Omnidirectional mobile robot, kinematics solution and control method and device thereof

Abstract

The present invention discloses an omnidirectional mobile robot, its kinematic solution and control method and device. The solution and control method includes: 1) solving and obtaining the target deflection angle of the decoupled active universal caster; 2) obtaining the actual deflection angle of the decoupled active universal caster; 3) calculating the deviation angle between the target deflection angle and the actual deflection angle; 4) when the absolute value of the deviation angle is greater than π / 2, deflecting the decoupled active universal caster toward the target deflection angle at a preset deflection speed in advance for a preset time length. The kinematic solution and control method of the omnidirectional mobile robot provided by the present invention controls the decoupled active universal caster to deflect in advance at a preset deflection speed by judging the size of the deviation angle to be deflected, thereby avoiding the situation where the wheels of the mobile robot suddenly turn or the control direction is inaccurate, thereby avoiding the reduction of accuracy or vibration of the omnidirectional mobile robot.

Description

Technical Field

[0001] The present invention belongs to the field of robotics and relates to a decoupled omnidirectional mobile robot, and in particular to an omnidirectional mobile robot, a kinematic calculation and control method and a device thereof. Background Art

[0002] Compared with traditional mobile robots, decoupled omnidirectional mobile robots can realize omnidirectional movement, have high flexibility, and can move in different narrow areas. Therefore, they are widely used in warehousing and logistics, machinery manufacturing, military and other fields.

[0003] Unlike traditional mobile robots, in order to achieve omnidirectional movement, this type of robot usually achieves omnidirectional movement by adjusting the deflection direction of each wheel on the chassis, and adjusting the deflection direction of the wheels on the chassis requires kinematic solution.

[0004] For such robots, singularities can occur at certain locations during kinematic calculations. This means that when mapping the robot's velocity space to its joint space, multiple solutions exist in the joint space. If the kinematic solution is not chosen correctly, the robot's wheels may suddenly turn or its control direction may be inaccurate, resulting in reduced accuracy or vibration. Therefore, preventing these singularities has become a pressing technical issue in this field. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention aims to provide an omnidirectional mobile robot, and a kinematic solution and control method and device thereof.

[0006] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0007] In a first aspect, the present invention provides a kinematic solution and control method for an omnidirectional mobile robot, wherein the omnidirectional mobile robot includes a plurality of decoupled active universal casters, and the kinematic solution and control method includes:

[0008] 1) Calculating and obtaining a target deflection angle of the decoupled active universal caster;

[0009] 2) obtaining an actual deflection angle of the decoupled active universal caster;

[0010] 3) calculating the deviation angle between the target deflection angle and the actual deflection angle;

[0011] 4) When the absolute value of the deviation angle is greater than π / 2, the decoupled active universal caster is deflected toward the target deflection angle at a preset deflection speed in advance for a preset time length.

[0012] In a second aspect, the present invention also provides a kinematic solution and control device for an omnidirectional mobile robot, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is run by the processor, the steps of the above-mentioned kinematic solution and control method are executed.

[0013] In a third aspect, the present invention further provides an omnidirectional mobile robot, comprising a robot chassis, decoupled active universal casters, and the above-mentioned kinematic solution and control device;

[0014] The decoupled active universal caster is arranged on the robot chassis and can be controlled by the kinematic solution and control device to deflect and roll relative to the robot chassis.

[0015] Based on the above technical solution, compared with the prior art, the beneficial effects of the present invention include at least:

[0016] The kinematic solution and control method of the omnidirectional mobile robot provided by the present invention controls the decoupled active universal casters to deflect in advance at a preset deflection speed by judging the size of the deviation angle to be deflected, thereby avoiding the sudden turning of the wheels of the mobile robot or the inaccurate control direction, thereby avoiding the reduction of accuracy or vibration of the omnidirectional mobile robot.

[0017] The above description is only an overview of the technical solution of the present invention. In order to enable those skilled in the art to more clearly understand the technical means of this application and implement them according to the contents of the specification, the following is an explanation of the preferred embodiments of the present invention with detailed drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic structural diagram of a decoupled active universal caster provided by a typical embodiment of the present invention;

[0019] Figure 2 This is a schematic structural diagram of an omnidirectional mobile robot provided by a typical embodiment of the present invention;

[0020] Figure 3 This is a flow chart of a kinematic solution and control method for an omnidirectional mobile robot provided by a typical embodiment of the present invention;

[0021] Description of reference numerals: 10, wheel carrier; 11, axle carrier; 12, roller; 13, steering drive motor; 14, rolling drive motor; 15, differential;

[0022] 20. Robot chassis. DETAILED DESCRIPTION

[0023] In view of the deficiencies in the prior art, the inventors of this case have proposed the technical solution of the present invention after long-term research and extensive practice, which can be summarized as follows: establishing an inverse kinematics model of a decoupled omnidirectional mobile robot. The calculation of this model is simple and clear, laying a good foundation for subsequent control methods. After obtaining the speed of the workspace, the angles at which the four casters reach the target position are predicted based on inverse kinematics; when the angle between the predicted position and the actual deflection position is greater than π / 2, and the steering speed of the active universal caster is within a set limit range, a smaller speed is sent to the deflection motor of the active universal caster in advance to allow it to turn in advance, thereby avoiding the sudden turning of the deflection motor at a higher speed, thereby reducing the possibility of sudden vibration of the mobile robot. The technical solution, its implementation process and principles will be further explained below.

[0024] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0025] Moreover, relational terms such as “first” and “second” are merely used to distinguish one component or method step from another with the same name, but do not necessarily require or imply any actual relationship or order between these components or method steps.

[0026] First see Figure 1-Figure 3 An embodiment of the present invention provides a kinematics solution and control method for an omnidirectional mobile robot, wherein the omnidirectional mobile robot includes a plurality of decoupled active universal casters. The kinematics solution and control method includes the following steps:

[0027] 1) Calculate and obtain the target deflection angle of the decoupled active universal caster.

[0028] 2) Obtaining the actual deflection angle of the decoupled active universal caster.

[0029] 3) Calculate the deviation angle between the target deflection angle and the actual deflection angle.

[0030] 4) When the absolute value of the deviation angle is greater than π / 2, a preset time length is set in advance to allow the decoupled active universal caster to deflect toward the target deflection angle at a preset deflection speed, wherein the preset time length = (absolute value of the deviation angle - π / 2) / preset deflection speed.

[0031] The above-described kinematic calculation and control method is primarily used to improve the smoothness of decoupled active swivel casters with offsets. Of course, as described below, it can also be applied to unbiased decoupled active swivel casters. The omnidirectional mobile robot employs at least two decoupled active swivel casters. As specific application examples, the kinematic algorithm may include: establishing an inverse kinematic model of the omnidirectional mobile robot based on the caster offsets and calculating the angles at which the four casters reach the target position based on the inverse kinematic model; and, when the calculated theoretical target position deviates from the actual current position of the casters by more than π / 2, pre-sending a smaller deflection speed value based on the direction of the deviation to the decoupled active swivel caster's yaw motor. This prediction and control method can prevent this type of omnidirectional mobile robot from experiencing a situation where the casters do not deflect at low speeds, but suddenly swerve when the vehicle reaches higher speeds.

[0032] When the decoupled active universal caster deflects to a certain position, and the given speed direction at this time forms an angle of π with the current deflection direction of the universal wheel, this is a singularity point. The solution and control method provided by the present invention can allow the decoupled active universal caster of the omnidirectional mobile robot to avoid this singularity point in advance.

[0033] The kinematic solution and control method provided by the present invention enables the omnidirectional mobile robot to always ensure that the decoupled active universal casters rotate to the opposite direction of the omnidirectional mobile robot's movement after obtaining instructions for various motion states. This method can improve the stability of the mobile robot, and the algorithm is simple and easy to implement.

[0034] In some embodiments, in step 1), the target deflection angle of the decoupled active universal caster can be obtained by solving an inverse kinematics model based on the current position and the target position of the omnidirectional mobile robot.

[0035] In some embodiments, the omnidirectional mobile robot may preferably include a plurality of decoupled active universal casters arranged in a rectangular shape, and the inverse kinematics model may be solved using the following calculation method:

[0036] Using the kinematic equations

[0037]

[0038]

[0039] Obtain the solution formula for the target deflection angle

[0040]

[0041] Wherein, R represents the radius of the decoupled active universal caster, B represents the offset distance of the decoupled active universal caster, represents the target deflection angle, Vx represents the moving speed of the omnidirectional mobile robot in the x-axis direction, V y represents the moving speed of the mobile robot in the y-axis direction, H represents half of the installation point spacing of the diagonally arranged decoupled active universal casters, ω is the rotational angular velocity of the omnidirectional mobile robot, and β represents the aspect ratio of the rectangle.

[0042] In some embodiments, the offset distance B of the decoupled active universal caster has a non-negative value range. Figure 2 As shown, when the offset distance B is a positive value, such as 5 cm or 10 cm, the decoupled active universal caster is a multi-degree-of-freedom caster with an offset, and when the offset distance B is 0, the decoupled active universal caster is a two-degree-of-freedom caster without an offset.

[0043] In some embodiments, as Figure 1 As shown, the deflection angle of the decoupled active universal caster is controlled by the steering drive motor 13. In step 2), the position angle of the steering drive motor 13 can be measured in real time, and the actual deflection angle is calculated based on the position angle. The beneficial effect of this technical solution is that by measuring parameters such as the operating angle or number of revolutions of the motor, the actual deflection angle of the decoupled active universal caster is indirectly reflected, without the need to use other deflection angle measurement components for measurement, the structure is streamlined, and the measured data is accurate. Of course, if, due to other needs, those skilled in the art set up additional deflection angle measurement components for measurement, it is also a technical solution based on the same inventive concept and also falls within the scope of protection of the present invention.

[0044] In some embodiments, in step 3), the deviation angle may be equal to the target deflection angle minus the actual deflection angle.

[0045] Please continue to see Figure 3 In some embodiments, step 4) further comprises the following steps:

[0046] The given deflection speed of the decoupled active universal caster is calculated, specifically by solving the given deflection speed of the decoupled active universal caster through a kinematic equation.

[0047] When the given yaw speed is above a yaw speed limit, the preset yaw speed is equal to the given yaw speed.

[0048] When the given yaw speed is less than the yaw speed limit, the preset yaw speed is equal to the yaw speed limit.

[0049] Based on the above technical solution, when the deviation angle is greater than π / 2, and the deflection speed of the decoupled active universal caster is less than a certain set value (i.e., the deflection speed limit) at this time, the decoupled active universal caster will obtain a smaller turning speed in advance, so that the deflection motor of the decoupled active universal caster of the omnidirectional mobile robot can obtain a fixed speed consistent with the direction of the final speed in advance, thereby guiding the deflection wheel of the decoupled active universal caster to reach the final target position at the deflection speed limit in advance, thereby avoiding the situation where it suddenly turns when running at a higher speed, improving the stability of the omnidirectional mobile robot, and reducing the vibration of the omnidirectional mobile robot during movement.

[0050] In some embodiments, the yaw speed limit can be adjusted based on the motion state of the omnidirectional mobile robot.

[0051] In some embodiments, the motion state includes the omnidirectional mobile robot switching from a forward / left state to a backward / right state, the omnidirectional mobile robot switching from a forward / backward state to a left / right state, etc.

[0052] In some implementations, when an omnidirectional mobile robot is in forward motion and suddenly receives a reverse motion command, the deflection angle π of the decoupled active swivel casters is at a singularity point. Directly controlling the deflection with a smaller deflection velocity results in varying response times for the deflection of the decoupled active swivel casters, leading to poor stability of the omnidirectional mobile robot. The proposed control algorithm predicts the decoupled active swivel casters' singularity points and assigns them a pre-deflection velocity to avoid them, enabling multiple decoupled active swivel casters to synchronously deflect to the target angle.

[0053] Based on the above technical solutions, the kinematic solution and control method provided by the present invention is applicable to all omnidirectional mobile robots with two degrees of freedom: rolling and rotation. The deflection angle π of the decoupled active universal casters is exactly the singularity point. If the existing control method, i.e., speed control after inverse kinematic solution, is used, when the calculated given deflection speed is low, the deflection response time of the decoupled active universal casters varies, resulting in discontinuous switching from the forward state to the reverse state of the omnidirectional mobile robot and poor stability. The proposed control method can determine in advance whether the casters have reached the singularity point and whether the given deflection speed is low, enabling multiple decoupled active universal casters to respond synchronously and deflect to the specified target position, thereby improving the motion smoothness and accuracy of the omnidirectional mobile robot.

[0054] An embodiment of the present invention also provides a kinematic solution and control device for an omnidirectional mobile robot, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is run by the processor, the steps of the kinematic solution and control method in any of the above-mentioned embodiments are executed.

[0055] Continue to see Figure 1-Figure 2 An embodiment of the present invention further provides an omnidirectional mobile robot, comprising a robot chassis 20, a decoupled active universal caster, and the above-mentioned kinematic solution and control device; the decoupled active universal caster is arranged on the robot chassis 20, and can be controlled by the kinematic solution and control device to deflect and roll relative to the robot chassis 20.

[0056] Among them, the robot chassis 20 can be a planar chassis or a non-planar chassis, such as a chassis with a concave-convex structure or a curved surface structure. Of course, the omnidirectional mobile robot can only include the above-mentioned structure, such as a robot for carrying goods, and other components can continue to be arranged on the chassis, such as manipulators, detectors and other components to achieve specific functions.

[0057] In some embodiments, the decoupled active universal caster includes a wheel frame 10, an axle frame 11, a roller 12, a steering drive motor 13, a rolling drive motor 14 and a differential 15; the first end of the axle frame 11 is rotatably connected to the wheel frame 10, and the roller 12 is rotatably connected to the second end of the axle frame 11 through its rotating axis; the steering drive motor 13, the rolling drive motor 14 and the differential 15 are fixed on the wheel frame 10, and the power output shafts of the steering drive motor 13 and the rolling drive motor 14 are both transmission-connected to the roller 12 through the differential 15.

[0058] In some embodiments, a plurality of the decoupled active universal casters may be symmetrically mounted on the robot chassis 20 .

[0059] In some embodiments, the plurality of decoupled active universal casters may preferably be installed in a rectangular shape on the robot chassis 20 .

[0060] As some typical application examples, see Figure 1 As shown, the active universal caster assembly of a decoupled omnidirectional mobile robot provided by the present invention mainly includes a roller 12, an axle frame 11, a wheel frame 10, a rolling drive motor 14, a steering drive motor 13 and a differential 15. The rolling drive motor 14 and the steering drive motor 13 are two servo motors, respectively. The two motors control the two degrees of freedom of movement of the decoupled active universal caster to achieve omnidirectional movement of the entire omnidirectional mobile robot. The differential 15 has the function of decoupling the rolling and steering of the roller 12, preventing the rolling drive motor 14 from generating additional rolling output to the roller 12 when the steering drive motor 13 drives the roller 12 to turn, which is beneficial to the rolling stability of the roller 12.

[0061] The kinematic calculation and control device primarily comprises an encoder connected to the rolling drive motor 14 and the steering drive motor 13, a driver, a motion control card, and an industrial computer. The encoder reads the actual position values ​​of the rolling drive motor 14 and the steering drive motor 13; the driver receives information and instructions from the motion control card to control the movement of the rolling drive motor 14 and the steering drive motor 13; the motion control card receives the control algorithm in the industrial computer and transmits it to the driver; the industrial computer calculates the motion control algorithm, issues control instructions, and receives information from the encoder via the driver and motion control card. The industrial computer can store a computer program for the kinematic calculation and control method for an omnidirectional mobile robot, and utilizes a processor in the industrial computer to execute the steps of the method.

[0062] As another typical application example, the kinematic solution and control method of the omnidirectional mobile robot in the above technical solution can preferably be implemented using the following steps:

[0063] The kinematic equation of the omnidirectional mobile robot is established, and the target deflection angle of each decoupled active universal caster of the theoretical mobile robot is calculated according to the current kinematic speed command.

[0064] Get the actual deflection angle of the current caster deflection motor in real time.

[0065] Calculate the deviation between the two angles to determine the size of the deviation.

[0066] If the deviation between the two is greater than π / 2 and the current speed of the deflection wheel is smaller, the speed is sent to the deflection motor at the set smaller limit speed.

[0067] If the deviation between the two is greater than π / 2 and the current yaw wheel speed is large, the yaw angular velocity value calculated by the current kinematics is directly sent to the yaw motor.

[0068] The kinematic solution and control method provided in the previous embodiment of the present invention is applicable to all decoupled omnidirectional mobile robots with or without offset casters. Upon receiving any motion control command, the omnidirectional mobile platform can achieve accurate and smooth motion. Specifically, when the active universal caster reaches the target position and rotates by an angle greater than π / 2, to avoid different steering directions and response times for the four casters, the casters are pre-aligned, for example, by a counterclockwise angle. This effectively avoids caster singularities. This control method effectively improves the motion control accuracy of the omnidirectional mobile robot and avoids vibration caused by sudden changes in caster direction during high-speed motion.

[0069] The above is a description of some of the more preferred embodiments of the present invention. It should be understood that the above embodiments are merely illustrative of the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A kinematic solution and control method for an omnidirectional mobile robot having a plurality of decoupled active universal casters, characterized in that: The kinematic solution and control method includes: 1) Calculating and obtaining a target deflection angle of the decoupled active universal caster; 2) obtaining an actual deflection angle of the decoupled active universal caster; 3) calculating the deviation angle between the target deflection angle and the actual deflection angle; 4) Calculating the given deflection speed of the decoupled active universal caster by using a kinematic equation; when the absolute value of the deviation angle is greater than π / 2, a preset time length is set in advance to allow the decoupled active universal caster to deflect toward the target deflection angle at a preset deflection speed, and when the given deflection speed is above the deflection speed limit, the preset deflection speed is equal to the given deflection speed, and when the given deflection speed is less than the deflection speed limit, the preset deflection speed is equal to the deflection speed limit; wherein, the preset time length = (absolute value of the deviation angle - π / 2) / preset deflection speed.

2. The kinematic solution and control method according to claim 1, characterized in that: In step 1), the target deflection angle of the decoupled active universal caster is obtained by calculating the target deflection angle of the decoupled active universal caster according to the current position and the target position of the omnidirectional mobile robot using an inverse kinematics model.

3. The kinematic solution and control method according to claim 2, characterized in that: The omnidirectional mobile robot includes a plurality of decoupled active universal casters arranged in a rectangular shape. The inverse kinematics model is solved using the following calculation method: Using the kinematic equations Obtain the solution formula for the target deflection angle Wherein, R represents the radius of the decoupled active universal caster, B represents the offset distance of the decoupled active universal caster, represents the target deflection angle, V x represents the moving speed of the omnidirectional mobile robot in the x-axis direction, V y represents the moving speed of the mobile robot in the y-axis direction, H represents half of the distance between the installation points of the diagonally arranged decoupled active universal casters, ω is the rotational angular velocity of the omnidirectional mobile robot, and β represents the aspect ratio of the rectangle; The offset distance B of the decoupled active universal caster has a value range of non-negative values.

4. The kinematic solution and control method according to claim 1, characterized in that: The deflection angle of the decoupled active universal caster is controlled by a steering drive motor. In step 2), the position angle of the steering drive motor is measured in real time, and the actual deflection angle is calculated based on the position angle.

5. The kinematic solution and control method according to claim 1, characterized in that: In step 3), the deviation angle is equal to the target deflection angle minus the actual deflection angle.

6. The kinematic solution and control method according to claim 1, characterized in that: The yaw speed limit can be adjusted based on the motion state of the omnidirectional mobile robot.

7. The kinematic solution and control method according to claim 6, characterized in that: The motion state includes any one or a combination of the following: the omnidirectional mobile robot's forward or left state switching to a reverse or right state, the omnidirectional mobile robot's forward or reverse state switching to a left or right state; When the omnidirectional mobile robot is in a forward movement state and suddenly receives an instruction to move backward, the singularity point of the decoupled active universal caster is predicted in advance and a preset deflection speed is given to the decoupled active universal caster to avoid the singularity point, and multiple decoupled active universal casters respond synchronously and deflect to the target deflection angle.

8. A kinematics solution and control device for an omnidirectional mobile robot, comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the computer program is executed by the processor, the steps of the kinematic solution and control method according to any one of claims 1 to 7 are executed.

9. An omnidirectional mobile robot, characterized in that: It comprises a robot chassis, a decoupled active universal caster, and the kinematics solution and control device as claimed in claim 8; The decoupled active universal caster is arranged on the robot chassis and can be controlled by the kinematic solution and control device to deflect and roll relative to the robot chassis.

10. The omnidirectional mobile robot according to claim 9, characterized in that: The decoupled active universal caster includes a wheel frame, an axle frame, a roller, a steering drive motor, a rolling drive motor and a differential; The first end of the shaft frame is rotatably connected to the wheel frame, and the roller is rotatably connected to the second end of the shaft frame via its rotation axis; The steering drive motor, rolling drive motor and differential are fixed on the wheel frame, and the power output shafts of the steering drive motor and rolling drive motor are both transmission-connected to the roller through the differential.

11. The omnidirectional mobile robot according to claim 10, characterized in that: A plurality of the decoupled active universal casters are symmetrically installed on the robot chassis.

12. The omnidirectional mobile robot according to claim 11, characterized in that: The plurality of decoupled active universal casters are installed in a rectangular shape on the robot chassis.

Images