opened rightwards, the rotating bucket hydraulic cylinder extends out and is opened leftwards, the rotating bucket hydraulic cylinder retracts, when the control valve is closed, the rotating bucket hydraulic cylinder keeps the original position, and the movable arm control valve and the rotating bucket control valve are the same;

when the hydraulic system of the loader works, the output flow of the constant delivery pump is controlled by adjusting the rotating speed of the hydraulic motor, and the designated hydraulic cylinder is driven to generate corresponding displacement under the action of the control valve.

The automatic control method of the hydraulic motor of the pure electric loader comprises the steps of firstly judging the working stage of the loader according to state information such as the gear position of the loader, the pressure of a hydraulic cylinder, the speed of the loader and the like;

then, judging the difficulty degree of operation according to the attribute of the material to obtain the required power range of the hydraulic system under the material at the stage; then determining the range of the expected output rotating speed of the motor according to the current torque and the power range, and simultaneously calculating the mapping relation between the motor efficiency and the rotating speed under the current torque by a binary Lagrange interpolation method;

and finally, obtaining the expected motor rotating speed through fuzzy control according to the torque signal of the hydraulic motor and the displacement signal of the action hydraulic cylinder and considering the efficiency attribute of the hydraulic motor, and realizing the automatic control of the hydraulic motor and the matching of the flow rate as required.

The automatic control method for the hydraulic motor of the pure electric loader provided by the embodiment of the invention has the following beneficial effects:

the invention provides an automatic control algorithm for a hydraulic motor of a pure electric loader, which reduces the operation difficulty of a driver, solves the problems of low output and high energy consumption of a hydraulic system caused by insufficient experience of the driver and the like, and promotes the unmanned driving process of the loader. Meanwhile, the invention solves the problem that the required power of the loader hydraulic system is different when different materials are in different stages, and the actual output power is matched with the required power. The rotating speed of the hydraulic motor dynamically changes along with the load in the operation process, the output flow of the hydraulic pump is matched with the actual flow, and the throttling loss and the overflow loss are reduced. In addition, the hydraulic motor works in a high-efficiency interval as much as possible, the loss of the motor is reduced, the action speed of the hydraulic cylinder is considered, and the output of a hydraulic system is considered. The fuzzy control algorithm adopted by the invention can calculate output values under different inputs in an off-line manner, and stores the output values in the controller in a table look-up manner, so that the universality and the practicability are strong, and the application prospect is good.

Drawings

FIG. 1 is a schematic diagram of a hydraulic system;

FIG. 2 is a system work flow diagram;

FIG. 3 is a schematic diagram of a binary Lagrange interpolation method for calculating the efficiency of any point of a motor;

FIG. 4 is an input-output relationship of a fuzzy controller;

FIG. 5 is a graph of motor efficiency versus rotational speed;

fig. 6 shows a typical case of two operating points of the motor.

In the drawings: the hydraulic control system comprises a fixed displacement pump 1, a hydraulic motor 2, a priority valve 3, a multi-way valve 4, a bucket control valve 4-1, a boom control valve 4-2, a pilot control valve 5, a double-acting valve 6, a bucket cylinder 7, a boom cylinder 8, a steering cylinder 9 and a steering control valve 10.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Specific implementations of the present invention are described in detail below with reference to specific embodiments.

Fig. 1 is a schematic diagram of a hydraulic system of a pure electric loader, and mainly comprises a constant delivery pump 1, a hydraulic motor 2, a multi-way valve 4, a steering control valve 10, a rotating bucket oil cylinder 7, a movable arm oil cylinder 8 and a steering oil cylinder 9;

the multi-way valve 4 comprises a rotary bucket control valve 4-1 and a movable arm control valve 4-2;

when the bucket control valve is opened rightwards, the bucket hydraulic cylinder extends out and is opened leftwards, the bucket hydraulic cylinder retracts, when the control valve is closed, the bucket hydraulic cylinder keeps the original position, and the movable arm control valve and the bucket control valve are the same;

when the hydraulic system of the loader works, the output flow of the constant delivery pump is controlled by adjusting the rotating speed of the hydraulic motor, and the designated hydraulic cylinder is driven to generate corresponding displacement under the action of the control valve.

FIG. 2 is a main working process of the present invention, which is characterized in that the present invention firstly judges the working stage of the loader according to the state information of the gear position of the loader, the pressure of the hydraulic cylinder, the vehicle speed, etc., then judges the difficulty of the operation according to the property of the material, obtains the required power range of the hydraulic system under the material in the stage, then determines the range of the expected output rotating speed of the motor according to the current torque and the power range, and simultaneously calculates the mapping relation between the efficiency and the rotating speed of the motor under the current torque by a binary Lagrange interpolation method;

and finally, obtaining the expected motor rotating speed through fuzzy control according to the torque signal of the hydraulic motor and the displacement signal of the action hydraulic cylinder and considering the efficiency attribute of the hydraulic motor, and realizing the automatic control of the hydraulic motor and the matching of the flow rate as required.

The automatic control method of the hydraulic motor of the pure electric loader comprises the following specific steps:

1) firstly, the operation stage of the loader is judged according to the state of the loader (information such as gear, big cavity pressure of a rotary bucket cylinder, big cavity pressure of a movable arm cylinder, vehicle speed and the like), the common operation condition of the loader is v-shaped operation, the v-shaped operation condition can be divided into 7 stages according to the operation characteristics of a hydraulic system, and the name and the judgment standard of each stage are shown in table 1.

For convenience of description, a threshold value is respectively set for the vehicle speed, the pressure of the large cavity of the rotary bucket cylinder and the pressure of the large cavity of the movable arm cylinder, the vehicle speed, the pressure of the large cavity of the rotary bucket cylinder and the pressure of the large cavity of the movable arm cylinder are judged to be low when the threshold value is lower than the threshold value, and the vehicle speed, the pressure of the large cavity of the rotary bucket cylinder and the pressure of the large cavity of the movable arm cylinder are judged to be high when the threshold value is higher than the threshold value.

TABLE 1 Hydraulic System stage Classification and judgment

2) Next, when the materials are in contact with the bucket, the difficulty degree of operation is judged according to the material properties, and the operation objects of the loader have diversified characteristics, including the bulk materials with different properties such as sand, coal briquettes, iron ore and the like;

in the same working stage, when different objects are operated, the power required by the hydraulic system is greatly different, particularly in the stages of V2 digging, V3 full load retreating and V4 boom lifting, the operation difficulty of the V2 digging stage is related to parameters such as material density, particle size, fluidity, material pile size, repose angle and the like, the full load transportation and boom lifting stage is related to the material density, and the operation difficulty is higher when the density is higher under the condition of full bucket.

3) After the operation stage and the operation difficulty degree of the stage are determined, the required power range [ P ] of the hydraulic system in the current stage can be obtained_min，P_max]。

The power range can be determined by carrying out multiple load spectrum experiments on materials with different attributes through the loaders with the same model and analyzing experimental data;

the method is characterized in that the required power is different in different stages, wherein the required power is the largest in V2 and V4 stages, the V3 times is the lower in V6 and V7 stages, and the V1 and V5 stages are the minimum, and the larger the operation difficulty is, the higher the required power is in the same stage; conversely, the lower the power demand.

4) Then, the rotating speed range can be determined according to the current motor torque and power range:

wherein, P_minThe minimum required power, w, of the hydraulic motor; p_maxThe maximum required power of the hydraulic motor, w; t is the current torque, Nm, of the hydraulic motor; d_minThe minimum required rotating speed of the hydraulic motor is rad/s; n is_maxThe maximum required rotating speed of the hydraulic motor is rad/s.

5) Meanwhile, according to the magnitude of the motor torque, on the basis of motor efficiency MAP data, a binary Lagrange interpolation method is adopted to obtain the mapping relation of the motor efficiency along with the rotating speed under the current torque, and the principle of the binary Lagrange interpolation method is shown in FIG. 3;

the efficiency eta (n, T) at the intersection of any rotating speed and torque can be determined according to four points (n) nearest to n and T in the motor efficiency MAP data₁，T₁)，(n₂，T₁)，(n₁，T₂)，(n₂，T₂) The efficiency calculation of (3) yields the motor speed N2 at which the efficiency is highest in the speed range determined in step 4.

Point (n, T)₂) Treatment efficiency eta (n, T)₂) Calculating the formula:

point (n, T)₁) Treatment efficiency eta (n, T)₁) Calculating the formula:

the efficiency at point (n, T) can be based on point (n, T)₁) And a point (n, T)₂) The treatment efficiency calculation formula is as follows:

6) setting the reference displacement Y of the hydraulic cylinder_refTaking the rotating bucket hydraulic cylinder as an example, when the rotating bucket control valve receives a command of opening to the right or opening to the left to start timing, the reference displacement of the rotating bucket hydraulic cylinder at the initial moment is set to be 0, the reference displacement of the rotating bucket hydraulic cylinder is a linear function of time, and the measured displacement of the hydraulic cylinder at the initial moment is recorded as Y_iniThe measured displacement of the hydraulic cylinder at any moment is recorded as Y_mesRecording the actual displacement of the hydraulic cylinder as Y;

Y_ref＝v_ref×t；

Y＝Y_mes-Y_ini；

in the formula, v_refIs the average speed, m/s, at which the cylinder is ideally extended or retracted.

7) Will reference the hydraulic cylinder displacement Y_refDifference dY from actual cylinder displacement Y (dY ═ Y)_ref-Y) and the current torque T of the motor are used as two inputs of the fuzzy controller 1 to perform fuzzy control to obtain the motor speed N1, and the specific method comprises the following steps:

the hydraulic cylinder displacement difference dY and the motor torque T are used as fuzzy input quantities, and the motor speed N1 is used as a fuzzy output quantity;

three fuzzy sets are used to describe the cylinder displacement difference dY: negative large NB, small S, positive large PB;

three fuzzy sets are also used to describe the motor torque T: small S, medium C and large B;

five fuzzy sets are used for describing the motor speed N1: minimum VS, small S, medium C, large B, maximum VB;

according to expert experience, fuzzy rules are formulated as shown in table 2:

TABLE 2 fuzzy rule of Motor speed N1

8) The absolute value dN (dN ═ N2-N1|) of the rotation speed difference between the motor rotation speed N2 and the motor rotation speed N1 corresponding to the current torque T and the efficiency difference d η (d η ═ η (N2, T) - η (N1, T)) are used as two input quantities of the fuzzy controller 2 to perform fuzzy control to obtain the motor rotation speed increment δ N, and the specific method is as follows:

the absolute value dN of the rotation speed difference and the efficiency difference d eta are used as fuzzy input quantities, and the motor rotation speed delta N is used as a fuzzy output quantity; three fuzzy sets are used to describe the absolute value dN of the rotational speed difference: small S, medium C and large B; three fuzzy sets are also used to describe the efficiency difference d η: small S, medium C and large B; five fuzzy sets are adopted to describe the motor speed increment delta N: minimum VS, small S, medium C, large B, maximum VB; according to expert experience, fuzzy rules are formulated as shown in table 3:

TABLE 3 fuzzy rule of motor speed increment δ N

9) Calculating the final expected rotating speed N of the motor from N1 and a rotating speed increment delta N;

N＝N1+k×δN；

in the formula, k is an incremental rotation speed coefficient, and when N2 is more than or equal to N1, k is 1; when N2 < N1, k is-1.

Fig. 4 depicts the input-output relationship of the fuzzy controller in steps 7-9.

In step 7, the two inputs of the fuzzy controller 1 are a motor torque T and a displacement difference dY, the motor torque depends on the external load of the hydraulic system, the larger the load is, the larger the motor torque is, the lower the flow required by the hydraulic system is at this time, and the lower the expected rotation speed of the motor is; conversely, the smaller the motor torque, the higher the desired motor speed.

The displacement difference dY represents the action of the hydraulic cylinder, when dY is NB, the actual displacement of the hydraulic cylinder is higher than the reference displacement, and the motor is expected to output a lower rotating speed; when dY is PB, the actual displacement of the hydraulic cylinder is lower than the reference displacement, the speed of the hydraulic cylinder is lower in a period of time, and the hydraulic motor is expected to output high rotating speed to enable the actual displacement to be close to the reference displacement.

The fuzzy controller 1 output of step 7 is the motor speed N1, which takes into account the load size and the hydraulic system output, but does not take into account the efficiency of the hydraulic motor operating point.

After the current torque of the motor is determined, the change of the motor efficiency along with the rotating speed is shown in fig. 5, the abscissa is the rotating speed, the ordinate is the efficiency, the motor efficiency is firstly and rapidly increased along with the increase of the rotating speed, then slowly increased until the maximum value is reached, and finally the efficiency begins to be slowly reduced, the mapping relation of the motor efficiency along with the rotating speed at different torques has similarity, and the similarity is consistent with the curve change trend shown in fig. 5.

The fuzzy controller 2 in step 8 further determines an expected motor rotation speed by combining the motor efficiency characteristics on the basis of the motor rotation speed N1, where N1 is a rotation speed obtained by considering the load and the output of the hydraulic system within a rotation speed range, N2 is a rotation speed with the highest efficiency point within the rotation speed range, and the rotation speed difference and the efficiency difference between the motor (N1, T) and the (N2, T) point have four typical cases shown in fig. 6; in the case of "small difference in rotation speed and large difference in efficiency" in fig. 6(a), the desired motor rotation speed should be adjusted from N1 to near N2; in the case of "large difference between rotation speed and efficiency" shown in fig. 6(b), the desired rotation speed should be adjusted to a position between N1 and N2; in the case of "small speed difference and small efficiency difference" in fig. 6(c), it is desirable that the influence of the rotation speed N1 or N2 on the result is not large, and the motor rotation speed N1 can be slightly adjusted; in fig. 6(d), the situation of "large speed difference and small efficiency difference" occurs, and the expected speed should be close to N1, and the speed increment δ N should be very small.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.