CN111469855A - Vehicle motion parameter calculation method - Google Patents

Vehicle motion parameter calculation method Download PDF

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Publication number
CN111469855A
CN111469855A CN202010314469.8A CN202010314469A CN111469855A CN 111469855 A CN111469855 A CN 111469855A CN 202010314469 A CN202010314469 A CN 202010314469A CN 111469855 A CN111469855 A CN 111469855A
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vehicle
wheel
center
speed
axle
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黄丙胜
张磊
吕金桐
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Beijing Yikong Zhijia Technology Co Ltd
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Beijing Yikong Zhijia Technology 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
    • B60W40/00—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models
    • B60W40/10—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models related to vehicle motion
    • 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
    • B60W40/00—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models
    • B60W40/10—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models related to vehicle motion
    • B60W40/101—Side slip angle of tyre
    • 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
    • B60W40/00—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models
    • B60W40/10—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models related to vehicle motion
    • B60W40/109—Lateral acceleration
    • 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
    • B60W2520/125—Lateral acceleration
    • 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
    • B60W2520/26—Wheel slip
    • B60W2520/263—Slip values between front and rear axle
    • 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
    • B60W2520/26—Wheel slip
    • B60W2520/266—Slip values between left and right wheel
    • 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
    • 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

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Mathematical Physics (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Steering Control In Accordance With Driving Conditions (AREA)

Abstract

A method for calculating vehicle motion parameters includes: s1, obtaining vehicle geometric parameters and establishing a vehicle model and a coordinate system, wherein the geometric parameters at least comprise the geometric position relation of the front axle center and the rear axle center of the vehicle; s2, acquiring the primary motion parameters of the vehicle; s3, acquiring speed vectors of the center of the front shaft and the center of the rear shaft according to the geometric parameters and the primary motion parameters; s4, acquiring the tire slip angle of the front wheel and the tire slip angle of the rear wheel according to the speed vectors of the front axle center and the rear axle center; s5, acquiring the lateral acceleration of the vehicle according to the primary motion parameters of the vehicle; and S6, obtaining the steering stability coefficient of the vehicle according to the lateral acceleration, the slip angle of the front wheels and the slip angle of the rear wheels. The estimation precision of the vehicle running parameters is improved by uniformly converting the measured values in different reference systems. Meanwhile, the motion state of the vehicle can be comprehensively measured, and a plurality of state parameter bases are provided for the stable control and the path planning of the vehicle.

Description

Vehicle motion parameter calculation method
Technical Field
The disclosure relates to the technical field of vehicle motion parameter estimation, in particular to a vehicle motion parameter calculation method.
Background
In order to improve mine production efficiency and economic benefits, the mining area gradually changes to automatic and intelligent directions, wherein the popularization and application of unmanned technology can reduce the driver personnel cost of transport vehicle fleets, promote transport efficiency and avoid personnel potential safety hazards. In the unmanned driving process of the mining vehicle, accurate motion control and optimal decision planning of the vehicle need to obtain accurate vehicle motion parameters, and accurate estimation of the vehicle motion parameters has important significance for realization of the mining unmanned driving technology. In the prior art, the motion state of the vehicle under the high-speed working condition is accurately estimated by reasonably simplifying and properly calculating a vehicle dynamic model, and the vehicle running state information is obtained by properly modeling the vehicle dynamic process by utilizing an improved extended Kalman filtering algorithm. According to the technology, a certain vehicle model is established to obtain vehicle motion state parameters, a reasonable vehicle dynamics model and a kinematics model are the premise and the basis of vehicle stability control, but the working scene of a mining vehicle is an unstructured road, the uncertainty and disturbance of the model are large, ideal vehicle model parameters are different from real vehicle motion parameters, and vehicle sensors are usually required to be mounted on the mining unmanned vehicle to obtain the vehicle motion parameters. Therefore, it is common to calculate and monitor state parameters during the driving process of the vehicle in real time by collecting and analyzing information related to the acceleration of the vehicle, determining the driving state of the vehicle using an acceleration sensor, or estimating the stability of the vehicle using the vehicle speed and attitude angle by analyzing the characteristics of the vehicle. The technology judges part of vehicle running state parameters by using a vehicle speed sensor, an attitude angle sensor or an acceleration sensor, and can not reflect the running state of the vehicle comprehensively and accurately. In order to realize safe unmanned driving of the mining vehicle, the running state of the vehicle cannot be completely judged by acquiring a single or a small number of vehicle state parameters, and various sensors are required to be mounted on the vehicle for measuring the motion parameters of the vehicle in the full state. Due to the fact that the motion characteristics of the mining vehicle are complex, the load state can also change, information measured by each sensor is possibly not in the same reference system, large errors exist when the motion parameters of the vehicle are directly estimated, and the measured information needs to be converted and unified. An Inertial Navigation System (INS) is an important device for acquiring vehicle navigation parameters, and generally requires that an internal inertial measurement unit is installed at a vehicle yaw rotation center, and if the installation position of the inertial measurement unit is not coincident with the vehicle yaw rotation center, the inertial measurement unit interferes with the existence of acceleration and interference speed, and the measurement accuracy of the vehicle parameters is affected.
Disclosure of Invention
Technical problem to be solved
The present disclosure provides a method for calculating a vehicle motion parameter, which at least solves the above technical problems.
(II) technical scheme
A method for calculating vehicle motion parameters includes: s1, obtaining vehicle geometric parameters and establishing a vehicle model and a coordinate system, wherein the geometric parameters at least comprise the geometric position relation of the front axle center and the rear axle center of the vehicle; s2, acquiring the primary motion parameters of the vehicle; s3, acquiring speed vectors of the center of the front shaft and the center of the rear shaft according to the geometric parameters and the primary motion parameters; s4, acquiring the tire slip angle of the front wheel and the tire slip angle of the rear wheel according to the speed vectors of the front axle center and the rear axle center; s5, acquiring the lateral acceleration of the vehicle according to the primary motion parameters of the vehicle; and S6, obtaining the steering stability coefficient of the vehicle according to the lateral acceleration, the tire slip angle of the front wheels and the tire slip angle of the rear wheels.
Optionally, the primary motion parameter includes a steering wheel angle of the vehicle, and step S4 is specifically: s41, obtaining the steering angle of the front wheels of the vehicle according to the steering wheel angle of the vehicle and the steering transmission ratio of the steering wheel; s42, obtaining the tire slip angle of the front wheel according to the steering angle of the front wheel and the included angle between the speed vector of the front axle center and the longitudinal axis; and S43, obtaining the tire slip angle of the rear wheel according to the included angle between the speed vector of the center of the rear axle and the longitudinal axis of the vehicle.
Alternatively, the steering angle of the front wheels of the vehicle in step S41fThe calculation formula is as follows:
f＝θs/Rs
wherein, thetasTo the steering wheel angle, RsIs the squareSteering gear ratio to the steering wheel;
tire slip angle α of front wheel in step S42fThe calculation formula of (2) is as follows:
αf＝(f-θVf)
wherein, thetaVfIs the angle between the velocity vector at the center of the front axle and the longitudinal axis,
Figure BDA0002457745210000021
wherein v isf，xIs the partial velocity, v, of the velocity vector of the center of the front axle in the x-axis direction of the vehicle coordinate systemf，yThe component speed of the speed vector of the center of the front axle in the y-axis direction of the vehicle coordinate system;
tire slip angle α of rear wheel in step S43rThe calculation formula of (2) is as follows:
αr＝-θVr
wherein, thetaVrIs the angle between the velocity vector at the center of the rear axle and the longitudinal axis,
Figure BDA0002457745210000031
wherein v isr，xIs the partial velocity, v, of the velocity vector of the center of the rear axle in the x-axis direction of the vehicle coordinate systemr，yIs the component velocity of the velocity vector of the front axle center in the direction of the v axle of the vehicle coordinate system.
Optionally, step S2 is preceded by installing a plurality of sensors on the vehicle, and in step S2, the primary motion parameters of the vehicle are obtained through the plurality of sensors.
Alternatively, the calculation formula of the lateral acceleration of the vehicle in step S5 is:
Figure BDA0002457745210000032
wherein the content of the first and second substances,
Figure BDA0002457745210000033
is the acceleration in the coordinate system of the vehicle,
Figure BDA0002457745210000034
as lateral acceleration of the vehicle, anIs the acceleration a in the sensorn＝(ae，an，au)T，
Figure BDA0002457745210000035
Is a direction cosine matrix of the sensor to vehicle coordinate system.
Alternatively, in step S6, the stability coefficient K of the vehicle is calculated by the formula:
Figure BDA0002457745210000036
wherein, LfrThe wheelbase of the front axle and the rear axle of the vehicle.
Optionally, the method further includes calculating a yaw rotation center of the vehicle according to the geometric parameters, where the yaw rotation center is an origin of the coordinate system.
Optionally, the plurality of sensors includes an inertial measurement unit, and the compensation of the lever arm disturbance acceleration and the disturbance velocity is performed if the inertial measurement unit is not coincident with the swing rotation center.
Optionally, the primary motion parameters further include a wheel speed of a front wheel of the vehicle and a speed of a center of the front wheel relative to a vehicle coordinate system, and a wheel speed of a rear wheel of the vehicle and a speed of a center of the rear wheel relative to the vehicle coordinate system, and the slip rates of the front wheel and the rear wheel are calculated from the wheel speeds of the front wheel and the rear wheel and the speeds of the center of the front wheel and the center of the rear wheel relative to the vehicle coordinate system.
Optionally, the vehicle comprises two front wheels, namely a front axle left side wheel and a front axle right side wheel, and two rear wheels, namely a rear axle left side wheel and a rear axle right side wheel, and the slip ratio of the front wheels and the rear wheels is calculated by the following formula:
slip ratio S of left wheel of front axleflThe calculation formula of (2) is as follows:
Figure BDA0002457745210000041
wherein, VflIs the left side of the front axleForward speed of wheel center, Vfl，wThe wheel speed of the left wheel of the front axle;
the slip ratio of the wheels on the right side of the front axle is calculated by the formula:
Figure BDA0002457745210000042
wherein, VfrThe forward speed, V, of the center of the wheel on the right side of the front axlefr，wThe wheel speed of the wheel on the right side of the front axle;
slip ratio S of left wheel of rear axlerlThe calculation formula of (a) is as follows:
during braking:
Figure BDA0002457745210000043
when in driving:
Figure BDA0002457745210000044
wherein, VrlIs the forward speed, V, of the center of the wheel on the left side of the rear axlerl，wThe wheel speed of the left wheel of the rear axle;
slip ratio S of right wheel of rear axlerrThe calculation formula of (a) is as follows:
during braking:
Figure BDA0002457745210000045
when in driving:
Figure BDA0002457745210000046
wherein, VrrThe forward speed, V, of the center of the wheel on the right side of the rear axlerr，wThe wheel speed of the right wheel of the rear axle.
(III) advantageous effects
The utility model provides a vehicle motion parameter calculation method, when the installation position of the inertia measurement unit is not coincident with the vehicle swing rotation center, the lever arm interference acceleration and the interference speed are compensated, and the estimation precision of the vehicle motion parameter can be improved when the vehicle moves in high dynamic motion after the interference compensation; the estimation precision of the vehicle running parameters is improved by uniformly converting the measured values in different reference systems; meanwhile, parameters such as a vehicle slip angle, a tire slip angle, a steering characteristic stability coefficient, lateral acceleration, an attitude angle rate and the like can be accurately estimated, the motion state of the vehicle can be comprehensively measured, and a plurality of state parameter bases are provided for stable control and path planning of the vehicle.
Drawings
FIG. 1 schematically illustrates a flow chart of a method of calculating vehicle motion parameters according to an embodiment of the present disclosure;
fig. 2 schematically shows a vehicle model of a vehicle according to an embodiment of the present disclosure.
Detailed Description
A method for calculating a vehicle motion parameter, as shown in fig. 1, the method comprising: s1, obtaining vehicle geometric parameters and establishing a vehicle model and a coordinate system, wherein the geometric parameters at least comprise the geometric position relation of the front axle center and the rear axle center of the vehicle; s2, acquiring the primary motion parameters of the vehicle; s3, acquiring speed vectors of the center of the front shaft and the center of the rear shaft according to the geometric parameters and the primary motion parameters; s4, acquiring the tire slip angle of the front wheel and the tire slip angle of the rear wheel according to the speed vectors of the front axle center and the rear axle center; s5, acquiring the lateral acceleration of the vehicle according to the primary motion parameters of the vehicle; and S6, obtaining the steering stability coefficient of the vehicle according to the lateral acceleration, the slip angle of the front wheels and the slip angle of the rear wheels.
In order to make the objects, solutions and advantages of the present invention more apparent, the method according to the present disclosure will be described in detail below, in connection with specific embodiments, and with reference to the accompanying drawings, by way of example of a driverless mining vehicle.
And S1, acquiring vehicle geometric parameters and establishing a vehicle model and a coordinate system, wherein the geometric parameters at least comprise the geometric position relation of the front axle center and the rear axle center of the vehicle.
The unmanned mining vehicle in the embodiment of the invention is a vehicle with a single-steering front axle and double-drive rear axles, and models the double-drive rear axles to obtain a virtual rear axle 6 and virtual rear wheels 3rl and 4 rr. The vehicle model comprises four wheels, namely a front axle left wheel, a front axle right wheel, a rear axle left wheel and a rear axle right wheel.
And measuring the geometric positions of all equipment in the vehicle by using a measuring instrument, and referring to fig. 2, the geometric positions at least comprise a front left wheel center 1flc, a front right wheel center 2frc, a rear left wheel center 3rlc, a rear right wheel center 4rrc, a front axle center 7, a rear axle center 8 and the position vector relation of an inertial measurement unit in a vehicle coordinate system.
And acquiring a swing rotation center of the vehicle according to the geometric position relationship, establishing a coordinate system by taking the swing rotation center as a coordinate origin, taking the vehicle length direction as an X axis and taking the direction which is perpendicular to the X axis and is parallel to the axle as a Y axis, wherein the head direction, the left side of the Y axis and the upper side of the z axis of the coordinate system are positive directions. General, if a ═ a (a)x，ay，az)TIs a variable in the coordinate system, then ax、ay、azThe components of the variable in the three axes of the coordinate system are shown respectively.
And S2, acquiring the primary motion parameters of the vehicle.
A plurality of sensors are installed on the vehicle, and parameters measured by the sensors are primary motion parameters. The sensor may include: the system comprises a strapdown inertial navigation system, high-precision satellite navigation receiving equipment, a wheel speed sensor, a steering wheel corner sensor, an accelerator sensor and a brake sensor.
Wherein the measurement information output by the strapdown inertial navigation system comprises a gyro angular rate wibSpecific force f of accelerometeribEtc.; the measurement information output by the high-precision satellite navigation receiving equipment comprises position, speed, time, course angle and the like.
The SINS/GNSS integrated navigation system is composed of the strapdown inertial navigation system and the satellite navigation receiving equipment, and the measurement information output by the SINS/GNSS integrated navigation system comprises time (time:)UTC time), location pn＝(L，λ，h)T(wherein L represents latitude, λ represents longitude, and h represents altitude), and navigation system velocity vn＝(ve，vn，vu)T(wherein, veEast velocity, vnIs the north velocity, vuIn the direction of the sky), the navigation system acceleration an＝(ae，an，au)T(wherein, a)eIs east acceleration, anIs the north acceleration, auAcceleration in the sky), attitude angle
Figure BDA0002457745210000061
(wherein γ is a roll angle, θ is a pitch angle,
Figure BDA0002457745210000062
As heading angle), attitude angle rate
Figure BDA0002457745210000063
(wherein,
Figure BDA0002457745210000064
is the roll angle rate,
Figure BDA0002457745210000065
Is the pitch angle rate,
Figure BDA0002457745210000066
Is the heading angular rate).
The measurement information output by the wheel speed sensor comprises the wheel speed V of the left wheel of the front axlefl，wFront axle right wheel speed Vfr，wRear axle left wheel speed Vrl，wAnd the wheel speed V of the right wheel of the rear axlerr，w。
The measurement information output from the steering wheel angle sensor includes steering wheel angle information θs。
The measurement information output by the throttle sensor includes the accelerator pedal stroke.
The measurement information output by the brake sensor includes the brake pedal travel.
And S3, acquiring the speed vectors of the front axle center and the rear axle center according to the geometric parameters and the primary motion parameters.
The speed of the vehicle at the swing rotation center, the front axle center, the rear axle center, the left front wheel, the right front wheel, the left rear wheel, the right rear wheel and the like can be derived according to the information output by the SINS/GNSS combined navigation system and the geometric position relation of the vehicle.
The speed of the vehicle swing rotation center in the vehicle coordinate system is as follows: v. ofo＝(vo，xvo，yvoz)T。
The speed of the front axle center in the vehicle coordinate system is: v. off＝(vf，xvf，yvf，z)T。
The speed of the rear axle center in the vehicle coordinate system is: v. ofr＝(vr，xvr，yvr，z)T。
The speed of the left wheel of the front axle in the vehicle coordinate system is as follows: v. offl＝(vfl，xvfl，yvfl，z)T。
The speed of the right wheel of the front axle in the vehicle coordinate system is as follows: v. offr＝(vfr，xvfr，yvfr，z)T。
The speed of the left wheel of the rear axle in the vehicle coordinate system is: v. ofrl＝(vrl，xvrl，yvrl，z)T。
The speed of the right wheel of the rear axle in the vehicle coordinate system is: v. ofrr＝(vrr，xvrr，yvrr，z)T。
When the mounting position of the Inertial Measurement Unit (IMU) coincides with the vehicle roll rotation center, compensation of lever arm disturbance acceleration and disturbance velocity, i.e. vo＝vIMUIn the formula, vIMUThe velocity of the IMU mounting location in the vehicle coordinate system.
When the installation position of an Inertial Measurement Unit (IMU) is not coincident with the swinging rotation center of the vehicle, a lever arm stem is requiredCompensation of disturbance acceleration and disturbance velocity, i.e. vo＝vIMU-wnb×rIMUIn the formula rIMUFor a position vector, w, of the IMU mounting position in the vehicle coordinate systemnbIs the angular rate of rotation of the vehicle coordinate system relative to the navigation system.
From the above speeds, the slip rates of the front and rear wheels can be calculated as follows:
slip ratio S of left wheel of front axleflThe calculation formula of (2) is as follows:
Figure BDA0002457745210000071
wherein, VflThe forward speed, V, of the center of the wheel on the left side of the front axlefl，wThe wheel speed of the left wheel of the front axle;
the slip ratio of the wheels on the right side of the front axle is calculated by the formula:
Figure BDA0002457745210000072
wherein, VfrThe forward speed, V, of the center of the wheel on the right side of the front axlefr，wThe wheel speed of the wheel on the right side of the front axle;
slip ratio S of left wheel of rear axlerlThe calculation formula of (a) is as follows:
during braking:
Figure BDA0002457745210000081
when in driving:
Figure BDA0002457745210000082
wherein, VrlIs the forward speed, V, of the center of the wheel on the left side of the rear axlerl，wThe wheel speed of the left wheel of the rear axle;
slip ratio S of right wheel of rear axlerrThe calculation formula of (a) is as follows:
during braking:
Figure BDA0002457745210000083
when in driving:
Figure BDA0002457745210000084
wherein, VrrThe forward speed, V, of the center of the wheel on the right side of the rear axlerr，wThe wheel speed of the right wheel of the rear axle.
S4, tire slip angles of the front wheels and the rear wheels are obtained from the velocity vectors of the front axle center and the rear axle center.
The method specifically comprises the following steps:
and S41, obtaining the steering angle of the front wheels of the vehicle according to the steering wheel angle of the vehicle and the steering transmission ratio of the steering wheel.
Steering angle of front wheel of vehiclefThe calculation formula is as follows:
f＝θs/Rs
wherein, thetasTo the steering wheel angle, RsIs the steering gear ratio of the steering wheel.
And S42, obtaining the tire slip angle of the front wheel according to the steering angle of the front wheel and the included angle between the velocity vector of the front axle center and the vertical axis.
Tire slip angle α for front wheelfThe calculation formula of (2) is as follows:
αf＝(f-θVf)
wherein, thetaVfIs the angle between the velocity vector at the center of the front axle and the longitudinal axis,
Figure BDA0002457745210000091
wherein v isf，xIs the partial velocity, v, of the velocity vector of the center of the front axle in the x-axis direction of the vehicle coordinate systemf，yIs the component speed of the speed vector of the front axle center in the y-axis direction of the vehicle coordinate system.
And S43, obtaining the tire slip angle of the rear wheel according to the included angle between the speed vector of the center of the rear axle and the longitudinal axis of the vehicle.
Tire slip angle α for rear wheelsrThe calculation formula of (2) is as follows:
αr＝-θVr
wherein, thetaVrIs the angle between the velocity vector at the center of the rear axle and the longitudinal axis,
Figure BDA0002457745210000092
wherein v isr，xIs the partial velocity, v, of the velocity vector of the center of the rear axle in the x-axis direction of the vehicle coordinate systemr，yIs the component speed of the speed vector of the front axle center in the y-axis direction of the vehicle coordinate system.
And S5, acquiring the lateral acceleration of the vehicle according to the primary motion parameters of the vehicle.
The calculation formula of the lateral acceleration of the vehicle is:
Figure BDA0002457745210000093
wherein the content of the first and second substances,
Figure BDA0002457745210000094
is the acceleration in the coordinate system of the vehicle,
Figure BDA0002457745210000095
as lateral acceleration of the vehicle, anIs the acceleration a in the sensorn＝(ae，an，au)T，
Figure BDA0002457745210000096
Is a direction cosine matrix of the sensor to vehicle coordinate system.
And S6, obtaining the steering stability coefficient of the vehicle according to the lateral acceleration, the tire slip angle of the front wheels and the tire slip angle of the rear wheels. The calculation formula of the steering stability coefficient K of the vehicle is as follows:
Figure BDA0002457745210000097
wherein, LfrIs the wheelbase between the front and rear axles of the vehicle.
In conclusion, when the installation position of the inertia measurement unit is not coincident with the swing rotation center of the vehicle, the interference acceleration and the interference speed of the lever arm are compensated, and the estimation precision of the motion parameters of the vehicle can be improved when the vehicle moves in a high dynamic motion after the interference compensation; the estimation precision of the vehicle running parameters is improved by uniformly converting the measured values in different reference systems; meanwhile, parameters such as a vehicle slip angle, a tire slip angle, a steering characteristic stability coefficient, lateral acceleration, an attitude angle rate and the like can be accurately estimated, the motion state of the vehicle can be comprehensively measured, and a plurality of state parameter bases are provided for stable control and path planning of the vehicle.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A method for calculating vehicle motion parameters includes:
s1, obtaining vehicle geometric parameters and establishing a vehicle model and a coordinate system, wherein the geometric parameters at least comprise the geometric position relation between the front axle center and the rear axle center of the vehicle;
s2, acquiring a primary motion parameter of the vehicle;
s3, acquiring the speed vectors of the front axle center and the rear axle center according to the geometric parameters and the primary motion parameters;
s4, acquiring the tire slip angle of the front wheel and the tire slip angle of the rear wheel according to the speed vectors of the front axle center and the rear axle center;
s5, acquiring the lateral acceleration of the vehicle according to the primary motion parameters of the vehicle;
and S6, obtaining the steering stability coefficient of the vehicle according to the lateral acceleration, the tire slip angle of the front wheels and the tire slip angle of the rear wheels.
2. The calculation method according to claim 1, wherein the primary motion parameter includes a steering wheel angle of the vehicle, and the step S4 is specifically as follows:
s41, obtaining the steering angle of the front wheels of the vehicle according to the steering wheel angle of the vehicle and the steering transmission ratio of the steering wheel;
s42, obtaining the tire slip angle of the front wheel according to the steering angle of the front wheel and the included angle between the speed vector of the front axle center and the longitudinal axis;
and S43, obtaining the tire slip angle of the rear wheel according to the included angle between the speed vector of the rear axle center and the longitudinal axis of the vehicle.
3. The calculation method according to claim 2, wherein the steering angle of the front wheels of the vehicle in step S41fThe calculation formula is as follows:
f＝θs/Rs
wherein, thetasTo the steering wheel angle, RsIs the steering gear ratio of the steering wheel;
the tire slip angle α of the front wheel in the step S42fThe calculation formula of (2) is as follows:
αf＝(f-θVf)
wherein, thetaVfIs the angle between the velocity vector at the center of the front axle and the longitudinal axis,
Figure FDA0002457745200000011
wherein v isf，xIs the partial velocity, v, of the velocity vector of the center of the front axle in the x-axis direction of the vehicle coordinate systemf，yThe component speed of the speed vector of the center of the front axle in the y-axis direction of the vehicle coordinate system is obtained;
the tire slip angle α of the rear wheel in the step S43rThe calculation formula of (2) is as follows:
αr＝-θVr
wherein, thetaVrIs the angle between the velocity vector at the center of the rear axle and the longitudinal axis,
Figure FDA0002457745200000021
wherein v isr，xIs the partial velocity, v, of the velocity vector of the rear axle center in the x-axis direction of the vehicle coordinate systemr，yThe component speed of the speed vector of the front axle center in the y-axis direction of the vehicle coordinate system is obtained.
4. The calculation method according to claim 1 or 3, wherein the step S2 is preceded by installing a plurality of sensors on the vehicle, and the step S2 is preceded by acquiring the primary motion parameters of the vehicle through the plurality of sensors.
5. The calculation method according to claim 4, wherein the calculation formula of the lateral acceleration of the vehicle in step S5 is:
Figure FDA0002457745200000022
wherein the content of the first and second substances,
Figure FDA0002457745200000023
is the acceleration in the coordinate system of the vehicle,
Figure FDA0002457745200000024
is the lateral acceleration of the vehicle, anFor the navigation system acceleration a in the sensorn＝(ae，an，au)T，
Figure FDA0002457745200000025
A direction cosine matrix that navigates the sensor to the vehicle coordinate system.
6. The calculation method according to claim 5, wherein in the step S6, the stability coefficient K of the vehicle is calculated by the formula:
Figure FDA0002457745200000026
wherein, LfrThe wheelbase of the front axle and the rear axle of the vehicle.
7. The calculation method according to claim 4, further comprising calculating a yaw rotation center of the vehicle from the geometric parameters, the yaw rotation center being an origin of the coordinate system.
8. The computing method of claim 7, wherein the plurality of sensors comprises an inertial measurement unit, and wherein the inertial measurement unit compensates for lever arm disturbance acceleration and disturbance velocity if the inertial measurement unit is not coincident with the center of yaw rotation.
9. The calculation method according to claim 1, the primary motion parameters further comprising a wheel speed of a front wheel of the vehicle and a speed of a center of the front wheel in the vehicle coordinate system, and a wheel speed of a rear wheel of the vehicle and a speed of a center of the rear wheel in the vehicle coordinate system, the slip rate of the front and rear wheels being calculated from the wheel speeds of the front and rear wheels and the vehicle coordinate system speeds of the center of the front and rear wheels.
10. The calculation method according to claim 9, wherein the vehicle includes two front wheels, i.e., a front-axle left-side wheel and a front-axle right-side wheel, and two rear wheels, i.e., a rear-axle left-side wheel and a rear-axle right-side wheel, and the slip rates of the front wheels and the rear wheels are calculated by:
slip ratio S of left wheel of front axleflThe calculation formula of (2) is as follows:
Figure FDA0002457745200000031
wherein, VflThe forward speed, V, of the center of the wheel on the left side of the front axlefl，wThe wheel speed of the left wheel of the front axle;
the slip ratio of the wheels on the right side of the front axle is calculated by the formula:
Figure FDA0002457745200000032
wherein, VfrThe forward speed, V, of the center of the wheel on the right side of the front axlefr，wThe wheel speed of the wheel on the right side of the front axle;
slip ratio S of left wheel of rear axlerlThe calculation formula of (a) is as follows:
during braking:
Figure FDA0002457745200000033
when in driving:
Figure FDA0002457745200000034
wherein, VrlIs the forward speed, V, of the center of the wheel on the left side of the rear axlerl，wThe wheel speed of the left wheel of the rear axle;
slip ratio S of right wheel of rear axlerrThe calculation formula of (a) is as follows:
during braking:
Figure FDA0002457745200000035
when in driving:
Figure FDA0002457745200000041
wherein, VrrThe forward speed, V, of the center of the wheel on the right side of the rear axlerr，wThe wheel speed of the right wheel of the rear axle.
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