Multi-rudder calibration method, device and storage medium

Abstract

The application discloses a multi-rudder calibration method and device and a storage medium. The multi-rudder calibration method comprises the following steps: constructing a conversion relationship between the motion state of each rudder and the motion state of a vehicle body, and obtaining motion model parameters; moving the vehicle body according to a motion instruction, calculating estimated pose parameters based on the motion model parameters and the motion speed and motion angle of each rudder in the motion instruction; obtaining actual pose parameters after the vehicle body moves, performing difference calculation on the estimated pose parameters and the actual pose parameters, and obtaining pose residuals; and updating the rudder zero offsets of each rudder by using the pose residuals, and obtaining target rudder zero offsets of the final calibration of each rudder. The scheme is suitable for odometer calibration of a multi-rudder vehicle type. Through deduction of the conversion process of multi-rudder encoders and the motion state of a vehicle body, the vehicle body pose can be solved according to odometer data, and then the zero offset is adjusted through difference calculation of the actual pose parameters, so that the accuracy of the zero offset adjustment is improved.

Description

Technical Field

[0001] This application relates to the field of sensor calibration technology, and in particular to a multi-steering wheel calibration method, device and storage medium. Background Technology

[0002] The widespread application of mobile robots, such as Automated Guided Vehicles (AGVs) and robotic vacuum cleaners, across various industries has led to a rapid increase in demand. However, due to mechanical installation errors, mobile robots have a constant zero-angle steering wheel. When the steering wheel angle is zero, the mobile robot cannot travel in a straight line and will slightly turn to one side. Therefore, it is necessary to calibrate the angle deviation of each steering wheel in the mobile robot.

[0003] Traditional steering wheel calibration methods rely on machine manufacturing processes or manual calibration, and the calibration results mainly depend on the subjective experience of technicians, which can lead to inaccurate calibration results.

[0004] Therefore, how to accurately calibrate the steering wheel of a mobile robot has become an urgent problem to be solved. Summary of the Invention

[0005] To address the aforementioned technical problems, this application provides at least one method, apparatus, and storage medium for calibrating multiple steering wheels.

[0006] The first aspect of this application provides a multi-steering wheel calibration method, which includes: constructing a conversion relationship between the motion state of each steering wheel and the motion state of the vehicle body to obtain motion model parameters; wherein, the motion state includes motion speed and motion angle; instructing the vehicle body to move according to a motion command, the motion command containing the motion speed and motion angle of each steering wheel, the motion angle of the steering wheel being the sum of a preset command angle and the steering wheel zero bias; calculating the pose parameters of the vehicle body after movement based on the motion model parameters and the motion speed and motion angle of each steering wheel in the motion command to obtain the estimated pose parameters; obtaining the actual pose parameters of the vehicle body after movement, calculating the difference between the estimated pose parameters and the actual pose parameters to obtain the pose residual; and updating the steering wheel zero bias of each steering wheel using the pose residual to obtain the final calibrated target steering wheel zero bias of each steering wheel.

[0007] In one embodiment, the transformation relationship between the motion state of each steering wheel and the motion state of the vehicle body is constructed to obtain motion model parameters, including: obtaining the line connecting the center of each steering wheel to the center of the vehicle body and the angle of the line in the vehicle body coordinate system; based on the line corresponding to each steering wheel and the angle corresponding to the line, constructing the transformation matrix between the motion state of each steering wheel and the motion state of the vehicle body to obtain motion model parameters.

[0008] In one embodiment, the motion state of the vehicle body includes linear velocity and angular velocity. Based on the motion model parameters and the motion speed and motion angle of each steering wheel in the motion command, the pose parameters of the vehicle body after movement are calculated to obtain the estimated pose parameters. This includes: using the motion model parameters to convert and calculate the motion speed and motion angle of each steering wheel in the motion command to obtain the linear velocity and angular velocity of the vehicle body; calculating the angle change value of the vehicle body within a preset time period based on the angular velocity of the vehicle body; calculating the position change value of the vehicle body within a preset time period based on the linear velocity and angle change value of the vehicle body; and combining the angle change value and the position change value to calculate the pose parameters of the vehicle body after movement to obtain the estimated pose parameters.

[0009] In one embodiment, the pose parameters include position parameters and angle parameters; calculating the difference between the estimated pose parameters and the actual pose parameters to obtain the pose residual includes: calculating the difference between the angle parameters in the estimated pose parameters and the angle parameters in the actual pose parameters to obtain the angle residual; and calculating the difference between the position parameters in the estimated pose parameters and the position parameters in the actual pose parameters to obtain the position residual.

[0010] In one embodiment, the current zero bias of each steering wheel is updated using the pose residual to obtain the final target zero bias of each steering wheel. This includes: grouping each steering wheel into groups containing two steering wheels to be calibrated; wherein the two steering wheels in the same group contribute equally to the angular velocity of the vehicle body; taking any one steering wheel in the group as the steering wheel to be aligned and the other steering wheel as the reference steering wheel, keeping the zero bias of the reference steering wheel unchanged, and updating the zero bias of the steering wheel to be aligned based on the angle residual; if the zero bias of the steering wheel to be aligned is aligned with the running trajectory of the reference steering wheel, then the zero bias of the reference steering wheel and the steering wheel to be aligned are updated synchronously based on the position residual to obtain the final target zero bias of each steering wheel in the group to be calibrated.

[0011] In one embodiment, the vehicle body includes four steering wheels, with two steering wheels located diagonally assigned to a steering wheel group to be calibrated.

[0012] In one embodiment, updating the zero-bias of the steering wheel to be aligned based on the angular residual includes: solving for the optimal zero-bias of the steering wheel to be aligned using the least squares method, where the sum of squares of the angular residuals corresponding to the optimal zero-bias of the steering wheel to be aligned is minimized; updating the zero-bias of the steering wheel to be aligned based on the optimal zero-bias of the steering wheel to be aligned; and synchronously updating the zero-bias of the reference steering wheel and the steering wheel to be aligned based on the position residual includes: solving for the optimal zero-bias of the reference steering wheel using the least squares method, where the inner product of the position residuals corresponding to the optimal zero-bias of the reference steering wheel is minimized; and updating the zero-bias of the reference steering wheel and the steering wheel to be aligned based on the optimal zero-bias of the reference steering wheel.

[0013] In one embodiment, there are multiple motion commands, each with a different motion angle and a different motion path. The pose residual is used to update the current zero bias of each steering wheel to obtain the final target zero bias of each steering wheel. This includes: obtaining the pose residual calculated for each motion path; and updating the current zero bias of each steering wheel by combining the pose residual for each motion path to obtain the final target zero bias of each steering wheel.

[0014] The second aspect of this application provides a multi-steering wheel calibration device, comprising: a conversion relationship construction module for constructing a conversion relationship between the motion state of each steering wheel and the motion state of the vehicle body, thereby obtaining motion model parameters; wherein the motion state includes motion speed and motion angle; a motion instruction module for instructing the vehicle body to move according to motion commands, wherein the motion commands contain the motion speed and motion angle of each steering wheel, and the motion angle of the steering wheel is the sum of a preset command angle and the steering wheel zero bias; a pose estimation module for calculating the pose parameters of the vehicle body after movement based on the motion model parameters and the motion speed and motion angle of each steering wheel in the motion commands, thereby obtaining estimated pose parameters; a residual calculation module for obtaining the actual pose parameters of the vehicle body after movement, performing difference calculation between the estimated pose parameters and the actual pose parameters, thereby obtaining a pose residual; and a zero bias update module for updating the steering wheel zero bias of each steering wheel using the pose residual, thereby obtaining the final calibrated target steering wheel zero bias of each steering wheel.

[0015] A third aspect of this application provides an electronic device, including a memory and a processor, wherein the processor is used to execute program instructions stored in the memory to implement the above-described multi-steering wheel calibration method.

[0016] The fourth aspect of this application provides a computer-readable storage medium having program instructions stored thereon, which, when executed by a processor, implement the above-described multi-steering wheel calibration method.

[0017] The above scheme obtains motion model parameters by constructing the conversion relationship between the motion states of each steering wheel and the motion state of the vehicle body; it moves the vehicle body according to motion commands, which contain the motion speed and motion angle of each steering wheel; based on the motion model parameters and the motion speed and motion angle of each steering wheel in the motion commands, it calculates the pose parameters of the vehicle body after movement, obtaining the estimated pose parameters; it obtains the actual pose parameters of the vehicle body after movement, calculates the difference between the estimated pose parameters and the actual pose parameters, and obtains the pose residual; it uses the pose residual to update the steering wheel zero bias of each steering wheel, obtaining the final calibrated target steering wheel zero bias of each steering wheel. This scheme is suitable for odometer calibration of multi-steering wheel vehicles. By deriving the conversion process between the multi-steering wheel encoder and the vehicle body motion state, the vehicle body pose can be calculated based on the odometer data, and then the difference between the odometer data and the actual pose parameters can be calculated to adjust the zero bias, improving the accuracy of the zero bias adjustment.

[0018] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this application. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with this application and, together with the specification, serve to explain the technical solutions of this application.

[0020] Figure 1 This is a flowchart illustrating a multi-steering wheel calibration method as shown in an exemplary embodiment of this application;

[0021] Figure 2 This is a schematic diagram illustrating zero-bias steering wheel in an exemplary embodiment of this application;

[0022] Figure 3 This is a schematic diagram illustrating the kinematic relationship between the steering wheel and the vehicle body, as shown in an exemplary embodiment of this application;

[0023] Figure 4 This is a schematic diagram illustrating multiple motion paths in an exemplary embodiment of this application;

[0024] Figure 5 This is a block diagram illustrating a multi-steering wheel calibration device according to an exemplary embodiment of this application;

[0025] Figure 6 This is a schematic diagram of the structure of an electronic device shown in an exemplary embodiment of this application;

[0026] Figure 7 This is a schematic diagram illustrating the structure of a computer-readable storage medium, as shown in an exemplary embodiment of this application. Detailed Implementation

[0027] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0028] In the following description, specific details such as particular system architectures, interfaces, and technologies are presented for illustrative purposes rather than for limiting purposes, in order to provide a thorough understanding of this application.

[0029] In this document, the term "and / or" is merely a description of the association information of related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship. Furthermore, "many" in this document means two or more. Moreover, the term "at least one" in this document means any combination of at least two of any one or more of a plurality of elements. For example, including at least one of A, B, and C can mean including any one or more elements selected from the set consisting of A, B, and C.

[0030] The multi-steering wheel calibration method provided in the embodiments of this application is described below.

[0031] The multi-steering wheel calibration method can be specifically executed by the vehicle body. Of course, the multi-steering wheel calibration method can also be specifically executed by other devices, such as when the vehicle body and the server are connected in communication. The multi-steering wheel calibration method can be specifically executed by the server, or the vehicle body and the server can cooperate to execute it. That is, some steps of the method are executed by the vehicle body and other steps are executed by the server. This embodiment does not limit the specific subject of execution of the method.

[0032] Please see Figure 1 , Figure 1 This is a flowchart illustrating a multi-steering wheel calibration method as shown in an exemplary embodiment of this application, such as... Figure 1 As shown, the multi-steering wheel calibration method includes at least steps S110 to S150, which are described in detail below:

[0033] Step S110: Construct the transformation relationship between the motion state of each steering wheel and the motion state of the vehicle body to obtain motion model parameters; wherein, the motion state includes motion speed and motion angle.

[0034] The vehicle body is equipped with multiple steering wheels. The vehicle body can be an Automated Guided Vehicle (AGV) or a mobile robot such as a sweeping robot. The steering wheels drive the movement of the vehicle body. It should be noted that the steering wheels to be specified in this application are drive wheels with driving force.

[0035] Establish the transformation relationship between the motion state of each steering wheel and the motion state of the vehicle body, and use it as the parameters of the motion model.

[0036] The motion state includes motion speed and motion angle. Motion speed is used to characterize the travel speed of the steering wheel or vehicle body, which may include the linear velocity of the steering wheel or vehicle body as a whole, or the velocity component of the steering wheel or vehicle body in a specific direction. Motion angle is used to characterize the travel direction of the steering wheel or vehicle body, which may include a specific angle value, or the rate of change of angle, i.e., angular velocity.

[0037] The motion model parameters constructed in this application can be used to calculate the motion state of the vehicle body based on the motion state transformation of each steering wheel.

[0038] Step S120: Move the vehicle body according to the motion command. The motion command contains the motion speed and motion angle of each steering wheel. The motion angle of the steering wheel is the sum of the preset command angle and the zero offset of the steering wheel.

[0039] In the ideal model, the steering wheel installation angle is consistent with the vehicle's forward direction. However, in actual applications, the steering wheel installation angle may have an angular deviation. The angle between the steering wheel installation angle and the vehicle's forward direction is called the steering wheel zero offset. By combining the preset command angle and the steering wheel zero offset, the final motion angle of the steering wheel is determined.

[0040] For example, please see Figure 2 , Figure 2 This is a schematic diagram illustrating zero deflection of the steering wheel in an exemplary embodiment of this application, as shown below. Figure 2 As shown, the vehicle body is equipped with four steering wheels. The zero offset of the four steering wheels is represented by θ1, θ2, θ3, and θ4 respectively. If counterclockwise is set as positive, then θ1, θ3, and θ4 are positive, and θ2 is negative.

[0041] It should be noted that before the steering wheel zero offset calibration, the steering wheel zero offset used in the motion angle can be a preset value, such as 0°. When the steering wheel zero offset calibration is performed, the steering wheel zero offset used in the motion angle is the latest updated value. After the steering wheel zero offset calibration is completed, the motion angle of each steering wheel is calculated using the target steering wheel zero offset obtained from its corresponding calibration.

[0042] Step S130: Based on the motion model parameters and the motion speed and motion angle of each steering wheel in the motion command, calculate the vehicle's pose and obtain the estimated pose parameters.

[0043] According to the motion command, the motion speed and angle of each steering wheel can be known. Then, based on the conversion relationship between the motion state of each steering wheel and the motion state of the vehicle body in the pre-built motion model parameters, the motion speed and angle of each steering wheel are converted and calculated to obtain the motion speed and angle of the vehicle body. Then, based on the motion speed and angle of the vehicle body, the pose parameters of the vehicle body after movement can be calculated and used as the estimated pose parameters. The estimated pose parameters refer to the pose parameters of the vehicle body derived from the motion speed and angle of the steering wheels.

[0044] The vehicle body's pose parameters can be the vehicle body's position and / or its angle. The vehicle body's pose parameters can also be the change in the vehicle body's position and / or the change in its angle. This application does not limit these parameters.

[0045] Step S140: Obtain the actual pose parameters after the vehicle body moves, calculate the difference between the estimated pose parameters and the actual pose parameters, and obtain the pose residual.

[0046] The actual pose parameters of the vehicle body can be detected by environmental perception devices deployed on the vehicle body, including but not limited to lidar, vision cameras, depth cameras, etc.

[0047] For example, Figure 2 The vehicle shown is equipped with a lidar system. The lidar collects environmental information, which is then matched with a prior map to obtain the vehicle's actual pose parameters.

[0048] Similarly, the actual pose parameters of the vehicle body can be the actual position and / or the actual angle of the vehicle body. The actual pose parameters of the vehicle body can also be the actual position change and / or the actual angle change of the vehicle body. This application does not limit this.

[0049] The difference between the estimated pose parameters and the actual pose parameters is calculated to obtain the pose residual.

[0050] The position residual reflects the difference between the vehicle body position calculated based on the steering wheel's motion state and the actual position. It reflects the difference between the vehicle body's desired position and the actual position after the steering wheel moves according to the motion angle in the motion command. Based on this, the steering wheel's motion angle can be corrected.

[0051] Step S150: Update the zero bias of each steering wheel using the pose residual to obtain the final target zero bias of each steering wheel.

[0052] The zero bias of the steering wheel is calculated based on the pose residual, and the steering wheel zero bias is updated. In the next cycle, the motion angle is calculated using the updated steering wheel zero bias. The above steps are repeated to iteratively update the zero bias of the steering wheel until the update termination condition is met. Then, the final calibrated target steering wheel zero bias of each steering wheel is output.

[0053] The update termination condition can be either the pose residual being less than or equal to a preset residual threshold, or the number of iterations being greater than or equal to a preset number threshold.

[0054] The following describes some embodiments of this application in detail.

[0055] In some implementations, step S110 involves establishing the conversion relationship between the motion state of each steering wheel and the motion state of the vehicle body to obtain motion model parameters, including the following steps S111 to S112.

[0056] Step S111: Obtain the line connecting the center of each steering wheel to the center of the vehicle body, and the angle of the line in the vehicle body coordinate system.

[0057] Among them, the line connecting the center of the steering wheel and the center of the vehicle body, and the angle of the line in the vehicle body coordinate system are known scalars.

[0058] Step S112: Based on the lines and angles corresponding to each steering wheel, construct the transformation matrix between the motion state of each steering wheel and the motion state of the vehicle body to obtain the motion model parameters.

[0059] For example, given k steering wheels, and the rotational speed n of each steering wheel... i and angle The linear velocity of the vehicle body can be obtained by solving the motion model parameters. and angular velocity ω o , where i is an integer greater than or equal to 1 and less than or equal to k, and o refers to the center of the vehicle body.

[0060] For an example illustrating the derivation process of the motion model parameters, please refer to [link / reference]. Figure 3 , Figure 3 This is a schematic diagram illustrating the kinematic relationship between the steering wheel and the vehicle body, as shown in an exemplary embodiment of this application. Figure 3 As shown, since the steering wheels and the chassis are rigidly connected, each steering wheel has the same speed υ as the chassis. o Additionally, due to the angular velocity of the vehicle body, the line R connecting the center of the i-th steering wheel and the center of the vehicle body... i Velocity in the vertical direction Furthermore, its direction satisfies the right-hand rule. Therefore, for each steering wheel, the following relationship exists as shown in Formula 1:

[0061]

[0062] Among them, v i The calculated actual speed of the steering wheel.

[0063] Converting the vector equation in Formula 1 into a computable matrix form yields Formula 2:

[0064]

[0065] In formula 2, It is the angle of the vector from the center of the vehicle body to the steering wheel in the vehicle coordinate system. like Figure 3As shown, a and b are the horizontal and vertical coordinates of the steering wheel center in the vehicle coordinate system, with the vehicle coordinate system originating from the vehicle center; v ox and v oy The respective vehicle speeds υ o Components on the x-axis and y-axis.

[0066] By combining k steering wheels and expanding Equation 2, we can obtain the following Equation 3:

[0067]

[0068] Among them, by controlling the rotational speed n of each steering wheel i The speed of the steering wheel is obtained by multiplying the speed by the radius r.

[0069] Then, the steering wheel motion state vector on the left side of Equation 3 is denoted as... The first matrix on the right-hand side of the equation is the transformation matrix, denoted as A; the second matrix on the right-hand side is the vehicle motion state vector to be solved, denoted as... Then Formula 3 as a whole can be written as Multiply both sides of the equation by A T Formula 4 can be obtained as follows:

[0070]

[0071] Multiply both sides of equation (4) by (A) T A) -1 Formula 5 can be obtained as follows:

[0072]

[0073] The final solution is as follows Right now

[0074] The above formula provides a kinematic forward solution calculation method for multi-steering wheel systems, and derives the conversion process between the steering wheel encoder and the vehicle speed in the multi-steering wheel motion model, which facilitates subsequent steering wheel calibration calculations.

[0075] The steering wheels are driven by motion commands to move the vehicle body. These motion commands can be linear open-loop speed commands; however, due to inconsistent zero-bias on the steering wheels, the vehicle's trajectory is an arc rather than a straight line.

[0076] In some implementations, the motion state of the vehicle body includes linear velocity and angular velocity, and the estimated pose parameters are the changes in the pose of the vehicle body; in step S130, based on the motion model parameters and the motion speed and motion angle of each steering wheel in the motion command, the pose parameters of the vehicle body after movement are calculated to obtain the estimated pose parameters, including the following steps S131 to S134.

[0077] Step S131: Using the motion model parameters, convert and calculate the motion speed and motion angle of each steering wheel in the motion command to obtain the linear velocity and angular velocity of the vehicle body.

[0078] For example, taking four steering wheels as an example, the preset command angle of each steering wheel is: Let the current zero bias of each steering wheel be represented as θ1, θ2, θ3, and θ4, respectively. Then, according to the formula...

[0079] After superimposing the zero-bias equations for each steering wheel in Equation 4, we obtain the following Equation 6:

[0080]

[0081] Transforming Formula 6, we obtain the angular velocity ω of the vehicle body. o This is expressed as Formula 7 below:

[0082]

[0083] In this context, the subscript 3 indicates the third row of the matrix.

[0084] Similarly, the linear velocity of the vehicle body can be obtained using Formula 6.

[0085] Step S132: Calculate the angle change of the vehicle body within a preset time period based on the angular velocity of the vehicle body.

[0086] Specifically, the angular velocity and the duration of the preset time period are multiplied to obtain the angular change value of the vehicle body within the preset time period.

[0087] Step S133: Calculate the position change of the vehicle body within a preset time period based on the linear velocity and angle change values ​​of the vehicle body.

[0088] Specifically, an angle change matrix is ​​constructed based on the angle change value. The angle change matrix, linear velocity, and the duration of the preset time period are multiplied to obtain the position change value of the vehicle body within the preset time period.

[0089] Step S134: Calculate the vehicle's pose by combining the angle change value and the position change value to obtain the estimated pose parameters.

[0090] For example, through step S131 above, the linear velocity of the vehicle body during the preset time period Δt is known. and angular velocity ω o Then the change in the angle of the vehicle body θ within the time interval Δt. o This can be expressed as Formula 8 below:

[0091] θ o =ω o ·Δt (Formula 8)

[0092] Change in vehicle position over time Δt This is expressed as Formula 9 below:

[0093]

[0094] Then calculate the pose parameter T o This is expressed as formula 10 below:

[0095]

[0096] In Formula 10, the rotation matrix

[0097] Then, the actual pose parameters after the vehicle body moves are obtained, and the difference between the estimated pose parameters and the actual pose parameters is calculated to obtain the pose residual.

[0098] In some implementations, the pose parameters include position parameters and angle parameters; in step S140, the difference between the calculated pose parameters and the actual pose parameters is calculated to obtain the pose residual, including the following steps S141 and S142.

[0099] Step S141: Calculate the difference between the angle parameters in the estimated pose parameters and the angle parameters in the actual pose parameters to obtain the angle residual.

[0100] Step S142: Calculate the difference between the position parameters in the estimated pose parameters and the position parameters in the actual pose parameters to obtain the position residual.

[0101] The position parameters can be the position of the vehicle in a preset coordinate system (such as a map coordinate system) and / or the angle of the vehicle. The pose parameters of the vehicle can also be the change in position and / or the change in angle of the vehicle.

[0102] Taking the vehicle's pose parameters as the changes in position and angle of the vehicle as an example, where the position parameter is the change in position and the angle parameter is the change in angle, the difference between the calculated angle change in the pose parameters and the actual angle change in the pose parameters is calculated to obtain the angle residual. Similarly, the difference between the calculated position change in the pose parameters and the actual position change in the pose parameters is calculated to obtain the position residual.

[0103] Using the aforementioned angular and positional residuals, the zero bias of each steering wheel is updated to obtain the final target zero bias of each steering wheel.

[0104] The goal of updating the steering wheel zero bias is to minimize the angular and position residuals. Specifically, methods such as least squares and regularized regression can be used to find the optimal solution for the steering wheel zero bias, thus achieving the update.

[0105] In some implementations, there are multiple motion commands, each corresponding to a different motion angle and a different motion path. For example, please refer to [link to relevant documentation]. Figure 4 , Figure 4 This is a schematic diagram of multiple motion paths shown in an exemplary embodiment of this application. The pose residual calculated for each motion path is obtained. The pose residual corresponding to each motion path is combined to update the current zero bias of each steering wheel, so as to obtain the target zero bias of each steering wheel finally calibrated.

[0106] For example, the set of actual pose parameters calculated for each motion path can be represented as: The set of inferred pose parameters calculated for each motion path is represented as follows: Where m refers to the number of motion paths, such as Figure 4 There are 7 movement paths. Indicates the actual pose parameters. This indicates the calculated pose parameters. For the calculation method of the calculated pose parameters, please refer to Formulas 6 to 8.

[0107] The difference between the actual pose parameters and the estimated pose parameters corresponding to each of the above motion paths is calculated. The calculated pose residual is then used to update the current zero bias of each steering wheel based on the pose residual corresponding to each motion path.

[0108] In some implementations, step S150 updates the current zero bias of each steering wheel using the pose residual to obtain the final target zero bias of each steering wheel, including steps S151 to S153 below.

[0109] Step S151: Group the various steering wheels to obtain a group of steering wheels to be calibrated containing two steering wheels; wherein, the two steering wheels in the same group of steering wheels to be calibrated contribute the same amount to the angular velocity of the vehicle body.

[0110] For example, such as Figure 2 As shown, the vehicle body includes four steering wheels. Two steering wheels located diagonally are divided into a group of steering wheels to be calibrated, that is, steering wheel 1 and steering wheel 4 are divided into a group of steering wheels to be calibrated, and steering wheel 2 and steering wheel 3 are divided into a group of steering wheels to be calibrated.

[0111] Step S152: Take any one of the steering wheels in the steering wheel group to be calibrated as the steering wheel to be aligned, and the other steering wheel as the reference steering wheel. Keep the zero bias of the reference steering wheel unchanged, and update the zero bias of the steering wheel to be aligned based on the angle residual.

[0112] When the zero bias of each set of steering wheels is inconsistent, such as Figure 2When θ1≠θ4 and θ2≠θ3, a linear open-loop velocity is issued to the vehicle body. At this time, the vehicle body is not moving in a straight line but in an arc.

[0113] Therefore, the steering wheels in the same steering wheel group to be calibrated are first adjusted to zero relative bias so that the running trajectories of each steering wheel in the same steering wheel group are aligned.

[0114] Specifically, when adjusting the relative zero bias of the steering wheels in the same group, any one of the steering wheels in the group to be calibrated is taken as the steering wheel to be aligned, and the other steering wheel is taken as the reference steering wheel. The zero bias of the reference steering wheel remains unchanged, and the zero bias of the steering wheel to be aligned is updated based on the angle residual.

[0115] For example, updating the zero bias of the steering wheel to be aligned based on the angle residual includes: using the least squares method to solve for the optimal zero bias of the steering wheel to be aligned, where the sum of squares of the angle residuals corresponding to the optimal zero bias of the steering wheel to be aligned is minimized; and updating the zero bias of the steering wheel to be aligned based on the optimal zero bias of the steering wheel to be aligned.

[0116] For example, the actual pose parameters of the vehicle body are calculated using environmental point data collected by the lidar. Since the vehicle's motion on the horizontal plane is two-dimensional and the lidar and vehicle body are rigidly connected, ideally, the angle rotated by the steering wheel per unit time should be the same as the angle rotated by the lidar. If the angle rotated by the lidar in time Δt is calculated from the environmental point data collected by the lidar... S Furthermore, the angle change value θ derived from the motion state of the steering wheel is obtained by calculating using formulas 6 to 8 above. O Ideally, θ S Should be with θ O They are equal, but due to the inconsistent zero bias of each steering wheel, θ S and θ O Different, for θ S and θ O The angle residual is obtained by performing difference calculation.

[0117] For example, if there are multiple motion paths corresponding to the calculated actual pose parameters And calculate pose parameters The angular residual Δθ can then be calculated using the following formula 11:

[0118]

[0119] Where m is the number of motion paths.

[0120] The optimal zero-bias of the steering wheels to be aligned is solved using the least squares method.

[0121] like Figure 2The steering wheels 1 and 4 are divided into one group of steering wheels to be calibrated, and the steering wheels 2 and 3 are divided into another group of steering wheels to be calibrated. The zero biases of steering wheels 1 to 4 are represented as θ1, θ2, θ3, and θ4, respectively. The least squares method can be used to solve for the zero biases. During the solution process, θ1 = θ2 = 0 are fixed, and the objective function is expressed as shown in Formula 12 below:

[0122]

[0123] The initial value of the zero bias of each steering wheel is θ = 0. After each solution, the zero bias of the steering wheel is updated to θ = θ + Δθ, and the updated zero bias of the steering wheel is used to compensate for the steering wheel angle in the open-loop velocity during the next travel.

[0124] repeat Figure 4 As shown in the walking process, the zero bias of the steering wheel to be aligned is continuously updated iteratively. After the iteration update is completed, θ1≈θ4 and θ2≈θ3, so that the vehicle body will not exhibit curved motion after traveling a straight path.

[0125] Step S153: If the zero bias of the steering wheel to be aligned is aligned with the running trajectory of the reference steering wheel, then the zero bias of the reference steering wheel and the steering wheel to be aligned is updated synchronously based on the position residual, so as to obtain the final target steering wheel zero bias of each steering wheel in the steering wheel group to be calibrated.

[0126] After the relative zero bias adjustment is completed, the absolute zero bias adjustment is then performed.

[0127] For example, updating the zero bias of the reference steering wheel and the steering wheel to be aligned synchronously based on the position residual includes: solving for the optimal zero bias of the reference steering wheel using the least squares method, where the inner product of the position residuals corresponding to the optimal zero bias of the reference steering wheel is minimized; and updating the zero bias of the reference steering wheel and the steering wheel to be aligned based on the optimal zero bias of the reference steering wheel.

[0128] For example, after iteratively updating the zero bias of the steering wheel to be aligned based on Formula 12 and converging, an absolute zero bias adjustment is then performed, that is, θ1 and θ2 are adjusted, and θ3 and θ4 are adjusted synchronously.

[0129] Specifically, using the actual pose parameters and estimated pose parameters of the last run of the steering wheel after zero-bias convergence, if the actual pose parameters are calculated from point cloud data collected by lidar, then the lidar extrinsic parameters can be used. For the actual pose parameters T S A coordinate system transformation is performed, where O represents the coordinate system corresponding to the steering wheel and S represents the coordinate system corresponding to the lidar. The actual pose parameter transformation process can be expressed as the following formula 13:

[0130]

[0131] Among them, T O ′ represents the pose after coordinate system transformation, which contains angle and position parameters. Let T be the coordinate system transformation parameter. O From the position parameters in ', the actual position parameters can be obtained.

[0132] Since the zero bias of the steering wheel to be aligned converges, θ O ≈0, therefore, simplifying formula 9 yields the following formula 14:

[0133]

[0134] Among them, t l This represents the l-th time period, where l ranges from i to j; This indicates the linear velocity of the vehicle body at the corresponding timestamp.

[0135] Extending Formula 14 to the m-segment motion path, the position residual is then calculated. The method can be found in Formula 15 below:

[0136]

[0137] Similarly, the solution obtained using the least squares method is... The objective function is expressed as shown in Formula 16 below:

[0138]

[0139] Based on Equation 16, θ1 and θ2 are obtained, and θ3 = θ3 + θ2 and θ4 = θ4 + θ1 are updated synchronously.

[0140] It should be noted that the above embodiments mainly use the case of four steering wheels as an example. However, in actual application scenarios, the solution of this application can also be used in calibration scenarios with other numbers of steering wheels, and this application does not limit it.

[0141] By performing relative and absolute zero-bias adjustments in stages, the zero-bias of all steering wheels can be obtained, thus achieving odometer calibration and improving the accuracy of multi-steering wheel calibration.

[0142] The multi-steering wheel calibration method provided in this application obtains motion model parameters by constructing the transformation relationship between the motion state of each steering wheel and the motion state of the vehicle body; the vehicle body moves according to motion commands, which contain the motion speed and motion angle of each steering wheel; based on the motion model parameters and the motion speed and motion angle of each steering wheel in the motion commands, the pose parameters of the vehicle body after movement are calculated to obtain the estimated pose parameters; the actual pose parameters of the vehicle body after movement are obtained, and the difference between the estimated pose parameters and the actual pose parameters is calculated to obtain the pose residual; the pose residual is used to update the steering wheel zero bias of each steering wheel to obtain the final calibrated target steering wheel zero bias of each steering wheel. This method is applicable to the calibration of odometers for multi-steering wheel vehicles. By deriving the transformation process between the multi-steering wheel encoder and the motion state of the vehicle body, the vehicle body pose can be calculated based on the odometer data, and then the difference between the odometer data and the actual pose parameters can be calculated to adjust the zero bias, thereby improving the accuracy of the zero bias adjustment.

[0143] Figure 5 This is a block diagram illustrating a multi-steering wheel calibration device according to an exemplary embodiment of this application. Figure 5 As shown, the exemplary multi-steering wheel calibration device 500 includes:

[0144] The transformation relationship construction module 510 is used to construct the transformation relationship between the motion state of each steering wheel and the motion state of the vehicle body, and obtain the motion model parameters; wherein, the motion state includes motion speed and motion angle;

[0145] The motion instruction module 520 is used to instruct the vehicle body to move according to the motion command. The motion command contains the motion speed and motion angle of each steering wheel. The motion angle of the steering wheel is the sum of the preset command angle and the zero offset of the steering wheel.

[0146] The pose estimation module 530 is used to calculate the pose parameters of the vehicle body after it moves based on the motion model parameters and the motion speed and motion angle of each steering wheel in the motion command, and to obtain the estimated pose parameters.

[0147] The residual calculation module 540 is used to obtain the actual pose parameters after the vehicle body moves, and to calculate the difference between the estimated pose parameters and the actual pose parameters to obtain the pose residual.

[0148] The zero-bias update module 550 is used to update the zero bias of each steering wheel using the pose residual, so as to obtain the final target steering wheel zero bias of each steering wheel.

[0149] It should be noted that the multi-steering wheel calibration device and the multi-steering wheel calibration method provided in the above embodiments belong to the same concept. The specific operation methods of each module and unit have been described in detail in the method embodiments and will not be repeated here. In practical applications, the multi-steering wheel calibration device provided in the above embodiments can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. This is not a limitation.

[0150] Please see Figure 6 , Figure 6 This is a schematic diagram illustrating the structure of an electronic device in an exemplary embodiment of this application. The electronic device 600 includes a memory 601 and a processor 602. The processor 602 executes program instructions stored in the memory 601 to implement the steps in any of the above-described multi-steering wheel calibration method embodiments. In a specific implementation scenario, the electronic device 600 may include, but is not limited to, mobile robots, microcomputers, servers, laptops, tablets, etc., and is not limited thereto.

[0151] Specifically, processor 602 controls itself and memory 601 to implement the steps in any of the above-described multi-steering wheel calibration method embodiments. Processor 602 can also be referred to as a Central Processing Unit (CPU). Processor 602 may be an integrated circuit chip with signal processing capabilities. Processor 602 can also be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. A general-purpose processor can be a microprocessor or any conventional processor. Furthermore, processor 602 can be implemented using integrated circuit chips.

[0152] Please see Figure 7 , Figure 7 This is a schematic diagram illustrating the structure of a computer-readable storage medium in an exemplary embodiment of this application. The computer-readable storage medium 700 stores program instructions 710 that can be executed by a processor. The program instructions 710 are used to implement the steps in any of the above-described embodiments of the multi-steering wheel calibration method.

[0153] In some embodiments, the functions or modules of the apparatus provided in this disclosure can be used to perform the methods described in the above method embodiments. The specific implementation can be referred to the description of the above method embodiments, and for the sake of brevity, it will not be repeated here.

[0154] The description of the various embodiments above tends to emphasize the differences between the various embodiments. The similarities or similarities between them can be referred to, and for the sake of brevity, they will not be repeated here.

[0155] In the several embodiments provided in this application, it should be understood that the disclosed methods and apparatus can be implemented in other ways. For example, the apparatus implementations described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection of devices or units may be electrical, mechanical, or other forms.

[0156] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) or processor to execute all or part of the steps of the methods in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

Claims

1. A method for calibrating multiple steering wheels, characterized in that, The vehicle body is equipped with multiple steering wheels, and the method includes: The transformation relationship between the motion states of each steering wheel and the motion state of the vehicle body is constructed to obtain the motion model parameters; wherein, the motion state includes motion speed and motion angle; The vehicle body moves according to the motion command, which includes the motion speed and motion angle of each steering wheel. The motion angle of each steering wheel is the sum of the preset command angle and the zero offset of the steering wheel. Based on the motion model parameters and the motion speed and motion angle of each steering wheel in the motion command, the position and posture parameters of the vehicle body after movement are calculated to obtain the estimated position and posture parameters. The actual pose parameters of the vehicle body after movement are obtained, and the difference between the estimated pose parameters and the actual pose parameters is calculated to obtain the pose residual. The zero bias of each steering wheel is updated using the pose residual to obtain the final target zero bias of each steering wheel. The goal of updating the zero bias of the steering wheel is to reduce the pose residual. The update termination condition includes the pose residual being less than or equal to a preset residual threshold, or the number of iterations being greater than or equal to a preset number threshold.

2. The method according to claim 1, characterized in that, The process of constructing the transformation relationship between the motion states of each steering wheel and the motion state of the vehicle body yields motion model parameters, including: Obtain the line connecting the center of each steering wheel to the center of the vehicle body, and the angle of the line in the vehicle body coordinate system; Based on the lines connecting each steering wheel and the angles corresponding to those lines, a transformation matrix is ​​constructed between the motion states of each steering wheel and the motion states of the vehicle body, thus obtaining motion model parameters.

3. The method according to claim 1, characterized in that, The motion state of the vehicle body includes linear velocity and angular velocity; based on the motion model parameters and the motion velocity and motion angle of each steering wheel in the motion command, the pose parameters of the vehicle body after movement are calculated to obtain the estimated pose parameters, including: Using the motion model parameters, the motion speed and motion angle of each steering wheel in the motion command are converted and calculated to obtain the linear velocity and angular velocity of the vehicle body; Based on the angular velocity of the vehicle body, calculate the angular change value of the vehicle body within a preset time period; Based on the linear velocity of the vehicle body and the angle change value, calculate the position change value of the vehicle body within a preset time period; The pose parameters of the vehicle body after movement are calculated by combining the angle change value and the position change value, and the estimated pose parameters are obtained.

4. The method according to claim 1, characterized in that, The pose parameters include position parameters and angle parameters; the step of calculating the difference between the calculated pose parameters and the actual pose parameters to obtain the pose residual includes: The angle residual is obtained by calculating the difference between the angle parameters in the estimated pose parameters and the angle parameters in the actual pose parameters. The position residual is obtained by calculating the difference between the position parameters in the estimated pose parameters and the position parameters in the actual pose parameters.

5. The method according to claim 4, characterized in that, The step of updating the current zero bias of each steering wheel using the pose residual to obtain the final target zero bias of each steering wheel includes: The individual steering wheels are grouped to obtain a steering wheel group to be calibrated containing two steering wheels; wherein, the two steering wheels in the same steering wheel group to be calibrated contribute the same amount to the angular velocity of the vehicle body. Take any one of the steering wheels in the steering wheel group to be calibrated as the steering wheel to be aligned, and the other steering wheel as the reference steering wheel. Keep the zero bias of the reference steering wheel unchanged, and update the zero bias of the steering wheel to be aligned based on the angle residual. If the zero bias of the steering wheel to be aligned is aligned with the running trajectory of the reference steering wheel, then the zero bias of the reference steering wheel and the steering wheel to be aligned is updated synchronously based on the position residual, so as to obtain the final target steering wheel zero bias of each steering wheel in the steering wheel group to be calibrated.

6. The method according to claim 5, characterized in that, The vehicle body includes four steering wheels, with two steering wheels located diagonally assigned to a group of steering wheels to be calibrated.

7. The method according to claim 5, characterized in that, The step of updating the zero bias of the steering wheel to be aligned based on the angular residual includes: The optimal zero bias of the steering wheel to be aligned is obtained by using the least squares method, and the sum of the squares of the angular residuals corresponding to the optimal zero bias of the steering wheel to be aligned is minimized. Based on the optimal zero bias of the steering wheel to be aligned, update the zero bias of the steering wheel to be aligned; The step of synchronously updating the zero bias of the reference steering wheel and the steering wheel to be aligned based on the position residual includes: The optimal zero bias of the reference steering wheel is obtained by using the least squares method, and the inner product of the position residuals corresponding to the optimal zero bias of the reference steering wheel is minimized. Based on the optimal zero bias of the reference steering wheel, update the zero bias of both the reference steering wheel and the steering wheel to be aligned.

8. The method according to any one of claims 1 to 7, characterized in that, The number of motion commands is multiple, with different motion angles and different motion paths corresponding to different motion commands; the step of updating the current zero bias of each steering wheel using the pose residual to obtain the final calibrated target zero bias of each steering wheel includes: Obtain the calculated pose residual for each motion path; By combining the pose residuals corresponding to each motion path, the current zero bias of each steering wheel is updated to obtain the final target zero bias of each steering wheel.

9. An electronic device, characterized in that, The electronic device includes a memory and a processor, the processor being configured to execute program instructions stored in the memory to implement the steps of the method as described in any one of claims 1-8.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores program instructions that can be executed by a processor to implement the steps of the method as described in any one of claims 1-8.

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