Pure tracking calculation method and system based on adjacent zero course error preview point compensation

Abstract

The invention discloses a pure tracking calculation method and system based on adjacent zero course error preview point compensation, and relates to the technical field of trajectory tracking algorithms of automatic parking systems, and the method comprises the steps: calculating a preview distance, amplifying a current transverse error and a course error according to a first proportion value, and taking the amplified transverse error and course error as a transverse error; calculating a zero course error preview point, and searching a position point in the vertical direction of the preview point of the original pure tracking algorithm, so that the orientation of a vehicle body is the same as the expected direction of a planned track point when the vehicle moves to the point according to Ackerman steering; performing weighted averaging on the zero lateral error preview point and the zero course error preview point, and performing weighted averaging on the zero lateral deviation point and the zero course error point according to a certain proportion in a tolerance zone range to obtain a fused preview point; and calculating a front wheel steering angle. According to the method, an adjustment space is reserved for the subsequent error suppression process, the probability of trajectory oscillation is reduced, the stability of a tracking algorithm is improved, the probability of occurrence of the trajectory oscillation phenomenon caused by the course error is reduced, and the stability of the tracking algorithm is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of trajectory tracking algorithms for automatic parking systems, and in particular to a pure tracking calculation method and system based on compensation of adjacent zero heading error preview points. Background Art

[0002] Automatic parking belongs to the short-range, low-speed, high curvature change rate, and high-precision control scenario. The common trajectory tracking algorithms used in the current automatic parking system are: pure tracking algorithm, feedforward curvature + PID, LQR + PID, MPC, etc. The pure tracking algorithm does not take into account the heading error, has poor anti-interference performance, and the trajectory is prone to oscillation, making it difficult to meet the requirements of high-precision control. The feedforward curvature + PID algorithm has many parameters and requires detailed parameter adjustment according to the scenario. The parameter adjustment process is difficult and time-consuming. LQR + PID is usually used for driving lane keeping and is difficult to adapt to parking scenarios with a high rate of change of trajectory curvature. The MPC algorithm requires iterative solution of the optimal control quantity, consumes a lot of computing power, has high hardware costs, and is difficult to apply on low-cost, low-computing power platforms. The present invention mainly improves the problem that the original pure tracking algorithm does not explicitly control the heading error and the trajectory is prone to oscillation, and realizes a vehicle lateral control algorithm with acceptable control accuracy, which can be solved analytically without iterative solution, and has low computing power and hardware requirements. Summary of the invention

[0003] In view of the above existing problems, the present invention calculates the front wheel turning angle in real time during the automatic parking process to accurately track the trajectory output by the planning module and reduce the lateral error and heading error of parking.

[0004] In order to solve the above technical problems, a pure tracking calculation method based on compensation of adjacent zero heading error preview points is proposed, including:

[0005] Calculate the preview distance, and amplify the current lateral error and heading error by a first proportional value as the lateral error; calculate the zero heading error preview point; the weighted average of the zero lateral error preview point and the zero heading error preview point, and proportionally weight the zero lateral error preview point, the zero heading error preview point and the zero heading error preview point within the tolerance band to obtain a fused preview point; calculate the front wheel turning angle.

[0006] As a preferred solution of the pure tracking calculation method based on compensation of the adjacent zero heading error preview point described in the present invention, the calculation of the front wheel turning angle includes calculating the turning radius required to reach the fusion preview point according to the Ackermann steering and the vehicle wheelbase, and then calculating the corresponding steering wheel angle.

[0007] As a preferred solution of the pure tracking calculation method based on adjacent zero heading error preview point compensation described in the present invention, wherein: the zero heading error preview point includes, among the planned path points, searching for the first path point that exceeds the preview distance in the expected direction of travel as the preview point, and calculating the zero heading error preview point coordinates in the vertical direction of the preview point.

[0008] As a preferred solution of the pure tracking calculation method based on compensation of adjacent zero heading error preview points described in the present invention, wherein: the fusion preview point includes calculating the allowable lateral error range of the current position, calculating the distance between the zero lateral error preview point and the zero heading error preview point, and calculating the coordinates of the fusion preview point. The allowable lateral error range includes the length of the remaining trajectory of the path planned for parking in the parking space, and calculating the allowable lateral error e of the current position in the form of a quadratic function. a :

[0009] e a =min(a m ,a 2 s 2 +a 0 )

[0010] Among them, a 0 The engineering error requirement when reaching the parking point; a 2 This is the allowable error when the center of the rear axle of the vehicle reaches the parking space entrance; a m It is the maximum allowable lateral error of the whole process.

[0011] As a preferred solution of the pure tracking calculation method based on compensation of adjacent zero heading error preview points of the present invention, wherein: the zero lateral error preview point and the zero heading error preview point include, and the distance d between the zero lateral error preview point and the zero heading error preview point is:

[0012]

[0013] Among them, x P0 ,y P0 P 0 The coordinates of the point, x P1 and P1 P 1 The coordinates of the point.

[0014] As a preferred solution of the pure tracking calculation method based on compensation of adjacent zero heading error preview points described in the present invention, wherein: the coordinates of the fused preview points include calculating the coordinates of the fused preview points: when k*d <e a , calculate the fusion preview point P as:

[0015] P=kP 1 +(1-k)P 0

[0016] If k*d≥e a , calculate the fusion preview point P as:

[0017]

[0018] Among them, k is the prescribed experience fusion weight.

[0019] As a preferred solution of the pure tracking calculation method based on compensation of adjacent zero heading error preview points described in the present invention, the preview distance includes: a path for parking in the parking space has been planned according to the parking space position, and discrete path points with direction information are marked on the current path to meet the physical limitations of vehicle kinematics and vehicle actuators. At the same time, the coordinates and directions of the path points are converted to the vehicle body coordinate system according to the current posture of the vehicle body output by positioning.

[0020] Set the path points as the two path points closest to the center of the rear axle of the vehicle in the vehicle body coordinate system, perform linear interpolation of position and heading angle based on the two adjacent path points closest to the current position, estimate the current lateral error and heading error, and multiply the two errors by two proportional coefficients k respectively. 1 and k 2 , get two distances, take the larger value and limit the minimum value l m As the preview distance l d :

[0021] l d =max(l m ,max(k 1 e l ,k 2 e θ ))

[0022] Among them, e l is the lateral error, e θ is the heading error.

[0023] Another object of the present invention is to provide a pure tracking calculation system based on compensation of adjacent zero heading error preview points, which aims to solve multiple technical problems in the field of autonomous driving and navigation, including improving trajectory tracking accuracy, enhancing steering control accuracy, reducing heading error, accurately controlling lateral error, optimizing steering instructions, and improving the real-time and adaptability of the system. By accurately calculating the preview distance, zero heading error preview point and fused preview point, and combining the Ackerman steering geometry model, the system can adjust the steering instructions in real time in a complex and changeable driving environment, ensuring that the vehicle can smoothly, naturally and accurately track the predetermined trajectory, thereby improving driving safety and efficiency.

[0024] As a preferred solution of the pure tracking calculation system based on adjacent zero heading error preview point compensation described in the present invention, it is characterized by including a preview distance module, a zero heading error preview point module, a fused preview point module and a front wheel turning angle module.

[0025] The preview distance module uses the two path points closest to the current vehicle position to perform linear interpolation to estimate the current lateral error and heading error, uses the empirical proportional coefficient to amplify the error value, takes the larger value and limits it to the minimum value, and calculates the final preview distance as the input of the zero-difference preview point module, ensuring that the vehicle can track the given trajectory more accurately when approaching the parking space.

[0026] The zero-difference preview point module searches for the zero-difference preview point on the vertical line of the expected heading according to the preview point, and determines the coordinates by geometric method to ensure that the vehicle body orientation is consistent with the expectation when the vehicle turns. The zero-difference preview point output by the zero-difference preview point module is input into the fusion preview point calculation module to participate in the calculation of the fusion preview point, so that the vehicle moves along the expected heading and reduces the heading error.

[0027] The fusion preview point module determines the distance between the zero lateral deviation point and the zero heading error point by calculating the allowable lateral error range of the current position, and determines the calculation method of the fusion preview point based on the preset fusion weight. The fusion result of the fusion preview point module will be transmitted to the front wheel turning angle module to obtain the final steering instruction, thereby improving the vehicle tracking accuracy.

[0028] The front wheel steering angle module uses the Ackerman steering geometry model and the vehicle's wheelbase to calculate the steering radius required to reach the fusion preview point, converts it into a steering wheel angle, and provides accurate steering instructions for the driving control system.

[0029] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and is characterized in that when the processor executes the computer program, the steps of the pure tracking calculation method based on compensation of adjacent zero heading error preview points are implemented.

[0030] A computer-readable storage medium having a computer program stored thereon, characterized in that when the computer program is executed by a processor, the steps of the pure tracking calculation method based on compensation of adjacent zero heading error preview points are implemented.

[0031] Beneficial effects of the present invention: The present invention dynamically adjusts the preview distance based on the method of calculating the preview distance based on the current error. When the current tracking error is small, the preview distance is small, and the actual trajectory is more consistent with the planned trajectory; when the error is large, the preview distance is large, leaving adjustment space for the subsequent error suppression process, reducing the probability of trajectory oscillation and improving the stability of the tracking algorithm.

[0032] The fused preview point is calculated based on the zero lateral deviation point and the zero heading error point, and the heading error is introduced into the trajectory tracking algorithm. The original pure tracking algorithm only calculates the control amount based on the zero lateral deviation preview point, which may lead to a large heading error when reaching the preview point, and then cause subsequent trajectory oscillation. The fused preview point enables the control algorithm to suppress the lateral error and the heading error at the same time, reducing the probability of the heading error and the trajectory oscillation caused by it, and improving the stability of the tracking algorithm. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0034] Figure 1 An overall flow chart of a pure tracking calculation method based on compensation of adjacent zero heading error preview points provided by one embodiment of the present invention.

[0035] Figure 2 A schematic diagram of the vehicle body coordinate system at the current moment of a monitoring system of a pure tracking calculation method based on compensation of adjacent zero heading error preview points provided by an embodiment of the present invention.

[0036] Figure 3 A system solution flow chart of a pure tracking calculation system based on compensation of adjacent zero heading error preview points provided for one embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0038] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0039] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it an embodiment that is mutually exclusive with other embodiments, either individually or selectively.

[0040] The present invention is described in detail with reference to schematic diagrams. When describing the embodiments of the present invention, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0041] At the same time, in the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper, lower, inner and outer" are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first, second or third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0042] In the present invention, unless otherwise clearly specified and limited, the terms "install, connect, connect" should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection or an integral connection; it can also be a mechanical connection, an electrical connection or a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0043] Example 1, reference Figure 1-Figure 2 , which is the first embodiment of the present invention, provides a pure tracking calculation method based on compensation of adjacent zero heading error preview points, including:

[0044] S1: Calculate the preview distance, and amplify the current lateral error and heading error by a first proportional value as the lateral error.

[0045] Furthermore, the path to the parking space has been planned according to the parking space position, and the discrete path points with direction information are marked on the current path to meet the physical constraints of vehicle kinematics and vehicle actuators. At the same time, the coordinates and directions of the path points are converted to the vehicle body coordinate system according to the current position of the vehicle body output by positioning; Figure 2 As shown, Figure 2 It is a schematic diagram of the vehicle body coordinate system at the current moment. The origin is the center of the rear axle of the vehicle, the positive direction of the x-axis is the front direction of the vehicle, the orange points are the planned path points, and the direction of the path points is the tangent direction of the path.

[0046] like Figure 2 , set the path point T 1 =(x 1 ,y 1 ,θ 1 ) T , waypoint T 2 =(x 2 ,y 2 ,θ 2 ) T are the two path points closest to the center of the rear axle in the vehicle body coordinate system. Linear interpolation of position and heading angle is performed based on the two adjacent path points closest to the current position to estimate the current lateral error e l and heading error e θ :

[0047]

[0048] Among them, x and y are the horizontal and vertical coordinates of the path point, and θ is the desired heading angle.

[0049] Multiply the two errors by two proportional coefficients k respectively 1 and k 2 , get two distances, take the larger value and limit the minimum value l m As the preview distance l d :

[0050] l d =max(l m ,max(k 1 e l ,k 2 e θ ))

[0051] Among them, a set of empirical values ​​is l m =0.25m, k 1 =5, k 2 =0.167m / deg.

[0052] S2: Calculate the zero heading error preview point and find the position point in the vertical direction of the original pure tracking algorithm preview point, so that when the vehicle moves to the current position point according to the Ackermann steering, the body direction is the same as the expected direction of the planned trajectory point.

[0053] Furthermore, among the planned path points, the first path point exceeding the preview distance is searched in the expected direction of travel as the preview point P 0 ,like Figure 2 As shown, due to the existence of positioning error and control error, there is a certain deviation between the center of the rear axle of the vehicle, i.e., the origin, and the planned path, i.e., the orange discrete points. The original pure tracking algorithm is based on P 0The coordinates of a turning radius r are calculated 0 , due to the above deviation, if the vehicle moves according to this turning radius, the moving trajectory will be as follows Figure 2 As shown by the green dotted line in the middle, go to P 0 When the vehicle body is actually facing P 0 E will move towards P with the expectation 0 If G does not match, there is a heading error. If the heading error is large, it will cause serious trajectory overshoot and oscillation problems. 0 It is the preview point selected by the original pure tracking algorithm. It is the first path point in the direction of travel whose distance is greater than the preview distance. It is one of the planned path points.

[0054] Pass preview point P 0 Make a vertical direction perpendicular to the desired heading P 0 G straight line j is the orange solid line, straight line j intersects the y-axis at C 1 , with C 1 The center of the circle is AC 1 Draw a circle with radius as blue dashed line, and the circle intersects the straight line j at P 1 , it can be proved that if the car turns to P along the blue line 1 When the vehicle body faces P 1 F and expectation towards P 0 G is the same, that is, point P 1 It is the zero flight difference preview point, calculated at the preview point P 0 The coordinates of the zero flight difference preview point in the vertical direction:

[0055]

[0056]

[0057]

[0058] S3: The weighted average of the zero lateral error preview point and the zero heading error preview point. The fused preview point is obtained by proportionally weighting the zero lateral deviation point and the zero heading error point within the tolerance band.

[0059] Furthermore, the allowable lateral error range of the current position is calculated, and the allowable lateral error of the current position is calculated in the form of a quadratic function according to the length of the remaining trajectory of the path planned for parking in the parking space.

[0060] It should be noted that the distance d between the zero lateral deviation point and the zero heading error point is calculated as:

[0061]

[0062] in, P 0 The coordinates of the point, and P1 The coordinates of the point.

[0063] It should also be noted that the coordinates of the fusion preview point are calculated: when k*d <e a , the method for calculating the fusion preview point is:

[0064] P=kP 1 +(1-k)P 0

[0065] If k*d≥e a , the method for calculating the fusion preview point is:

[0066]

[0067] The empirical fusion weight k is specified to be between 0.5 and 0.9.

[0068] S4: Calculate the front wheel steering angle.

[0069] The turning radius required to reach the fusion preview point is calculated based on the Ackermann steering and the vehicle wheelbase.

[0070] Example 2, reference Figure 1-Figure 2 The second embodiment of the present invention provides a pure tracking calculation method based on compensation of adjacent zero heading error preview points, including:

[0071] In the automatic parking scenario, it helps the vehicle to park accurately. By calculating the preview distance, zero heading error preview point and zero lateral error preview point, the vehicle can be precisely controlled during the parking process.

[0072] S1: Calculate the preview distance, and amplify the current lateral error and heading error by a first proportional value as the lateral error.

[0073] Furthermore, the path to the parking space has been planned according to the parking space position, and the discrete path points with direction information are marked on the current path to meet the physical constraints of vehicle kinematics and vehicle actuators. At the same time, the coordinates and directions of the path points are converted to the vehicle body coordinate system according to the current position of the vehicle body output by positioning;

[0074] Set the path points as the two path points closest to the center of the rear axle of the vehicle in the vehicle body coordinate system, perform linear interpolation of position and heading angle based on the two adjacent path points closest to the current position, estimate the current lateral error and heading error, and multiply the two errors by two proportional coefficients k respectively. 1 and k 2 , get two distances, take the larger value and limit the minimum value l m As the preview distance l d :

[0075] l d=max(l m ,max(k 1 e l ,k 2 e θ ))

[0076] Among them, e l is the lateral error, e θ is the heading error, a set of empirical values ​​is l m =0.25m, k 1 =5, k 2 =0.167m / deg.

[0077] S2: Calculate the zero heading error preview point and find the position point in the vertical direction of the original pure tracking algorithm preview point, so that when the vehicle moves to the current position point according to the Ackermann steering, the body direction is the same as the expected direction of the planned trajectory point.

[0078] Furthermore, among the planned path points, the first path point exceeding the preview distance is searched in the expected direction of travel as the preview point, and the zero-difference preview point coordinates in the vertical direction of the preview point are calculated.

[0079] S3: The weighted average of the zero lateral error preview point and the zero heading error preview point. The fused preview point is obtained by proportionally weighting the zero lateral deviation point and the zero heading error point within the tolerance band.

[0080] Furthermore, the allowable lateral error range of the current position is calculated. According to the length s of the remaining trajectory of the planned parking path, the allowable lateral error e of the current position is calculated in the form of a quadratic function. a :

[0081] e a =min(a m ,a 2 s 2 +a 0 )

[0082] Among them, a 0 =0.1, that is, the engineering error requirement when reaching the parking point is 0.1m; the coefficient of the quadratic term a 2 =0.008, that is, when the rear axle center of the vehicle reaches the parking space entrance, an error of 0.15m to 0.18m is allowed; the maximum value of the lateral error allowed during the whole process is a m =0.3m.

[0083] It should be noted that the distance d between the zero lateral deviation point and the zero heading error point is calculated as:

[0084]

[0085] in, P 0 The coordinates of the point, and P 1 The coordinates of the point.

[0086] It should also be noted that the coordinates of the fusion preview point are calculated: when k*d <e a , the method for calculating the fusion preview point is:

[0087] P=kP 1 +(1-k)P 0

[0088] If k*d≥e a , the method for calculating the fusion preview point is:

[0089]

[0090] The empirical fusion weight k is specified to be between 0.5 and 0.9.

[0091] S4: Calculate the front wheel steering angle.

[0092] According to Ackerman steering and vehicle wheelbase l a Calculate the turning radius r required to reach the fusion preview point, and then calculate the corresponding steering wheel angle.

[0093] According to Ackerman steering, the required front wheel turning angle δ is: δ = arctan (l a / r).

[0094] The steering wheel to front wheel angle rotation ratio is k δ , the steering wheel angle δs is: δ s =δ / k δ .

[0095] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

[0096] Embodiment 3, the third embodiment of the present invention, is different from the first two embodiments in that:

[0097] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, and other media that can store program codes.

[0098] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0099] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0100] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0101] Example 4, reference Figure 3 , which is the fourth embodiment of the present invention, provides a pure tracking calculation system based on compensation of adjacent zero heading error preview points, including a preview distance module, a zero heading error preview point module, a fusion preview point module and a front wheel turning angle module.

[0102] The preview distance module uses the two path points closest to the current vehicle position to perform linear interpolation to estimate the current lateral error and heading error, uses the empirical proportional coefficient to amplify the error value, takes the larger value and limits it to the minimum value, and calculates the final preview distance as the input of the zero-difference preview point module, ensuring that the vehicle can track the given trajectory more accurately when approaching a parking space.

[0103] The zero-difference preview point module searches for the zero-difference preview point on the vertical line of the expected heading based on the preview point, and determines the coordinates by geometric methods to ensure that the vehicle's body orientation is consistent with expectations when turning. The zero-difference preview point output by the zero-difference preview point module is input into the fusion preview point calculation module to participate in the calculation of the fusion preview point, so that the vehicle moves in the expected heading and reduces the heading error.

[0104] The fusion preview point module calculates the allowable lateral error range of the current position, determines the distance between the zero lateral deviation point and the zero heading error point, and determines the calculation method of the fusion preview point based on the preset fusion weight. The fusion result of the fusion preview point module will be transmitted to the front wheel steering angle module to obtain the final steering instruction, thereby improving the vehicle tracking accuracy.

[0105] The front wheel steering angle module uses the Ackerman steering geometry model and the vehicle's wheelbase to calculate the steering radius required to reach the fusion preview point, converts it into the steering wheel angle, and provides accurate steering instructions for the driving control system.

[0106] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A pure tracking calculation method based on compensation of adjacent zero heading error preview points, characterized in that: include, Calculate the preview distance, and amplify the current lateral error and heading error by a first proportional value as the lateral error; Calculate the zero heading error preview point; The weighted average of the zero lateral error preview point and the zero heading error preview point is obtained by proportionally weighting the zero lateral error preview point, the zero heading error preview point and the zero heading error preview point within the tolerance band to obtain the fused preview point; Calculate the front wheel angle.

2. The pure tracking calculation method based on compensation of adjacent zero heading error preview points as claimed in claim 1 is characterized in that: The calculating of the front wheel turning angle includes calculating the turning radius required to reach the fusion preview point according to the Ackermann steering and the vehicle wheelbase, and then calculating the corresponding steering wheel angle.

3. The pure tracking calculation method based on compensation of adjacent zero heading error preview points as claimed in claim 2 is characterized in that: The zero heading error preview point includes searching for the first path point exceeding the preview distance in the expected direction of travel as the preview point among the planned path points, and calculating the zero heading error preview point coordinates in the vertical direction of the preview point.

4. The pure tracking calculation method based on compensation of adjacent zero heading error preview points as claimed in claim 3 is characterized in that: The fusion preview point includes calculating the allowable lateral error range of the current position, calculating the distance between the zero lateral error preview point and the zero heading error preview point, and calculating the coordinates of the fusion preview point. The allowable lateral error range includes calculating the allowable lateral error e of the current position in the form of a quadratic function based on the length of the remaining trajectory of the path planned for parking. a : e a =min(a m ,a2s 2 +a0) Among them, a0 is the engineering error requirement when reaching the parking point; a2 is the allowable error when the center of the rear axle of the vehicle reaches the vicinity of the parking space entrance; a m It is the maximum allowable lateral error of the whole process.

5. The pure tracking calculation method based on compensation of adjacent zero heading error preview points as claimed in claim 4 is characterized in that: The zero lateral error preview point and the zero heading error preview point include, and the distance d between the zero lateral error preview point and the zero heading error preview point is: in, is the coordinate of point P0, and is the coordinate of point P1.

6. The pure tracking calculation method based on compensation of adjacent zero heading error preview points as claimed in claim 5, characterized in that: The coordinates of the fused preview point include calculating the coordinates of the fused preview point: when k*d <e a , calculate the fusion preview point P as: P=kP1+(1-k)P0 If k*d≥e a , calculate the fusion preview point P as: Among them, k is the prescribed experience fusion weight.

7. The pure tracking calculation method based on compensation of adjacent zero heading error preview points as claimed in claim 6 is characterized in that: The preview distance includes planning a parking path according to the parking space position, marking discrete path points with direction information on the current path to meet the physical constraints of vehicle kinematics and vehicle actuators, and converting the coordinates and directions of the path points to the vehicle body coordinate system according to the current position of the vehicle body output by positioning; Set the path points as the two path points closest to the center of the rear axle of the vehicle in the vehicle body coordinate system, perform linear interpolation of position and heading angle according to the two adjacent path points closest to the current position, estimate the current lateral error and heading error, multiply the two errors by two proportional coefficients k1 and k2 respectively, and get two distances, take the larger value and limit the minimum value l m As the preview distance l d : L d =max(l m ,max(k1e l ,k2e θ )) Among them, e l is the lateral error, e θ is the heading error.

8. A system using the pure tracking calculation method based on compensation of adjacent zero heading error preview points as claimed in any one of claims 1 to 7, characterized in that: Including preview distance module, zero flight difference preview point module, fusion preview point module and front wheel turning angle module; The preview distance module uses the two path points closest to the current vehicle position to perform linear interpolation to estimate the current lateral error and heading error, uses the empirical proportional coefficient to amplify the error value, takes the larger value and limits it to the minimum value, and calculates the final preview distance as the input of the zero-difference preview point module, ensuring that the vehicle can track the given trajectory more accurately when approaching the parking space; The zero-difference preview point module searches for the zero-difference preview point on the vertical line of the desired heading according to the preview point, and determines the coordinates by geometric method to ensure that the vehicle body direction is consistent with the expectation when turning. The zero-difference preview point output by the zero-difference preview point module is input into the fusion preview point calculation module to participate in the calculation of the fusion preview point, so that the vehicle moves in the desired heading and reduces the heading error. The fusion preview point module determines the distance between the zero lateral deviation point and the zero heading error point by calculating the allowable lateral error range of the current position, and determines the calculation method of the fusion preview point based on the preset fusion weight. The fusion result of the fusion preview point module will be transmitted to the front wheel turning angle module to obtain the final steering instruction, thereby improving the vehicle tracking accuracy. The front wheel steering angle module uses the Ackerman steering geometry model and the vehicle's wheelbase to calculate the steering radius required to reach the fusion preview point, converts it into a steering wheel angle, and provides accurate steering instructions for the driving control system.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the pure tracking calculation method based on compensation for adjacent zero heading error preview points according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the pure tracking calculation method based on compensation for adjacent zero heading error preview points according to any one of claims 1 to 7 are implemented.

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