CN115715263A - Steering control method and device - Google Patents
Steering control method and device Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L15/00—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles
- B60L15/20—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
- B60W30/00—Purposes of road vehicle drive control systems not related to the control of a particular sub-unit, e.g. of systems using conjoint control of vehicle sub-units
- B60W30/02—Control of vehicle driving stability
- B60W30/045—Improving turning performance
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
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Abstract
A vehicle steering control method and device, the method includes: determining a tire force range according to a road adhesion coefficient and real-time load transfer of a vehicle, determining a steering coordination rate of autonomous steering and differential steering according to the tire force range, wherein the steering coordination rate indicates weights of the autonomous steering and the differential steering, determining a target wheel angle and a target yaw moment according to the steering coordination rate, a yaw rate error and the like, providing the target wheel angle to an autonomous steering system, and providing the target yaw moment to the differential steering system. The method is a steering coordination control method of autonomous steering and differential steering based on trajectory tracking, and can improve the trajectory tracking precision.
Description
The application relates to the technical field of intelligent vehicles, in particular to a steering control method and device.
As a vehicle control method, there is a Steering control method in which autonomous Steering and Differential Steering are caused to work together to track a vehicle so as to cause the vehicle to travel along a predetermined path and trajectory, and specifically, in this method, when only front-wheel autonomous Steering is performed and lateral deviation cannot be suppressed to a small range (that is, lateral deviation is excessively large), the front-wheel autonomous Steering is assisted by Differential Steering (DS), and the vehicle can be caused to travel along the predetermined path with certainty.
However, in the above-described steering control method, the autonomous steering and the differential steering are caused to function together for trajectory tracking only when the lateral deviation caused by the autonomous steering is large, the cooperative function between the autonomous steering and the differential steering is not sufficiently exerted, the lateral response speed is slow in some driving conditions (for example, high-speed driving conditions or other limit conditions), and the tracking accuracy is low.
Disclosure of Invention
The present application provides a steering control method and apparatus, etc., which can improve the trajectory tracking accuracy.
A first aspect of the present application provides a steering control method, which includes: acquiring a tire force range; determining a steering coordination rate based on the tire force range, the steering coordination rate indicating a weight of a steering amount generated by an autonomous steering system of the vehicle and a steering amount generated by a differential steering system of the vehicle; acquiring a yaw angular velocity error; determining a target wheel corner and a target yaw moment according to the yaw velocity error and the steering coordination rate; and sending a first control command, wherein the first control command comprises a control command used for enabling the autonomous steering system to generate a target wheel angle and a control command used for enabling the differential steering system to generate a target yaw moment.
By adopting the steering control method, the steering coordination rate, namely the weight occupied by the autonomous steering and the differential steering is determined according to the tire force range, so that the tire force can be fully exerted, the lateral response speed is improved, the turning radius is reduced, and the track tracking precision is improved.
In addition, since the steering coordination rate is determined in consideration of the tire force range, the steering stability and safety of the vehicle can be improved even in the limit running mode (the mode such as low road adhesion coefficient and high-speed running).
In addition, the steering control method provided by the embodiment utilizes the dual systems of the autonomous steering system and the differential system to carry out coupling steering control, has a redundancy function, and can improve the running safety of the vehicle under the coping limit working condition. In addition, for example, when the autonomous steering system fails or malfunctions, the differential steering system can be operated, and safety of vehicle running can be improved.
As one possible implementation manner of the first aspect, in the above method, a road adhesion coefficient and/or a load variation amount of a plurality of wheels of the vehicle is acquired; the tire force range is determined from the road adhesion coefficient and/or the load variation.
The tire force range is determined in consideration of the road surface adhesion coefficient and the load variation amount of the wheel, and the tire force range can be reliably planned.
As one possible implementation manner of the first aspect, one or more of the acceleration in the three directions of the transverse direction and the longitudinal direction of the vehicle, the roll motion state parameter or the pitch motion state parameter is acquired; the load change is determined from one or more of the acceleration, the roll state of motion parameter, or the pitch state of motion parameter.
The load change amount is determined in consideration of the acceleration in the three lateral and vertical directions of the vehicle, the roll motion state parameter, or the pitch motion state parameter, and the load change amount can be reliably determined.
As one possible implementation manner of the first aspect, the determining the steering coordination rate according to the tire force range may specifically include: acquiring a tire transverse relative utilization rate and a preset basic coordination rate, wherein the tire transverse relative utilization rate indicates the ratio of a transverse tire force relative to a total tire force, and the basic coordination rate is an initial parameter of a steering coordination rate; and determining the steering coordination rate according to the basic coordination rate, the lateral relative utilization rate of the tire and the tire force range.
The steering amount may typically be determined by the steering radius or the yaw angle.
A second aspect of the present application provides a vehicle steering control apparatus, which includes a processing module and a transceiver module, wherein the processing module is configured to obtain a tire force range and a yaw rate error, determine a steering coordination rate according to the tire force range, the steering coordination rate indicating a weight of a steering amount generated by an autonomous steering system of a vehicle and a steering amount generated by a differential steering system of the vehicle, and determine a target wheel angle and a target yaw moment according to the yaw rate error and the steering coordination rate; the transceiver module is used for sending a first control instruction, and the first control instruction comprises a control instruction for enabling the autonomous steering system to generate a target wheel turning angle and a control instruction for enabling the differential steering system to generate a target yaw moment.
As a possible implementation manner of the second aspect, the processing module is specifically configured to obtain a road adhesion coefficient and/or a load variation amount of a plurality of wheels of the vehicle; the tire force range is determined from the road adhesion coefficient and/or the load variation.
As a possible implementation manner of the second aspect, the processing module is specifically configured to acquire one or more of an acceleration in three directions of a transverse direction and a vertical direction of the vehicle, a roll motion state parameter, or a pitch motion state parameter; the load change is determined from one or more of the acceleration, the roll state of motion parameter, or the pitch state of motion parameter.
As a possible implementation manner of the second aspect, the processing module is specifically configured to obtain a tire lateral relative utilization rate and a preset basic coordination rate, where the tire lateral relative utilization rate indicates a ratio of lateral tire force relative to total tire force, and the basic coordination rate is an initial parameter of the steering coordination rate; and determining the steering coordination rate according to the basic coordination rate, the lateral relative utilization rate of the tire and the tire force range.
The steering amount may be determined by a steering radius or a yaw angle.
The technical effects of the second aspect of the present application are substantially the same as those described in the first aspect, and the description thereof will not be repeated here.
A third aspect of the present application provides a computing device comprising a processor and a memory, the memory storing program instructions that, when executed by the processor, cause the processor to perform any of the methods described in the first aspect.
A fourth aspect of the present application provides a computer-readable storage medium storing program instructions that, when executed by a computer, cause the computer to perform any one of the methods described in the first aspect.
A fifth aspect of the present application provides a computer program product comprising program instructions which, when executed by a computer, cause the computer to perform any of the methods described in the first aspect.
These and other aspects of the present application will be more readily apparent from the following description of the embodiment(s).
Fig. 1 is a schematic structural view of a vehicle to which a steering control method according to an embodiment of the present application is applied;
FIG. 2 is a flow chart of a steering control method provided in an embodiment of the present application;
fig. 3 is a block diagram schematically illustrating a structure of a steering control device according to an embodiment of the present application;
FIG. 4 is a schematic structural diagram of an electronic control unit according to an embodiment of the present application;
FIG. 5 is a diagram illustrating a steering control method according to an embodiment of the present application;
FIG. 6 is a schematic illustration of vehicle conditions involved in trajectory tracking control in an embodiment of the present application;
FIG. 7 is a schematic illustration of an attachment ellipse referred to in one embodiment of the present application;
FIG. 8 is a schematic illustration of the coordination rate ranges involved in one embodiment of the present application;
FIG. 9 is a simplified diagram illustrating analysis of vehicle body motion forces involved in the description of one embodiment of the present application;
FIG. 10 is a schematic illustration of tire force ranges involved in one embodiment of the present application;
fig. 11 is a schematic diagram of a (vehicular) steering system architecture to which the steering control method according to an embodiment of the present application is applied.
As a control method of a vehicle, there is a steering control method of performing trajectory tracking by causing autonomous steering and differential steering to work together in order to cause the vehicle to travel along a predetermined path and trajectory, and specifically, in this method, when only front wheel autonomous steering is performed and lateral deviation cannot be suppressed within a small range (that is, lateral deviation is excessively large), the front wheel autonomous steering is assisted by the differential steering, and the vehicle can be caused to travel reliably along the predetermined path.
However, in the above-described steering control method, the autonomous steering and the differential steering are caused to work together to track only when the lateral deviation caused by the autonomous steering is large, and the cooperative action between the autonomous steering and the differential steering is not sufficiently exerted, so that the lateral response speed is slow in some driving conditions (for example, high-speed driving conditions or other limit conditions), and the tracking accuracy is low.
In view of this, an embodiment of the present application provides a steering control method, so as to improve the tracking accuracy.
Before describing the steering control method, a description will be given of a related structure of a vehicle to which the steering control method is applied.
Fig. 1 is a schematic structural diagram of a vehicle to which a steering control method according to an embodiment of the present application is applied. As shown in fig. 1, the vehicle 100 is a distributed drive vehicle, in which in-wheel motors 120 are disposed in 4 wheels 110, respectively, and the wheels 110 are driven and braked by the in-wheel motors 120. In addition, in-wheel motor 120 may be independently controlled (motor controller not shown) to generate differential torque by applying different torques to coaxial wheels 110, thereby generating differential steering of vehicle 100. That is, the in-wheel motor 120 constitutes a Differential Steering (DS) system.
In another example of the distributed drive vehicle, wheel-side motors may be provided near the 4 wheels 110 instead of the in-wheel motors 120, and the wheel-side motors may be connected to the wheels 110 via transmission mechanisms, respectively, to drive and brake the wheels 110. In addition, the method of the embodiment of the application can also be applied to other types of vehicles.
As shown in fig. 1, the vehicle 100 further includes a steering wheel 20, a torque and rotation angle sensor 30, a steering motor 40, a clutch 70, a reduction gear 50, a steering gear 60, and a steering controller 90. The steering wheel 20 is used for steering operation by the driver. The torque and rotation angle sensor 30 detects a rotation angle of the steering wheel 20 and a torque received. The steering motor 40 is used for driving the steering wheel 20 to rotate. The reduction mechanism 50 is used to reduce the rotation speed of the steering motor 40 and transmit the rotation speed to the steering wheel 20. The clutch 70 is provided between the steering motor 40 and the reduction mechanism 50, and controls on/off of connection between the driving motor 40 and the reduction mechanism 50. The steering gear 60 is used to convert the rotational motion of the steering wheel 20 into a linear motion or the like and rotationally drive the two front wheels 110. The steering Controller 90 is configured to control the steering motor 40 and the clutch 70 in accordance with an operation of the steering wheel 20 by the driver or a command from a Vehicle Domain Controller (VDC) 10 described later, and the steering Controller 90 may be configured by an Electronic Control Unit (ECU). The torque and rotation angle sensor 30, the Steering motor 40, the clutch 70, the reduction mechanism 50, the Steering gear 60, the Steering controller 90, and the like constitute an Electric Power Steering (EPS). The EPS system includes the above-described components, as well as components such as a vehicle speed sensor.
This EPS system has an assist function of assisting a steering operation of a driver, and also has an autonomous steering function of actively steering the wheels 110 in accordance with an instruction from a controller (for example, the entire vehicle range controller 10), and therefore can be said to constitute an autonomous steering system. As other examples of the autonomous steering system, a four-wheel steering (4 WS) system may also be employed.
In addition, as shown in fig. 1, the vehicle 100 has a whole domain controller 10, and the whole domain controller 10 is configured to provide services to vehicle parts of a vehicle body domain including a door/window lifting controller, a power mirror, an air conditioner, a central door lock, and the like, and vehicle parts of a chassis domain. The vehicle parts in the chassis area include vehicle parts in a brake system, vehicle parts in a steering system, vehicle parts in an acceleration system, such as a throttle, and the like.
The entire area controller 10 also has the overall control function of the differential steering system and the autonomous steering system, and under the control of this, when it is necessary to control the vehicle 100 to steer, the differential steering system and the autonomous steering system may be caused to function separately, or the differential steering system and the autonomous steering system may be caused to function together (simultaneously). By performing the steering control by causing the differential steering system and the autonomous steering system to function together, it is possible to obtain an effect of improving the vehicle stability at the time of steering.
A steering control method provided in an embodiment of the present application is described below with reference to fig. 2 to 4, and the steering control method is a steering coordination control method for coordinating an autonomous steering system and a differential steering system based on trajectory tracking, and may be applied to automatic driving or manual driving as a driving assistance function.
Fig. 2 is a flowchart of a steering control method according to an embodiment of the present application. The steering control method is executed by a control device, which is a whole vehicle domain controller in the embodiment, and specifically, the whole vehicle domain controller may include a function module for implementing vehicle dynamics control, and the function module executes the steering control method. In addition, as another embodiment, the steering control method may be executed by a controller for implementing vehicle dynamics control, which is independent of the vehicle controller.
The following describes in detail the steering control method provided in the embodiment of the present application, and the method may specifically include the following:
s1, obtaining vehicle dynamics related informationAnd (4) information. Such information includes the real-time lateral and longitudinal position of the vehicle acquired by a camera or the like of the vehicle. The vehicle dynamics-related parameter information includes a heading angle obtained by an Inertial Measurement Unit (IMU) of the vehicle
Angle of roll theta Roll Pitch angle θ Pitch Longitudinal acceleration a x Lateral acceleration a y Vertical acceleration a z And also includes a yaw rate r, a road adhesion coefficient μ, and the like, which are estimated by calculation. For estimating the yaw rate, the ESP system receives an angle signal from a steering wheel torque angle sensor, and in combination with a vehicle speed signal, estimates a vehicle body yaw rate value to be applied to the vehicle speed and the steering wheel angle. Here, the inertial measurement unit is a device for measuring the three-axis attitude angle (or angular rate) and acceleration of an object, and generally, an inertial measurement unit includes three single-axis accelerometers and three single-axis gyros, the accelerometers detect acceleration signals of the object in three independent axes of a carrier coordinate system, and the gyros detect the angular velocity and acceleration of the object in a three-dimensional space.
The estimation of the road adhesion coefficient is briefly described below. The road adhesion coefficient is equal to the ratio of the longitudinal force of the tire to the vertical load, the estimation of the road adhesion coefficient is the estimation of the maximum adhesion rate, the adhesion coefficient mu and the slip rate s of the tire have a mu-s curve relation, the slip rate can be obtained by estimating and calculating signals such as wheel speed, vehicle speed and ground force, and the adhesion coefficient can be calculated by combining with the longitudinal acceleration.
In addition, the yaw rate r and the road adhesion coefficient μmay be estimated by the entire vehicle domain controller, or may be acquired by the entire vehicle domain controller from another controller.
S2, determining a lateral displacement error and a course angle error according to the vehicle real-time position signal, determining a path plan according to the lateral displacement error and the course angle error, and obtaining a target yaw rate. Specifically, for example, assuming that the vehicle travels at a constant speed during trajectory tracking, the path tracking target may specifically consider the lateral tracking accuracy, i.e., pursuing the lateral error and the heading angle error to be minimum, and obtain the target yaw rate by using a pre-aiming control algorithm, for example.
And S3, planning a tire force dynamic range (also referred to as a tire force range) based on the road surface adhesion coefficient and/or the vertical load (also referred to as a load) variation. The tire force range indicates the distributable range of tire force. The road adhesion coefficient has an influence on the tire force, and thus the tire force range can be determined from the road adhesion coefficient. In addition, the variation of the vertical load applied to the wheel changes the tire force range of the wheel, so that the tire force range can be determined according to the variation of the vertical load. The amount of change in the vertical load may be determined based on one or more of the acceleration in the three lateral and vertical directions of the vehicle, a roll motion state parameter (roll angle), or a pitch motion state parameter (pitch angle). And determining the real-time vertical load of each wheel according to the variable quantity of the vertical load, and determining the tire force range of each wheel according to the real-time vertical load.
And S4, determining the steering coordination rate according to the basic coordination rate and the tire force range. The steering coordination ratio (also simply referred to as a coordination ratio) may be referred to as a control coefficient of the autonomous steering controller and the differential steering controller, and may be referred to as a weight indicating the autonomous steering and the differential steering, or a weight indicating a steering amount by the autonomous steering system of the vehicle and a steering amount by the differential steering system of the vehicle. The steering amount here may be determined by a steering radius or a yaw angle. The basic coordination rate is an initial parameter of the steering coordination rate, and may be set in advance based on experiments or experience, for example.
And S5, determining a target wheel rotation angle and a target yaw moment according to the yaw rate error and the steering coordination rate. After the steering coordination rate, i.e., the weights of the autonomous steering and the differential steering are determined in S4, the target wheel angle generated by the autonomous steering system and the target yaw moment generated by the differential steering system may be determined based on the yaw rate error in combination with the weights of the autonomous steering and the differential steering. It is understood that the yaw-rate error is obtained from the target yaw-rate and the current yaw-rate.
And S6, sending a control command based on the target wheel rotation angle and the yaw moment. That is, control commands including a control command for causing the autonomous steering system to generate a target wheel angle and a control command for causing the differential steering system to generate a target yaw moment are generated and transmitted based on the target wheel angle and the target yaw moment.
By adopting the steering control method, the steering coordination rate, namely the weights of the autonomous steering and the differential steering are determined according to the tire force range, so that the tire force can be fully exerted, the lateral response speed is improved, the turning radius is reduced, and the track tracking precision is improved.
In addition, since the steering coordination rate is determined in consideration of the tire force range, the steering stability and safety of the vehicle can be improved even in the limit running mode (the mode such as low road adhesion coefficient and high-speed running).
In addition, the steering control method provided by the embodiment does not need to additionally increase vehicle-mounted hardware (such as hardware required by the hub motor to drive the electric automobile).
Further, in the present embodiment, the vehicle state quantity threshold value is corrected in consideration of the road surface adhesion condition and/or the vertical load shift, and the steering coordination rate is determined on the basis thereof, so that the vehicle running safety is improved.
In addition, the steering control method provided by the embodiment utilizes the dual systems of the autonomous steering system and the differential system to perform coupling steering control, has a redundancy function, and can improve the vehicle running safety under the coping extreme condition. In addition, for example, when the autonomous steering system fails or malfunctions, the differential steering system can be operated, and safety of vehicle running can be improved.
In addition, when the method is applied to manual driving, the method of the embodiment can reduce the operation of the driver and reduce the driving load.
Alternatively, in S2, the target centroid slip angle may be determined, and in S5, the target wheel rotation angle and yaw moment may be determined according to the yaw rate error and the centroid slip angle error, so that the vehicle may maintain a smooth posture during steering, improving the comfort of the occupant.
Fig. 3 is a block diagram illustrating a structure of a steering control device according to an embodiment of the present application. The steering control apparatus is used to execute the steering control method described with reference to fig. 2. As shown in fig. 3, the steering control device 200 includes a processing module 210 and a transceiver module 220, where the processing module 210 may be configured to execute the above S2-S5, and the transceiver module 220 may be configured to execute the above S1 and S6.
The steering control device may be constituted by an electronic control unit ECU, which is a control device including an integrated circuit for realizing a series of functions such as analysis, processing, and transmission of data. As shown in fig. 4, an embodiment of the present application provides an ECU including a microcomputer (microcomputer), an input circuit, an output circuit, and an analog-to-digital (a/D) converter.
The main function of the input circuit is to pre-process the input signal (e.g. from the sensor), which varies from input signal to input signal and from processing method to processing method. Specifically, because there are two types of input signals: analog signals and digital signals, the input circuit may include an input circuit that processes analog signals and an input circuit that processes digital signals.
The A/D converter has the main function of converting analog signals into digital signals, and the analog signals are preprocessed by the corresponding input circuit and then input into the A/D converter for processing and converting into digital signals received by the microcomputer.
The output circuit is a device that establishes communication between the microcomputer and the actuator. Its function is to convert the processing result from microcomputer into control signal to drive the actuator to work. The output circuit is generally a power transistor, and controls an electronic circuit of the actuator by turning on or off according to an instruction of the microcomputer.
The microcomputer includes a Central Processing Unit (CPU), a memory, and an input/output (I/O) interface, and the CPU is connected to the memory and the I/O interface through a bus, and can exchange information with each other through the bus. The memory may be a read-only memory (ROM) or a Random Access Memory (RAM). The I/O interface is a connection circuit for exchanging information between a Central Processing Unit (CPU) and an input circuit, an output circuit, or an a/D converter, and specifically, the I/O interface may be divided into a bus interface and a communication interface. The memory stores programs, and the CPU calls the programs in the memory to execute the steering control method described in the embodiment corresponding to FIG. 2.
In view of the above, an embodiment of the present application provides a computing device, where the computing device includes a processor and a memory, where the memory stores program instructions, and when the program instructions are executed by the processor, the steering control method described in the embodiment corresponding to fig. 2 is performed. In addition, the embodiment of the application also provides a computer readable storage medium (memory) and a computer program product which are included by the computing device.
A steering control method provided in an embodiment of the present application is described below with reference to fig. 5.
Fig. 5 is an explanatory diagram of a steering control method according to an embodiment of the present application.
The markers used in the following description will be briefly described first. In the following description, regarding the three-dimensional direction, x represents the longitudinal direction of the vehicle, y represents the lateral direction of the vehicle, and z represents the vertical direction of the vehicle, unless otherwise specified. In addition, regarding front, rear, left, and right, f denotes front, r denotes rear, l denotes left, and r denotes right. The letters "·" indicate a differential, one "·" a first-order differential, and two "·" a second-order differential. E.g. theta Roll Which represents the angle of the roll angle,
is the roll angular acceleration. In addition, unless otherwise specified, the meanings of the symbols in the entire specification are identical.
As shown in fig. 5, the steering control method of the present embodiment includes the following.
S10: and acquiring vehicle dynamics related parameter information so as to carry out path planning subsequently and determine a target front wheel corner and a target yaw moment by utilizing a track tracking controller (model) established based on a steering dynamics model.
Here, the vehicle dynamics-related parameter information includes a heading angle obtained by an inertial measurement unit of the vehicle
Roll angle theta Roll Angle of pitch theta Pitch Longitudinal acceleration a x Lateral acceleration a y Vertical acceleration a z The calculation and estimation also includes obtaining the yaw rate r, the road adhesion coefficient mu and the like. The yaw rate r and the road adhesion coefficient μmay be estimated by the entire vehicle domain controller, or may be acquired by the entire vehicle domain controller from another controller.
S20: according to the real-time position of the vehicle and other vehicle state signals, for example, a pre-aiming control algorithm is adopted to realize the tracking of the lateral displacement and the heading angle, and the target yaw velocity and the target mass center lateral deviation angle are obtained.
S30: based on the yaw rate error and the centroid yaw angle error, and in combination with a steering coordination rate described in detail below, a target front wheel steering angle and a target yaw moment are determined by using an established Model Predictive Control (MPC) trajectory tracking controller for front wheel steering and differential steering, and a command based thereon is output to cause the autonomous steering system to generate the target front wheel steering angle and cause the differential steering system to generate the target yaw moment.
MPC trajectory tracking control is a control method that aims at decomposing an optimization control problem of a longer time span, even an infinite time, into several optimization control problems of shorter time spans, or finite time spans, and still pursuing an optimal solution to some extent. Model predictive control consists of three elements: prediction model, online rolling optimization and feedback correction.
S40: and (3) deciding a coordination rate range according to the basic coordination rate of the front wheel steering and the differential steering, the transverse relative utilization rate of the tire and the vehicle posture state, wherein the coordination rate boundary is restrained by a tire force dynamic distribution area detailed below.
S50: and planning a tire force dynamic distribution area according to the acceleration of the vehicle in the transverse direction, the longitudinal direction and the vertical direction and the load transfer influence caused by the rolling and pitching motions based on the road adhesion coefficient.
S60: and solving to determine the steering coordination rate (namely solving to obtain the optimal coordination rate) according to a coordination control optimization model constructed based on the steering coordination rate and other constraint conditions.
S70: and determining EPS (electric power storage) required torque according to the target front wheel steering angle, determining required driving torque of each wheel according to the target yaw moment, and finally completing closed-loop control by the motor. Here, S70 may be performed by the controller of the EPS system and the controller of the in-wheel motor, respectively.
The contents of S20-S60 are described in more detail below.
S20: according to the real-time position of the vehicle and other vehicle state signals, for example, a pre-aiming control algorithm is adopted to realize the tracking of the lateral displacement and the heading angle, and the target yaw velocity and the target mass center lateral deviation angle are obtained.
The specific algorithm design is as follows:
fig. 6 is a schematic explanatory view of a vehicle state involved in the trajectory tracking control in one embodiment of the present application. The S-shaped curve in the figure is the target path of the vehicle and CG is the center of mass of the vehicle. Referring to fig. 5, the arc length of the starting point of the target path is defined as σ =0, and the arc length from the starting point to the point at time T is expressed as follows:
in the above equation, ρ (σ) represents the curvature at T on the path, and is related to the arc length of the point from the starting point.
The lateral error and the heading error of the vehicle are represented as follows:
the lateral error and the course error in the above formula are enabled to be globally asymptotically stable and converged to zero, and meanwhile, the stability requirement of the vehicle is met. When designing the trajectory tracking controller, the control target is:
with the global gradual stabilization of lateral errors and course errors as a target, a target yaw angular velocity is obtained through backstepping algorithm design as follows:
in the above formula, k 1 、k 2 Representing a weight coefficient, which is a constant greater than zero. k is a radical of 1 、k 2 The condition k needs to be satisfied 2 ＞k 1 v x To determine the progressive stability of the lateral error and the heading error.
In addition, the preview error may be expressed as follows:
e a ＝e+L sinψ (2-5)
in the above formula, L is the pre-aiming distance, e a For the pre-aiming error, making a small angle assumption on the course angle error, and simplifying the formula as follows:
e a ＝e+Lψ (2-6)
comparing formulas (2-4) and (2-6), L =1/k can be obtained 1 Then the target yaw rate can be further expressed as:
in addition, the target value of the lateral velocity is designed to tend to 0, that is:
because the centroid slip angle is the ratio of the lateral velocity to the longitudinal velocity, when the longitudinal velocity is fixed, the target centroid slip angle is zero.
S30: and determining a target front wheel turning angle and a target yaw moment by utilizing an established Model Predictive Control (MPC) trajectory tracking controller of front wheel steering and differential steering based on the yaw velocity error, the mass center slip angle error and the steering coordination rate.
The design of the trajectory tracking controller is described first.
Firstly, a front wheel steering dynamic model is established, and the front wheel is steered automatically to change a steering angle delta f As system inputs, the vehicle dynamics equations are expressed as follows:
the non-linear brush tire model will be used to calculate the longitudinal and lateral forces of the tire;
wherein the state quantities are:
x 1 ＝[r β] T
the input quantity is:
u 1 ＝δ f
then, a differential steering dynamics model is established, and a differential torque M is defined z As system inputs, the differential steering system can be represented as follows:
in the above formula, J f 、J r Respectively representing the equivalent yaw moment of inertia of the front and rear axles, d f 、d r Respectively representing front axle, rear axle equivalent damping, τ Af 、τ Ar Respectively representing the aligning moments, tau, of the front and rear tyres Ff 、τ Fr Representing front and rear tire friction torque, respectively.
The vehicle dynamics equation is expressed as follows:
M z ＝M f +M r ＝(F 2 -F 1 )l c +(F 4 -F 3 )l c
in the above formula, F 1 、F 2 Is the driving force of two front wheels, F 3 、F 4 Is the driving force of the two rear wheels, and a, b are the distances from the front and rear axles to the center of mass, respectively.
In the above formula, the state quantities are:
x 2 ＝[r β δ f δ r ] T
the input quantity is:
u 2 ＝M z
the vehicle dynamic model based on the active steering and the differential steering of the front wheels is uniformly written into the following nonlinear time-varying form:
for a distributed driving automobile, except for a front wheel EPS, the independent steering is realized, a differential steering system can be realized by a front double shaft and a rear double shaft, and the state and the input quantity of the differential steering system are as follows:
considering the track tracking error, the target value r of the following yaw angular velocity is satisfied * The stability of the device can be gradually improved; lateral stability requires that the system meet the following centroid slip angle target value beta * Thus, the system output is defined:
y＝[r β] T (3-6)
discretizing the state equation (3-4) to obtain a system model:
x k+1 -x k ＝T□f(x k ,u k ) (3-7)
and (3) simplifying calculation: the state quantity x (k) at the current moment k and the control input u (k-1) of the nonlinear model both need to be linearized:
Δx(k+1)＝A k Δx(k)+B k Δu(k)
obtaining a discretized linear time-varying prediction model:
x p+1,k ＝A p,k x p,k +B p,k u p,k +d p,k (3-9)
self-steering for the front wheels: in the MPC control process, the best track tracking effect is obtained by the minimum corner input, and an objective function is constructed:
in the above formula, Δ U is the control input increment, N p 、N c For prediction step number and control compensation, Q, R, respectivelyρ is the corresponding weight coefficient, and ε is the relaxation factor.
For differential steering trajectory tracking, the objective function is designed in the same way as follows:
based on the real-time calculated steering coordination rate, in order to obtain the optimal track tracking effect, the minimum turning angle and the minimum yawing moment are pursued, and a multi-objective optimization model is established as follows:
min J＝λ c J 1 (x(k),u 1 (k-1),ΔU(k))+(1-λ c )J 2 (x(k),u 2 (k-1),ΔU(k))
based on the optimization model, the optimal control increment sequence at the current moment can be obtained by solving as follows:
and finally, performing rolling optimization by taking the item 1 of the optimal control increment sequence as the current actual control quantity of the system, thereby obtaining the result of the whole control time sequence.
S40: and (3) deciding a coordination rate range according to the basic coordination rate of the front wheel steering and the differential steering, the transverse relative utilization rate of the tire and the vehicle posture state, wherein the coordination rate boundary is restrained by a tire force dynamic distribution area detailed below.
First, an experiment for comparing the front wheels EPS and the Differential Steering (DS) is performed in advance. Specifically, a certain front wheel corner and a differential yaw moment are input respectively, circular motion is performed at different vehicle speeds, and an actual driving steering radius R is recorded 1 (v x )，R 2 (v x ) The inputs (front wheel corner, yaw moment) are normalized separately to obtain the steering radius under each unit input:
in the above formula, δ f,test ，M Z,test Respectively representing the steering angle and differential torque input of the front wheel in the steering circumference experiment.
Therefore, for both control effects in the steering control, the weight occupied by the front wheel steering can be determined:
in the above formula, ω b,1 The basic coordination rate of the front wheel EPS in the circular motion lateral tracking control is represented, and is an initial parameter of the steering coordination rate.
The control states of the two systems are restrained under different driving states, so that the vehicle does not need to simultaneously carry out front wheel steering and differential braking control under a certain working condition. The driving conditions do not consider the acceleration process, and then the driving state of the vehicle is determined according to different conditions and the estimated vehicle posture as shown in table 1.
TABLE 1 vehicle different driving state table
In the above table, r is the yaw rate, δ f Is a corner of the front wheel r t Is a yaw rate threshold value, delta t Is the front wheel steering angle threshold value. K is a stability factor and is used for characterizing steady-state response in an automobile steering stability experiment, and the steady-state response is represented as the following formula:
in the above formula, m represents the mass of the automobile; l f Representing the distance of the front axle to the vehicle's center of mass; l r Representing the distance of the rear axle to the center of mass of the vehicle; k is a radical of 1 Representing front axle cornering stiffness; k is a radical of formula 2 Representing rear axle cornering stiffness; l represents a vehicle wheel base: l = L f +l r 。
From the vehicle running state in table 1, for example, from table 2, control states of a Front-wheel Steering (FS) controller and a Differential Steering (DS) controller are obtained.
TABLE 2 Dual System (FS/DS) controllable State Table
Based on the controller state in the table, the state coefficient eta of the two control strategies of front wheel steering and differential steering is defined under different vehicle driving states s,1 ,η s,2 The two variables are variables (value is 0 or 1) from 0 to 1.
When the front wheels are controlled to steer, the front wheels can generate a certain turning angle by lateral force provided by the ground, and the differential steering not only generates yaw motion but also can act on a steering system to drive the wheels to rotate by a certain angle by controlling the driving torque difference, namely the differential torque, of the coaxial left and right two wheels of the four-wheel independent drive electric automobile. The ground acting force on the tire includes a cornering force (lateral force ) and a longitudinal force, both of which satisfy an adhesion ellipse relationship, and as shown in fig. 7, the cornering force is dependent on a tire cornering angle in addition to the magnitude of the driving force and the braking force, and the cornering force is larger as the cornering angle is larger. Considering that the front wheel steering generates tire lateral deviation force, and the driving torque difference of the differential steering is controlled by tire longitudinal force, and combining limit values of lateral and longitudinal forces of the tire, establishing a tire lateral relative utilization expression as follows:
in the above formula, ω f,2 Indicating the relative utilization in the lateral direction of the tire, F yi Is the cornering force, F, to which the tire i is subjected xi The longitudinal force to which the tire i is subjected, the lateral and longitudinal tire force limit values F yi,lim ，F xi,lim Obtained from the tire adhesion ellipse. The schematic view of the tire adhesion ellipse can be referred to fig. 7.
F yi For tire i (in this embodiment, 4 tires, and therefore i is a positive integer less than or equal to 4), the cornering power is proportional to the cornering angle when the tire is in the linear region, and when the tire is in the nonlinear region, the cornering power is obtained by a calibrated data lookup table, and the expression is:
in the above equation, whether the region belongs to the linear region or the nonlinear region can be determined according to the magnitude of the slip angle. Further, the determination may also be made in conjunction with the magnitude of the slip angle, the state of the road surface, and the state of the tire (tire pressure, etc.).
According to (target) differential moment M z And a tread d, the longitudinal force F of each tire can be obtained xi The following relationship is satisfied:
the expression formula of the coordination rate for controlling the front wheel steering system and the differential steering system is determined by integrating the basic coordination rate, the lateral relative utilization rate of the tire and the vehicle attitude state, and is as follows:
in the above formula, λ c,1 Indicating the control coefficient, λ, of the front-wheel steering controller in coordinated control c,2 And represents a control coefficient of the differential steering controller in the cooperative control. In conjunction with the tire force dynamic distribution region mentioned below, the available coordination rate range is shown in fig. 8. In fig. 8, the oval line indicates the boundary of the tire force range, and the hatched line indicates the variation range of the boundary of the tire force range, that is, the tire force that can be exerted by the vehicle differs depending on the vehicle load and the road adhesion coefficient, so that such a boundary variation exists. The left solid vector line corresponds to the base coordination rate. The right solid line vector line corresponds to the steering coordination rate of a working condition (such as under a normal driving working condition, the dynamic boundary is not exceeded), and the dotted line vector line corresponds to the steering coordination rate of front wheel steering and differential steering under a limit working condition (such as when a large-angle rapid steering is carried out, a large lateral force needs to be improved).
S50: based on the road surface adhesion coefficient, a tire force dynamic distribution area (tire force range) is planned according to the acceleration of the vehicle in the lateral direction, the longitudinal direction and the vertical direction and the load transfer influence caused by the rolling and pitching motions.
In order to perform coordinated control of front wheel steering and differential steering, the maximum lateral force and the maximum longitudinal force provided by a road to a tire need to be accurately obtained, and boundary constraint is provided for a feasible solution of calculating a coordination rate, so that the tire force assignable area (tire force range) is planned in real time by considering a vehicle body motion posture based on a road attachment coefficient.
Vertical load F zi Affecting the tire force range of the vehicle. In the embodiment of the application, the influence of the movement in the three-dimensional directions X, Y and Z on the load transfer is considered, the influence mainly includes the acceleration in the lateral direction, the longitudinal direction and the vertical direction of the vehicle, the roll motion and the pitch motion, fig. 9 is a vehicle body movement stress analysis diagram, and then a relational expression of the load transfer (load variation) caused by the vehicle body movement is established.
Lateral acceleration a y Resulting in a load transfer of the left and right wheels:
the roll motion causes the load transfer of the left and right wheels to be:
in the above formula, I x Is the moment of inertia about the x-axis (longitudinal axis),
is the roll angular acceleration.
Longitudinal acceleration a x Resulting in load transfer for the front and rear axles as:
based on the load transfer caused by the roll motion, the load transfer of the front and rear shafts caused by the pitch motion can be obtained by the following steps:
in the above formula, the first and second carbon atoms are,
is the pitch acceleration.
Taking into account the acceleration a in the vertical direction z The resulting vertical load transfer is:
ΔF″″′ z ＝-ma z (5-5)
in summary, the estimated values of the vertical loads of the four wheels are:
taking the left front wheel as an example, defining the change of the dynamic vertical load caused by the three-dimensional motion of the left front wheel to be delta F zfl Namely:
considering dynamic load transfer, combining with an attachment ellipse, obtaining that the lateral and longitudinal forces borne by the tire meet the following requirements:
in the above equation, m is a vehicle mass, and specifically may be a sprung mass (no-load mass) or an actual mass (non-no-load mass) that can be estimated in real time.
In addition, from the above formula, the boundary of the attachment ellipse changes with the change of the load by Δ F zfl The resulting tire force dynamic assignable areas are shown in fig. 10. In fig. 10, the oval line indicates the boundary of the range of tire force, and the hatched area indicates the variation range of the boundary of tire force. The right vector line corresponds to the resultant force of the braking force and the lateral deviation force, and theta is the included angle of the resultant force and the braking force. The left vector line corresponds to the resultant force after the vertical force is taken into account (one example).
Based on the ellipse in fig. 10, the maximum lateral force and the maximum longitudinal force of the tire can be obtained as follows:
F yfl,lim ＝μF zfl sinθ，F xfl,lim ＝μF zfl cosθ (5-9)
the MPC controller described in S30 allows the vehicle to track the target yaw rate and target centroid slip angle, but cannot provide sufficient tire force to reach the target yaw rate under some limit conditions (conditions of low ground adhesion coefficient, unequal forces on each tire), and thus in combination with the front and rear axle tire force limit values, constrains the yaw rate for improved driving stability:
in the above formula, F yf,lim ,F yr,lim The maximum lateral force of the front shaft and the rear shaft respectively:
in addition, under the working conditions of low friction coefficient or high curvature path, the centroid slip angle can be restrained to ensure that the centroid slip angle is not too large, and the relation between the centroid slip angle and the slip angles of the front tire and the rear tire is as follows:
the accessible restriction tire side declination guarantees that barycenter side declination is at reasonable within range:
α i ≤α i,lim ＝f(F yi,lim ,k i ) (5-13)
in addition, the limit values of the vehicle state signals (yaw velocity and yaw angle) are also fed back to the MPC trajectory tracking controller in S30, and are converted into inequality constraints for rolling optimization solution.
In addition, S40 and S50 may be regarded as one process.
S60: and solving to determine the steering coordination rate (namely solving to obtain the optimal coordination rate) according to a coordination control optimization model constructed based on the steering coordination rate and other constraint conditions.
The design of the coordinated control optimization model is described first.
In order to pursue the minimum front wheel corner and yaw moment and ensure that each tire is subjected to small stress, a comprehensive objective function J is established based on the coordination rate 1 。
The objective function mainly comprises three parts, wherein the first term is the sum of the rotation angle errors in the control domain time, the second term is the sum of the moment errors in the control domain time, and the third term is the sum of the load rates of the tires.
In the above formula, Δ δ f (k + i) represents a front wheel steering angle error value at the time k + i; Δ M z (k + i) represents a yaw moment error value at the time of k + i; r represents a corresponding weight matrix; n is a radical of c Representing the control domain step size.
And (5) combining the yaw angular velocity, the slip angle threshold expression and other constraints established in the S50 to construct constraint conditions of an equation and an inequality, and finally establishing an optimization model with constraints:
in the above formula, epsilon represents a relaxation factor, ensuring that the optimization problem can be solved. Inequality constraint 6-2-3) represents that the stress balance xi of each tire force is considered lim Is a limiting factor; the formula 6-2-4) shows that the performance of the hub motor and the road attachment condition are comprehensively considered to restrain the longitudinal force; the optimization problem can be converted into a Quadratic Programming (QP) problem to be solved, for example, by an active set method or an interior point method. Here, the quadratic programming problem is a constrained nonlinear programming problem, and the objective function f (x) is a quadratic function which is simple in form, i.e., a quadratic functionThe solution can be used in general, but also in specific solutions, to solve non-linear programming.
Using the above optimization model, a steering coordination rate may be determined, which is provided to the MPC trajectory tracking controller in S30 for determining the target front wheel steering angle and the target yaw moment.
By adopting the steering control method of the embodiment, the steering coordination rate, namely the weight of the autonomous steering and the differential steering is determined according to the tire force range, so that the tire force can be fully exerted, the lateral response speed is improved, the turning radius is reduced, and the track tracking precision is improved.
In addition, since the steering coordination rate is determined in consideration of the tire force range, the steering stability and safety of the vehicle can be improved even under the limit running condition (the condition of low road adhesion coefficient, high-speed running, and the like).
In addition, the steering control method provided by the embodiment does not need to additionally increase vehicle-mounted hardware (such as hardware required by the hub motor to drive the electric automobile).
Further, in the present embodiment, the vehicle state quantity threshold value is corrected in consideration of the road surface adhesion condition and/or the vertical load shift, and the steering coordination rate is determined on the basis thereof, so that the vehicle running safety is improved.
In addition, the steering control method provided by the embodiment utilizes the dual systems of the autonomous steering system and the differential system to perform coupling steering control, has a redundancy function, and can improve the vehicle running safety under the coping extreme condition. In addition, for example, when the autonomous steering system fails or malfunctions, the differential steering system can be operated, and safety of vehicle running can be improved.
Fig. 11 is a schematic diagram of a (vehicular) steering system architecture to which the steering control method according to an embodiment of the present application is applied.
As shown in fig. 11, the system architecture mainly includes the following modules:
the signal processing module: the method mainly comprises modules of detection and collection, parameter estimation, identification and the like, and aims to obtain steering control related information. Specifically, the method comprises the steps of acquiring the real-time transverse and longitudinal positions of the vehicle through the cameraX, Y, obtaining course angle through IMU
Angle of roll theta Roll Pitch angle θ Pitch Longitudinal acceleration a x Lateral acceleration a y Vertical acceleration a z The parameter estimation module mainly obtains a mass center slip angle beta and a yaw angular velocity r, and the identification module obtains a road surface adhesion coefficient mu in real time. The signal processing module may be configured to perform the content described in S10 above. The parameter estimation module and the recognition module may also be integrated in the VDC.
The following gives brief examples of the centroid slip angle estimation method, yaw rate estimation method, and road surface adhesion coefficient acquisition method.
Estimating the centroid slip angle: based on a two-degree-of-freedom model of the vehicle, the method can be simplified into a linear estimation model taking the lateral speed as the state, and the lateral speed state value can be estimated by utilizing a linear Kalman filtering method
Finally, according to the relation between the centroid slip angle and the longitudinal and lateral speeds, the calculation can be carried out
Yaw rate estimation: the ESP system receives the angle signal from the steering wheel angle sensor, and in combination with the vehicle speed signal, estimates the yaw rate of the vehicle body due to the vehicle speed and the steering wheel angle.
Road surface adhesion coefficient: the estimation of the road adhesion coefficient is the estimation of the maximum adhesion rate, the adhesion coefficient mu and the tire slip rate s have a mu-s curve relation, the slip rate can be obtained by estimating and calculating signals such as wheel speed, vehicle speed, ground force and the like, and the adhesion coefficient can be calculated by combining with the longitudinal acceleration.
A path planning module: assuming that the vehicle runs at a constant speed in the track tracking process, the path tracking target can specially consider the lateral tracking precision, namely pursuing the lateral error and the heading angle error to be minimum, and a pre-aiming control algorithm is adopted to obtain the target yaw velocity and the centroid yaw angle. The path planning module may be configured to perform the operations described in S20 above.
MPC trajectory tracking module: based on a vehicle dynamic model of front wheel steering and differential steering, a dual-system coordination rate model prediction controller is established, the yaw rate and the centroid yaw angle are controlled to target values to meet the lateral tracking requirement of track tracking, and the controller solves to obtain the target front wheel steering angle
Yaw moment with target
The MPC trajectory tracking module may be used to perform the above-described operations of S30.
Coordination control module (model): and determining the coordination rate range by comprehensively considering the basic coordination rate, the relative utilization rate and the vehicle posture state. In order to seek the minimum front wheel angle and yaw moment, and the tire load rate, a comprehensive objective function J1 is established. And considering the influence of X, Y and Z three-dimensional motions on load transfer, determining a tire force assignable area and providing boundary constraint for a coordination rate range. And finally, constructing a coordination rate optimization model based on the objective function and in combination with other constraint conditions, converting the coordination rate optimization model into a quadratic programming problem, and solving the quadratic programming problem to obtain the optimal coordination rate of the double systems (front wheel steering and differential steering). The coordination control module may be configured to perform the operations described in S40-S60 above.
In addition, in order to reduce the number of controllers and the hard-wire connection and fully exert the strong calculation capability of the domain controller, the path planning module, the MPC trajectory tracking module, the coordination control module, the vehicle posture estimation module and the like are integrated into the VDC for real-time calculation, and finally the control command front wheel corner delta is obtained f,c And the yaw moment M z,c Drive torque command T assigned to four wheels i 。
A motor control strategy module: the front wheel autonomous steering controller receives the steering angle and then completes the steering angle closed-loop control, and the hub motors of the four wheels receive a VDC torque instruction T i And then completing torque closed-loop control. The motor control strategy module may be configured to perform the above-described operation of S70. Additionally, some or all of the functionality of the motor control strategy module may also be integrated into the VDC.
In addition, it is needless to say that the present embodiment also provides a vehicle including the above system architecture, and the steering control apparatus, the computing device, and the like described in the above embodiments.
It is to be understood that in various embodiments of the present application, unless otherwise specified or conflicting, terms and/or descriptions of different embodiments have consistency and may be mutually referenced, and technical features in different embodiments may be combined to form new embodiments according to their inherent logical relationships.
Moreover, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order, unless otherwise indicated. Reference to reference numerals indicating specific contents of methods, such as S10, S20 \8230 \ 8230, etc., do not necessarily indicate that the reference numerals are performed in the order of the numerals, and where permissible, the front and back orders may be interchanged or performed simultaneously. The term "comprising" as used in the specification and claims should not be construed as being limited to the contents listed thereafter; it does not exclude the presence of other elements or steps.
Claims (13)
- A steering control method characterized by comprising:acquiring a tire force range;determining a steering coordination rate from the tire force range, the steering coordination rate indicating a weighting of a steering amount produced by an autonomous steering system of a vehicle and a steering amount produced by a differential steering system of the vehicle;acquiring a yaw angular velocity error;determining a target wheel rotation angle and a target yaw moment according to the yaw angular speed error and the steering coordination rate;transmitting a first control command including a control command for causing the autonomous steering system to generate the target wheel angle and a control command for causing the differential steering system to generate the target yaw moment.
- The steering control method according to claim 1, wherein the acquiring of the tire force range specifically includes:acquiring a road adhesion coefficient and/or load variation of a plurality of wheels of the vehicle;and determining the tire force range according to the road adhesion coefficient and/or the load variation.
- The steering control method according to claim 2, wherein the obtaining of the load variation amounts of the plurality of wheels of the vehicle specifically includes:acquiring one or more of the acceleration, the roll motion state parameter or the pitch motion state parameter of the vehicle in the transverse, longitudinal and vertical directions;determining the load change amount from one or more of the acceleration, the roll-motion state parameter, or the pitch-motion state parameter.
- The steering control method according to any one of claims 1 to 3, wherein the determining a steering coordination rate according to the tire force range specifically includes:acquiring a tire lateral relative utilization rate and a preset basic coordination rate, wherein the tire lateral relative utilization rate indicates the ratio of lateral tire force relative to total tire force, and the basic coordination rate is an initial parameter of the steering coordination rate;and determining the steering coordination rate according to the basic coordination rate, the tire transverse relative utilization rate and the tire force range.
- The steering control method according to any one of claims 1 to 4, characterized in that the steering amount is determined by a steering radius or a yaw angle.
- A vehicle steering control device is characterized by comprising a processing module and a transceiver module,the processing module is used for acquiring a tire force range and a yaw rate error, determining a steering coordination rate according to the tire force range, wherein the steering coordination rate indicates the weight of a steering quantity generated by an autonomous steering system of a vehicle and a steering quantity generated by a differential steering system of the vehicle, and determining a target wheel angle and a target yaw moment according to the yaw rate error and the steering coordination rate;the transceiver module is configured to send a first control instruction, where the first control instruction includes a control instruction for causing the autonomous steering system to generate the target wheel angle and a control instruction for causing the differential steering system to generate the target yaw moment.
- The steering control device according to claim 6, characterized in that the processing module is in particular adapted to,acquiring a road adhesion coefficient and/or load variation of a plurality of wheels of the vehicle;and determining the tire force range according to the road adhesion coefficient and/or the load variation.
- The steering control device according to claim 7, characterized in that the processing module is in particular adapted to,acquiring one or more of acceleration, roll motion state parameters or pitch motion state parameters of the vehicle in the transverse and longitudinal directions;determining the load change amount from one or more of the acceleration, the roll-motion state parameter, or the pitch-motion state parameter.
- The steering control device according to any one of claims 6-8, characterized in that the processing module is specifically configured to,acquiring a tire lateral relative utilization rate and a preset basic coordination rate, wherein the tire lateral relative utilization rate indicates the ratio of lateral tire force relative to total tire force, and the basic coordination rate is an initial parameter of the steering coordination rate;and determining the steering coordination rate according to the basic coordination rate, the tire transverse relative utilization rate and the tire force range.
- The steering control apparatus according to any one of claims 6 to 9, characterized in that the steering amount is determined by a steering radius or a yaw angle.
- A computing device comprising a processor and a memory, the memory storing program instructions that, when executed by the processor, cause the processor to perform the method of any of claims 1-5.
- A computer-readable storage medium storing program instructions, which when executed by a computer, cause the computer to perform the method of any one of claims 1-5.
- A computer program product comprising program instructions which, when executed by a computer, cause the computer to perform the method of any one of claims 1 to 5.
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