阅读说明：本技术 一种基于车辆轨迹的轮胎转角估算方法 (Tire rotation angle estimation method based on vehicle track ) 是由 具大源 李晓宇 张兴兴 于 2021-08-20 设计创作，主要内容包括：本发明公开了一种基于车辆轨迹的轮胎转角估算方法：S100：在车体上安装GNSS天线,在车辆方向盘的电机上安装编码器；S200：根据GNSS位置坐标计算车辆的航向角；S300：根据计算得到的航向角得到航向角差值和车体偏航角速率；S400：根据车体运动学计算轮胎的绝对转角；S500：读取车辆方向盘电机上编码器的数值,对该数值进行计算处理得到相应的编码器转角；再对编码器转角进行修正；S600：当轮胎转角变化率大于设定阈值时使用卡尔曼滤波算法估算轮胎转角；发明结合了基于车辆轨迹计算的轮胎转角长期稳定以及通过编码器计算的轮胎转角短期精度高的特点,能够在农机车辆正常作业的情况下提供精确、稳定性高的轮胎转角。(The invention discloses a tire corner estimation method based on vehicle tracks, which comprises the following steps: s100: the GNSS antenna is arranged on the vehicle body, and the encoder is arranged on the motor of the vehicle steering wheel; s200: calculating the course angle of the vehicle according to the GNSS position coordinates; s300: obtaining a course angle difference value and a vehicle body yaw rate according to the calculated course angle; s400: calculating an absolute rotation angle of the tire according to the vehicle body kinematics; s500: reading a numerical value of an encoder on a motor of a vehicle steering wheel, and calculating the numerical value to obtain a corresponding encoder corner; then correcting the rotation angle of the encoder; s600: when the tire rotation angle change rate is larger than a set threshold value, estimating a tire rotation angle by using a Kalman filtering algorithm; the invention combines the characteristics of long-term stability of the tire rotation angle calculated based on the vehicle track and high short-term precision of the tire rotation angle calculated by the encoder, and can provide the tire rotation angle with high precision and high stability under the condition of normal operation of agricultural vehicles.)

1. A vehicle trajectory-based tire rotation angle estimation method, characterized by comprising:

s100: the GNSS antenna is arranged on the vehicle body, and the encoder is arranged on the motor of the vehicle steering wheel;

s200: calculating the course angle of the vehicle according to the GNSS position coordinates;

s300: obtaining a course angle difference value according to the course angle obtained by calculation in the step S200, and calculating the yaw rate of the vehicle body according to the course angle difference value;

s400: calculating an absolute rotation angle of the tire according to the vehicle body kinematics;

s500: reading a numerical value of an encoder on a motor of a vehicle steering wheel, and calculating the numerical value to obtain a corresponding encoder corner; correcting the rotation angle of the encoder;

s600: and when the tire rotation angle change rate is larger than a set threshold value, estimating the tire rotation angle by using a Kalman filtering algorithm.

2. A vehicle-track-based tire rotation angle estimation method according to claim 1, wherein: the step S200 includes:

s201: acquiring position information of an east coordinate and a north coordinate of a vehicle body through a GNSS antenna;

s202: obtaining a coordinate difference of an east coordinate of the vehicle body and a north coordinate of the vehicle body according to the position information obtained in the step S201;

s203: calculating the course angle of the vehicle according to a formula, wherein the formula is as follows: psi ═ tan-^-1(Δ E/Δ N); wherein ψ represents a heading angle; Δ E represents a coordinate difference of the vehicle body coordinate east; Δ N represents a coordinate difference of the vehicle body coordinate north.

3. A vehicle-track-based tire rotation angle estimation method according to claim 2, wherein: in the step S201, the sampling frequency of the GNSS antenna is 10 Hz; in step S202, data at fixed time intervals are used to calculate the coordinate difference between the east coordinate of the vehicle body and the north coordinate of the vehicle body, so as to obtain the heading angle of the vehicle at fixed time intervals.

4. A vehicle-track-based tire rotation angle estimation method according to claim 1, wherein: in step S300, the calculation formula of the yaw rate of the vehicle body is:wherein, the delta psi is a course angle difference; Δ t is the time interval.

5. A vehicle-track-based tire rotation angle estimation method according to claim 1, wherein: the step S400 includes:

s401: measuring the wheel base of the vehicle to obtain the running speed of the vehicle;

s402: calculating the absolute rotation angle of the vehicle body tire according to a formula:wherein L is the wheelbase of the vehicle; v is the running speed of the vehicle;is the yaw rate of the vehicle body.

6. A vehicle-track-based tire rotation angle estimation method according to claim 1, wherein: the step S500 includes:

s501: dividing the read value of the encoder on the vehicle steering wheel motor by the vehicle transmission ratio to obtain the tire rotation angle theta of the vehicle based on the steering wheel rotation angle_e；

S502: the absolute rotation angle theta of the vehicle body tire calculated in the step S400_vAngle of rotation theta of tyre with said vehicle_eMaking difference between them, calculating difference value delta theta ═ theta_v-θ_e；

S503: averaging the first three seconds of data of the difference value delta theta to obtain an average value of the first three seconds of data of the difference value delta theta, compensating the encoder by the average value to obtain a smooth tire rotation angle theta_t。

7. A vehicle-track-based tire rotation angle estimation method according to claim 1, wherein: the step S600:

s601: listing a vehicle state space equation as follows:

wherein, theta_rTo estimate a tire rotation angle; theta_tA tire rotation angle obtained for compensating the encoder; τ is a time constant; u. of_rAnd u_tAre each theta_rAnd theta_tCorresponding noise;

s602: the vehicle output equations are listed as follows:

wherein y is the measurement output;

s603: discretizing the vehicle state space equation and the vehicle output equation to respectively obtain discrete equations of the vehicle state space equation and the vehicle output equation:

where Δ t is the sampling time interval, θ_r(k) Representing the tire rotation angle at time k.

Technical Field

The invention relates to the technical field of automatic control, in particular to a tire rotation angle estimation method based on a vehicle track.

Background

An agricultural machinery automatic driving system is a device system for steering control of a vehicle according to position information of the vehicle. In the automatic driving steering control of the agricultural machinery, the vehicle needs to be controlled in real time by taking the tire rotation angle as a feedback quantity; the accurate measurement of the tire rotation angle is one of the important prerequisites for realizing the steering control of the agricultural machinery; the traditional method for measuring the tire rotation angle is to install a Hall angle sensor on a tire, and the reading of the sensor is taken as the measurement value of the tire rotation angle, although the measurement value is accurate, the method has the defects of complex installation, high price, easy abrasion and the like; in addition, the tire rotation angle can also be estimated by mounting a gyroscope on the vehicle body and the front axle of the vehicle respectively, calculating the relative coordinates between the two and fusing the relative coordinates with the speed information of the vehicle, but the method is also high in cost; in ideal conditions, the tire rotation angle may be calculated from the steering wheel rotation angle and the vehicle transmission ratio; if the encoder is arranged on the steering wheel to read the steering wheel angle, the tire angle can be directly calculated through the transmission ratio; however, in the actual operation process of the agricultural vehicle, due to the existence of the problems of pressure relief and clearance, the relationship between the steering wheel corner and the tire corner has the condition of no correspondence: when the steering wheel angle changes, the tire angle does not change; the problems of aging and abrasion exist in the using process of the agricultural vehicle, so that the problems of pressure relief and clearance cannot be avoided; when these two problems exist, the accurate tire angle cannot be obtained using the steering wheel angle and the gear ratio.

Disclosure of Invention

The present invention is directed to a method for estimating a tire rotation angle based on a vehicle track, so as to solve the problems of the background art.

In order to solve the technical problems, the invention provides the following technical scheme: a vehicle trajectory-based tire rotation angle estimation method, the estimation method comprising:

s100: the GNSS antenna is arranged on the vehicle body, and the encoder is arranged on the motor of the vehicle steering wheel;

s200: calculating the course angle of the vehicle according to the GNSS position coordinates;

s300: obtaining a course angle difference value according to the course angle obtained by calculation in the step S200, and calculating the yaw rate of the vehicle body according to the course angle difference value;

s400: calculating an absolute rotation angle of the tire according to the vehicle body kinematics;

s500: reading a numerical value of an encoder on a motor of a vehicle steering wheel, and calculating the numerical value to obtain a corresponding encoder corner; then correcting the rotation angle of the encoder;

s600: when the tire rotation angle change rate is larger than a set threshold value, estimating a tire rotation angle by using a Kalman filtering algorithm;

the method can estimate the optimal value of the tire rotation angle, gives the optimal estimation under the condition of large rotation angle change rate, and repeats the process, so that the tire rotation angle can be continuously estimated under the condition of normal operation of the vehicle.

Further, step S200 includes:

s201: acquiring position information of an east coordinate and a north coordinate of a vehicle body through a GNSS antenna;

s202: obtaining a coordinate difference of an east coordinate of the vehicle body and a north coordinate of the vehicle body according to the position information obtained in the step S201;

s203: calculating the course angle of the vehicle according to a formula, wherein the formula is as follows: psi ═ tan-^-1(Δ E/Δ N); wherein ψ represents a heading angle; Δ E represents a coordinate difference of the vehicle body coordinate east; Δ N represents a coordinate difference of the vehicle body coordinate north.

Further, in step S201, the sampling frequency of the GNSS antenna is 10 Hz; in step S202, data at fixed time intervals are used to calculate the coordinate difference between the east coordinate of the vehicle body and the north coordinate of the vehicle body, so as to obtain the heading angle of the vehicle at fixed time intervals;

by setting the sampling frequency of the GNSS antenna to be 10Hz and calculating the coordinate difference of the east coordinate and the north coordinate of the vehicle coordinate by adopting data at fixed time intervals, the influence of noise can be reduced in practical use, and a more accurate calculation result can be obtained.

Further, the calculation formula of the yaw rate of the vehicle body in step S300 is:wherein, the delta psi is a course angle difference; Δ t is the time interval;

compared with the Z-axis angular rate read by a gyroscope, the vehicle body yaw angular rate calculated by using the vehicle body track greatly reduces noise, and further improves the precision of estimating the tire rotation angle in subsequent calculation.

Further, step S400 includes:

s401: measuring the wheel base of the vehicle to obtain the running speed of the vehicle;

s402: calculating the absolute rotation angle of the vehicle body tire according to the formula:wherein L is the wheelbase of the vehicle; v is the running speed of the vehicle;is the yaw rate of the vehicle body.

Further, step S500 includes:

s501: dividing the read value of the encoder on the vehicle steering wheel motor by the vehicle transmission ratio to obtain the tire rotation angle theta of the vehicle based on the steering wheel rotation angle_e；

S502: the absolute rotation angle theta of the vehicle body tire calculated in the step S400_vAngle of rotation theta of vehicle tyre_eMaking difference between them, calculating difference value delta theta ═ theta_v-θ_e；

S503: averaging the first three seconds of data of the difference value delta theta to obtain an average value of the first three seconds of data of the difference value delta theta, compensating the encoder by the average value to obtain a smooth tire corner theta_t；

Experimental errors always occur in the process of calculating the tire rotation angle, and data fluctuation caused by the experimental errors can be reduced through the steps, so that the tire rotation angle theta obtained after the encoder is compensated_tAnd more accurate.

Further, step S600:

s601: listing the vehicle state space equation as follows:

wherein, theta_rTo estimate a tire rotation angle; theta_tA tire rotation angle obtained for compensating the encoder; τ is a time constant; u. of_rAnd u_tAre each theta_rAnd theta_tCorresponding noise;

s602: the vehicle output equations are listed as follows:

wherein y is the measurement output;

s603: discretizing the vehicle state space equation and the vehicle output equation to respectively obtain the discrete equations of the vehicle state space equation and the vehicle output equation:

where Δ t is the sampling time interval, θ_r(k) Represents the tire rotation angle at the time k;

since the above method of compensating the encoder cannot obtain an accurate tire rotational angle in the case where the tire rotational angle change rate is larger than the threshold value, the above steps can be applied to the case where this occurs, so that an optimum estimation is given in the case where the tire rotational angle change rate is larger than the threshold value.

Compared with the prior art, the invention has the following beneficial effects: the tire rotation angle is calculated through the motion track of the vehicle and the kinematics of the vehicle, and the rotation angle is fused with the steering wheel rotation angle read by the encoder to estimate the tire rotation angle; the characteristics of long-term stability of the tire rotation angle calculated based on the vehicle track and high short-term accuracy of the tire rotation angle calculated through the encoder are combined, and the tire rotation angle with accuracy and high stability can be provided under the condition of normal operation of the agricultural vehicle.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

fig. 1 is a flowchart illustrating a tire rotation angle estimation method based on a vehicle track.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1, the present invention provides a technical solution: a vehicle trajectory-based tire rotation angle estimation method, the estimation method comprising:

s100: the GNSS antenna is arranged on the vehicle body, and the encoder is arranged on the motor of the vehicle steering wheel;

s200: calculating the course angle of the vehicle according to the GNSS position coordinates; wherein, step S200 includes:

s201: acquiring position information of an east coordinate and a north coordinate of a vehicle body through a GNSS antenna; wherein, in step S201, the sampling frequency of the GNSS antenna is 10 Hz; in step S202, data at fixed time intervals are used to calculate the coordinate difference between the east coordinate of the vehicle body and the north coordinate of the vehicle body, so as to obtain the heading angle of the vehicle at fixed time intervals;

s202: obtaining a coordinate difference of an east coordinate of the vehicle body and a north coordinate of the vehicle body according to the position information obtained in the step S201;

s203: calculating the course angle of the vehicle according to a formula, wherein the formula is as follows: psi ═ tan-^-1(Δ E/Δ N); wherein ψ represents a heading angle; Δ E represents a coordinate difference of the vehicle body coordinate east; Δ N represents a coordinate difference of the vehicle body coordinate north;

s300: obtaining a course angle difference value according to the course angle obtained by calculation in the step S200, and calculating the yaw rate of the vehicle body according to the course angle difference value; the calculation formula of the yaw rate of the vehicle body is as follows:wherein, the delta psi is a course angle difference; Δ t is the time interval;

s400: calculating an absolute rotation angle of the tire according to the vehicle body kinematics; wherein, step S400 includes:

s401: measuring the wheel base of the vehicle to obtain the running speed of the vehicle;

s402: calculating the absolute rotation angle of the vehicle body tire according to the formula:wherein L is the wheelbase of the vehicle; v is the running speed of the vehicle;is the yaw rate of the vehicle body;

s500: reading a numerical value of an encoder on a motor of a vehicle steering wheel, and calculating the numerical value to obtain a corresponding encoder corner; then correcting the rotation angle of the encoder; wherein, step S500 includes:

s501: dividing the read value of the encoder on the vehicle steering wheel motor by the vehicle transmission ratio to obtain the tire rotation angle theta of the vehicle based on the steering wheel rotation angle_e；

S502: the absolute rotation angle theta of the vehicle body tire calculated in the step S400_vAngle of rotation theta of vehicle tyre_eMaking difference between them, calculating difference value delta theta ═ theta_v-θ_e；

S503: for the first three seconds of the difference value delta thetaAveraging the data to obtain the average value of the data of the first three seconds of the difference value delta theta, compensating the encoder by the average value to obtain the smooth tire corner theta_t；

S600: when the tire rotation angle change rate is larger than a set threshold value, estimating a tire rotation angle by using a Kalman filtering algorithm;

wherein, the step S600:

s601: listing the vehicle state space equation as follows:

wherein, theta_rTo estimate a tire rotation angle; theta_tA tire rotation angle obtained for compensating the encoder; τ is a time constant; u. of_rAnd u_tAre each theta_rAnd theta_tCorresponding noise;

s602: the vehicle output equations are listed as follows:

wherein y is the measurement output;

s603: discretizing the vehicle state space equation and the vehicle output equation to respectively obtain the discrete equations of the vehicle state space equation and the vehicle output equation:

where Δ t is the sampling time interval, θ_r(k) Representing the tire rotation angle at time k.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.