A loader steering wheel electro-hydraulic power steering control method, system and device

Abstract

The application discloses a loader steering wheel electro-hydraulic power-assisted steering control method, system and device. According to the speed of the loader and the steering angle of the loader, whether the loader is stationary or enters a steering limit position buffer area is determined, different control strategies are adopted to control the motor in different cases, and then the motor controls the hydraulic steering gear, so that the problems existing in the electro-hydraulic power-assisted steering can be effectively solved, and the driving safety and comfort can be improved.

Description

Technical Field

[0001] This invention relates to a method, system, and device for electro-hydraulic power steering control of a loader steering wheel, belonging to the field of loader steering technology. Background Technology

[0002] Currently, the steering of loaders is entirely driven by hydraulic power, which is mechanically driven by hydraulics. This type of hydraulic power steering has problems such as large steering start-up impact, poor steering smoothness, poor handling at different vehicle speeds, large steering torque, and large steering limit impact. As the market's requirements for the micro-controllability, control precision, starting comfort, rapid response, and safety of loader steering wheel are constantly increasing, the traditional hydraulic power steering control method can no longer meet market requirements. Summary of the Invention

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

[0004] According to one aspect of this disclosure, a method for controlling the electro-hydraulic power steering of a loader steering wheel is provided, comprising:

[0005] If the loader is stationary at the current moment, and it is determined from the current steering angle that the loader has not entered the steering limit buffer zone, then the motor is controlled according to the first control strategy based on the current steering wheel speed and torque. If it is determined from the current steering angle that the loader has entered the steering limit buffer zone, then the point where the loader enters the steering limit buffer zone is used as the control starting point, and the motor is controlled according to the second control strategy. Here, the motor is the motor that drives the hydraulic steering unit.

[0006] If the loader is not stationary at the current moment, and it is determined from the loader's current steering angle and speed that the loader has not entered the steering limit buffer zone, then the motor is controlled according to the third control strategy based on the loader's current speed, steering wheel speed and torque. If it is determined from the loader's current steering angle and speed that the loader has entered the steering limit buffer zone, then the point where the loader enters the steering limit buffer zone is used as the control starting point, and the motor is controlled according to the second control strategy.

[0007] In some embodiments of this disclosure, when the loader is stationary at the current moment, the process of determining whether the loader's steering has entered the steering limit buffer zone based on the loader's current steering angle is as follows:

[0008] Calculate the judgment coefficient based on the loader's current steering angle;

[0009] If the current controlling the speed of the motor is less than the judgment coefficient at the current moment, then the loader has not entered the steering limit buffer zone at the current moment.

[0010] If the current controlling the speed of the motor is not less than the judgment coefficient at the current moment, then the loader has entered the steering limit buffer zone at the current moment.

[0011] In some embodiments of this disclosure, when the loader is not stationary at the current moment, the process of determining whether the loader's steering has entered the steering limit buffer zone based on the loader's steering angle and speed at the current moment is as follows:

[0012] Calculate the judgment coefficient based on the loader's current steering angle and speed;

[0013] If the current controlling the speed of the motor is less than the judgment coefficient at the current moment, then the loader has not entered the steering limit buffer zone at the current moment.

[0014] If the current controlling the speed of the motor is not less than the judgment coefficient at the current moment, then the loader has entered the steering limit buffer zone at the current moment.

[0015] In some embodiments of this disclosure, the formula for calculating the determination coefficient is as follows:

[0016] m= l *Kp+△*Kd+b+V*Kv;

[0017] In the formula, m is the determination coefficient. l KP is the remaining distance from the current position of the loader's steering angle to the steering limit position. KP is the position coefficient, Δ is the steering distance per unit time, Kd is the steering speed coefficient, b is the minimum starting current of the motor, V is the loader's speed at the current moment (V is 0 when the loader is stationary), and Kv is the travel coefficient.

[0018] In some embodiments of this disclosure, the first control strategy is a linear control strategy, and the control formula is:

[0019] y = ax + b;

[0020] y = Acc × sp + lasty;

[0021] In the formula, y is the speed control current supplied to the motor at the current moment, a is the slope of the speed control current, b is the minimum current for motor startup, b is larger when the steering wheel torque is larger at the current moment, and b is smaller when the steering wheel torque is smaller at the current moment, 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 supplied to the motor at the previous moment, and sp is the control cycle.

[0022] In some embodiments of this disclosure, the second control strategy is a control strategy that decays in the form of a single parabola, as shown in the formula:

[0023] y=((y0-y1) / l 1 2 ) l 2 -(2(y0 -y1) / l 1) l +y0;

[0024] In the formula, y is the speed control current supplied to the motor at the current moment. l Let (y0, y0) be the remaining distance from the current position of the loader's steering angle to its steering limit, (y0, y0) be the coordinates of the control endpoint, and y0 be the speed control current corresponding to the control endpoint. l (1, y1) represents the coordinates of the control starting point, where y1 is the speed control current corresponding to the control starting point. l 1 represents the remaining distance corresponding to the control starting point.

[0025] In some embodiments of this disclosure, the third control strategy is a linear control strategy, and the control formula is:

[0026] y = ax + b;

[0027] y = Acc × sp + lasty;

[0028] In the formula, y is the speed control current supplied to the motor at the current moment, a is the slope of the generated speed control current, b is the minimum current for motor startup, b is larger when the steering wheel torque is larger at the current moment, and b is smaller when the steering wheel torque is smaller at the current moment, 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, ACC is smaller when the loader speed is smaller at the current moment, and ACC is larger when the loader speed is larger at the current moment, lasty is the speed control current supplied to the motor at the previous moment, and sp is the control cycle.

[0029] According to another aspect of this disclosure, a loader steering wheel electro-hydraulic power steering control system is provided, comprising:

[0030] The stationary control module, when the loader is stationary at the current moment, if it is determined from the current steering angle that the loader's steering has not entered the steering limit buffer zone, then the motor is controlled according to the first control strategy based on the current steering wheel speed and torque. If it is determined from the current steering angle that the loader's steering has entered the steering limit buffer zone, then the point where the loader enters the steering limit buffer zone is used as the control starting point, and the motor is controlled according to the second control strategy. Here, the motor is the motor that drives the hydraulic steering unit.

[0031] In the non-stationary control module, if the loader is not stationary at the current moment, and it is determined from the current loader's steering angle and speed that the loader's steering has not entered the steering limit buffer zone, then the motor is controlled according to the third control strategy based on the current loader's speed, steering wheel speed and torque. If it is determined from the current loader's steering angle and speed that the loader's steering has entered the steering limit buffer zone, then the point where the loader enters the steering limit buffer zone is used as the control starting point, and the motor is controlled according to the second control strategy.

[0032] According to another aspect of this disclosure, a loader steering wheel electro-hydraulic power steering control device is provided, 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.

[0033] The speed acquisition device and torque acquisition device respectively acquire the speed and torque of the steering wheel;

[0034] The steering angle acquisition device acquires the steering angle of the loader;

[0035] The vehicle speed data acquisition device collects the speed of the loader;

[0036] The electric motor drives the hydraulic steering gear, and the motor's control terminal is connected to the controller.

[0037] The controller uses the loader steering wheel electro-hydraulic power steering control method for steering control.

[0038] In some embodiments of this disclosure, the speed acquisition device and torque acquisition device are mounted on the steering column, the steering angle acquisition device is mounted at the hinge points of the front and rear frames of the loader, and the vehicle speed acquisition device is mounted on the loader's driveshaft or tire hub to acquire the speed of the driveshaft or tire hub and determine the vehicle speed based on the speed of the driveshaft or tire hub. The motor is mounted on the steering column.

[0039] The beneficial effects achieved by this invention are as follows: Based on the loader's speed and steering angle, this invention determines whether the loader is stationary or has entered the steering limit buffer zone. Different control strategies are adopted to control the motor in different situations, and then the motor controls the hydraulic steering gear. This can effectively solve the problems existing in hydraulic power steering and improve driving safety and comfort. Attached Figure Description

[0040] Figure 1 A flowchart of the electro-hydraulic power steering control method for a loader steering wheel;

[0041] Figure 2 A block diagram of the electro-hydraulic power steering control system for a loader steering wheel;

[0042] Figure 3A schematic diagram of the electro-hydraulic power steering control device for a loader steering wheel. Detailed Implementation

[0043] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this disclosure or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0044] Unless otherwise stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of this disclosure.

[0045] At the same time, it should be understood that, for ease of description, the dimensions of the various parts shown in the accompanying drawings are not drawn according to actual scale.

[0046] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0047] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0048] It should be noted that similar symbols and letters in the following figures represent similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0049] To address the problems of large steering start-up impact, poor steering smoothness, poor handling at different vehicle speeds, large steering torque, and large steering limit impact in hydraulic power steering, this disclosure proposes a method, system, and device for controlling electro-hydraulic power steering of a loader steering wheel. Specifically, based on the loader's speed and steering angle, it determines whether the loader is stationary or has entered the steering limit buffer zone. Different control strategies are used to control the motor in different situations, and then the motor controls the hydraulic steering gear. This effectively solves the problems of hydraulic power steering and improves driving safety and comfort.

[0050] See Figure 1 , Figure 1This is a flowchart illustrating a loader steering wheel electro-hydraulic power steering control method provided in an embodiment of this application. This loader steering wheel electro-hydraulic power steering control method can be executed by a controller in the loader. The controller in the loader can be an on-board steering controller, or it can be a separate motor controller. The loader steering wheel electro-hydraulic power steering control method can include at least the following steps:

[0051] Step 1: If the loader is stationary at the current moment, and it is determined from the current steering angle that the loader has not entered the steering limit buffer zone, then the motor is controlled according to the first control strategy based on the current steering wheel speed and torque. If it is determined from the current steering angle that the loader has entered the steering limit buffer zone, then the point where the loader enters the steering limit buffer zone is taken as the control starting point, and the motor is controlled according to the second control strategy. Here, the motor is the motor that drives the hydraulic steering gear.

[0052] It should be noted that in step 1, the loader's status is determined based on the data collected, i.e., whether it is stationary or not, and whether it has entered or not entered the steering limit buffer zone. The collected data mainly includes the steering wheel speed, the loader's steering angle, and the loader's speed.

[0053] The steering wheel rotation speed is the speed at which the driver turns the steering wheel. It includes not only the speed itself but also the direction of rotation; for example, clockwise rotation speed can be defined as positive, and counterclockwise rotation speed as negative. The loader's steering angle refers to the maximum deflection angle of the front wheels or steering wheels during driving or operation. The loader's vehicle speed is its travel speed, which can be further calculated from the rotation speed of the driveshaft or wheel hubs. Existing loaders already have built-in speed and steering angle data collection capabilities; therefore, additional data collection devices (such as sensors) are needed to collect the steering wheel rotation speed.

[0054] In step 1, whether the loader is stationary 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.

[0055] It should be noted that the steering limit buffer zone refers to the area between the left and right limit positions when the loader turns from the middle position to the left / 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 range of speed reduction when approaching the limit position is the steering limit buffer zone.

[0056] Since the vehicle speed is 0 when stationary, determining whether it has entered the steering limit buffer zone only requires considering the steering angle. The specific process is as follows: First, calculate the determination coefficient based on the loader's current steering angle. The formula is:

[0057] m=l *Kp+△*Kd+b;

[0058] In the formula, m is the determination coefficient. l KP is the remaining distance from the current position of the loader's steering angle to the steering limit position. KP is the position coefficient, Δ is the steering distance per unit time, Kd is the steering speed coefficient, and b is the minimum starting current of the motor.

[0059] If the current controlling the speed of the motor is less than the determination coefficient at the current moment, then the loader has not entered the steering limit buffer zone at the current moment; if the current controlling the speed of the motor is not less than the determination coefficient at the current moment, then the loader has entered the steering limit buffer zone at the current moment.

[0060] In some embodiments, the first control strategy may be a linear control strategy, and the control formula may be expressed as:

[0061] y = ax + b;

[0062] y = Acc × sp + lasty;

[0063] In the formula, y is the speed control current supplied to the motor at the current moment, a is the slope of the speed control current, b is the minimum starting current of the motor, b is larger when the steering wheel torque is larger at the current moment, and b is smaller when the steering wheel torque is smaller at the current moment (the correspondence between torque and b can be set according to the actual situation), 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 supplied to the motor at the previous moment, and sp is the control period; the first formula controls the generation of the speed control current, and the second formula controls the rate of change of the speed control current; simply put, taking 100A as an example, the first formula controls the generation of 100A of current, and the second formula controls the time to generate 100A.

[0064] The first control strategy can achieve slow response and high power assistance at low speeds, resulting in a comfortable and fast response.

[0065] The starting point of the second control strategy is the point where the steering limit buffer zone is entered, i.e., the current at which the current equals 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:

[0066] y=((y0-y1) / l 1 2 ) l 2 -(2(y0 -y1) / l 1) l +y0;

[0067] In the formula, y is the speed control current supplied to the motor at the current moment. l Let (y0, y0) be the remaining distance from the current position of the loader's steering angle to its steering limit, (y0, y0) be the coordinates of the control endpoint, and y0 be the speed control current corresponding to the control endpoint. l (1, y1) represents the coordinates of the control starting point, where y1 is the speed control current corresponding to the control starting point. l 1 represents the remaining distance corresponding to the control starting point.

[0068] The second control strategy can achieve a smooth transition in controlling the motor speed. As the remaining distance to the steering limit position continues to decrease, the current controlling the motor speed decreases smoothly, reducing the impact when steering to the limit position while ensuring steering speed.

[0069] return Figure 1 In step 2 of the embodiment, if the loader is not stationary at the current moment, and it is determined from the steering angle and speed of the loader at the current moment that the loader has not entered the steering limit buffer zone, then the motor is controlled according to the third control strategy based on the speed of the loader, the speed of the steering wheel and the torque at the current moment. If it is determined from the steering angle and speed of the loader at the current moment that the loader has entered the steering limit buffer zone, then the point where the loader enters the steering limit buffer zone is taken as the control starting point, and the motor is controlled according to the second control strategy.

[0070] Similar to step 1, the judgment in step 2 is also based on the data collected. In addition to the data in step 1, there is only one more data: the torque of the steering wheel. The torque of the steering wheel is the force when the driver operates the steering wheel. The greater the torque of the steering wheel, the greater the steering resistance encountered by the driver when turning. Similar to the speed measurement, the existing loaders do not have this function, so it is necessary to add an additional data collection device (such as a sensor) to collect the torque of the steering wheel.

[0071] Since the vehicle is not stationary and its speed is not zero, determining whether it has entered the steering limit buffer zone requires considering both the steering angle and the vehicle speed. The specific process is as follows: First, calculate the judgment coefficient based on the loader's current steering angle and speed. The formula is:

[0072] m= l *Kp+△*Kd+b+V*Kv;

[0073] In the formula, m is the determination coefficient. lKP is the remaining distance from the current position of the loader's steering angle to the steering limit position. KP is the position coefficient, Δ is the steering distance per unit time, Kd is the steering speed coefficient, b is the minimum current for motor startup, V is the loader's speed at the current moment, and Kv is the travel coefficient.

[0074] If the current controlling the speed of the motor is less than the determination coefficient at the current moment, then the loader has not entered the steering limit buffer zone at the current moment; if the current controlling the speed of the motor is not less than the determination coefficient at the current moment, then the loader has entered the steering limit buffer zone at the current moment.

[0075] In some embodiments, the third control strategy also employs a linear control strategy, and the control formula is:

[0076] y = ax + b;

[0077] y = Acc × sp + lasty;

[0078] In the formula, y is the speed control current supplied to the motor at the current moment, a is the slope of the speed control current, b is the minimum current for motor startup, b is larger when the steering wheel torque is larger at the current moment, and b is smaller when the steering wheel torque is smaller at the current moment (the correspondence between torque and b can be set according to the actual situation), 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, ACC is smaller when the loader speed is smaller at the current moment, and ACC is larger when the loader speed is larger at the current moment (the correspondence between speed and ACC can be set according to the actual situation), lasty is the speed control current supplied to the motor at the previous moment, and sp is the control cycle.

[0079] The third control strategy can be used to control the loader to turn at different speeds and corresponding steering rates.

[0080] It should be noted that, as can be seen from the above determination coefficient formula, with other coefficients remaining constant, the higher the vehicle speed, the larger the value of m. Furthermore, the non-stationary state differs from the stationary state. In the stationary state, with other coefficients remaining constant, the value of m is fixed, and therefore the point of entering the steering limit buffer zone is fixed. However, in the non-stationary state, m changes with vehicle speed, meaning that the point of entering the steering limit buffer zone also changes with vehicle speed. Therefore, in control, it is necessary to calculate m in real time based on vehicle speed to determine the point of entering the steering limit buffer zone in real time (that is, the control starting point is different at different times, and the corresponding starting point needs to be determined at each time). Then, the second control strategy is adopted for control.

[0081] The above method determines whether the loader is stationary or has entered the steering limit buffer zone based on the loader's speed and steering angle. Different control strategies are used to control the motor in different situations, and then the motor controls the hydraulic steering system. This can effectively solve the problems of hydraulic power steering and improve driving safety and comfort.

[0082] See Figure 2 , Figure 2 This is a block diagram of an electro-hydraulic power steering control system for a loader, provided in an embodiment of this application. This 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 an onboard steering controller, or it can be a separate motor controller. Figure 2 The system can include at least a static control module and a non-static control module, which, when used to execute the above-described loader steering wheel electro-hydraulic power steering control method, can:

[0083] In the static control module, if the loader is stationary at the current moment and it is determined from the current steering angle that the loader has not entered the steering limit buffer zone, then the motor is controlled according to the first control strategy based on the current steering wheel speed and torque. If it is determined from the current steering angle that the loader has entered the steering limit buffer zone, then the point where the loader enters the steering limit buffer zone is used as the control starting point, and the motor is controlled according to the second control strategy. The motor is the motor that drives the hydraulic steering unit.

[0084] In the non-stationary control module, if the loader is not stationary at the current moment, and it is determined from the current loader's steering angle and speed that the loader's steering has not entered the steering limit buffer zone, then the motor is controlled according to the third control strategy based on the current loader's speed, steering wheel speed and torque. If it is determined from the current loader's steering angle and speed that the loader's steering has entered the steering limit buffer zone, then the point where the loader enters the steering limit buffer zone is used as the control starting point, and the motor is controlled according to the second control strategy.

[0085] The system determines whether the loader is stationary or has entered the steering limit buffer zone based on the loader's speed and steering angle. Different control strategies are used to control the motor in different situations, and then the motor controls the hydraulic steering gear. This can effectively solve the problems of hydraulic power steering and improve driving safety and comfort.

[0086] See Figure 3 , Figure 3 This is a framework diagram of an electro-hydraulic power steering control device for a loader, provided in an embodiment of this application. This device is a hardware device that enables electro-hydraulic power steering. Figure 3The device includes at least a motor, a controller, a speed acquisition device, a torque acquisition device, a steering angle acquisition device, and a vehicle speed acquisition device.

[0087] The speed acquisition device and torque acquisition device acquire the speed and torque of the steering wheel, respectively. They can be equipped with speed sensors and torque sensors, which are directly mounted on the steering column connected to the steering wheel.

[0088] The steering angle acquisition device collects the steering angle of the loader. It can use a steering angle sensor and can be installed at the hinge points of the front and rear frames of the loader.

[0089] The vehicle speed acquisition device collects the speed of the loader. The vehicle speed acquisition device can be a speed sensor. The speed sensor collects the rotational speed of the drive shaft or the tire hub. The vehicle speed is determined by the rotational speed of the drive shaft or the tire hub. The speed sensor can be installed on the drive shaft or the tire hub of the loader.

[0090] The motor is directly mounted on the steering column. The motor's control end is connected to the controller, and the motor's drive end is connected to the intermediate shaft via a reduction gear. The intermediate shaft is connected to the hydraulic steering gear. The motor drives the reduction gear to rotate left and right, converting the speed into torque, which drives the intermediate shaft. The intermediate shaft then drives the hydraulic steering gear to rotate left and right. The hydraulic oil output from the hydraulic steering gear drives the left and right steering cylinders, thus achieving electro-hydraulic power steering for the loader.

[0091] The controller is either an additional controller or the steering controller that comes with the loader (see...). Figure 3 All sensor outputs are connected to the controller, which uses the loader steering wheel electro-hydraulic power steering control method for steering control, specifically controlling the motor. The controller is connected to the sensors and motor via CAN bus or hardwired connection to ensure stable signal transmission.

[0092] The controller of the aforementioned device receives the steering wheel speed, steering wheel torque, loader steering angle, and loader speed, and dynamically outputs control signals to control the motor. The motor drives the mechanical structure to drive the hydraulic system to generate steering assistance, realizing electro-hydraulic power steering, which can effectively improve the handling, comfort, and safety of the loader during driving and operation.

[0093] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for controlling the electro-hydraulic power steering of a loader steering wheel, characterized in that, include: If the loader is stationary at the current moment, and it is determined from the current steering angle that the loader has not entered the steering limit buffer zone, then the motor is controlled according to the first control strategy based on the current steering wheel speed and torque. If it is determined from the current steering angle that the loader has entered the steering limit buffer zone, then the point where the loader enters the steering limit buffer zone is used as the control starting point, and the motor is controlled according to the second control strategy. Here, the motor is the motor that drives the hydraulic steering unit. If the loader is not stationary at the current moment, and it is determined from the current loader's steering angle and speed that the loader has not entered the steering limit buffer zone, then the motor is controlled according to the third control strategy based on the current loader's speed, steering wheel speed and torque. If it is determined from the current loader's steering angle and speed that the loader has entered the steering limit buffer zone, then the point where the loader enters the steering limit buffer zone is taken as the control starting point, and the motor is controlled according to the second control strategy. When the loader is stationary at the current moment, the process of determining whether the loader's steering has entered the steering limit buffer zone based on the loader's steering angle at the current moment is as follows: Calculate the determination coefficient based on the loader's steering angle at the current moment; if the current controlling the speed in the motor at the current moment is less than the determination coefficient, then the loader's 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, then the loader's steering has entered the steering limit buffer zone at the current moment. When the loader is not stationary at the current moment, the process of determining whether the loader's steering has entered the steering limit buffer zone based on the loader's steering angle and speed at the current moment is as follows: Calculate the determination coefficient based on the loader's steering angle and speed at the current moment; if the current controlling the speed in the motor at the current moment is less than the determination coefficient, then the loader's 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, then the loader's steering has entered the steering limit buffer zone at the current moment. The formula for calculating the determination coefficient is as follows: m= l *Kp+△*Kd+b+V*Kv; In the formula, m is the determination coefficient. l KP is the remaining distance from the current position of the loader's steering angle to the steering limit position. KP is the position coefficient, Δ is the steering distance per unit time, Kd is the steering speed coefficient, b is the minimum starting current of the motor, V is the loader's speed at the current moment (V is 0 when the loader is stationary), and Kv is the travel coefficient.

2. 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; In the formula, y is the speed control current supplied to the motor at the current moment, a is the slope of the speed control current, b is larger when the steering wheel torque is larger at the current moment, and b is smaller when the steering wheel torque is smaller at the current moment, x is the speed of the steering wheel at the current moment, ACC is the slope of the speed control current, ACC is a fixed value when the loader is stationary, lasty is the speed control current supplied to the motor at the previous moment, and sp is the control period.

3. 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; In the formula, y is the speed control current supplied to the motor at the current moment, (0, y0) is the coordinate of the control endpoint, and y0 is the speed control current corresponding to the control endpoint. l (1, y1) represents the coordinates of the control starting point, where y1 is the speed control current corresponding to the control starting point. l 1 represents the remaining distance corresponding to the control starting point.

4. 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; In the formula, y is the speed control current supplied to the motor at the current moment, a is the slope of the speed control current, b is larger when the steering wheel torque is larger at the current moment, b is smaller when the steering wheel torque is smaller at the current moment, x is the speed of the steering wheel at the current moment, ACC is the slope of the speed control current, when the loader is stationary, ACC is smaller when the loader speed is smaller at the current moment, and larger when the loader speed is larger at the current moment, lasty is the speed control current supplied to the motor at the previous moment, and sp is the control period.

5. A loader steering wheel electro-hydraulic power steering control system, characterized in that, include: The stationary control module, when the loader is stationary at the current moment, if it is determined from the current steering angle that the loader's steering has not entered the steering limit buffer zone, then the motor is controlled according to the first control strategy based on the current steering wheel speed and torque. If it is determined from the current steering angle that the loader's steering has entered the steering limit buffer zone, then the point where the loader enters the steering limit buffer zone is used as the control starting point, and the motor is controlled according to the second control strategy. Here, the motor is the motor that drives the hydraulic steering unit. In the non-stationary control module, if the loader is not stationary at the current moment, and it is determined from the current loader's steering angle and speed that the loader's steering has not entered the steering limit buffer zone, then the motor is controlled according to the third control strategy based on the current loader's speed, steering wheel speed and torque. If it is determined from the current loader's steering angle and speed that the loader's steering has entered the steering limit buffer zone, then the point where the loader enters the steering limit buffer zone is used as the control starting point, and the motor is controlled according to the second control strategy. When the loader is stationary at the current moment, the process of determining whether the loader's steering has entered the steering limit buffer zone based on the loader's steering angle at the current moment is as follows: Calculate the determination coefficient based on the loader's steering angle at the current moment; if the current controlling the speed in the motor at the current moment is less than the determination coefficient, then the loader's 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, then the loader's steering has entered the steering limit buffer zone at the current moment. When the loader is not stationary at the current moment, the process of determining whether the loader's steering has entered the steering limit buffer zone based on the loader's steering angle and speed at the current moment is as follows: Calculate the determination coefficient based on the loader's steering angle and speed at the current moment; if the current controlling the speed in the motor at the current moment is less than the determination coefficient, then the loader's 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, then the loader's steering has entered the steering limit buffer zone at the current moment. The formula for calculating the determination coefficient is as follows: m= l *Kp+△*Kd+b+V*Kv; In the formula, m is the determination coefficient. l KP is the remaining distance from the current position of the loader's steering angle to the steering limit position. KP is the position coefficient, Δ is the steering distance per unit time, Kd is the steering speed coefficient, b is the minimum starting current of the motor, V is the loader's speed at the current moment (V is 0 when the loader is stationary), and Kv is the travel coefficient.

6. A loader steering wheel electro-hydraulic power steering control device, characterized in that, This includes a motor, controller, speed acquisition device, torque acquisition device, steering angle acquisition device, and vehicle speed acquisition device; The speed acquisition device and 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 data acquisition device collects the speed of the loader; The electric motor drives the hydraulic steering gear, and the motor's control terminal is connected to the controller. The controller performs steering control using the method described in any one of claims 1 to 4.

7. The apparatus according to claim 6, characterized in that, The speed acquisition device and torque acquisition device are installed on the steering column, the steering angle acquisition device is installed at the hinge point of the front and rear frames of the loader, and the vehicle speed acquisition device is installed on the drive shaft of the loader or at the tire hub to acquire the speed of the drive shaft or tire hub. The vehicle speed is determined by the speed of the drive shaft or tire hub. The motor is installed on the steering column.

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