CN114355924B - Improved pure tracking path tracking method - Google Patents
Improved pure tracking path tracking method Download PDFInfo
- Publication number
- CN114355924B CN114355924B CN202111630228.5A CN202111630228A CN114355924B CN 114355924 B CN114355924 B CN 114355924B CN 202111630228 A CN202111630228 A CN 202111630228A CN 114355924 B CN114355924 B CN 114355924B
- Authority
- CN
- China
- Prior art keywords
- steering wheel
- control period
- output
- tracking
- angle
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Abstract
The application relates to the technical field of intelligent driving, in particular to an improved pure tracking path tracking method, which comprises the steps of determining a pre-aiming point, calculating the curvature of an expected path, converting the curvature into a front wheel equivalent turning angle, and obtaining a steering wheel turning angle of each control period; the sampling value of the steering wheel angle of each control period is weighted with the actual output value of the last control period after the steering wheel angle of the first control period is directly output, so that an effective filtering value is obtained; calculating the difference between the current steering wheel angle to be processed and the steering wheel angle output in the previous control period, and updating the number of steering signals when the difference exceeds a threshold value; only when the number of signals to be turned exceeds a preset value and the difference between the signals to be turned and the last control period is larger than a preset step length, turning is performed. Compared with the traditional pure tracking algorithm, the method improves the tracking precision, improves the riding comfort and meets the requirement of path tracking of the vehicle under the working condition of low speed and large curvature.
Description
Technical Field
The application relates to the technical field of intelligent driving, in particular to an improved pure tracking path tracking method.
Background
Path tracking refers to the fact that in an inertial coordinate system, an unmanned vehicle starts from a given initial state, follows and reaches an ideal geometric path, and the initial point of the vehicle may or may not be on the path. To achieve lateral control of the vehicle, i.e., path tracking, the vehicle is automatically steered to travel along a reference trajectory while ensuring ride comfort. Pure tracking is a widely adopted tracking algorithm, and because of good robustness, the method ignores the transverse dynamics characteristic of the vehicle and is widely applied to the unmanned vehicle path tracking field. The method is based on a tracking algorithm derived from a bicycle model, and the basic idea is that in each updating period, the steering wheel angle is calculated through selection of a pretightening distance and a pretightening point, so that the center of the rear wheel moves along a desired path.
The core of the pure tracking algorithm is the selection of the pretightening distance. The pre-aiming distance is too large, the vehicle slowly approaches the expected path along an arc with smaller curvature, the vehicle tracking cannot generate large oscillation in the approaching process, but the tracking error is increased and the accuracy is reduced when the vehicle approaches the expected path; the pretightening distance is too small, and the expected path can be approximated in a short time, but steering wheel rotation angle adjustment is discontinuous, control quantity is discretized, control oscillation is caused, and passenger comfort is poor.
It should be noted that the foregoing description of the background art is only for the purpose of providing a clear and complete description of the technical solution of the present application and is presented for the convenience of understanding by those skilled in the art. The above-described solutions are not considered to be known to the person skilled in the art simply because they are set forth in the background of the application section.
Disclosure of Invention
The purpose of the application is that: aiming at the defects, an improved pure tracking path tracking algorithm is provided, the tracking precision is improved, meanwhile, the pretightening distance is selected without limit in a mode of low-pass filtering and setting a plurality of threshold constraint steering angle output under the working condition of low speed and large curvature, steering wheel shake is greatly reduced, and tracking stability is improved.
The technical scheme of the application is as follows: an improved pure tracking path tracking method comprises the following steps:
firstly, taking the current vehicle position as a circle center, taking a pre-aiming distance as a radius to make a circle, determining a pre-aiming point at an intersection point of the pre-aiming distance and a front untracked path, calculating the curvature of the expected path according to a geometric relationship, and converting the curvature into a front wheel equivalent turning angle to obtain a steering wheel turning angle of each control period;
step two, low-pass filtering, namely, except for directly outputting steering wheel angles in a first control period, weighting a sampling value of the steering wheel angles in each control period with an actual output value in a last control period to obtain an effective filtering value;
step three, calculating the number of signals to be turned, calculating the difference between the current steering wheel angle to be processed and the steering wheel angle output in the previous control period, comparing the difference with a preset threshold value, and updating the number of the turning signals when the difference exceeds the threshold value;
and step four, updating the state quantity, wherein steering can be performed only when the number of signals to be steered exceeds a preset value and the difference between the signals to be steered and the previous control period is larger than a preset step length, and otherwise, the steering wheel rotation angle of the previous control period is still output.
Further, after the pretightening point is determined in the first step, the pretightening distance l d The relationship between the current heading of the vehicle and the chord cut angle magnitude α of the expected curvature circle is:
wherein R is an expected curvature radius, and is obtained by arrangement:
and because the curvature kappa=1/R, the pretightening curvature kappa and the pretightening distance l are pretighten d The relationship is as follows:
combining with a simplified kinematic model of the vehicle, the method comprises the following steps of:
where L is the vehicle wheelbase, t is each control period, where L d Under the fixed condition, the corresponding front wheel equivalent rotation angle delta (t) can be calculated for each alpha, and then the steering wheel rotation angle in the control period is obtained.
Further, the specific calculation formula of the low-pass filtering in the second step is as follows:
θ pro(t) ＝θ output(t-1) ·β+θ e(t) ·(1-β)
wherein θ pro(t) For the current steering wheel angle to be processed, θ output(t-1) Steering wheel angle, θ, for the last control period output e(t) And (3) outputting a desired steering wheel angle for the pure tracking algorithm of the current control period, wherein beta is a weight coefficient.
Further, the specific formula for updating the number of the steering signals in the step three is as follows:
wherein up, down is the number of left (right) turn signals, and is initially 0; steerjspace is the set steering threshold.
Further, the specific updating method in the fourth step is as follows:
when the up, down number is less than or equal to the set number control threshold value control_space, the steering wheel angle theta outputted in the last control period is still outputted output(t-1) As a current output;
when the up and down numbers exceed a set threshold, judging whether the vehicle needs to act or not by controlling_space; if theta is dif If the absolute value of (a) exceeds the set step control threshold step_space, then θ will be pro(t) As a vehicle current position steering control output; otherwise, the steering wheel angle theta of the last control period is still output output(t-1) 。
The scheme of the application has the following beneficial effects:
according to the application, on the basis of a traditional pure tracking algorithm, through setting weights to carry out low-pass filtering on expected output values in a period, the output is enabled to have feedback effect on the input, an effective filtering value is obtained, the weight of new data is reduced, the weight of a history expected output corner is increased, meanwhile, the steering angle is restrained by a plurality of thresholds to be output, the tracking precision is improved, the riding comfort is improved, and the requirement of path tracking of a vehicle under the working condition of low speed and large curvature is met; in addition, the pretightening distance can be selected without limit under the applicable working condition, so that the difficult problems that a large number of experiments are required to select a proper pretightening distance or the pretightening distance is not proper according to experience are avoided; the application has simple realization and effective tracking, and meets the application requirement;
other advantageous effects of the present application will be described in detail in the detailed description section which follows.
Drawings
FIG. 1 is a flow chart of the steps of the present application;
FIG. 2 is a schematic diagram of the calculation of the equivalent rotation angle of the front wheel according to the present application;
FIG. 3 is a schematic diagram of an experimental reference trajectory of the present application;
FIG. 4 is a diagram of the present application d Comparison of tracking accuracy simulation results at=1.5m;
FIG. 5 is the diagram of the present application d Comparison of tracking accuracy simulation results when the number is 2 m;
FIG. 6 is the diagram of the present application d Comparison of tracking accuracy simulation results when=2.5m;
FIG. 7 is a diagram of the present application d Steering wheel angle simulation results comparison at=1.5m;
FIG. 8 is a diagram of the present application d Steering wheel angle simulation results comparison when=2m;
FIG. 9 is the diagram of the present application d Steering wheel angle simulation results at=2.5m are compared.
Detailed Description
In order to make the technical problems, technical solutions and advantages to be solved more apparent, the following detailed description will be given with reference to the accompanying drawings and specific embodiments. It will be apparent that the described embodiments are some, but not all, embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application. In addition, the technical features of the different embodiments of the present application described below may be combined with each other as long as they do not collide with each other.
For simplicity of explanation, the methodologies or rules are depicted and described as a series of acts, and are not intended to be exhaustive or limiting of the order of acts. For example, the experimental operations may be performed in various orders and/or concurrently, and include other experimental operations not described again. Furthermore, the described steps are not all necessary for the methods and algorithms described herein. Those skilled in the art will recognize and appreciate that the methodologies and algorithms can be represented by a state diagram or item as a series of interrelated states.
The embodiment of the application provides an improved pure tracking path tracking method, referring to fig. 2, a current vehicle position is taken as a circle center, a pre-aiming distance is taken as a radius to make a circle, and an intersection point between the pre-aiming distance and a front untracked path is taken as a pre-aiming point. After the pre-aiming point is determined, calculating the curvature of the expected path according to the geometric relationship, wherein the specific calculation formula is as follows:
where α is the chord tangent angle between the current heading of the vehicle and the intended circle of curvature, and R is the intended radius of curvature. And (3) finishing to obtain:
and because the curvature kappa=1/R, the pretightening curvature kappa and the pretightening distance l are pretighten d The relationship is as follows:
the controllable quantity of the current position of the vehicle is steering wheel turning angle, and the steering wheel turning angle can be converted into front wheel equivalent turning angle according to steering transmission ratio, so that the current steering wheel turning angle control quantity can be obtained by converting curvature into the front wheel equivalent turning angle, and the vehicle simplified kinematic model is combined to obtain:
where L is the vehicle wheelbase, t is each control period, where L d In the fixed case, for each α, the corresponding front wheel equivalent rotation angle δ (t) can be calculated, and the desired steering wheel rotation angle can be obtained.
After each control cycle obtains the steering wheel angle, the steps shown in fig. 1 are adopted for processing, specifically:
and (5) low-pass filtering. Besides the direct output of the steering wheel rotation angle of the first control period, the sampling value of each control period is weighted with the actual output value of the last control period, so that the output has feedback effect on the input, an effective filtering value is obtained, the weight of new data is reduced, the weight of the historical expected output rotation angle is increased, and the specific calculation formula is as follows:
θ pro(t) ＝θ output(t-1) ·β+θ e(t) ·(1-β)
wherein θ pro(t) For the current steering wheel angle to be processed, θ output(t-1) Steering wheel angle theta outputted for last control period e(t) And (3) outputting the expected steering wheel angle for the pure tracking algorithm of the current control period, namely directly calculating and outputting the steering wheel angle through alpha, wherein beta is a weight coefficient.
The number of turn signals to be counted. Calculating θ pro(t) And theta output(t-1) Difference theta of dif And comparing with a set threshold value, and updating the steering signal quantity when the threshold value is exceeded. The specific updating formula is as follows:
wherein up, down is the number of left (right) turn signals, and is initially 0; steerjspace is the set steering threshold.
And updating each state quantity. In order to avoid the situation that the traditional pure tracking algorithm frequently turns when tracking a path, the algorithm only turns when the number of signals to be turned exceeds a certain range and the difference value between the signals to be turned and the previous control period is larger than a certain step length, and the specific updating method is as follows:
when the up, down number is less than or equal to the set number control threshold value control_space, the steering wheel angle theta outputted in the last control period is still outputted output(t-1) As the current output.
When the number of up and down exceeds a set threshold, control_space is controlled to judge whether the vehicle needs to act. If theta is dif If the absolute value of (a) exceeds the set step control threshold step_space, then θ will be pro(t) As a vehicle current position steering control output; otherwise, the steering wheel angle theta of the last control period is still output output(t-1) 。
In the embodiment, low-pass filtering is set, the history expected steering angle is weighted, the smaller the filtering coefficient beta is, the more stable the filtering result is, but the sensitivity is reduced; setting a steering threshold value steer_space, and recording the steering quantity only when the absolute value of the difference value between the output rotation angle of the previous period and the current steering angle is larger than the threshold value; the steering step control_space is set, and the steering action is performed only when the difference is greater than a certain step. The parameters can be flexibly adjusted according to the actual use conditions, so that the effects of improving tracking precision and improving comfort are achieved.
By adopting the improved pure tracking path tracking method provided by the embodiment, the pretightening distance can be selected without limitation under the applicable working condition, and the difficult problem that a large number of experiments are required to select the proper pretightening distance or the pretightening distance is selected improperly according to experience is avoided. In the embodiment, the low-pass filtering and the multiple threshold constraint steering angle output are adopted, and the pretightening distances are respectively 1.5m, 2m and 2.5m under the applicable working conditions to carry out experiments. From the experimental results, the method improves the tracking precision, improves the riding comfort and meets the requirement of path tracking of the vehicle under the working condition of low speed and large curvature.
Specifically, the parameters selected in the above experiments are as follows:
table 1: parameter selection
| Parameters (parameters) | Value of | Parameters (parameters) | Value of |
| Wheelbase | 2.6m | α | 0.5° |
| Sampling interval | 0.05s | steer_space | 2.0° |
| Initial heading angle | 0° | control_space | 5 |
| Initial position | (-6,6) | step_space | 5.0° |
The tracking path is straight line and 1/4 circle, the radius of the circle is 6m, the curvature k=1/R=0.167, the reference track is shown in fig. 3, and the pretightening distance l is selected d The comparison between the conventional pure tracking algorithm (OPP) and the improved pure tracking path tracking method (IPP) provided in this embodiment is performed in terms of tracking accuracy and control stability, and the comparison results are shown in fig. 4 to 6.
From the drawingIt can be seen that the pretightening distance l d When the absolute values of the OPP tracking errors are 1.5m, 2m and 2.5m, the maximum values of the OPP tracking errors are 0.037m, 0.076m and 0.112m respectively, and the maximum values of the IPP tracking errors are 0.014m, 0.042m and 0.069m respectively. IPP improves tracking accuracy, and when the pretightening distance becomes large, the improvement effect is more obvious.
Fig. 7-9 show the comparison of the steering wheel angles output by the two tracking methods under different pretightening distances, and it can be seen from the figures that the IPP obviously reduces the steering wheel shake frequency and amplitude, and the larger the pretightening distance is, the more obvious the improvement effect is, and the technical effect of the method is achieved.
While the application has been described in detail in the foregoing general description and specific examples, it will be apparent to those skilled in the art that modifications and improvements can be made thereto. Accordingly, such modifications or improvements may be made without departing from the spirit of the application and are intended to be within the scope of the application as claimed.
Claims (3)
1. An improved pure tracking path tracking method is characterized by comprising the following steps:
firstly, taking the current vehicle position as a circle center, taking a pre-aiming distance as a radius to make a circle, determining a pre-aiming point at an intersection point of the pre-aiming distance and a front untracked path, calculating the curvature of the expected path according to a geometric relationship, and converting the curvature into a front wheel equivalent turning angle to obtain a steering wheel turning angle of each control period;
step two, low-pass filtering, namely, except for directly outputting steering wheel angles in a first control period, weighting a sampling value of the steering wheel angles in each control period with an actual output value in a last control period to obtain an effective filtering value;
the calculation formula of the low-pass filtering is as follows:
θ pro(t) ＝θ output(t-1) ·β+θ e(t) ·(1-β)
wherein θ pro(t) For the current steering wheel angle to be processed, θ output(t-1) Steering wheel angle, θ, for the last control period output e(t) The expected steering wheel rotation angle output by the pure tracking algorithm in the current control period is given, and beta is a weight coefficient;
step three, calculating the number of signals to be turned, calculating the difference between the current steering wheel angle to be processed and the steering wheel angle output in the previous control period, comparing the difference with a preset threshold value, and updating the number of the turning signals when the difference exceeds the threshold value;
the formula for updating the number of turn signals is:
wherein up, down is the number of left and right turn signals, and is initially 0; steerjspace is the set steering threshold;
and step four, updating the state quantity, wherein steering can be performed only when the number of signals to be steered exceeds a preset value and the difference between the signals to be steered and the previous control period is larger than a preset step length, and otherwise, the steering wheel rotation angle of the previous control period is still output.
2. The improved pure tracking path tracking method according to claim 1, wherein after the pretightening point is determined in the first step, pretightening distance l d The relationship between the current heading of the vehicle and the chord cut angle magnitude α of the expected curvature circle is:
wherein R is an expected curvature radius, and is obtained by arrangement:
and because the curvature kappa=1/R, the pretightening curvature kappa and the pretightening distance l are pretighten d The relationship is as follows:
combining with a simplified kinematic model of the vehicle, the method comprises the following steps of:
where L is the vehicle wheelbase, t is each control period, where L d Under the fixed condition, the corresponding front wheel equivalent rotation angle delta (t) can be calculated for each alpha, and then the steering wheel rotation angle in the control period is obtained.
3. The improved pure trace path tracing method according to claim 1, wherein the specific updating method of step four is as follows:
when the up, down number is less than or equal to the set number control threshold value control_space, the steering wheel angle theta outputted in the last control period is still outputted output(t-1) As a current output;
when the up and down numbers exceed a set threshold, judging whether the vehicle needs to act or not by controlling_space; if theta is dif If the absolute value of (a) exceeds the set step control threshold step_space, then θ will be pro(t) As a vehicle current position steering control output; otherwise, the steering wheel angle theta of the last control period is still output output(t-1) 。
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111630228.5A CN114355924B (en) | 2021-12-28 | 2021-12-28 | Improved pure tracking path tracking method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111630228.5A CN114355924B (en) | 2021-12-28 | 2021-12-28 | Improved pure tracking path tracking method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN114355924A CN114355924A (en) | 2022-04-15 |
| CN114355924B true CN114355924B (en) | 2023-10-13 |
Family
ID=81103610
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111630228.5A Active CN114355924B (en) | 2021-12-28 | 2021-12-28 | Improved pure tracking path tracking method |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114355924B (en) |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107153420A (en) * | 2017-05-25 | 2017-09-12 | 广州汽车集团股份有限公司 | Path tracking control method, device and intelligent automobile |
| WO2018072647A1 (en) * | 2016-10-19 | 2018-04-26 | 中车株洲电力机车研究所有限公司 | Method and system utilized by multi-axle articulated vehicle tracking central lane line |
| CN210011734U (en) * | 2019-04-10 | 2020-02-04 | 吉林大学 | Unmanned vehicle path tracking control device based on multi-point tracking |
| CN111731381A (en) * | 2020-06-30 | 2020-10-02 | 三一专用汽车有限责任公司 | Vehicle transverse self-adaptive control method and device and vehicle |
| CN112572436A (en) * | 2020-12-15 | 2021-03-30 | 北京理工大学 | Vehicle following control method and system |
| CN113204236A (en) * | 2021-04-14 | 2021-08-03 | 华中科技大学 | Intelligent agent path tracking control method |
| CN113311845A (en) * | 2021-07-29 | 2021-08-27 | 北京理工大学深圳汽车研究院(电动车辆国家工程实验室深圳研究院) | Pure tracking control error compensation method and device based on path curvature |
-
2021
- 2021-12-28 CN CN202111630228.5A patent/CN114355924B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2018072647A1 (en) * | 2016-10-19 | 2018-04-26 | 中车株洲电力机车研究所有限公司 | Method and system utilized by multi-axle articulated vehicle tracking central lane line |
| CN107153420A (en) * | 2017-05-25 | 2017-09-12 | 广州汽车集团股份有限公司 | Path tracking control method, device and intelligent automobile |
| CN210011734U (en) * | 2019-04-10 | 2020-02-04 | 吉林大学 | Unmanned vehicle path tracking control device based on multi-point tracking |
| CN111731381A (en) * | 2020-06-30 | 2020-10-02 | 三一专用汽车有限责任公司 | Vehicle transverse self-adaptive control method and device and vehicle |
| CN112572436A (en) * | 2020-12-15 | 2021-03-30 | 北京理工大学 | Vehicle following control method and system |
| CN113204236A (en) * | 2021-04-14 | 2021-08-03 | 华中科技大学 | Intelligent agent path tracking control method |
| CN113311845A (en) * | 2021-07-29 | 2021-08-27 | 北京理工大学深圳汽车研究院(电动车辆国家工程实验室深圳研究院) | Pure tracking control error compensation method and device based on path curvature |
Non-Patent Citations (1)
| Title |
|---|
| 段建民 等.基于Pure Pursuit算法的智能车路径跟踪.北京工业大学学报.2016,第42卷(第09期),1301-1306. * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN114355924A (en) | 2022-04-15 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN110001637B (en) | Unmanned vehicle path tracking control device and control method based on multipoint tracking | |
| WO2020187257A1 (en) | Vehicle abnormal lane change control method, device and system | |
| CN113126623B (en) | Adaptive dynamic sliding mode automatic driving vehicle path tracking control method considering input saturation | |
| CN108001447A (en) | A kind of intelligent vehicle path trace front wheel angle compensating control method | |
| CN110262229B (en) | Vehicle self-adaptive path tracking method based on MPC | |
| WO2021098663A1 (en) | Trajectory tracking method and system for four-wheel independent steering and independent drive vehicle | |
| CN111538328B (en) | Priority hierarchical prediction control method for obstacle avoidance trajectory planning and tracking control of autonomous driving vehicle | |
| CN111123701B (en) | Automatic driving path tracking anti-interference control method based on pipeline prediction model | |
| CN112109732A (en) | Intelligent driving self-adaptive curve pre-aiming method | |
| CN113183957A (en) | Vehicle control method, device and equipment and automatic driving vehicle | |
| CN110687797A (en) | Self-adaptive MPC parking transverse control method based on position and posture | |
| CN115489594A (en) | Pure-tracking intelligent vehicle path following control method | |
| CN114355924B (en) | Improved pure tracking path tracking method | |
| CN113212538B (en) | Method and terminal for autonomously correcting direction of remote-control unmanned vehicle | |
| CN111221338B (en) | Path tracking method, device, equipment and storage medium | |
| CN115534930A (en) | Vehicle transverse control method and device and electronic equipment | |
| CN114852085A (en) | Automatic vehicle driving track planning method based on road right invasion degree | |
| CN113190018B (en) | Intelligent agent path control method based on improved course error rate | |
| CN111026144B (en) | Air cushion landing boat control method based on stability augmentation controller | |
| CN113311698A (en) | Lane keeping control method, control device and vehicle | |
| CN111966103A (en) | Method, device, equipment and medium for dynamically correcting zero deflection angle of unmanned forklift | |
| CN112829760B (en) | Vehicle driving track prediction method and system | |
| CN113075930B (en) | Unmanned vehicle automatic steering control method and system based on event triggering | |
| CN116184808A (en) | Vehicle path tracking method and device, vehicle and storage medium | |
| CN116679592A (en) | Automatic driving vehicle control method and device based on MPC control |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |