Articulated vehicle yaw stability control method and system based on trailer active steering

Abstract

The present invention provides a yaw stability control method and system for an articulated vehicle based on active trailer steering, comprising a feedforward controller that solves the trailer's feedforward control angle based on the differential equations of motion of the tractor and trailer, the front wheel angle input, and steady-state conditions, and solves the steady-state motion state using the articulated vehicle system state equation. A feedback controller solves the trailer's feedback control angle using a linear quadratic regulator based on the error between the current vehicle state and the steady-state motion state. The controller outputs the trailer angle, which is the sum of the trailer's feedforward control angle and the feedback control angle. A trailer steering actuator implements the trailer angle output by the controller. The present invention can improve the lateral stability of an articulated vehicle, effectively suppress trailer shimmy when the articulated vehicle is traveling at medium and high speeds, and provide the vehicle system with sufficient stability margin. It also assists the articulated vehicle in steering to a certain extent, improving the vehicle's handling stability and driving safety.

Description

Technical Field

[0001] The present invention relates to the technical field of transport systems and control thereof, in particular to a yaw stabilization control method and system for an articulated vehicle based on active trailer steering. Background Art

[0002] An articulated vehicle system consists of a tractor and trailer connected by an articulated joint (such as a saddle). Common examples include full trailers, semi-trailers, and electric mining shovels. Due to their low transportation costs, high efficiency, and flexible and diverse tractor and trailer combinations, articulated vehicles are widely used in logistics, agricultural production, mineral mining, and other fields, becoming an indispensable means of transportation in production and daily life.

[0003] However, the articulated vehicle system has the coupling of motion between multiple vehicle bodies, and its dynamic behavior is more complex and difficult to control, especially when driving at high speeds, it is easy to have lateral oscillations, causing dangerous vehicle behaviors such as trailer tail-spinning and rollover, which seriously affects road safety. With the rapid development of computer technology and control technology, the leap in controllers and computer hardware has enabled vehicle active control technologies such as active steering and active braking to be implemented and applied on passenger cars. At present, the stability control of articulated vehicles is mainly achieved by applying a braking torque to the trailer to suppress the oscillation of the vehicle body. This method will affect the longitudinal speed of the vehicle system, and the trailer wheel braking is difficult to cope with operations such as changing lanes and avoiding obstacles. The purpose of the present invention is to propose an active steering control system for an articulated vehicle trailer, which relies on the dynamic coupling relationship between the trailer and the tractor, and improves the lateral stability of the articulated vehicle system without affecting the normal driving of the vehicle, and effectively suppresses the oscillation of the trailer when the articulated vehicle system is driving at medium and high speeds, so that the vehicle system has sufficient stability margin, while assisting the steering of the articulated vehicle to a certain extent, and improving the handling stability and driving safety of the articulated vehicle. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of the present invention is to propose an articulated vehicle yaw stability control method and system based on active trailer steering, which can improve the lateral stability of the articulated vehicle and effectively suppress the yaw phenomenon of the trailer when the articulated vehicle is traveling at medium and high speeds, so that the vehicle system has sufficient stability margin. At the same time, it assists the articulated vehicle in steering to a certain extent, improves the handling stability and driving safety of the articulated vehicle, and enables the trailer to easily cope with operations such as lane changing and obstacle avoidance.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] The method for controlling yaw stability of an articulated vehicle based on active trailer steering comprises the following steps:

[0007] A variety of sensors measure the motion state of the articulated vehicle, construct the motion differential equations of the tractor and trailer, and the state equation of the articulated vehicle system;

[0008] The feedforward controller calculates the trailer's feedforward control angle based on the differential equations of motion for the tractor and trailer, the front wheel angle input, and the steady-state conditions. The steady-state motion state is calculated using the articulated vehicle system's state equation. The feedback controller calculates the trailer's feedback control angle using a linear quadratic regulator based on the error between the current vehicle state and the steady-state motion state. The controller outputs the trailer angle, which is the sum of the trailer's feedforward control angle and the feedback control angle.

[0009] The trailer steering actuator drives the trailer axle to realize the trailer steering according to the trailer angle output by the controller.

[0010] Furthermore, the differential equation of motion of the tractor is:

[0011]

[0012] The differential equation of motion of the trailer is:

[0013]

[0014] Among them, v y1 is the longitudinal speed of the tractor, v y2 is the longitudinal speed of the trailer, is the yaw angular velocity of the tractor, is the trailer's yaw rate, is the pulling angular velocity, θ h is the traction angle, A, B w and B t are coefficient matrices, δ w (t) is the front wheel turning angle of the tractor, δ tff (t) is the feedforward control angle, m1 and m2 are the curb weights of the tractor and trailer, and C af1 、C ar1 、C a2 is the lateral stiffness of the front axle of the tractor, the lateral stiffness of the rear axle of the tractor, and the lateral stiffness of the axle of the trailer, l f1 、l r1 、l a2 The distance from the front axle of the tractor to the center of gravity of the tractor, the distance from the rear axle of the tractor to the center of gravity of the tractor, and the distance from the axle of the trailer to the center of gravity of the trailer, l h1 、l h2 I is the distance from the center of gravity of the tractor and trailer to the articulation point. z1 , I z2 is the yaw moment of inertia of the tractor and trailer, v x is the lateral speed of the tractor and trailer.

[0015] Furthermore, according to the balance of lateral force and moment of the tractor and trailer axles, the state variables are selected as Construct the state equation of the articulated vehicle system:

[0016]

[0017] in:

[0018] A=M -1 D, B w =M -1 E, B t =M -1 F;

[0019]

[0020]

[0021]

[0022]

[0023] Furthermore, the control objective of the feedforward controller is to make the current motion state of the tractor and trailer meet the steady-state condition by increasing the trailer turning angle, and the yaw angular velocity of the tractor and trailer is equal. When the vehicle system is in a steady-state state, the yaw angular velocity of the tractor and the trailer is a constant value, the acceleration of the yaw angular velocity of the tractor and the trailer is 0, the acceleration of the lateral velocity of the tractor and the trailer is 0, the sideslip angle of the center of mass is 0, and the traction angle θ is 0. h The trailer's feedforward control angle δ is calculated by solving the motion differential equations of the tractor and trailer. tff The expression of (t) is:

[0024]

[0025] Among them, m1 and m2 are the curb weights of the tractor and trailer, C af1 、C ar1 、C a2 is the lateral stiffness of the front axle of the tractor, the lateral stiffness of the rear axle of the tractor, and the lateral stiffness of the axle of the trailer, l f1 、l r1 、l a2 The distance from the front axle of the tractor to the center of gravity of the tractor, the distance from the rear axle of the tractor to the center of gravity of the tractor, and the distance from the axle of the trailer to the center of gravity of the trailer, l h1 、l h2 I is the distance from the center of gravity of the tractor and trailer to the articulation point. z1 , I z2 is the yaw moment of inertia of the tractor and trailer, v xis the lateral velocity of the tractor and trailer, δ w (t) is the front wheel turning angle of the tractor.

[0026] Furthermore, the feedback controller uses a linear quadratic regulator to solve the optimal control result of the trailer angle based on the error between the current motion state and the steady-state motion state. When the system enters the steady-state state, the state equation of the articulated vehicle system is: The state variable at this time is the ideal motion state x for feedback control. des (t), defined as:

[0027] x des (t) = -A -1 B w δ w (t)

[0028] The method for solving the feedback control angle through the linear quadratic regulator is:

[0029] The state error is defined as:

[0030] e(t)=x(t)-xd es (t)

[0031] The cost function of the linear quadratic regulator is expressed as:

[0032]

[0033] Take the weight matrix Q, R as:

[0034]

[0035] By solving the Riccati equation, we get the feedback control coefficient matrix k(t) = [k1 k2 k3 k4];

[0036] The feedback control angle of the trailer obtained by solving the feedback controller is:

[0037] δ tfb (t) = k(t)*e(t).

[0038] Furthermore, it also includes:

[0039] The architecture of feedforward open-loop control plus feedback closed-loop control is adopted. The trailer steering angle signal output by the controller is the sum of the steering angle solved by the feedforward controller and the steering angle solved by the feedback controller. The expression is:

[0040] δ t (t) = δ tff (t)+δ tfb (t)

[0041] Among them, δ t(t) is the trailer turning angle, δ tff (t) is the feedforward control angle, δ tfb (t) is the feedback control angle;

[0042] The first-order exponential smoothing method is used to reduce the noise of the controller in solving the trailer angle. The specific method is as follows:

[0043] Take the sampling period T s , the trailer turning angle δ solved by the controller t (t) is discretized to obtain δ t (k), k is the kth moment, and t=k*T s , the final trailer turning angle δ of the k+1th sampling period obtained by exponential smoothing p (k+1) is:

[0044] δ p (k+1)=s*δ t (k+1)+(1-s)δ p (k), δ p (0) = δ t (0)

[0045] Among them, δ p (k) is the final trailer turning angle obtained by exponential smoothing method in the kth sampling period, δ t (k+1) is the trailer turning angle solved by the controller in the k+1th sampling period, and s is the smoothing coefficient.

[0046] The articulated vehicle yaw stability control system based on trailer active steering is applied to the above-mentioned articulated vehicle yaw stability control method based on trailer active steering, comprising:

[0047] A state measurement module, used for measuring the motion state of the articulated vehicle through a variety of sensors;

[0048] An in-vehicle communication module for transmitting the motion status of the articulated vehicle to the controller via the controller area network communication bus for data processing;

[0049] The controller includes a feedforward controller and a feedback controller. The feedforward controller solves the feedforward control angle of the trailer based on the differential equations of motion of the tractor and trailer, the front wheel angle input, and the steady-state condition. The feedback controller solves the steady-state motion state through the state equation of the articulated vehicle system based on the error between the current vehicle state and the steady-state motion state, and solves the feedback control angle of the trailer through a linear quadratic regulator. The controller outputs the trailer angle that is the sum of the feedforward control angle and the feedback control angle.

[0050] The trailer steering actuator is used to drive the trailer axle to steer the trailer according to the trailer angle output by the controller.

[0051] Furthermore, the trailer steering actuator is an electric-driven steering actuator, which includes an electronic control unit, a steering drive motor, a reducer, and a rack-and-pinion steering gear. The electronic control unit is electrically connected to the steering drive motor, the reducer is connected to the output shaft of the steering drive motor, and the rack-and-pinion steering gear is connected to the output shaft of the reducer and drives the trailer to steer. After receiving the filtered trailer angle signal, the electronic control unit calculates the torque required by the steering drive motor. After the reducer decelerates, the trailer axle is driven through the rack-and-pinion steering gear to achieve steering. For the steering drive motor, its dynamic equation is:

[0052]

[0053] Where, J m is the moment of inertia of the driving motor, θ m is the motor angle, B m is the equivalent damping coefficient of the drive motor and reducer, K m is the torsional stiffness of the driving motor, f is the steering equivalent friction torque acting on the motor and the reducer, i is the reduction ratio of the reducer, T m Output torque of the steering motor; T r is the aligning torque, and for the motor angle θ m =Gδ p , where G is the equivalent transmission ratio of the steering system.

[0054] Furthermore, the trailer steering actuator is a trailer hydraulically driven steering actuator, which includes an electronic control unit, an oil storage tank, a steering oil pump, a rotary valve and a circulating ball steering gear. When the electronic control unit receives the trailer angle signal, the steering oil pump works to output high-pressure oil with corresponding flow and pressure to the rotary valve. The rotary valve creates a pressure difference at both ends of the hydraulic cylinder, pushes the piston to move, and then drives the trailer axle to steer through the circulating ball steering gear.

[0055] Furthermore, the sensors in the state measurement module include:

[0056] Steering wheel angle sensor, used to obtain the steering wheel angle δ s (t);

[0057] GPS, used to obtain the longitudinal speed v of the tractor y1 , trailer longitudinal speed v y2 , lateral speed v of the tractor x ;

[0058] Tractor yaw rate sensor, used to obtain the yaw rate of the tractor

[0059] Trailer yaw angular velocity sensor, used to obtain the trailer's yaw angular velocity

[0060] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0061] (1) A control architecture of feedforward control plus feedback control is adopted. The feedforward controller obtains the desired trailer angle based on the input of the steering wheel angle, and the feedback controller obtains the feedback control angle output based on the solution of the vehicle system state error; (2) The feedforward controller solves the trailer angle requirement in the steady state based on the steering wheel angle input and the dynamic equations of the tractor and trailer, suppresses the trailer's swing amplitude to a certain extent, and assists the driver in completing vehicle lane changes, obstacle avoidance and other operations; (3) The feedback controller obtains the full state error between the current motion state and the desired state based on the three-degree-of-freedom model of the articulated vehicle, and obtains the optimal control result of the trailer angle through the linear quadratic regulator, thereby obtaining the yaw angular velocity, traction angle, and traction angular acceleration that meet the lateral stability of the vehicle system. Feedback control enables articulated vehicles to maintain lateral stability over a wide speed range, giving the vehicle system sufficient stability margin. (4) When executing the steering requirements solved by the controller, the trailer steering actuator uses exponential smoothing to make the final trailer turning angle execution smoother, allowing the vehicle system to maintain lateral stability while improving driving smoothness. The steering drive motor directly drives the steering rack through the reducer, improving transmission efficiency and system rigidity, and can provide a larger steering torque for trailer steering. For heavy trailers, the trailer should adopt a hydraulic actuator steering mechanism to provide a larger steering torque. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The accompanying drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0063] Figure 1 Schematic diagram of the yaw stability control method for an articulated vehicle according to the present invention.

[0064] Figure 2 This is a working block diagram of the present invention.

[0065] Figure 3 This is the control flow chart of the trailer steering feedback control.

[0066] Figure 4 Schematic diagram of the steering of an articulated vehicle trailer.

[0067] Figure 5 This is a schematic diagram of the trailer's electric drive trailer steering actuator.

[0068] Figure 6 This is a schematic diagram of the trailer hydraulically driven trailer steering actuator. DETAILED DESCRIPTION

[0069] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0070] In the present invention, the term "tractor" refers to the traction vehicle that provides power in an articulated vehicle, such as a truck, a van, a car with an articulated device, etc., and the term "trailer" refers to any vehicle being towed, such as a semi-trailer, a full trailer, a travel trailer, etc.

[0071] Example 1

[0072] Example 1 provides an articulated vehicle yaw stability control method for active trailer steering, such as Figure 1 and Figure 2 As shown, the following steps are included:

[0073] S1. Use multiple sensors to measure the motion state of the articulated vehicle, construct the motion differential equations of the tractor and trailer, and the state equation of the articulated vehicle system;

[0074] S2. The feedforward controller solves the trailer's feedforward control angle based on the differential equations of motion of the tractor and trailer, the front wheel angle input, and the steady-state conditions. The steady-state motion state is solved using the articulated vehicle system state equation. The feedback controller solves the trailer's feedback control angle using a linear quadratic regulator based on the error between the current vehicle state and the steady-state motion state. The controller outputs the trailer angle, which is the sum of the trailer's feedforward control angle and the feedback control angle.

[0075] S3. The trailer steering actuator drives the trailer axle to realize the trailer steering according to the trailer turning angle.

[0076] The articulated vehicle yaw stability control method provided in Example 1 adopts feedforward control plus feedback control to establish the state equation of the articulated vehicle system, and obtain the motion differential equations of the articulated vehicle tractor and trailer, and transmit the motion state information to the controller through the controller local area network communication bus. The feedforward controller calculates the feedforward input of the trailer feedforward control angle based on the motion differential equations of the tractor and trailer, the front wheel angle input and the feedforward control angle of the trailer under steady-state conditions, thereby suppressing the yaw amplitude of the trailer to a certain extent and assisting the driver to complete vehicle lane change, obstacle avoidance and other operations. The feedback control is based on the state equation of the articulated vehicle system. Solve the steady-state motion state, calculate the error between the current vehicle state and the steady-state motion state, and solve the feedback control angle of the trailer through a linear quadratic regulator. Feedback control enables the articulated vehicle to maintain lateral stability in a large speed range, so that the vehicle system has sufficient stability margin. At the same time, it assists the articulated vehicle to achieve steering to a certain extent. The trailer angle is obtained by adding the feedforward control angle and the feedback control angle, so that the trailer steering actuator drives the trailer axle to achieve trailer steering according to the trailer angle, thereby improving the handling stability and driving safety of the articulated vehicle and allowing the trailer wheels to easily cope with operations such as lane changing and obstacle avoidance.

[0077] The yaw stability control method for an articulated vehicle provided in this embodiment is described in detail below.

[0078] In step S1, the longitudinal speed of the tractor v is selected y1 , yaw angular velocity of the tractor Articulation angular velocity Articulation angle θ h For state variables:

[0079]

[0080] The articulation angular velocity is and the yaw rate of the tractor and trailer yaw rate The difference is equivalent, that is Articulation angle θ h By articulation angular velocity Points earned.

[0081] The vehicle model is constructed by assuming that the vehicle is traveling at a constant speed, with small sideslip angles and steering wheel angles. Based on the balance of lateral forces and moments between the tractor and trailer axles, a three-degree-of-freedom monorail model of the articulated vehicle system is constructed, and then the state equation of the articulated vehicle system is constructed:

[0082]

[0083] Among them, A, B w and B t are coefficient matrices, δw (t) is the front wheel angle of the tractor, and is related to the steering wheel angle δ s (t), with δ w (t) = i c δ s (t), steering wheel angle δ s (t) is measured by the steering wheel angle sensor, which is installed on the steering column below the steering wheel of the tractor, where i c is the equivalent angle transmission ratio of the tractor front wheel steering system, δ t (t) is the trailer turning angle to be solved;

[0084] Where A=M -1 D, B w =M -1 E, B t =M -1 F;

[0085] Specifically,

[0086]

[0087]

[0088]

[0089] In the above matrix, m1 and m2 are the curb weights of the tractor and trailer respectively, C df1 、C ar1 、C a2 is the lateral stiffness of the front axle of the tractor, the lateral stiffness of the rear axle of the tractor, and the lateral stiffness of the axle of the trailer, l f1 、l r1 、l a2 The distance from the front axle of the tractor to the center of gravity of the tractor, the distance from the rear axle of the tractor to the center of gravity of the tractor, and the distance from the axle of the trailer to the center of gravity of the trailer, l h1 、l h2 I is the distance from the center of gravity of the tractor and trailer to the articulation point. z1 , I z2 is the yaw moment of inertia of the tractor and trailer, v x is the lateral speed of the tractor and trailer.

[0090] When the system enters the steady state, the state equation of the articulated vehicle system is: The motion state at this time is the ideal motion state x for feedback control. des (t), defined as:

[0091] x des (t) = -A -1 B w δw (t).

[0092] Specifically, a variety of sensors are installed on the articulated vehicle to obtain the motion state of the articulated vehicle, the longitudinal speed v of the tractor, and the y1 Obtained from GPS, the yaw angular velocity of the tractor The yaw rate sensor of the tractor is installed near the center of mass of the tractor body, and the yaw rate of the trailer is obtained by the yaw rate sensor of the tractor. Obtained by the trailer yaw angular velocity sensor, which is installed near the center of mass of the trailer body.

[0093] In step s2, the control objective of the feedforward controller is to increase the trailer's rotation angle so that the current motion state of the tractor and trailer meets the steady-state condition and the yaw angular velocity of the tractor and trailer are equal. Based on the state equation of the articulated vehicle system, the motion differential equations of the tractor and trailer can be obtained respectively. The motion differential equation of the tractor is:

[0094]

[0095] The differential equation of motion of the trailer is:

[0096]

[0097] Among them, v y1 is the longitudinal speed of the tractor, v y2 is the longitudinal velocity of the trailer, v x is the lateral speed of the tractor, is the yaw angular velocity of the tractor, is the trailer's yaw rate.

[0098] Based on the definition of the motion state of the vehicle system in a steady state, when the vehicle system is in a steady state, the yaw angular velocity of the tractor and trailer yaw rate is a constant value, the yaw angular velocity of the tractor and trailer yaw rate The acceleration of the tractor and trailer is 0, the acceleration of the lateral velocity is 0, the sideslip angle of the center of mass is 0, and the terms related to the traction angle are ignored. Therefore, the feedforward control angle expression of the trailer wheel angle can be solved as follows:

[0099] Then in step S2, the trailer feedforward control angle δ tff The expression of (t) is:

[0100]

[0101] Among them, v x is the lateral velocity of the tractor, the lateral velocity of the tractor v xand the longitudinal velocity of the tractor v y1 The differential GPS method is used for measurement, and two GPS antennas are arranged in the direction of the central axis of the tractor roof.

[0102] like Figure 3 As shown, in step S3, a feedback closed-loop control based on a linear quadratic regulator is adopted. The feedback controller uses the linear quadratic regulator to solve the optimal control result of the trailer angle based on the error between the current motion state and the steady-state motion state.

[0103] The state error is defined as:

[0104] e(t)=x(t)-x des (t).

[0105] The cost function of the linear quadratic regulator is expressed as:

[0106]

[0107] Take the weight matrix Q, R as:

[0108]

[0109] By solving the Riccati equation, we can obtain the feedback control coefficient matrix k(t) = [k1 k2 k3 k4].

[0110] Therefore, the trailer turning angle obtained by the feedback controller is:

[0111] δ tfb (t) = k(t)*e(t).

[0112] like Figure 4 The figure shows a schematic diagram of the steering of an articulated vehicle trailer. The present invention adopts a feedforward open-loop control plus feedback closed-loop control architecture. The trailer steering angle signal output by the controller is the sum of the steering angle solved by the feedforward controller and the steering angle solved by the feedback controller, namely:

[0113] δ t (t) = δ tff (t)+δ tfb (t)

[0114] Among them, δ t (t) is the trailer turning angle, δ tff (t) is the feedforward control angle, δ tfb (t) is the feedback control angle.

[0115] The steering angle solved by the feedforward controller is based on the front wheel steering angle of the trailer, which can suppress the trailer's oscillation to a certain extent and assist the driver in completing operations such as lane changing. The steering angle of the feedback controller is obtained based on the system state error, which can improve the handling stability of the articulated vehicle, significantly suppress the trailer's oscillation, and enhance the stability margin of the vehicle system at high speeds.

[0116] In step S2, this embodiment uses a first-order exponential smoothing method to reduce the noise of the controller in solving the trailer's turning angle, so that the turning angle input finally executed by the trailer's steering actuator is smoother. s , the trailer angle signal δ solved by the controller t (t) is discretized to obtain δ t (k), k is the kth moment, and t=k*T s Therefore, the trailer turning angle obtained by exponential smoothing is:

[0117] δ p (k+1)=s*δ t (k+1)+(1-s)δ p (k), δ p (0) = δ t (0)

[0118] Among them, δ p (k) is the trailer turning angle obtained by exponential smoothing method in the kth sampling period, δ t (k+1) is the k+1th sampling period. The controller calculates the trailer steering angle of the trailer equipped with an electric trailer steering actuator or a hydraulic trailer steering actuator.

[0119] When executing the steering requirements solved by the controller, the trailer steering actuator uses exponential smoothing to make the final trailer turning angle execution smoother, allowing the vehicle system to maintain lateral stability while improving driving smoothness.

[0120] Example 2

[0121] Embodiment 2 provides an articulated vehicle yaw stabilization control system based on trailer active steering, which is applied to the above-mentioned articulated vehicle yaw stabilization control method based on trailer active steering, including:

[0122] A state measurement module, used to measure the motion state of the articulated vehicle;

[0123] The in-vehicle communication module is used to transmit the vehicle body motion status measured by the sensor to the controller through the controller area network communication bus for data processing;

[0124] The controller includes a feedforward controller and a feedback controller. The feedforward controller solves the feedforward control angle of the trailer based on the differential equations of motion of the tractor and trailer, the front wheel angle input, and the steady-state condition. The feedback controller solves the steady-state motion state through the state equation of the articulated vehicle system based on the error between the current vehicle state and the steady-state motion state, and solves the feedback control angle of the trailer through a linear quadratic regulator. The controller outputs the trailer angle that is the sum of the feedforward control angle and the feedback control angle.

[0125] The trailer steering actuator is an electric or hydraulically driven steering actuator. The electronic control unit receives the trailer angle signal obtained by feedforward and feedback control from the controller LAN communication bus. After filtering, it calculates the torque or hydraulic pressure required to execute the steering. The motor or steering oil pump starts to run, driving the electric or hydraulically driven steering actuator to execute the trailer steering.

[0126] Trailers equipped with electric or hydraulic steering actuators use a steering drive motor that directly drives the steering rack through a speed reducer, improving transmission efficiency and system rigidity while providing greater steering torque. For heavy trailers, a hydraulically-actuated steering actuator is recommended to provide greater steering torque.

[0127] like Figure 5 The figure shows a schematic diagram of an electric-driven trailer steering actuator. The electric-driven steering actuator is suitable for light trailers such as travel trailers. In this embodiment, the electric-driven steering actuator includes an electronic control unit, a steering drive motor, a reducer and a rack-and-pinion steering gear. The electronic control unit is electrically connected to the steering drive motor, the reducer is connected to the output shaft of the steering drive motor, the rack-and-pinion steering gear is connected to the output shaft of the reducer and drives the trailer to steer, and the steering drive motor and the reducer are installed axially on the steering rack. After receiving the trailer angle signal after filtering, the electronic control unit calculates the torque required for the steering drive motor, the reducer mechanism decelerates and increases the torque, and the motor output torque acts on the rack through the reducer, driving the pull rod to perform the trailer steering operation. For the drive motor, its dynamic equations are:

[0128]

[0129] Where, J m is the moment of inertia of the driving motor, θ m is the motor angle, B m is the equivalent damping coefficient of the drive motor and reducer, K m is the torsional stiffness of the driving motor, f is the steering equivalent friction torque acting on the motor and the reducer, i is the reduction ratio of the reducer, T m Output torque of the steering motor; T r is the aligning torque. For the motor angle, θ m=Gδ p , where G is the equivalent transmission ratio of the steering system.

[0130] like Figure 6 The figure shows a schematic diagram of a hydraulically driven trailer steering actuator. For heavy trailers, the torque provided by the drive motor is insufficient, and a hydraulically driven steering actuator is used to steer the trailer. The hydraulically driven steering actuator is suitable for heavy trailers such as semi-trailers. The hydraulically driven steering actuator of the present invention includes an electronic control unit, an oil storage tank, a steering oil pump, a rotary valve, and a recirculating ball steering gear. When the electronic control unit receives the trailer angle signal, the steering oil pump operates to output high-pressure oil of corresponding flow and pressure to the rotary valve. The rotary valve generates a pressure difference at both ends of the hydraulic cylinder, pushing the piston to move, and then driving the trailer to steer through the recirculating ball steering gear.

[0131] The in-vehicle communication module utilizes a controller area network (CAN) bus that complies with the SAE J1939 protocol. This bus consists of two signal lines, CAN_High and CAN_Low, and uses differential signals for asynchronous communication. It can accommodate multiple communication nodes, each consisting of a CAN controller and transceiver. Node signals are transmitted via the bus, enabling inter-node communication. This protocol can achieve a communication rate of up to 250kbps, with a maximum of 30 subsystems on the same network and a maximum transmission line length of 40 meters.

[0132] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A yaw stability control method for an articulated vehicle based on active trailer steering, characterized in that: The following steps are involved: A variety of sensors measure the motion state of the articulated vehicle, construct the motion differential equations of the tractor and trailer, and the state equation of the articulated vehicle system; The feedforward controller calculates the trailer's feedforward control angle based on the differential equations of motion for the tractor and trailer, the front wheel angle input, and the steady-state conditions. The steady-state motion state is calculated using the articulated vehicle system's state equation. The feedback controller calculates the trailer's feedback control angle using a linear quadratic regulator based on the error between the current vehicle state and the steady-state motion state. The controller outputs the trailer angle, which is the sum of the trailer's feedforward control angle and the feedback control angle. The trailer steering actuator drives the trailer axle to steer the trailer according to the trailer angle output by the controller; The differential equation of motion of the tractor is: The differential equation of motion of the trailer is: Among them, v y1 is the longitudinal speed of the tractor, v y2 is the longitudinal speed of the trailer, is the yaw angular velocity of the tractor, is the trailer's yaw rate, is the pulling angular velocity, θ h is the traction angle, δ w (t) is the front wheel turning angle of the tractor, δ tff (t) is the feedforward control angle, m1 and m2 are the curb weights of the tractor and trailer, and C af1 、C ar1 、C a2 is the lateral stiffness of the front axle of the tractor, the lateral stiffness of the rear axle of the tractor, and the lateral stiffness of the axle of the trailer, l f1 、l r1 、l a2 The distance from the front axle of the tractor to the center of gravity of the tractor, the distance from the rear axle of the tractor to the center of gravity of the tractor, and the distance from the axle of the trailer to the center of gravity of the trailer, l h1 、l h2 I is the distance from the center of gravity of the tractor and trailer to the articulation point. z1 , I z2 is the yaw moment of inertia of the tractor and trailer, v x is the lateral speed of the tractor and trailer.

2. The yaw stability control method for an articulated vehicle based on trailer active steering according to claim 1 is characterized by: According to the balance of lateral force and moment of the tractor and trailer axles, the state variables are selected as Construct the state equation of the articulated vehicle system: A, B w and B t are coefficient matrices; in:

3. The yaw stability control method for an articulated vehicle based on trailer active steering according to claim 1 is characterized in that: The control objective of the feedforward controller is to make the current motion state of the tractor and trailer meet the steady-state condition by increasing the trailer angle, and the yaw angular velocity of the tractor and trailer is equal. When the vehicle system is in a steady-state state, the yaw angular velocity of the tractor and the trailer is a constant value, the acceleration of the yaw angular velocity of the tractor and the trailer is 0, the acceleration of the lateral velocity of the tractor and the trailer is 0, the sideslip angle of the center of mass is 0, and the traction angle θ h The trailer's feedforward control angle δ is calculated by solving the motion differential equations of the tractor and trailer. tff The expression of (t) is: Among them, m1 and m2 are the curb weights of the tractor and trailer, C af1 、C ar1 、C a2 is the lateral stiffness of the front axle of the tractor, the lateral stiffness of the rear axle of the tractor, and the lateral stiffness of the axle of the trailer, l fl 、l r1 、l a2 The distance from the front axle of the tractor to the center of gravity of the tractor, the distance from the rear axle of the tractor to the center of gravity of the tractor, and the distance from the axle of the trailer to the center of gravity of the trailer, l h1 、l h2 I is the distance from the center of gravity of the tractor and trailer to the articulation point. z1 , I z2 is the yaw moment of inertia of the tractor and trailer, v x is the lateral velocity of the tractor and trailer, δ w (t) is the front wheel turning angle of the tractor.

4. The yaw stability control method for an articulated vehicle based on trailer active steering according to claim 2 is characterized in that: The feedback controller uses a linear quadratic regulator to solve the optimal control result of the trailer angle based on the error between the current motion state and the steady-state motion state. When the system enters the steady-state state, the state equation of the articulated vehicle system is: The state variable at this time is the ideal motion state x for feedback control. des (t), defined as: x des (t)=-A -1 B w δ w (t) The method for solving the feedback control angle through the linear quadratic regulator is: The state error is defined as: e(t)=x(t)-x des (t) The cost function of the linear quadratic regulator is expressed as: Take the weight matrix Q, R as: By solving the Riccati equation, we get the feedback control coefficient matrix k(t) = [k1 k2 k3 k4]; The feedback control angle of the trailer obtained by solving the feedback controller is: δ tfb (t)=k(t)*e(t)。 5. The yaw stability control method for an articulated vehicle based on trailer active steering according to claim 1 is characterized in that: Also includes: The architecture of feedforward open-loop control plus feedback closed-loop control is adopted. The trailer steering angle signal output by the controller is the sum of the steering angle solved by the feedforward controller and the steering angle solved by the feedback controller. The expression is: d t (t)=δ tff (t)+δ tfb (t) Among them, δ t (t) is the trailer turning angle, δ tff (t) is the feedforward control angle, δ tfb (t) is the feedback control angle; The first-order exponential smoothing method is used to reduce the noise of the controller in solving the trailer angle. The specific method is as follows: Take the sampling period T s , the trailer turning angle δ solved by the controller t (t) is discretized to obtain δ t (k), k is the kth moment, and t=k*T s , the final trailer turning angle δ of the k+1th sampling period obtained by exponential smoothing p (k+1) is: d p (k+1)=s*δ t (k+1)+(1-s)δ p (k), d p (0)=d t (0) Among them, δ p (k) is the final trailer turning angle obtained by exponential smoothing method in the kth sampling period, δ t (k+1) is the trailer turning angle solved by the controller in the k+1th sampling period, and s is the smoothing coefficient.

6. An articulated vehicle yaw stability control system based on trailer active steering, applied to an articulated vehicle yaw stability control method based on trailer active steering according to any one of claims 1 to 5, characterized in that: include: A state measurement module, used for measuring the motion state of the articulated vehicle through a variety of sensors; An in-vehicle communication module for transmitting the motion status of the articulated vehicle to the controller via the controller area network communication bus for data processing; The controller includes a feedforward controller and a feedback controller. The feedforward controller solves the feedforward control angle of the trailer based on the differential equations of motion of the tractor and trailer, the front wheel angle input and the steady-state condition. The feedback controller calculates the steady-state motion state based on the error between the current vehicle state and the steady-state motion state using the state equation of the articulated vehicle system. The feedback control angle of the trailer is then calculated using a linear quadratic regulator. The controller then outputs the trailer angle, which is the sum of the trailer's feedforward control angle and the feedback control angle. The trailer steering actuator is used to drive the trailer axle to steer the trailer according to the trailer angle output by the controller.

7. The articulated vehicle yaw stability control system based on trailer active steering according to claim 6 is characterized in that: The trailer steering actuator is an electric-driven steering actuator, which includes an electronic control unit, a steering drive motor, a reducer, and a rack-and-pinion steering gear. The electronic control unit is electrically connected to the steering drive motor, the reducer is connected to the output shaft of the steering drive motor, and the rack-and-pinion steering gear is connected to the output shaft of the reducer and drives the trailer to steer. After receiving the filtered trailer angle signal, the electronic control unit calculates the torque required by the steering drive motor. After the reducer decelerates, the trailer axle is driven through the rack-and-pinion steering gear to achieve steering. For the steering drive motor, its dynamic equation is: Where, J m is the moment of inertia of the driving motor, θ m is the motor angle, B m is the equivalent damping coefficient of the drive motor and reducer, K m is the torsional stiffness of the driving motor, f is the steering equivalent friction torque acting on the motor and the reducer, i is the reduction ratio of the reducer, T m Output torque of the steering motor; T r is the aligning torque, and for the motor angle θ m =Gδ p , where G is the equivalent transmission ratio of the steering system.

8. The articulated vehicle yaw stability control system based on trailer active steering according to claim 6 is characterized in that: The trailer steering actuator is a hydraulically driven steering actuator, which includes an electronic control unit, an oil storage tank, a steering oil pump, a rotary valve and a recirculating ball steering gear. When the electronic control unit receives the trailer angle signal, the steering oil pump works to output high-pressure oil with corresponding flow and pressure to the rotary valve. The rotary valve creates a pressure difference at both ends of the hydraulic cylinder, pushes the piston to move, and then drives the trailer axle to steer through the recirculating ball steering gear.

9. The articulated vehicle yaw stability control system based on trailer active steering according to claim 6 is characterized in that: The sensors in the state measurement module include: Steering wheel angle sensor, used to obtain the steering wheel angle δ s (t); GPS, used to obtain the longitudinal speed v of the tractor y1 , trailer longitudinal speed v y2 , lateral speed v of the tractor x ; Tractor yaw rate sensor, used to obtain the yaw rate of the tractor Trailer yaw angular velocity sensor, used to obtain the trailer's yaw angular velocity

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