A control method and system for steering a guided vehicle

Abstract

This application primarily relates to the field of vehicle motion control technology, specifically to a control method and system for steering a guided vehicle. This application provides a control method for steering a guided vehicle, comprising: acquiring the desired steering angle, desired angular acceleration, and actual steering angle of the guided vehicle; determining a steering angle deviation based on the desired steering angle and the actual steering angle; determining a PID feedback control quantity and a threshold feedforward compensation quantity for the dead zone of the steering proportional valve based on the steering angle deviation; determining an angular acceleration feedforward compensation quantity based on the desired angular acceleration; superimposing the PID feedback control quantity, the threshold feedforward compensation quantity, and the angular acceleration feedforward compensation quantity to obtain a final control quantity; and driving the steering actuator of the guided vehicle to achieve steering based on the magnitude and direction of the final control quantity, thereby improving the dynamic response speed and achieving smooth and rapid full-range control.

Description

Technical Field

[0001] This application mainly relates to the field of vehicle motion control technology, and specifically to a control method and system for steering a guided vehicle. Background Technology

[0002] Automated Guided Vehicles (AGVs) are widely used in industrial logistics, port terminals, smart warehousing, and other scenarios. During operation, AGVs need to perform steering control according to the navigation path. The response speed, control accuracy, and smoothness of steering control directly affect the vehicle's path tracking effect, operating efficiency, and operational safety.

[0003] Current AGV steering control typically employs the classic PID (Proportional-Integral-Derivative) control method. This method calculates the proportional, integral, and derivative terms based on the deviation between the desired and actual steering angles, and outputs a control quantity to drive the steering actuator, such as an electro-hydraulic proportional valve.

[0004] However, in practical applications, especially for AGVs with high dynamic performance requirements, the above-mentioned conventional PID steering control method has the following shortcomings: First, the dynamic response speed is limited. When the AGV starts to turn or the target turning angle changes abruptly, due to the inherent lag characteristics of PID control, especially the integral element, the system exhibits a significant response delay, resulting in steering lag during the AGV's start-up phase and when reaching the target position.

[0005] Secondly, control parameters are difficult to optimize under all operating conditions. AGV steering actuators (such as electro-hydraulic proportional valves) typically have inherent dead-zone characteristics. When the control quantity changes near the dead zone, the actuator output is insensitive. To obtain sufficient response with small deviations, a large proportional coefficient is often required; however, an excessively large proportional coefficient can cause overshoot or oscillation in the system with large deviations. Therefore, a single PID parameter set cannot simultaneously achieve both fine control near the dead zone and fast, stable response across the entire range, presenting a contradiction between "speed" and "stability."

[0006] Finally, it lacks the ability to anticipate and compensate for external disturbances. Conventional PID is a feedback control based on historical deviations, which cannot compensate for known and predictable dynamic changes in advance (such as angular acceleration requirements pre-calculated based on the navigation path), thus limiting further improvements in the system's response characteristics.

[0007] In summary, existing AGV steering control methods based on conventional PID control are insufficient in terms of response speed, parameter adaptability, and predictive compensation, making it difficult to meet the ever-increasing steering performance requirements of high-efficiency, high-precision AGVs. Summary of the Invention

[0008] This application provides a control method and system for steering a guided vehicle, which solves the technical problem in the prior art of how to overcome the contradiction between dynamic response lag and PID parameter tuning caused by delayed response and the inherent characteristics of the actuator in AGV steering control.

[0009] The technical solution adopted in this application to solve the above-mentioned technical problems is a control method for steering a guided vehicle, including: Obtain the desired steering angle, desired angular acceleration, and actual steering angle of the guided vehicle; The steering angle deviation is determined based on the expected steering angle and the actual steering angle, and the PID feedback control quantity and the threshold feedforward compensation quantity of the steering proportional valve dead zone are determined based on the steering angle deviation. Determine the angular acceleration feedforward compensation amount based on the desired angular acceleration; The PID feedback control quantity, the threshold feedforward compensation quantity, and the angular acceleration feedforward compensation quantity are superimposed to obtain the final control quantity, and the steering actuator of the guided vehicle is driven to achieve steering based on the magnitude and direction of the final control quantity.

[0010] In one embodiment of this application, determining the steering angle deviation based on the desired steering angle and the actual steering angle, and determining the PID feedback control quantity and the threshold feedforward compensation quantity for the steering proportional valve dead zone based on the steering angle deviation, further includes: The steering angle deviation is determined based on the difference between the desired steering angle and the actual steering angle, and a PID calculation is performed on the steering angle deviation to obtain the PID feedback control quantity.

[0011] In one embodiment of this application, determining the steering angle deviation based on the desired steering angle and the actual steering angle, and determining the PID feedback control quantity and the threshold feedforward compensation quantity for the steering proportional valve dead zone based on the steering angle deviation, further includes: The threshold feedforward compensation amount of the steering proportional valve dead zone is determined based on the direction of the steering angle deviation and the preset proportional valve dead zone threshold.

[0012] In one embodiment of this application, determining the threshold feedforward compensation amount for the steering proportional valve dead zone based on the steering angle deviation and a preset proportional valve dead zone threshold further includes: When the absolute value of the steering angle deviation is greater than a first preset deviation threshold, the threshold feedforward compensation amount of the steering proportional valve dead zone is determined based on the steering angle deviation and the preset proportional valve dead zone threshold. The direction of the threshold feedforward compensation is consistent with the direction of the steering angle deviation.

[0013] In one embodiment of this application, determining the angular acceleration feedforward compensation amount based on the desired angular acceleration further includes: The desired angular acceleration is multiplied by the preset feedforward gain coefficient to obtain the angular acceleration feedforward compensation amount.

[0014] In one embodiment of this application, the step of controlling the steering actuator of the guided vehicle to achieve steering based on the magnitude and direction of the final control quantity further includes: When the final control quantity is a first direction control quantity, the absolute value of the final control quantity is output to the first steering proportional valve; When the final control quantity is a second direction control quantity, the absolute value of the final control quantity is output to the second steering proportional valve; The first steering proportional valve and the second steering proportional valve are used to drive the guided vehicle to turn in two opposite directions, respectively.

[0015] In one embodiment of this application, it further includes: When the guided vehicle meets the preset no-steering requirement condition, a holding control quantity is output to the steering proportional valve, so that the steering proportional valve is in a pre-action state.

[0016] In one embodiment of this application, the preset no-steering-requirement condition includes: The absolute value of the steering angle deviation is less than the second preset deviation threshold, and the desired angular acceleration is zero.

[0017] In one embodiment of this application, it further includes: Obtain the last effective control direction of the guided vehicle, and determine the current required direction based on the current steering angle deviation; Based on the comparison between the current demand direction and the previous effective control direction, determine whether to adjust the threshold feedforward compensation amount of the dead zone of the steering proportional valve.

[0018] In one embodiment of this application, it further includes: Obtain the load status of the guided vehicle; The feedforward gain coefficient is adjusted according to the load condition, and the angular acceleration feedforward compensation amount is determined based on the adjusted feedforward gain coefficient.

[0019] To address the aforementioned technical problems, this application also proposes a steering control system for a guided vehicle, comprising: The acquisition module is used to acquire the desired steering angle and desired angular acceleration of the guided vehicle, as well as the actual steering angle. The processing module, connected to the acquisition module, is used to determine the steering angle deviation based on the desired steering angle and the actual steering angle, and to determine the PID feedback control quantity and the threshold feedforward compensation quantity for the dead zone of the steering proportional valve based on the steering angle deviation. Determine the angular acceleration feedforward compensation amount based on the desired angular acceleration; The final control quantity is obtained by superimposing the PID feedback control quantity, the threshold feedforward compensation quantity, and the angular acceleration feedforward compensation quantity. The drive module is used to drive the steering actuator of the guided vehicle to achieve steering based on the magnitude and direction of the final control quantity.

[0020] In one embodiment of this application, the processing module includes a PID calculation unit, a dead-zone feedforward calculation unit, an angular acceleration feedforward calculation unit, and a superposition unit: The PID calculation unit is used to determine the steering angle deviation based on the difference between the desired steering angle and the actual steering angle, and to perform PID calculation on the steering angle deviation to obtain the PID feedback control quantity. The dead zone feedforward calculation unit is used to determine the threshold feedforward compensation amount of the steering proportional valve dead zone based on the direction of the steering angle deviation and the preset proportional valve dead zone threshold. The angular acceleration feedforward calculation unit is used to multiply the desired angular acceleration by a preset feedforward gain coefficient to obtain the angular acceleration feedforward compensation amount. The superposition unit is used to superimpose the PID feedback control quantity, the threshold feedforward compensation quantity, and the angular acceleration feedforward compensation quantity to obtain the final control quantity.

[0021] In one embodiment of this application, the dead-zone feedforward calculation unit further includes: Obtain the last effective control direction of the guided vehicle, and determine the current required direction based on the current steering angle deviation; Based on the comparison between the current demand direction and the previous effective control direction, determine whether to adjust the threshold feedforward compensation amount of the dead zone of the steering proportional valve.

[0022] In one embodiment of this application, the angular acceleration feedforward calculation unit further includes: Obtain the load status of the guided vehicle; The feedforward gain coefficient is adjusted according to the load condition, and the angular acceleration feedforward compensation amount is determined based on the adjusted feedforward gain coefficient.

[0023] This application provides a steering control method and system for a guided vehicle. By introducing angular acceleration feedforward compensation and dead zone threshold feedforward compensation, the control system can output control quantities in advance according to the expected dynamic changes provided by navigation, and actively inject compensation quantities when steering starts or when crossing the dead zone of the proportional valve is required. This improves the problem of the proportional valve not acting or lagging, greatly enhances the dynamic response speed, and achieves smooth and fast full-process control. Attached Figure Description

[0024] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 The present application discloses a step diagram of a control method for steering a guided vehicle according to an embodiment of the present application; Figure 2 A schematic diagram of the control system structure for steering of a guided vehicle according to an embodiment of this application is disclosed; Figure 3 A schematic flowchart of a steering control method for a guided vehicle according to an embodiment of this application is disclosed; Figure 4 This paper presents a schematic diagram illustrating the final control quantity synthesis and the proportional valve drive signal flow of an embodiment of this application.

[0025] Explanation of reference numerals in the accompanying drawings for specific embodiments: 101 navigation interface module; 102 State Awareness Module; 103 processing module; 1031 PID calculation unit; 1032 dead-zone feedforward computing units; 1033 angular acceleration feedforward calculation unit; 1034 stacked elements; 104 driver module; 105 steering proportional valve; 106 Steering actuator; 201 Navigation System; 202 Angle Sensor. Detailed Implementation

[0026] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0027] Flowcharts are used in this application to illustrate the operations performed by the system according to embodiments of this application. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, various steps can be processed in reverse order or simultaneously. Furthermore, other operations may be added to these processes, or one or more steps may be removed from these processes.

[0028] AGV (Automated Guided Vehicle) steering control is essential for AGVs to turn along a planned path during operation, requiring precise control of the wheel steering angle. The steering control system calculates a control signal using a PID algorithm based on the deviation between the desired steering angle and the actual steering angle. This signal then drives the steering actuator (such as a proportional valve) to adjust the wheel angle, thereby achieving AGV steering.

[0029] The proportional valve can be an electro-hydraulic control valve that receives an electrical signal (such as a voltage or PWM signal) and opens its valve port proportionally to the signal strength, thereby controlling the flow of hydraulic oil to the steering cylinder. The flow rate determines the steering speed. Because the proportional valve does not operate when the input signal is very small, a "dead zone" occurs.

[0030] This application provides a steering control method for a guided vehicle, which improves the tracking accuracy and smoothness of steering control by introducing threshold feedforward based on the dead zone characteristics of a proportional valve and angular acceleration feedforward based on navigation information.

[0031] Figure 1 This application discloses a step diagram of a control method for steering a guided vehicle according to an embodiment of the present application, with reference to... Figure 1 As shown, the steering control method for the guided vehicle in this embodiment includes the following steps: Step S1: Obtain the desired steering angle, desired angular acceleration, and actual steering angle of the guided vehicle; Step S2: Determine the steering angle deviation based on the desired steering angle and the actual steering angle, and determine the PID feedback control quantity and the threshold feedforward compensation quantity for the dead zone of the steering proportional valve based on the steering angle deviation; Step S3: Determine the angular acceleration feedforward compensation amount based on the desired angular acceleration; Step S4: The PID feedback control quantity, the threshold feedforward compensation quantity, and the angular acceleration feedforward compensation quantity are superimposed to obtain the final control quantity, and the steering actuator of the guided vehicle is driven to achieve steering according to the magnitude and direction of the final control quantity.

[0032] This application provides a steering control method for a guided vehicle. It employs a PID controller to generate a basic feedback control quantity, actively superimposing a fixed feedforward compensation quantity sufficient to overcome the dead zone threshold of the proportional valve based on the direction of the steering angle deviation of the guided vehicle, and generating an angular acceleration feedforward compensation quantity based on the product of the desired angular acceleration and the feedforward gain coefficient. These three are then superimposed to form the final control quantity to drive the steering proportional valve. This method solves the problems in AGV steering control caused by pure feedback delay, the dead zone characteristics of the proportional valve leading to contradictory control parameter sensitivity, and the lack of predictive compensation resulting in dynamic response lag, lack of response to small deviations, easy overshooting of large deviations, and insufficient tracking accuracy and smoothness. It achieves improved dynamic response speed, elimination of start-up and arrival lag, smooth and rapid control across the entire range, and enhanced tracking accuracy and smoothness.

[0033] The steps of the steering control method for the guided vehicle proposed in this application will be described in detail below. It should be understood that, within the scope of this application, the above-mentioned technical features of this application and the technical features specifically described below (such as in the embodiments) can be combined and related to each other to form a preferred technical solution.

[0034] Step S1: Obtain the desired steering angle, desired angular acceleration, and actual steering angle of the guided vehicle.

[0035] The system acquires the AGV's navigation path information and calculates or receives the current desired steering angle θ_d and its desired angular acceleration α_d from the upper-level navigation system in real time. The desired angular acceleration α_d can be obtained by the navigation system through differential calculation of the desired path, or it can be directly provided by the planning algorithm.

[0036] Obtain the actual steering angle θ_a of the AGV, and determine the steering angle deviation e based on the expected steering angle and the actual steering angle.

[0037] Step S2: Determine the steering angle deviation e based on the desired steering angle and the actual steering angle, and determine the PID feedback control quantity and the threshold feedforward compensation quantity for the dead zone of the steering proportional valve based on the steering angle deviation.

[0038] In one embodiment, the steering angle deviation is determined based on the difference between the desired steering angle and the actual steering angle, and a PID calculation is performed on the steering angle deviation to obtain the PID feedback control quantity.

[0039] In this embodiment, the steering angle deviation e = θ_d - θ_a. The deviation e is input to a classic PID controller to calculate the basic PID feedback control quantity U_pid.

[0040] The PID controller includes adjustable proportional coefficient Kp, integral coefficient Ki, and derivative coefficient Kd. This step aims to eliminate steady-state error and suppress unknown disturbances.

[0041] In some embodiments, the threshold feedforward compensation amount of the steering proportional valve dead zone is determined based on the direction of the steering angle deviation and a preset proportional valve dead zone threshold.

[0042] In this embodiment, the dead zone threshold feedforward compensation amount U_ff1 is calculated based on the direction of the steering angle deviation e and in combination with the preset proportional valve dead zone threshold U_th.

[0043] In one embodiment, in response to the absolute value of the steering angle deviation e being greater than a first preset deviation threshold, the threshold feedforward compensation amount of the steering proportional valve dead zone is determined according to the sign of the steering angle deviation and the preset proportional valve dead zone threshold. The direction of the threshold feedforward compensation is consistent with the direction of the steering angle deviation.

[0044] In this embodiment, when |e|>E0 and the steering control system needs to overcome static error to start steering, let U_ff1=sign(e). U_th, where sign(e) is the sign function; otherwise, let U_ff1=0. Where E0 is the first preset deviation threshold, which is a preset small deviation threshold.

[0045] Specifically, the direction of the steering angle deviation e determines the sign of the dead zone threshold feedforward compensation amount U_ff1.

[0046] If the desired steering angle θ_d is greater than the actual steering angle θ_a, i.e., the deviation e>0, it means that the wheels need to be driven in the positive direction (e.g., left turn) to reduce the deviation. At this time, sign(e) is positive and the dead zone threshold feedforward compensation amount U_ff1 is positive. If the desired steering angle θ_d is less than the actual steering angle θ_a, i.e., the deviation e < 0, it means that the wheels need to be driven in the opposite direction (e.g., right turn). In this case, sign(e) is negative and the dead zone feedforward compensation amount U_ff1 is negative.

[0047] Therefore, when the desired steering angle is greater than the actual steering angle, positive compensation is applied to the proportional valve; when the desired steering angle is less than the actual steering angle, it needs to rotate in the opposite direction, and negative compensation is added at this time.

[0048] When |e|≤E0, let U_ff1=0. It can be seen that the first preset deviation threshold E0 is used to avoid false triggering, that is, compensation is only applied when the absolute value of the deviation exceeds the small threshold E0, so as to prevent frequent injection of step disturbances near the steady state.

[0049] In this embodiment, at the instant of steering initiation or direction change, a fixed compensation amount sufficient to drive the proportional valve spool past the dead zone threshold is actively injected. The sign of this compensation amount represents the required steering direction, and the dead zone threshold U_th of the proportional valve ensures that the spool can reliably exit the dead zone, thereby solving the problem of insensitive initial response caused by the dead zone under small deviations.

[0050] In a preferred embodiment, it further includes: Obtain the last effective control direction of the guided vehicle, and determine the current required direction based on the current steering angle deviation; Based on the comparison between the current demand direction and the previous effective control direction, determine whether to adjust the threshold feedforward compensation amount of the dead zone of the steering proportional valve.

[0051] In this embodiment, the calculation of the threshold feedforward compensation for the dead zone of the steering proportional valve has been optimized to be applicable to more complex operating conditions.

[0052] Specifically, after the steering control system of the guided vehicle is powered on or initialized, the last effective control direction Dir_last is recorded.

[0053] When |e|>E0, calculate the current demand direction Dir_curr, where Dir_curr=sign(e). Compare the current demand direction Dir_curr with the effective control direction Dir_last: If they are the same, it means the steering control system is in continuous control and the dead zone effect has been overcome; in this case, let U_ff1 = 0. If they are different, it means the steering control system may have just experienced reversal or started from a standstill; in this case, let U_ff1 = Dir_curr. U_th K_adj, where K_adj is an adjustment coefficient between 0.8 and 1.2, used to compensate for minor changes in dead zone characteristics caused by variations in oil temperature and pressure. After outputting U_ff1, the effective control direction Dir_last = Dir_curr is updated.

[0054] In this embodiment, through dynamic adjustment, it is possible to intelligently determine when dead zone compensation needs to be injected, avoiding the introduction of unnecessary step disturbances during continuous control and making the control process smoother.

[0055] Step S3: Determine the angular acceleration feedforward compensation amount based on the desired angular acceleration. Based on the desired angular acceleration α_d obtained in Step S1, and the vehicle parameters of the guided vehicle, such as vehicle weight, or other information affecting the turning velocity, the angular acceleration feedforward compensation amount U_ff2 is calculated by mapping through the feedforward gain coefficient K_ff. Angular acceleration feedforward compensation amount U_ff2 = K_ff α_d.

[0056] The feedforward gain coefficient K_ff is a fixed value obtained through system identification or experimental calibration, and is used to convert the angular acceleration requirement into the corresponding proportional valve control quantity pre-feed.

[0057] This step involves "predictive" compensation for the dynamic process of AGV steering, providing control forces in advance to overcome system inertia, thereby significantly improving dynamic response speed and reducing tracking lag.

[0058] In a preferred embodiment, the method further includes: Obtain the load status of the guided vehicle; The feedforward gain coefficient is adjusted according to the load condition, and the angular acceleration feedforward compensation amount is determined based on the adjusted feedforward gain coefficient.

[0059] In this embodiment, the load mass M of the AGV is estimated or measured in real time, and the feedforward gain coefficient K_ff is no longer a fixed value, but is dynamically adjusted according to the load mass M. K_ff=K_ff0 (1+β (M / M0). Where K_ff0 is the reference gain under no-load conditions, M0 is the reference mass, β is the adjustment coefficient, and M is the load mass, which is obtained through offline calibration.

[0060] In this embodiment, not only is the desired angular acceleration α_d obtained, but the current load status identifier (load mass) is also obtained. Based on the load status identifier, the corresponding feedforward gain coefficient K_ff value is selected from the pre-stored different load-gain relationship tables, and then the angular acceleration feedforward compensation amount U_ff2 is calculated, where the angular acceleration feedforward compensation amount U_ff2 = K_ff α_d.

[0061] The feedforward compensation can adapt to changes in AGV load and provide a pre-control force that matches the system's rotational inertia under different loads, thereby maintaining consistent dynamic response performance.

[0062] Step S4: The PID feedback control quantity, the threshold feedforward compensation quantity, and the angular acceleration feedforward compensation quantity are superimposed to obtain the final control quantity, and the steering actuator of the guided vehicle is driven to achieve steering according to the magnitude and direction of the final control quantity.

[0063] In this step, the PID control quantity U_pid, the dead zone threshold feedforward compensation quantity U_ff1, and the angular acceleration feedforward compensation quantity U_ff2 are superimposed to obtain the final control quantity U_final. The final control quantity U_final = U_pid + U_ff1 + U_ff2, and then the final proportional valve control command is generated. This command is output to the steering proportional valve of the AGV to drive the wheels to steer.

[0064] The superposition of U_ff1, U_pid, and U_ff2 yields U_final, the sign of which determines the final control direction. Specifically, the sign of U_pid is determined by the sign of the steering deviation e, the sign of U_ff1 also changes with the direction of the steering deviation e, and the sign of U_ff2 is determined by the direction of the desired angular acceleration α_d. Therefore, U_final is a signed quantity; a positive value represents one direction of rotation (e.g., left turn), and a negative value represents the opposite direction (e.g., right turn). In a dual proportional valve configuration (left-turn proportional valve / right-turn proportional valve), the steering control system directly sends |U_final| to the corresponding proportional valve based on the sign of U_final.

[0065] Therefore, the sign of the dead zone threshold feedforward compensation amount U_ff1 not only participates in the direction determination of the control quantity, but also indirectly determines which proportional valve the compensation amount should be applied to. The whole process does not require additional direction discrimination logic, realizing the integration of direction and drive.

[0066] In one embodiment, in response to the final control quantity being a first directional control quantity, the absolute value of the final control quantity is output to a first steering proportional valve; When the final control quantity is a second direction control quantity, the absolute value of the final control quantity is output to the second steering proportional valve; The first steering proportional valve and the second steering proportional valve are used to drive the guided vehicle to turn in two opposite directions, respectively.

[0067] In this embodiment, since the final control quantity U_final is a signed control quantity, the sign of which indicates the steering direction and the amplitude of which indicates the control intensity, it is mapped to the corresponding steering proportional valve according to the sign and amplitude of U_final.

[0068] When the final control quantity U_final is the first direction control quantity, that is, when U_final>0, |U_final| is output to the left proportional valve, and the right proportional valve outputs 0; When the final control quantity U_final is the second direction control quantity, that is, when U_final<0, |U_final| is output to the right-turn proportional valve, and the output of the left-turn proportional valve is 0; When the final control quantity U_final=0, neither valve has any output.

[0069] Finally, the corresponding proportional valve control command is output to the steering proportional valve of the AGV to drive the wheels to steer.

[0070] Optionally, the steering control method for the guided vehicle provided in this application further includes: S5. In response to the guided vehicle meeting the preset no-steering requirement condition, a holding control quantity is output to the steering proportional valve to put the steering proportional valve in a pre-action state.

[0071] In this step, the steering proportional valve is preheated and held. When it is determined that the AGV has no steering requirement, a small, constant-direction holding voltage or current U_hold is output to the proportional valve to keep the valve core in a micro-motion preheating state, so as to eliminate the static friction of the valve core and improve the response speed of the next action.

[0072] In one embodiment, the preset no-steering requirement condition includes: the absolute value of the steering angle deviation is less than a second preset deviation threshold, and the desired angular acceleration is zero.

[0073] In this embodiment, the steering angle deviation |e| is continuously less than a smaller threshold, that is, the second preset deviation threshold is smaller than the first preset deviation threshold mentioned above.

[0074] This application provides a steering control method for a guided vehicle. By introducing angular acceleration feedforward compensation (U_ff2) and threshold feedforward compensation based on dead zone characteristics (U_ff1), it enables the system to react in advance to known and impending dynamic changes in steering. This is equivalent to providing "predictability" to the PID controller. When the steering control system needs to overcome steady-state error and begin to move, a control quantity sufficient to overcome the dead zone is actively injected. This allows the proportional coefficient Kp in the PID controller to be set at a more optimal value focused on dynamic adjustment, without having to set an excessively large value to "pry" the dead zone. It maintains a fast and stable response throughout the entire stroke, significantly improving the system's adaptability to different operating conditions (such as different loads and different speeds) and overall path tracking accuracy.

[0075] To achieve the above objectives, this application also provides a control system for steering a guided vehicle. Figure 2 This application discloses a schematic diagram of the control system structure for steering of a guided vehicle according to an embodiment of the present application, as shown below. Figure 2 As shown, the steering control system of the guided vehicle includes an acquisition module, a processing module 103, and a drive module 104.

[0076] Figure 3 A schematic flowchart of a steering control method for a guided vehicle according to an embodiment of this application is disclosed below. Figure 2and Figure 3 The control method and system for steering the guided vehicle provided in this application are further described.

[0077] The acquisition module is used to acquire the desired steering angle and desired angular acceleration of the guided vehicle, as well as the actual steering angle.

[0078] The acquisition module includes a navigation interface module 101 and a state awareness module 102.

[0079] The upper-level navigation system 201 of the AGV generates the desired turning angle command based on a preset path or real-time task planning. The input terminal of the navigation interface module 101 is connected to the upper-level navigation system 201 and is used to receive the desired turning angle θ_d and desired angular acceleration α_d from the navigation system. The angular acceleration α_d can be obtained by the navigation system 201 through differential calculation of the desired path, or it can be directly given by the planning algorithm.

[0080] The input terminal of the state perception module 102 is connected to the angle sensor 202, which is used to obtain the actual steering angle θ_a of the AGV. The angle sensor 202 is installed on the steering shaft of the AGV and can collect the actual steering angle θ_a in real time. The hardware for actually sensing the angle can be an absolute encoder (also called an angle encoder).

[0081] Processing module 103, connected to the acquisition module, is used to determine the steering angle deviation based on the desired steering angle and the actual steering angle, and to determine the PID feedback control quantity and the threshold feedforward compensation quantity of the steering proportional valve dead zone based on the steering angle deviation. Determine the angular acceleration feedforward compensation amount based on the desired angular acceleration; The final control quantity is obtained by superimposing the PID feedback control quantity, the threshold feedforward compensation quantity, and the angular acceleration feedforward compensation quantity.

[0082] The processing module 103, as the "brain" of the system, may include a PID calculation unit 1031, a dead zone feedforward calculation unit 1032, an angular acceleration feedforward calculation unit 1033, and a superposition unit 1034.

[0083] The deviation calculation node receives the difference between the expected steering angle θ_d and the actual steering angle θ_a to determine the steering angle deviation e.

[0084] The PID calculation unit 1031 is used to perform PID calculations on the steering angle deviation e. Specifically, based on preset proportional coefficient Kp, integral coefficient Ki, and derivative coefficient Kd, it performs proportional, integral, and derivative calculations on the deviation e to generate a basic PID feedback control quantity U_pid, where U_pid = Kp + Ki / s + Kd. s, where s is a complex variable in the Laplace transform, and the role of U_pid is to eliminate steady-state error and suppress unknown disturbances.

[0085] The dead zone feedforward calculation unit 1032 internally presets a small deviation threshold E0 and a proportional valve dead zone threshold U_th, and receives the steering angle deviation e. When the system determines that steering initiation is required to overcome static error (i.e., |e|>E0), the unit determines the threshold feedforward compensation amount U_ff1 of the steering proportional valve dead zone based on the direction of the steering angle deviation and the preset proportional valve dead zone threshold.

[0086] That is, output a compensation amount of fixed amplitude U_ff1=sign(e) U_th, where sign(e) is the sign function, ensuring that the direction of the compensation amount is consistent with the desired turning direction; when |e|≤E0, U_ff1=0.

[0087] In one embodiment, the dead-time feedforward calculation unit 1032 further includes: Obtain the last effective control direction of the guided vehicle, and determine the current required direction based on the current steering angle deviation; Based on the comparison between the current demand direction and the previous effective control direction, determine whether to adjust the threshold feedforward compensation amount of the dead zone of the steering proportional valve.

[0088] In this embodiment, the dead zone feedforward calculation unit 1032 is further optimized. The core processing module 103 records the last effective control direction Dir_last and determines the current required direction Dir_curr based on the current steering angle deviation e.

[0089] When the current demand direction Dir_curr is consistent with the previous effective control direction Dir_last, it indicates that the system is in a continuous control process in the same direction, and the dead zone of the proportional valve may have been overcome. At this time, the dead zone threshold feedforward compensation amount can be reduced or the dead zone threshold feedforward compensation amount can be omitted.

[0090] When the current demand direction Dir_curr is inconsistent with the last effective control direction Dir_last, it indicates that the system may have reversed direction or started from a standstill. At this time, the dead zone threshold feedforward compensation amount is determined based on the current demand direction and the proportional valve dead zone threshold.

[0091] Furthermore, the dead zone threshold feedforward compensation amount can be: Uff1 = Dir_curr × Uth × Kadj; Kadj is an adjustment coefficient used to compensate for changes in dead zone characteristics caused by factors such as oil temperature and pressure. It is usually an adjustment coefficient between 0.8 and 1.2.

[0092] This optimization makes the control process smoother, injecting compensation only when dead zones or direction changes need to be overcome.

[0093] The angular acceleration feedforward calculation unit 1033 receives the desired angular acceleration α_d output by the navigation interface module 102, and presets a feedforward gain coefficient K_ff, which is used to multiply the desired angular acceleration by the preset feedforward gain coefficient to obtain the angular acceleration feedforward compensation amount U_ff2. That is, the angular acceleration feedforward compensation amount U_ff2=K_ff α_d, thereby significantly improving dynamic response speed and reducing tracking lag. K_ff is obtained through system identification or experimental calibration, and its physical meaning is to map the angular acceleration requirement into the pre-control quantity of the proportional valve.

[0094] In one embodiment, the angular acceleration feedforward calculation unit 1033 further includes: Obtain the load status of the guided vehicle; The feedforward gain coefficient is adjusted according to the load condition, and the angular acceleration feedforward compensation amount is determined based on the adjusted feedforward gain coefficient.

[0095] In this embodiment, an adaptive method for determining the angular acceleration feedforward compensation amount is further provided.

[0096] The AGV can be configured with a load detection module to obtain the current load status of the AGV. The core processing module 103 adjusts the feedforward gain coefficient Kff according to the load status.

[0097] For example, the feedforward gain coefficient Kff can be determined as follows: Kff=Kff0×(1+β M / M0); Where Kff0 is the reference feedforward gain under no-load conditions, M represents the current load, M0 represents the reference load, and β represents the calibration coefficient.

[0098] When the AGV is heavily loaded, the inertia of the steering system increases. By increasing or adjusting the feedforward gain coefficient, the angular acceleration feedforward compensation can be matched with the actual load state, thereby maintaining a more consistent steering dynamic response.

[0099] The superposition unit 1034 is used to superimpose the PID feedback control quantity U_pid, the threshold feedforward compensation quantity U_ff1, and the angular acceleration feedforward compensation quantity U_ff2 to obtain the final control quantity U_final.

[0100] Figure 4 This application discloses a schematic diagram of the final control quantity synthesis and proportional valve drive signal flow in one embodiment of the present application, combined with... Figure 2 ,3 As shown in Figure 4, the superimposed unit 1034 ( Figure 4 The control inputs from the three channels are combined: U_final = U_pid + U_ff1 + U_ff2. The final control command is then sent to the driver module 104.

[0101] The final control value U_final is a signed numerical value, where the sign represents the steering direction (positive for left turn, negative for right turn), and the magnitude represents the control strength.

[0102] The input terminal of the drive module 104 is connected to the superposition unit 1034 of the core processing module 103, and receives the final control quantity U_final. It is used to convert the final control quantity into a high-power drive signal output according to the magnitude and direction of the final control quantity, so as to drive the steering actuator of the guided vehicle to achieve steering.

[0103] The drive output module 104 typically includes a power amplifier circuit that converts U_final into a PWM signal or analog current signal that can directly drive the proportional valve. This drive signal is applied to the electromagnet coil of the steering proportional valve 105.

[0104] The input end of the steering proportional valve 105 is connected to the drive output module 104 to receive the drive signal. It drives the valve core to move through electromagnetic force, thereby controlling the hydraulic or pneumatic oil circuit. The hydraulic energy output by the proportional valve drives the steering actuator 106 (such as a steering cylinder or motor), which in turn drives the steering wheel of the AGV to achieve the steering action of the wheel.

[0105] The steering control system of the guided vehicle provided in this application forms a closed loop: the action of the steering actuator changes the wheel angle, which is detected by the angle sensor 202 to obtain the actual steering angle θ_a, and is fed back to the state perception module 101 to perform deviation calculation (e=θ_d-θ_a), thus forming closed-loop control, thereby achieving accurate tracking of the desired steering angle θ_d.

[0106] The steering control method and system for a guided vehicle provided in this application have the following significant advantages: (1) By introducing angular acceleration feedforward compensation (U_ff2), the system can react in advance to known and upcoming dynamic changes in steering, which is equivalent to providing "foresight" for the PID controller. This enables the AGV to drive the steering mechanism almost synchronously when accelerating to turn or tracking a changing path, fundamentally reducing the lag caused by pure feedback delay, greatly improving the dynamic response speed, and eliminating the lag phenomenon.

[0107] (2) By introducing threshold feedforward compensation (U_ff1) based on dead zone characteristics, a control quantity sufficient to overcome the dead zone is actively injected when the system needs to overcome steady-state error to start action. This allows the proportional coefficient Kp in the PID controller to be set at a more optimal value focused on dynamic adjustment without having to set an excessively large value in order to "pry up" the dead zone. This perfectly solves the parameter setting contradiction between "insensitivity to small deviations" and "easy overshooting to large deviations", enabling the system to maintain a fast and stable response throughout the entire stroke. It effectively solves the control contradiction caused by the dead zone of the proportional valve and achieves smooth and fast full-range control.

[0108] (3) By combining feedback control with feedforward control, feedback (PID) is responsible for eliminating steady-state error and suppressing unknown disturbances, while feedforward (U_ff1, U_ff2) is responsible for handling known system nonlinearity and predictable dynamic commands, which significantly improves the system's adaptability to different operating conditions (such as different loads and different speeds) and the overall path tracking accuracy, thereby enhancing the system's adaptability and control accuracy.

[0109] (4) By preheating and holding the proportional valve when there is no steering requirement (U_hold), the static friction of the valve core is effectively reduced, ensuring that the steering actuator is always in a "standby" state, so that the system can respond to small commands in an instant, and further optimize the control quality under low speed or fine-tuning conditions.

[0110] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0111] Furthermore, the terms “up,” “down,” “left,” “right,” “top,” “bottom,” “horizontal,” and “vertical” used in the following description should be understood as the orientations shown in the paragraph and related figures. This relative terminology is for illustrative purposes only and does not imply that the described device must be manufactured or operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0112] It is understood that although terms such as "first," "second," and "third" may be used herein to describe various components, regions, layers, and / or parts, these components, regions, layers, and / or parts should not be limited by these terms, and these terms are only used to distinguish different components, regions, layers, and / or parts. Therefore, the first component, region, layer, and / or part discussed below may be referred to as the second component, region, layer, and / or part without departing from some embodiments of this application.

[0113] Those skilled in the art will understand that information, signals, and data can be represented using any of a variety of different techniques and skills. For example, the data, instructions, commands, information, signals, bits, symbols, and chips described throughout the above description can be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, light fields or optical particles, or any combination thereof.

[0114] Those skilled in the art will further appreciate that the various illustrative logic blocks, modules, circuits, and algorithm steps described in conjunction with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or a combination of both. To clearly illustrate this interchangeability between hardware and software, the various illustrative components, blocks, modules, circuits, and steps are described above in a generalized manner in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. Those skilled in the art may implement the described functionality in different ways for each specific application, but such implementation decisions should not be construed as departing from the scope of the invention.

[0115] The various illustrative logic modules and circuits described in conjunction with the embodiments disclosed herein may be implemented or performed using a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The general-purpose processor may be a microprocessor, but in alternatives, it may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors cooperating with a DSP core, or any other such configuration.

[0116] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of both. The software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to a processor such that the processor can read and write information to / from the storage medium. In an alternative, the storage medium may be integrated into the processor. The processor and storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In an alternative, the processor and storage medium may reside as discrete components in the user terminal.

[0117] In one or more exemplary embodiments, the described functionality may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software as a computer program product, the functionality may be stored or transmitted as one or more instructions or code on or through a computer-readable medium. A computer-readable medium includes both computer storage media and communication media, encompassing any medium that facilitates the transfer of a computer program from one location to another. A storage medium may be any available medium accessible to a computer. By way of example and not limitation, such a computer-readable medium may include RAM, ROM, EEPROM, CD-ROM or other optical disc storage, disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and is accessible to a computer. Any connection is also legitimately referred to as a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of a medium. As used in this article, disk and disc include compact discs (CDs), laser discs, optical discs, digital multi-purpose discs (DVDs), floppy disks, and Blu-ray discs. Disks typically reproduce data magnetically, while discs reproduce data optically using lasers. Combinations of these should also be included within the scope of computer-readable media.

[0118] The basic concepts have been described above. Obviously, for those skilled in the art, the above disclosure is merely illustrative and does not constitute a limitation of this application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this application. Such modifications, improvements, and corrections are suggested in this application, and therefore remain within the spirit and scope of the exemplary embodiments of this application.

[0119] Furthermore, this application uses specific terms to describe embodiments of the application. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic related to at least one embodiment of the application. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "an alternative embodiment" mentioned twice or more in different locations in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0120] In some embodiments, numbers describing the quantity of components and attributes are used. It should be understood that such numbers used to describe embodiments are sometimes modified by the terms "approximately," "approximately," or "generally." Unless otherwise stated, "approximately," "approximately," or "generally" indicates that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in this application are approximate values, which may be changed depending on the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant digits and employ a general method of digit reservation. Although the numerical ranges and parameters used to confirm their breadth of range in some embodiments of this application are approximate values, in specific embodiments, such values ​​are set as precisely as feasible.

Claims

1. A control method for steering a guided vehicle, characterized in that, include: Obtain the desired steering angle, desired angular acceleration, and actual steering angle of the guided vehicle; The steering angle deviation is determined based on the expected steering angle and the actual steering angle, and the PID feedback control quantity and the threshold feedforward compensation quantity of the steering proportional valve dead zone are determined based on the steering angle deviation. Determine the angular acceleration feedforward compensation amount based on the desired angular acceleration; The PID feedback control quantity, the threshold feedforward compensation quantity, and the angular acceleration feedforward compensation quantity are superimposed to obtain the final control quantity, and the steering actuator of the guided vehicle is driven to achieve steering based on the magnitude and direction of the final control quantity.

2. The steering control method for a guided vehicle as described in claim 1, characterized in that, The step of determining the steering angle deviation based on the desired steering angle and the actual steering angle, and determining the PID feedback control quantity and the threshold feedforward compensation quantity for the dead zone of the steering proportional valve based on the steering angle deviation, further includes: The steering angle deviation is determined based on the difference between the desired steering angle and the actual steering angle, and a PID calculation is performed on the steering angle deviation to obtain the PID feedback control quantity.

3. The steering control method for a guided vehicle as described in claim 1, characterized in that, The step of determining the steering angle deviation based on the desired steering angle and the actual steering angle, and determining the PID feedback control quantity and the threshold feedforward compensation quantity for the dead zone of the steering proportional valve based on the steering angle deviation, further includes: The threshold feedforward compensation amount of the steering proportional valve dead zone is determined based on the direction of the steering angle deviation and the preset proportional valve dead zone threshold.

4. The steering control method for a guided vehicle as described in claim 3, characterized in that, The step of determining the threshold feedforward compensation amount for the steering proportional valve dead zone based on the steering angle deviation and the preset proportional valve dead zone threshold further includes: When the absolute value of the steering angle deviation is greater than a first preset deviation threshold, the threshold feedforward compensation amount of the steering proportional valve dead zone is determined based on the steering angle deviation and the preset proportional valve dead zone threshold. The direction of the threshold feedforward compensation is consistent with the direction of the steering angle deviation.

5. The steering control method for a guided vehicle as described in claim 1, characterized in that, The step of determining the angular acceleration feedforward compensation amount based on the desired angular acceleration further includes: The desired angular acceleration is multiplied by the preset feedforward gain coefficient to obtain the angular acceleration feedforward compensation amount.

6. The steering control method for a guided vehicle as described in claim 1, characterized in that, The step of controlling the steering actuator of the guided vehicle to achieve steering based on the magnitude and direction of the final control quantity further includes: When the final control quantity is a first direction control quantity, the absolute value of the final control quantity is output to the first steering proportional valve; When the final control quantity is a second direction control quantity, the absolute value of the final control quantity is output to the second steering proportional valve; The first steering proportional valve and the second steering proportional valve are used to drive the guided vehicle to turn in two opposite directions, respectively.

7. The steering control method for a guided vehicle as described in claim 1, characterized in that, Also includes: When the guided vehicle meets the preset no-steering requirement condition, a holding control quantity is output to the steering proportional valve, so that the steering proportional valve is in a pre-action state.

8. The method as described in claim 7, characterized in that, The preset no-steering-requirement conditions include: The absolute value of the steering angle deviation is less than the second preset deviation threshold, and the desired angular acceleration is zero.

9. The steering control method for a guided vehicle as described in claim 1, characterized in that, Also includes: Obtain the last effective control direction of the guided vehicle, and determine the current required direction based on the current steering angle deviation; Based on the comparison between the current demand direction and the previous effective control direction, determine whether to adjust the threshold feedforward compensation amount of the dead zone of the steering proportional valve.

10. The steering control method for a guided vehicle as described in claim 5, characterized in that, Also includes: Obtain the load status of the guided vehicle; The feedforward gain coefficient is adjusted according to the load condition, and the angular acceleration feedforward compensation amount is determined based on the adjusted feedforward gain coefficient.

11. A control system for steering a guided vehicle, characterized in that, include: The acquisition module is used to acquire the desired steering angle, desired angular acceleration, and actual steering angle of the guided vehicle. The processing module, connected to the acquisition module, is used to determine the steering angle deviation based on the desired steering angle and the actual steering angle, and to determine the PID feedback control quantity and the threshold feedforward compensation quantity for the dead zone of the steering proportional valve based on the steering angle deviation. Determine the angular acceleration feedforward compensation amount based on the desired angular acceleration; The final control quantity is obtained by superimposing the PID feedback control quantity, the threshold feedforward compensation quantity, and the angular acceleration feedforward compensation quantity. The drive module is used to drive the steering actuator of the guided vehicle to achieve steering based on the magnitude and direction of the final control quantity.

12. The steering control system for the guided vehicle as described in claim 11, characterized in that, The processing module includes a PID calculation unit, a dead-zone feedforward calculation unit, an angular acceleration feedforward calculation unit, and a superposition unit. The PID calculation unit is used to determine the steering angle deviation based on the difference between the desired steering angle and the actual steering angle, and to perform PID calculation on the steering angle deviation to obtain the PID feedback control quantity. The dead zone feedforward calculation unit is used to determine the threshold feedforward compensation amount of the steering proportional valve dead zone based on the direction of the steering angle deviation and the preset proportional valve dead zone threshold. The angular acceleration feedforward calculation unit is used to multiply the desired angular acceleration by a preset feedforward gain coefficient to obtain the angular acceleration feedforward compensation amount. The superposition unit is used to superimpose the PID feedback control quantity, the threshold feedforward compensation quantity, and the angular acceleration feedforward compensation quantity to obtain the final control quantity.

13. The steering control system for the guided vehicle as described in claim 12, characterized in that, The dead-zone feedforward calculation unit further includes: Obtain the last effective control direction of the guided vehicle, and determine the current required direction based on the current steering angle deviation; Based on the comparison between the current demand direction and the previous effective control direction, determine whether to adjust the threshold feedforward compensation amount of the dead zone of the steering proportional valve.

14. The steering control system for the guided vehicle as described in claim 12, characterized in that, The angular acceleration feedforward calculation unit also includes: Obtain the load status of the guided vehicle; The feedforward gain coefficient is adjusted according to the load condition, and the angular acceleration feedforward compensation amount is determined based on the adjusted feedforward gain coefficient.

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