CN113291323B - Automatic driving path tracking control method and system for rhombic vehicle and vehicle - Google Patents

Automatic driving path tracking control method and system for rhombic vehicle and vehicle Download PDF

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CN113291323B
CN113291323B CN202110679202.3A CN202110679202A CN113291323B CN 113291323 B CN113291323 B CN 113291323B CN 202110679202 A CN202110679202 A CN 202110679202A CN 113291323 B CN113291323 B CN 113291323B
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vehicle
rhombic
control
path tracking
distance
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CN113291323A (en
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刘东寰
杨泽宇
王锱雷
高宝杰
张敏
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CRRC Qingdao Sifang Co Ltd
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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
    • B60W60/00—Drive control systems specially adapted for autonomous road vehicles
    • B60W60/001—Planning or execution of driving tasks
    • 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
    • B60W10/00—Conjoint control of vehicle sub-units of different type or different function
    • B60W10/20—Conjoint control of vehicle sub-units of different type or different function including control of steering systems
    • 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
    • B60W2520/10—Longitudinal speed
    • 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
    • B60W2520/12—Lateral speed
    • 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
    • B60W2530/00—Input parameters relating to vehicle conditions or values, not covered by groups B60W2510/00 or B60W2520/00
    • B60W2530/10—Weight
    • 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
    • B60W2540/00—Input parameters relating to occupants
    • B60W2540/18—Steering angle
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D61/00—Motor vehicles or trailers, characterised by the arrangement or number of wheels, not otherwise provided for, e.g. four wheels in diamond pattern
    • B62D61/02—Motor vehicles or trailers, characterised by the arrangement or number of wheels, not otherwise provided for, e.g. four wheels in diamond pattern with two road wheels in tandem on the longitudinal centre line of the vehicle
    • B62D61/04—Motor vehicles or trailers, characterised by the arrangement or number of wheels, not otherwise provided for, e.g. four wheels in diamond pattern with two road wheels in tandem on the longitudinal centre line of the vehicle with two other wheels which are coaxial

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  • Engineering & Computer Science (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Automation & Control Theory (AREA)
  • Human Computer Interaction (AREA)
  • Steering Control In Accordance With Driving Conditions (AREA)

Abstract

The invention provides a method and a system for tracking and controlling an automatic driving path of a rhombic vehicle and the vehicle, wherein geometric parameters and dynamic parameters of the rhombic vehicle are determined, and control parameters are set; acquiring the longitudinal speed of the vehicle, judging the relation between the longitudinal speed of the vehicle and a set speed control threshold value, if the longitudinal speed of the vehicle is less than the speed control threshold value, performing path tracking control by using a pre-aiming control method based on geometry, and otherwise, performing path tracking control by using a pre-aiming control method based on dynamics; the method aims at the specific steering geometric relation and the transverse dynamic characteristic of the rhombic vehicle, utilizes different control strategies under the working conditions of high speed and low speed, is really suitable for the rhombic vehicle, and simultaneously ensures that the rhombic vehicle can have better motion control performance under all the working conditions.

Description

Automatic driving path tracking control method and system for rhombic vehicle and vehicle
Technical Field
The disclosure belongs to the technical field of automatic vehicle driving, and particularly relates to a rhombic automatic vehicle driving path tracking control method and system and a vehicle.
Background
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
The rhombic vehicle is a vehicle with a three-shaft four-wheel novel chassis framework. The front and rear shafts have independent steering functions, and the middle shaft provides driving force. The rhombic vehicle has excellent side impact and front impact safety and excellent steering performance. Meanwhile, the rhombic chassis configuration enables the overall design to have a streamlined characteristic, and can effectively reduce the running wind resistance and save the oil consumption. The structure, dynamic response, etc. of a diamond-shaped vehicle have been widely studied, but the automatic driving technique thereof has not been regarded as important.
According to the inventor, the path tracking control technical scheme in the current automatic vehicle driving control is not suitable for the diamond-shaped vehicle, the characteristics of the geometric structure and different dynamic performances are not considered, the tracking performance of the diamond-shaped vehicle in a full speed interval cannot be realized, the motion control precision of the vehicle under the low-speed working condition of the diamond-shaped vehicle is easy to cause insufficient, and the risk of sideslip and the like are caused due to the untimely vehicle control under the high-speed working condition.
Disclosure of Invention
The invention provides a method, a system and a vehicle for tracking and controlling an automatic driving path of a rhombic vehicle, aiming at the specific steering geometric relation and the transverse dynamic characteristic of the rhombic vehicle, different control strategies are utilized under high-speed and low-speed working conditions, the method and the system are really suitable for the rhombic vehicle, and simultaneously the rhombic vehicle can have better motion control performance under all working conditions.
According to some embodiments, the following technical scheme is adopted in the disclosure:
the first purpose of the present disclosure is to provide a method for tracking and controlling an automatic driving path of a diamond-shaped vehicle, comprising the following steps:
determining geometric parameters and dynamic parameters of the rhombic vehicle, and setting control parameters;
acquiring the longitudinal speed of the vehicle, judging the relation between the longitudinal speed of the vehicle and a set speed control threshold value, if the longitudinal speed of the vehicle is less than the speed control threshold value, carrying out path tracking control by using a pre-aiming control method based on geometry, otherwise, carrying out path tracking control by using a pre-aiming control method based on dynamics.
As an alternative embodiment, the geometrical parameters of the diamond-shaped vehicle include, but are not limited to, the distance l of the rear axle of the vehicle from the center of mass of the vehiclerDistance l from center axis of vehicle to center of mass of vehiclemDistance l between front axle of vehicle and mass center of vehiclefDistance l between rear axle and middle axle of vehiclermDistance l from the front axle of the vehicle to the middle axle of the vehiclefm。
As an alternative embodiment, the dynamic parameters of the rhombic vehicle comprise but are not limited to the mass M of the whole vehicle, and the moment of inertia I of the vehicle around the gravity center in the direction vertical to the horizontal planeZRear wheel side yaw stiffness krMiddle wheel cornering stiffness kmAnd front wheel side cornering stiffness kf。
As an alternative embodiment, the control parameter comprises a mode switching threshold vMPre-aiming distance DLA parameter matrix R and a parameter matrix Q.
As an alternative embodiment, the specific process of performing path tracking control by using the pre-aiming control method based on geometry includes:
acquiring an included angle between a connecting line from the center of a central shaft of the vehicle to a pre-aiming point and an x-axis of the vehicle, and calculating an expected turning radius of the vehicle according to the included angle;
and calculating steering angle control quantities of front and rear wheels of the vehicle according to the expected turning radius, the distance between the rear axle of the vehicle and the middle axle of the vehicle and the distance between the front axle of the vehicle and the middle axle of the vehicle and the Ackerman steering geometric relation of the rhombic vehicle so as to control the vehicle.
By way of further limitation, the desired turning radius R is calculated by:
Figure BDA0003121892570000031
wherein D isLFor the pre-aiming distance,/mThe distance between the center axis of the vehicle and the center of mass of the vehicle is alpha, the included angle between the connecting line from the center of the center axis of the vehicle to the prealignment point and the x axis of the vehicle is alpha, when the prealignment point is in the fourth quadrant of the vehicle coordinate system, the alpha sign is negative, otherwise, the alpha sign is positive.
As a further limitation, the steering angle control amount δ of the front wheels of the vehiclefAnd a steering angle control amount δ of a rear wheel of the vehiclerThe calculation method comprises the following steps:
Figure BDA0003121892570000032
Figure BDA0003121892570000033
wherein R is the periodRadius of turn, lrmIs the distance of the rear axle of the vehicle from the center axle, lfmSign (alpha) is a sign function about alpha, and is the distance between a front axle of the vehicle and a middle axle of the vehicle, and when the alpha is larger than or equal to 0, the sign (alpha) is 1; alpha is alpha<At 0, sign (α) is-1.
As an alternative embodiment, the specific process of performing the path tracking control by using the dynamics-based preview control method includes:
calculating an error state vector according to the yaw velocity, the lateral velocity, the vehicle yaw angle error and the vehicle lateral offset of the vehicle;
calculating a vehicle transverse dynamics parameter according to the transverse dynamics model of the rhombic vehicle;
calculating error dynamic model parameters according to the transverse dynamic parameters of the vehicle and the diamond vehicle path tracking error dynamic model to obtain a diamond vehicle path tracking error dynamic model;
and calculating control parameters according to a preset parameter matrix, a preset parameter matrix and error dynamics model parameters, and calculating control vectors according to the control parameters, the preset parameter matrix and the error dynamics model parameters.
By way of further limitation, the method of calculating the error state vector is: yaw rate based on vehicle state information
Figure BDA0003121892570000041
Transverse velocity vyVehicle yaw angle error
Figure BDA0003121892570000042
Vehicle lateral offset eyCalculating error state vectors
Figure BDA0003121892570000043
Wherein the content of the first and second substances,
Figure BDA0003121892570000044
a first derivative is laterally offset for the vehicle,
Figure BDA0003121892570000045
for the first derivative of the vehicle yaw angle error, the calculation formulas are respectively as follows:
Figure BDA0003121892570000046
Figure BDA0003121892570000047
wherein v isxAs longitudinal speed of the vehicle, DLFor a pre-aiming distance, cRCurvature information at the pre-aimed point on the desired path.
As a further limitation, the specific process of calculating the lateral dynamics parameter of the vehicle includes:
the diamond-shaped vehicle transverse dynamics calculation formula is as follows:
Figure BDA0003121892570000048
Figure BDA0003121892570000049
wherein the transverse dynamic parameter a of the vehicle1～a8The calculation formulas of (A) and (B) are respectively as follows:
Figure BDA0003121892570000051
Figure BDA0003121892570000052
wherein lrIs the distance of the rear axle of the vehicle from the center of mass of the vehicle, lmIs the distance of the vehicle center axis from the vehicle center of mass,/fIs the distance from the front axle of the vehicle to the center of mass of the vehicle, M is the total vehicle mass, IZFor the moment of inertia of the vehicle about the centre of gravity perpendicular to the horizontal, krThe rear wheel side is deviated and rigidDegree, kmFor cornering stiffness of the middle wheel, kfIs the front wheel cornering stiffness.
As a further limitation, the diamond vehicle path tracking error dynamic model is:
Figure BDA0003121892570000053
wherein U is [ δ ═ df，δr]For the control vector, A, B is a model parameter, C is a road curvature related parameter, and A, B, C is calculated as follows:
Figure BDA0003121892570000054
Figure BDA0003121892570000055
wherein, cRCurvature at the intended point on the desired path, DLFor the pre-aiming distance, vxIs the vehicle longitudinal speed.
As a further limitation, the specific process of calculating the control parameter is as follows: solving the Riccati equation: a. theTP+PA-2PBR-1BTP + Q is 0, where P is the control variable, Q is the parameter matrix characterizing the weights of the error states, and A, B is the error dynamics model parameter.
By way of further limitation, the control vector U is: u ═ R-1BTAnd PX, wherein R is a parameter matrix representing the weight of the control cost, B is an error dynamic model parameter, P is a control parameter, and X is an error state vector.
It is a second object of the present disclosure to provide a diamond-shaped vehicle automatic driving path tracking control system, comprising:
the parameter determination module is configured to determine geometric parameters and dynamic parameters of the rhombic vehicle and set control parameters;
a speed acquisition module configured to acquire a vehicle longitudinal speed;
and the sub-working condition control module is configured to judge the relation between the longitudinal speed of the vehicle and a set speed control threshold, if the longitudinal speed of the vehicle is less than the speed control threshold, the path tracking control is carried out by using a pre-aiming control method based on geometry, and if not, the path tracking control is carried out by using a pre-aiming control method based on dynamics.
A third object of the present disclosure is to provide a diamond-shaped vehicle, which adopts the method provided by the first object or comprises the system provided by the second object.
As an alternative embodiment, the diamond-shaped vehicle further comprises:
the positioning module is used for acquiring rhombic vehicle position information;
the sensing module is used for acquiring the motion state information of the rhombic vehicle;
and the planning module is used for generating the expected path.
According to the positioning module and the sensing module, the speed v of the vehicle can be acquiredxYaw rate
Figure BDA0003121892570000061
Transverse velocity vyVehicle lateral offset eyVehicle yaw angle error
Figure BDA0003121892570000062
And the state information of the included angle alpha between the connecting line from the center of the middle axle of the vehicle to the pre-aiming point and the x-axis.
It is a fourth object of the present disclosure to provide a computer readable storage medium for storing computer instructions which, when executed by a processor, perform the steps of the above method.
A fifth object of the present disclosure is to provide a terminal device, comprising a memory and a processor, and computer instructions stored on the memory and run on the processor, wherein the computer instructions, when executed by the processor, perform the steps of the above method.
Compared with the prior art, the beneficial effect of this disclosure is:
the method considers the unique steering geometric relation and the transverse dynamic response model of the diamond-shaped vehicle, can be really suitable for the diamond-shaped vehicle in the path tracking automatic control, can exert the excellent steering performance of the diamond-shaped vehicle, and realizes the following of the expected path with larger curvature.
According to the characteristics of the rhombic vehicle under different working conditions, the method adopts the regional/sub-working condition control, uses the pre-aiming control strategy based on the geometry in the low-speed interval, and uses the pre-aiming control strategy based on the dynamics in the high-speed interval, so that the excellent path tracking performance in the full-speed interval is realized.
In order to make the aforementioned objects, features and advantages of the present disclosure more comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and are not to limit the disclosure.
FIG. 1 is a schematic diagram of a three-axle four-wheel chassis of a diamond vehicle of the present disclosure;
FIG. 2 is a schematic illustration of Ackerman steering geometry and preview geometry for a diamond shaped vehicle according to the present disclosure;
FIG. 3 is a schematic diagram of path tracking errors in the dynamics-based control strategy of the present disclosure;
fig. 4 is a control flow schematic of the present disclosure.
The specific implementation mode is as follows:
the present disclosure is further described with reference to the following drawings and examples.
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
In the present disclosure, terms such as "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "side", "bottom", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only relational terms determined for convenience in describing structural relationships of the parts or elements of the present disclosure, and do not refer to any parts or elements of the present disclosure, and are not to be construed as limiting the present disclosure.
In the present disclosure, terms such as "fixedly connected", "connected", and the like are to be understood in a broad sense, and mean either a fixed connection or an integrally connected or detachable connection; may be directly connected or indirectly connected through an intermediate. The specific meanings of the above terms in the present disclosure can be determined on a case-by-case basis by persons skilled in the relevant art or technicians, and are not to be construed as limitations of the present disclosure.
As described in the background, a diamond-shaped vehicle is a vehicle having a three-axle four-wheel new chassis architecture. The front and rear shafts have independent steering functions, and the middle shaft provides driving force. The existing path tracking control method is not suitable for diamond-shaped vehicles.
The invention provides an unmanned path tracking control method for a rhombic vehicle, which adopts a sectional type and working condition type control strategy aiming at the specific steering geometric relation and transverse dynamics characteristics of the rhombic vehicle. The method comprises the steps that switching is carried out according to the longitudinal speed of a vehicle, and when the longitudinal speed is higher than a preset threshold value, a pre-aiming control strategy based on dynamics is adopted; and when the longitudinal speed is lower than a preset threshold value, adopting a pre-aiming control strategy based on geometry.
The first embodiment is as follows:
a method for controlling unmanned path tracking of a diamond-shaped vehicle includes the following specific steps, as shown in FIG. 4:
and step S001, determining related parameters.
The method specifically comprises the following steps: setting control parameters: mode switching threshold vMPre-aiming distance DLA parameter matrix R and a parameter matrix Q;
determining the geometrical parameters of the vehicle: distance l of vehicle rear axle from vehicle mass centerrDistance l from center axis of vehicle to center of mass of vehiclemDistance l between front axle of vehicle and mass center of vehiclefDistance l between rear axle and middle axle of vehiclermDistance l between front axle of vehicle and middle axle of vehiclefm；
Determining the dynamic parameters of the vehicle: the mass M of the whole vehicle and the rotational inertia I of the vehicle around the gravity center perpendicular to the horizontal planeZRear wheel side yaw stiffness krMiddle wheel cornering stiffness kmFront wheel side deflection rigidity kf。
Of course, as shown in fig. 1, the rhombus vehicle has a three-axis four-wheel configuration, CoG is the vehicle center of gravity, xoy is the vehicle coordinate system, which uses the vehicle center of gravity as the origin, the vehicle body length direction as the x-axis, and the axis perpendicular to the vehicle body length on the horizontal plane as the y-axis.
The front axle and the rear axle of the rhombic vehicle have independent steering functions and provide a tire turning angle control interface. Two wheels of the middle shaft of the bicycle are driving wheels.
The intelligent diamond vehicle is provided with a positioning module (such as a Global Positioning System (GPS)), a sensing module (a motion combination sensor and a laser radar), a decision module, a planning module and a control module. The control module is used for executing the path tracking control strategy provided by the disclosure. The desired path is generated by a planning module. Curvature information c at the point of preview on the desired pathRAre known.
Through the positioning module and the sensing module, the vehicle can acquire the speed v of the vehiclexYaw rate
Figure BDA0003121892570000101
Transverse velocity vyVehicle lateral offset ey(y-direction distance between vehicle and pre-aiming point on desired path), and yaw angle error of vehicle
Figure BDA0003121892570000102
(the difference value of the vehicle yaw angle and the expected yaw angle determined by the slope at the prealignment point on the expected path), the included angle alpha between the connecting line from the center of the central axis of the vehicle to the prealignment point and the x axis, and the like.
Of course, in other embodiments, other modules, such as a camera, a lighting lamp, etc., may be included on the diamond-shaped vehicle. Similarly, the state information of the vehicle may also be obtained by other detection modules, which are not described herein again.
And step S002, judging the working condition state of the vehicle.
Acquiring the longitudinal speed v of a vehiclexIf v isx<vMExecuting a geometric-based preview control strategy, and entering step S003, otherwise executing a dynamic-based preview control strategy, vMTo set the control mode switching threshold, the process proceeds to step S004.
Step S003, a geometric-based preview control strategy:
when the longitudinal speed of the vehicle is low, the tire sideslip phenomenon is not obvious, and the vehicle movement basically conforms to the Ackerman steering geometric relation. The rhombic car steering control strategy designed based on the relation can achieve a relatively ideal control effect under a low-speed working condition.
And S003-1, acquiring an included angle alpha between a connecting line from the center of a central axis of the vehicle to the preview point and the x axis of the vehicle (if the preview point is in the fourth quadrant of the vehicle coordinate system, the alpha sign is negative, otherwise, the alpha sign is positive), and calculating the expected turning radius R of the vehicle according to the included angle alpha. If the vehicle is traveling along the desired turning radius, the vehicle will tend to approach the desired path. As shown in fig. 2, the calculation formula of the desired turning radius is:
Figure BDA0003121892570000111
step S003-2, according to the desired turning radius and the geometric parameter l of the vehiclefmAnd lrmThe steering angle of the front and rear wheels of the vehicle can be calculated by the Ackerman steering geometry relation of the diamond vehicle as shown in figure 3The control quantity sum is specifically calculated by the formula
Figure BDA0003121892570000112
Figure BDA0003121892570000113
Wherein sign (α) is a sign function for α, and when α ≧ 0, sign (α) is 1; when α <0, sign (α) ═ 1.
Step S004, a pre-aiming control strategy based on dynamics:
when the longitudinal speed of the vehicle is high, if the path tracking control is performed by neglecting the dynamic characteristics of the vehicle, an excellent control effect cannot be obtained. And under a high-speed working condition, path tracking control is performed by adopting a dynamic model.
Step S004-1, obtaining vehicle state information yaw rate
Figure BDA0003121892570000114
Transverse velocity vyVehicle yaw angle error
Figure BDA0003121892570000115
Vehicle lateral offset eyIn this embodiment, the parameters are obtained through the positioning module and the sensing module. Calculating error state vectors
Figure BDA0003121892570000121
Wherein the content of the first and second substances,
Figure BDA0003121892570000122
a first derivative is laterally offset for the vehicle,
Figure BDA0003121892570000123
for the first derivative of the vehicle yaw angle error, the calculation formulas are respectively as follows:
Figure BDA0003121892570000124
Figure BDA0003121892570000125
wherein D isLIs the pre-aiming distance.
Step S004-2, calculating a vehicle transverse dynamics parameter a according to the transverse dynamics model of the rhombic vehicle1～a8The diamond-shaped vehicle transverse dynamics calculation formula is as follows:
Figure BDA0003121892570000126
Figure BDA0003121892570000127
wherein the transverse dynamic parameter a of the vehicle1～a8Are respectively calculated as
Figure BDA0003121892570000128
Figure BDA0003121892570000129
Wherein lrIs the distance of the rear axle of the vehicle from the center of mass of the vehicle, lmIs the distance of the vehicle center axis from the vehicle center of mass,/fIs the distance from the front axle of the vehicle to the center of mass of the vehicle, M is the total vehicle mass, IZFor the moment of inertia of the vehicle about the centre of gravity perpendicular to the horizontal, krFor rear wheel cornering stiffness, kmFor cornering stiffness of the middle wheel, kfIs the front wheel cornering stiffness.
Step S004-3, according to the transverse dynamic parameter a of the vehicle1～a8And a diamond vehicle path tracking error dynamic model, calculating error dynamic model parameters A,B. According to the step S004-1 and the step S004-2, the diamond-shaped vehicle path tracking error dynamic model can be obtained as follows:
Figure BDA00031218925700001210
wherein U is [ δ ═ df，δr]For the control vector, A, B is a model parameter, and C is a road curvature-related parameter. A. B, C is calculated as follows:
Figure BDA0003121892570000131
Figure BDA0003121892570000132
wherein, cRIs the curvature at the intended point on the desired path.
Step S004-4, according to a preset parameter matrix Q>0，Q∈R4×4(weight indicating error State), parameter matrix R>0，R∈R2×2(weight representing control cost), the error dynamics model parameter A, B, the calculated control parameter P. The specific calculation process can be realized by solving the following rica-carti equation:
ATP+PA-2PBR-1BTP+Q＝0
and step S004-5, calculating a control vector U according to the control parameter P, the parameter matrix R, the error dynamic model parameter B and the error state vector X. The specific calculation formula is as follows:
U＝-R-1BTPX
step S005, control is performed according to the control strategy result.
The obtained front and rear wheel steering angle control quantity deltafAnd deltarAnd inputting a front and rear wheel steering system to realize stable following of the expected path.
Or the front and rear wheel steering systems are controlled according to the control vector U, so that stable following of the expected path is realized.
In summary, the first embodiment provides a path tracking segmented control strategy based on the longitudinal speed of a rhombic vehicle, when the speed is lower than a set threshold value, the vehicle steering geometric relationship can realize accurate description of vehicle motion, and the path tracking control strategy is designed based on the steering geometric relationship; when the speed is higher than the set threshold value, the dynamic characteristics of the diamond-shaped vehicle cannot be ignored, and a path tracking control strategy is designed based on a dynamic model, so that the excellent path tracking performance of a full speed interval is realized.
Example two
A diamond vehicle autonomous driving path tracking control system comprising:
the parameter determination module is configured to determine geometric parameters and dynamic parameters of the rhombic vehicle and set control parameters;
a speed acquisition module configured to acquire a vehicle longitudinal speed;
and the sub-working condition control module is configured to judge the relation between the longitudinal speed of the vehicle and a set speed control threshold, if the longitudinal speed of the vehicle is less than the speed control threshold, the path tracking control is carried out by using a pre-aiming control method based on geometry, and if not, the path tracking control is carried out by using a pre-aiming control method based on dynamics.
EXAMPLE III
A rhombic vehicle adopts the method provided by the first embodiment or comprises the system provided by the first embodiment or the second embodiment.
The diamond-shaped vehicle further comprises:
the positioning module is used for acquiring rhombic vehicle position information;
the sensing module is used for acquiring the motion state information of the rhombic vehicle;
and the planning module is used for generating the expected path.
According to the positioning module and the sensing module, the speed v of the vehicle can be acquiredxYaw rate
Figure BDA0003121892570000151
Transverse velocity vyVehicle lateral offset eyVehicle yaw angleError of the measurement
Figure BDA0003121892570000152
And the state information of the included angle alpha between the connecting line from the center of the middle axle of the vehicle to the pre-aiming point and the x-axis.
Example four
A computer readable storage medium storing computer instructions which, when executed by a processor, perform the steps of a method provided by one embodiment.
EXAMPLE five
A terminal device, in this embodiment a controller, includes a memory and a processor, and computer instructions stored in the memory and executed on the processor, where the computer instructions, when executed by the processor, perform the steps of the method provided in the first embodiment.
The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure, and various modifications and changes may be made to the present disclosure by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.
Although the present disclosure has been described with reference to specific embodiments, it should be understood that the scope of the present disclosure is not limited thereto, and those skilled in the art will appreciate that various modifications and changes can be made without departing from the spirit and scope of the present disclosure.

Claims (15)

1. A rhombic vehicle automatic driving path tracking control method is characterized by comprising the following steps: the method comprises the following steps:
determining geometric parameters and dynamic parameters of the rhombic vehicle, and setting control parameters;
acquiring the longitudinal speed of the vehicle, judging the relation between the longitudinal speed of the vehicle and a set speed control threshold value, if the longitudinal speed of the vehicle is less than the speed control threshold value, performing path tracking control by using a pre-aiming control method based on geometry, otherwise, performing path tracking control by using a pre-aiming control method based on dynamics;
the specific process of utilizing the pre-aiming control method based on geometry to carry out path tracking control comprises the following steps:
acquiring an included angle between a connecting line from the center of a central shaft of the vehicle to a pre-aiming point and an x-axis of the vehicle, and calculating an expected turning radius of the vehicle according to the included angle;
the calculation method of the expected turning radius R is as follows:
Figure FDA0003551179330000011
wherein D isLFor the pre-aiming distance,/mThe distance between the center axis of the vehicle and the center of mass of the vehicle is defined as alpha, the included angle between the connecting line from the center of the center axis of the vehicle to the prealignment point and the x axis of the vehicle is defined as alpha, when the prealignment point is in the fourth quadrant of the vehicle coordinate system, the sign of the alpha is negative, otherwise, the sign of the alpha is positive;
calculating steering angle control quantities of front and rear wheels of the vehicle according to the expected turning radius, the distance between the rear axle of the vehicle and the middle axle of the vehicle and the distance between the front axle of the vehicle and the middle axle of the vehicle and the Ackerman steering geometric relation of the rhombic vehicle so as to control the vehicle;
steering angle control amount delta of front wheels of vehiclefAnd a steering angle control amount δ of a rear wheel of the vehiclerThe calculation method comprises the following steps:
Figure FDA0003551179330000021
Figure FDA0003551179330000022
wherein R is a desired turning radius lrmIs the distance of the rear axle of the vehicle from the center axle, lfmSign (alpha) is a sign function about alpha, and is the distance between a front axle of the vehicle and a middle axle of the vehicle, and when the alpha is larger than or equal to 0, the sign (alpha) is 1; when alpha is less than 0, sign (alpha) is-1.
2. The automatic driving path tracking control method for the rhombic vehicles as claimed in claim 1, wherein: the geometrical parameters of the rhombic vehicle include but are not limited to the distance l between the rear axle of the vehicle and the mass center of the vehiclerDistance l from center axis of vehicle to center of mass of vehiclemDistance l between front axle of vehicle and mass center of vehiclefDistance l between rear axle and middle axle of vehiclermDistance l from the front axle of the vehicle to the middle axle of the vehiclefm。
3. The automatic driving path tracking control method for the rhombic vehicles as claimed in claim 1, wherein: the dynamic parameters of the rhombic vehicle comprise but are not limited to the mass M of the whole vehicle and the moment of inertia I of the vehicle around the gravity center vertical to the horizontal planeZRear wheel side yaw stiffness krMiddle wheel cornering stiffness kmAnd front wheel side cornering stiffness kf。
4. The automatic driving path tracking control method for the rhombic vehicles as claimed in claim 1, wherein: the control parameter comprises a mode switching threshold vMPre-aiming distance DlA parameter matrix R and a parameter matrix Q.
5. The automatic driving path tracking control method for the rhombic vehicles as claimed in claim 1, wherein: the specific process of utilizing the dynamics-based preview control method to carry out path tracking control comprises the following steps:
calculating an error state vector according to the yaw velocity, the lateral velocity, the vehicle yaw angle error and the vehicle lateral offset of the vehicle;
calculating a vehicle transverse dynamics parameter according to the transverse dynamics model of the rhombic vehicle;
calculating error dynamic model parameters according to the transverse dynamic parameters of the vehicle and the diamond vehicle path tracking error dynamic model to obtain a diamond vehicle path tracking error dynamic model;
and calculating control parameters according to a preset parameter matrix, a preset parameter matrix and error dynamics model parameters, and calculating control vectors according to the control parameters, the preset parameter matrix and the error dynamics model parameters.
6. The automatic driving path tracking control method for the rhombic vehicles as claimed in claim 5, wherein: the method for calculating the error state vector comprises the following steps: yaw rate based on vehicle state information
Figure FDA0003551179330000031
Transverse velocity vyVehicle yaw angle error
Figure FDA0003551179330000032
Vehicle lateral offset eyCalculating error state vectors
Figure FDA0003551179330000033
Wherein the content of the first and second substances,
Figure FDA0003551179330000034
a first derivative is laterally offset for the vehicle,
Figure FDA0003551179330000035
for the first derivative of the vehicle yaw angle error, the calculation formulas are respectively as follows:
Figure FDA0003551179330000036
Figure FDA0003551179330000037
wherein v isxAs longitudinal speed of the vehicle, DLFor a pre-aiming distance, cRCurvature information at the pre-aimed point on the desired path.
7. The automatic driving path tracking control method for the rhombic vehicles as claimed in claim 5, wherein: the specific process for calculating the transverse dynamic parameters of the vehicle comprises the following steps:
the diamond-shaped vehicle transverse dynamics calculation formula is as follows:
Figure FDA0003551179330000038
Figure FDA0003551179330000039
wherein the transverse dynamic parameter a of the vehicle1～a8The calculation formulas of (A) and (B) are respectively as follows:
Figure FDA0003551179330000041
Figure FDA0003551179330000042
wherein lrIs the distance of the rear axle of the vehicle from the center of mass of the vehicle, lmIs the distance of the vehicle center axis from the vehicle center of mass,/fIs the distance from the front axle of the vehicle to the center of mass of the vehicle, M is the total vehicle mass, IZFor the moment of inertia of the vehicle about the centre of gravity perpendicular to the horizontal, krFor rear wheel cornering stiffness, kmFor cornering stiffness of the middle wheel, kfIs the front wheel cornering stiffness.
8. The automatic driving path tracking control method for the rhombic vehicles as claimed in claim 5, wherein: the diamond vehicle path tracking error dynamic model is as follows:
Figure FDA0003551179330000043
wherein U is [ δ ═ df,δr]A, B is a model parameter and C is a road curvature related parameter for a control vectorA, B, C is calculated as follows:
Figure FDA0003551179330000044
Figure FDA0003551179330000045
wherein, cRCurvature at the intended point on the desired path, DLFor the pre-aiming distance, vxIs the vehicle longitudinal speed.
9. The automatic driving path tracking control method for the rhombic vehicles as claimed in claim 5, wherein: the specific process of calculating the control parameters is as follows: solving the Riccati equation: a. theTP+PA-2PBR-1BTP + Q is 0, where P is the control variable, Q is the parameter matrix characterizing the weights of the error states, and A, B is the error dynamics model parameter.
10. The automatic driving path tracking control method for the rhombic vehicles as claimed in claim 5, wherein: the control vector U is: u ═ R-1BTAnd PX, wherein R is a parameter matrix representing the weight of the control cost, B is an error dynamic model parameter, P is a control parameter, and X is an error state vector.
11. A rhombic automatic driving path tracking control system for a vehicle is characterized in that: the method comprises the following steps:
the parameter determination module is configured to determine geometric parameters and dynamic parameters of the rhombic vehicle and set control parameters;
a speed acquisition module configured to acquire a vehicle longitudinal speed;
and the sub-working condition control module is configured to judge the relation between the longitudinal speed of the vehicle and a set speed control threshold, if the longitudinal speed of the vehicle is less than the speed control threshold, the path tracking control is carried out by using a pre-aiming control method based on geometry, and if not, the path tracking control is carried out by using a pre-aiming control method based on dynamics.
12. A diamond-shaped vehicle, characterized by: a diamond vehicle automatic driving path tracking control method adopting any one of claims 1-10 or comprising a diamond vehicle automatic driving path tracking control system of claim 11.
13. A diamond shaped vehicle as set forth in claim 12, wherein: further comprising:
the positioning module is used for acquiring rhombic vehicle position information;
the sensing module is used for acquiring the motion state information of the rhombic vehicle;
and the planning module is used for generating the expected path.
14. A computer-readable storage medium characterized by: for storing computer instructions which, when executed by a processor, perform the steps of a diamond shaped vehicle autopilot path tracking control method of any one of claims 1-10.
15. A terminal device is characterized in that: comprising a memory and a processor and computer instructions stored on the memory and executed on the processor, which when executed by the processor, perform the steps of a diamond shaped vehicle autopilot path tracking control method of any one of claims 1-10.
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