Electro-hydraulic power-assisted steering control method, system and device for steering wheel of loading machine

Abstract

The invention discloses an electro-hydraulic power-assisted steering control method, system and device for a steering wheel of a loader, and the method comprises the steps: determining whether the loader is static and enters a steering limit buffer area or not according to the speed and steering angle of the loader, and controlling a motor by adopting different control strategies under different conditions, therefore, the hydraulic steering gear is controlled through the motor, the problems existing in hydraulic power-assisted steering can be effectively solved, and the driving safety and comfort can be improved.

Description

Technical Field

[0001] The invention relates to a method, system and device for controlling an electro-hydraulic power steering of a steering wheel of a loader, and belongs to the technical field of loader steering. Background Art

[0002] At present, the steering of loaders is completely hydraulically driven by mechanical driving hydraulics. This type of hydraulic power steering has problems such as large steering start-up impact, poor steering smoothness, poor controllability at different vehicle speeds, large steering torque, and large steering limit impact. As the market's requirements for the micro-controllability, control accuracy, starting comfort, rapid response, and safety of loader steering wheels continue to increase, the traditional hydraulic power steering control method can no longer meet market requirements. Summary of the invention

[0003] The invention provides a method, system and device for controlling an electro-hydraulic power steering of a steering wheel of a loader, which solve the problems disclosed in the background technology.

[0004] According to one aspect of the present disclosure, a method for controlling an electro-hydraulic power steering of a loader steering wheel is provided, comprising: When the loader is stationary at the current moment, if it is judged by the steering angle of the loader at the current moment that the steering of the loader at the current moment has not entered the steering limit buffer zone, then the motor is controlled according to the first control strategy based on the speed and torque of the steering wheel at the current moment; if it is judged by the steering angle of the loader at the current moment that the steering of the loader at the current moment has entered the steering limit buffer zone, then the point of entering the steering limit buffer zone is used as the control starting point, and the motor is controlled according to the second control strategy; wherein the motor is a motor for driving a hydraulic steering gear; When the loader is not stationary at the current moment, if it is judged by the steering angle and vehicle speed of the loader at the current moment that the steering of the loader has not entered the steering limit buffer zone, then the motor is controlled according to the third control strategy based on the vehicle speed, steering wheel speed and torque of the loader at the current moment. If it is judged by the steering angle and vehicle speed of the loader at the current moment that the steering of the loader has entered the steering limit buffer zone, then the point of entering the steering limit buffer zone is used as the control starting point, and the motor is controlled according to the second control strategy.

[0005] In some embodiments of the present disclosure, when the loader is stationary at the current moment, the process of determining whether the loader steering at the current moment enters the steering limit buffer zone according to the steering angle of the loader at the current moment is as follows: Calculate the determination coefficient according to the steering angle of the loader at the current moment; If the current controlling the rotation speed in the motor at the current moment is less than the determination coefficient, the loader steering has not entered the steering limit buffer at the current moment; If the current controlling the rotation speed in the motor at the current moment is not less than the determination coefficient, the loader steering enters the steering limit buffer zone at the current moment.

[0006] In some embodiments of the present disclosure, when the loader is not stationary at the current moment, the process of determining whether the loader steering enters the steering limit buffer zone at the current moment according to the steering angle and vehicle speed of the loader at the current moment is as follows: Calculate the determination coefficient according to the steering angle and vehicle speed of the loader at the current moment; If the current controlling the rotation speed in the motor at the current moment is less than the determination coefficient, the loader steering has not entered the steering limit buffer at the current moment; If the current controlling the rotation speed in the motor at the current moment is not less than the determination coefficient, the loader steering enters the steering limit buffer zone at the current moment.

[0007] In some embodiments of the present disclosure, the formula for calculating the determination coefficient is: m= l *Kp+△*Kd+b+V*Kv; In the formula, m is the determination coefficient, l is the remaining distance from the position corresponding to the steering angle of the loader at the current moment to the steering limit position, KP is the position coefficient, △ is the steering distance per unit time, Kd is the steering speed coefficient, b is the minimum current for motor starting, V is the speed of the loader at the current moment, V is 0 when the loader is stationary, and Kv is the driving coefficient.

[0008] In some embodiments of the present disclosure, the first control strategy is a linear control strategy, and the control formula is: y=ax+b; y=Acc×sp+lasty; Wherein, y is the speed control current delivered to the motor at the current moment, a is the slope of the speed control current, b is the minimum current for motor startup, the greater the steering wheel torque at the current moment, the greater b is, the smaller the steering wheel torque at the current moment, the smaller b is, x is the steering wheel speed at the current moment, ACC is the slope of the speed control current change, ACC is a fixed value when the loader is stationary, lasty is the speed control current delivered to the motor at the previous moment, and sp is the control period.

[0009] In some embodiments of the present disclosure, the second control strategy is a control strategy that decays in the form of a single parabola, and the formula is: y=((y0-y1 ) / l 1 2 ) l 2 -(2(y0 -y1 ) / l 1) l +y0; Where y is the speed control current delivered to the motor at the current moment, l is the remaining distance from the current moment when the loader steering angle corresponds to the position to the steering limit position, (0,y0) is the control end point coordinate, y0 is the speed control current corresponding to the control end point, ( l 1, y1) is the coordinate of the control starting point, y1 is the speed control current corresponding to the control starting point, l 1 is the remaining distance corresponding to the control starting point.

[0010] In some embodiments of the present disclosure, the third control strategy is a linear control strategy, and the control formula is: y=ax+b; y=Acc×sp+lasty; Wherein, y is the speed control current delivered to the motor at the current moment, a is the slope of the speed control current, b is the minimum current for motor startup, the greater the steering wheel torque at the current moment, the greater b is, the smaller the steering wheel torque at the current moment, the smaller b is, x is the steering wheel speed at the current moment, ACC is the slope of the speed control current change, when the loader is stationary, the smaller the loader speed at the current moment, the smaller ACC is, the greater the loader speed at the current moment, the greater ACC is, lasty is the speed control current delivered to the motor at the previous moment, sp is the control period.

[0011] According to another aspect of the present disclosure, a loader steering wheel electro-hydraulic power steering control system is provided, comprising: A stationary control module, when the loader is stationary at the current moment, if it is judged by the steering angle of the loader at the current moment that the steering of the loader has not entered the steering limit buffer zone at the current moment, then the motor is controlled according to the first control strategy based on the speed and torque of the steering wheel at the current moment; if it is judged by the steering angle of the loader at the current moment that the steering of the loader has entered the steering limit buffer zone at the current moment, then the point of entering the steering limit buffer zone is used as the control starting point, and the motor is controlled according to the second control strategy; wherein the motor is a motor for driving a hydraulic steering gear; A non-stationary control module, when the loader is not stationary at the current moment, if it is judged by the steering angle and vehicle speed of the loader at the current moment that the steering of the loader has not entered the steering limit buffer zone at the current moment, then the motor is controlled according to the vehicle speed, steering wheel speed and torque of the loader at the current moment according to the third control strategy; if it is judged by the steering angle and vehicle speed of the loader at the current moment that the steering of the loader has entered the steering limit buffer zone at the current moment, then the point of entering the steering limit buffer zone is used as the control starting point, and the motor is controlled according to the second control strategy.

[0012] According to another aspect of the present disclosure, there is provided a loader steering wheel electro-hydraulic power steering control device, characterized in that it includes a motor, a controller, a speed acquisition device, a torque acquisition device, a steering angle acquisition device and a vehicle speed acquisition device; The speed acquisition device and the torque acquisition device respectively acquire the speed and torque of the steering wheel; The steering angle acquisition device acquires the steering angle of the loader; The vehicle speed collecting device collects the vehicle speed of the loader; The motor drives the hydraulic steering gear, and the control end of the motor is connected to the controller; The controller adopts the loader steering wheel electro-hydraulic power steering control method to perform steering control.

[0013] In some embodiments of the present disclosure, the speed acquisition device and the torque acquisition device are installed on the steering column, the steering angle acquisition device is installed at the hinge points of the front and rear frames of the loader, the vehicle speed acquisition device is installed on the loader drive shaft or tire hub, the speed of the drive shaft or tire hub is collected, and the vehicle speed is determined by the speed of the drive shaft or tire hub, and the motor is installed on the steering column. .

[0014] The beneficial effects achieved by the present invention are as follows: the present invention determines whether the loader is stationary or has entered the steering limit buffer zone according to the vehicle speed and the steering angle of the loader, and adopts different control strategies to control the motor in different situations, and then controls the hydraulic steering gear through the motor, which can effectively solve the problems existing in the hydraulic power steering and improve driving safety and comfort. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The flowchart of the electro-hydraulic power steering control method for the steering wheel of a loader; Figure 2 This is the block diagram of the electro-hydraulic power steering control system for the loader steering wheel; Figure 3 This is the framework diagram of the loader steering wheel electro-hydraulic power steering control device. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. It is obvious that the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present disclosure and its application or use. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present disclosure.

[0017] Unless otherwise specified, the relative arrangement of components and steps, the numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present disclosure.

[0018] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0019] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0020] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0021] It should be noted that similar symbols and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it does not require further discussion in subsequent figures.

[0022] In order to solve the problems of hydraulic power steering, such as large steering start-up impact, poor steering smoothness, poor controllability at different vehicle speeds, large steering torque, large steering limit impact, etc., the present invention discloses a loader steering wheel electro-hydraulic power steering control method, system and device, which determine whether the loader is stationary and whether it has entered the steering limit buffer zone according to the vehicle speed and the steering angle of the loader, and adopt different control strategies to control the motor in different situations, and then control the hydraulic steering gear through the motor, which can effectively solve the problems existing in hydraulic power steering and improve driving safety and comfort.

[0023] See also Figure 1 , Figure 1 The present invention is a flowchart of a method for controlling a steering wheel electro-hydraulic power steering of a loader provided in an embodiment of the present invention. The method for controlling a steering wheel electro-hydraulic power steering of a loader can be executed by a controller in the loader. The controller in the loader can be a vehicle-mounted steering controller. Of course, a motor controller can also be separately provided. The method for controlling a steering wheel electro-hydraulic power steering of a loader can at least include the following steps: Step 1, when the loader is stationary at the current moment, if it is judged by the steering angle of the loader at the current moment that the steering of the loader at the current moment has not entered the steering limit buffer zone, then the motor is controlled according to the first control strategy based on the speed and torque of the steering wheel at the current moment; if it is judged by the steering angle of the loader at the current moment that the steering of the loader at the current moment has entered the steering limit buffer zone, then the point of entering the steering limit buffer zone is used as the control starting point, and the motor is controlled according to the second control strategy; wherein the motor is a motor for driving a hydraulic steering gear.

[0024] It should be noted that in step 1, the state of the loader is judged based on the collected data, i.e., stationary / non-stationary, entering the steering limit buffer zone / not entering the steering limit buffer zone. The collected data mainly includes the steering wheel speed, the steering angle of the loader and the vehicle speed of the loader.

[0025] The speed of the steering wheel is the speed at which the driver turns the steering wheel. It includes not only the value of the speed itself, but also the corresponding direction of rotation. For example, the speed of clockwise rotation can be defined as positive, and the speed of counterclockwise rotation can be defined as negative. The steering angle of the loader refers to the maximum deflection angle of the front wheel or steering wheel during the driving or operation of the loader. The speed of the loader is the driving speed of the loader, which can be further calculated by the speed of the drive shaft or tire hub. The existing loaders themselves have the function of collecting vehicle speed and steering angle, so additional collection devices (such as sensors) are required to collect the steering wheel speed.

[0026] In step 1, it is determined whether the loader is stationary, which can be determined directly from the vehicle speed. That is, when the vehicle speed is 0, it means that the loader is stationary, and when it is not 0, it means that the loader is not stationary.

[0027] It should be noted that the steering limit buffer zone refers to the area where the loader turns from the middle position to the left limit position / right limit position. In order to reduce the impact when turning to the limit position, the steering speed needs to be reduced when approaching the limit position. The interval where the speed is reduced when approaching the limit position is the steering limit buffer zone.

[0028] Since the vehicle speed is 0 when stationary, the steering angle is the only factor to determine whether the vehicle has entered the steering limit buffer zone. The specific process is as follows: first, the determination coefficient is calculated based on the steering angle of the loader at the current moment. The formula can be: m= l *Kp+△*Kd+b; In the formula, m is the determination coefficient, l is the remaining distance from the position corresponding to the steering angle of the loader at the current moment to the steering limit position, KP is the position coefficient, △ is the steering distance per unit time, Kd is the steering speed coefficient, and b is the minimum current for motor starting.

[0029] If the current controlling the speed in the motor at the current moment is less than the determination coefficient, the loader steering has not entered the steering limit buffer zone at the current moment; if the current controlling the speed in the motor at the current moment is not less than the determination coefficient, the loader steering has entered the steering limit buffer zone at the current moment.

[0030] In some embodiments, the first control strategy may adopt a linear control strategy, and the control formula may be expressed as: y=ax+b; y=Acc×sp+lasty; Wherein, y is the speed control current delivered to the motor at the current moment, a is the slope of the speed control current, b is the minimum current for motor startup, the greater the torque of the steering wheel at the current moment, the greater b is, and the smaller the torque of the steering wheel at the current moment, the smaller b is (the corresponding relationship between torque and b can be set according to actual conditions), x is the speed of the steering wheel at the current moment, ACC is the slope of the speed control current change, ACC is a fixed value when the loader is stationary, lasty is the speed control current delivered to the motor at the previous moment, sp is the control period; among them, the former formula controls the speed control current generation, and the latter formula controls the rate of change of the speed control current; to put it simply, taking 100A as an example, the first formula controls the current generation of 100A, and the latter formula controls the time to generate 100A.

[0031] The first control strategy can achieve slow response and large assistance at low vehicle speeds, and can achieve comfortable and fast response.

[0032] The starting point of the second control strategy is the point entering the steering limit buffer, that is, the current equal to m and the corresponding steering wheel speed are taken as the starting point. In some embodiments, the second control strategy is a control strategy that decays in the form of a single parabola, and the control formula can be expressed as: y=((y0-y1 ) / l 1 2 ) l 2 -(2(y0 -y1 ) / l 1) l +y0; Where y is the speed control current delivered to the motor at the current moment, l is the remaining distance from the current moment when the loader steering angle corresponds to the position to the steering limit position, (0,y0) is the control end point coordinate, y0 is the speed control current corresponding to the control end point, ( l 1, y1) is the coordinate of the control starting point, y1 is the speed control current corresponding to the control starting point, l 1 is the remaining distance corresponding to the control starting point.

[0033] The second control strategy can achieve a smooth transition of the motor speed control. As the remaining distance to the steering limit continues to decrease, the current controlling the motor speed decays smoothly, reducing the impact when steering to the limit while ensuring the steering speed.

[0034] return Figure 1In step 2 of the embodiment, when the loader is not stationary at the current moment, if it is judged by the steering angle and vehicle speed of the loader at the current moment that the steering of the loader has not entered the steering limit buffer zone at the current moment, then the motor is controlled according to the vehicle speed, steering wheel speed and torque of the loader at the current moment according to the third control strategy; if it is judged by the steering angle and vehicle speed of the loader at the current moment that the steering of the loader has entered the steering limit buffer zone at the current moment, then the point of entering the steering limit buffer zone is used as the control starting point, and the motor is controlled according to the second control strategy.

[0035] Similar to step 1, the judgment in step 2 is also based on the collected data. In addition to the data in step 1, there is only one more steering wheel torque. The steering wheel torque is the torque when the driver operates the steering wheel to turn. The greater the steering wheel torque, the greater the steering resistance encountered by the driver during the current steering. Similar to collecting the rotational speed, the existing loader itself does not have this function, so an additional collection device (such as a sensor) is also required to collect the steering wheel torque.

[0036] Since the vehicle is not stationary and the vehicle speed is not 0, the judgment of whether to enter the steering limit buffer zone should not only consider the steering angle but also the vehicle speed. The specific process can be: first, according to the steering angle and speed of the loader at the current moment, calculate the determination coefficient. The formula can be: m= l *Kp+△*Kd+b+V*Kv; In the formula, m is the determination coefficient, l is the remaining distance from the current moment's corresponding position of the loader's steering angle to the steering limit position, KP is the position coefficient, △ is the steering distance per unit time, Kd is the steering speed coefficient, b is the minimum current for motor starting, V is the current moment's loader speed, and Kv is the driving coefficient.

[0037] If the current controlling the speed in the motor at the current moment is less than the determination coefficient, the loader steering has not entered the steering limit buffer zone at the current moment; if the current controlling the speed in the motor at the current moment is not less than the determination coefficient, the loader steering has entered the steering limit buffer zone at the current moment.

[0038] In some embodiments, the third control strategy also adopts a linear control strategy, and the control formula is: y=ax+b; y=Acc×sp+lasty; Wherein, y is the speed control current delivered to the motor at the current moment, a is the slope of the speed control current, b is the minimum current for motor startup, the greater the torque of the steering wheel at the current moment, the greater b is, and the smaller the torque of the steering wheel at the current moment, the smaller b is (the corresponding relationship between torque and b can be set according to actual conditions), x is the speed of the steering wheel at the current moment, ACC is the slope of the speed control current change, when the loader is stationary, the smaller the speed of the loader at the current moment, the smaller ACC is, and the greater the speed of the loader at the current moment, the greater ACC is (the corresponding relationship between speed and ACC can be set according to actual conditions), lasty is the speed control current delivered to the motor at the previous moment, and sp is the control period.

[0039] The third control strategy can be used to achieve different steering rates when controlling the loader to turn at different vehicle speeds.

[0040] It should be noted that, from the above determination coefficient formula, it can be seen that, when the other coefficients remain unchanged, the greater the vehicle speed, the greater the m value; and the non-stationary state is different from the stationary state. In the stationary state, when the other coefficients remain unchanged, the m value is fixed, and thus the point of entering the steering limit buffer zone is fixed, while in the non-stationary state, m changes with the vehicle speed, that is, the point of entering the steering limit buffer zone also changes with the vehicle speed. Therefore, in control, it is necessary to calculate m in real time through the vehicle speed, so as to determine the point of entering the steering limit buffer zone in real time (that is, the control starting point at different moments is different, and the corresponding starting point needs to be determined at each moment), and then adopt the second control strategy for control.

[0041] The above method determines whether the loader is stationary or has entered the steering limit buffer zone according to the vehicle speed and the steering angle of the loader, and adopts different control strategies to control the motor in different situations. Then, the hydraulic steering gear is controlled by the motor, which can effectively solve the problems existing in the hydraulic power steering and improve driving safety and comfort.

[0042] See also Figure 2 , Figure 2 : is a block diagram of a loader steering wheel electro-hydraulic power steering control system provided in an embodiment of the present application. The system is a virtual system, i.e., software, which can be loaded and executed by a controller in the loader. The controller in the loader can be a vehicle-mounted steering controller, and of course, a separate motor controller can also be provided. Figure 2 The system may include at least a stationary control module and a non-stationary control module, which, when used to execute the above-mentioned loader steering wheel electro-hydraulic power steering control method, can: A stationary control module, when the loader is stationary at the current moment, if it is judged by the steering angle of the loader at the current moment that the steering of the loader has not entered the steering limit buffer zone at the current moment, then the motor is controlled according to the first control strategy based on the speed and torque of the steering wheel at the current moment; if it is judged by the steering angle of the loader at the current moment that the steering of the loader has entered the steering limit buffer zone at the current moment, then the point of entering the steering limit buffer zone is used as the control starting point, and the motor is controlled according to the second control strategy; wherein the motor is a motor for driving a hydraulic steering gear.

[0043] A non-stationary control module, when the loader is not stationary at the current moment, if it is judged by the steering angle and vehicle speed of the loader at the current moment that the steering of the loader has not entered the steering limit buffer zone at the current moment, then the motor is controlled according to the vehicle speed, steering wheel speed and torque of the loader at the current moment according to the third control strategy; if it is judged by the steering angle and vehicle speed of the loader at the current moment that the steering of the loader has entered the steering limit buffer zone at the current moment, then the point of entering the steering limit buffer zone is used as the control starting point, and the motor is controlled according to the second control strategy.

[0044] The above system determines whether the loader is stationary or has entered the steering limit buffer zone according to the loader's speed and steering angle, and adopts different control strategies to control the motor in different situations. The hydraulic steering gear is then controlled by the motor, which can effectively solve the problems existing in hydraulic power steering and improve driving safety and comfort.

[0045] See also Figure 3 , Figure 3 This is a framework diagram of a loader steering wheel electro-hydraulic power steering control device provided in an embodiment of the present application. The device is a hardware device that can realize the steering wheel electro-hydraulic power steering. Figure 3 The device at least includes a motor, a controller, a speed acquisition device, a torque acquisition device, a steering angle acquisition device and a vehicle speed acquisition device.

[0046] The speed acquisition device and the torque acquisition device respectively acquire the speed and torque of the steering wheel, and can respectively adopt a speed sensor and a torque sensor, which are directly mounted on the steering column connected to the steering wheel.

[0047] The steering angle acquisition device acquires the steering angle of the loader and may adopt a steering angle sensor which may be installed at the hinge points of the front and rear frames of the loader.

[0048] The vehicle speed collection device collects the vehicle speed of the loader. The vehicle speed collection device can be used as a speed sensor. The speed sensor collects the speed of the drive shaft or the tire hub, and the vehicle speed is determined by the speed of the drive shaft or the tire hub. The speed sensor can be installed on the loader drive shaft or the tire hub.

[0049] The motor is directly fixed on the steering column. The control end of the motor is connected to the controller. The drive end of the motor is connected to the intermediate shaft through the reduction gear, and the intermediate shaft is connected to the hydraulic steering gear. The motor drives the reduction gear to rotate left and right. The reduction gear converts the speed into torque to drive the intermediate shaft. The intermediate shaft drives the hydraulic steering gear to rotate left and right. The hydraulic oil flow output by the hydraulic steering gear drives the left and right steering cylinders to move, thereby realizing the left and right electro-hydraulic power steering of the loader.

[0050] The controller is an additional controller or a steering controller that comes with the loader (see Figure 3 ), the output ends of all sensors are connected to the controller. The controller adopts the loader steering wheel electro-hydraulic power steering control method for steering control, specifically controlling the motor. The controller is connected to the sensor and motor through the CAN bus or hard wiring to ensure the stability of signal transmission.

[0051] The controller of the above-mentioned device receives the steering wheel speed, steering wheel torque, steering angle of the loader and vehicle speed of the loader, dynamically outputs the control signal of the control motor, controls the operation of the motor, and the motor drives the mechanical structure to drive the hydraulic system to form steering assistance, thereby realizing electro-hydraulic power steering of the steering wheel, which can effectively improve the controllability, comfort and safety of the loader during driving and operation.

[0052] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A loader steering wheel electro-hydraulic power steering control method, characterized in that: include: When the loader is stationary at the current moment, if it is judged by the steering angle of the loader at the current moment that the steering of the loader at the current moment has not entered the steering limit buffer zone, then the motor is controlled according to the first control strategy based on the speed and torque of the steering wheel at the current moment; if it is judged by the steering angle of the loader at the current moment that the steering of the loader at the current moment has entered the steering limit buffer zone, then the point of entering the steering limit buffer zone is used as the control starting point, and the motor is controlled according to the second control strategy; wherein the motor is a motor for driving a hydraulic steering gear; When the loader is not stationary at the current moment, if it is judged by the steering angle and vehicle speed of the loader at the current moment that the steering of the loader has not entered the steering limit buffer zone, then the motor is controlled according to the third control strategy based on the vehicle speed, steering wheel speed and torque of the loader at the current moment. If it is judged by the steering angle and vehicle speed of the loader at the current moment that the steering of the loader has entered the steering limit buffer zone, then the point of entering the steering limit buffer zone is used as the control starting point, and the motor is controlled according to the second control strategy.

2. The method according to claim 1, characterized in that When the loader is stationary at the current moment, the process of judging whether the loader's steering enters the steering limit buffer zone at the current moment according to the steering angle of the loader at the current moment is as follows: Calculate the determination coefficient according to the steering angle of the loader at the current moment; If the current controlling the rotation speed in the motor at the current moment is less than the determination coefficient, the loader steering has not entered the steering limit buffer at the current moment; If the current controlling the rotation speed in the motor at the current moment is not less than the determination coefficient, the loader steering enters the steering limit buffer zone at the current moment.

3. The method according to claim 1, characterized in that When the loader is not stationary at the current moment, the process of judging whether the loader's steering enters the steering limit buffer zone at the current moment is as follows according to the steering angle and speed of the loader at the current moment: Calculate the determination coefficient according to the steering angle and vehicle speed of the loader at the current moment; If the current controlling the rotation speed in the motor at the current moment is less than the determination coefficient, the loader steering has not entered the steering limit buffer at the current moment; If the current controlling the rotation speed in the motor at the current moment is not less than the determination coefficient, the loader steering enters the steering limit buffer zone at the current moment.

4. The method according to claim 2 or 3, characterized in that: The formula for calculating the coefficient of determination is: m= l *Kp+△*Kd+b+V*Kv; In the formula, m is the determination coefficient, l is the remaining distance from the position corresponding to the steering angle of the loader at the current moment to the steering limit position, KP is the position coefficient, △ is the steering distance per unit time, Kd is the steering speed coefficient, b is the minimum current for motor starting, V is the speed of the loader at the current moment, V is 0 when the loader is stationary, and Kv is the driving coefficient.

5. The method according to claim 1, characterized in that The first control strategy is a linear control strategy, and the control formula is: y=ax+b; y=Acc×sp+lasty; Wherein, y is the speed control current delivered to the motor at the current moment, a is the slope of the speed control current, b is the minimum current for motor startup, the greater the steering wheel torque at the current moment, the greater b is, the smaller the steering wheel torque at the current moment, the smaller b is, x is the steering wheel speed at the current moment, ACC is the slope of the speed control current change, ACC is a fixed value when the loader is stationary, lasty is the speed control current delivered to the motor at the previous moment, and sp is the control period.

6. The method according to claim 1, characterized in that The second control strategy is a control strategy that decays in the form of a single parabola, and the formula is: y=((y0-y1 ) / l 1 2 ) l 2 -(2(y0 -y1 ) / l 1) l +y0; Where y is the speed control current delivered to the motor at the current moment, l is the remaining distance from the current moment when the loader steering angle corresponds to the position to the steering limit position, (0,y0) is the control end point coordinate, y0 is the speed control current corresponding to the control end point, ( l 1, y1) is the coordinate of the control starting point, y1 is the speed control current corresponding to the control starting point, l 1 is the remaining distance corresponding to the control starting point.

7. The method according to claim 1, characterized in that The third control strategy is a linear control strategy, and the control formula is: y=ax+b; y=Acc×sp+lasty; Wherein, y is the speed control current delivered to the motor at the current moment, a is the slope of the speed control current, b is the minimum current for motor startup, the greater the steering wheel torque at the current moment, the greater b is, the smaller the steering wheel torque at the current moment, the smaller b is, x is the steering wheel speed at the current moment, ACC is the slope of the speed control current change, when the loader is stationary, the smaller the loader speed at the current moment, the smaller ACC is, the greater the loader speed at the current moment, the greater ACC is, lasty is the speed control current delivered to the motor at the previous moment, sp is the control period.

8. A loader steering wheel electro-hydraulic power steering control system, characterized in that: include: A stationary control module, when the loader is stationary at the current moment, if it is judged by the steering angle of the loader at the current moment that the steering of the loader has not entered the steering limit buffer zone at the current moment, then the motor is controlled according to the first control strategy based on the speed and torque of the steering wheel at the current moment; if it is judged by the steering angle of the loader at the current moment that the steering of the loader has entered the steering limit buffer zone at the current moment, then the point of entering the steering limit buffer zone is used as the control starting point, and the motor is controlled according to the second control strategy; wherein the motor is a motor for driving a hydraulic steering gear; A non-stationary control module, when the loader is not stationary at the current moment, if it is judged by the steering angle and vehicle speed of the loader at the current moment that the steering of the loader has not entered the steering limit buffer zone at the current moment, then the motor is controlled according to the vehicle speed, steering wheel speed and torque of the loader at the current moment according to the third control strategy; if it is judged by the steering angle and vehicle speed of the loader at the current moment that the steering of the loader has entered the steering limit buffer zone at the current moment, then the point of entering the steering limit buffer zone is used as the control starting point, and the motor is controlled according to the second control strategy.

9. A loader steering wheel electro-hydraulic power steering control device, characterized in that: It includes a motor, a controller, a speed acquisition device, a torque acquisition device, a steering angle acquisition device and a vehicle speed acquisition device; The speed acquisition device and the torque acquisition device respectively acquire the speed and torque of the steering wheel; The steering angle acquisition device acquires the steering angle of the loader; The vehicle speed collecting device collects the vehicle speed of the loader; The motor drives the hydraulic steering gear, and the control end of the motor is connected to the controller; The controller adopts the method described in any one of claims 1 to 7 to perform steering control.

10. The device according to claim 9, characterized in that The speed collection device and the torque collection device are installed on the steering column, the steering angle collection device is installed at the hinge points of the front and rear frames of the loader, the vehicle speed collection device is installed on the loader drive shaft or tire hub, collects the speed of the drive shaft or tire hub, and determines the vehicle speed through the speed of the drive shaft or tire hub. The motor is installed on the steering column.

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