CN112373463A

CN112373463A - Vehicle control method and system and vehicle

Info

Publication number: CN112373463A
Application number: CN202011285962.8A
Authority: CN
Inventors: 刘景湘; 郭天亮; 黄华军
Original assignee: Hunan Sany Intelligent Control Equipment Co Ltd
Current assignee: Hunan Sany Intelligent Control Equipment Co Ltd
Priority date: 2020-11-17
Filing date: 2020-11-17
Publication date: 2021-02-19
Anticipated expiration: 2040-11-17
Also published as: CN112373463B

Abstract

The invention provides a control method and a control system of a vehicle and the vehicle, wherein the control method of the vehicle comprises the following steps: acquiring an initial coordinate point, an initial course, a target coordinate point and a target course of a vehicle; acquiring the running parameters of the vehicle; determining a steering angle according to the initial course and the target course; generating a vehicle travelling track according to the starting coordinate point, the target coordinate point, the steering angle and the running parameter; controlling the vehicle to run along the vehicle running track; the operating parameters include, among other things, the minimum turn radius of the vehicle, the vehicle speed, and the time required to reach the minimum turn radius. According to the vehicle control method provided by the invention, in the process of moving the vehicle to the garage, manual participation is not needed, so that the position and the driving direction of the vehicle can be quickly adjusted according to the automatically generated vehicle advancing track, unnecessary starting and stopping actions are avoided, the overall energy consumption and the component abrasion of the vehicle are reduced, and the efficiency of moving the vehicle to the garage is improved.

Description

Vehicle control method and system and vehicle

Technical Field

The invention relates to the technical field of vehicle control, in particular to a vehicle control method, a vehicle control system and a vehicle.

Background

In the process of moving the vehicle to a garage or parking at a side position, the vehicle is often required to be started and stopped for multiple times and the direction of the vehicle is adjusted due to the limitation of the range of the field, the track of the vehicle which is controlled to advance is difficult to accurately control in the whole adjusting process, and the vehicle is further caused to generate extra energy consumption and abrasion.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art or the related art.

To this end, a first aspect of the invention provides a control method of a vehicle.

A second aspect of the invention provides a control system of a vehicle.

A third aspect of the invention provides a vehicle.

In view of this, a first aspect of the present invention provides a control method of a vehicle, including: acquiring an initial coordinate point, an initial course, a target coordinate point and a target course of a vehicle; acquiring the running parameters of the vehicle; determining a steering angle according to the initial course and the target course; generating a vehicle travelling track according to the starting coordinate point, the target coordinate point, the steering angle and the running parameter; controlling the vehicle to run along the vehicle running track; the operating parameters include, among other things, the minimum turn radius of the vehicle, the vehicle speed, and the time required to reach the minimum turn radius.

The invention provides a vehicle control method, which comprises the steps of firstly obtaining an initial coordinate point, an initial course, a target coordinate point and a target course of a vehicle. Operating parameters of the vehicle are then obtained, including a minimum turn radius of the vehicle, a vehicle speed, and a time required to reach the minimum turn radius. And determining a steering angle according to an included angle between the initial course and the target course. And calculating a vehicle travelling track according to the starting coordinate point, the target coordinate point, the steering angle and the vehicle running parameters, and finally controlling the vehicle to travel along the vehicle travelling track for garage transfer.

According to the vehicle control method provided by the invention, in the process of moving the vehicle to the garage, manual participation is not needed, so that the position and the driving direction of the vehicle can be quickly adjusted according to the automatically generated vehicle advancing track, unnecessary starting and stopping actions are avoided, the overall energy consumption and the component abrasion of the vehicle are reduced, and the efficiency of moving the vehicle to the garage is improved.

In addition, the control method of the vehicle in the above technical solution provided by the present invention may further have the following additional technical features:

in the above technical solution, further, the control method of a vehicle further includes: converting the initial coordinate point and the target coordinate point from a local map coordinate system to a relative coordinate system with the initial coordinate point as an origin and the target course as the positive direction of an x axis; and calculating to obtain the maximum turning angle which is turned when the vehicle turns from the initial coordinate point to reach the minimum turning radius according to the operation parameters.

In the technical scheme, before the vehicle advancing track is generated, the obtained initial coordinate point and the target coordinate point are converted into a relative coordinate system, the converted initial coordinate point is (0, 0) no matter which position the vehicle starts from, and the positive direction of the x axis of the relative coordinate system is the target course, so that the calculation in the subsequent vehicle advancing track generating process is simpler and more visual. When calculating the maximum turning angle, the minimum turning radius R of the vehicle is first obtained_minVehicle speed V and time T required to reach the minimum turning radius. In particular, time T is the ratio of the maximum angle of rotation of the steering wheel of the vehicle to the maximum angular speed of rotation of the steering wheel, the maximum angle of rotation being

According to the relationship between the steering angle and the maximum steering angle, different methods can be selected to generate the vehicle travel track.

In any of the above technical solutions, further, based on the situation that the steering angle is equal to 0, generating a vehicle travel track according to the start coordinate point, the target coordinate point, the steering angle, and the operation parameter includes: step 3002, setting the value of the track execution times i to 1; step 3004, setting a temporary displacement width, wherein the temporary displacement width is a ratio of a vertical coordinate of the target coordinate point in the relative coordinate system to i; step 3006, generating a first standard path with the start coordinate point as the start point and the end ordinate as the temporary displacement width according to the operation parameters in the relative coordinate system; step 3008, determining whether the abscissa of the end point of the first standard path is smaller than the abscissa of the target coordinate point, if so, performing step 3018, otherwise, performing step 3010; step 3010, generating a second standard path with the start coordinate point as a start point and the end ordinate as a temporary displacement width according to the operation parameters in the relative coordinate system; step 3012, determining whether the abscissa of the second standard path endpoint is smaller than the abscissa of the target coordinate point, if so, executing step 3018, otherwise, executing step 3014; step 3014, increase the value of i by 1; step 3016, determining whether i is greater than a first preset threshold, if not, executing step 3004, otherwise, ending generating the vehicle travel track; step 3018, executing the first standard path or the second standard path i times to obtain a vehicle traveling track; and based on the condition that the end point ordinate of the first standard path is the same as the end point ordinate of the second standard path, the end point abscissa of the second standard path is smaller than the end point abscissa of the first standard path.

In the technical scheme, when the vehicle traveling track is generated, two generation modes can be adopted, namely, a first standard path or a second standard path is generated firstly in the process of generating the vehicle traveling track. After the vehicle runs along the complete first standard path or the second standard path, the heading is consistent with the initial heading. In the process of generating the track, one of the first standard path and the second standard path can be selected according to the actual driving requirement. And when the end point ordinate of the first standard path is the same as that of the second standard path, the end point abscissa of the second standard path is smaller than that of the first standard path. For the same ordinate, selecting the second standard path may result in a shorter distance traveled by the vehicle, thereby reducing vehicle energy consumption, while selecting the first standard path may result in a reduction in pivot steering of the vehicle at the starting coordinate point, thereby reducing vehicle component wear.

Specifically, when the vehicle moves to a garage, if the steering angle is zero, it is indicated that the initial heading of the vehicle is consistent with the target heading, and the complete first standard path or the complete second standard path can be selected to generate the vehicle traveling track. First, the value of the number of times of executing the trajectory i is set to 1, and the temporary displacement width is set according to the ratio of the ordinate of the target coordinate point to the number of times of executing the trajectory. When the trajectory is generated, in order to reduce the wear of the vehicle component, a first standard path may be preferentially generated according to the start coordinate point, the temporary displacement width, and the operating parameter, and then it may be determined whether the abscissa of the end point of the first standard path is smaller than the abscissa of the target coordinate point. If the judgment result is yes, the first standard path does not exceed the boundary of the vehicle garage moving area, and at the moment, the first standard path is the vehicle traveling track. If the judgment result is negative, the situation that the vehicle can move out of the boundary of the vehicle garage moving area by adopting the first standard path is indicated, and a second standard path is selected and generated in order to reduce the displacement of the vehicle in the x-axis direction under the relative coordinate system.

And after a second standard path is generated according to the initial coordinate point, the temporary displacement width and the operation parameters, judging whether the abscissa of the end point of the second standard path is smaller than the abscissa of the target coordinate point. If the judgment result is yes, the second standard path does not exceed the boundary of the vehicle garage moving area, and at the moment, the second standard path is the vehicle traveling track. If the judgment result is negative, the fact that the vehicle can also exit the boundary of the vehicle garage moving area by adopting the second standard path is shown, and then the fact that the vehicle cannot finish garage moving through one-time starting and stopping under the current temporary displacement width is further shown. At this time, the temporary displacement width is halved, the number of times of executing the trajectory is increased to 2 correspondingly, the generation processes of the first standard path and the second standard path are repeated, a new first standard path or second standard path corresponding to the halved temporary displacement width is generated, and whether the abscissa of the end point of the new first standard path or second standard path is smaller than the abscissa of the target coordinate point is judged. And repeating the steps until a first standard path or a second standard path is found, the path end point of which does not exceed the vehicle garage moving area, and executing the first standard path or the second standard path for i times to obtain the vehicle traveling track.

In any of the above technical solutions, further, based on a situation that the steering angle is greater than 0 and less than or equal to the maximum turning angle, generating a vehicle travel track according to the start coordinate point, the target coordinate point, the steering angle, and the operation parameter includes: step 4002, under a relative coordinate system, acquiring a clothoid curve traveled by the vehicle from a straight start to a minimum turning radius according to the operation parameters by taking the starting coordinate point as a starting point, and acquiring a first correction point on the clothoid curve; step 4004, under a relative coordinate system, acquiring a circular curve with the minimum turning radius as the radius, a circle center abscissa of 0 and a circle center ordinate of the minimum turning radius, and acquiring a second correction point on the circular curve in the first quadrant; step 4006, setting the value of the first adjustment number j to 1; step 4008, setting a temporary correction width, wherein the temporary correction width is a ratio of a vertical coordinate of the target coordinate point in a relative coordinate system to j; step 4010, generating a first standard path with a starting coordinate point as a starting point and an end point ordinate as a sum of the temporary correction width and the ordinate of the first correction point according to the operation parameters in the relative coordinate system; step 4012, judging whether the difference between the abscissa of the first standard path end point and the abscissa of the first correction point is smaller than the abscissa of the target coordinate point, if so, executing step 4022, otherwise, executing step 4014; step 4014, generating a second standard path using the start coordinate point as a start point and the end ordinate as a sum of the temporary correction width and the ordinate of the second correction point according to the operation parameters in the relative coordinate system; step 4016, judging whether the difference between the abscissa of the second standard path end point and the abscissa of the second correction point is smaller than the abscissa of the target coordinate point, if so, executing step 4022, otherwise, executing step 4018; step 418, increasing the value of j by 1; step 4020, judging whether j is larger than a second preset threshold value, if not, executing step 4008, otherwise, ending generating the vehicle traveling track; step 4022, intercepting a path from the first correction point to a first standard path end point to obtain a first correction path, or intercepting a path from the second correction point to a second standard path end point to obtain a second correction path; step 4024, translating the first correction path or the second correction path to an origin of a relative coordinate system to obtain a vehicle travelling track; the tangent angle at the first correction point is equal to the steering angle, the tangent angle at the second correction point is equal to the steering angle, and the end-point abscissa of the second standard path is smaller than the end-point abscissa of the first standard path based on the condition that the end-point ordinate of the first standard path is the same as the end-point ordinate of the second standard path.

In the technical scheme, when the vehicle moves to a garage, if the steering angle is a positive value and is less than or equal to the maximum turning angle, when the vehicle traveling track is generated, a part of the first standard path or the second standard path needs to be intercepted so as to adjust the initial course of the vehicle to the target course.

Specifically, a clothoid curve which is traveled when the vehicle reaches the minimum turning radius from straight running is obtained by taking a starting coordinate point as a starting point according to the running parameters, a first correction point with a tangent angle equal to the steering angle is found on the clothoid curve, a circular curve with the radius of the minimum turning radius, a circle center abscissa of 0 and a circle center ordinate of the minimum turning radius is obtained, and a second correction point with the tangent angle equal to the steering angle is found on the circular curve. Setting the initial value of the first adjustment times j to be 1, and setting the temporary correction width according to the ratio of the ordinate of the target coordinate point to the first adjustment times.

In order to reduce wear of vehicle components when generating a vehicle travel track, a first standard route may be preferentially generated according to a start coordinate point, an operation parameter, and a sum of a temporary correction width and an ordinate of a first correction point, and then it may be determined whether a difference between an abscissa of an end point of the first standard route and an abscissa of the first correction point is smaller than an abscissa of a target coordinate point. If the judgment result is yes, the first standard path does not exceed the boundary of the vehicle garage moving area after being intercepted. If the judgment result is negative, the situation that the vehicle can exit the boundary of the vehicle garage moving area due to the fact that the first standard path is intercepted is indicated, potential safety hazards exist, and at the moment, a second standard path is selected and generated in order to reduce the displacement of the vehicle in the x-axis direction under the relative coordinate system.

And after a second standard path is generated according to the starting coordinate point, the running parameter and the sum of the temporary correction width and the ordinate of the second correction point, judging whether the abscissa of the end point of the second standard path and the abscissa of the second correction point are smaller than the abscissa of the target coordinate point. If the judgment result is yes, the second standard path is intercepted and does not exceed the boundary of the vehicle garage moving area. If the judgment result is negative, the vehicle can exit the boundary of the vehicle garage moving area by intercepting the second standard path. At this time, the first adjustment number is increased to 2, the temporary correction width is halved correspondingly, the generation processes of the first standard path and the second standard path are repeated, a new first standard path or a new second standard path corresponding to the halved temporary correction width is generated, and whether the cut new first standard path or the cut new second standard path exceeds the vehicle garage moving area is judged. And repeating the steps until a first standard path or a second standard path meeting the requirement is found, intercepting a path from the first correction point to the end point of the first standard path to obtain a first correction path or intercepting a path from the second correction point to the end point of the second standard path to obtain a second correction path, and translating the first correction path or the second correction path to the origin of the relative coordinate system.

And obtaining a first correction path or a second correction path under the condition that the value of the first adjustment times is 1, indicating that the vehicle can directly reach the target coordinate point after running along the translated first correction path or the translated second correction path, and adjusting the course to the target course, wherein the translated first correction path or the translated second correction path is the vehicle running track. If the first correction path or the second correction path is obtained under the condition that the value of the first adjustment times is larger than 1, the heading of the vehicle can be adjusted to the target heading after the vehicle runs along the first correction path or the second correction path after translation, but the vehicle does not reach the target coordinate point at the moment. In this case, the end point of the translated first correction path or second correction path may be used as a new start coordinate point, and a complete vehicle traveling track may be obtained by generating a vehicle traveling track when the steering angle is equal to 0 according to the new start coordinate point, the target coordinate point and the operation parameter, so as to control the vehicle to travel to the target coordinate point. In any of the above technical solutions, further, based on a situation that the steering angle is greater than or equal to a negative value of the maximum rotation angle and less than 0, generating a vehicle travel track according to the start coordinate point, the target coordinate point, the steering angle, and the operation parameter, includes: step 5002, under a relative coordinate system, taking the initial coordinate point as a starting point, obtaining a clothoid curve which the vehicle travels when the vehicle reaches the minimum turning radius from a straight line according to the operation parameters, and obtaining a third correction point on the clothoid curve, wherein a tangent angle at the third correction point is equal to an absolute value of a steering angle; step 5004, setting the value of the second adjustment time k to 1; step 5006, setting a first intermediate coordinate point, wherein an abscissa of the first intermediate coordinate point is an abscissa of the target coordinate point in the relative coordinate system, and an ordinate of the first intermediate coordinate point is a ratio of an ordinate of the target coordinate point in the relative coordinate system to k; step 5008, rotating the absolute value of the steering angle counterclockwise by taking the origin of the relative coordinate system as the center of the first intermediate coordinate point to obtain a second intermediate coordinate point; step 5010, generating a first standard path with the initial coordinate point as a starting point and the end point ordinate as the sum of the third correction point and the second intermediate coordinate point according to the operation parameters in a relative coordinate system; step 5012, judging whether the difference between the abscissa of the first standard path end point and the abscissa of the third correction point is smaller than the abscissa of the second middle coordinate point, if so, executing step 5018, otherwise, executing step 5014; step 5014, increasing the value of k by 1; step 5016, judging whether k is larger than a third preset threshold, if not, executing step 5006, otherwise, ending generation of the vehicle travelling track; step 5018, intercepting a path from the starting point of the first standard path to a point where the ordinate of the first standard path is equal to the ordinate of the second middle coordinate point to obtain a third correction path; step 5020, translating the third correction path in the positive direction of the x axis to enable the abscissa of the end point of the third correction path to be the same as the abscissa of the second middle coordinate point; step 5022, a splicing straight line is arranged between the starting point of the third correction path and the origin of the relative coordinate system, and a fourth correction path is obtained; step 5024, rotating the absolute value of the steering angle clockwise by taking the origin of the relative coordinate system as the center of the fourth correction path to obtain a vehicle advancing track; wherein the tangent angle at the third correction point is equal to the absolute value of the steering angle.

In the technical scheme, when the vehicle moves to a garage, if the steering angle is a negative value and the absolute value of the steering angle is less than or equal to the maximum turning angle, when the vehicle traveling track is generated, a part of track of the first standard path needs to be intercepted, translated and rotated so as to adjust the initial course of the vehicle to the target course.

Specifically, a clothoid curve which the vehicle travels when reaching the minimum turning radius from a straight-ahead start is obtained according to the operation parameters by taking the start coordinate point as a starting point, and a third correction point at which the tangent angle is equal to the absolute value of the steering angle is found on the clothoid curve. And then setting the value of the second adjustment frequency k as 1, setting a first intermediate coordinate point according to the abscissa of the target coordinate point and the ratio of the ordinate of the target coordinate point to the second adjustment frequency, and rotating the absolute value of the steering angle anticlockwise by taking the original point of the first intermediate coordinate point as the center to obtain a second intermediate coordinate point. And generating a first standard path according to the starting coordinate point, the operating parameter and the sum of the ordinate of the third correction point and the ordinate of the second intermediate coordinate point, and then judging whether the difference between the abscissa of the end point of the first standard path and the abscissa of the third correction point is smaller than the abscissa of the second intermediate coordinate point. If the judgment result is yes, the first standard path is intercepted and does not exceed the boundary of the vehicle garage moving area. If the judgment result is negative, the situation that the vehicle can exit the boundary of the vehicle garage moving area by intercepting the first standard path is explained, and potential safety hazards exist.

At this time, the second adjustment frequency is increased to 2, correspondingly, the vertical coordinate of the first intermediate coordinate point is halved, the generation process of the first standard path is repeated, a new first standard path corresponding to the sum of the new second intermediate coordinate point and the vertical coordinate of the third correction point is generated, and whether the intercepted new first standard path exceeds the boundary of the vehicle garage shifting area or not is judged. And repeating the steps until a first standard path meeting the requirement is found, and intercepting a path from the starting point of the first standard path to a point on the first standard path, wherein the ordinate of the point is equal to the ordinate of the second middle coordinate point, so as to obtain a third correction path. And translating the third correction path along the positive direction of the x axis, enabling the abscissa of the end point of the third correction path to be the same as the abscissa of the second middle coordinate point, setting a splicing straight line between the starting point and the origin point of the third correction path to obtain a fourth correction path, and finally, rotating the fourth correction path clockwise to the absolute value of the steering angle.

And obtaining a fourth correction path under the condition that the value of the second adjustment times is 1, and indicating that the vehicle can directly reach the target coordinate point after running along the rotated fourth correction path, and adjusting the course to the target course, wherein the rotated fourth correction path is the vehicle running track. If the fourth corrected path is obtained under the condition that the value of the second adjustment times is greater than 1, the heading of the vehicle can be adjusted to the target heading after the vehicle runs along the rotated fourth corrected path, but the vehicle does not reach the target coordinate point at the moment. In this case, the end point of the rotated fourth correction path may be used as a new start coordinate point, and a complete vehicle traveling track may be obtained by continuing to generate the vehicle traveling track when the steering angle is equal to 0 according to the new start coordinate point, the target coordinate point and the operation parameter, so as to control the vehicle to travel to the target coordinate point.

In any of the above technical solutions, further, the first standard path includes: a first curved track, the angle of the first curved track is greater than 0 degree and less than or equal to 90 degrees; and the second curve track is connected with the first curve track, and the second curve track and the first curve track are centrosymmetric about the connection point of the first curve track and the second curve track.

In an aspect, the first standard path includes a first curvilinear track and a second curvilinear track. The second curve track is connected with the first curve track, the first curve track and the second curve track are centrosymmetric about a connection position, so that tangents of a starting position and an end position of the first preset track are parallel, the first standard path with symmetric design is adopted, the calculation amount for generating the first standard path can be reduced, the complete first standard path can be obtained as long as the first curve track is obtained, and the generation difficulty of the first standard path is effectively reduced.

The angle of the first curve track is greater than 0 degree and less than or equal to 90 degrees, and various driving requirements can be met under the relative position relation of various initial coordinate points and target coordinate points.

In any of the above technical solutions, based on a case where the first curved track rotates by an angle greater than 0 degree and less than or equal to 2 times the maximum rotation angle, the first curved track includes: the terminal point of the first backspin track is connected with the starting point of the second backspin track, and the curvature of the terminal point of the first backspin track is the same as that of the starting point of the second backspin track; based on the first curve track turning through an angle greater than 2 times the maximum rotation angle and less than or equal to 90 degrees, the first curve track includes: the terminal point of the third circular track is connected with the starting point of the first circular track, the terminal point curvature of the third circular track is the same as the starting point curvature of the first circular track, the terminal point curvature of the first circular track is connected with the starting point of the fourth circular track, and the terminal point curvature of the first circular track is the same as the starting point curvature of the fourth circular track.

In this embodiment, the first curve path is rotated by an angle θ₁Greater than 0 degrees and less than or equal to 2 alpha, indicating that the vehicle need not turn the steering wheel to the maximum during travel along the first curved path. At this time, the first curved track includes a first convolution track and a second convolution track, where the first convolution track and the second convolution track rotate by the same angle, and the lengths of the first convolution track and the second convolution track are the same. The curvature of the starting point position of the first revolution trajectory is 0, the curvature of the first revolution trajectory is gradually increased from the starting point position to the end point position, the end point of the first revolution trajectory is connected with the starting point of the second revolution trajectory, the curvature of the end point position of the second revolution trajectory is 0, and the curvature of the second revolution trajectory is gradually decreased from the starting point position to the end point position.

Angle theta if the first curve track turns₁Greater than 2 α indicates that the vehicle is required to steer the vehicle during travel along the first curved pathThe rotation angle is turned to the maximum. At this time, the first curved track includes a third clothoid track, a first circular arc track, and a fourth clothoid track. The rotating angles of the third rotating track and the fourth rotating track are both the maximum rotating angle alpha, the curvature of the starting point position of the third rotating track is 0, and the curvature of the end point position of the third rotating track is 1/R_minThe end point of the third convolution track is connected to the start point of the first circular arc track, and the angle of the first circular arc track is theta ₁2 alpha, the curvature of the first circular arc track is 1/R from the starting position to the end position_minThe end point of the first circular arc track is connected with the starting point of the fourth circular arc track, and the curvature of the starting point of the fourth circular arc track is 1/R_minThe curvature of the end position of the fourth clothoid locus is 0.

The curvature of the starting point of the first curve track generated by the method is 0, so that the vehicle does not need to rotate a steering wheel in situ before driving away from the starting coordinate point, the loss of vehicle parts is reduced, the curvature of the position of the first curve track from the starting point of the track to the terminal point of the track is continuous, the tracking of the vehicle is facilitated, and the vehicle abrasion caused by the fact that the vehicle needs to be stopped in situ to adjust the direction due to sudden change of the advancing direction in the driving process is further reduced.

In any of the above technical solutions, further, the second standard path includes: a third curved track, the angle of the third curved track is greater than 0 degree and less than or equal to 90 degrees; and the fourth curve track is connected with the third curve track, and the fourth curve track and the third curve track are centrosymmetric about the connecting point of the third curve track and the fourth curve track.

In this solution, the second standard path includes a third curved trajectory and a fourth curved trajectory. The third curve track is connected with the fourth curve track, the third curve track and the fourth curve track are centrosymmetric about a connection position, so that tangents of the starting position and the ending position of the second standard path are parallel, the second standard path with the symmetric design is adopted, the calculation amount for generating the second standard path can be reduced, the complete second standard path can be obtained as long as the third curve track is obtained, and the generation difficulty of the second standard path is effectively reduced.

The angle of the third curve track is greater than 0 degree and less than or equal to 90 degrees, and the driving requirements under different working conditions can be met under the relative position relationship between various initial coordinate points and target coordinate points.

In any of the above solutions, further, the third curved track includes: a second circular arc trajectory; and the starting point of the fifth circular track is connected with the end point of the second circular arc track, and the curvature of the end point of the second circular arc track is the same as that of the starting point of the fifth circular track.

In this technical solution, the third curved trajectory includes a second circular arc trajectory and a fifth clothoid trajectory. Wherein the fifth turning track turns by the angle that the vehicle turns from the initial coordinate point to the minimum turning radius R_minThe maximum rotation angle alpha of the second arc track is equal to the rotation angle theta of the third curve track₃Minus the maximum rotation angle alpha. The curvature of the second circular arc track is 1/R from the starting position to the end position_minThe end point of the second circular arc track is connected with the start point of the fifth circular track, and the curvature of the position of the start point of the fifth circular track is 1/R_minThe curvature of the end position of the fifth clothoid trace is 0.

The curvature of the starting point of the third curve track generated in the above way is 1/R_minThe vehicle can drive away from the initial coordinate point by the minimum turning radius, so that the aims of quickly steering and shortening the overall track length are fulfilled. And the curvature of the third curve track from the track starting point to the track end point is continuous, which is beneficial to the tracking of the vehicle, and the vehicle does not need to stop midway to adjust the direction in situ in the process of running along the third curve track, thereby reducing the abrasion of vehicle parts.

A second aspect of the invention provides a control system for a vehicle, comprising a memory configured and adapted to store a computer program; a processor configured to be adapted to execute a computer program to implement the control method of the vehicle as provided in any of the above claims.

In this aspect, the control system of the vehicle includes a memory and a processor, and implements the control method of the vehicle as provided in any one of the above aspects, and therefore, the control system of the vehicle includes all the advantageous effects of the control method of the vehicle as provided in any one of the above aspects.

Specifically, in the process of moving the vehicle to the garage, manual participation is not needed, so that the position and the running direction of the vehicle can be quickly adjusted according to the automatically generated vehicle running track, unnecessary starting and stopping actions are avoided, the overall energy consumption and the component abrasion of the vehicle are reduced, and the efficiency of moving the vehicle to the garage is improved.

A third aspect of the invention provides a vehicle comprising: a vehicle body; a traveling mechanism provided on the vehicle body; in the control system of the vehicle according to the above-described aspect, the control system of the vehicle is electrically connected to the travel mechanism, and the control system of the vehicle is configured to control the travel mechanism.

The vehicle provided by the invention comprises the vehicle body, the traveling mechanism and the control system of the vehicle in the technical scheme, so that the vehicle has all the beneficial effects of the control system of the vehicle provided in the technical scheme, and the description is omitted.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

fig. 1 shows a flowchart of a control method of a vehicle of one embodiment of the invention;

fig. 2 shows a flowchart of a control method of a vehicle of another embodiment of the invention;

FIG. 3 shows a schematic diagram of a first standard path and a second standard path of one embodiment of the present invention;

fig. 4 shows a flowchart of a control method of a vehicle of a further embodiment of the invention;

FIG. 5 is a schematic diagram illustrating a vehicle travel path for a vehicle to make a garage shift when the steering angle is positive in one embodiment of the present invention;

fig. 6 shows a flowchart of a control method of a vehicle of still another embodiment of the invention;

FIG. 7 is a schematic diagram illustrating a vehicle travel path for a vehicle to make a garage shift when the steering angle is negative in one embodiment of the present invention;

fig. 8 shows a flowchart of a control method of a vehicle of a further embodiment of the invention;

FIG. 9 is a schematic illustration of vehicle parking paths for parallel parking of vehicles in accordance with an embodiment of the present invention;

FIG. 10 shows a schematic view of a first curvilinear path of an embodiment of the present invention;

FIG. 11 shows a schematic view of another first curvilinear path of an embodiment of the present invention;

FIG. 12 shows a schematic view of a third curvilinear path of an embodiment of the present invention;

FIG. 13 shows a schematic block diagram of a control system of a vehicle of one embodiment of the invention;

FIG. 14 is a flow chart illustrating a vehicle garage transfer according to an embodiment of the present invention;

fig. 15 shows a flow chart for parallel parking of a vehicle according to an embodiment of the present invention.

Detailed Description

In order that the above objects, features and advantages of the present invention can be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings. It should be noted that the embodiments and features of the embodiments of the present application may be combined with each other without conflict.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described herein, and therefore the scope of the present invention is not limited by the specific embodiments disclosed below.

A control method, a control system, and a vehicle of a vehicle according to some embodiments of the invention are described below with reference to fig. 1 to 15.

The first embodiment is as follows:

as shown in fig. 1, in one embodiment of the present invention, there is provided a control method of a vehicle, including:

s102, acquiring an initial coordinate point, an initial course, a target coordinate point and a target course of the vehicle;

s104, acquiring the running parameters of the vehicle;

s106, determining a steering angle according to the initial course and the target course;

s108, generating a vehicle travelling track according to the starting coordinate point, the target coordinate point, the steering angle and the running parameters;

and S110, controlling the vehicle to run along the vehicle running track.

The operating parameters include, among other things, the minimum turn radius of the vehicle, the vehicle speed, and the time required to reach the minimum turn radius.

The control method of the vehicle provided by the embodiment firstly obtains the initial coordinate point, the initial course, the target coordinate point and the target course of the vehicle. Operating parameters of the vehicle are then obtained, including a minimum turn radius of the vehicle, a vehicle speed, and a time required to reach the minimum turn radius. And determining a steering angle according to an included angle between the initial course and the target course. And calculating a vehicle travelling track according to the starting coordinate point, the target coordinate point, the steering angle and the vehicle running parameters, and finally controlling the vehicle to travel along the vehicle travelling track for garage transfer.

According to the control method of the vehicle, in the process of moving the vehicle to the garage, manual participation is not needed, so that the position and the running direction of the vehicle can be quickly adjusted according to the automatically generated vehicle running track, unnecessary starting and stopping actions are avoided, the overall energy consumption and the component abrasion of the vehicle are reduced, and the efficiency of moving the vehicle to the garage is improved.

Example two:

as shown in fig. 2, in one embodiment of the present invention, there is provided a control method of a vehicle, including:

s202, acquiring an initial coordinate point, an initial course, a target coordinate point and a target course of the vehicle;

s204, acquiring the running parameters of the vehicle;

s206, determining a steering angle according to the initial course and the target course;

s208, converting the initial coordinate point and the target coordinate point from the local map coordinate system to a relative coordinate system which takes the initial coordinate point as an origin and the target course as the positive direction of the x axis;

s210, setting the value of the track execution times i as 1;

s212, setting a temporary displacement width, wherein the temporary displacement width is the ratio of the ordinate of the target coordinate point in the relative coordinate system to the i;

s214, generating a first standard path with a starting coordinate point as a starting point and an end point ordinate as a temporary displacement width according to the operation parameters in a relative coordinate system;

s216, judging whether the abscissa of the end point of the first standard path is smaller than the abscissa of the target coordinate point, if so, executing S226, otherwise, executing S218;

s218, generating a second standard path with a starting coordinate point as a starting point and an end point ordinate as a temporary displacement width according to the operation parameters in a relative coordinate system;

s220, judging whether the abscissa of the second standard path end point is smaller than the abscissa of the target coordinate point, if so, executing S226, otherwise, executing S222;

s222, increasing the value of i by 1;

s224, judging whether i is larger than a first preset threshold value, if not, executing S212, otherwise, ending;

s226, executing the first standard path or the second standard path for i times to obtain a vehicle traveling track;

and S228, controlling the vehicle to run along the vehicle running track.

In this embodiment, as shown in fig. 3, when the vehicle travel track is generated, two generation methods may be adopted, that is, the first standard path or the second standard path is generated in the process of generating the vehicle travel track. After the vehicle runs along the complete first standard path or the second standard path, the heading is consistent with the initial heading. In the process of generating the track, one of the first standard path and the second standard path can be selected according to the actual driving requirement. And when the end point ordinate of the first standard path is the same as that of the second standard path, the end point abscissa of the second standard path is smaller than that of the first standard path. For the same ordinate, selecting the second standard path may result in a shorter distance traveled by the vehicle, thereby reducing vehicle energy consumption, while selecting the first standard path may result in a reduction in pivot steering of the vehicle at the starting coordinate point, thereby reducing vehicle component wear.

Furthermore, before the vehicle travelling track is generated, the obtained initial coordinate point and the target coordinate point are converted into a relative coordinate system, the converted initial coordinate point is (0, 0) no matter where the vehicle starts from, and the positive direction of the x axis of the relative coordinate system is the target heading, so that the calculation in the subsequent vehicle travelling track generation process is simpler and more intuitive.

In the embodiment, the steering angle of the vehicle during garage moving is zero, the initial heading of the vehicle is consistent with the target heading, and the complete first standard path or the complete second standard path can be selected to generate the vehicle traveling track. First, the value of the number of times of executing the trajectory i is set to 1, and the temporary displacement width is set according to the ratio of the ordinate of the target coordinate point to the number of times of executing the trajectory. When the trajectory is generated, in order to reduce the wear of the vehicle component, a first standard path may be preferentially generated according to the start coordinate point, the temporary displacement width, and the operating parameter, and then it may be determined whether the abscissa of the end point of the first standard path is smaller than the abscissa of the target coordinate point. If the judgment result is yes, the first standard path does not exceed the boundary of the vehicle garage moving area, and at the moment, the first standard path is the vehicle traveling track. If the judgment result is negative, the situation that the vehicle can move out of the boundary of the vehicle garage moving area by adopting the first standard path is indicated, and a second standard path is selected and generated in order to reduce the displacement of the vehicle in the x-axis direction under the relative coordinate system.

Example three:

as shown in fig. 4, in one embodiment of the present invention, there is provided a control method of a vehicle, including:

s402, acquiring an initial coordinate point, an initial course, a target coordinate point and a target course of the vehicle;

s404, acquiring the running parameters of the vehicle;

s406, determining a steering angle according to the initial course and the target course;

s408, converting the initial coordinate point and the target coordinate point from the local map coordinate system to a relative coordinate system with the initial coordinate point as an origin and the target course as the positive direction of the x axis;

s410, calculating according to the operation parameters to obtain a maximum turning angle which is turned when the vehicle turns from the initial coordinate point to reach the minimum turning radius;

s412, based on the situation that the steering angle is larger than 0 and smaller than or equal to the maximum steering angle, under a relative coordinate system, by taking the initial coordinate point as a starting point, acquiring a clothoid curve which the vehicle runs when the vehicle reaches the minimum turning radius from a straight start according to the operation parameters, and acquiring a first correction point on the clothoid curve;

s414, under a relative coordinate system, acquiring a circular curve with the minimum turning radius as the radius, the circle center abscissa as 0 and the circle center ordinate as the minimum turning radius, and acquiring a second correction point on the circular curve in the first quadrant;

s416, setting the value of the first adjusting times j to be 1;

s418, setting a temporary correction width, wherein the temporary correction width is the ratio of the ordinate of the target coordinate point in the relative coordinate system to j;

s420, generating a first standard path with a starting coordinate point as a starting point and an end point ordinate as the sum of the temporary correction width and the ordinate of the first correction point according to the operation parameters in a relative coordinate system;

s422, judging whether the difference between the abscissa of the first standard path end point and the abscissa of the first correction point is smaller than the abscissa of the target coordinate point, if so, executing S432, otherwise, executing S424;

s424, generating a second standard path with the initial coordinate point as a starting point and the end point ordinate as the sum of the temporary correction width and the ordinate of the second correction point according to the operation parameters in the relative coordinate system;

s426, judging whether the difference between the abscissa of the second standard path end point and the abscissa of the second correction point is smaller than the abscissa of the target coordinate point, if so, executing S432, otherwise, executing S428;

s428, increasing the value of j by 1;

s430, judging whether j is larger than a second preset threshold value, if not, executing S418, otherwise, ending;

s432, intercepting a path from the first correction point to a first standard path end point to obtain a first correction path, or intercepting a path from the second correction point to a second standard path end point to obtain a second correction path;

s434, translating the first correction path or the second correction path to the origin of the relative coordinate system to obtain a vehicle advancing track;

and S436, controlling the vehicle to run along the vehicle running track.

The tangent angle at the first correction point is equal to the steering angle, the tangent angle at the second correction point is equal to the steering angle, and the end-point abscissa of the second standard path is smaller than the end-point abscissa of the first standard path based on the condition that the end-point ordinate of the first standard path is the same as the end-point ordinate of the second standard path.

In this embodiment, in calculating the maximum turning angle, the minimum turning radius R of the vehicle is first acquired_minVehicle speed V and time T required to reach the minimum turning radius. In particular, time T is the ratio of the maximum angle of rotation of the steering wheel of the vehicle to the maximum angular speed of rotation of the steering wheel, the maximum angle of rotation being

In this embodiment, the steering angle of the vehicle during garage moving is greater than 0 and less than or equal to the maximum turning angle, and when the vehicle travel track is generated, a part of the first standard path or the second standard path needs to be intercepted to adjust the initial heading of the vehicle to the target heading.

And obtaining a first correction path or a second correction path under the condition that the value of the first adjustment times is 1, indicating that the vehicle can directly reach the target coordinate point after running along the translated first correction path or the translated second correction path, and adjusting the course to the target course, wherein the translated first correction path or the translated second correction path is the vehicle running track. If the first correction path or the second correction path is obtained under the condition that the value of the first adjustment times is larger than 1, the heading of the vehicle can be adjusted to the target heading after the vehicle runs along the first correction path or the second correction path after translation, but the vehicle does not reach the target coordinate point at the moment. In this case, the end point of the translated first correction path or second correction path may be used as a new start coordinate point, and a complete vehicle traveling track may be obtained by generating a vehicle traveling track when the steering angle is equal to 0 according to the new start coordinate point, the target coordinate point and the operation parameter, so as to control the vehicle to travel to the target coordinate point.

In the specific embodiment, as shown in fig. 5, the vehicle 100 may drive to the left front by starting and stopping for the first time, so that the heading is adjusted to the target heading, and then drive to the target coordinate point by starting and stopping four times by the vehicle control method in the second embodiment.

Example four:

as shown in fig. 6, in one embodiment of the present invention, there is provided a control method of a vehicle, including:

s602, acquiring an initial coordinate point, an initial course, a target coordinate point and a target course of the vehicle;

s604, acquiring the running parameters of the vehicle;

s606, determining a steering angle according to the initial course and the target course;

s608, converting the initial coordinate point and the target coordinate point from the local map coordinate system to a relative coordinate system with the initial coordinate point as an origin and the target course as the positive direction of the x axis;

s610, calculating according to the operation parameters to obtain a maximum turning angle which is turned when the vehicle turns from the initial coordinate point to reach the minimum turning radius;

s612, based on the situation that the steering angle is smaller than 0 and the absolute value of the steering angle is smaller than or equal to the maximum turning angle, under a relative coordinate system, the initial coordinate point is taken as the starting point, a clothoid curve which the vehicle runs when the vehicle starts to reach the minimum turning radius from the straight running is obtained according to the operation parameters, and a third correction point is obtained on the clothoid curve;

s614, setting the value of the second adjustment times k as 1;

s616, setting a first intermediate coordinate point, wherein the abscissa of the first intermediate coordinate point is the abscissa of the target coordinate point in the relative coordinate system, and the ordinate of the first intermediate coordinate point is the ratio of the ordinate of the target coordinate point in the relative coordinate system to k;

s618, rotating the absolute value of the steering angle anticlockwise by taking the origin of the relative coordinate system as the center of the first intermediate coordinate point to obtain a second intermediate coordinate point;

s620, generating a first standard path with the starting coordinate point as a starting point and the end point ordinate as the sum of the third correction point and the second intermediate coordinate point according to the operation parameters in the relative coordinate system;

s622, determining whether a difference between the abscissa of the first standard path end point and the abscissa of the third correction point is smaller than the abscissa of the second intermediate coordinate point, if so, performing S628, otherwise, performing S624;

s624, increasing the value of k by 1;

s626, judging whether k is larger than a third preset threshold value, if not, executing S616, otherwise, ending;

s628, intercepting a path from the starting point of the first standard path to a point where the ordinate of the first standard path is equal to the ordinate of the second intermediate coordinate point to obtain a third correction path;

s630, translating the third correction path along the positive direction of the x axis, so that the abscissa of the end point of the third correction path is the same as the abscissa of the second middle coordinate point;

s632, arranging a splicing straight line between the starting point of the third correction path and the origin of the relative coordinate system to obtain a fourth correction path;

s634, rotating the absolute value of the steering angle clockwise by taking the origin of the relative coordinate system as the center of the fourth correction path to obtain the vehicle advancing track;

and S636, controlling the vehicle to run along the vehicle running track.

Wherein the tangent angle at the third correction point is equal to the absolute value of the steering angle.

In this embodiment, the steering angle of the vehicle during garage moving is less than 0, and the absolute value of the steering angle is less than or equal to the maximum rotation angle, and when the vehicle travel track is generated, a part of the track of the first standard path needs to be intercepted, translated and rotated, so as to adjust the initial heading of the vehicle to the target heading.

In the specific embodiment, as shown in fig. 7, the vehicle 100 may drive to the right front by starting and stopping for the first time, so that the heading is adjusted to the target heading, and then drive to the target coordinate point by starting and stopping four times by the vehicle control method in the second embodiment.

Example five:

as shown in fig. 8, in one embodiment of the present invention, there is provided a control method of a vehicle for parallel parking of the vehicle, the control method including:

s802, acquiring parking space parameters of a vehicle, size parameters of the vehicle and operation parameters of the vehicle;

s804, determining a target coordinate point according to the parking space parameter and the size parameter of the vehicle;

s806, setting a vertical coordinate of a temporary parking starting point;

s808, generating a first standard path with a starting point ordinate as a temporary parking starting point ordinate and a target coordinate point as an end point according to the operation parameters;

s810, judging whether the vehicle collides with the boundary of the parking space according to the first standard path and the size parameter of the vehicle, if so, executing S812, otherwise, executing S820;

s812, generating a second standard path with a starting point ordinate as a temporary parking starting point ordinate and a target coordinate point as an end point according to the operation parameters;

s814, judging whether the vehicle collides with the boundary of the parking space according to the second standard path and the size parameter of the vehicle, if so, executing S816, otherwise, executing S820;

s816, increasing a preset value to the vertical coordinate of the temporary parking starting point;

s818, judging whether the vertical coordinate of the temporary parking starting point is larger than a fourth preset threshold value, if not, executing S808, otherwise, ending;

s820, taking the first standard path or the second standard path as a vehicle parking path;

and S822, controlling the vehicle to run along the parking path of the vehicle.

The parking space parameters comprise boundary coordinates of the parking space and width of the parking space, and the size parameters of the vehicle comprise width of the vehicle body.

In this embodiment, as shown in fig. 9, when the vehicle 100 performs parallel parking, the steering angle is zero, and in the process of generating a vehicle parking path, whether to adjust the vertical coordinate of the temporary parking starting point is determined according to whether the vehicle collides with the boundary of the parking space 120, so as to generate a new vehicle parking path, thereby ensuring that the vehicle 100 can complete parallel parking through one start and stop, and reducing the energy consumption and the component wear of the vehicle 100.

Specifically, the parking space parameter and the size parameter of the vehicle are firstly acquired, and when the parking path of the vehicle is generated, in order to reduce the abrasion of vehicle parts, the first standard path can be preferentially generated according to the target coordinate point, the vertical coordinate of the temporary parking starting point and the operation parameter. And judging whether the vehicle collides with the parking space according to the first standard path, the size parameter and the parking space parameter generated by calculation, if not, taking the first standard path as a vehicle advancing track, if so, generating a second standard path according to the target coordinate point, the temporary parking starting point ordinate and the operation parameter, and if so, judging that the vehicle collides along the second standard path generated by calculation, which indicates that the vehicle cannot reach the target coordinate point by starting and stopping once. At this time, the temporary parking starting point ordinate needs to be increased by a preset value, the process of generating the first standard path or the second standard path is repeated according to the new temporary parking starting point ordinate until the vehicle does not collide with the parking space when running along the first standard path or the second standard path generated by calculation, and finally the first standard path or the second standard path generated by calculation is used as the vehicle parking path.

Further, the initially set temporary parking start point ordinate may be half of the sum of the parking space width and the vehicle body width. The smaller the set preset value is, the smaller the interval between the first parking path or the second parking path generated by each calculation is, so that the vertical coordinate of the starting point of the parallel parking of the vehicle is as close to the vertical coordinate of the initial temporary parking starting point as possible, the traveling distance of the vehicle is reduced, the energy consumption and the abrasion of the vehicle are further reduced, and the larger the set preset value is, the more favorable the rapid calculation of the vehicle parking path is, and the calculation efficiency of the vehicle parking path is improved. Specifically, the preset value can be 0.2, 0.5, 1, and the like, and the user can flexibly select the preset value according to the parallel parking requirement.

Example six:

in any of the above embodiments, further, as shown in fig. 3, the first standard path includes: a first curvilinear path and a second curvilinear path.

As shown in fig. 3, the second curve track is connected to the first curve track, and the first curve track and the second curve track are centrosymmetric with respect to the connection point, so as to ensure that the tangents of the start position and the end position of the first standard path are parallel, and by adopting the first standard path with symmetric design, the calculation amount for generating the first standard path can be reduced, and the complete first standard path can be obtained as long as the first curve track is obtained, thereby effectively reducing the generation difficulty of the first standard path.

Further, the first curved track includes, based on the first curved track turning through an angle greater than 0 degrees and less than or equal to 2 times the maximum rotation angle: a first clothoid trajectory and a second clothoid trajectory. Based on the first curve track turning through an angle greater than 2 times the maximum rotation angle and less than or equal to 90 degrees, the first curve track includes: a third clothoid trajectory, a first circular arc trajectory and a fourth clothoid trajectory.

Specifically, as shown in FIG. 10, the first curved path rotates through an angle θ₁Greater than 0 degrees and less than or equal to 2 alpha, indicating that the vehicle need not turn the steering wheel to the maximum during travel along the first curved path. At this time, the first curved track includes a first convolution track and a second convolution track, where the first convolution track and the second convolution track rotate by the same angle, and the lengths of the first convolution track and the second convolution track are the same. The curvature of the starting point position of the first revolution trajectory is 0, the curvature of the first revolution trajectory is gradually increased from the starting point position to the end point position, the end point of the first revolution trajectory is connected with the starting point of the second revolution trajectory, the curvature of the end point position of the second revolution trajectory is 0, and the curvature of the second revolution trajectory is gradually decreased from the starting point position to the end point position.

As shown in FIG. 11, the first curved path rotates by an angle θ₁Greater than 2 α indicates that the vehicle is required to steer the steering wheel to a maximum during travel along the first curved path. At this time, the first curved track includes a third clothoid track, a first circular arc track, and a fourth clothoid track. The rotating angles of the third rotating track and the fourth rotating track are both the maximum rotating angle alpha, the curvature of the starting point position of the third rotating track is 0, and the curvature of the end point position of the third rotating track is 1/R_minThe end point of the third convolution track is connected to the start point of the first circular arc track, and the angle of the first circular arc track is theta ₁2 alpha, the curvature of the first circular arc track is 1/R from the starting position to the end position_minThe end point of the first circular arc track is connected with the starting point of the fourth circular arc track, and the curvature of the starting point of the fourth circular arc track is 1/R_minThe curvature of the end position of the fourth clothoid locus is 0.

Specifically, the coordinates and related parameters of the first curvilinear path may be calculated using the following formula:

L_max＝VT，

C＝L_max×R_min；

wherein R is_minIs the minimum turning radius, L, of the vehicle_maxThe method is characterized in that the method is the maximum clothoid length traveled by a vehicle when the vehicle turns from a starting coordinate point to reach a minimum turning radius, V is the vehicle speed, T is the time required for reaching the minimum turning radius, alpha is the maximum turning angle rotated by the vehicle when the vehicle turns from the starting coordinate point to reach the minimum turning radius, C is a clothoid constant, x is the abscissa of a point on a first clothoid track or a third clothoid track in a first curve track, y is the ordinate of a point on the first clothoid track or the third clothoid track in the first curve track, and l is the arc length corresponding to the point on the first clothoid track or the third clothoid track in the first curve track to the track starting point.

Further, the angle theta of the first curve track₁For example, when the angle is larger than 2 α, as shown in fig. 11, the third rotation locus and the fourth rotation locus both rotate at α, and the angle of the first circular arc locus is 2 γ₁，2γ₁＝θ₁-2 α. The arc length L from the starting point to the end point of the third convolution track is L_max. Substituting the above formula to obtain the coordinate (x) of the third convolution trajectory end point₂，y₂) Further, the coordinate of the center o (x, y) of the first circular arc track is (x)₂-R_minsinα，y₂+R_mincosα)。

Connecting line L between the center of the first arc track and the midpoint of the first arc track₁The equation ax + by + c is 0, then

b＝-1，c＝y₂+R_mincosα-a(x₂-R_minsin α), the end point coordinate of the first curve trajectory can be obtained as

Further, the angle θ still rotated by the first curved trajectory₁Greater than 2 α for example, for a given end point ordinate y of the first curve path₁End, first calculate the coordinate (x) of the end point of the third convolution track₂，y₂) Let c₁＝y₂+R_mincosα，c₂＝x₂-R_minsin α, c ═ c in the equation of connecting the center of the first arc track and the midpoint of the first arc track can be obtained₁-ac₂Continue to substitute b and c

Obtain a linear equation of two da for a²+ ea + f is 0, d is 1,

the value of a, the angle theta through which the first curve path turns, can be determined₁π +2atana, by θ₁＝2α+2γ₁Can find gamma₁According to the center o (x, y) of the first circular arc track and the rotation angle gamma of the first circular arc track₁The radius can be found as R_minFrom

Start the central angle to rotate by 2 gamma₁The x coordinate of the third convolution locus is rotated by 2 α +2 γ again by taking the opposite value₁And then the second circular arc track is translated to the end point of the first circular arc track to obtain a fourth circular track, so that a complete first curve track is obtained.

Further, as shown in fig. 3, the second standard path includes a third curved track and a fourth curved track.

The third curve track is connected with the fourth curve track, the third curve track and the fourth curve track are centrosymmetric about a connection position, so that tangents of the starting position and the ending position of the second standard path are parallel, the second standard path with the symmetric design is adopted, the calculation amount for generating the second standard path can be reduced, the complete second standard path can be obtained as long as the third curve track is obtained, and the generation difficulty of the second standard path is effectively reduced.

Further, as shown in fig. 12, the third curved trajectory includes a second circular arc trajectory and a fifth clothoid trajectory.

Specifically, the fifth clothoid trace is rotated by an angle at which the vehicle turns from the start coordinate point to the minimum turning radius R_minThe maximum rotation angle alpha of the second arc track is equal to the rotation angle theta of the third curve track₃Minus the maximum rotation angle alpha. The curvature of the second circular arc track is 1/R from the starting position to the end position_minThe end point of the second circular arc track is connected with the start point of the fifth circular track, and the curvature of the position of the start point of the fifth circular track is 1/R_minThe curvature of the end position of the fifth clothoid trace is 0.

Further, the end point ordinate y for a given third curve path₃End, first, the end point coordinate (x) of the third convolution track is calculated₂，y₂)。

Let o be x₂cosα+y₂sinα，p＝x₂sinα-y₂cosα-R_min，q＝R_min-y₃_end，

The angle of the second arc track is 2 gamma₂Wherein, in the step (A),

further according to the circle center (0, R) of the second circular arc track_min) Radius R_minObtained from

Start the central angle to rotate by 2 gamma₂And the fifth clothoid track can be inverted by the x coordinate of the third clothoid track in the first curve track and rotated by alpha +2 gamma₂And translating to the end point of the second arc track to obtain the third curve track.

Example seven:

as shown in FIG. 13, in one embodiment of the present invention, a control system 150 for a vehicle is provided, including a memory 152 and a processor 154; the memory 152 is configured and adapted to store a computer program; the processor 154 is configured as being adapted to execute a computer program to implement the control method of the vehicle as provided in any of the embodiments described above.

In this embodiment, the control system 150 of the vehicle includes the memory 152 and the processor 154, and thereby implements the control method of the vehicle as provided in any of the embodiments described above, and therefore, the control system 150 of the vehicle includes all the advantageous effects of the control method of the vehicle as provided in any of the embodiments described above.

Specifically, in the process of transferring the garage or parking in parallel of the vehicle, the manual work is not needed, so that the position and the running direction of the vehicle can be quickly adjusted according to the automatically generated vehicle running track, unnecessary starting and stopping actions are avoided, the overall energy consumption and the component abrasion of the vehicle are reduced, and the efficiency of transferring the garage or parking in parallel of the vehicle is improved.

Example eight:

in one embodiment of the present invention, further, there is provided a vehicle including a vehicle body, a travel mechanism, and the control system 150 of the vehicle in the above-described embodiment. The traveling mechanism is disposed on the vehicle body, the vehicle control system 150 is electrically connected to the traveling mechanism, and the vehicle control system 150 is used to control the traveling mechanism.

The vehicle provided in the present embodiment includes a vehicle body, a travel mechanism, and the control system 150 of the vehicle in the above-described embodiment. Therefore, the vehicle has all the advantages of the control system 150 of the vehicle provided in the above embodiments, and the description thereof is omitted.

The first embodiment is as follows:

as shown in fig. 14, in an embodiment of the present invention, further, taking the control of the vehicle moving warehouse as an example, the control method of the vehicle includes:

s1402, inputting a starting posture (x0, y0, th0) and a target posture (good _ x, good _ y, good _ th) of the vehicle;

s1404, transferring (gold _ x, gold _ y) to a coordinate system with (x0, y0) as an origin and the gold _ th direction as the positive direction of the x axis;

s1406, calculating an angle difference th _ diff between th0 and good _ th;

s1408, judging whether the absolute value of th _ diff is larger than 0, if so, executing S1410, otherwise, executing S1414;

s1410, judging whether th _ diff is smaller than 0 and larger than or equal to the maximum rotation angle-alpha, if not, executing S1412, otherwise, executing S1418;

s1412, judging whether th _ diff is greater than 0 and less than or equal to the maximum rotation angle alpha, if so, executing S1416, otherwise, ending;

s1414, solving according to the first type of situation to obtain a vehicle advancing track;

s1416, solving according to the second type of situation to obtain a vehicle advancing track;

s1418, solving according to the third type of situation to obtain a vehicle advancing track;

s1420, judging whether the vehicle advancing track is out of bounds, if so, ending, otherwise, executing S1422;

and S1422, converting the vehicle traveling track into a local map coordinate system.

Particularly in the controlBefore the vehicle is moved to a garage, firstly setting parameters, including: minimum turning radius R of vehicle_minThe vehicle speed V, and the ratio T of the maximum steering angle of the steering wheel to the maximum rotational angular speed of the steering wheel. The minimum turning radius R of the vehicle from the starting coordinate point to the turning point can be calculated_minLength L of maximum clothoid curve of time-lapse_maxAnd the maximum angle of rotation alpha that is rotated. And then setting the field size of the garage, and establishing a local coordinate system according to the size of the rectangular limited space.

The concrete steps of controlling the vehicle to move the garage are as follows:

(1) acquiring a starting posture and a target posture of a vehicle; wherein the starting posture of the vehicle comprises a starting coordinate point (x0, y0) and a starting heading th0, and the target posture of the vehicle comprises a target coordinate point (good _ x, good _ y) and a target heading good _ th;

(2) converting the end point coordinate to a coordinate system taking the start point coordinate as an origin point and the end point direction as the positive direction of the x axis;

(3) according to the angle difference between the initial course and the terminal course, recording as th _ diff, and dividing the solution of the vehicle advancing track into three types of conditions: in the first case, th _ diff is 0; in the second case, th _ diff is greater than 0 and less than α; in the third case, th _ diff is greater than- α and less than 0;

(4) and converting the vehicle traveling track back to the local map coordinate system.

The garage moving process can be divided into one or more car moving processes, and if the distance of the transverse movement required by the car is large, the car needs to move for many times. Each car moving process can be divided into a first stage and a second stage; the first stage is that the vehicle turns the steering wheel to a certain angle from the steering initial position and then returns to the positive steering wheel to turn the vehicle body to a certain angle; the second stage is that the steering wheel is rotated in the direction opposite to the first stage and then returns to the positive steering wheel again to enable the vehicle to reach the parking target position; the track of the second stage can be obtained by rotating and translating the track of the first stage; the rotation angle is clockwise when the rotation angle is positive and counterclockwise when the rotation angle is negative.

The track of the first stage has two composition modes, wherein the first mode sequentially comprises a clothoid curve, an arc (optional) and a clothoid curve, the second mode comprises an arc and a clothoid curve, the direction of the vehicle is required to rotate in situ at the beginning, and the required longitudinal distance (x direction) is shorter than that of the first mode under the condition that the transverse (y direction) moving distance of the vehicle is certain; under the condition that y is constant, only a unique track corresponds to the first mode and the second mode, namely the corresponding track with the transverse moving distance y of the vehicle can be calculated according to y.

The algorithm for the first case is as follows: (1) let i equal to 1; (2) tmp _ good _ y ═ good _ y/i; (3) calculating a track 1 with the end point y of the first mode as tmp _ good _ y, if 2 times of x of the end point of the track 1 is less than good _ x, the track does not exceed the boundary and meets the requirement, and turning to the step (6), otherwise, executing the step (4); (4) calculating a track 2 with the end point y of the second mode as tmp _ good _ y, if 2 times of x of the end point of the track 2 is less than good _ x, the track does not exceed the boundary and meets the requirement, and turning to the step (6), otherwise, executing the step (5); (5) increasing i by 1, if i is more than the set maximum times, exiting, otherwise, turning to the step (2); (6) and (3) obtaining the track of the second stage by rotating and translating the track 1 or 2, and if i is greater than 1, repeating the whole track for i-1 times, and exiting.

The algorithm for the second case is as follows: (1) calculating the coordinates (c _ x, c _ y) of a point on the first section of clothoid curve in the direction equal to th _ diff, and calculating the center of a circle (0, R)_min) Radius R_minThe coordinates (a _ x, a _ y) of the point after the rotation of th _ diff from 1.5 pi; (2) let j equal 1; (3) tmp _ good _ y ═ good _ y/j; (4) calculating a track 1 with an end point y of the first mode being (tmp _ good _ y + c _ y)/2, if the subtraction c _ x of 2 times of x of the end point of the track 1 is smaller than the good _ x, the track does not exceed the boundary and meets the requirement, and going to the step (7), otherwise, executing the step (5); (5) calculating a track 2 with an end point y of the second mode being (tmp _ good _ y + a _ y)/2, if the subtraction a _ x of 2 times of x of the end point of the track 2 is smaller than the good _ x, the track does not exceed the boundary and meets the requirement, and going to the step (7), otherwise, executing the step (6); (6) increasing j by 1, if j is more than the set maximum times, exiting, otherwise, turning to the step (3); (7) obtaining the track of the second stage by rotating and translating the track 1 or 2, finding out the point where y is c _ y or a _ y in the whole track, and intercepting the track from the point toThe last point, then translate the truncated trajectory (-c _ x, -c _ y) or (-a _ x, -a _ y); (8) if j is equal to 1, exit is performed, otherwise, processing is performed next as per the first category case.

The algorithm for the third case is as follows: (1) calculating the coordinates (c _ x, c _ y) of a point on the first segment clothoid in the direction equal to-th _ diff; (2) let k equal to 1; (3) rotating (good _ x, good _ y/k) by-th _ diff to obtain (r _ x, r _ y); (4) calculating a track 1 with the end point y of the first mode as (r _ y + c _ y)/2, if the subtraction of c _ x from 2 times of x of the end point of the track 1 is less than r _ x, the track does not exceed the boundary, and the step (6) is carried out if the requirement is met, otherwise the step (5) is carried out; (5) increasing k by 1, if k is more than the set maximum times, exiting, otherwise, turning to the step (3); (6) obtaining a track of a second stage by rotating and translating the track 1, finding out a point where y is r _ y in the whole track, and intercepting a point from a starting point to the point; (7) translating the track along an x axis to enable x at the end point to be r _ x, connecting the original point with the starting point of the track by using a straight line, and combining the straight line into the whole track; (8) rotating the track by th _ diff; (9) if k is equal to 1, exit is performed, otherwise, processing continues as in the first case.

The method for controlling the vehicle to move to the garage provided by the embodiment prevents the curvature of the vehicle traveling track from changing suddenly, thereby reducing the tire wear caused by pivot steering or quick steering and being beneficial to the tracking of the vehicle. The calculation of the vehicle advancing track is simple, the requirement on a hardware platform is reduced, and the cost is saved.

The second embodiment is as follows:

as shown in fig. 15, in an embodiment of the present invention, further, taking an example of controlling a vehicle to park in parallel, the control method of the vehicle includes:

s1502, inputting the size of the parking space;

s1504, judging whether the size of the parking space is larger than the required minimum size, if so, executing S1506, otherwise, ending;

s1506, setting an initial y value of the target coordinate point;

s1508, solving the parking track according to the first mode;

s1510, judging whether the vehicle collides with the parking space, if so, executing S1512, otherwise, ending;

s1512, solving a parking track according to a second mode;

s1514, judge whether will collide with parking stall, if judge the result is, carry out S1516, otherwise finish;

s1516, increasing the value of y by 0.2;

and S1518, judging whether y is larger than the threshold, if so, ending, otherwise, executing S1508.

Specifically, before controlling the vehicle to perform parallel parking, vehicle size parameters are firstly acquired, including: the length and width of the vehicle body, and the distance from the center of the rear axle of the vehicle (the coordinate point of the vehicle) to the tail of the vehicle. The method comprises the following specific steps of controlling the vehicle to park in parallel:

(1) setting the size of a parking space;

(2) judging whether the size of the parking space is larger than the required minimum size or not, and if not, exiting;

(3) setting the initial y value of the target coordinate point as the sum of the width of the parking space and half of the width of the vehicle body;

(4) according to the track calculation method in the first embodiment, the track 1 in the first mode is calculated, the track in the second stage is obtained by rotating and translating the track 1, and the vehicle exits if the vehicle does not collide with a parking space, otherwise, the step (5) is executed;

(5) according to the track calculation method in the first specific embodiment, the track 2 in the second mode is calculated, the track in the second stage is obtained by rotating and translating the track 2, and the vehicle exits if the vehicle does not collide with a parking space, otherwise, the step (6) is executed;

(6) and increasing the value of y by 0.2, exiting if y is larger than the set maximum threshold, and otherwise, turning to the step (4).

The method for controlling the parallel parking of the vehicles provided by the embodiment prevents the sudden change of the curvature of the advancing track of the vehicles, and the vehicles can finish the parallel parking through one-time starting and stopping, so that the tire wear caused by pivot steering or quick steering is reduced, and the method is favorable for tracking the vehicles. The calculation of the vehicle advancing track is simple, the requirement on a hardware platform is reduced, and the cost is saved.

In the description of the present invention, the terms "plurality" or "a plurality" refer to two or more, and unless otherwise specifically defined, the terms "upper", "lower", and the like indicate orientations or positional relationships based on the orientations or positional relationships illustrated in the drawings, and are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention; the terms "connected," "mounted," "secured," and the like are to be construed broadly and include, for example, fixed connections, removable connections, or integral connections; may be directly connected or indirectly connected through an intermediate. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the description of the present invention, the description of the terms "one embodiment," "some embodiments," "specific embodiments," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In the present invention, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. 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.

Claims

1. A control method of a vehicle, characterized by comprising:

acquiring an initial coordinate point, an initial course, a target coordinate point and a target course of the vehicle;

acquiring the running parameters of the vehicle;

determining a steering angle according to the starting course and the target course;

generating a vehicle travelling track according to the starting coordinate point, the target coordinate point, the steering angle and the operation parameter;

controlling the vehicle to travel along the vehicle travel track;

wherein the operating parameters include a minimum turning radius of the vehicle, a vehicle speed, and a time required to reach the minimum turning radius.

2. The control method of a vehicle according to claim 1, characterized by further comprising:

converting the initial coordinate point and the target coordinate point from a local map coordinate system to a relative coordinate system which takes the initial coordinate point as an origin and the target course as the positive direction of an x axis;

and calculating to obtain the maximum turning angle which is turned when the vehicle turns from the initial coordinate point to reach the minimum turning radius according to the operation parameters.

3. The control method of a vehicle according to claim 2, wherein said generating a vehicle travel locus from the start coordinate point, the target coordinate point, the steering angle, and the running parameter based on a case where the steering angle is equal to 0 includes:

step 3002, setting the value of the track execution times i to 1;

step 3004, setting a temporary displacement width, wherein the temporary displacement width is a ratio of a vertical coordinate and i of the target coordinate point in the relative coordinate system;

step 3006, generating a first standard path with the start coordinate point as a start point and the end ordinate as the temporary displacement width according to the operation parameter in the relative coordinate system;

step 3008, determining whether the abscissa of the end point of the first standard path is smaller than the abscissa of the target coordinate point, if so, performing step 3018, otherwise, performing step 3010;

step 3010, in the relative coordinate system, according to the operation parameter, generating a second standard path with the start coordinate point as a start point and the end ordinate as the temporary displacement width;

step 3012, determining whether the abscissa of the second standard path endpoint is smaller than the abscissa of the target coordinate point, if so, executing step 3018, otherwise, executing step 3014;

step 3014, increase the value of i by 1;

step 3016, determining whether i is greater than a first preset threshold, if not, executing step 3004, otherwise, ending generating the vehicle travel track;

step 3018, executing the first standard path or the second standard path i times to obtain the vehicle travel track;

and on the basis of the condition that the end point ordinate of the first standard path is the same as the end point ordinate of the second standard path, the end point abscissa of the second standard path is smaller than the end point abscissa of the first standard path.

4. The control method of a vehicle according to claim 2, wherein said generating a vehicle travel locus from the start coordinate point, the target coordinate point, the steering angle, and the running parameter based on a case where the steering angle is greater than 0 and equal to or less than the maximum turning angle includes:

step 4002, in the relative coordinate system, taking the starting coordinate point as a starting point, obtaining a clothoid curve that the vehicle travels when reaching the minimum turning radius from a straight start according to the operation parameters, and obtaining a first correction point on the clothoid curve;

step 4004, acquiring a circular curve with the minimum turning radius as the radius, a circle center abscissa of 0 and a circle center ordinate of the minimum turning radius in the relative coordinate system, and acquiring a second correction point on the circular curve in the first quadrant;

step 4006, setting the value of the first adjustment number j to 1;

step 4008, setting a temporary correction width, wherein the temporary correction width is a ratio of a vertical coordinate and a j of the target coordinate point in the relative coordinate system;

step 4010, in the relative coordinate system, according to the operating parameter, generating a first standard path with the starting coordinate point as a starting point and an end point ordinate as a sum of the temporary correction width and the ordinate of the first correction point;

step 4012, determining whether a difference between an abscissa of the first standard path end point and an abscissa of the first correction point is smaller than an abscissa of the target coordinate point, if so, executing step 4022, otherwise, executing step 4014;

step 4014, generating a second standard path using the start coordinate point as a start point and the end ordinate as a sum of the temporary correction width and the ordinate of the second correction point according to the operation parameter in the relative coordinate system;

step 4016, determining whether a difference between an abscissa of the second standard path end point and an abscissa of the second correction point is smaller than an abscissa of the target coordinate point, if so, executing step 4022, otherwise, executing step 4018;

step 4018, increment the value of j by 1;

step 4020, judging whether j is larger than a second preset threshold value, if not, executing step 4008, otherwise, ending generating the vehicle traveling track;

step 4022, intercepting a path from the first correction point to the first standard path end point to obtain a first correction path, or intercepting a path from the second correction point to the second standard path end point to obtain a second correction path;

step 4024, translating the first correction path or the second correction path to the origin of the relative coordinate system to obtain the vehicle travelling track;

the tangent angle at the first correction point is equal to the steering angle, the tangent angle at the second correction point is equal to the steering angle, and the end abscissa of the second standard path is smaller than the end abscissa of the first standard path based on the condition that the end ordinate of the first standard path is equal to the end ordinate of the second standard path.

5. The control method of a vehicle according to claim 2, wherein said generating a vehicle travel locus from the start coordinate point, the target coordinate point, the steering angle, and the running parameter based on a case where the steering angle is greater than or equal to a negative value of the maximum rotation angle and less than 0 includes:

step 5002, in the relative coordinate system, taking the starting coordinate point as a starting point, obtaining a clothoid curve that the vehicle travels when the vehicle reaches the minimum turning radius from a straight start according to the operation parameters, and obtaining a third correction point on the clothoid curve;

step 5004, setting the value of the second adjustment time k to 1;

step 5006, setting a first intermediate coordinate point, where an abscissa of the first intermediate coordinate point is an abscissa of the target coordinate point in the relative coordinate system, and an ordinate of the first intermediate coordinate point is a ratio of an ordinate of the target coordinate point in the relative coordinate system to k;

step 5008, rotating the absolute value of the steering angle counterclockwise by using the first intermediate coordinate point as a center with respect to the origin of the relative coordinate system to obtain a second intermediate coordinate point;

step 5010 of generating a first standard path with the starting coordinate point as a starting point and the end point ordinate as the sum of the ordinates of the third correction point and the second intermediate coordinate point according to the operation parameters in the relative coordinate system;

step 5012, judging whether the difference between the abscissa of the first standard path end point and the abscissa of the third correction point is smaller than the abscissa of the second intermediate coordinate point, if so, executing step 5018, otherwise, executing step 5014;

step 5014, increasing the value of k by 1;

step 5016, judging whether k is larger than a third preset threshold, if not, executing step 5006, otherwise, ending generation of the vehicle travelling track;

step 5018, intercepting a path from the starting point of the first standard path to a point where the ordinate of the first standard path is equal to the ordinate of the second middle coordinate point to obtain a third correction path;

step 5020, translating the third correction path in the positive direction of the x axis to enable the abscissa of the end point of the third correction path to be the same as the abscissa of the second middle coordinate point;

step 5022, a splicing straight line is arranged between the starting point of the third correction path and the origin point of the relative coordinate system, and a fourth correction path is obtained;

step 5024, clockwise rotating the absolute value of the steering angle by taking the origin of the relative coordinate system as the center of the fourth correction path to obtain the vehicle advancing track;

6. The control method of the vehicle according to any one of claims 3 to 5, characterized in that the first standard path includes:

a first curved track, the angle of the first curved track is greater than 0 degree and less than or equal to 90 degrees;

the second curve track is connected with the first curve track, and the second curve track and the first curve track are centrosymmetric about the connection point of the first curve track and the second curve track.

7. The control method of a vehicle according to claim 6,

based on the first curve track turning through an angle greater than 0 degrees and less than or equal to 2 times the maximum rotation angle, the first curve track includes: the terminal point of the first backspin track is connected with the starting point of the second backspin track, and the curvature of the terminal point of the first backspin track is the same as the curvature of the starting point of the second backspin track;

based on the first curved track turning an angle greater than 2 times the maximum turning angle and less than or equal to 90 degrees, the first curved track includes: the terminal point of the third clothoid track is connected with the starting point of the first circular arc track, the terminal point curvature of the third clothoid track is the same as the starting point curvature of the first circular arc track, the terminal point curvature of the first circular arc track is connected with the starting point of the fourth clothoid track, and the terminal point curvature of the first circular arc track is the same as the starting point curvature of the fourth clothoid track.

8. The control method of the vehicle according to any one of claims 3 to 5, characterized in that the second standard path includes:

a third curvilinear path, the angle of rotation of the third curvilinear path being greater than 0 degrees and less than or equal to 90 degrees;

a fourth curved track connected to the third curved track, the fourth curved track and the third curved track being centrosymmetric about a connection point of the third curved track and the fourth curved track.

9. The control method of the vehicle according to claim 8, characterized in that the third curve locus includes:

a second circular arc trajectory;

and the starting point of the fifth circular track is connected with the end point of the second circular arc track, and the curvature of the end point of the second circular arc track is the same as that of the starting point of the fifth circular track.

10. A control system of a vehicle, characterized by comprising:

a memory configured to be adapted to store a computer program;

a processor configured to be adapted to execute the computer program to implement a control method of a vehicle according to any one of claims 1 to 9.

11. A vehicle, characterized by comprising:

a vehicle body;

a travel mechanism provided on the vehicle body;

the control system of the vehicle as claimed in claim 10, the control system of the vehicle being electrically connected to the travel mechanism, the control system of the vehicle being for controlling the travel mechanism.