Hydrostatic bilateral driving control method and control system and skid loader

Abstract

The invention discloses a control method and a control system for hydrostatic bilateral driving and a skid steer loader. The control method comprises the steps that when a vehicle walking handle controls the vehicle to be in a straight moving mode, the rotating speeds of left and right motors of the vehicle are collected in real time through a rotating speed sensor, and the speed difference Vdiffer of left and right wheels is calculated in real time; when the speed difference Vdiffer of the left and right wheels is lower than a set speed difference value Vdiffer1, left and right wheel speed compensation is not triggered, and when the speed difference Vdiffer of the left and right wheels of the vehicle reaches or is higher than the set speed difference value Vdiffer1, the left and right variable pumps are triggered to conduct current compensation at the same time, and then left and right wheel speed compensation is achieved. The problem of normal linear walking deviation caused by actual parameter difference, variable characteristic difference and the like of a left variable pump, a right variable pump and a variable motor of a bilateral driving vehicle is solved, and meanwhile the problem of deviation caused by handle action micro-motion caused by motor displacement change response difference during gear shifting and impact in the traveling gear shifting process is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of engineering machinery, in particular to the technical field of straight-line travel control of hydrostatic double-sided drive vehicles. Background Art

[0002] Hydrostatic dual-drive systems are widely used in skid-steer loaders, bulldozers, pavers, and other mobile machinery. The hydrostatic drive system consists of a hydraulic pump and a hydraulic motor on each wheel. The hydraulic pump is a variable displacement pump, and the hydraulic motor is typically a radial piston motor (fixed or variable displacement). The left and right speeds of the machine are controlled by manipulating the travel handle to different positions, enabling various maneuvers such as straight travel and steering. Due to the dual-drive system, differences in displacement and control characteristics between the left and right hydraulic pumps and motors, as well as wear and tear on the transmission components, tracks, or tires, can cause speed differences between the two sides, leading to deviation during straight travel. During travel, if gear shifts are performed, the displacement of the hydraulic motor changes, and any differences in the response and process of the displacement change between the two motors can also cause speed differences during straight travel. Rapid speed changes can cause significant deviation. Furthermore, if gear shifts cause driving shock, the travel handle control can fluctuate, causing a slight deviation from the straight travel position to the left or right, which can easily cause the machine to deviate from the straight travel direction and initiate skid steering, which can also cause deviation.

[0003] To address the problem of deviation in straight-line travel caused by hydrostatic drive, some existing technical solutions set and adjust the correction factor, which actually involves modifying the corresponding displacement control parameters of the single-sided variable pump to achieve consistency in the actual speeds of the left and right wheels, so that the vehicle can maintain straight-line travel. The operator is required to subjectively feel whether the vehicle is deviating and modify the parameters. The maximum adjustable deviation range is limited, such as ±1% deviation, which mainly solves the deviation caused by inconsistent or worn tires or tracks. In some technical solutions, when the speed of one side is low during driving, if the controller receives a straight-line movement command, the controller can adjust the output flow of the first variable pump or the second variable pump until the first speed value is equal to the second speed value when the first speed value and the second speed value are inconsistent.

[0004] The existing solutions have the following technical defects: (1) Statically set the correction factor, adjust the correction factor after subjectively feeling the deviation phenomenon, and then conduct driving verification. Usually, multiple modifications and verifications are required, which is inefficient and low-precision. It cannot solve the influence of different parameter differences within the full displacement range of the pump motor (such as the difference in the actual displacement corresponding to the bilateral components under different currents), and cannot solve the deviation phenomenon caused by dynamic changes in the driving process, such as inconsistent left and right system loads causing inconsistent left and right pump motor efficiencies. (2) After detecting the inconsistency between the left and right speeds, only the side with the higher speed is slowed down. Single-sided adjustment is likely to cause a significant speed reduction problem. Single-sided adjustment at a low speed is likely to cause a stop. If the speeds are inconsistent at the same time, the vehicle enters the adjustment mode and needs to be completely consistent before exiting. Due to the fluctuation of the speed sensor, it is easier to enter the adjustment mode and difficult to exit the adjustment mode. If the adjustment mode is continuously performed, it is likely to cause the vehicle to adjust back and forth on both sides. The vehicle actually adjusts back and forth on the left and right, and the straight-line control is poor. (3) During the gear shifting process, the motor displacement changes rapidly, and the performance differences such as the response of the left and right motors cause inconsistent changes, which can easily cause the vehicle to deviate from the straight line. At the same time, the impact of the straight shifting process causes the instantaneous change in the handle control, which leads to deviation. The existing solution cannot solve the deviation problem under similar working conditions. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a control method, a control system and a skid loader for a hydrostatic double-sided drive vehicle, which solves the problem of normal straight-line deviation of the double-sided drive vehicle caused by differences in the actual parameters and variable characteristics of the left and right variable pumps and variable motors; at the same time, it solves the deviation problem caused by the response difference of the motor displacement change itself when shifting gears during straight-line travel and the micro-movement of the handle caused by the impact of the driving shifting process.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: A control method for hydrostatic bilateral drive, comprising: The vehicle accelerator pedal generates an engine speed request signal, which is analyzed by the vehicle controller and sent to the engine controller, which controls the engine to set the requested speed; The vehicle controller controls the displacement of the left and right variable displacement pumps by controlling the current of the displacement control valves. The hydraulic oil output by the left and right variable displacement pumps drives the left and right motors to rotate respectively, thereby driving the vehicle to move. When the vehicle is in straight-ahead mode controlled by the walking handle, the speed sensor collects the speed of the left and right motors of the vehicle in real time and calculates the speed difference V between the left and right wheels in real time. differ ; When the left and right wheel speed difference V differ Lower than the set speed difference value V differ When 1, the left and right wheel speed compensation is not triggered. When the left and right wheel speed difference V differ Reach or exceed the set speed difference value V differ When the value is 1, the left and right variable pumps are triggered to perform current compensation control simultaneously, thereby achieving left and right wheel speed compensation; During the left and right wheel speed current compensation process, the left and right wheel speed difference V differ Lower than the set speed difference value V differ 2 or when the vehicle is identified as non-straight driving mode, exit the left and right wheel speed compensation control, where Vdiffer 2 is less than V differ 1.

[0007] The aforementioned control method for hydrostatic bilateral drive is characterized in that the wheel speed compensation control method is: When walking in a straight line, set the current of the left and right variable pumps to A1, and the speed difference between the left and right wheels to V differ Reach or exceed the set speed difference value V differ 1, set the left and right wheel speed difference V differ The corresponding compensation current value is A2, which is calculated based on the speed difference value V differ The size of corresponds to a linear change; When the left and right wheel speed difference V differ When it is positive, that is, the left wheel speed is greater than the right wheel speed, the current controlling the left variable pump displacement control valve is A1-A2, and the current controlling the right variable pump displacement control valve is A1+A2; When the left and right wheel speed difference V differ When it is negative, that is, the left wheel speed is less than the right wheel speed, the current controlling the left variable pump displacement control valve is A1+A2, and the current controlling the right variable pump displacement control valve is A1-A2; The rate of change of the increase of the control current of the variable pump displacement control valve is defined as a1, and the rate of change of the decrease of the control current of the variable pump displacement control valve is defined as b1. The sizes of a1 and b1 are positively correlated with the vehicle speed.

[0008] The aforementioned control method for hydrostatic bilateral drive is characterized in that when a gear shift operation is performed when the vehicle is in a straight-ahead mode, i.e., when shifting up or down: Set compensation limit time t1; When the left and right wheel speed difference V differ Reach or exceed the set speed difference value V differ 1, the left and right variable pumps are triggered to perform current compensation control at the same time, setting the left and right wheel speed difference V differ The corresponding compensation current value is A3, which is calculated based on the speed difference value V differ The size of corresponds to a linear change. Under the same left and right wheel speed difference, A3 is greater than A2. When the left and right wheel speed difference V differ When the left wheel speed is greater than the right wheel speed, the current controlling the displacement control valve of the left variable pump is A1-A3, and the current controlling the displacement control valve of the right variable pump is A1+A3; When the left and right wheel speed difference V differ When it is negative, that is, the left wheel speed is less than the right wheel speed, the current controlling the left variable pump displacement control valve is A1+A3, and the current controlling the right variable pump displacement control valve is A1-A3; The rate of change of the increase in the control current of the variable pump displacement control valve is defined as a2, and the rate of change of the decrease in the control current of the variable pump displacement control valve is defined as b2, where the sizes of a2 and b2 are positively correlated with the vehicle speed, and at the same vehicle speed, a2 is greater than a1, and b2 is greater than b1.

[0009] The aforementioned control method of hydrostatic bilateral drive is characterized in that: when the left and right wheel speed difference V is compensated differ Lower than the set speed difference value V differ 2. Increase the waiting time t2. If the left and right wheel speed difference V is within the t2 time range differ Always lower than V differ 2, then exit the compensation, otherwise maintain the left and right wheel speed compensation control.

[0010] The aforementioned control method for a hydrostatic bilateral drive is characterized in that: within a limited time range t1 after a gear shift is triggered, if the travel handle is in a non-straight travel mode, and the lateral coordinate value X of the travel handle is less than the longitudinal coordinate value Y, and the lateral coordinate value X is less than a set boundary value X1, the straight travel mode is still considered, and left and right wheel speed compensation control is continued. If the lateral coordinate value X of the travel handle is greater than the longitudinal coordinate value Y or the lateral coordinate value X is greater than the set boundary value X1, the wheel speed compensation control is exited and the corresponding skid steering action is performed.

[0011] The aforementioned control method for a hydrostatic bilateral drive is characterized in that, during wheel speed compensation control caused by gear shifting in straight-ahead mode, when upshifting or downshifting at or near the maximum speed of the current gear, that is, when the current A1 of the left or right variable displacement pump displacement control valve reaches or nears the actual current A20 corresponding to the maximum displacement of the variable pump, the current range of the corresponding variable displacement pump displacement control valve is adjusted within a limited time range t1, that is, the current application range of the variable displacement pump displacement control valve is correspondingly adjusted to A10-A30, with A30 being less than A20, where current A10 is the current value corresponding to the minimum displacement of the variable pump. During wheel speed compensation at or near the maximum speed, the control current A1 of the variable displacement pump displacement control valve on the lower speed side increases from or near A30, and the control current A1 of the variable displacement pump displacement control valve on the higher speed side decreases from or near A30.

[0012] The aforementioned control method of hydrostatic bilateral drive is characterized in that: the motor is an electronically controlled variable motor, the displacement of which can be linearly and steplessly adjusted according to the left and right wheel speed difference V differ While compensating the current of the left and right variable pump displacement control valves, the displacement of the electronically controlled variable motor can be proportionally controlled. When the left and right wheel speed difference V differWhen the left wheel speed is positive, that is, the left wheel speed is greater than the right wheel speed, based on the above-mentioned left and right variable pump compensation control, the displacement of the left electronically controlled variable motor is controlled to increase, and the displacement of the right electronically controlled variable motor is controlled to decrease; when the left and right wheel speed difference V differ When it is negative, that is, the left wheel speed is less than the right wheel speed, on the basis of the aforementioned left and right variable pump compensation control, the displacement of the left electronically controlled variable motor is controlled to decrease, and the displacement of the right electronically controlled variable motor is controlled to increase, so as to achieve a rapid reduction in the speed difference between the two sides of the wheel.

[0013] A hydrostatic bilateral drive control system includes a vehicle controller, an engine controller, an engine, a left variable displacement pump, a left pump displacement control valve, a right variable displacement pump, a right pump displacement control valve, a shift control valve, a left hydraulic motor and a right hydraulic motor, a left motor displacement control valve, and a right motor displacement control valve; wherein, The vehicle controller is connected to the engine controller; The output end of the vehicle controller is connected to the signal input ends of the left pump displacement control valve and the right pump displacement control valve; The input shaft end of the left variable displacement pump is directly connected to the output shaft end of the engine, and the right variable displacement pump and the left variable displacement pump form a tandem pump; The two oil ports of the left variable displacement pump are directly connected to the two oil ports of the left hydraulic motor through pipelines, and the two oil ports of the right variable displacement pump are directly connected to the two oil ports of the right hydraulic motor through pipelines. The left and right hydraulic motors drive the left and right wheels of the vehicle respectively; The left pump displacement control valve and the right pump displacement control valve respectively control the displacement of the left variable pump and the right variable pump; The input end of the vehicle controller is also connected to the accelerator pedal signal, the walking handle signal and the shift button signal. The output end of the vehicle controller is also connected to the shift control valve signal input end. The shift control valve output end is connected to the left hydraulic motor and the right hydraulic motor displacement control valve input end. The output shaft positions of the left hydraulic motor and the right hydraulic motor are both provided with speed sensors, and are connected to the input end of the vehicle controller.

[0014] A hydrostatic bilateral drive control system includes a vehicle controller, an engine controller, an engine, a left variable displacement pump, a left pump displacement control valve, a right variable displacement pump, a right pump displacement control valve, a left electronically controlled variable motor and a right electronically controlled variable motor, a left motor displacement control valve, and a right motor displacement control valve; wherein, The vehicle controller is connected to the engine controller; The output end of the vehicle controller is connected to the signal input ends of the engine controller, the left pump displacement control valve, the right pump displacement control valve, the left electronically controlled variable motor displacement control valve and the right electronically controlled variable motor displacement control valve; The input shaft end of the left variable displacement pump is directly connected to the output shaft end of the engine, and the right variable displacement pump and the left variable displacement pump form a tandem pump; The two oil ports of the left variable displacement pump are directly connected to the two oil ports of the left electronically controlled variable displacement motor through pipelines, and the two oil ports of the right variable displacement pump are directly connected to the two oil ports of the right electronically controlled variable displacement motor through pipelines. The left and right electronically controlled variable displacement motors drive the left and right wheels of the vehicle respectively. The left pump displacement control valve and the right pump displacement control valve respectively control the displacement of the left variable pump and the right variable pump; The input end of the vehicle controller is also connected to the accelerator pedal signal, the travel handle signal and the shift button signal; The output shaft positions of the left electronically controlled variable motor and the right electronically controlled variable motor are both provided with speed sensors, and are connected to the input end of the vehicle controller.

[0015] A skid steer loader and the aforementioned control system are used to execute the aforementioned control method.

[0016] The beneficial effects of the present invention are: 1. During normal straight-line deviation, bilateral compensation is performed quickly. The greater the speed difference, the greater the compensation amount, and the faster the deviation correction is performed. Independent current increase and decrease rates are set, and the deviation correction process changes smoothly. 2. To address deviation caused by shifting in straight-line mode, a straight-line mode is defined within a time limit to prevent shift shock from causing handle fluctuations and deviation caused by exit compensation. Exit boundary conditions are set to maintain speed difference compensation. A new variable pump compensation current change rate is set to achieve rapid compensation and correction. When shifting at maximum speed, the current range of the bilateral variable pumps is actively adjusted to achieve bilateral compensation for shift deviation at maximum speed. 3. For the electronically controlled variable motor solution, the pump current compensation control process is added as an adjustable controlled object to achieve rapid left and right speed difference compensation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive work, among which: Figure 1 : Schematic diagram of a control system for a hydrostatic bilateral drive vehicle according to a second embodiment of the present invention; Figure 2 : Schematic diagram of a control system for a hydrostatic bilateral drive vehicle according to a third embodiment of the present invention; Figure 3 : Schematic diagram of electric control handle operation; Figure 4 : Variable pump compensation current and left and right wheel speed difference V differSchematic diagram of the linear relationship between In the figure: 1. Left variable displacement pump; 2. Left pump displacement control valve; 3. Right variable displacement pump; 4. Right pump displacement control valve; 5. Left motor; 5a. Left motor speed sensor; 5b. Left motor displacement control valve; 5c. Left electronically controlled variable displacement motor displacement control valve; 6. Right motor; 6a. Right motor speed sensor; 6b. Right motor displacement control valve; 6c. Right electronically controlled variable displacement motor displacement control valve; 7. Shift control valve; 8. Engine; 9. Engine controller; 10. Vehicle controller; 11. Accelerator pedal; 12. Travel handle; 13. Shift button. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0019] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices. Example 1

[0020] This embodiment provides a control method for hydrostatic bilateral drive, specifically comprising the following steps: The vehicle accelerator pedal generates an engine speed request signal, which is analyzed by the vehicle controller and sent to the engine controller, which controls the engine to set the requested speed; The vehicle controller controls the displacement of the left and right variable pumps by controlling the current of the displacement control valves. The hydraulic oil output by the left and right variable pumps drives the left and right motors to rotate respectively, thereby driving the vehicle to move. When the vehicle is in straight-ahead mode controlled by the walking handle, the speed sensor collects the speed of the left and right motors of the vehicle in real time and calculates the speed difference V between the left and right wheels in real time. differ ; When the left and right wheel speed difference Vdiffer Lower than the set speed difference value V differ 1, indicating the wheel speed difference V on both sides differ The difference is within the acceptable range, the vehicle still maintains a state close to straight driving, and the left and right wheel speed compensation is not triggered. When the left and right wheel speed difference V differ Reach or exceed the set speed difference value V differ 1, indicating the wheel speed difference V on both sides differ The difference has exceeded the acceptable range, triggering the left and right variable pumps to perform current compensation at the same time, thereby achieving left and right wheel speed compensation; During the left and right wheel speed current compensation process, the left and right wheel speed difference V differ Lower than the set speed difference value V differ 2 or when the vehicle is identified as non-straight driving mode, exit the left and right wheel speed compensation control, where V differ 2 is less than V differ 1. By setting the speed difference value V differ 2 as the exit compensation condition, increases the difficulty of exiting compensation, keeps the vehicle in the compensation control state for a longer time, and avoids the left and right wheel speed difference V differ 1. Repeated entry and exit compensation.

[0021] Rapid compensation of left and right wheel speeds is achieved through bilateral driving. When performing left and right wheel speed compensation, this method is actually divided into two compensation modes. The first is a straight-line driving deviation control mode, and the second is a straight-line driving gear shift deviation control mode.

[0022] For the first straight-line driving deviation control mode, the specific compensation process is as follows: When walking in a straight line, set the current of the left and right variable pump displacement control valves to A1. When the left and right wheel speed difference V differ Reach or exceed the set speed difference value V differ 1, set the left and right wheel speed difference V differ The corresponding compensation current value is A2, where the current compensation value A2 is proportional to the left and right wheel speed difference V differ The linear relationship between Figure 4 The A2 curve shown; when the left and right wheel speed difference V differ When the left wheel speed is positive, that is, the left wheel speed is greater than the right wheel speed, the current of the left variable pump displacement control valve is adjusted to A1-A2, and the current of the right variable pump displacement control valve is adjusted to A1+A2; when the left and right wheel speed difference V differ When it is negative, meaning the left wheel speed is less than the right wheel speed, the current in the left variable displacement pump control valve is adjusted to A1+A2, and the current in the right variable displacement pump control valve is adjusted to A1-A2. The rate of change for increasing the control current of the variable displacement pump control valve is defined as a1, and the rate of change for decreasing the control current of the variable displacement pump control valve is defined as b1. The magnitudes of a1 and b1 are positively correlated with vehicle speed.

[0023] For the second straight - line driving shift deviation control mode, this mode means shifting gears during the straight - line driving of the vehicle. The specific compensation process is as follows: Set a limited time t1; The left - right wheel speed difference V differ reaches or is higher than the set speed difference value V differ 1, trigger the current compensation control of the left - and - right variable pumps simultaneously, and set the corresponding compensation current value for the left - right wheel speed difference V differ as A3. When the left - right wheel speed difference V differ is positive, that is, the left wheel speed is greater than the right wheel speed, control the current of the left variable pump displacement control valve as A1 - A3, and control the current of the right variable pump displacement control valve as A1 + A3; when the left - right wheel speed difference V differ is negative, that is, the left wheel speed is less than the right wheel speed, control the current of the left variable pump displacement control valve as A1 + A3, and control the current of the right variable pump displacement control valve as A1 - A3; and define the change rate of the increase of the control current of the variable pump displacement control valve as a2, and the change rate of the decrease of the control current of the variable pump displacement control valve as b2. a2 and b2 are positively correlated with the vehicle speed, and at the same vehicle speed, a2 is greater than a1, and b2 is greater than b1.

[0024] When the compensation reaches the left - right wheel speed difference V differ lower than the set speed difference value V differ 2, add a waiting time t2, t2 << t1. If the left - right wheel speed difference V differ is always lower than V differ 2 within the t2 time range, then exit the compensation, otherwise maintain the left - right wheel speed compensation control; by setting the waiting time t2, the vehicle will not easily exit the bilateral wheel speed compensation mode. Even if the vehicle has met the exit conditions at a certain time point, it is necessary to ensure that the exit conditions are met throughout the entire t2 time period to confirm the exit of the compensation. Otherwise, continue to enter the cycle of bilateral wheel speed compensation, so as to filter out some false triggers or interference signals that instantaneously meet the exit conditions during the shift operation process.

[0025] The prerequisite for straight-line driving gear shift deviation compensation is that the travel handle maintains straight-line operation. Due to the impact of the vehicle's speed change after a gear shift, the handle may slightly move, which can easily cause the straight-line mode to be exited. Therefore, this embodiment introduces a wide straight-line range for the handle: within the action time t1 after the gear shift is triggered, if the travel handle is in non-straight-line mode, and the travel handle's lateral coordinate value X is less than the longitudinal coordinate value Y, and the lateral coordinate value X is less than the set boundary value X1 (the boundary value X1 can be set according to actual conditions), the vehicle is still considered to be in straight-line mode and bilateral wheel speed compensation continues. If the travel handle's lateral coordinate value X is greater than the longitudinal coordinate value Y or the lateral coordinate value X is greater than the set boundary value X1 (indicating that the travel handle has been deflected significantly, indicating a steering operation), straight-line wheel speed compensation is exited and the corresponding slip steering action is executed.

[0026] It should be noted that during wheel speed compensation caused by shifting in straight-ahead mode, when shifting up or down at or near the maximum speed of the current gear, the displacement of the variable pump has reached or is close to reaching its maximum. Within the set time range t1, the control range of the variable pump displacement control valve is adjusted, and the current application range of the variable pump displacement control valve is correspondingly adjusted to A10-A30, with the value of A30 being less than the actual current value A20 corresponding to the maximum displacement of the variable pump, where current A10 is the current value corresponding to the minimum displacement of the variable pump. During wheel speed compensation control at or near the maximum speed, the control current A1 of the variable pump displacement control valve on the lower speed side increases from or near A30, while the control current A1 of the variable pump displacement control valve on the higher speed side decreases from or near A30.

[0027] In the above two modes, when wheel speed compensation is performed, the compensation current value is proportional to the wheel speed difference V differ In a linear relationship, and at the same wheel speed difference V differ In the case of , the compensation current value in the straight shift mode is greater than the compensation current value in the straight mode, such as Figure 4 As shown, curve A2 is the current compensation value and the left and right wheel speed difference V in the straight driving mode. differ The linear relationship between the two, curve A3 is the current compensation value and the left and right wheel speed difference V in the straight shift mode. differ And when performing wheel speed compensation in both modes, the rate of change of the compensation current value is positively correlated with the vehicle speed.

[0028] It should be noted that, in this embodiment, curves A2 and A3 reflect the corresponding relationship between the wheel speed difference and the compensation current value in the two modes. In actual operation, this relationship can be a linear relationship or a multi-segment nonlinear relationship as required. The greater the wheel speed difference, the greater the compensation current.

[0029] In this embodiment, the motor selected is a hydraulic double-displacement motor. An electronically controlled variable motor can be selected, whose displacement changes linearly and can be adjusted steplessly. Its output is decelerated by a reducer and then drives the wheels. This is different from the above-mentioned scheme of adjusting the displacement of the left and right variable pumps to compensate for the speed difference. On the basis of the above-mentioned control scheme, during the straight-line process, on the basis of monitoring the left and right speed differences, in addition to performing bilateral variable pump displacement compensation control, the process increases the displacement control of the electronically controlled variable motor. For example, if the left wheel speed is greater than the right wheel speed, in addition to reducing the left pump displacement and increasing the right pump displacement, the displacement of the left electronically controlled variable motor is further reduced and the displacement of the right electronically controlled variable motor is increased to quickly reduce the bilateral speed difference and realize straight-line control of the entire machine. Example 2

[0030] A system for a hydrostatically driven vehicle, such as Figure 1As shown, it includes a vehicle controller 10, an engine controller 9, an engine 8, a left variable displacement pump 1, a left pump displacement control valve 2, a right variable displacement pump 3, a right pump displacement control valve 4, a left motor 5 and a right motor 6, wherein the left motor 5 and the right motor 6 are both dual-displacement hydraulic motors, and the vehicle controller 10 is connected to the engine controller 9; the output end of the vehicle controller 10 is connected to the signal input end of the left pump displacement control valve 2 and the right pump displacement control valve 4; the input shaft end of the left variable displacement pump 1 is directly connected to the output shaft end of the engine 8, and the right variable displacement pump 3 and the left variable displacement pump 1 form a series pump; the two oil ports of the left variable pump 1 are directly connected to the two oil ports of the left hydraulic motor through pipelines The two oil ports of the right variable pump 3 are directly connected to the two oil ports of the right hydraulic motor through pipelines, and the left and right hydraulic motors drive the left and right wheels of the vehicle respectively; the left pump displacement control valve 2 and the right pump displacement control valve 4 respectively control the displacement of the left variable pump 1 and the right variable pump 3 to achieve different pump flow outputs; the shift control valve 7 is connected to the left motor displacement control valve 5b of the left hydraulic motor and the right motor displacement control valve 6b of the right hydraulic motor. The output shaft positions of the left hydraulic motor and the right hydraulic motor are respectively provided with left motor speed sensors 5a and right motor speed sensors 6a to detect the actual left and right wheel motor speeds, and the actual left and right wheel speeds can be calculated according to the speed ratio and wheel diameter. The left hydraulic motor and the right hydraulic motor realize the switching of the left and right motor displacements through the left motor displacement control valve 5b and the right motor displacement control valve 6b, and the control pressure is output through the shift control valve 7; the signals of the left motor speed sensor 5a and the right motor speed sensor 6a are directly connected to the input end of the vehicle controller 10, and the input end of the vehicle controller 10 is connected to the signals of the accelerator pedal 11, the walking handle 12 and the shift button 13, and the actual engine speed of the engine controller 9 is received through CAN communication. The vehicle controller 10 and the engine controller 9 realize engine speed control through CAN communication. At the same time, the output end of the vehicle controller 10 is connected to the left pump displacement control valve 2, the right pump displacement control valve 4, and the shift control valve 7, and the variable pump displacement control and the shift valve output pressure control are realized by setting different currents.

[0031] For electric control handles, such as Figure 3 As shown, it usually has X and Y coordinate positions, corresponding to values of [0 1000] respectively. If X is 0 and Y has a value, it is a straight-line action. If Y is 0 and X has a value, it is a turning action in place. Other X and Y combinations are walking turning actions. For example, if the positions are FR and FL, it is a front right turn or front left turn action. Example 3

[0032] A control system for hydrostatic bilateral drive, such as Figure 2As shown, it includes a vehicle controller 10, an engine controller 9, an engine 8, a left variable displacement pump 1, a left pump displacement control valve 2, a right variable displacement pump 3, a right pump displacement control valve 4, a left motor 5 and a right motor 6, wherein the left motor 5 and the right motor 6 are both electronically controlled variable motors; the vehicle controller 10 is connected to the engine controller 9; the output end of the vehicle controller 10 is connected to the signal input ends of the left pump displacement control valve 2, the right pump displacement control valve 4, the left electronically controlled variable motor displacement control valve 5c and the right electronically controlled variable motor displacement control valve 6c; the input shaft end of the left variable pump 1 is directly connected to the output shaft end of the engine 8, and the right variable pump 3 and the left variable pump 1 form a series pump; the left variable pump 1 The two oil ports are directly connected to the two oil ports of the left electronically controlled variable motor 5 through pipelines, and the two oil ports of the right variable pump 3 are directly connected to the two oil ports of the right electronically controlled variable motor 6 through pipelines. The left and right electronically controlled variable motors drive the left and right wheels of the vehicle respectively; the left pump displacement control valve 2 and the right pump displacement control valve 4 respectively control the displacement of the left variable pump 1 and the right variable pump 3 to achieve different pump flow outputs; the input end of the vehicle controller 10 is also connected to the accelerator pedal 11 signal, the travel handle 12 signal and the shift button 13 signal; the output shaft positions of the left electronically controlled variable motor 5 and the right electronically controlled variable motor 6 are both provided with speed sensors 5a and 6a, and are connected to the input end of the vehicle controller 10.

[0033] Compared with the second embodiment, the left and right motors of this embodiment use electronically controlled variable motors, and the shift control valve is cancelled. The displacement control valves of the left and right electronically controlled variable motors are directly controlled by the vehicle controller 10. Since the displacement of the electronically controlled variable motor changes linearly, it can be adjusted steplessly. On the basis of monitoring the left and right speed differences, in addition to performing bilateral left and right pump displacement compensation control, the vehicle controller 10 increases the displacement control of the electronically controlled variable motors. For example, if the left wheel speed is greater than the right wheel speed, in addition to reducing the left pump displacement and increasing the right pump displacement, the left motor displacement is further increased and the right displacement motor is reduced, so that the bilateral speed difference is quickly reduced to achieve straight-line control of the entire machine. Example 4

[0034] A skid steer loader comprises the aforementioned control system, wherein the control system is used to execute the aforementioned control method.

[0035] In summary, the control method, control system and skid loader of the hydrostatic bilateral drive of the present invention solve the problem of deviation during normal straight-line travel of bilateral drive vehicles due to differences in actual parameters and variable characteristics of the left and right variable pumps and variable motors; at the same time, it solves the problem of deviation during straight-line travel caused by differences in the response of the motor displacement change itself when shifting gears and the micro-movement of the handle caused by the impact of the gear shifting process.

[0036] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A control method for hydrostatic bilateral drive, characterized by: include: The vehicle accelerator pedal generates an engine speed request signal, which is analyzed by the vehicle controller and sent to the engine controller, which controls the engine to set the requested speed; The vehicle controller controls the displacement of the left and right variable pumps by controlling the current of the displacement control valves. The hydraulic oil output by the left and right variable pumps drives the left and right motors to rotate respectively, thereby driving the vehicle to move. When the vehicle is in straight-ahead mode controlled by the walking handle, the speed sensor collects the speed of the left and right motors of the vehicle in real time and calculates the speed difference V between the left and right wheels in real time. differ ; When the left and right wheel speed difference V differ Lower than the set speed difference value V differ 1, the left and right wheel speed compensation control is not triggered. When the left and right wheel speed difference V differ Reach or exceed the set speed difference value V differ When 1, the left and right variable pumps are triggered to perform current compensation control simultaneously; During the left and right wheel speed current compensation process, the left and right wheel speed difference V differ Lower than the set speed difference value V differ 2 or when the vehicle is identified as non-straight driving mode, exit the left and right wheel speed compensation control, where V differ 2 is less than V differ 1.

2. The control method of a hydrostatic bilateral drive according to claim 1, characterized in that: The wheel speed compensation control method is: When walking in a straight line, set the current of the left and right variable pump displacement control valves to A1, and the left and right wheel speed difference V differ Reach or exceed the set speed difference value V differ 1, set the left and right wheel speed difference V differ The corresponding compensation current value is A2, which is calculated based on the speed difference value V differ The size of corresponds to a linear change; When the left and right wheel speed difference V differ When it is positive, that is, the left wheel speed is greater than the right wheel speed, the current controlling the left variable pump displacement control valve is A1-A2, and the current controlling the right variable pump displacement control valve is A1+A2; When the left and right wheel speed difference V differ When it is negative, that is, the left wheel speed is less than the right wheel speed, the current controlling the left variable pump displacement control valve is A1+A2, and the current controlling the right variable pump displacement control valve is A1-A2; The rate of change of the increase of the control current of the variable pump displacement control valve is defined as a1, and the rate of change of the decrease of the control current of the variable pump displacement control valve is defined as b1, and the sizes of a1 and b1 are positively correlated with the vehicle speed.

3. A control method for hydrostatic bilateral drive according to claim 1 or 2, characterized in that: When the vehicle is in straight-ahead mode and shifting gears, that is, shifting up or down: Set compensation limit time t1; When the left and right wheel speed difference V differ Reach or exceed the set speed difference value V differ 1, the left and right variable pumps are triggered to perform current compensation control at the same time, setting the left and right wheel speed difference V differ The corresponding compensation current value is A3, which is calculated based on the speed difference value V differ The size of corresponds to a linear change. Under the same left and right wheel speed difference, A3 is greater than A2. When the left and right wheel speed difference V differ When the left wheel speed is greater than the right wheel speed, the current controlling the displacement control valve of the left variable pump is A1-A3, and the current controlling the displacement control valve of the right variable pump is A1+A3; When the left and right wheel speed difference V differ When it is negative, that is, the left wheel speed is less than the right wheel speed, the current controlling the left variable pump displacement control valve is A1+A3, and the current controlling the right variable pump displacement control valve is A1-A3; The rate of change of the increase of the control current of the variable pump displacement control valve is defined as a2, and the rate of change of the decrease of the control current of the variable pump displacement control valve is defined as b2. The sizes of a2 and b2 are positively correlated with the vehicle speed, and at the same vehicle speed, a2 is greater than a1, and b2 is greater than b1.

4. The control method of hydrostatic bilateral drive according to claim 3, characterized in that: During the left and right wheel speed compensation control process, when the left and right wheel speed difference V differ is lower than the set speed difference value V differ 2, a waiting time t2 is added, t2 << t1. If the left and right wheel speed difference V differ remains lower than V differ 2 within the t2 time range, the compensation is exited; otherwise, the left and right wheel speed compensation control is maintained.

5. The control method of hydrostatic bilateral drive according to claim 3, characterized in that: Within the limited time t1 after the gear shift is triggered, if the travel handle is in non-straight travel mode, and the lateral coordinate value X of the travel handle is less than the longitudinal coordinate value Y, and the lateral coordinate value X is less than the set boundary value X1, it is still considered to be in straight travel mode and the left and right wheel speed compensation control continues. If the lateral coordinate value X of the travel handle is greater than the longitudinal coordinate value Y or the lateral coordinate value X is greater than the set boundary value X1, the wheel speed compensation control is exited and the corresponding skid steering action is performed.

6. The control method of hydrostatic bilateral drive according to claim 3, characterized in that: During wheel speed compensation control caused by shifting in straight-ahead mode, when shifting up or down at the maximum speed of the current gear or near the maximum speed, that is, when the current A1 of the left and right variable displacement pump displacement control valves reaches or nears the actual current A20 corresponding to the maximum displacement of the variable pump, the control range of the variable pump displacement control valve is adjusted within a limited time t1, that is, the variable pump displacement control valve current application range is adjusted to A10-A30, with A30 being less than A20, and A10 being the current value corresponding to the minimum displacement of the variable pump. During wheel speed compensation control at or near the maximum speed, the control current A1 of the variable pump displacement control valve on the lower speed side increases from A30 or near A30, and the control current A1 of the variable pump displacement control valve on the higher speed side decreases from A30 or near A30.

7. The control method of hydrostatic bilateral drive according to claim 1, characterized in that: The motor is an electronically controlled variable displacement motor, and its displacement can be linearly and steplessly adjusted according to the speed difference V between the left and right wheels. differ While compensating the current of the left and right variable pump displacement control valves, the displacement of the electronically controlled variable motor can be proportionally controlled. When the left and right wheel speed difference V differ When the left wheel speed is positive, that is, the left wheel speed is greater than the right wheel speed, based on the above-mentioned left and right variable pump compensation control, the displacement of the left electronically controlled variable motor is controlled to increase, and the displacement of the right electronically controlled variable motor is controlled to decrease; when the left and right wheel speed difference V differ When it is negative, that is, the left wheel speed is less than the right wheel speed, on the basis of the above-mentioned left and right variable pump compensation control, the displacement of the left electronically controlled variable motor is controlled to decrease, and the displacement of the right electronically controlled variable motor is controlled to increase, so as to achieve a rapid reduction in the speed difference between the two sides of the wheel.

8. A hydrostatic bilateral drive control system, characterized by: It includes a vehicle controller, an engine controller, an engine, a left variable displacement pump, a left pump displacement control valve, a right variable displacement pump, a right pump displacement control valve, a shift control valve, a left hydraulic motor and a right hydraulic motor, a left motor displacement control valve, and a right motor displacement control valve; wherein the vehicle controller is connected to the engine controller; The output end of the vehicle controller is connected to the signal input ends of the left pump displacement control valve, the right pump displacement control valve and the shift control valve; The input shaft end of the left variable displacement pump is directly connected to the output shaft end of the engine, and the right variable displacement pump and the left variable displacement pump form a tandem pump; The two oil ports of the left variable displacement pump are directly connected to the two oil ports of the left hydraulic motor through pipelines, and the two oil ports of the right variable displacement pump are directly connected to the two oil ports of the right hydraulic motor through pipelines. The left and right hydraulic motors drive the left and right wheels of the vehicle respectively; The input end of the vehicle controller is also connected to the accelerator pedal signal, the walking handle signal and the shift button signal. The output end of the shift control valve is connected to the input ends of the left and right motor displacement control valves. The output shaft positions of the left hydraulic motor and the right hydraulic motor are both provided with speed sensors and connected to the input end of the vehicle controller.

9. A hydrostatic bilateral drive control system, characterized by: It includes a vehicle controller, an engine controller, an engine, a left variable pump, a left pump displacement control valve, a right variable pump, a right pump displacement control valve, a left electronically controlled variable motor and a right electronically controlled variable motor, a left motor displacement control valve, and a right motor displacement control valve; wherein, The vehicle controller is connected to the engine controller; The output end of the vehicle controller is connected to the signal input ends of the engine controller, the left pump displacement control valve, the right pump displacement control valve, the left electronically controlled variable motor displacement control valve and the right electronically controlled variable motor displacement control valve; The input shaft end of the left variable displacement pump is directly connected to the output shaft end of the engine, and the right variable displacement pump and the left variable displacement pump form a tandem pump; The two oil ports of the left variable displacement pump are directly connected to the two oil ports of the left electronically controlled variable displacement motor through pipelines, and the two oil ports of the right variable displacement pump are directly connected to the two oil ports of the right electronically controlled variable displacement motor through pipelines. The left and right electronically controlled variable displacement motors drive the left and right wheels of the vehicle respectively. The input end of the vehicle controller is also connected to the accelerator pedal signal, the travel handle signal and the shift button signal; The output shaft positions of the left electronically controlled variable motor and the right electronically controlled variable motor are both provided with speed sensors, and are connected to the input end of the vehicle controller.

10. A skid steer loader, characterized in that: The invention comprises the control system according to claim 8 or 9, wherein the control system is used to execute the control method according to any one of claims 1 to 7.

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