Method and system for controlling steering wheel angle of multi-steering wheel vehicle in place, storage medium

Abstract

The application discloses a method and system for controlling rudder wheel angles of a multi-rudder wheel vehicle in situ, and a storage medium, the method determines an upper limit of the number of rudder wheels allowed to steer simultaneously according to the total number of rudder wheels, so that the number of rudder wheels kept fixed is not less than half of the total number; estimates the steering time required for each rudder wheel to turn to a target angle; selects rudder wheels to join a steering queue in order of steering time from long to short, so that the total number of rudder wheels in a steering state does not exceed the upper limit; when the number of candidate rudder wheels with the same steering time exceeds the remaining number that can be joined, selects a combination of rudder wheels that maximizes the dispersion degree of the geometric distribution of rudder wheels kept fixed; controls the rudder wheels in the queue to steer simultaneously, keeps the remaining rudder wheels continue to steer after any rudder wheel reaches the target angle, and re-executes the selection until all rudder wheels reach the target angle. The application maximizes the parallelism of rudder wheel steering while ensuring the stability of the vehicle body, significantly shortens the time consumed for steering the rudder angle in situ, and does not increase the hardware cost.

Description

Technical Field

[0001] This invention relates to the field of motion control for mobile robots, and more particularly to a method, system, and storage medium for controlling the steering wheel angle of a multi-steering wheel vehicle in place. Background Technology

[0002] Multi-steering wheel vehicles, as omnidirectional mobile platforms, are widely used in space-constrained industrial scenarios due to their omnidirectional movement capabilities within a plane (including lateral movement, diagonal movement, and rotation in place). Before performing a task, these vehicles typically need to rotate each steering wheel (drive wheel) to a specific target angle according to a planned path, without causing any displacement of the vehicle itself; this process is called "steering in place."

[0003] However, in practical applications, due to factors such as machining and assembly errors, uneven friction coefficients between tires and the ground, and unbalanced load distribution on the vehicle body, if all steering wheels are controlled to perform steering actions simultaneously, the frictional forces generated between each steering wheel and the ground will create complex couples and torques, which can easily lead to unexpected translational or swaying of the vehicle body. This will not only reduce the vehicle's positioning accuracy, but in severe cases, it may even damage cargo or cause safety accidents.

[0004] The simplest way to overcome the above phenomenon is to turn the steering wheel one by one, that is, to lock the other steering wheels in sequence and drive only one steering wheel at a time to ensure the absolute stability of the vehicle during the turning process. However, the drawback of this method is very obvious: its execution time is directly proportional to the number of steering wheels. The more steering wheels there are, the longer the total time takes to turn the steering wheel in place, which is extremely inefficient and seriously affects the robot's work cycle and overall throughput.

[0005] It is evident that among existing methods for turning steering wheels in place in multi-steering wheel vehicles, the method of turning all steering wheels simultaneously is the most efficient but has poor stability, while the method of turning each steering wheel individually has good stability but extremely low efficiency. Therefore, it is clear that stability and efficiency cannot be simultaneously achieved. Consequently, how to shorten the overall time required for turning steering wheels in place while ensuring vehicle stability, without relying on external sensors for positioning or increasing hardware costs, has become a pressing technical problem to be solved in this field. Summary of the Invention

[0006] The main objective of this invention is to provide a method, system, and storage medium for controlling the steering wheel angle of a multi-steering wheel vehicle in place. This method maximizes the parallelism of steering wheel steering while ensuring vehicle stability, and thus shortens the overall time required for in-place steering angle adjustment, without relying on external sensors for positioning or increasing hardware costs, by selecting and scheduling each steering wheel in batches.

[0007] To achieve the above objectives, according to one aspect of the present invention, a method for controlling the steering wheel angle of a multi-steering wheel vehicle in place is provided, the steps of which include:

[0008] Step S1: Determine the upper limit of the number of steering wheels that can turn simultaneously based on the total number of steering wheels on the vehicle body, so that the number of steering wheels that remain fixed during the turning process is not less than half of the total number;

[0009] Step S2: Estimate the turning time required for each steering wheel to turn from the current angle to the target angle;

[0010] Step S3: Select steering wheels from those that have not yet started turning and add them to the current batch's waiting-to-turn queue in descending order of turning time. The number of steering wheels added to the waiting-to-turn queue shall be limited to ensure that the total number of steering wheels in the turning state does not exceed the upper limit. Wherein, when the number of candidate steering wheels with the same turning time exceeds the remaining number that can be added, select the combination of steering wheels that maximizes the geometric distribution dispersion of the fixed steering wheels from the candidate steering wheels and add it to the waiting-to-turn queue.

[0011] Step S4: Control the steering wheels in the steering queue to turn simultaneously, and in response to any steering wheel that is turning reaching the target angle, keep the remaining steering wheels turning and return to step S3 until all steering wheels reach the target angle.

[0012] In a possible preferred embodiment, before estimating the turning time in step S2, the step further includes: determining the rotation direction of each steering wheel:

[0013] Determine whether the angles traversed during the process of rotating from the current angle to the target angle in an increasing manner and in a decreasing manner are both within the preset steering wheel angle range;

[0014] If both rotation methods are feasible, select the rotation direction with the smaller required rotation angle; if only one rotation method is feasible, select the feasible rotation direction; and estimate the turning time based on the rotation angle required by the selected rotation direction.

[0015] In a possible preferred embodiment, in step S2, the turning time is estimated using any one of T-shaped speed planning, S-shaped speed planning, or jerk-limited trajectory planning, based on the maximum angular velocity and maximum angular acceleration of the motor driving the steering wheel.

[0016] In a possible preferred embodiment, where T-type speed planning is employed, the turning time T is estimated using the following formula:

[0017] ;

[0018] in, The required rotation angle for the steering wheel. This is the maximum angular velocity of the motor. This is the maximum angular acceleration of the motor.

[0019] In a possible preferred embodiment, in step S3, the geometric distribution dispersion is the sum of the Euclidean distances between each pair of steering wheels in the vehicle coordinate system, keeping the distance constant:

[0020] ;

[0021] Where M represents the number of fixed steering wheels. , These are the position vectors of the i-th and j-th fixed steering wheels in the vehicle coordinate system, respectively.

[0022] In a possible preferred embodiment, step S3, the step of determining the geometric distribution dispersion includes: connecting the position points of each fixed steering wheel in the vehicle coordinate system in a circumferential order around the geometric center of the vehicle to form a supporting polygon, and using the area of ​​the supporting polygon as the geometric distribution dispersion.

[0023] In a possible preferred embodiment, step S3, the step of determining the geometric distribution dispersion includes: calculating the distance between the position of each fixed steering wheel in the vehicle coordinate system and the geometric center of the vehicle body, and using the standard deviation of each distance as the geometric distribution dispersion.

[0024] In a possible preferred embodiment, in step S4, in response to any steering wheel that is turning reaching the target angle, the steering wheels that have not reached the target angle are divided into a first steering wheel group that is turning and a second steering wheel group that has not started turning; the steering state of each steering wheel in the first steering wheel group remains unchanged and does not participate in the selection in step S3, and steps S3 and S4 are executed again for the steering wheels in the second steering wheel group, so that the steering wheels in the first steering wheel group turn in parallel with the newly selected steering wheels added to the steering queue.

[0025] To achieve the above objectives, according to another aspect of the present invention, a system for controlling the steering wheel angle of a multi-steering wheel vehicle in place is also provided, comprising:

[0026] The quantity determination module is used to determine the upper limit of the number of steering wheels that can be turned simultaneously based on the total number of steering wheels on the vehicle body, so that the number of steering wheels that remain fixed during the turning process is not less than half of the total number;

[0027] The time estimation module is used to estimate the turning time required for each steering wheel to turn from the current angle to the target angle;

[0028] The steering wheel selection module is used to select steering wheels from those that have not yet started turning, in descending order of turning time, and add them to the current batch's waiting-to-turn queue. The number of steering wheels added to the waiting-to-turn queue is limited to ensure that the total number of steering wheels in a turning state does not exceed the upper limit. When the number of candidate steering wheels with the same turning time exceeds the remaining number that can be added, the combination of steering wheels that maximizes the geometric distribution dispersion of the fixed steering wheels is selected from the candidate steering wheels and added to the waiting-to-turn queue.

[0029] The steering control module is used to control the steering wheels in the steering queue to turn simultaneously, and in response to any steering wheel that is turning reaching the target angle, to keep the remaining steering wheels turning and trigger the steering wheel selection module to re-execute the selection until all steering wheels reach the target angle.

[0030] To achieve the above objectives, according to another aspect of the present invention, a computer-readable storage medium is also provided, on which a computer program is stored, wherein the computer program, when executed by a processor, implements the method for controlling the steering wheel angle of a multi-steering wheel vehicle in place as described above.

[0031] The method, system, and storage medium for controlling the steering wheel angle of a multi-steering wheel vehicle in place provided by this invention have the following beneficial technical effects compared with the prior art:

[0032] Significantly improved efficiency: Compared with the traditional method of steering one by one, this invention uses a greedy scheduling strategy of batch parallelism and immediately triggers rescheduling after any steering wheel is in place to maintain full parallelism, which maximizes the use of the system's parallel processing capabilities. Especially on multi-steering wheel models with heavy loads (N≥4), the time spent on steering angle adjustment in place can be reduced by more than 50%.

[0033] Good stability: Through the hard constraint of fixing at least half of the wheels, and the optimization of maximizing the geometric distribution dispersion of the fixed steering wheels in the same batch selection, the algorithm ensures that the vehicle body always has stable mechanical support during parallel steering, effectively suppressing vehicle body displacement.

[0034] Good versatility: This invention does not depend on specific vehicle models or sensors and can be widely applied to multi-steering wheel omnidirectional mobile robot platforms with two-wheel drive, four-wheel drive and more wheels. Attached Figure Description

[0035] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0036] Figure 1 This is a schematic diagram of the method steps of the present invention;

[0037] Figure 2 This is a schematic diagram of the overall flow logic of the method of the present invention;

[0038] Figure 3 This is a schematic diagram of the rotational orientation of each steering wheel in a six-steering-wheel omnidirectional moving platform, as illustrated in the method example of this invention.

[0039] Figure 4 This is a schematic diagram of the system structure of the present invention. Detailed Implementation

[0040] To enable those skilled in the art to better understand the technical solutions of the present invention, the specific technical solutions of the present invention will be clearly and completely described below in conjunction with embodiments, so as to help those skilled in the art further understand the present invention. Obviously, the embodiments described in this application are merely some embodiments of the present invention, and not all embodiments. It should be noted that, for those skilled in the art, the embodiments and features in the embodiments of this application can be combined with each other without departing from the concept of the present invention and without conflict. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the disclosure and protection scope of the present invention.

[0041] Furthermore, the terms "first," "second," "S1," "S2," etc., used in the specification, claims, and drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such features can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those described herein. At the same time, the stages described in each step are not necessarily to be implemented in the same step; it should be understood that the implementation order of the contents of each step stage can be adjusted and interchanged without violating the inventive concept, so that embodiments of the invention described herein can be implemented in orders other than those described herein. Additionally, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. Unless otherwise expressly specified and limited, the terms "set," "arrange," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or a connection within two elements. Those skilled in the art can understand the specific meaning of the above terms in this case based on the specific circumstances and in conjunction with existing technology.

[0042] Multi-steering wheel vehicles, as omnidirectional mobile platforms, are widely used in space-constrained industrial scenarios due to their omnidirectional movement capabilities within a plane (including lateral movement, diagonal movement, and rotation in place). Before performing a task, these vehicles typically need to rotate each steering wheel (drive wheel) to a specific target angle according to a planned path, without causing any displacement of the vehicle itself; this process is called "steering in place."

[0043] The inventive concept of this invention lies in resolving the contradiction between stability and efficiency by scheduling and controlling the steering wheel process without relying on any additional hardware or external sensing positioning methods. Specifically, throughout the entire steering wheel's stationary steering process, at least half of the steering wheels are always constrained to remain fixed, providing stable mechanical support for the vehicle body. Under this hard constraint, batch selection is performed based on the steering wheel's steering time, prioritizing the steering wheel with the longest steering time for parallel execution. When multiple combinations of selections occur, a secondary selection is performed based on the criterion of maximizing the geometrical dispersion of the fixed steering wheels. Simultaneously, rescheduling is triggered immediately when any steering wheel reaches the target angle, supplementing it with a new steering wheel to ensure that the number of steering wheels in parallel steering is always maintained at the allowable upper limit, thereby achieving pipeline-style parallel scheduling.

[0044] Based on this concept, such as Figures 1 to 2 As shown, the present invention provides a method for controlling the steering wheel angle of a multi-steering wheel vehicle in place, and the implementation steps include:

[0045] Step S1: Determine the upper limit of the number of steering wheels that can be turned simultaneously based on the total number of steering wheels on the vehicle body, so that the number of steering wheels that remain fixed during the turning process is not less than half of the total number.

[0046] Specifically, when a multi-steering wheel vehicle adjusts its steering angle in place, friction is generated between the steering wheels involved in the steering and the ground, exerting a counterforce on the vehicle body. If all steering wheels turn synchronously, the aforementioned counterforce forms a complex couple and torque, which can easily cause unexpected translational or swaying of the vehicle body. To address this issue, this step determines the upper limit of the number of steering wheels that can be simultaneously steered based on the total number N of steering wheels on the vehicle body. While considering both stability and operational efficiency, when the number of steering wheels maintaining a fixed posture is not less than half of the total number of steering wheels, the static friction generated between the fixed steering wheels (hereinafter referred to as fixed wheels) and the ground can effectively counteract the counterforce generated by the steering wheels, thereby suppressing vehicle body displacement.

[0047] As a specific implementation method, let the minimum number of fixed steering wheels required when turning the rudder angle in place be... The maximum number of steering wheels that can rotate simultaneously is It is calculated according to formula (1):

[0048] ; (Formula 1)

[0049] Where N represents the total number of steering wheels in the vehicle body, and ceil represents the rounding up operation. The significance of this constraint is that at least half of the steering wheels must remain fixed when turning the rudder angle in place, thereby providing stable support for the vehicle body against the reaction force of the rotating wheels. For example, when the total number of steering wheels N is odd (such as N=5), rounding up makes the number of fixed wheels (3) more than the number of steering wheels allowed to turn simultaneously (2), thus further tilting this parallel constraint towards stability.

[0050] Step S2: Estimate the turning time required for each steering wheel to turn from the current angle to the target angle.

[0051] Specifically, since the batch scheduling in subsequent step S3 requires the turning time of each steering wheel as a quantitative decision-making basis, step S2 will estimate the turning time required for each steering wheel to turn from its current angle to the target angle. This estimation can be based on the current angle of each steering wheel. Target perspective Steering wheel angle range and the maximum angular velocity of the motor that drives the steering wheel. Maximum angular acceleration The process involves two steps: determining the direction of rotation and estimating the rotation time.

[0052] 1. Determining the direction of rotation

[0053] Because the steering wheel angle changes periodically during rotation, the target angle can be reached by rotating clockwise or counterclockwise. However, the mechanical structure of the steering wheel dictates that it cannot rotate continuously in one direction and must adhere to the constraints of the steering wheel angle range. Therefore, it is first necessary to determine the rotation direction that minimizes the change in steering wheel angle. Specifically:

[0054] Confirm the feasibility of clockwise rotation: Set the current angle The increment is continuously increased according to the preset angle step size until... If the angles during the accumulation process are all within the steering wheel angle range If the rotation is within the specified range, then clockwise rotation is considered feasible, and the required rotation angle is recorded; otherwise, the rotation direction is considered infeasible.

[0055] Confirm the feasibility of counter-clockwise rotation: Set the current angle Decrease continuously according to the preset angle step size until... If the angles during the decreasing process are all within the steering wheel angle range If the rotation direction is within the range, then counterclockwise rotation is considered feasible, and the required rotation angle is recorded; otherwise, the rotation direction is considered infeasible.

[0056] If both clockwise and counterclockwise rotation are feasible, choose the rotation direction with the smaller required rotation angle; if only one rotation direction is feasible, choose that direction. After confirming the steering wheel's rotation direction, the required rotation angle will be determined. It should be noted that if both rotation directions are not feasible, it may be due to an incorrect target angle or an incorrect initial angle, requiring exception handling. This invention will not elaborate on this situation.

[0057] 2. Estimation of rotation time

[0058] Rotate at the required angle and the maximum angular velocity of the motor Maximum angular acceleration Using T-shaped velocity planning, the required turning time for the steering wheel can be estimated. Under T-shaped velocity planning, the steering wheel's turning process involves acceleration, then constant speed, and finally deceleration. When the required rotation angle is large, the angular velocity reaches its maximum, and the turning time is calculated using a trapezoidal velocity curve of "acceleration-constant speed-deceleration." When the required rotation angle is small, deceleration is required before reaching the maximum angular velocity, and the turning time is calculated using a triangular velocity curve of "acceleration-deceleration." The critical angle for both scenarios is... Accordingly, turning time Calculate according to formula (2):

[0059] (Formula 2)

[0060] in, The required rotation angle for the steering wheel. This is the maximum angular velocity of the motor. This is the maximum angular acceleration of the motor.

[0061] As an alternative implementation, the speed planning algorithm described above is not limited to T-shaped speed planning. In practical applications, it can be replaced with S-shaped speed planning or a more advanced jerk-limited trajectory planning, depending on the performance of the motor driver, to estimate a smoother turning time.

[0062] Step S3: Select steering wheels from those that have not yet started turning and add them to the current batch's waiting-to-turn queue in descending order of turning time. The number of steering wheels added to the waiting-to-turn queue shall be limited to the total number of steering wheels in a turning state not exceeding the upper limit. Wherein, when the number of candidate steering wheels with the same turning time exceeds the remaining number that can be added, select the combination of steering wheels that maximizes the geometric distribution dispersion of the fixed steering wheels from the candidate steering wheels and add it to the waiting-to-turn queue.

[0063] Specifically, the greedy selection and stability optimization of the batch of steering wheels are illustrated in the following example:

[0064] 1. Steerable selection based on a greedy strategy

[0065] This step involves arranging all steering wheels according to their turning time. Sort in descending order, using the upper limit of quantity determined in step S1. To determine the upper limit of single-batch processing capacity, a greedy strategy is used to select the wheel with the longest current processing time from all the steering wheels. Each steering wheel serves as the first queue of wheels to be turned. The selection logic is as follows: traverse the sorted steering wheels in descending order of their turn times, and add them to the queue in turn until the queue is full. One. During this process, the following three situations may occur:

[0066] Scenario 1: If the number of steering wheels corresponding to the current time consumption is exactly equal to the remaining required number, then all of them are selected, and the combination for the current batch is determined;

[0067] Scenario 2: If the number of steering wheels corresponding to the current time consumption is less than the remaining required number, then all of them are selected and the selection continues to the next time consumption tier.

[0068] Scenario 3: If the number of steering wheels corresponding to the current time consumption is greater than the remaining required number (i.e., a time conflict occurs), the following stability optimization is triggered: select the required number of steering wheels from the candidate steering wheels in this time consumption echelon to maximize the dispersion of the fixed wheels, thereby determining the current batch combination.

[0069] The principle behind this greedy strategy is that the total time taken for batch parallel execution depends on the bottleneck wheel that takes the longest time in this batch. Therefore, by prioritizing the execution of the wheel that takes the longest time in the first round, these wheels can overlap with other shorter-timed wheels on the time axis to the greatest extent, thereby shortening the overall completion time.

[0070] 2. Optimal selection of rudder wheels from the same batch based on stability.

[0071] In the above selection process, because the turning time of different steering wheels may be the same, it leads to the need for selection beforehand. There may be multiple combinations of individual steering wheels, so a stability criterion is introduced for secondary screening. The steering wheels that are not selected in the current batch are defined as fixed wheels. The more dispersed the geometric distribution of the fixed wheels in the vehicle coordinate system, the more stable the support they provide to the vehicle body, and the higher the stability of the vehicle body when facing the reaction force of the rotating wheels.

[0072] To quantify this dispersion, this embodiment defines a cost value D, which is calculated as follows: calculate the pairwise Euclidean distances between all fixed wheels and sum these distances. The larger the sum, the more dispersed the distribution of fixed wheels, and the higher the stability of the vehicle body.

[0073] (Formula 3)

[0074] Where M is the number of fixed wheels. and These are the position vectors of the fixed wheels in the vehicle coordinate system.

[0075] When determining the current batch combination, iterate through all combinations that meet the quantity requirement (i.e. The invention selects candidate steering wheel combinations (number of combinations), calculates the dispersion of the corresponding fixed wheels for each combination, and selects the combination with the largest dispersion value as the steering wheel combination for actual control of rotation in the current batch. Thus, the invention uses "steering time" as the primary indicator for batch division (greedy scheduling) and "vehicle stability (dispersion)" as the optimization indicator in the selection of the same batch, forming a two-layer control logic that takes into account both efficiency and safety.

[0076] As an alternative implementation, the aforementioned "sum of pairwise Euclidean distances" can also employ other quantification standards to characterize dispersion, achieving the same goal of selecting the optimal combination. For example:

[0077] (1) Using the area of ​​the supporting polygon as the geometric distribution dispersion: For example, the position points of each fixed steering wheel in the vehicle coordinate system are connected in the circumferential order around the geometric center of the vehicle body (i.e., in ascending order of the polar angle relative to the geometric center of the vehicle body) to form a supporting polygon, and the area of ​​the supporting polygon is used as the geometric distribution dispersion.

[0078] As a specific calculation method, sorting the M fixed wheel positions yields an ordered vertex sequence. The area is calculated using the shoelace formula:

[0079]

[0080] in The larger the area of ​​the supporting polygon, the larger the support area formed by the fixed wheelset on the vehicle body, and the stronger the vehicle body's resistance to overturning and disturbance.

[0081] (2) Using the standard deviation of the distance between the fixed wheel position and the geometric center of the vehicle body as the geometric distribution dispersion: calculate the position of each fixed steering wheel in the vehicle body coordinate system relative to the geometric center of the vehicle body. Distance between The standard deviation of each distance:

[0082]

[0083] As the geometric distribution dispersion, where For each distance The average value. It should be noted that this index is a simplified optional index with less computational complexity; if all fixed wheels are exactly evenly distributed on the same circumference with the geometric center of the vehicle body as the center, its standard deviation will approach zero, which does not match the actual stability. Therefore, in scenarios where the distribution of fixed wheels is relatively regular, the sum of pairwise Euclidean distances or the area of ​​the supporting polygon should be used as the dispersion index.

[0084] Step S4: Control the steering wheels in the steering queue to turn simultaneously, and in response to any steering wheel that is turning reaching the target angle, keep the remaining steering wheels turning and return to step S3 until all steering wheels reach the target angle.

[0085] Specifically, when controlling the selected steering wheels in the current batch to perform steering actions simultaneously, since the steering times of each steering wheel are different, the steering wheels in the same batch will not arrive at their positions at the same time. If the next batch is started only after all the steering wheels in the current batch have arrived at their positions, the parallel quota corresponding to the steering wheels that arrived earlier will be idle, reducing overall efficiency. To address this, the present invention adopts a dynamic rescheduling mechanism triggered by completion events: once any steering wheel reaches the target angle, dynamic rescheduling is immediately triggered, and the specific process is as follows.

[0086] 1. Complete event triggering and state update.

[0087] The rotation status of each steering wheel in the current batch is monitored in real time. When a steering wheel in the current batch is detected to have reached the target angle, the completed steering wheel is removed from the set of uncompleted steering wheels and marked as completed. If there are other uncompleted steering wheels in the current batch, they are allowed to continue rotating without interrupting their current action. The remaining time for each currently rotating steering wheel is recorded.

[0088] 2. Group rescheduling

[0089] Based on the updated set of incomplete steering wheels, the steering wheels are divided into two groups: Group A (steering wheels currently rotating) and Group B (steering wheels not yet rotating). Group A retains its current rotation state and does not participate in the new round of sorting and selection to avoid time loss and mechanical shock caused by frequent starts and stops; Group B is sorted according to theoretical time consumption. Sort in descending order, The upper limit is set, and the steering wheel with the longest current time is selected from the sorting results and added to the new round of the steering queue. If a time conflict occurs (multiple steering wheels with the same time consumption, resulting in the number of candidates exceeding the remaining number that can be added), the above stability optimization is re-executed, the dispersion D of the fixed wheel (the steering wheel not in the steering queue) under each candidate combination is calculated, and the combination that maximizes the dispersion is selected as the rotating wheel actually controlled in this round.

[0090] 3. Start the new batch of steering wheels

[0091] The newly selected steering wheel is started to rotate. At this time, there may be two types of steering wheels in the vehicle: those from the previous batch that were not yet completed (Group A, continuing to rotate) and the newly started steering wheel (starting to rotate). The two types of steering wheels operate in parallel without interfering with each other. Throughout the entire process, the number of rotating steering wheels is always kept below a certain limit. At the same time, ensure that the number of fixed wheels is not less than This means that the hard stability constraint still holds after each rescheduling.

[0092] 4. Execute in a loop

[0093] Repeat the process of triggering the completion event, rescheduling the group, and starting a new batch. Each time a steering wheel completes its task, a rescheduling is triggered, ensuring the system can continuously maintain [its functionality]. The individual steering wheels operate in parallel, achieving a pipeline-style parallel scheduling until the unfinished steering wheel assembly is empty, all steering wheels have reached the target angle, and the stationary steering angle process ends.

[0094] Application example (six-wheel omnidirectional moving platform example)

[0095] like Figure 3 As shown in the figure, this example illustrates a six-steering-wheel omnidirectional moving platform. The position distribution, initial angle, and target angle of the six steering wheels in the vehicle coordinate system are shown in Table 1 below: Table 1. Steering wheel position distribution and initial and target angles.

[0096] 1 (-0.50, 0.45) 0 90 2 (0.00, 0.50) 0 90 3 (0.50, 0.45) -30 90 4 (-0.50, -0.45) -30 90 5 (0.00, -0.50) 30 90 6 (0.50, -0.45) 30 90

[0097] The performance parameters of each steering wheel drive motor are consistent: maximum angular velocity Maximum angular acceleration The mechanical limit range of the steering wheel is... The angle is 1° from the walking distance.

[0098] Step S1: According to formula (1), N=6, we can obtain = 3, = 3, meaning that a maximum of 3 steering wheels can be controlled to turn at the same time, and at least 3 steering wheels must be kept fixed.

[0099] Step S2: Calculate the critical angle according to formula (2) = = 60² / 30 = 120°. Taking steering wheel 1 as an example: Initial angle = 0°, target angle = 90°, steering wheel angle range Clockwise rotation: Increasing from 0° in 1° increments to 90°, the angle remains within the steering wheel angle range, therefore feasible. Counterclockwise rotation: Decreasing from 0° in 1° increments, the angle exceeds the steering wheel angle range when it decreases to -46°, therefore not feasible. Therefore, clockwise rotation is chosen. Calculate according to formula (2) By analogy, we can calculate that: T1 = T2 = 3.464s, T3 = T4 = 4.0s, T5 = T6 = 2.828s.

[0100] Step S3: Sort by turning time in descending order, resulting in T3 = T4 > T1 = T2 > T5 = T6. Since... = 3. Following a greedy strategy, prioritize selecting the steering wheels with the longest time consumption: The first tier (4.0s) has two steering wheels, 3 and 4, both of which must be selected; the second tier (3.464s) has two steering wheels, 1 and 2, from which 3-2 = 1 must be selected, resulting in a time conflict. Therefore, the first round of candidate rotating wheel combinations has only two possibilities: Combination A (rotating wheels are steering wheels 3, 4, and 1; fixed wheels are steering wheels 2, 5, and 6) and Combination B (rotating wheels are steering wheels 3, 4, and 2; fixed wheels are steering wheels 1, 5, and 6).

[0101] Stability optimization: Calculate the dispersion of the fixed wheel under the two combinations according to formula (3).

[0102] Combination A: The fixed wheels are steering wheels 2, 5, and 6, with positions P2 = (0.00, 0.50), P5 = (0.00, -0.50), and P6 = (0.50, -0.45) respectively. ;

[0103] Combination B: The fixed wheels are steering wheels 1, 5, and 6, with positions P1 = (-0.50, 0.45), P5 = (0.00, -0.50), and P6 = (0.50, -0.45) respectively. .

[0104] because We select combination B, which has a higher degree of dispersion, as the first rotating wheel combination.

[0105] Step S4: The iterative control process is as follows.

[0106] First round of execution: Control wheel 3, wheel 4, and wheel 2 start rotating simultaneously, with time taken for T3 = T4 = 4.0s and T2 = 3.464s respectively. After 3.464s, wheel 2 reaches the target angle first. At this time, wheel 3 and wheel 4 are still 4.0 - 3.464 = 0.536s away from completing the execution. Wheel 2 is removed from the set of unfinished wheel steers. At this time, group A consists of {wheel 3 (0.536s remaining, currently rotating), wheel 4 (0.536s remaining, currently rotating)}, and group B consists of {wheel 1 (3.464s, not rotating), wheel 5 (2.828s, not rotating), wheel 6 (2.828s, not rotating)}.

[0107] Second round of execution: Select the steering wheel 1 with the longest execution time from group B to start steering. At this time, the total number of steering wheels in the steering state is still 3, which satisfies the requirement. Constraints. After 0.536s, steering wheels 3 and 4 reach the target angle. At this time, steering wheel 1 is still 3.464 - 0.536 = 2.928s away from completing its operation. Steering wheels 3 and 4 are removed from the set of steering wheels that have not yet completed their operation. At this point, group A consists of {steering wheel 1 (2.928s remaining, currently rotating)}, and group B consists of {steering wheel 5 (2.828s, not rotating) and steering wheel 6 (2.828s, not rotating)}.

[0108] Third round of execution: Select steering wheel 5 and steering wheel 6 from group B to initiate steering. Since steering wheels 5 and 6 take the same amount of time and the remaining number that can be added is 2 ( -1 = 2), both are selected, so there is no need to trigger the discrete optimization. After 2.828s, steering wheels 5 and 6 reach the target angle. At this time, steering wheel 1 is still 2.928-2.828 = 0.1s away from completing the execution.

[0109] Fourth round of execution: At this point, only steering wheel 1 has not yet been executed. After 0.1 seconds, steering wheel 1 is executed, all steering wheels have reached the target angle, and the stationary steering angle process ends.

[0110] The total time is 3.464 + 0.536 + 2.828 + 0.1 = 6.928s; if the traditional method of ruddering one by one is used, the time required is 3.464 + 3.464 + 4.0 + 4.0 + 2.828 + 2.828 = 20.584s. In comparison, the efficiency improvement of this example is (20.584-6.928) / 20.584 ≈ 66.3%.

[0111] On the other hand, corresponding to the above method examples, such as Figure 4 As shown, the present invention also provides a system for controlling the steering wheel angle of a multi-steering wheel vehicle in place, examples of which include:

[0112] The quantity determination module is used to determine the upper limit of the number of steering wheels that can be turned simultaneously based on the total number of steering wheels on the vehicle body, so that the number of steering wheels that remain fixed during the turning process is not less than half of the total number;

[0113] The time estimation module is used to estimate the turning time required for each steering wheel to turn from the current angle to the target angle;

[0114] The steering wheel selection module is used to select steering wheels from those that have not yet started turning, in descending order of turning time, and add them to the current batch's waiting-to-turn queue. The number of steering wheels added to the waiting-to-turn queue is limited to ensure that the total number of steering wheels in a turning state does not exceed the upper limit. When the number of candidate steering wheels with the same turning time exceeds the remaining number that can be added, the combination of steering wheels that maximizes the geometric distribution dispersion of the fixed steering wheels is selected from the candidate steering wheels and added to the waiting-to-turn queue.

[0115] The steering control module is used to control the steering wheels in the steering queue to turn simultaneously, and in response to any steering wheel that is turning reaching the target angle, to keep the remaining steering wheels turning and trigger the steering wheel selection module to re-execute the selection until all steering wheels reach the target angle.

[0116] The above system embodiments and method embodiments are based on the same inventive concept. The specific execution logic of each module can be referred to the description of the corresponding steps in the method embodiments. The technical effects they can achieve are also the same, and will not be repeated here.

[0117] In summary, as can be seen from the above methods and system examples, the concept of this invention lies in using "at least half of the steering wheels remain fixed" as a hard constraint on stability throughout the entire steering process. Under this constraint, a batch decision-making mechanism with dual time and stability objectives is constructed. Specifically, steering time is used as the primary indicator for batch division, and greedy scheduling is used to maximize the overlap of the bottleneck steering wheels with the longest time consumption on the time axis. The geometric distribution dispersion of fixed wheels is used as the optimization indicator for selecting the same batch, so that the vehicle body always has stable mechanical support during parallel steering. Dynamic rescheduling triggered when any steering wheel is in place is used as a closed-loop control method to keep the number of steering wheels that can be steered in parallel at the upper limit of the allowable limit, forming a pipeline-style parallel scheduling.

[0118] This concept overcomes the technical bottlenecks of instability in fully parallel systems and low efficiency in fully serial systems. Without relying on external sensors for positioning or increasing hardware costs, it achieves a balance between stability and efficiency solely through control algorithms. Compared to individual steering, the time required for steering angle adjustment in stationary positions for high-load (N≥4) multi-steering-wheel vehicles can be reduced by more than 50% (approximately 66.3% in the above example). Compared to fully parallel systems, the vehicle body maintains at least half of its fixed wheels providing mechanical support throughout the steering process, effectively suppressing unintended translational and swaying movements. Furthermore, this invention does not rely on specific vehicle models or sensors and can be widely applied to two-wheel drive, four-wheel drive, and multi-steering-wheel omnidirectional mobile robot platforms with more wheels. It is also applicable to multi-differential-module vehicles, demonstrating good versatility.

[0119] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The present invention is limited only by the claims and their full scope and equivalents. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

[0120] Those skilled in the art will understand that, besides implementing the system, apparatus, unit, and its modules provided by this invention in purely computer-readable program code, the same program can be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system, apparatus, and its modules provided by this invention can be considered a hardware component, and the modules included therein for implementing various programs can also be considered structures within the hardware component; alternatively, modules for implementing various functions can be considered both software programs implementing the method and structures within the hardware component.

[0121] Furthermore, all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. This program is stored in a storage medium and includes several instructions to cause a microcontroller, chip, or processor to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0122] Furthermore, various different implementations of the present invention can be combined arbitrarily, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed in the present invention.

Claims

1. A method for controlling the steering wheel angle of a multi-steering wheel vehicle in place, comprising the following steps: Step S1: Determine the upper limit of the number of steering wheels that can turn simultaneously based on the total number of steering wheels on the vehicle body, so that the number of steering wheels that remain fixed during the turning process is not less than half of the total number; Step S2: Estimate the turning time required for each steering wheel to turn from the current angle to the target angle; Step S3: Select steering wheels from those that have not yet started turning and add them to the current batch's waiting-to-turn queue in descending order of turning time. The number of steering wheels added to the waiting-to-turn queue shall be limited to ensure that the total number of steering wheels in the turning state does not exceed the upper limit. Wherein, when the number of candidate steering wheels with the same turning time exceeds the remaining number that can be added, select the combination of steering wheels that maximizes the geometric distribution dispersion of the fixed steering wheels from the candidate steering wheels and add it to the waiting-to-turn queue. Step S4: Control the steering wheels in the steering queue to turn simultaneously, and in response to any steering wheel that is turning reaching the target angle, keep the remaining steering wheels turning and return to step S3 until all steering wheels reach the target angle.

2. The method for controlling the steering wheel angle of a multi-steering wheel vehicle in place according to claim 1, wherein before estimating the turning time in step S2, the step further includes: Determine the rotation direction of each steering wheel: Determine whether the angles traversed during the process of rotating from the current angle to the target angle in an increasing manner and in a decreasing manner are both within the preset steering wheel angle range; If both rotation methods are feasible, select the rotation direction with the smaller required rotation angle; if only one rotation method is feasible, select the feasible rotation direction; and estimate the turning time based on the rotation angle required by the selected rotation direction.

3. The method for controlling the steering wheel angle of a multi-steering wheel vehicle in place according to claim 2, in step S2, the turning time is estimated by any one of T-shaped speed planning, S-shaped speed planning, or jerk-limited trajectory planning based on the maximum angular velocity and maximum angular acceleration of the motor driving the steering wheel.

4. The method for controlling the steering wheel angle of a multi-steering wheel vehicle in place according to claim 3, wherein when using T-shaped speed planning, the turning time T is estimated by the following formula: ； in, Δθ is the angle that the steering wheel needs to rotate. This is the maximum angular velocity of the motor. This is the maximum angular acceleration of the motor.

5. The method for controlling the steering wheel angle of a multi-steering wheel vehicle in place according to any one of claims 1 to 4, wherein in step S3, the geometric distribution dispersion is the sum of the Euclidean distances between each pair of steering wheels in the vehicle coordinate system, which are kept fixed: ； in, M represents maintaining a fixed number of steering wheels. , These are the position vectors of the i-th and j-th fixed steering wheels in the vehicle coordinate system, respectively.

6. The method for controlling the steering wheel angle of a multi-steering wheel vehicle in place according to any one of claims 1 to 4, wherein the step of determining the geometric distribution dispersion in step S3 includes: The fixed positions of each steering wheel in the vehicle coordinate system are connected sequentially in a circumferential order around the geometric center of the vehicle to form a supporting polygon, and the area of ​​the supporting polygon is used as the geometric distribution dispersion.

7. The method for controlling the steering wheel angle of a multi-steering wheel vehicle in place according to any one of claims 1 to 4, wherein the step of determining the geometric distribution dispersion in step S3 includes: Calculate the distance between the position of each fixed steering wheel in the vehicle coordinate system and the geometric center of the vehicle body, and use the standard deviation of each distance as the geometric distribution dispersion.

8. The method for controlling the steering wheel angle of a multi-steering wheel vehicle in place according to claim 1, in step S4, in response to any steering wheel that is turning reaching the target angle, the steering wheels that have not reached the target angle are divided into a first steering wheel group that is turning and a second steering wheel group that has not started turning; the steering state of each steering wheel in the first steering wheel group remains unchanged and does not participate in the selection in step S3, and steps S3 and S4 are executed again for the steering wheels in the second steering wheel group, so that the steering wheels in the first steering wheel group turn in parallel with the newly selected steering wheels added to the steering queue.

9. A system for controlling the steering wheel angle of a multi-steering wheel vehicle in place, comprising: The quantity determination module is used to determine the upper limit of the number of steering wheels that can turn simultaneously based on the total number of steering wheels on the vehicle body, so that the number of steering wheels that remain fixed during the turning process is not less than half of the total number; The time estimation module is used to estimate the turning time required for each steering wheel to turn from the current angle to the target angle; The steering wheel selection module is used to select steering wheels from those that have not yet started turning, in descending order of turning time, and add them to the current batch's waiting-to-turn queue. The number of steering wheels added to the waiting-to-turn queue is limited to ensure that the total number of steering wheels in a turning state does not exceed the upper limit. When the number of candidate steering wheels with the same turning time exceeds the remaining number that can be added, the combination of steering wheels that maximizes the geometric distribution dispersion of the fixed steering wheels is selected from the candidate steering wheels and added to the waiting-to-turn queue. The steering control module is used to control the steering wheels in the steering queue to turn simultaneously, and in response to any steering wheel that is turning reaching the target angle, to keep the remaining steering wheels turning and trigger the steering wheel selection module to re-execute the selection until all steering wheels reach the target angle.

10. A computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the method for controlling the steering wheel angle of a multi-steering wheel vehicle in place as described in any one of claims 1 to 8.

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