CN114715161A - Longitudinal vehicle speed estimation method based on combined slip control - Google Patents

Longitudinal vehicle speed estimation method based on combined slip control Download PDF

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Publication number
CN114715161A
CN114715161A CN202210503504.XA CN202210503504A CN114715161A CN 114715161 A CN114715161 A CN 114715161A CN 202210503504 A CN202210503504 A CN 202210503504A CN 114715161 A CN114715161 A CN 114715161A
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wheel
longitudinal
speed
acceleration
vehicle speed
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宋大凤
吴佳俊
钱琦峰
曾小华
高皓铭
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Jilin University
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Jilin University
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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
    • B60W40/105—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
    • B60W50/00—Details of control systems for road vehicle drive control not related to the control of a particular sub-unit, e.g. process diagnostic or vehicle driver interfaces
    • 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
    • B60W50/00—Details of control systems for road vehicle drive control not related to the control of a particular sub-unit, e.g. process diagnostic or vehicle driver interfaces
    • B60W2050/0001—Details of the control system
    • B60W2050/0002—Automatic control, details of type of controller or control system architecture
    • 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
    • B60W50/00—Details of control systems for road vehicle drive control not related to the control of a particular sub-unit, e.g. process diagnostic or vehicle driver interfaces
    • B60W2050/0001—Details of the control system
    • B60W2050/0019—Control system elements or transfer functions
    • 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
    • B60W2720/00—Output or target parameters relating to overall vehicle dynamics
    • B60W2720/10—Longitudinal speed
    • 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
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Abstract

The invention provides a longitudinal vehicle speed estimation method based on combined slip control, which ensures that a longitudinal vehicle speed is extracted from four wheel speed signals during the intervention period of wheel slip control. Firstly, measuring the rotating speed of a wheel according to a wheel speed sensor, converting the rotating speed of the wheel into the speed at the position of the mass center of the vehicle through rigid body motion conversion and the relation between the braking force coefficient and the slip ratio, establishing fuzzy logic to obtain the reliability of four wheels, and obtaining the measured value of the longitudinal speed through weighting fusion; then calculating the longitudinal acceleration of the vehicle, correcting the longitudinal acceleration based on the longitudinal vehicle speed measurement value, and further predicting to obtain an estimated value of the longitudinal vehicle speed through the obtained longitudinal acceleration; and finally, performing weighted fusion according to the longitudinal vehicle speed estimated value and the measured value to obtain a final longitudinal vehicle speed estimation result.

Description

Longitudinal vehicle speed estimation method based on combined slip control
Technical Field
The invention relates to a longitudinal speed estimation method based on combined slip control, and belongs to the technical field of vehicle control
Background
In the running process of the vehicle, the longitudinal speed of the vehicle is important information in the active safety system of the vehicle, and has important significance on the stability control of the vehicle. The longitudinal speed of a vehicle needs to be estimated in the automobile stability control, and the currently common longitudinal speed estimation method mainly comprises a kinematic estimation method and a dynamic method. The estimation method based on kinematics mainly comprises a wheel speed method, a direct integration method and other traditional longitudinal vehicle speed estimation methods. The longitudinal vehicle speed estimation method based on dynamics is mainly based on the dynamic model and multi-dimensional information fusion, however, under the complex working condition of vehicle instability, the signal source and the model are often interfered by the outside world and cannot accurately reflect the longitudinal vehicle speed information, and the complexity of the filtering algorithm and the reference information amount are simply improved, so that the estimation precision cannot be improved, and the robustness of the control system is possibly influenced.
Therefore, the problem that the existing longitudinal vehicle speed estimation method based on the dynamic model or the signal filtering processing cannot ensure the robustness under the complex state environment (such as the vehicle in the emergency braking instability state) is solved. The invention provides a longitudinal vehicle speed estimation method based on combined slip control, which ensures that the longitudinal vehicle speed can be extracted from four wheel speed signals all the time during the intervention period of wheel slip control.
Disclosure of Invention
The invention aims to solve the problem of longitudinal speed estimation of a vehicle in a complex state environment (such as an emergency braking process), and ensures that the longitudinal speed can be extracted from four wheel speed signals by introducing slip control.
The invention is realized by adopting the following technical scheme:
the method comprises the following steps: firstly, measuring the rotating speed of a wheel according to a wheel speed sensor, then converting the rotating speed of the wheel into the speed at the position of the mass center of the vehicle, finally formulating fuzzy logic, and weighting and fusing according to the credibility of four wheels to obtain the measured value of the longitudinal speed:
(1) respectively acquiring the number of upper and lower edges and the timing size of the counter from the wheel speed sensor timer and the counter, and calculating the original rotating speed of the wheel;
(2) according to the relation between the braking force coefficient and the slip ratio, correcting the slip ratio of the wheel speed to obtain the longitudinal speed of the wheel center;
the relationship between the longitudinal braking force coefficient of the tire and the slip ratio is as follows:
μ＝Ks
in the formula, mu is a braking force coefficient, K is a proportionality coefficient, and s is a tire slip ratio;
the tire slip ratio s is calculated as follows:
Figure BDA0003635129420000021
in the formula, siIs the tire slip ratio, VxiIs the wheel center longitudinal speed, omegaiThe wheel speed is taken as the wheel speed, and r is the wheel radius (subscript i is 1,2,3,4 respectively represents a left front wheel, a right front wheel, a left rear wheel and a right rear wheel, and the following parameters are all applicable);
according to the above formula, when K, r, mu and other parameters are known, the original wheel rotation speed can be converted into the wheel center longitudinal speed:
Figure BDA0003635129420000022
(3) converting the wheel center longitudinal speed of the wheels to the longitudinal speed at the vehicle mass center according to rigid body motion conversion and by combining measured values such as steering wheel angles, yaw angular speeds and the like;
after the wheel center longitudinal speeds of the four wheels are obtained, the longitudinal linear speeds at the wheel center can be converted to the position of the center of mass according to the rigid body kinematics relationship, and the conversion relationship from the wheel center longitudinal speeds to the position of the center of mass of the four wheels in a wheel coordinate system is obtained through derivation:
Figure BDA0003635129420000023
in formula (II) V'xi(i ═ 1,2,3,4) is the wheel speed at the center of mass, VxiIs the transverse component of the wheel center velocity in the wheel coordinate system, deltaiIs the steering angle of the wheel, L is the wheelbase, omegarThe yaw angular velocity of the vehicle body, and the wheel track B;
(4) according to different working conditions (acceleration, deceleration and sliding), different fuzzy logics are formulated, and the reliability coefficients of the four wheels are calculated (taking the emergency braking condition as an example for analysis);
firstly, identifying and judging the working condition, analyzing by taking the emergency braking condition as an example, when the vehicle is braked emergently, firstly judging that the vehicle enters a deceleration working condition, wherein at the moment, the four tires are likely to have larger slippage, so that the credibility of the four wheels is smaller, and the estimated vehicle speed is inaccurate, so that the slippage control is introduced, under the condition of ensuring the braking performance of the vehicle, one wheel is in an adjustment state, the braking force of the wheel is reduced or the wheel is in a small slippage state, so that the higher credibility of at least one wheel is ensured, and the longitudinal vehicle speed of the vehicle can be accurately reflected;
according to the change rule of the wheel speed under the working condition, the relative stability degree of the wheel is represented in a priority mode on the premise of ensuring the stability, the most preferable wheel is obtained through screening and is used for entering an adjusting state, if the last period of the wheel is already in the adjusting state and the time in the state exceeds the maximum time limit, the wheel is required to jump out of the adjusting state, and the wheel with the next priority enters the adjusting state;
if the four wheels are not selected to enter the adjusting state, the four wheels are in the normal sliding range at present, and the control of the adjusting state is finished;
in order to ensure the smoothness of the vehicle when the wheel is switched into an adjusting state from the normal slip control, an adjusting transition state is introduced between the normal slip control and the adjusting state control, and the switching of the three states is adjusted by adopting a feedforward and feedback method;
finally, calculating the reliability of the current input wheel speed according to parameters such as wheel speed change, acceleration change, stress magnitude and the like;
(5) weighting according to the corrected reliability coefficients of the four wheels and the wheel speeds of the four wheels to obtain a longitudinal vehicle speed measured value;
obtaining a post-confidence pair V 'for each wheel'xiAnd performing weighted fusion to finally obtain a longitudinal vehicle speed measured value as follows:
Figure BDA0003635129420000031
in formula (II) V'xLongitudinal vehicle speed measurement weighted for four wheel speeds and used as Kalman filtering measurement, fiWeighting coefficients of the wheels are calculated by fuzzy logic and represent the credibility of each wheel;
step two: calculating the longitudinal acceleration of the vehicle, correcting the longitudinal acceleration based on the longitudinal vehicle speed measurement value, and further predicting the longitudinal acceleration to obtain an estimated value of the longitudinal vehicle speed:
(1) firstly, calculating to obtain an estimated value of a longitudinal acceleration deviant according to a dynamic model of the acceleration deviant, then calculating to obtain a measured value of the acceleration deviant by combining a longitudinal vehicle speed measured value and the deviation of the estimated value, and then weighting and fusing the estimated value and the measured value to obtain a longitudinal acceleration correction value;
calculating the offset of the longitudinal acceleration and the corrected longitudinal acceleration:
aoff(k+1)＝aoff(k)+Ka_off(V'x(k)-Vax(k))
in the formula, aoff(k +1) is an acceleration offset value of the k +1 th cycle, aoff(k) Is the acceleration offset value of the K-th cycle, Ka_offIs a weighting coefficient, is used for aoff(k) Smoothing filter, Vax(k) Is an estimate of longitudinal vehicle speed, V ', of the k-th cycle'x(k) Longitudinal vehicle speed measurements for the kth cycle;
(2) according to the stress of the four wheels and based on a dynamic model, calculating a longitudinal acceleration based on the model as a basic value of the longitudinal acceleration;
(3) combining the acceleration basic value and the acceleration correction value, summing to obtain the longitudinal acceleration of the vehicle, and obtaining a longitudinal vehicle speed estimation value according to longitudinal acceleration integration;
corrected longitudinal acceleration
Figure BDA0003635129420000032
Comprises the following steps:
Figure BDA0003635129420000033
in the formula, axFor longitudinal acceleration based on model solution, aoffIs the offset value of the acceleration;
then, obtaining a longitudinal vehicle speed estimated value according to the corrected longitudinal speed:
Figure BDA0003635129420000034
where T is the time step for each estimation period,
Figure BDA0003635129420000035
is the longitudinal acceleration estimated value of the k-1 th period,
Figure BDA0003635129420000036
longitudinal acceleration corrected for the k-th cycle;
step three: weighting according to the longitudinal vehicle speed estimated value and the measured value to obtain a final longitudinal vehicle speed estimation result:
weighting and fusing the measured value and the estimated value of the longitudinal speed to obtain a final longitudinal speed estimation result:
Figure BDA0003635129420000041
in the formula, KxA weighting factor for the longitudinal vehicle speed estimate.
Compared with the prior art, the invention has the beneficial effects that:
1. compared with the existing longitudinal vehicle speed estimation method based on a dynamic model or signal filtering processing, the method has the advantage that the robustness of the vehicle cannot be guaranteed in a complex state environment. The invention provides a longitudinal vehicle speed estimation method based on combined slip control, which ensures that the longitudinal vehicle speed can be extracted from four wheel speed signals all the time during the intervention period of wheel slip control.
2. Under the complex operation condition, a special slip control state, namely an adjustment state is introduced, the wheel speed change is optimized by adjusting the wheel braking force, a series of optimal setting procedures are needed for the wheels to enter and exit the state, the reliability of the optimal wheels is improved, and the robustness of a longitudinal vehicle speed estimation algorithm is ensured.
Drawings
The invention is further described with reference to the accompanying drawings in which:
FIG. 1 longitudinal vehicle speed estimation overview flow chart
FIG. 2 longitudinal vehicle speed measurement calculation flow chart
FIG. 3 flow chart for longitudinal vehicle speed estimate calculation
FIG. 4 is a flow chart of final longitudinal vehicle speed estimate calculation
Detailed Description
Referring to fig. 1, the invention is realized by adopting the following technical scheme:
the method comprises the following steps: referring to fig. 2, firstly, the wheel speed is measured according to the wheel speed sensor, then the wheel speed is converted into the speed at the position of the vehicle mass center, finally, fuzzy logic is formulated, and the measured value of the longitudinal vehicle speed is obtained according to the reliability weighting fusion of the four wheels:
(1) respectively acquiring the number of upper and lower edges and the timing size of the counter from the wheel speed sensor timer and the counter, and calculating the original rotating speed of the wheel;
(2) according to the relation between the braking force coefficient and the slip ratio, correcting the slip ratio of the wheel speed to obtain the longitudinal speed of the wheel center;
the relationship between the longitudinal braking force coefficient of the tire and the slip ratio is as follows:
μ＝Ks
in the formula, mu is a braking force coefficient, K is a proportionality coefficient, and s is a tire slip ratio;
the tire slip ratio s is calculated as follows:
Figure BDA0003635129420000051
in the formula, siIs the tire slip ratio, VxiIs the wheel center longitudinal speed, omegaiThe wheel speed is taken as the wheel speed, and r is the wheel radius, (subscript i is 1,2,3,4 respectively represents a left front wheel, a right front wheel, a left rear wheel and a right rear wheel, and the following parameters are all applicable);
according to the above formula, when K, r, μ, etc. parameters are known, the original wheel speed can be converted into the wheel center longitudinal speed:
Figure BDA0003635129420000052
(3) converting the wheel center longitudinal speed of the wheels to the longitudinal speed at the vehicle mass center according to rigid body motion conversion and by combining measured values such as steering wheel angles, yaw angular speeds and the like;
after the wheel center longitudinal speeds of the four wheels are obtained, the wheel center longitudinal speeds can be converted to the center of mass from the longitudinal linear speeds at the wheel center according to rigid body kinematics relationship, and the conversion relationship from the wheel center longitudinal speeds to the center of mass of the four wheels in a wheel coordinate system is obtained through derivation:
Figure BDA0003635129420000053
in formula (II) V'xi(i ═ 1,2,3,4) is the wheel speed at the center of mass, VxiIs the transverse component of the wheel center velocity in the wheel coordinate system, deltaiIs the steering angle of the wheel, L is the wheelbase, omegarThe yaw rate of the vehicle body and the wheel track B are respectively;
(4) according to different working conditions (acceleration, deceleration and sliding), different fuzzy logics are formulated, and the reliability coefficients of the four wheels are calculated (taking the emergency braking condition as an example for analysis);
firstly, identifying and judging the working condition, analyzing by taking the emergency braking condition as an example, when the vehicle is braked emergently, firstly judging that the vehicle enters a deceleration working condition, wherein at the moment, the four tires are likely to have larger slippage, so that the credibility of the four wheels is smaller, and the estimated vehicle speed is inaccurate, so that the slippage control is introduced, under the condition of ensuring the braking performance of the vehicle, one wheel is in an adjustment state, the braking force of the wheel is reduced or the wheel is in a small slippage state, so that the higher credibility of at least one wheel is ensured, and the longitudinal vehicle speed of the vehicle can be accurately reflected;
according to the change rule of the wheel speed under the working condition, the relative stability degree of the wheel is represented in a priority mode on the premise of ensuring the stability, the most preferable wheel is obtained through screening and is used for entering an adjusting state, if the last period of the wheel is already in the adjusting state and the time in the state exceeds the maximum time limit, the wheel is required to jump out of the adjusting state, and the wheel with the next priority enters the adjusting state;
if the four wheels are not selected to enter the adjusting state, the four wheels are in the normal sliding range at present, and the control of the adjusting state is finished;
in order to ensure the smoothness of the vehicle when the wheel is switched into an adjusting state from the normal slip control, an adjusting transition state is introduced between the normal slip control and the adjusting state control, and the switching of the three states is adjusted by adopting a feedforward and feedback method;
finally, calculating the reliability of the current input wheel speed according to parameters such as wheel speed change, acceleration change, stress magnitude and the like;
(5) weighting according to the corrected reliability coefficients of the four wheels and the wheel speeds of the four wheels to obtain a longitudinal vehicle speed measured value;
obtaining a post-confidence pair V 'for each wheel'xiAnd performing weighted fusion to finally obtain a longitudinal vehicle speed measured value as follows:
Figure BDA0003635129420000061
in formula (II) V'xLongitudinal vehicle speed measurement weighted for four wheel speeds and used as Kalman filtering measurement, fiWeighting coefficients of the wheels are calculated by fuzzy logic and represent the credibility of each wheel;
step two: referring to FIG. 3, the longitudinal acceleration of the vehicle is calculated and corrected based on the longitudinal vehicle speed measurement, and then further predicted by the longitudinal acceleration to yield an estimate of the longitudinal vehicle speed:
(1) firstly, calculating to obtain an estimated value of a longitudinal acceleration deviant according to a dynamic model of the acceleration deviant, then calculating to obtain a measured value of the acceleration deviant by combining a longitudinal vehicle speed measured value and the deviation of the estimated value, and then performing weighted fusion on the estimated value and the measured value to obtain a longitudinal acceleration correction value;
calculating the offset of the longitudinal acceleration and the corrected longitudinal acceleration:
aoff(k+1)＝aoff(k)+Ka_off(V'x(k)-Vax(k))
in the formula, aoff(k +1) is the acceleration offset value of the k +1 th cycle, aoff(k) Is the acceleration offset value of the K-th cycle, Ka_offIs a weighting coefficient, is used for aoff(k) Smoothing filter, Vax(k) Is an estimate of longitudinal vehicle speed, V ', of the k-th cycle'x(k) Longitudinal vehicle speed measurements for the kth cycle;
(2) according to the stress of the four wheels and based on a dynamic model, calculating the longitudinal acceleration based on the model as a basic value of the longitudinal acceleration;
(3) combining the acceleration basic value and the acceleration correction value, summing to obtain the longitudinal acceleration of the vehicle, and obtaining a longitudinal vehicle speed estimation value according to longitudinal acceleration integration;
corrected longitudinal acceleration
Figure BDA0003635129420000062
Comprises the following steps:
Figure BDA0003635129420000063
in the formula, axFor longitudinal acceleration based on model solution, aoffIs the offset value of the acceleration;
then, obtaining a longitudinal vehicle speed estimated value according to the corrected longitudinal speed:
Figure BDA0003635129420000071
where T is the time step for each estimation period,
Figure BDA0003635129420000072
is the longitudinal acceleration estimated value of the k-1 th period,
Figure BDA0003635129420000073
longitudinal acceleration corrected for the k-th cycle;
step three: referring to fig. 4, weighting is performed according to the longitudinal vehicle speed estimation value and the measured value to obtain a final longitudinal vehicle speed estimation result:
weighting and fusing the measured value and the estimated value of the longitudinal speed to obtain a final longitudinal speed estimation result:
Figure BDA0003635129420000074
in the formula, KxA weighting factor for the longitudinal vehicle speed estimate.

Claims (1)

1. A longitudinal vehicle speed estimation method combining slip control is characterized by comprising the following steps:
the method comprises the following steps: firstly, the wheel rotating speed is measured according to a wheel speed sensor, then the wheel rotating speed is converted into the speed at the position of the mass center of the vehicle, finally, fuzzy logic is formulated, and the measured value of the longitudinal vehicle speed is obtained according to the weighted fusion of the credibility of the four wheels:
(1) respectively acquiring the number of upper and lower edges and the timing size of the counter from the wheel speed sensor timer and the counter, and calculating the original rotating speed of the wheel;
(2) according to the relation between the braking force coefficient and the slip ratio, correcting the slip ratio of the wheel speed to obtain the longitudinal speed of the wheel center;
the relationship between the longitudinal braking force coefficient of the tire and the slip ratio is as follows:
μ＝Ks
in the formula, mu is a braking force coefficient, K is a proportionality coefficient, and s is a tire slip ratio;
the tire slip ratio s is calculated as follows:
Figure FDA0003635129410000011
in the formula, siIs the tire slip ratio, VxiIs the wheel center longitudinal speed, omegaiThe wheel speed is taken as the wheel speed, and r is the wheel radius (subscript i is 1,2,3,4 respectively represents a left front wheel, a right front wheel, a left rear wheel and a right rear wheel, and the following parameters are all applicable);
according to the above formula, when K, r, mu and other parameters are known, the original wheel rotation speed can be converted into the wheel center longitudinal speed:
Figure FDA0003635129410000012
(3) converting the wheel center longitudinal speed of the wheels to the longitudinal speed at the vehicle mass center according to rigid body motion conversion and by combining measured values such as steering wheel angles, yaw angular speeds and the like;
after the wheel center longitudinal speeds of the four wheels are obtained, the wheel center longitudinal speeds can be converted to the center of mass from the longitudinal linear speeds at the wheel center according to rigid body kinematics relationship, and the conversion relationship from the wheel center longitudinal speeds to the center of mass of the four wheels in a wheel coordinate system is obtained through derivation:
Figure FDA0003635129410000021
in formula (II) V'xi(i ═ 1,2,3,4) is the wheel speed at the center of mass, VxiIs the transverse component of the wheel center velocity in the wheel coordinate system, deltaiIs the steering angle of the wheel, L is the wheelbase, omegarFor vehicle body yaw rateDegree, B is the track width;
(4) according to different working conditions (acceleration, deceleration and sliding), different fuzzy logics are formulated, and the reliability coefficients of the four wheels are calculated (taking the emergency braking condition as an example for analysis);
firstly, identifying and judging the working condition, analyzing by taking the emergency braking condition as an example, when the vehicle is braked emergently, firstly judging that the vehicle enters a deceleration working condition, wherein at the moment, the four tires are likely to have larger slippage, so that the credibility of the four wheels is smaller, and the estimated vehicle speed is inaccurate, so that the slippage control is introduced, under the condition of ensuring the braking performance of the vehicle, one wheel is in an adjustment state, the braking force of the wheel is reduced or the wheel is in a small slippage state, so that the higher credibility of at least one wheel is ensured, and the longitudinal vehicle speed of the vehicle can be accurately reflected;
according to the change rule of the wheel speed under the working condition, the relative stability degree of the wheel is represented in a priority mode on the premise of ensuring the stability, the most preferable wheel is obtained through screening and is used for entering an adjusting state, if the last period of the wheel is already in the adjusting state and the time in the state exceeds the maximum time limit, the wheel is required to jump out of the adjusting state, and the wheel with the next priority enters the adjusting state;
if none of the four wheels is selected to enter the adjusting state, the current four wheels are in the normal sliding range, and the adjusting state control is finished;
in order to ensure the smoothness of the vehicle when the wheel is switched into an adjusting state from the normal slip control, an adjusting transition state is introduced between the normal slip control and the adjusting state control, and the switching of the three states is adjusted by adopting a feedforward and feedback method;
finally, calculating the reliability of the current input wheel speed according to parameters such as wheel speed change, acceleration change, stress magnitude and the like;
(5) weighting according to the corrected reliability coefficients of the four wheels and the wheel speeds of the four wheels to obtain a longitudinal vehicle speed measured value;
obtaining a confidence value back pair V 'of each wheel'xiAnd performing weighted fusion to finally obtain a longitudinal vehicle speed measured value as follows:
Figure FDA0003635129410000031
in formula (II) V'xLongitudinal vehicle speed measurement weighted for four wheel speeds and used as Kalman filtering measurement, fiWeighting coefficients for the wheels are calculated by fuzzy logic and represent the credibility of each wheel;
step two: calculating the longitudinal acceleration of the vehicle, correcting the longitudinal acceleration based on the longitudinal vehicle speed measurement value, and further predicting the longitudinal acceleration to obtain an estimated value of the longitudinal vehicle speed:
(1) firstly, calculating to obtain an estimated value of a longitudinal acceleration deviant according to a dynamic model of the acceleration deviant, then calculating to obtain a measured value of the acceleration deviant by combining a longitudinal vehicle speed measured value and the deviation of the estimated value, and then performing weighted fusion on the estimated value and the measured value to obtain a longitudinal acceleration correction value;
calculating the offset of the longitudinal acceleration and the corrected longitudinal acceleration:
aoff(k+1)＝aoff(k)+Ka_off(V'x(k)-Vax(k))
in the formula, aoff(k +1) is the acceleration offset value of the k +1 th cycle, aoff(k) Is the acceleration offset value of the K-th cycle, Ka_offIs a weighting coefficient, is used for aoff(k) Smoothing filter, Vax(k) Is an estimate of longitudinal vehicle speed, V ', of the kth cycle'x(k) A longitudinal vehicle speed measurement for a kth cycle;
(2) according to the stress of the four wheels and based on a dynamic model, calculating the longitudinal acceleration based on the model as a basic value of the longitudinal acceleration;
(3) combining the acceleration basic value and the acceleration correction value, summing to obtain the longitudinal acceleration of the vehicle, and obtaining a longitudinal vehicle speed estimation value according to longitudinal acceleration integration;
corrected longitudinal acceleration
Figure FDA0003635129410000041
Comprises the following steps:
Figure FDA0003635129410000042
in the formula, axFor longitudinal acceleration based on model solution, aoffIs the offset value of the acceleration;
then, obtaining a longitudinal vehicle speed estimated value according to the corrected longitudinal speed:
Figure FDA0003635129410000043
where T is the time step for each estimation period,
Figure FDA0003635129410000044
is the longitudinal acceleration estimated value of the k-1 th period,
Figure FDA0003635129410000045
longitudinal acceleration corrected for the k-th cycle;
step three: weighting according to the longitudinal vehicle speed estimated value and the measured value to obtain a final longitudinal vehicle speed estimation result:
weighting and fusing the measured value and the estimated value of the longitudinal speed to obtain a final longitudinal speed estimation result:
Figure FDA0003635129410000046
in the formula, KxA weighting factor for the longitudinal vehicle speed estimate.
CN202210503504.XA 2022-05-09 2022-05-09 Longitudinal vehicle speed estimation method based on combined slip control Pending CN114715161A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024022051A1 (en) * 2022-07-29 2024-02-01 中国第一汽车股份有限公司 Method and apparatus for controlling vehicle, and electronic device and storage medium
WO2024037130A1 (en) * 2022-08-18 2024-02-22 中国第一汽车股份有限公司 Center-of-mass velocity determination method and device

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024022051A1 (en) * 2022-07-29 2024-02-01 中国第一汽车股份有限公司 Method and apparatus for controlling vehicle, and electronic device and storage medium
WO2024037130A1 (en) * 2022-08-18 2024-02-22 中国第一汽车股份有限公司 Center-of-mass velocity determination method and device

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