Vehicle lateral control method, system and automobile

Abstract

The application provides a vehicle lateral control method, system and automobile, comprising the following steps: judging the driving state of the current vehicle according to the current vehicle speed, and selecting a corresponding automatic driving vehicle lateral controller; inputting the current vehicle speed, the vehicle yaw rate, the vehicle mass center side slip angle, the lateral deviation between the vehicle and the target path, the heading angle deviation, and the target path curvature into the corresponding vehicle lateral controller to obtain the total expected steering wheel angle of the vehicle; outputting the final steering wheel angle obtained after limiting the amplitude of the steering wheel angle and the change rate of the steering wheel angle to the steering controller, and then performing steering control according to the final steering wheel angle. The application selects appropriate vehicle lateral controllers for different working conditions, considers the calculation complexity and the control accuracy, and can realize the applicability in all working conditions. Fewer control parameters need to be adjusted, and the working efficiency and the universality can be improved.

Description

A vehicle lateral control method, system and automobile Technical Field

[0001] This invention relates to the field of lateral control technology for autonomous driving, and in particular to a vehicle lateral control method, system, and automobile. Background Technology

[0002] The application scenarios of autonomous driving technology have gradually expanded from specific driving assistance conditions to all conditions, including ramps, urban roads, and highways. The requirements of these scenarios for vehicle motion control algorithms are becoming increasingly higher. In the complex scenarios of autonomous driving on roads with different speeds and curvatures, lateral control is particularly important for vehicle safety.

[0003] Current control methods mainly include PID, fuzzy control, MPC, active disturbance rejection control, sliding mode control, and end-to-end control, but each has its own limitations, primarily the need to adjust numerous parameters, the large workload of parameter tuning that relies on experience, and the high computational cost. Currently, vehicle system modeling includes geometric models, dynamic models, and kinematic-dynamic combined models. Choosing an appropriate vehicle system model based on the control method is crucial to achieving a balance between computational complexity and accuracy.

[0004] The most commonly used pure tracking algorithm controls the vehicle's steering radius, guiding the rear axle center along an arc to the target path point at a pre-aimed distance. Then, the required front wheel steering angle is designed based on the Ackerman steering model. This method is simple and practical, and exhibits good robustness to road curvature disturbances. However, its tracking performance heavily depends on the selection of the pre-aimed distance, and obtaining the optimal value is difficult. Furthermore, the pure tracking algorithm is based on a simple geometric model and does not consider vehicle dynamics and steering actuator dynamics. Rapid changes in steering curvature at high speeds can easily cause vehicle sideslip, and a significant discrepancy between the system model and actual vehicle characteristics leads to deteriorated tracking performance. Summary of the Invention

[0005] The purpose of this invention is to propose a vehicle lateral control method, system, and automobile, which solves the technical problem of how to reduce the amount of computation while ensuring the accuracy of lateral control under all operating conditions.

[0006] On the one hand, a vehicle lateral control method is provided, including:

[0007] Real-time acquisition of vehicle's current speed, yaw rate, sideslip angle, lateral deviation between vehicle and target path, heading angle deviation, and target path curvature;

[0008] The current vehicle speed is used to determine the current driving status of the vehicle, and the corresponding driving lateral controller is selected according to the current driving status of the vehicle.

[0009] The vehicle's current speed, yaw rate, sideslip angle, lateral deviation between the vehicle and the target path, heading angle deviation, and target path curvature are input into the corresponding autonomous driving lateral controller for calculation to obtain the vehicle's total expected steering wheel angle.

[0010] The steering controller performs steering control based on the desired steering wheel angle;

[0011] The lateral control system includes a low-speed lateral control system and a high-speed lateral control system.

[0012] Preferably, the step of determining the current vehicle's driving status based on the current vehicle speed and selecting the corresponding lateral control controller based on the current vehicle's driving status specifically includes:

[0013] Compare the current vehicle speed with the preset smooth starting vehicle speed and smooth speed width;

[0014] If the current vehicle speed is less than the smoothing starting speed, the current vehicle driving state is determined to be low speed, and a preset low-speed autonomous driving lateral controller is selected.

[0015] If the current vehicle speed is greater than the sum of the smoothed starting speed and the smoothed speed width, then the current driving state of the vehicle is determined to be high speed, and a preset high-speed autonomous driving lateral controller is selected.

[0016] If the current vehicle speed is greater than the smoothing starting speed and less than the sum of the smoothing starting speed and the smoothing speed width, then a smooth transition is performed between the preset high-speed driving lateral controller and the low-speed driving lateral controller.

[0017] Preferably, obtaining the total desired steering wheel angle of the vehicle specifically includes:

[0018] The desired steering wheel angle of the low-speed controller is calculated using the low-speed driving lateral controller.

[0019] The desired steering wheel angle of the high-speed controller is calculated using the high-speed driving lateral controller;

[0020] The total expected steering wheel angle is calculated based on the expected steering wheel angle of the low-speed lateral controller, the expected steering wheel angle of the high-speed lateral controller, and the smooth transition coefficients corresponding to the low-speed and high-speed lateral controllers.

[0021] Preferably, the step of calculating the desired steering wheel angle of the low-speed vehicle lateral controller via the low-speed vehicle lateral controller specifically includes:

[0022] Based on the current vehicle speed, vehicle center of gravity sideslip angle, relative lateral position deviation between the vehicle and the target path, heading angle deviation, and target path curvature, the desired steering wheel angle feedforward control quantity under low-speed conditions is calculated by the low-speed driving lateral controller.

[0023] The desired steering wheel angle feedforward control quantity under the low-speed operating condition is output as the desired steering wheel angle of the low-speed driving lateral controller.

[0024] Preferably, the desired steering wheel angle feedforward control value under low-speed conditions is calculated according to the following formula:

[0025]

[0026] Where, δ w,ff,ls Let represent the desired steering wheel angle feedforward control value under low-speed conditions, r represent the relative lateral position deviation between the vehicle and the target path, θ represent the relative heading angle deviation between the vehicle speed and the target path, κ represent the curvature of the target path, l represent the wheelbase of the vehicle, and ii represent the other values. wf This represents the steering ratio between the front wheel rotation angle and the steering wheel rotation angle, where k0 is a constant coefficient of 0 and k1 is a constant coefficient of 1.

[0027] Preferably, the step of calculating the desired steering wheel angle of the high-speed vehicle lateral controller via the high-speed vehicle lateral controller specifically includes:

[0028] Based on the current vehicle speed, vehicle center of gravity sideslip angle, relative lateral position deviation between the vehicle and the target path, heading angle deviation, and target path curvature, the expected steering wheel angle feedforward control quantity under high-speed conditions is calculated by the high-speed driving lateral controller.

[0029] Calculate the steering wheel angle feedback control quantity under high-speed conditions based on the vehicle's yaw rate;

[0030] The sum of the desired steering wheel angle feedforward control quantity and the steering wheel angle feedback control quantity under the high-speed operating condition is output as the desired steering wheel angle of the high-speed controller.

[0031] Preferably, the desired steering wheel angle feedforward control value under high-speed conditions is calculated according to the following formula:

[0032]

[0033]

[0034]

[0035] Where, δ w,ff,hsω represents the desired steering wheel angle feedforward control value under high-speed conditions. d This represents the virtual control quantity, namely the desired yaw rate of the high-speed controller, g. ω (v) represents the steady-state gain, ii wf The steering ratio represents the front wheel turning angle versus the steering wheel turning angle; r represents the relative lateral position deviation between the vehicle and the target path; θ represents the relative heading angle deviation between the vehicle speed and the target path; κ represents the curvature of the target path; η represents linear state feedback control; m represents the vehicle mass; v represents the vehicle speed; and C... f C represents the lateral stiffness of a single front wheel. r The l represents the lateral stiffness of a single rear wheel. f The distance l represents the distance from the center of mass to the front axle. r This indicates the distance from the center of mass to the rear axle.

[0036] Preferably, the steering wheel angle feedback control quantity under high-speed conditions is calculated according to the following formula:

[0037] δ w,fb =k ω (ω d -ω)

[0038] Where, δ w,fb k represents the steering wheel angle feedback control quantity under high-speed conditions. ω ω represents the feedback coefficient. d ω represents the virtual control quantity, i.e., the expected yaw rate of the high-speed controller, where ω represents the current yaw rate of the vehicle.

[0039] Preferably, the smooth transition coefficients corresponding to the low-speed controller and the high-speed controller are calculated using the following formula:

[0040]

[0041] Where f represents the smooth transition coefficient, v represents the current vehicle speed, and v fading,start Indicates a smooth initial vehicle speed, v fading,width This indicates the width of the smooth vehicle speed.

[0042] Preferably, the total desired steering wheel angle is calculated using the following formula:

[0043] δ w =fδ w,hs +(1-f)δ w,ls

[0044] Where, δ w δ represents the total expected steering wheel angle. w,hs δ represents the desired steering wheel angle of the high-speed controller. w,lsdenoted by , where represents the desired steering wheel angle of the low-speed controller, and f represents the smooth transition coefficient.

[0045] On the other hand, a vehicle lateral control system is also provided to implement the aforementioned vehicle lateral control method, comprising:

[0046] The vehicle data acquisition module is used to acquire in real time the vehicle's current speed, yaw rate, sideslip angle, lateral deviation between the vehicle and the target path, heading angle deviation, and target path curvature.

[0047] The lateral controller selection module is used to determine the current driving status of the vehicle based on the current vehicle speed, and select the corresponding driving lateral controller based on the current driving status of the vehicle.

[0048] The steering wheel angle calculation module takes the vehicle's current speed, yaw rate, sideslip angle, lateral deviation between the vehicle and the target path, heading angle deviation, and target path curvature as inputs to the corresponding autonomous driving lateral controller for calculation, and obtains the total expected steering wheel angle of the vehicle; the steering controller performs steering control based on the expected steering wheel angle.

[0049] The lateral control system includes a low-speed lateral control system and a high-speed lateral control system.

[0050] On the other hand, a vehicle is also provided in which the vehicle steering is controlled by the aforementioned vehicle lateral control system.

[0051] In summary, implementing the embodiments of the present invention has the following beneficial effects:

[0052] The vehicle lateral control method, system, and vehicle provided by this invention select corresponding high-speed and low-speed lateral controllers based on vehicle speed. The inputs to the entire controller are the lateral deviation between the vehicle and the target path at the current moment, the heading angle deviation, the curvature of the target path, the vehicle's current speed, yaw rate, and the vehicle's center of gravity sideslip angle. The corresponding controllers calculate the desired steering wheel angles at high and low speeds. The calculation results of the high-speed and low-speed lateral controllers are selected or smoothed, and after amplitude limiting, the final steering wheel angle control output is given to the EPS (Electrical Power Steering) system. The vehicle motion response and cyclic control achieve tracking of the target path. Attached Figure Description

[0053] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0054] Figure 1 is a schematic diagram of the main flow of a vehicle lateral control method according to an embodiment of the present invention.

[0055] Figure 2 is a schematic diagram of a vehicle lateral control system according to an embodiment of the present invention.

[0056] Figure 3 is a schematic diagram of the Frenet coordinate system in an embodiment of the present invention. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0058] Figure 1 shows a schematic diagram of an embodiment of an autonomous driving lateral control method provided by the present invention. In this embodiment, the method includes the following steps:

[0059] The system acquires in real-time the vehicle's current speed, yaw rate, sideslip angle, lateral deviation between the vehicle and the target path, heading angle deviation, and target path curvature. In other words, this invention uses a feedback linearization method to solve nonlinear problems, introducing the desired yaw rate ω. d As a virtual control variable, the entire control process is divided into two layers for hierarchical control: The first layer employs a feedback linearization method, using vehicle kinematics to calculate the desired yaw rate from the vehicle's lateral deviation, heading angle deviation, vehicle speed, and path curvature relative to the target path. The second layer uses a combination of feedforward control and feedback control, or feedforward control alone, to calculate the desired steering wheel angle based on the vehicle dynamics or kinematic model, using the desired yaw rate, vehicle speed, and steering model. The entire calculation process requires fewer control parameters to be adjusted and has a clear theoretical basis for parameter tuning, rather than relying heavily on experience or blindly experimenting, thus improving work efficiency and the universality of the control algorithm.

[0060] Furthermore, the current vehicle's driving state is determined based on the current vehicle speed, and the corresponding autonomous driving lateral control is selected accordingly. That is, in the Frenet coordinate system shown in Figure 3, different linear state feedback control is required for different vehicle speed conditions. Specifically, for high-speed autonomous driving lateral control, a feedback linearization method is used to simplify the stability problem of the nonlinear system into the stability problem of a controllable linear system. Through a preset stable linear state feedback control law, the eigenvalues ​​of the closed-loop system are made to be in the left half-open plane (system stability), thereby obtaining the desired yaw rate ω. d A linear state feedback control law is used for the virtual control quantity. For lateral control of low-speed autonomous driving, assuming small lateral and heading angle deviations at low speeds, a singularity is avoided when the vehicle speed approaches zero. The system is transformed into a new nonlinear system by taking the derivative of the distance, and then processed using a linearized state feedback control law for low-speed conditions. The feedback linearization method is employed to appropriately linearize the system state equations, simplifying the solution and reducing computational complexity.

[0061] In a specific embodiment, the current vehicle speed is compared with a preset smoothing starting speed and a smoothing speed width. If the current vehicle speed is less than the smoothing starting speed, the current vehicle's driving state is determined to be low speed, and a preset low-speed autonomous driving lateral controller is selected. If the current vehicle speed is greater than the sum of the smoothing starting speed and the smoothing speed width, the current vehicle's driving state is determined to be high speed, and a preset high-speed autonomous driving lateral controller is selected. If the current vehicle speed is greater than the smoothing starting speed but less than the sum of the smoothing starting speed and the smoothing speed width, a smooth transition occurs between the preset high-speed autonomous driving lateral controller and the low-speed autonomous driving lateral controller. Here, the smoothing starting speed refers to the lower limit node for entering the smoothing process (a transition between low and high speed). If it is less than this node, it indicates that the vehicle is at low speed. The smoothing speed width refers to the range of the smoothing process. In summary, the node obtained by summing the smoothing starting speed and the smoothing speed width is the upper limit node of the smoothing process. If it is greater than this node, it indicates that the vehicle is at high speed. It should be noted that the smooth starting speed and smooth speed width are set according to the specific vehicle model.

[0062] In this embodiment, the high-speed autonomous driving lateral controller is based on the two-degree-of-freedom vehicle dynamics state equations to calculate the desired steering wheel angle that brings the system to a steady state. Achieving this steady state requires ω... d The virtual control quantity is controlled by a linear state feedback control law.

[0063] Specifically, under high-speed operating conditions, the desired yaw rate ω is determined. d The process of a linear state feedback control law for virtual control variables is as follows:

[0064] The nonlinear kinematics formula for a vehicle under high-speed conditions in the Frenet coordinate system is as follows:

[0065] s(0)=s0

[0066] r(0)=f0

[0067] θ(0)=θ0

[0068] Where θ=β+ψ-ψ p ; s represents the distance the vehicle travels along the target path, and s0 represents the initial value of the distance the vehicle travels along the target path. Let r be the tangential velocity of the vehicle at point P, r be the relative lateral position deviation between the vehicle and the target path, and r0 be the initial value of the relative lateral position deviation between the vehicle and the target path. Let θ be the lateral velocity of the vehicle at point P, θ be the relative heading angle deviation between the vehicle speed and the target path (i.e., the angle between the vehicle speed and the Ps axis), and θ0 be the initial value of the relative heading angle deviation between the vehicle speed and the target path. Let v be the relative angular velocity of the vehicle's rotation relative to the target path coordinate system, v be the current vehicle speed, β be the current sideslip angle of the vehicle's center of gravity, and ψ be the angle between the vehicle's orientation and the Ox axis. p The orientation of the current position path is the angle between the Ps axis and the Ox axis, Δψ = ψ - ψ p Let ω be the heading angle deviation between vehicles and the target path, ω be the current vehicle's yaw rate, and κ be the curvature of the target path at point P.

[0069] Let the state vector ξ be as follows:

[0070]

[0071] Where z1 is state variable 1; z2 is state variable 2.

[0072] The state equation of a nonlinear system is as follows:

[0073]

[0074] Where r is the relative lateral position deviation between the vehicle and the target path, θ is the relative heading angle deviation between the vehicle speed and the target path, i.e., the angle between the vehicle speed and the Ps axis, v is the current vehicle speed, ω is the current yaw rate of the vehicle, and κ is the curvature of the target path at point P.

[0075] From the above formulas, we can see that when performing feedback linearization, let

[0076] Where r is the relative lateral position deviation between the vehicle and the target path, θ is the relative heading angle deviation between the vehicle speed and the target path, i.e., the angle between the vehicle speed and the Ps axis, v is the current vehicle speed, ω is the current yaw rate of the vehicle, and κ is the curvature of the target path at point P. The state equation of the second-order linear system is obtained as follows:

[0077] Therefore, a linear state feedback control can be designed, as shown in the equation: η=-k1z2-k0z1

[0078] Where k0 is a constant coefficient of 0; k1 is a constant coefficient of 1. The process of finding k0 and k1 is as follows: Given the characteristic equation of a second-order system: Where s is the complex variable used in the Laplace transform, ω0 is the natural frequency, and ζ is the damping coefficient.

[0079] Substituting the linear state feedback control equation into the second equation of the second-order linear system state equation, we get: By comparing the characteristic equation of the second-order system, the following equation is derived: k1=2ζω0.

[0080] The second-order system response index is used as an important parameter in this step: y p Maximum overshoot; t s Adjust the time;

[0081] When the system is underdamped, the following equation applies:

[0082]

[0083] For a 2% error standard, the settling time is approximately equal to the system time constant. 4 times, resulting in: Where, T is the system time constant. Then it can be deduced that:

[0084] We can obtain the desired yaw rate ω under high-speed conditions. d The linear state feedback control law for the virtual control quantity is as follows:

[0085]

[0086] That is, we can get ω d The expression for the linear state feedback control law for the virtual control quantity.

[0087] In this embodiment, the lateral controller for low-speed automated driving has small lateral and heading angle deviations under low-speed conditions. Specifically, under low-speed conditions, ω... dThe process of a linear state feedback control law for virtual control variables is as follows:

[0088] Simplified nonlinear state equations can be obtained from kinematic analysis in the Frenet coordinate system:

[0089] s(0)=s0

[0090] r(0)=r0

[0091] θ(0)=θ0

[0092] Where θ=β+ψ-ψ p ; s represents the distance the vehicle travels along the target path, and s0 represents the initial value of the distance the vehicle travels along the target path. Let r be the tangential velocity of the vehicle at point P, r be the relative lateral position deviation between the vehicle and the target path, and r0 be the initial value of the relative lateral position deviation between the vehicle and the target path. Let θ be the lateral velocity of the vehicle at point P, θ be the relative heading angle deviation between the vehicle speed and the target path (i.e., the angle between the vehicle speed and the Ps axis), and θ0 be the initial value of the relative heading angle deviation between the vehicle speed and the target path. Let v be the relative angular velocity of the vehicle's rotation relative to the target path coordinate system, v be the current vehicle speed, β be the current sideslip angle of the vehicle's center of gravity, and ψ be the angle between the vehicle's orientation and the Ox axis. p The orientation of the current position path is the angle between the Ps axis and the Ox axis, Δψ = ψ - ψ p Let ω be the heading angle deviation between vehicles and the target path, ω be the current vehicle's yaw rate, and κ be the curvature of the target path at point P.

[0093] To avoid a singularity when the vehicle speed approaches 0, the derivative with respect to the distance is expressed as:

[0094] After transformation, it becomes the following formula:

[0095] s(0)=s0

[0096] r′=θ r(0=r0

[0097] θ′=ω′-κ θ(0)=θ0

[0098] Where s′ is the derivative of s with respect to distance, r′ is the derivative of r with respect to distance, θ′ is the derivative of θ with respect to distance, and ω′ is the derivative of ω with respect to distance.

[0099] Let the state vector ξ be as shown in the equation: Where z1 is state variable 1; z2 is state variable 2.

[0100] Establish the nonlinear state equations under low-speed operating conditions:

[0101]

[0102] A linear state feedback control law for low-speed operation is designed using the feedback linearization method: Let η = ω′ - κ, feedback linearization is performed, and the process of finding η is similar to that of the lateral controller for high-speed autonomous driving, with the formula: η = -k1z2 - k0z1, where, k1=2ζω0.

[0103] To avoid a singularity when the vehicle speed approaches 0 under low-speed conditions, the second-order system response index y used in the low-speed autonomous driving lateral controller is the maximum overshoot y. p Adjust distance d s This is an important parameter for this step.

[0104] The following formula can be derived:

[0105]

[0106]

[0107] The desired yaw rate ω can be obtained using a low-speed controller. d A linear state feedback control law for virtual control variables, such as: ω′ d =-k0r-k1θ+κ.

[0108] Furthermore, the vehicle's current speed, yaw rate, sideslip angle, lateral deviation between the vehicle and the target path, heading angle deviation, and target path curvature are input to the corresponding autonomous driving lateral controller for calculation, resulting in the vehicle's total desired steering wheel angle. In other words, by using high- and low-speed controllers, appropriate vehicle models can be selected from different layers within the appropriate controller, balancing computational complexity and control accuracy, rather than using a single system model, thus achieving applicability across all operating conditions.

[0109] In this embodiment, the specific calculation process includes calculating the desired steering wheel angle of the low-speed controller through the low-speed autonomous driving lateral controller; specifically, based on the current vehicle speed, vehicle center of gravity sideslip angle, relative lateral position deviation between the vehicle and the target path, heading angle deviation, and target path curvature, the desired steering wheel angle feedforward control quantity under low-speed conditions is calculated through the low-speed autonomous driving lateral controller; and the desired steering wheel angle feedforward control quantity under low-speed conditions is output as the desired steering wheel angle of the low-speed controller.

[0110] The specific value of ω is determined according to the following formula. d Linear state feedback control law for virtual control variables:

[0111] ω′ d =-k0r-k1θ+κ

[0112] The above determines the specific value of ω. d After applying the linear state feedback control law for the virtual control quantity, the specific process for calculating the desired steering wheel angle feedforward control quantity under low-speed conditions is as follows: This is combined with the application of the vehicle kinematics model under low-speed conditions, as shown in the equation:

[0113]

[0114] Where: ω′ is the derivative of ω with respect to distance; δ f θ is the front wheel steering angle; l is the wheelbase.

[0115] The steering gear ratio formula is:

[0116]

[0117] Where, δ f Indicates the front wheel steering angle, δ sw Indicates the steering wheel angle.

[0118] Combined with the desired yaw rate ω obtained in the previous step under low-speed conditions d Using the linear state feedback control law for the virtual control quantity, the steering transmission ratio relationship, and the vehicle kinematics model formula for the above low-speed conditions, the desired steering wheel angle feedforward control quantity under low-speed conditions can be obtained, as shown in the following equation:

[0119]

[0120] It should be noted that the lateral controller for low-speed automated driving vehicles has no feedback control element, therefore the control law under low-speed conditions is as follows:

[0121] δ w,ls =δ w,ff,ls .

[0122] In this embodiment, the specific calculation process further includes calculating the desired steering wheel angle of the high-speed controller through the high-speed autonomous driving lateral controller; specifically, based on the current vehicle speed, vehicle center of gravity sideslip angle, relative lateral position deviation between the vehicle and the target path, heading angle deviation, and target path curvature, the desired steering wheel angle feedforward control quantity under high-speed conditions is calculated through the high-speed autonomous driving lateral controller; the desired yaw rate of the high-speed controller and the current vehicle yaw rate are used to calculate the steering wheel angle feedback control quantity under high-speed conditions; and the sum of the desired steering wheel angle feedforward control quantity and the steering wheel angle feedback control quantity under high-speed conditions is output as the desired steering wheel angle of the high-speed controller.

[0123] The desired steering wheel angle feedforward control value under high-speed conditions is calculated using the following formula:

[0124]

[0125]

[0126]

[0127] Where, δ w,ff,hs ψ represents the desired steering wheel angle feedforward control value under high-speed conditions. d This represents the virtual control quantity, namely the desired yaw rate of the high-speed controller, g. ψ (v) represents the steady-state gain, ii wf The steering ratio is defined as the front wheel steering angle versus the steering wheel steering angle; r represents the relative lateral position deviation between the vehicle and the target path; θ represents the relative heading angle deviation between the vehicle speed and the target path; k represents the curvature of the target path; η represents linear state feedback control; m represents the vehicle mass; v represents the vehicle speed; and C... f C represents the lateral stiffness of a single front wheel. r The l represents the lateral stiffness of a single rear wheel. f The distance l represents the distance from the center of mass to the front axle. r This indicates the distance from the center of mass to the rear axle.

[0128] The steering wheel angle feedback control quantity under high-speed conditions is calculated using the following formula:

[0129] δ w,fb =k ω (ω d -ω)

[0130] Where, δ w,fb k represents the steering wheel angle feedback control quantity under high-speed conditions. ω ω represents the feedback coefficient. dω represents the virtual control quantity, i.e., the expected yaw rate of the high-speed controller, where ω represents the current yaw rate of the vehicle.

[0131] The above determines the specific desired yaw rate ω of the high-speed controller. d After establishing a linear state feedback control law for the virtual control quantity, the specific process for calculating the desired steering wheel angle feedforward control quantity under high-speed conditions is as follows:

[0132] A two-degree-of-freedom vehicle dynamics model is established, with the state equations as follows:

[0133]

[0134] Where m is the vehicle mass, v is the vehicle speed, β is the vehicle's sideslip angle, β0 is the initial value of the vehicle's sideslip angle, ω is the vehicle's yaw rate, ω0 is the initial value of the vehicle's yaw rate, and C is the vehicle's yaw rate. f The lateral stiffness of a single front wheel, C r Lateral stiffness of a single rear wheel, l f The distance from the center of gravity to the front axle, l r The distance from the center of gravity to the rear axle, I z The moment of inertia of the vehicle about the z-axis, δ f Front wheel steering angle.

[0135] steady state

[0136] Then the centroid sideslip angle β at steady state ss and steady-state yaw rate ω ss As shown in the formula:

[0137]

[0138] Their steady-state gains are as follows:

[0139]

[0140]

[0141]

[0142] Where m is the vehicle mass, v is the vehicle speed, and C is the vehicle speed. f The lateral stiffness of a single front wheel, C r Lateral stiffness of a single rear wheel, l f The distance from the center of gravity to the front axle, l r The distance from the center of gravity to the rear axle.

[0143] By ω ss=g ω (v)δ f From the steering gear ratio relationship, we can obtain:

[0144] The steady-state yaw rate is the desired yaw rate of the high-speed controller described above, i.e., ω. ss =ω d The steering wheel angle feedforward control value under high-speed conditions can be obtained as follows:

[0145]

[0146] Among them, g ω (v) Steady-state gain, ω d The desired yaw rate of the high-speed controller, ii wf Steering ratio between front wheel turning angle and steering wheel turning angle.

[0147] It should be noted that the high-speed autonomous driving lateral controller incorporates a feedback loop to account for external disturbances and system uncertainties. The expected steering wheel angle of the high-speed controller's feedback loop is as follows:

[0148] δ w,fb =k ω (ω d -ω)

[0149] Where, k ω Feedback coefficient, ω d Given the desired yaw rate of the high-speed controller and ω as the current yaw rate of the vehicle, the control law for high-speed operation, obtained from feedforward and feedback, is as follows:

[0150] δ w,hs =δ w,ff,hs +δ w,fb

[0151] Where, δ w,ff,hs Steering wheel angle feedforward control quantity under high-speed conditions, δ w,fb Steering wheel angle feedback control quantity under high-speed conditions.

[0152] Specifically, the total expected steering wheel angle is calculated based on the expected steering wheel angle of the low-speed controller, the expected steering wheel angle of the high-speed controller, and the smooth transition coefficient corresponding to the low-speed controller or the high-speed controller.

[0153] Specifically, the smooth transition coefficients for the low-speed controller and the high-speed controller are calculated using the following formula:

[0154]

[0155] Where f represents the smooth transition coefficient, v represents the current vehicle speed, and v fading,start Indicates a smooth initial vehicle speed, v fading,width This indicates the width of the smooth vehicle speed.

[0156] After determining the smooth transition between the low-speed and high-speed controllers, the total desired steering wheel angle is calculated using the following formula:

[0157] δ w =fδ w,hs +(1-f)δ w,ls

[0158] Where, δ w δ represents the total expected steering wheel angle. w,hs δ represents the desired steering wheel angle of the high-speed controller. w,ls denoted by , where represents the desired steering wheel angle of the low-speed controller, and f represents the smooth transition coefficient.

[0159] Furthermore, the final steering wheel angle, obtained by limiting the total desired steering wheel angle of the vehicle through both steering wheel angle and steering wheel angle change rate limits, is output to the steering controller. The steering controller then performs steering control based on this final steering wheel angle. In other words, the desired steering wheel angle and its change rate are limited by considering the performance limits of the EPS system of the selected vehicle model and the handshake logic between the EPS and lateral control. Specifically, the limits refer to the upper and lower limits. After limiting, the final steering wheel angle control output is given to the EPS, enabling vehicle motion response and cyclical control to track the target path.

[0160] Figure 2 shows a schematic diagram of an embodiment of an autonomous driving lateral control system provided by the present invention. In this embodiment, the system includes:

[0161] The vehicle data acquisition module is used to acquire in real time the vehicle's current speed, yaw rate, sideslip angle, lateral deviation between the vehicle and the target path, heading angle deviation, and target path curvature.

[0162] The lateral controller selection module is used to determine the current driving status of the vehicle based on the current vehicle speed, and select the corresponding autonomous driving lateral controller based on the current driving status of the vehicle.

[0163] The steering wheel angle calculation module takes the vehicle's current speed, yaw rate, sideslip angle, lateral deviation between the vehicle and the target path, heading angle deviation, and target path curvature as inputs to the corresponding autonomous driving lateral controller for calculation, obtaining the vehicle's total desired steering wheel angle. The final steering wheel angle, obtained by limiting the steering wheel angle and the rate of change of the total desired steering wheel angle, is then output to the steering controller. The steering controller then performs steering control based on the final steering wheel angle.

[0164] In another aspect, the present invention also provides an automobile in which the vehicle is steered by the aforementioned autonomous driving lateral control system.

[0165] It should be noted that the system described in the above embodiments corresponds to the method described in the above embodiments. Therefore, the parts of the system described in the above embodiments that are not described in detail can be obtained by referring to the content of the method described in the above embodiments, and will not be repeated here.

[0166] In summary, implementing the embodiments of the present invention has the following beneficial effects:

[0167] The autonomous driving lateral control method, system, and vehicle provided by this invention select corresponding high-speed and low-speed autonomous driving lateral controllers based on vehicle speed. The inputs to the entire controller are the lateral deviation between the vehicle and the target path at the current moment, the heading angle deviation, the curvature of the target path, the vehicle's current speed, yaw rate, and the vehicle's center of gravity sideslip angle. The corresponding controllers calculate the desired steering wheel angle at high and low speeds. The calculation results of the high-speed and low-speed autonomous driving lateral controllers are selected or smoothed, and after amplitude limiting, the final steering wheel angle control output is given to the EPS (Electrical Power Steering) system. The vehicle motion response is cyclically controlled to achieve target path tracking.

[0168] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A vehicle lateral control method, characterized in that, include: The system acquires the vehicle's current speed, yaw rate, sideslip angle, lateral deviation, heading deviation, and target path curvature in real time. Based on the current speed, it determines the vehicle's driving state and selects the appropriate lateral control unit. The acquired data (vehicle speed, yaw rate, sideslip angle, lateral deviation, heading deviation, and target path curvature) are input to the corresponding lateral control unit for calculation, yielding the vehicle's total desired steering wheel angle. The steering controller performs steering control based on the desired steering wheel angle; the lateral control system includes a low-speed lateral controller and a high-speed lateral controller; wherein, determining the current vehicle's driving state based on the current vehicle speed and selecting the corresponding lateral controller based on the current vehicle's driving state specifically includes: comparing the current vehicle speed with a preset smoothing starting speed and a smoothing speed width; if the current vehicle speed is less than the smoothing starting speed, the current vehicle's driving state is determined to be low speed, and the low-speed lateral controller is selected; if the current vehicle speed is greater than the sum of the smoothing starting speed and the smoothing speed width, the current vehicle's driving state is determined to be high speed, and the high-speed lateral controller is selected; if If the current vehicle speed is greater than the smoothing starting speed and less than the sum of the smoothing starting speed and the smoothing speed width, then a smooth transition is performed between the high-speed driving lateral controller and the low-speed driving lateral controller; and, obtaining the total expected steering wheel angle of the vehicle specifically includes: calculating the expected steering wheel angle of the low-speed controller through the low-speed driving lateral controller; calculating the expected steering wheel angle of the high-speed controller through the high-speed driving lateral controller; and calculating the total expected steering wheel angle based on the expected steering wheel angle of the low-speed driving lateral controller, the expected steering wheel angle of the high-speed driving lateral controller, and the smoothing transition coefficients corresponding to the low-speed driving lateral controller and the high-speed driving lateral controller.

2. The method as described in claim 1, characterized in that, The step of calculating the desired steering wheel angle of the low-speed lateral controller through the low-speed driving lateral controller specifically includes: calculating the desired steering wheel angle feedforward control quantity under low-speed conditions through the low-speed driving lateral controller based on the current vehicle speed, vehicle center of gravity sideslip angle, relative lateral position deviation between the vehicle and the target path, heading angle deviation, and target path curvature; and outputting the desired steering wheel angle feedforward control quantity under low-speed conditions as the desired steering wheel angle of the low-speed driving lateral controller; wherein, the desired steering wheel angle feedforward control quantity under low-speed conditions is calculated according to the following formula: in, This represents the desired steering wheel angle feedforward control value under low-speed conditions. This indicates the relative lateral position deviation of the vehicle from the target path. This indicates the deviation of the vehicle speed from the target path in terms of heading angle. Indicates the curvature of the target path. Indicates the vehicle's wheelbase. This indicates the steering gear ratio between the front wheel turning angle and the steering wheel turning angle. The constant coefficient is 0. The constant coefficient is 1.

3. The method as described in claim 1, characterized in that, The calculation of the desired steering wheel angle by the high-speed lateral controller specifically includes: calculating the desired steering wheel angle feedforward control quantity under high-speed conditions using the high-speed lateral controller based on the current vehicle speed, vehicle center of gravity sideslip angle, relative lateral position deviation between the vehicle and the target path, heading angle deviation, and target path curvature; calculating the desired steering wheel angle feedback control quantity under high-speed conditions using the high-speed lateral controller based on the desired yaw rate of the high-speed controller and the current vehicle yaw rate; and outputting the sum of the desired steering wheel angle feedforward control quantity and the steering wheel angle feedback control quantity as the desired steering wheel angle of the high-speed controller; wherein, the desired steering wheel angle feedforward control quantity under high-speed conditions is calculated according to the following formula: + in, This represents the desired steering wheel angle feedforward control value under high-speed operating conditions. This represents the virtual control quantity, specifically the desired yaw rate of the high-speed controller. Represents steady-state gain. This indicates the steering gear ratio between the front wheel turning angle and the steering wheel turning angle. This indicates the relative lateral position deviation of the vehicle from the target path. This indicates the deviation of the vehicle speed from the target path in terms of heading angle. Indicates the curvature of the target path. This indicates linear state feedback control. Indicates the overall vehicle weight. Indicates vehicle speed. This indicates the lateral stiffness of a single front wheel. This indicates the lateral stiffness of a single rear wheel. This represents the distance from the center of gravity to the front axle. This indicates the distance from the center of mass to the rear axle.

4. The method as described in claim 3, characterized in that, The steering wheel angle feedback control quantity under high-speed conditions is calculated using the following formula: in, This indicates the steering wheel angle feedback control value under high-speed operating conditions. Indicates the feedback coefficient. This represents the virtual control quantity, specifically the desired yaw rate of the high-speed controller. This indicates the current yaw rate of the vehicle.

5. The method as described in claim 1, characterized in that, The smooth transition coefficients corresponding to the low-speed lateral controller and the high-speed lateral controller are calculated using the following formula: in, Indicates the smooth transition coefficient. Indicates the current vehicle speed. Indicates a smooth initial vehicle speed. This indicates the width of the smooth vehicle speed.

6. The method as described in claim 5, characterized in that, The total expected steering wheel angle is calculated using the following formula: in, This represents the total expected steering wheel angle. This indicates the desired steering wheel angle of the high-speed controller. This indicates the desired steering wheel angle of the low-speed controller. This represents the smooth transition coefficient.

7. An autonomous driving lateral control system for implementing the method as described in any one of claims 1-6, characterized in that, include: The vehicle data acquisition module is used to acquire in real time the vehicle's current speed, yaw rate, sideslip angle, lateral deviation between the vehicle and the target path, heading angle deviation, and target path curvature. A lateral controller selection module is used to determine the current vehicle's driving state based on the current vehicle speed and select the corresponding lateral controller accordingly. Specifically, determining the current vehicle speed and selecting the appropriate lateral controller involves: comparing the current vehicle speed with a preset smoothing starting speed and a smoothing speed width; if the current vehicle speed is less than the smoothing starting speed, the current vehicle's driving state is determined to be low speed, and the low-speed lateral controller is selected; if the current vehicle speed is greater than the sum of the smoothing starting speed and the smoothing speed width, the current vehicle's driving state is determined to be high speed, and the high-speed lateral controller is selected; if the current vehicle speed is greater than the smoothing starting speed but less than the sum of the smoothing starting speed and the smoothing speed width, a smooth transition is performed between the high-speed lateral controller and the low-speed lateral controller. A steering wheel angle calculation module is used to calculate the current vehicle speed, vehicle yaw rate, and vehicle center of gravity. The sideslip angle, lateral deviation between the vehicle and the target path, heading angle deviation, and target path curvature are input to the corresponding lateral control system for calculation, resulting in the total desired steering wheel angle of the vehicle. This total desired steering wheel angle is then passed through a steering wheel angle limiter and a steering wheel angle change rate limiter to obtain the final steering wheel angle, which is output to the steering controller. The steering controller then performs steering control based on the final steering wheel angle. Specifically, obtaining the total desired steering wheel angle includes: calculating the desired steering wheel angle of the low-speed lateral control system using the low-speed lateral control system; calculating the desired steering wheel angle of the high-speed lateral control system using the high-speed lateral control system; and calculating the total desired steering wheel angle based on the desired steering wheel angles of the low-speed and high-speed lateral control systems, as well as the corresponding smoothing transition coefficients. The lateral control system includes both a low-speed and a high-speed lateral control system.

8. A car, characterized in that, The vehicle is steered using the autonomous driving lateral control system as described in claim 7.

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