CN116674528A - Rear wheel follow-up-based parking system and control method - Google Patents
Rear wheel follow-up-based parking system and control method Download PDFInfo
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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
- B60W30/06—Automatic manoeuvring for parking
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
- B60R16/00—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for
- B60R16/02—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements
- B60R16/023—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements for transmission of signals between vehicle parts or subsystems
- B60R16/0231—Circuits relating to the driving or the functioning of the vehicle
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D15/00—Steering not otherwise provided for
- B62D15/02—Steering position indicators ; Steering position determination; Steering aids
- B62D15/025—Active steering aids, e.g. helping the driver by actively influencing the steering system after environment evaluation
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D5/00—Power-assisted or power-driven steering
- B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
- B62D5/0457—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such
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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
- B60W2520/00—Input parameters relating to overall vehicle dynamics
- B60W2520/28—Wheel speed
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/72—Electric energy management in electromobility
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- Steering Control In Accordance With Driving Conditions (AREA)
Abstract
The invention discloses a parking system control method based on rear wheel follow-up, which is applied to a parking system based on rear wheel follow-up and comprises the following steps: after the automatic parking function is started, a parking space target coordinate system is established by taking the automatic parking space as an origin, the target parking space position is obtained, and 4 corner points of the target parking space are selected as positioning targets; decomposing four-wheel parameters of the self-vehicle to obtain the acceleration of the self-vehicle in the y-axis direction in a parking space target coordinate system and the second derivative of the deflection angle of the vehicle; respectively calculating to obtain deflection angles of the front wheel and the rear wheel; positioning the center of mass of the self-vehicle; and controlling the track of the own vehicle, and calculating to obtain a parking path. The invention utilizes the original automatic parking system and the rear wheel steering system, realizes the full utilization of the original vehicle executing and controlling system through the design based on an algorithm and a control scheme, finally realizes the coordination control of the vehicle under different rear wheel steering modes, and completes the coordination intercommunication of the two systems.
Description
Technical Field
The invention belongs to the field of automatic parking of vehicles, and particularly relates to a parking system based on rear wheel follow-up and a control method.
Background
In the prior art, a single steering unit is used for controlling the parking system, for example, most vehicles only can steer and operate front wheels, so that the vehicle is ensured to have unique corresponding control tracks when responding to a parking system request, and the accurate performance of parking action execution can be ensured.
The technical scheme is widely applicable to the vehicle types with non-follow-up steering of the rear wheels which are widely used at present, and when the EPS controller receives a parking system angle request, the EPS controller controls the front wheels of the vehicle to a preset position. There are significant limitations on vehicles equipped with rear-wheel-following parking systems, which are mainly reflected in:
1. the parking system with the trailing wheels has different vehicle motion tracks due to different steering angles of the trailing wheels and the leading wheels, so that the vehicle motion tracks are different under the same angle request of the parking system;
2. the rear wheel follow-up parking system has different modes of same-direction follow-up and reverse follow-up when the control mode of the rear wheel follow-up parking system changes, so that the motion trail of the vehicle is different under the same angle request of the parking system;
3. the rear wheels of the rear wheel follow-up parking system have different steering limits, so that the vehicle motion trail of the parking system is different under the same angle request;
in view of the above, it is common practice in parking systems to shut down the rear-wheel-following parking system or to always bring the rear-wheel steering angle and the front-wheel steering angle into a fixed proportional relationship while the parking system is in operation. The control problem of the parking system can be solved, but the advantages of the rear wheel steering system are reduced, so that the parking capacity of the automatic parking system is lower than the driving parking capacity of a driver under certain special working conditions, and the meaning of the parking system is lost.
Disclosure of Invention
The invention aims to provide a rear-wheel follow-up-based parking system and a control method, which utilize an original vehicle automatic parking system and a rear-wheel steering system, fully utilize the original vehicle execution and control system through algorithm-based and control scheme design, finally realize the coordination control of vehicles in different rear-wheel steering modes and complete the coordination intercommunication of the two systems.
In order to solve the technical problems, the technical scheme of the invention is as follows: the utility model provides a parking system control method based on rear wheel follow-up, be applied to the parking system based on rear wheel follow-up, this system includes four-wheel steering system, the central parking controller who has carried parking system control method based on rear wheel follow-up, whole car CAN bus, EPS controller, ESC\TCU controller and wheel speed sensor that are connected with each other, wherein, four-wheel steering system includes the electronic power assisted steering system that is used for controlling front wheel steering, the electronic power assisted steering system that is used for controlling rear wheel steering and the ECU that is used for driving deflection in order to adapt to front wheel steering through calculation control rear wheel steering mechanism, this method includes the following steps:
after the automatic parking function is started, a parking space target coordinate system is established by taking the automatic parking space as an origin, the target parking space position is obtained, and 4 corner points of the target parking space are selected as positioning targets;
decomposing four-wheel parameters of the self-vehicle to obtain the acceleration of the self-vehicle in the y-axis direction in a parking space target coordinate system and the second derivative of the deflection angle of the vehicle; wherein, the y axis is vertical to the running direction of the bicycle in the horizontal direction;
respectively calculating to obtain deflection angles of the front wheel and the rear wheel;
positioning the center of mass of the self-vehicle;
and controlling the track of the own vehicle, and calculating to obtain a parking path.
The four-wheel parameters of the vehicle are decomposed in the following modes:
wherein m isMass of bicycle, I Z For the moment of inertia of the vehicle, l f For the distance from the front axle to the centre of mass, l r A is the distance from the rear axle to the mass center y For the acceleration of the bicycle in the y-axis direction, F yf For the front wheel to bear force in the y-axis direction, F yr Is stressed by the rear wheel in the y-axis direction.
The steering angle of the front wheel and the rear wheel is calculated by the following steps:
the method is obtained according to the relation between the transverse stress and deflection angle of the tire:
F yf ＝2C αf (θ Vf -δ f )cos(δ f )
F yr ＝2C αr (δ r -θ Vr )cos(δ r )
wherein ,Cαf For front wheel cornering stiffness, delta f Is the steering angle of the front wheel, theta Vf C is the deflection angle of the front wheel αr For the cornering stiffness of the rear wheels, δr is the steering angle of the rear wheels, θ Vr Is the deflection angle of the rear wheel;
decomposing acceleration in the y-axis direction to obtain:
wherein ,for the acceleration of the vehicle displacement in the y-axis direction, i.e. the second derivative of y, +.>Centripetal acceleration of the bicycle;
wherein tan (θ) Vf ) Is the ratio of the lateral speed to the longitudinal speed of the front wheel of the vehicle, tan (θ Vr ) Is the ratio of the transverse speed to the longitudinal speed of the rear wheel of the bicycle;
the yaw angle of the front and rear wheels is expressed as:
the specific mode for positioning the mass center position of the vehicle is as follows:
according to the decomposition mode of four-wheel parameters of the bicycle and the steering angle calculation mode of the front wheel and the rear wheel, the following formula is obtained:
during the running process of the vehicle, the following steps are included:
s 1 ＝2C αf cos(δ f )
s 2 ＝2C αr cos(δ r )
the positioning data of the center of mass of the bicycle is expressed as:
the positioning data at the center of the rear axle is expressed as:
namely:
wherein ,Xt For the target position coordinate of the self-vehicle in the x-axis direction, Y t For the target position coordinates of the vehicle in the Y-axis direction,the real-time speed of the vehicle in the y direction; θ t Is the slip angle of the rear wheel.
The calculation mode of the track coordinates in track control of the vehicle is as follows:
wherein ,the vehicle state information of the own vehicle at the current moment, wherein y is the distance between the own vehicle at the current moment and the target position in the y direction,/for the own vehicle at the current moment>Is the angular change rate of the own vehicle.
The parking system based on rear wheel follow-up comprises a four-wheel steering system, a central parking controller, a whole vehicle CAN bus, an EPS controller, an ESC/TCU controller and a wheel speed sensor, wherein the four-wheel steering system, the central parking controller, the whole vehicle CAN bus, the EPS controller, the ESC/TCU controller and the wheel speed sensor are mutually and electrically connected; wherein,
the four-wheel steering system comprises an electric power steering system for controlling front wheel steering, an electric power steering system for controlling rear wheel steering and an ECU for driving deflection by calculating and controlling a rear wheel steering mechanism to adapt to front wheel steering; the whole vehicle CAN bus is used for providing the collected necessary vehicle signals for the central controller to process and return the control instructions processed by the central controller;
the central controller is used for establishing a parking space target coordinate system by taking the vehicle space as an origin after the vehicle starts an automatic parking function, acquiring a target parking space position, and selecting 4 corner points of the target parking space as positioning targets; decomposing four-wheel parameters of the self-vehicle to obtain the acceleration of the self-vehicle in the y-axis direction in a parking space target coordinate system and the second derivative of the deflection angle of the vehicle; respectively calculating to obtain deflection angles of the front wheel and the rear wheel; positioning the center of mass of the self-vehicle; performing track control on the own vehicle, and calculating to obtain a parking path;
an EPS controller for controlling steering angles of front and rear wheels of the bicycle;
an ESC/TCU controller for controlling other operations of the automatic parking system except for controlling steering angles of front and rear wheels of the vehicle;
and the wheel speed sensor is used for providing wheel speed information.
The four-wheel parameters of the vehicle are decomposed in the following modes:
wherein m is the mass of the vehicle, I Z For the moment of inertia of the vehicle, l f For the distance from the front axle to the centre of mass, l r A is the distance from the rear axle to the mass center y For the acceleration of the bicycle in the y-axis direction, F yf For the front wheel to bear force in the y-axis direction, F yr Is stressed by the rear wheel in the y-axis direction.
The steering angle of the front wheel and the rear wheel is calculated by the following steps:
the method is obtained according to the relation between the transverse stress and deflection angle of the tire:
F yf ＝2C αf (θ Vf -δ f )cos(δ f )
F yr ＝2C αr (δ r -θ Vr )cos(δ r )
wherein ,Cαf For front wheel cornering stiffness, delta f Is the steering angle of the front wheel, theta Vf C is the deflection angle of the front wheel αr For the cornering stiffness of the rear wheels, δr is the steering angle of the rear wheels, θ Vr Is the deflection angle of the rear wheel; decomposing acceleration in the y-axis direction to obtain:
wherein ,for the acceleration of the vehicle displacement in the y-axis direction, i.e. the second derivative of y, +.>Centripetal acceleration of the bicycle;
wherein tan (θ) Vf ) Is the ratio of the lateral speed to the longitudinal speed of the front wheel of the vehicle, tan (θ Vr ) Is the ratio of the transverse speed to the longitudinal speed of the rear wheel of the bicycle;
the yaw angle of the front and rear wheels is expressed as:
the specific mode for positioning the mass center position of the vehicle is as follows:
according to the decomposition mode of four-wheel parameters of the bicycle and the steering angle calculation mode of the front wheel and the rear wheel, the following formula is obtained:
during the running process of the vehicle, the following steps are included:
s 1 ＝2C αf cos(δ f )
s 2 ＝2C αr cos(δ r )
the positioning data of the center of mass of the bicycle is expressed as:
the positioning data at the center of the rear axle is expressed as:
namely:
wherein ,Xt For the target position coordinate of the self-vehicle in the x-axis direction, Y t For the target position coordinates of the vehicle in the Y-axis direction,the real-time speed of the vehicle in the y direction; θ t Is the slip angle of the rear wheel.
The calculation mode of the track coordinates in track control of the vehicle is as follows:
wherein ,the vehicle state information of the own vehicle at the current moment, wherein y is the distance between the own vehicle at the current moment and the target position in the y direction,/for the own vehicle at the current moment>Is the angular change rate of the own vehicle.
Compared with the prior art, the invention has the beneficial effects that:
safety benefit: the invention can ensure the continuous use of the rear wheel steering and automatic parking functions under various environmental conditions, ensure the use scene and further ensure the driving safety.
Economic benefit: under the condition that other equipment is not newly added, the scheme design is completed based on the rear wheel follow-up parking system control method, and the cost is saved.
Enterprise benefit: the invention is simple and practical, is suitable for all vehicle types, can interact with rear wheel steering systems of various types, and operates in a modularized manner.
Drawings
FIG. 1 is a schematic flow chart of an embodiment of the present invention;
FIG. 2 is a system architecture diagram in an embodiment of the invention;
fig. 3 is a flowchart of an algorithm in an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
The invention provides a control method of a parking system based on rear wheel follow-up, which utilizes an original automatic parking system and a rear wheel steering system, and realizes full utilization of an original vehicle execution and control system through design based on an algorithm and a control scheme, and finally realizes coordination control on vehicles in different rear wheel steering modes, thereby completing coordination and intercommunication of the two systems.
In order to achieve the purpose, a parking system control method based on rear wheel follow-up is provided, and a low-cost (with wide usability) system solution is provided.
Example 1: rear wheel follow-up-based parking system
As shown in fig. 2, the scheme is composed of four-wheel steering system supporting the basic structure designed by the invention, a central parking controller (with a parking system control method based on rear wheel follow-up), a CAN bus, an EPS controller, other controllers such as ESC/TCU, a wheel speed sensor, and the like.
The four-wheel steering system is a 4WS system adopting electronic control and electronic assistance, the front wheel can adopt a traditional/electric power steering system, the rear wheel adopts an electric steering system, no mechanical connecting device, hydraulic pipeline and other parts are arranged between the two steering devices, and the structures are mutually independent. The steering of the front and rear wheels is directly controlled by adopting electronic control. During steering, signals of a front wheel corner, a vehicle speed, a yaw rate sensor and the like are sent to an ECU for analysis and calculation, the ECU determines a rear wheel corner and outputs a driving signal to a stepping motor, and the rear wheel steering mechanism drives deflection to adapt to front wheel steering, so that four-wheel steering is realized.
The whole vehicle CAN bus is used for providing the collected necessary vehicle signals for the central controller to process and return the control instructions processed by the central controller;
the central controller (with an optical road spectrum detection method and technology based on an air suspension) is used for 1) storing and calculating the functional algorithm of the invention; 2) Storing an angle control meter module; 3) Algorithm program storage of other normal functions;
the EPS controller is used for uniformly executing the angle request in the invention;
other controllers such as ESC/TCU are used for parking system to need other actions;
the wheel speed sensor provides wheel speed information and further corrects angle information.
Example 2: also provided is a parking control method based on rear wheel follow-up
As shown in fig. 1 and 3, the steps of the present solution are designed as follows:
1) Establishment of parking space target coordinate system
At the time t=0 when the vehicle starts the automatic parking function and confirms the available (most of parking space searching) stage, a coordinate system of the origin of coordinates is established, and 4 corner points of the target parking space are the final control targets.
2) Decomposing four-wheel parameters of vehicle
ma y ＝F yf +F yr The method comprises the steps of carrying out a first treatment on the surface of the Is Newton's mechanical equation;is a moment balance equation;
m is the mass of the automobile, I Z Is the rotational inertia of the vehicle, I f Distance from front axle to mass center of vehicle, I r The distance from the rear axle of the vehicle to the center of mass is known in vehicle design.
3) Calculating steering angle of two wheels
The relation between the transverse stress and the slip angle of the tire is obtained:
F yf ＝2C αf (θ Vf -δ f )cos(δ f )
F yr ＝2C αr (δ r -θ Vr )cos(δ r )
C αf for front wheel cornering stiffness, delta f Is the rotation angle of the front wheel, theta Vf Is the side deflection angle of the front wheel
C αr For the cornering stiffness of the rear wheel, δr is the rear wheel steering angle, θ Vr Is the slip angle of the rear wheel
The lateral acceleration can be decomposed into acceleration and centripetal acceleration generated by lateral displacement, and the acceleration in the y-axis direction is decomposed to obtain:
acceleration for displacement in the y-axis direction, +.>The centripetal acceleration is indicated as such,
tan(θ Vf )，tan(θ Vr ) Is the ratio of the lateral speed and the longitudinal speed of the vehicle.
The two-wheel steering angle is as follows:
4) Vehicle center of mass location processing
The kinetic equation translates into:
during the running process of the vehicle:
wherein in the above formula:
s 1 ＝2C αf cos(δ f )
s 2 ＝2C αr cos(δ r )
the positioning data of the mass center of the vehicle are as follows:
the positioning data at the center of the rear axle are:
namely:
5) Track control of vehicles with reference to real-time parameters of the vehicles
The scheme is as follows:
wherein ,for the current momentVehicle state information of a vehicle, wherein y is the distance from the vehicle to the target position in the y direction at the current moment,/v>Is the angular change rate of the own vehicle.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (10)
1. The utility model provides a parking system control method based on rear wheel follow-up, characterized in that is applied to the parking system based on rear wheel follow-up, this system includes four-wheel steering system, the central parking controller who carries on the parking system control method based on rear wheel follow-up, whole car CAN bus, EPS controller, ESC\TCU controller and wheel speed sensor that are connected each other, wherein, four-wheel steering system includes the electric power steering system that is used for controlling front wheel steering, the electric power steering system that is used for controlling rear wheel steering and the ECU that is used for driving deflection in order to adapt to front wheel steering through calculating control rear wheel steering mechanism, this method includes the following steps:
after the automatic parking function is started, a parking space target coordinate system is established by taking the automatic parking space as an origin, the target parking space position is obtained, and 4 corner points of the target parking space are selected as positioning targets;
decomposing four-wheel parameters of the self-vehicle to obtain the acceleration of the self-vehicle in the y-axis direction in a parking space target coordinate system and the second derivative of the deflection angle of the vehicle; wherein, the y axis is vertical to the running direction of the bicycle in the horizontal direction;
respectively calculating to obtain deflection angles of the front wheel and the rear wheel;
positioning the center of mass of the self-vehicle;
and controlling the track of the own vehicle, and calculating to obtain a parking path.
2. The rear wheel follow-up based parking system control method according to claim 1, wherein the four-wheel parameters of the own vehicle are decomposed in the following manner:
wherein m is the mass of the vehicle, I Z For the moment of inertia of the vehicle, l f For the distance from the front axle to the centre of mass, l r A is the distance from the rear axle to the mass center y For the acceleration of the bicycle in the y-axis direction, F yf For the front wheel to bear force in the y-axis direction, F yr Is stressed by the rear wheel in the y-axis direction.
3. The rear wheel follow-up-based parking system control method according to claim 2, wherein the steering angle of the front wheels and the rear wheels is calculated by:
the method is obtained according to the relation between the transverse stress and deflection angle of the tire:
F yf ＝2C αf (θ Vf -δ f )cos(δ f )
F yr ＝2C αr (δ r -θ Vr )cos(δ r )
wherein ,Cαf For front wheel cornering stiffness, delta f Is the steering angle of the front wheel, theta Vf C is the deflection angle of the front wheel αr For the cornering stiffness of the rear wheels, δr is the steering angle of the rear wheels, θ Vr Is the deflection angle of the rear wheel;
decomposing acceleration in the y-axis direction to obtain:
wherein ,for the acceleration of the vehicle displacement in the y-axis direction, i.e. the second derivative of y, +.>Centripetal acceleration of the bicycle;
wherein tan (θ) Vf ) Is the ratio of the lateral speed to the longitudinal speed of the front wheel of the vehicle, tan (θ Vr ) Is the ratio of the transverse speed to the longitudinal speed of the rear wheel of the bicycle;
the yaw angle of the front and rear wheels is expressed as:
4. a rear wheel follow-up-based parking system control method according to claim 3, wherein the specific manner of locating the center of mass position of the vehicle is:
according to the decomposition mode of four-wheel parameters of the bicycle and the steering angle calculation mode of the front wheel and the rear wheel, the following formula is obtained:
during the running process of the vehicle, the following steps are included:
s 1 ＝2C αf cos(δ f )
s 2 ＝2C αr cos(δ r )
the positioning data of the center of mass of the bicycle is expressed as:
the positioning data at the center of the rear axle is expressed as:
namely:
wherein ,Xt For the target position coordinate of the self-vehicle in the x-axis direction, Y t For the target position coordinates of the vehicle in the Y-axis direction,the real-time speed of the vehicle in the y direction; θ t Is the slip angle of the rear wheel.
5. The rear wheel follow-up based parking system control method according to claim 4, wherein the track coordinates in the track control of the own vehicle are calculated by:
wherein ,the vehicle state information of the own vehicle at the current moment, wherein y is the distance between the own vehicle at the current moment and the target position in the y direction,/for the own vehicle at the current moment>Is the angular change rate of the own vehicle.
6. A parking system using the rear-wheel-following-based parking system control method according to claim 1, characterized by comprising a four-wheel steering system, a central parking controller, a whole vehicle CAN bus, an EPS controller, an esc\tcu controller and a wheel speed sensor, which are electrically connected with each other, and are equipped with the rear-wheel-following-based parking system control method; wherein,
the four-wheel steering system comprises an electric power steering system for controlling front wheel steering, an electric power steering system for controlling rear wheel steering and an ECU for driving deflection by calculating and controlling a rear wheel steering mechanism to adapt to front wheel steering; the whole vehicle CAN bus is used for providing the collected necessary vehicle signals for the central controller to process and return the control instructions processed by the central controller;
the central controller is used for establishing a parking space target coordinate system by taking the vehicle space as an origin after the vehicle starts an automatic parking function, acquiring a target parking space position, and selecting 4 corner points of the target parking space as positioning targets; decomposing four-wheel parameters of the self-vehicle to obtain the acceleration of the self-vehicle in the y-axis direction in a parking space target coordinate system and the second derivative of the deflection angle of the vehicle; respectively calculating to obtain deflection angles of the front wheel and the rear wheel; positioning the center of mass of the self-vehicle; performing track control on the own vehicle, and calculating to obtain a parking path;
an EPS controller for controlling steering angles of front and rear wheels of the bicycle;
an ESC/TCU controller for controlling other operations of the automatic parking system except for controlling steering angles of front and rear wheels of the vehicle;
and the wheel speed sensor is used for providing wheel speed information.
7. The parking system according to claim 6, wherein the four-wheel parameters of the own vehicle are decomposed in the following manner:
wherein m is the mass of the vehicle, I Z For the moment of inertia of the vehicle, l f For the distance from the front axle to the centre of mass, l r A is the distance from the rear axle to the mass center y For the acceleration of the bicycle in the y-axis direction, F yf For the front wheel to bear force in the y-axis direction, F yr Is stressed by the rear wheel in the y-axis direction.
8. The parking system according to claim 7, wherein the steering angles of the front wheels and the rear wheels are calculated by:
the method is obtained according to the relation between the transverse stress and deflection angle of the tire:
F yf ＝2C αf (θ Vf -δ f )cos(δ f )
F yr ＝2C αr (δ r -θ Vr )cos(δ r )
wherein ,Cαf For front wheel cornering stiffness, delta f Is the steering angle of the front wheel, theta Vf C is the deflection angle of the front wheel αr For the cornering stiffness of the rear wheels, δr is the steering angle of the rear wheels, θ Vr Is the deflection angle of the rear wheel; decomposing acceleration in the y-axis direction to obtain:
wherein ,for the acceleration of the vehicle displacement in the y-axis direction, i.e. the second derivative of y, +.>Centripetal acceleration of the bicycle;
wherein tan (θ) Vf ) Is the ratio of the lateral speed to the longitudinal speed of the front wheel of the vehicle, tan (θ Vr ) Is the ratio of the transverse speed to the longitudinal speed of the rear wheel of the bicycle;
the yaw angle of the front and rear wheels is expressed as:
9. the parking system of claim 8, wherein the location of the center of mass location of the host vehicle is in the following manner:
according to the decomposition mode of four-wheel parameters of the bicycle and the steering angle calculation mode of the front wheel and the rear wheel, the following formula is obtained:
during the running process of the vehicle, the following steps are included:
s 1 ＝2C αf cos(δ f )
s 2 ＝2C αr cos(δ r )
the positioning data of the center of mass of the bicycle is expressed as:
the positioning data at the center of the rear axle is expressed as:
namely:
wherein ,Xt For the target position coordinate of the self-vehicle in the x-axis direction, Y t For the target position coordinates of the vehicle in the Y-axis direction,the real-time speed of the vehicle in the y direction; θ t Is the slip angle of the rear wheel.
10. The parking system according to claim 9, wherein the track coordinates in track control of the host vehicle are calculated by:
wherein ,the vehicle state information of the own vehicle at the current moment, wherein y is the distance between the own vehicle at the current moment and the target position in the y direction,/for the own vehicle at the current moment>Is the angular change rate of the own vehicle.
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