阅读说明：本技术 一种路径跟踪前馈控制方法和装置 (Path tracking feedforward control method and device ) 是由 秦兆博 陈亮 秦洪懋 边有钢 秦晓辉 谢国涛 王晓伟 徐彪 胡满江 丁荣军 于 2021-07-15 设计创作，主要内容包括：本发明实施例公开了一种路径跟踪前馈控制方法和装置,该方法包括：步骤1,获取车辆状态信息；步骤2,根据所述车辆状态信息,确定用于抵消稳态横向误差的前馈控制量；步骤3,根据得到的所述前馈控制量实现车辆的横向控制。本发明实施例提供的方案中,利用基于打击中心建模的路径跟踪控制系统的稳态误差模型得到的稳态误差表达式,得到可以抵消稳态横向误差的前馈控制量,从而可以消除弯道工况下路径跟踪控制系统的稳态误差,提升路径跟踪精度。(The embodiment of the invention discloses a path tracking feedforward control method and a device, wherein the method comprises the following steps: step 1, obtaining vehicle state information; step 2, determining a feedforward control quantity for counteracting a steady-state lateral error according to the vehicle state information; and 3, realizing the transverse control of the vehicle according to the obtained feedforward control quantity. In the scheme provided by the embodiment of the invention, the steady-state error expression obtained by the steady-state error model of the path tracking control system based on the striking center modeling is utilized to obtain the feedforward control quantity capable of offsetting the steady-state transverse error, so that the steady-state error of the path tracking control system under the curve working condition can be eliminated, and the path tracking precision is improved.)

1. A path-tracking feedforward control method, comprising:

step 1, obtaining vehicle state information;

and 2, determining a feedforward control quantity for counteracting the steady-state lateral error by using the following formula (1) according to the vehicle state information:

wherein, F_{yf_feedforword}Representing a feedforward control quantity, K₃Representing a predetermined scale factor, e_{s_yaw}Representing steady state yaw angle error, c_rDenotes the curvature of the path,/_rRepresenting the distance of the centre of mass from the rear axle, m representing the mass of the vehicle, v_xRepresenting longitudinal vehicle speed, A_xRepresenting longitudinal acceleration, x_copIndicating a vehicle impact center position, L indicating a vehicle wheelbase, δ indicating a front wheel steering angle;

wherein the content of the first and second substances,

wherein l_fIs the distance of the center of mass from the front axis, C_rFor the tire sidewall deflection stiffness, k, of the rear wheel_rCoefficients characterizing the nonlinear characteristics of the tire;

and 3, realizing the transverse control of the vehicle according to the obtained feedforward control quantity.

2. The method of claim 1, wherein K is₃Column 3 elements of the gain matrix are controlled for the system.

3. The method of claim 2, wherein the system control gain matrix is a matrix obtained by an LQR (linear quadratic regulator) system.

4. The method of claim 1, wherein step 3 comprises:

and adding the feedforward control quantity and the feedback control quantity to obtain a final control quantity, and using the final control quantity to realize the transverse control of the vehicle.

5. The method according to claim 4, wherein the feedback control amount is a product of a vehicle state vector and a preset proportionality coefficient.

6. The method of claim 1, wherein the formula (1) is obtained based on the following settings:

is established withFront wheel cornering forces F as vehicle state vectors_yfEquation of state input for system control:

wherein:

in the formula (I), the compound is shown in the specification,representing the derivative of the vehicle state vector, C_rFor the tire sidewall deflection stiffness of the rear wheel, c_rIs the curvature of the path, k_rTo characterize the non-linear behavior of a tire, e_copFor lateral error based on center of vehicle impact, F_yfIs the cornering force of the front wheel, I_zThe moment of inertia of the vehicle about the z-axis, s is the reference path,for course deviation, L ═ L_r+x_cop，v_xFor longitudinal vehicle speed, r yaw rate, l_fIs the distance of the center of mass from the front axis,/_rIs the distance of the center of mass from the rear axis, x_copAs vehiclesA center of impact position;

order to

A state space model for the closed-loop lateral control system under state feedback is obtained:

where K is the system control gain matrix, c_rIs the path curvature.

7. The method of claim 6, wherein step 3 comprises:

the feedback control amount is obtained using the following equation:

F_{yf_feedback}＝-Kx

the feedback control quantity F_{yf_feedback}With said feedforward control quantity F_{yf_feedforword}Summing to obtain the front wheel side deflection force:

F_yf＝F_{yf_feedback}+F_{yf_feedforword}

lateral control of the vehicle is achieved using the front wheel side biasing force.

8. The method of claim 6, wherein the state space model of the closed loop system is represented as:

obtained by Laplace transform and making the initial state of the system be zero

X(s)＝(sI-(A-BK))^-1(BL(F_{yf_feedforword})+DL(c_r))

Wherein, L (F)_{yf_feedforword}) And L (c)_r) Are respectively F_{yf_feedforword}And c_rIs Laplace transform of (x (s)) is offIn the function of the complex variable s, I is an identity matrix;

the feedforward control amount is made constant, and Laplace transformation of the feedforward control amount is performedObtaining a steady-state lateral error:

through sign operation, the steady-state error expression is obtained as follows:

wherein, K_iTo control the ith column element of the gain matrix for the system, A_xIs the longitudinal acceleration;

and obtaining the formula (2) and the formula (1) based on the steady-state error expression.

9. A path-tracking feedforward control device, comprising:

the acquisition module is used for acquiring vehicle state information;

a determination module for determining a feedforward control amount for canceling a steady-state lateral error, based on the vehicle state information, using the following equation (1):

wherein, F_{yf_feedforword}Representing a feedforward control quantity, K₃Representing a predetermined scale factor, e_{s_yaw}Representing steady state yaw angle error, c_rDenotes the curvature of the path,/_rRepresenting the distance of the centre of mass from the rear axle, m representing the mass of the vehicle, v_xRepresenting longitudinal vehicle speed, A_xRepresenting longitudinal acceleration, x_copIndicating a vehicle impact center position, L indicating a vehicle wheelbase, δ indicating a front wheel steering angle;

wherein the content of the first and second substances,

wherein l_fIs the distance of the center of mass from the front axis, C_rFor the tire sidewall deflection stiffness, k, of the rear wheel_rCoefficients characterizing the nonlinear characteristics of the tire;

and the control module is used for realizing the transverse control of the vehicle according to the obtained feedforward control quantity.

10. The apparatus of claim 9, wherein the equation (1) is obtained based on the following settings:

is established withFront wheel cornering forces F as vehicle state vectors_yfEquation of state input for system control:

wherein:

in the formula (I), the compound is shown in the specification,representing the derivative of the vehicle state vector, C_rFor the tire sidewall deflection stiffness of the rear wheel, c_rIs the curvature of the path, k_rTo characterize the non-linear behavior of a tire, e_copFor lateral error based on center of vehicle impact, F_yfIs the cornering force of the front wheel, I_zThe moment of inertia of the vehicle about the z-axis, s is the reference path,for course deviation, L ═ L_r+x_cop，v_xFor longitudinal vehicle speed, r yaw rate, l_fIs the distance of the center of mass from the front axis,/_rIs the distance of the center of mass from the rear axis, x_copA vehicle impact center position;

order to

A state space model for the closed-loop lateral control system under state feedback is obtained:

where K is the system control gain matrix, c_rIs the path curvature.

Technical Field

The invention relates to the technical field of transverse control of an automatic driving vehicle, in particular to a path tracking feedforward control method and a path tracking feedforward control device.

Background

The problem of vehicle lateral control is always concerned by scholars at home and abroad as a core technology of unmanned vehicle motion control research. It reflects the ability to smoothly and accurately follow a predetermined desired trajectory with an unmanned vehicle. The transverse motion of the automobile is a strong nonlinear system, and has strong coupling effect with longitudinal motion, tires and loads, and the existing two-degree-of-freedom whole automobile dynamics model and small-angle lateral deviation tire model can solve the transverse control problem under some simple working conditions, but cannot cope with more complex road surface environment.

Disclosure of Invention

It is an object of the present invention to provide a path-tracking feedforward control method and apparatus that overcomes or at least mitigates at least one of the above-mentioned disadvantages of the prior art.

To achieve the above object, an embodiment of the present invention provides a path tracking feedforward control method, including:

step 1, obtaining vehicle state information;

and 2, determining a feedforward control quantity for counteracting the steady-state lateral error by using the following formula (1) according to the vehicle state information:

wherein, F_{yf_feedforword}Representing a feedforward control quantity, K₃Representing a predetermined ratio systemNumber e_{s_yaw}Representing steady state yaw angle error, c_rDenotes the curvature of the path,/_rRepresenting the distance of the centre of mass from the rear axle, m representing the mass of the vehicle, v_xRepresenting longitudinal vehicle speed, A_xRepresenting longitudinal acceleration, x_copIndicating a vehicle impact center position, L indicating a vehicle wheelbase, δ indicating a front wheel steering angle;

wherein the content of the first and second substances,

wherein l_fIs the distance of the center of mass from the front axis, C_rFor the tire sidewall deflection stiffness, k, of the rear wheel_rCoefficients characterizing the nonlinear characteristics of the tire;

and 3, realizing the transverse control of the vehicle according to the obtained feedforward control quantity.

Preferably, said K₃Column 3 elements of the gain matrix are controlled for the system.

Preferably, the system control gain matrix is a matrix obtained by an LQR (linear quadratic regulator) system.

Preferably, step 3 comprises: and adding the feedforward control quantity and the feedback control quantity to obtain a final control quantity, and using the final control quantity to realize the transverse control of the vehicle.

Preferably, the feedback control amount is a product of a vehicle state vector and a preset proportionality coefficient.

Preferably, the formula (1) is obtained based on the following settings:

is established withFront wheel cornering forces F as vehicle state vectors_yfEquation of state input for system control:

wherein:

in the formula (I), the compound is shown in the specification,representing the derivative of the vehicle state vector, C_rFor the tire sidewall deflection stiffness of the rear wheel, c_rIs the curvature of the path, k_rTo characterize the non-linear behavior of a tire, e_copFor lateral error based on center of vehicle impact, F_yfIs the cornering force of the front wheel, I_zThe moment of inertia of the vehicle about the z-axis, s is the reference path,for course deviation, L ═ L_r+x_cop，v_xFor longitudinal vehicle speed, r yaw rate, l_fIs the distance of the center of mass from the front axis,/_rIs the distance of the center of mass from the rear axis, x_copA vehicle impact center position;

order to

A state space model for the closed-loop lateral control system under state feedback is obtained:

where K is the system control gain matrix, c_rIs the path curvature.

Preferably, step 3 comprises:

the feedback control amount is obtained using the following equation:

F_{yf_feedback}＝-Kx

the feedback control quantity F_{yf_feedback}With said feedforward control quantity F_{yf_feedforword}Summing to obtain the front wheel side deflection force:

F_yf＝F_{yf_feedback}+F_{yf_feedforword}

lateral control of the vehicle is achieved using the front wheel side biasing force.

Preferably, the state space model of the closed loop system is represented as:

obtained by Laplace transform and making the initial state of the system be zero

X(s)＝(sI-(A-BK))^-1(BL(F_{yf_feedforword})+DL(c_r))

Wherein, L (F)_{yf_feedforword}) And L (c)_r) Are respectively F_{yf_feedforword}And c_rX(s) is a function on the complex variable s, I is an identity matrix;

the feedforward control amount is made constant, and Laplace transformation of the feedforward control amount is performedObtaining a steady-state lateral error:

through sign operation, the steady-state error expression is obtained as follows:

wherein, K_iTo control the ith column element of the gain matrix for the system, A_xIs the longitudinal acceleration;

and obtaining the formula (2) and the formula (1) based on the steady-state error expression.

The embodiment of the invention also provides a path tracking feedforward control device, which comprises:

the acquisition module is used for acquiring vehicle state information;

a determination module for determining a feedforward control amount for canceling a steady-state lateral error, based on the vehicle state information, using the following equation (1):

wherein, F_{yf_feedforword}Representing a feedforward control quantity, K₃Representing a predetermined scale factor, e_{s_yaw}Representing steady state yaw angle error, c_rDenotes the curvature of the path,/_rRepresenting the distance of the centre of mass from the rear axle, m representing the mass of the vehicle, v_xRepresenting longitudinal vehicle speed, A_xRepresenting longitudinal acceleration, x_copIndicating a vehicle impact center position, L indicating a vehicle wheelbase, δ indicating a front wheel steering angle;

wherein the content of the first and second substances,

wherein l_fIs the distance of the center of mass from the front axis, C_rFor the tire sidewall deflection stiffness, k, of the rear wheel_rCoefficients characterizing the nonlinear characteristics of the tire;

and the control module is used for realizing the transverse control of the vehicle according to the obtained feedforward control quantity.

Due to the adoption of the technical scheme, the embodiment of the invention has the following advantages:

a steady-state error expression obtained by using a steady-state error model of the path tracking control system based on the strike center modeling is utilized to obtain a feedforward control quantity capable of offsetting a steady-state transverse error, so that the steady-state error of the path tracking control system under the curve working condition can be eliminated, and the path tracking precision is improved.

Drawings

Fig. 1 is a schematic flow chart of a path tracking feedforward control method according to an embodiment of the present invention.

Fig. 2 is a flowchart showing a method of determining the calculation formula of the feedforward control amount applied to the embodiment of the present invention.

Fig. 3 is a schematic structural diagram of a path tracking feedforward control device according to an embodiment of the present invention.

Detailed Description

In the drawings, the same or similar reference numerals are used to denote the same or similar elements or elements having the same or similar functions. Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

In the description of the present invention, the terms "central", "longitudinal", "lateral", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and therefore, should not be construed as limiting the scope of the present invention.

In the present invention, the technical features of the embodiments and implementations may be combined with each other without conflict, and the present invention is not limited to the embodiments or implementations in which the technical features are located.

The present invention will be further described with reference to the accompanying drawings and specific embodiments, it should be noted that the technical solutions and design principles of the present invention are described in detail in the following only by way of an optimized technical solution, but the scope of the present invention is not limited thereto.

The embodiment of the invention provides a path tracking feedforward control method which is applied to an automatic driving vehicle. The automatic driving vehicle comprises a vehicle steering system, a navigation system (such as a combined inertial navigation system), an industrial personal computer and a vehicle bottom line control system. Of course, the autonomous vehicle may also include other configurations that are not described in detail herein.

The embodiment of the invention provides a path tracking feedforward control method. Fig. 1 shows a flow chart of the path tracking feedforward control method, which includes:

and step 110, obtaining vehicle state information including vehicle yaw angle, mass, longitudinal vehicle speed, longitudinal acceleration and wheel rotation angle.

In one example, vehicle yaw angle, longitudinal vehicle speed, longitudinal acceleration are obtained by a combination inertial navigation system, vehicle mass is obtained by a mass sensor, and wheel rotation angle is obtained by vehicle CAN bus signal feedback.

And step 120, calculating a feedforward control quantity for counteracting the steady-state lateral error according to the acquired vehicle state information by using the following formula:

wherein, F_{yf_feedforword}Representing a feedforward control quantity, K₃Representing a predetermined scaling factor, e.g. column 3 element of the system control gain matrix_{s_yaw}Representing steady state yaw angle error, c_rDenotes the curvature of the path,/_rRepresenting the distance of the centre of mass from the rear axle, m representing the mass of the vehicle, v_xRepresenting longitudinal vehicle speed, A_xRepresenting longitudinal acceleration, x_copIndicating the vehicle impact center position, L the vehicle wheelbase, and δ the front wheel angle.

Wherein the system control gain matrix, the steady-state yaw angle error, and the vehicle impact center position are terms in the industry, and the system control gain matrix is a matrix obtained by an LQR (linear quadratic regulator) system; the steady state yaw angle error is a yaw angle error with a numerical value kept unchanged; the vehicle collision center position is a position where the lateral acceleration of the vehicle body and the yaw acceleration caused by the vehicle rear wheel side-shifting force can cancel each other out.

Wherein the content of the first and second substances,

wherein l_fIs of qualityDistance of the center from the front axis, C_rFor the tire sidewall deflection stiffness, k, of the rear wheel_rAre coefficients characterizing the non-linear behavior of the tire.

And step 130, realizing the transverse control of the vehicle according to the calculated feedforward control amount.

Preferably, the feedforward control quantity and the feedback control quantity are combined to obtain a final control quantity of the system so as to eliminate the steady-state lateral error of the system. The feedback control quantity is a product of the vehicle state vector and a preset proportionality coefficient, for example, the system control gain matrix. Wherein combining the feedforward control amount with the feedback control amount comprises: the feedforward control amount and the feedback control amount are added.

Fig. 2 shows a method of determining the above calculation formula of the feedforward control amount applied to the embodiment of the present invention.

As shown in fig. 2, the method includes:

and step 210, establishing a steady-state error model of the path tracking control system for modeling based on the impact center under the condition of feedforward and feedback.

And step 220, designing a feedforward control quantity capable of offsetting the steady-state transverse error based on the steady-state error expression.

The above two steps are explained in detail below.

In step 210, establish toFront wheel cornering forces F as vehicle state vectors_yfThe state equation input for system control, namely the steady state error model:

wherein:

in the formula (I), the compound is shown in the specification,representing the derivative of the vehicle state vector, C_rFor the tire sidewall deflection stiffness of the rear wheel, c_rIs the curvature of the path, k_rTo characterize the non-linear behavior of a tire, e_copFor lateral error based on center of vehicle impact, F_yfIs the cornering force of the front wheel, I_zThe moment of inertia of the vehicle about the z-axis, s is the reference path,for course deviation, L ═ L_r+x_cop，v_xFor longitudinal vehicle speed, r yaw rate, l_fIs the distance of the center of mass from the front axis,/_rIs the distance of the center of mass from the rear axis, x_copIs the vehicle impact center position.

Order to

The state space model for the closed loop lateral control system under state feedback can be expressed as:

where K is the control gain matrix of the LQR system, c_rIs the path curvature.

Assuming that the front wheel side biasing force can be controlled by the state feedback control quantity F_{yf_feedback}Adding a feedforward control quantity F_{yf_feedforword}Obtaining:

F_yf＝F_{yf_feedback}+F_{yf_feedforword}

F_{yf_feedback}＝-Kx

the state space model of the closed loop system can be expressed as:

using Laplace (Laplace) transform, assuming that the system initial state is zero, we can obtain:

X(s)＝(sI-(A-BK))^-1(BL(F_{yf_feedforword})+DL(c_r))

wherein L (F)_{yf_feedforword}) And L (c)_r) Are respectively F_{yf_feedforword}And c_rX(s) is a function on the complex variable s, I is the identity matrix.

Assuming that the feedforward control quantity is constant, its Laplace transformUsing the theorem of final values, the steady state lateral error can be expressed as:

the steady state error expression obtained by the symbolic operation is:

wherein, K_iFor the ith column element in the control gain matrix of the LQR system, A_xIs the longitudinal acceleration.

In step 220, the steady state yaw angle error may be expressed as:

the feedforward control amount that can cancel the steady-state lateral error is:

from the formula, one can obtain:

wherein the course angle error

The embodiment of the invention provides a path tracking feedforward control device, which is used for realizing the steps in the method embodiment. Fig. 3 is a schematic structural diagram of the path-tracking feedforward control device, as shown in fig. 3, including:

an obtaining module 10, configured to obtain vehicle state information;

a determination module 20, configured to determine a feedforward control amount for canceling a steady-state lateral error according to the vehicle state information by using the following equation (1):

wherein, F_{yf_feedforword}Representing a feedforward control quantity, K₃Representing a predetermined scale factor, e_{s_yaw}Representing steady state yaw angle error, c_rDenotes the curvature of the path,/_rRepresenting the distance of the centre of mass from the rear axle, m representing the mass of the vehicle, v_xRepresenting longitudinal vehicle speed, A_xRepresenting longitudinal acceleration, x_copIndicating a vehicle impact center position, L indicating a vehicle wheelbase, δ indicating a front wheel steering angle;

wherein the content of the first and second substances,

wherein l_fIs the distance of the center of mass from the front axis, C_rFor the tire sidewall deflection stiffness, k, of the rear wheel_rCoefficients characterizing the nonlinear characteristics of the tire;

and the control module 30 is used for realizing the transverse control of the vehicle according to the obtained feedforward control quantity.

Preferably, said K₃Column 3 elements of the gain matrix are controlled for the system.

Preferably, the system control gain matrix is a matrix obtained by an LQR (linear quadratic regulator) system.

Preferably, step 3 comprises: and adding the feedforward control quantity and the feedback control quantity to obtain a final control quantity, and using the final control quantity to realize the transverse control of the vehicle.

Preferably, the feedback control amount is a product of a vehicle state vector and a preset proportionality coefficient.

Preferably, the formula (1) is obtained based on the following settings:

is established withFront wheel cornering forces F as vehicle state vectors_yfEquation of state input for system control:

wherein:

in the formula (I), the compound is shown in the specification,representing the derivative of the vehicle state vector, C_rFor the tire sidewall deflection stiffness of the rear wheel, c_rIs the curvature of the path, k_rTo characterize the non-linear behavior of a tire, e_copFor lateral error based on center of vehicle impact, F_yfIs the cornering force of the front wheel, I_zThe moment of inertia of the vehicle about the z-axis, s is the reference path,for course deviation, L ═ L_r+x_cop，v_xFor longitudinal vehicle speed, r yaw rate, l_fIs the distance of the center of mass from the front axis,/_rIs the distance of the center of mass from the rear axis, x_copA vehicle impact center position;

order to

A state space model for the closed-loop lateral control system under state feedback is obtained:

where K is the system control gain matrix, c_rIs the path curvature.

Preferably, step 3 comprises:

the feedback control amount is obtained using the following equation:

F_{yf_feedback}＝-Kx

the feedback control quantity F_{yf_feedback}With said feedforward control quantity F_{yf_feedforword}Summing to obtain the front wheel side deflection force:

F_yf＝F_{yf_feedback}+F_{yf_feedforword}

lateral control of the vehicle is achieved using the front wheel side biasing force.

Preferably, the state space model of the closed loop system is represented as:

obtained by Laplace transform and making the initial state of the system be zero

X(s)＝(sI-(A-BK))^-1(BL(F_{yf_feedforword})+DL(c_r))

Wherein, L (F)_{yf_feedforword}) And L (c)_r) Are respectively F_{yf_feedforword}And c_rX(s) is a function on the complex variable s, I is an identity matrix;

the feedforward control amount is made constant, and Laplace transformation of the feedforward control amount is performedObtaining a steady-state lateral error:

through sign operation, the steady-state error expression is obtained as follows:

wherein, K_iTo control the ith column element of the gain matrix for the system, A_xIs the longitudinal acceleration;

and obtaining the formula (2) and the formula (1) based on the steady-state error expression.

Finally, it should be pointed out that: the above examples are only for illustrating the technical solutions of the present invention, and are not limited thereto. Those of ordinary skill in the art will understand that: modifications can be made to the technical solutions described in the foregoing embodiments, or some technical features may be equivalently replaced; such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.