Steering control system, method and vehicle for a full hydraulic steering system of an unmanned vehicle

Abstract

The application discloses a steering control system, a method and a vehicle of a full hydraulic steering system of an unmanned vehicle, and belongs to the technical field of intelligent driving. A first feedforward controller in the steering control system applies a first feedforward amount consistent with the direction of a current target steering angle request or a current target steering angle request trend to the full hydraulic steering system when the current target steering angle request or the direction of the current target steering angle request trend is switched, and the size of the first feedforward amount is related to the size of the current target steering angle request; a second feedforward controller applies a second feedforward amount when the absolute value of the difference between the current target steering angle and the actual steering angle fed back by a steering angle sensor is greater than a setting coefficient; and a response speed controller operates the difference and applies a control amount corresponding to the operation result, so as to improve the response speed of the full hydraulic steering system together with the second feedforward controller. The application can improve the response speed, the adjustment accuracy, the adjustment speed, the static response characteristic and the dynamic response characteristic of steering switching.

Description

Technical Field

[0001] This application relates to the field of intelligent driving technology, and in particular to a steering control system, method and vehicle for a fully hydraulic steering system of an unmanned vehicle. Background Technology

[0002] Currently, autonomous driving has six main application scenarios in the commercial vehicle sector, including mining areas, ports, logistics parks, airports, long-haul logistics, and last-mile logistics. In mining areas, with increasing mining demands and the continuous increase in the tonnage of mining trucks, electric power steering can no longer meet the steering force requirements, necessitating the use of hydraulic power steering. A fully hydraulic steering system, consisting of a fully hydraulic steering gear, hydraulic pump, and hydraulic cylinders, is used to achieve power steering. However, compared to electric power steering, the fully hydraulic steering system suffers from significant response lag and slow reaction time when performing steering control in autonomous driving.

[0003] For autonomous driving, steer-by-wire is particularly important. Autonomous driving systems need to assess the vehicle's deviation from the expected trajectory in real time and make lateral corrections. However, fully hydraulic steering suffers from significant response lag and slow reaction, resulting in slow lateral correction speeds and excessive deviations during operation. This severely impacts the lateral control accuracy of autonomous driving and poses safety hazards. Therefore, by using control technology to make the response time and reaction speed of the fully hydraulic steering system approach the performance of electric power steering, it is more conducive to the implementation of autonomous driving technology in mining environments. Summary of the Invention

[0004] This application provides a steering control system, method, and vehicle for a fully hydraulic steering system in an unmanned vehicle, to solve the problems of response lag and slow reaction in fully hydraulic steering systems. The technical solution is as follows:

[0005] On the one hand, a steering control system for a fully hydraulic steering system of an unmanned vehicle is provided, the steering control system including a first feedforward controller, a second feedforward controller, a response speed controller and a steering angle sensor;

[0006] The input terminals of the first feedforward controller, the second feedforward controller, the response speed controller, and the output terminal of the steering angle sensor are connected together to serve as the input terminal of the steering control system, which is then connected to the output terminal of the autonomous driving system.

[0007] The output terminals of the first feedforward controller, the second feedforward controller, and the response speed controller are connected together to serve as the output terminal of the steering control system, and the output terminal of the steering control system is connected to the input terminal of the full hydraulic steering system.

[0008] The input terminal of the steering angle sensor is connected to the wheel or steering wheel, and the wheel or steering wheel is connected to the fully hydraulic steering system;

[0009] The first feedforward controller is configured to apply a first feedforward amount in the direction of the current target steering angle request or the current target steering angle request trend switching direction to the fully hydraulic steering system when the current target steering angle request or the current target steering angle request trend switching direction is detected by the autonomous driving system, wherein the magnitude of the first feedforward amount is related to the magnitude of the current target steering angle request;

[0010] The second feedforward controller is configured to apply a second feedforward amount to the fully hydraulic steering system when the absolute value of the difference between the current target steering angle request and the actual steering angle fed back by the steering angle sensor is greater than the setting coefficient, wherein the magnitude and direction of the second feedforward amount are both related to the difference;

[0011] The response speed controller is used to calculate the difference and apply the control quantity corresponding to the calculation result to the fully hydraulic steering system so as to improve the response speed of the fully hydraulic steering system together with the second feedforward controller.

[0012] In one possible implementation, the duration for which the first feedforward controller applies the first feedforward amount is greater than the response time of the fully hydraulic steering system.

[0013] In one possible implementation, the first feedforward controller is further configured to clear the first feedforward amount to zero when the current target angle request or the current target angle request trend has not changed direction;

[0014] The second feedforward controller is further configured to clear the second feedforward quantity to zero when the absolute value of the difference is less than the first reset coefficient.

[0015] In one possible implementation, the response speed controller is a PID controller, an incomplete derivative PID controller, or a fuzzy PID controller.

[0016] The response speed controller is also used to perform proportional, integral, and differential operations on the difference, and apply control quantities corresponding to the three operation results to the fully hydraulic steering system.

[0017] In one possible implementation, the response speed controller is further configured to clear the integral result to zero when the difference is less than the second reset coefficient;

[0018] The response speed controller is also used to clear the differential operation result to zero when the difference is less than the third reset coefficient.

[0019] In one possible implementation, the steering control system is used to perform low-pass filtering on the current target steering angle request.

[0020] In one possible implementation, the steering control system is further configured to differentiate the filtered current target turning angle request and determine, based on the differentiation result, whether the current target turning angle request or the trend of the current target turning angle request has changed direction.

[0021] In one possible implementation, the second feedforward controller is further configured to apply a second feedforward amount to the fully hydraulic steering system in the same direction as the current target steering angle request when the sign of the difference is positive;

[0022] The second feedforward controller is further configured to apply a second feedforward amount to the fully hydraulic steering system in the opposite direction to the current target steering angle request when the sign of the difference is negative.

[0023] On the one hand, a steering control method for a fully hydraulic steering system of an unmanned vehicle is provided for use in the steering control system described above, the method comprising:

[0024] When the current target steering angle request or the current target steering angle request trend switching direction is detected by the autonomous driving system, a first feedforward amount is applied to the full hydraulic steering system in the same direction as the current target steering angle request or the current target steering angle request trend, wherein the magnitude of the first feedforward amount is related to the magnitude of the current target steering angle request;

[0025] When the absolute value of the difference between the current target steering angle request and the actual steering angle fed back by the steering angle sensor is greater than the setting coefficient, a second feedforward amount is applied to the full hydraulic steering system, wherein the magnitude and direction of the second feedforward amount are both related to the difference;

[0026] The difference is calculated, and the control quantity corresponding to the calculation result is applied to the fully hydraulic steering system so as to improve the response speed of the fully hydraulic steering system together with the second feedforward controller.

[0027] On the one hand, an intelligent driving vehicle is provided, which includes an automatic driving system, a fully hydraulic steering system, wheels, a steering wheel, and a steering control system as described above.

[0028] The beneficial effects of the technical solution provided in this application include at least the following:

[0029] The first feedforward controller can apply a first feedforward amount to the fully hydraulic steering system in the same direction as the current target steering angle request or the current target steering angle request trend when the automatic driving system outputs the current target steering angle request or the current target steering angle request trend changes direction. This reduces the steering delay of the fully hydraulic steering system by increasing the first feedforward amount in advance, thereby improving the response speed when the steering direction changes.

[0030] The second feedforward controller can apply a second feedforward amount to the full hydraulic steering system when the absolute value of the difference between the current target steering angle request and the actual steering angle fed back by the steering angle sensor is greater than the setting coefficient, thereby improving the adjustment accuracy and adjustment speed of the full hydraulic steering system.

[0031] The response speed controller can calculate the difference and apply the control quantity corresponding to the calculation result to the fully hydraulic steering system, thereby improving the static and dynamic response characteristics of the fully hydraulic steering system, so as to improve the response speed of the fully hydraulic steering system together with the second feedforward controller.

[0032] When the difference is less than the second reset coefficient, the speed response controller resets the integral calculation result to zero; when the difference is less than the third reset coefficient, the speed response controller resets the derivative calculation result to zero, thus avoiding the influence of integral saturation and derivative saturation on the steering control system. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the structure of a steering control system for an unmanned vehicle provided in one embodiment of this application;

[0035] Figure 2 This is a schematic diagram of the structure of an incomplete differential PID controller provided in one embodiment of this application;

[0036] Figure 3 This is a flowchart of a steering control method for an unmanned vehicle provided in one embodiment of this application. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the implementation methods of this application will be further described in detail below with reference to the accompanying drawings.

[0038] Please refer to Figure 1The diagram shows a structural schematic of a steering control system 100 of a fully hydraulic steering system for an unmanned vehicle provided in an embodiment of this application. The steering control system 100 may include: a first feedforward controller 110, a second feedforward controller 120, a response speed controller 130, and a steering angle sensor 140.

[0039] The input terminals of the first feedforward controller 110, the second feedforward controller 120, the response speed controller 130, and the angle sensor 140 are connected to serve as the input terminals of the steering control system 100, which is connected to the output terminal of the automatic driving system 200. The output terminals of the first feedforward controller 110, the second feedforward controller 120, and the response speed controller 130 are connected to serve as the output terminals of the steering control system 100, which is connected to the input terminal of the fully hydraulic steering system 300. The input terminal of the angle sensor 140 is connected to the wheel or steering wheel 400, which is connected to the fully hydraulic steering system 300.

[0040] The autonomous driving system 200 outputs a target steering angle request to the steering control system 100. The steering control system 100 calculates the feedforward amount based on the target steering angle request and the actual steering angle of the wheel / steering wheel 400, and applies the control amount and feedforward amount to the fully hydraulic steering system 300. The fully hydraulic steering system 300 controls the wheel / steering wheel 400 to rotate based on the control amount and feedforward amount, so as to realize the steering control of the intelligent driving vehicle.

[0041] The steering control in this embodiment is divided into three control branches, which will be described in detail below.

[0042] (1) A first feedforward controller 110 is used to apply a first feedforward amount to the full hydraulic steering system 300 in the same direction as the current target angle request or the current target angle request trend when the current target angle request or the current target angle request trend switching direction is detected by the automatic driving system 200.

[0043] Within the turning range, the autonomous driving system 200 can sequentially output target turning angle requests to the steering control system 100 at regular angular intervals. For example, when the turning range is [20°, 30°] and the interval angle is 1°, the autonomous driving system 200 sequentially outputs target turning angle requests of 20°, 21°, 22°, ..., 30° to the steering control system 100. As another example, when the turning ranges are [20°, 30°] and [30°, 0°], and the interval angle is 2°, the autonomous driving system 200 sequentially outputs target turning angle requests of 20°, 22°, 24°, ..., 30°, 28°, 26°, ..., 2°, 0° to the steering control system 100.

[0044] The autonomous driving system 200 outputs multiple target turning angle requests. For ease of explanation, this embodiment distinguishes different target turning angle requests based on the output time of the target turning angle request. Specifically, the target turning angle request output by the autonomous driving system 200 at the current moment is called the current target turning angle request, and the target turning angle request output by the autonomous driving system 200 at the moment before the current moment is called the previous target turning angle request.

[0045] In one application scenario, the target steering angle request or trend output by the autonomous driving system 200 may change direction, for example, after the target steering angle request changes from 20° to 30°, it may change back to 0°. At this time, the steering control system 100 detects whether the current target steering angle request or trend has changed direction. When the current target steering angle request or trend changes direction, the system activates the first feedforward controller 110 and maintains it for a predetermined duration, so that the first feedforward controller 110 outputs a first feedforward amount during the direction change of the fully hydraulic steering system 300. This reduces the steering delay of the fully hydraulic steering system 300 by increasing the first feedforward amount in advance, improving the response speed during direction changes.

[0046] Before detecting whether the current target angle request or the current target angle request trend has changed direction, the steering control system 100 performs low-pass filtering on the current target angle request.

[0047] During the detection process, to avoid communication delays and noise interference, the steering control system 100 needs to perform low-pass filtering on the current target steering angle request. The filtering formula is as follows: Where a(n) represents the filtered current target turning angle request, a in (n) represents the current target corner request, a in (n-1) represents the previous target turning angle request, and k represents the first-order filter coefficient. The value of k can be set according to actual needs.

[0048] Then, the steering control system 100 can differentiate the filtered current target angle request and determine whether the current target angle request or its trend has changed direction based on the differentiation result. Specifically, when the differentiation result is greater than or less than 0, it is determined that the current target angle request or its trend has changed direction; when the differentiation result is equal to 0, it is determined that the current target angle request or its trend has not changed direction. For example, if the trend of the target angle changes from left to right to right to left, or from right to left to left to right, it is considered that the current target angle request or its trend has changed direction.

[0049] If the current target steering angle request or the current target steering angle request trend changes direction, the steering control system 100 needs to activate the first feedforward controller 110, keeping it active for a predetermined duration. This predetermined duration needs to be greater than the response time of the full hydraulic steering system 300 to ensure that the first feedforward controller 110 can output a first feedforward amount to the full hydraulic steering system 300 during steering. That is, the duration for which the first feedforward controller 110 applies the first feedforward amount is greater than the response time of the full hydraulic steering system 300. Therefore, the first feedforward controller 110 is a feedforward controller with feedforward conditions, and the steering changes under these conditions.

[0050] In this embodiment, the first feedforward controller 110 also needs to determine the value and application direction of the first feedforward amount. When determining the value, the first feedforward controller 110 is also used to obtain a preset mapping table, which stores the correspondence between multiple target steering angle requests and multiple first feedforward amounts; and to search for the first feedforward amount corresponding to the current target steering angle request in the mapping table. When determining the application direction, when the direction changes from right to left, the first feedforward controller 110 applies a leftward first feedforward amount to the fully hydraulic steering system 300; when the direction changes from left to right, the first feedforward controller 110 applies a rightward first feedforward amount to the fully hydraulic steering system 300.

[0051] When the current target angle request or the current target angle request trend has not changed direction, the first feedforward controller 110 clears the first feedforward quantity to zero.

[0052] In one example, when the steering range gradually changes from 20° to 30° and then from 30° to 0°, the first feedforward controller 110, upon detecting a change in the direction of change, adds a first feedforward amount in the current direction of change (30°~0°). That is, when the actual steering angle changes from 20° to 30°, and the direction change is detected when it approaches but does not reach 30°, the request to turn to 30° is no longer executed, and the request to turn to 28°~1° is executed directly. The first feedforward amount is added in advance to reduce the reversing delay of the full hydraulic steering system 300.

[0053] (2) The second feedforward controller 120 is used to apply a second feedforward amount to the full hydraulic steering system 300 when the absolute value of the difference between the current target steering angle and the actual steering angle fed back by the steering angle sensor 140 is greater than the setting coefficient, wherein the magnitude and direction of the second feedforward amount are related to the difference.

[0054] Specifically, when the angle sensor 140 is connected to the steering wheel 400, it functions as a steering wheel angle sensor; when connected to the wheel 400, it functions as a wheel angle sensor. By selecting angle sensors 140 based on different principles, the collected angle information can be converted into an actual angle with consistent units for the current target angle using the Ackermann steering principle formula, the steering curvature and angle conversion formula, and the correspondence between steering wheel angle and wheel angle, thus facilitating control.

[0055] To address the low adjustment accuracy and slow adjustment speed of the fully hydraulic steering system 300, this embodiment adds a fixed second feedforward controller 120. When the automatic driving system 200 inputs the current target steering angle request a... in The actual turning angle α of the feedback back When the difference is greater than the setting coefficient, a second feedforward is applied to the full hydraulic steering system 300; when the current target steering angle request a is input by the automatic driving system 200... in The actual turning angle α of the feedback back When the difference is less than the first reset coefficient, the second feedforward quantity is cleared to zero to prevent the target rotation angle from exceeding the expected request due to the open-loop feedforward controller.

[0056] When determining the direction of application of the second feedforward amount, the second feedforward controller 120 is further configured to apply a second feedforward amount to the fully hydraulic steering system 300 in the same direction as the current target steering angle request when the sign of the difference is positive; the second feedforward controller 120 is further configured to apply a second feedforward amount to the fully hydraulic steering system 300 in the opposite direction to the current target steering angle request when the sign of the difference is negative.

[0057] The setting coefficient and the first reset coefficient can be obtained through calibration during implementation, and the response speed can be improved by adjusting the second feedforward amount mapped to different target turning angle requests. For example, the magnitude of the second feedforward amount can be set to be positively correlated with the length of the straight driving condition during vehicle travel. In this way, when the straight driving condition of the autonomous vehicle is relatively long, the second feedforward amount corresponding to the target turning angle request can be increased to make it converge quickly.

[0058] (3) Response speed controller 130 is used to calculate the difference and apply the control quantity corresponding to the calculation result to the full hydraulic steering system 300 so as to improve the response speed of the full hydraulic steering system 300 together with the second feedforward controller 120.

[0059] In this embodiment, the response speed controller 130 is a PID (Proportional Integral Derivative) controller, an incomplete derivative PID controller, or a fuzzy PID controller. The response speed controller 130 is also used to perform proportional, integral, and derivative operations on the difference, respectively, and apply control quantities corresponding to the three operation results to the fully hydraulic steering system.

[0060] Please refer to Figure 2 The incomplete derivative PID controller shown, K p The proportional coefficient for term P is used to reduce the settling time of the fully hydraulic steering system 300°; T i T represents the integral coefficient of term I, used to reduce the steady-state error of the fully hydraulic steering system 300; d Tf represents the differential coefficient of the D term, which is used to reduce the overshoot introduced by the P and I terms and improve dynamic characteristics; Tf represents the first-order filter coefficient of the D term. A first-order low-pass filter is introduced after the differential term, which can effectively avoid high-frequency interference caused by sudden changes in error disturbance.

[0061] To avoid the impact of integral and derivative saturation on the steering control system 100, limits and reset procedures can be introduced for terms I and D. Specifically, the response speed controller 130 is also used to clear the integral calculation result to zero when the difference is less than the second reset coefficient; the response speed controller 130 is also used to clear the derivative calculation result to zero when the difference is less than the third reset coefficient.

[0062] In this embodiment, the second feedforward controller 120 and the response speed controller 130 in the steering control system 100 are used to improve the dynamic characteristics of the full hydraulic steering system 300. The first feedforward controller 110 with feedforward conditions calculates the target steering angle request of the automatic driving system 200 and applies the first feedforward amount in advance when a change in steering direction is detected, so as to improve the reversing speed of the full hydraulic steering system 300. Therefore, this embodiment can not only improve the speed of steer-by-wire response, but also improve the response speed when the steering direction is switched.

[0063] In summary, the steering control system of the fully hydraulic steering system of the unmanned vehicle provided in this application embodiment has a first feedforward controller that can apply a first feedforward amount consistent with the direction of the current target steering angle request or the trend of the current target steering angle request to the fully hydraulic steering system when the current target steering angle request or the trend of the current target steering angle request is switched by the output of the autonomous driving system. This reduces the steering delay of the fully hydraulic steering system by increasing the first feedforward amount in advance and improves the response speed when the steering direction is switched.

[0064] The second feedforward controller can apply a second feedforward amount to the full hydraulic steering system when the absolute value of the difference between the current target steering angle request and the actual steering angle fed back by the steering angle sensor is greater than the setting coefficient, thereby improving the adjustment accuracy and adjustment speed of the full hydraulic steering system.

[0065] The response speed controller can calculate the difference and apply the control quantity corresponding to the calculation result to the fully hydraulic steering system, thereby improving the static and dynamic response characteristics of the fully hydraulic steering system, so as to improve the response speed of the fully hydraulic steering system together with the second feedforward controller.

[0066] When the difference is less than the second reset coefficient, the response speed controller resets the integral calculation result to zero; when the difference is less than the third reset coefficient, the response speed controller resets the derivative calculation result to zero, thus avoiding the influence of integral saturation and derivative saturation on the steering control system.

[0067] Please refer to Figure 3 This document illustrates a flowchart of a steering control method for a fully hydraulic steering system of an unmanned vehicle according to an embodiment of this application. This steering control method for the fully hydraulic steering system of the unmanned vehicle can be applied to… Figure 1 In the steering control system shown, the steering control method may include:

[0068] Step 301: When the current target steering angle request or the current target steering angle request trend switching direction is detected, a first feedforward amount consistent with the direction of the current target steering angle request or the current target steering angle request trend is applied to the full hydraulic steering system, wherein the magnitude of the first feedforward amount is related to the magnitude of the current target steering angle request.

[0069] Before detecting whether the current target angle request or the current target angle request trend has changed direction, the steering control system performs low-pass filtering on the current target angle request.

[0070] During the detection process, to avoid communication delays and noise interference, the steering control system needs to perform a low-pass filter on the current target steering angle request. The filtering formula is as follows: Where a(n) represents the filtered current target turning angle request, a in (n) represents the current target corner request, a in (n-1) represents the previous target turning angle request, and k represents the first-order filter coefficient. The value of k can be set according to actual needs.

[0071] Then, the steering control system can differentiate the filtered current target angle request and determine whether the current target angle request or its trend has changed direction based on the differentiation result. Specifically, when the differentiation result is greater than or less than 0, it is determined that the current target angle request or its trend has changed direction; when the differentiation result is equal to 0, it is determined that the current target angle request or its trend has not changed direction. For example, if the trend of the target angle changes from left to right to right to left, or from right to left to left to right, it is considered that the current target angle request or its trend has changed direction.

[0072] If the current target steering angle request or the current target steering angle request trend changes direction, the steering control system needs to activate the first feedforward controller, keeping it active for a predetermined duration. This predetermined duration must be greater than the response time of the full hydraulic steering system to ensure that the first feedforward controller can output a first feedforward amount to the full hydraulic steering system during steering. In other words, the duration for which the first feedforward controller applies the first feedforward amount is greater than the response time of the full hydraulic steering system.

[0073] In this embodiment, the first feedforward controller also needs to determine the value and application direction of the first feedforward amount. When determining the value, the first feedforward controller obtains a preset mapping table, which stores the correspondence between multiple target steering angle requests and multiple first feedforward amounts; it then searches the mapping table for the first feedforward amount corresponding to the current target steering angle request. When determining the application direction, if the direction changes from right to left, the first feedforward controller applies a leftward first feedforward amount to the fully hydraulic steering system; if the direction changes from left to right, the first feedforward controller applies a rightward first feedforward amount to the fully hydraulic steering system.

[0074] When the current target angle request or the current target angle request trend has not changed direction, the first feedforward controller clears the first feedforward quantity to zero.

[0075] Step 302: When the absolute value of the difference between the current target steering angle request and the actual steering angle fed back by the steering angle sensor is greater than the setting coefficient, a second feedforward amount is applied to the full hydraulic steering system, wherein the magnitude and direction of the second feedforward amount are both related to the difference.

[0076] In this embodiment, the steering angle sensor can be a steering wheel angle sensor or a wheel angle sensor. When using steering angle sensors based on different principles, the collected steering angle information can be converted into an actual steering angle with the same unit as the current target steering angle by using the Ackermann steering principle formula, the steering curvature and steering angle conversion formula, and the correspondence between steering wheel angle and wheel angle, so as to facilitate control.

[0077] To address the low adjustment accuracy and slow adjustment speed of fully hydraulic steering systems, this embodiment adds a fixed second feedforward controller. When the autonomous driving system inputs the current target steering angle request a... in The actual turning angle α of the feedback back When the difference is greater than the setting coefficient, a second feedforward is applied to the full hydraulic steering system; when the current target steering angle request input by the automatic driving system is a in The actual turning angle α of the feedback back When the difference is less than the first reset coefficient, the second feedforward quantity is cleared to zero to prevent the target rotation angle from exceeding the expected request due to the open-loop feedforward controller.

[0078] When determining the direction of application of the second feedforward, the second feedforward controller applies a second feedforward to the fully hydraulic steering system in the same direction as the current target steering angle request when the sign of the difference is positive; and applies a second feedforward to the fully hydraulic steering system in the opposite direction to the current target steering angle request when the sign of the difference is negative.

[0079] The setting coefficient and the first reset coefficient can be obtained through calibration during implementation, and the response speed can be improved by adjusting the second feedforward amount mapped to different target turning angle requests. For example, the magnitude of the second feedforward amount can be set to be positively correlated with the length of the straight driving condition during vehicle travel. In this way, when the straight driving condition of the autonomous vehicle is relatively long, the second feedforward amount corresponding to the target turning angle request can be increased to make it converge quickly.

[0080] Step 303: Calculate the difference and apply the control quantity corresponding to the calculation result to the full hydraulic steering system so as to improve the response speed of the full hydraulic steering system together with the second feedforward controller.

[0081] In this embodiment, the response speed controller is a PID controller, an incomplete derivative PID controller, or a fuzzy PID controller. The response speed controller performs proportional, integral, and derivative operations on the difference, respectively, and applies the control quantities corresponding to the three operation results to the fully hydraulic steering system.

[0082] Please refer to Figure 2 The incomplete derivative PID controller shown, K p The proportional coefficient for term P is used to reduce the settling time of a fully hydraulic steering system; T i T represents the integral coefficient of term I, used to reduce the steady-state error of the fully hydraulic steering system; d Tf represents the differential coefficient of the D term, which is used to reduce the overshoot introduced by the P and I terms and improve dynamic characteristics; Tf represents the first-order filter coefficient of the D term. A first-order low-pass filter is introduced after the differential term, which can effectively avoid high-frequency interference caused by sudden changes in error disturbance.

[0083] To avoid the impact of integral and derivative saturation on the steering control system, limits and reset procedures can be introduced for the I and D terms. Specifically, the response speed controller resets the integral calculation result to zero when the difference is less than the second reset coefficient; the response speed controller resets the derivative calculation result to zero when the difference is less than the third reset coefficient.

[0084] In summary, the steering control method for the fully hydraulic steering system of the unmanned vehicle provided in this application embodiment allows the first feedforward controller to apply a first feedforward amount consistent with the direction of the current target steering angle request or the trend of the current target steering angle request to the fully hydraulic steering system when the current target steering angle request or the trend of the current target steering angle request is switched by the output of the autonomous driving system. This reduces the steering delay of the fully hydraulic steering system by increasing the first feedforward amount in advance and improves the response speed when the steering direction is switched.

[0085] The second feedforward controller can apply a second feedforward amount to the full hydraulic steering system when the absolute value of the difference between the current target steering angle request and the actual steering angle fed back by the steering angle sensor is greater than the setting coefficient, thereby improving the adjustment accuracy and adjustment speed of the full hydraulic steering system.

[0086] The response speed controller can calculate the difference and apply the control quantity corresponding to the calculation result to the fully hydraulic steering system, thereby improving the static and dynamic response characteristics of the fully hydraulic steering system, so as to improve the response speed of the fully hydraulic steering system together with the second feedforward controller.

[0087] When the difference is less than the second reset coefficient, the response speed controller resets the integral calculation result to zero; when the difference is less than the third reset coefficient, the response speed controller resets the derivative calculation result to zero, thus avoiding the influence of integral saturation and derivative saturation on the steering control system.

[0088] One embodiment of this application provides an intelligent driving vehicle, the intelligent driving vehicle including an automatic driving system, a fully hydraulic steering system, wheels, a steering wheel, and so on. Figure 1 The steering control system shown.

[0089] Those skilled in the art will understand that all or part of the steps of the above embodiments can be implemented by hardware or by a program instructing related hardware. The program can be stored in a computer-readable storage medium, such as a read-only memory, a disk, or an optical disk.

[0090] The above description is not intended to limit the embodiments of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the embodiments of this application should be included within the protection scope of the embodiments of this application.

Claims

1. A steering control system for a fully hydraulic steering system of an unmanned vehicle, characterized in that, The steering control system includes a first feedforward controller, a second feedforward controller, a response speed controller, and a steering angle sensor; The input terminals of the first feedforward controller, the second feedforward controller, the response speed controller, and the output terminal of the steering angle sensor are connected together to serve as the input terminal of the steering control system, which is then connected to the output terminal of the autonomous driving system. The output terminals of the first feedforward controller, the second feedforward controller, and the response speed controller are connected together to serve as the output terminal of the steering control system, and the output terminal of the steering control system is connected to the input terminal of the full hydraulic steering system. The input terminal of the steering angle sensor is connected to the wheel or steering wheel, and the wheel or steering wheel is connected to the fully hydraulic steering system; The first feedforward controller is configured to apply a first feedforward amount to the fully hydraulic steering system in the same direction as the current target steering angle request or the current target steering angle request trend when the current target steering angle request or the current target steering angle request trend switching direction is detected by the autonomous driving system, wherein the magnitude of the first feedforward amount is related to the magnitude of the current target steering angle request; The second feedforward controller is configured to apply a second feedforward amount to the fully hydraulic steering system when the absolute value of the difference between the current target steering angle request and the actual steering angle fed back by the steering angle sensor is greater than the setting coefficient, wherein the magnitude and direction of the second feedforward amount are both related to the difference; The response speed controller is used to calculate the difference and apply the control quantity corresponding to the calculation result to the fully hydraulic steering system so as to improve the response speed of the fully hydraulic steering system together with the second feedforward controller.

2. The steering control system of the fully hydraulic steering system of the unmanned vehicle according to claim 1, characterized in that, The duration for which the first feedforward controller applies the first feedforward amount is greater than the response time of the fully hydraulic steering system.

3. The steering control system of the fully hydraulic steering system of the unmanned vehicle according to claim 1, characterized in that, The first feedforward controller is further configured to clear the first feedforward quantity to zero when the current target angle request or the current target angle request trend has not changed direction; The second feedforward controller is further configured to clear the second feedforward quantity to zero when the absolute value of the difference is less than the first reset coefficient.

4. The steering control system of the fully hydraulic steering system of the unmanned vehicle according to claim 1, characterized in that, The response speed controller is a PID controller, an incomplete derivative PID controller, or a fuzzy PID controller. The response speed controller is also used to perform proportional, integral, and differential operations on the difference, and apply control quantities corresponding to the three operation results to the fully hydraulic steering system.

5. The steering control system of the fully hydraulic steering system of the unmanned vehicle according to claim 4, characterized in that, The response speed controller is also used to clear the integral calculation result to zero when the difference is less than the second reset coefficient; The response speed controller is also used to clear the differential operation result to zero when the difference is less than the third reset coefficient.

6. The steering control system of the fully hydraulic steering system of the unmanned vehicle according to claim 1, characterized in that, The steering control system is used to perform low-pass filtering on the current target steering angle request.

7. The steering control system of the fully hydraulic steering system of the unmanned vehicle according to claim 6, characterized in that, The steering control system is also used to differentiate the filtered current target turning angle request, and determine whether the current target turning angle request or the trend of the current target turning angle request has changed direction based on the differentiation result.

8. The steering control system of the fully hydraulic steering system of the unmanned vehicle according to claim 1, characterized in that, The second feedforward controller is further configured to apply a second feedforward amount to the fully hydraulic steering system in the same direction as the current target steering angle request when the sign of the difference is positive; The second feedforward controller is further configured to apply a second feedforward amount to the fully hydraulic steering system in the opposite direction to the current target steering angle request when the sign of the difference is negative.

9. A steering control method for a fully hydraulic steering system of an unmanned vehicle, characterized in that, In a steering control system as described in any one of claims 1 to 8, the method comprises: When the current target steering angle request or the current target steering angle request trend switching direction is detected by the autonomous driving system, a first feedforward amount is applied to the full hydraulic steering system in the same direction as the current target steering angle request or the current target steering angle request trend, wherein the magnitude of the first feedforward amount is related to the magnitude of the current target steering angle request; When the absolute value of the difference between the current target steering angle request and the actual steering angle fed back by the steering angle sensor is greater than the setting coefficient, a second feedforward amount is applied to the full hydraulic steering system, wherein the magnitude and direction of the second feedforward amount are both related to the difference; The difference is calculated, and the control quantity corresponding to the calculation result is applied to the fully hydraulic steering system so as to improve the response speed of the fully hydraulic steering system together with the second feedforward controller.

10. An intelligent driving vehicle, characterized in that, The intelligent driving vehicle includes an autonomous driving system, a fully hydraulic steering system, wheels, a steering wheel, and a steering control system as described in any one of claims 1 to 8.

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