CN114954501A - Omnidirectional mobile robot, its kinematics solution and control method and device - Google Patents

Abstract

The invention discloses an omnidirectional mobile robot, its kinematics solution and control method and device. The calculation and control method includes: 1) obtaining the target deflection angle of the decoupling active caster; 2) obtaining the actual deflection angle of the decoupling active caster; 3) calculating the The deviation angle between the target deflection angle and the actual deflection angle; 4) when the absolute value of the deviation angle is above π/2, make the decoupling active universal caster move to the desired direction at a preset deflection speed in advance for a preset period of time. Deflect according to the target deflection angle. The kinematics calculation and control method of the omnidirectional mobile robot provided by the present invention controls the decoupling active universal caster to deflect at the preset deflection speed in advance by judging the deviation angle to be deflected, thereby avoiding the sudden occurrence of the wheel of the mobile robot. Steering, or the inaccurate control direction, thus avoiding the reduction of the accuracy of the omnidirectional mobile robot or the occurrence of vibration.

Description

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

technical field

The invention belongs to the technical field of robots, and relates to a decoupled omnidirectional mobile robot, in particular to an omnidirectional mobile robot, a kinematics solution and control method and device thereof.

Background technique

Compared with the traditional mobile mobile robot, the decoupled omnidirectional mobile robot can realize the function of omnidirectional movement, has the characteristics of high flexibility, and can move in different narrow areas. It is widely used in other fields.

Different from traditional mobile robots, in order to achieve omnidirectional motion, this type of robot usually achieves omnidirectional movement by adjusting the deflection azimuth of each wheel on the chassis, and adjusting the deflection azimuth of the wheels on the chassis requires kinematics. solve to achieve.

For this type of robot, when kinematics is solved, strange phenomena will occur in some positions, that is, when mapping from the velocity space of the mobile robot to the joint space, there are multiple solutions in the joint space. If the kinematics solution is not selected properly, it will As a result, the wheels of the mobile robot suddenly turn, or the control direction is inaccurate, resulting in the reduction of the accuracy of the mobile robot or the occurrence of vibration. Therefore, how to avoid the above phenomenon has become an urgent technical problem to be solved in the art.

SUMMARY OF THE INVENTION

In view of the deficiencies of the prior art, the purpose of the present invention is to provide an omnidirectional mobile robot, its kinematics solution and control method and device.

In order to realize the foregoing invention purpose, the technical scheme adopted in the present invention includes:

In a first aspect, 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, and the kinematics solution and control method includes:

1) Calculate and obtain the target deflection angle of the decoupled active swivel caster;

2) Obtain the actual deflection angle of the decoupled active universal caster;

3) Calculate 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, deflect the decoupling active swivel caster to the target deflection angle at a preset deflection speed in advance for a preset period of time.

In a second aspect, the present invention also provides a kinematics solution and control device for an omnidirectional mobile robot, including a memory and a processor, wherein the memory stores a computer program, and the computer program is executed by the processor to execute the above-mentioned The steps of the kinematics solution and control method.

In a third aspect, the present invention also provides an omnidirectional mobile robot, including a robot chassis, a decoupled active universal caster, and the above kinematics solution and control device;

The decoupled active universal caster is disposed on the robot chassis, and can be controlled by the kinematics solution and control device to deflect and roll relative to the robot chassis.

Based on the above technical solutions, compared with the prior art, the beneficial effects of the present invention at least include:

The kinematics calculation and control method of the omnidirectional mobile robot provided by the present invention controls the decoupling active universal caster to deflect at the preset deflection speed in advance by judging the size of the deviation angle to be deflected, thereby avoiding the sudden occurrence of the wheel of the mobile robot. Steering, or the inaccurate control direction, thus avoiding the reduction of the accuracy of the omnidirectional mobile robot or the occurrence of vibration.

The above description is only an overview of the technical solutions of the present invention. In order to enable those skilled in the art to understand the technical means of the present application more clearly, and to implement them in accordance with the contents of the description, the following preferred embodiments of the present invention are used in conjunction with the detailed descriptions. The accompanying drawings are described below.

Description of drawings

1 is a schematic structural diagram of a decoupled active swivel caster provided by a typical implementation case of the present invention;

2 is a schematic structural diagram of an omnidirectional mobile robot provided by a typical implementation case of the present invention;

3 is a schematic flowchart of a kinematics solution and control method for an omnidirectional mobile robot provided by a typical implementation case of the present invention;

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

20. Robot chassis.

Detailed ways

In view of the deficiencies in the prior art, after long-term research and a lot of practice, the inventor of this case was able to propose the technical solution of the present invention, which can be summarized as: establishing an inverse kinematics model of a decoupled omnidirectional mobile robot, the model calculation is simple and clear , to lay a solid foundation for the subsequent control methods. After obtaining the working space speed, the angle at which the four casters reach the target position is predicted according to inverse kinematics; when the angle difference between the predicted position and the actual deflection position is greater than π/2, and the steering speed of the active swivel caster is within a set When it is within the limit range, send a small speed to the deflection motor of the active universal caster in advance to make it turn in advance, so as to avoid the sudden turning of the deflection motor when the speed is high, thereby reducing the sudden vibration of the mobile robot. possibility. The technical solution, its implementation process and principle will be further explained as follows.

Many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific implementation disclosed below. example limitations.

Moreover, relational terms such as "first" and "second" etc. are only used to distinguish one component or method step of the same name from another and do not necessarily require or imply that any one of these components or method steps is required or implied. any such actual relationship or sequence exists.

Referring first to FIG. 1 to FIG. 3 , an embodiment of the present invention provides a kinematics solution and control method for an omnidirectional mobile robot. The omnidirectional mobile robot includes a plurality of decoupled active universal casters. The kinematics The solution and control method includes the following steps:

1) Calculate and obtain the target deflection angle of the decoupled active swivel caster.

2) Obtain the actual deflection angle of the decoupled active swivel caster.

3) Calculate 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, the decoupling active universal caster is deflected to the target deflection angle at a preset deflection speed by a preset time period in advance, wherein the preset Duration=(absolute value of the deviation angle-π/2)/preset deflection speed.

The above kinematics calculation and control methods are mainly used for decoupling active swivel casters with offsets to improve their motion stability. Of course, as described below, they can also be used for unbiased decoupling active swivel casters. The omnidirectional mobile robot adopts at least two decoupled active universal casters. As some specific application examples, the kinematics algorithm may include: establishing an omnidirectional mobile robot according to the omnidirectional mobile robot with caster offset According to the inverse kinematics model, the angles at which the four casters reach the target position are calculated; when the deviation between the calculated theoretical target position and the actual current position of the casters is greater than π/2, the decoupling active universal casters are given in advance. The yaw motor sends a smaller yaw speed value according to the direction of the deviation. The prediction and control method can avoid the situation that the casters of this type of omnidirectional mobile robot do not deflect at low speed, but the deflection wheels suddenly turn when the vehicle body runs to a higher speed.

When the decoupled active swivel caster is deflected to a certain position, and if the angle formed by the given speed direction and the current deflection direction of the swivel wheel is π, then it is a singular point, and the present invention provides The solution and control method of , allows the decoupled active swivel caster of the omnidirectional mobile robot to avoid this singularity in advance.

The kinematics solution and control method provided by the present invention can always ensure that the decoupled active universal caster rotates to the opposite direction of the motion of the omnidirectional mobile robot after the omnidirectional mobile robot obtains commands of various motion states. The method can improve the stability of the mobile robot, and the algorithm is simple and easy to implement.

In some embodiments, in step 1), according to the current position and target position of the omnidirectional mobile robot, an inverse kinematics model can be used to obtain the target deflection angle of the decoupled active swivel caster.

In some embodiments, the omnidirectional mobile robot may preferably include a plurality of decoupled active swivel casters arranged in a rectangle, and the inverse kinematics model may be solved by using the following calculation method:

Using kinematic equations

Obtain the solution formula of the target deflection angle

代表所述目标偏转角度，Vx代表所述全向移动机器人在x轴方向上的移动速度，V_y代表所述移动机器人在y轴方向上的移动速度，H代表对角设置的所述解耦式主动万向脚轮的安装点间距的一半，ω是所述全向移动机器人的旋转角速度，β代表所述矩形的长宽比。Wherein, R represents the radius of the decoupled active swivel caster, B represents the offset distance of the decoupled active swivel caster,

represents the target deflection angle, Vx represents the moving speed of the omnidirectional mobile robot in the x-axis direction, _Vy represents the moving speed of the mobile robot in the y-axis direction, and H represents the decoupling of the diagonal setting The distance between the installation points of the type active swivel caster is half of the distance, ω is the rotational angular velocity of the omnidirectional mobile robot, and β represents the aspect ratio of the rectangle.

In some embodiments, the value range of the offset distance B of the decoupled active swivel caster is a non-negative value. It can be understood that, as shown in FIG. 2, when the value of the offset distance B is a positive value, such as 5cm or 10cm, the decoupled active swivel caster is an offset multi-degree-of-freedom caster. When the value of the offset distance B is 0, the decoupled active swivel caster is an unbiased two-degree-of-freedom caster.

In some embodiments, as shown in FIG. 1 , the deflection angle of the decoupled active swivel 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 the actual deflection angle of the decoupled active swivel caster can be indirectly reflected by measuring parameters such as the running angle or the number of turns of the motor, and there is no need to use other deflection angle measuring components for measurement, simplifying Structure and the measured data are accurate. Of course, if a person skilled in the art sets up an additional deflection angle measurement component for measurement due to other requirements, it is also a technical solution based on the same inventive concept and also falls within the protection scope of the present invention.

In some embodiments, in step 3), the deviation angle may be equal to the subtraction of the target deflection angle and the actual deflection angle.

Please continue to refer to Figure 3, in some embodiments, step 4) also includes the following steps:

Calculating the given deflection speed of the decoupled active swivel caster, specifically, calculating the given deflection speed of the decoupled active swivel caster through kinematic equations.

The preset yaw speed is equal to the given yaw speed when the given yaw speed is above the yaw speed limit.

When the given yaw speed is less than the yaw speed limit value, the preset yaw speed is equal to the yaw speed limit value.

Based on the above technical solution, when the deviation angle is greater than π/2, and the deflection speed of the decoupled active caster is less than a certain set value (that is, the deflection speed limit), the decoupled active caster The caster will obtain a small turning speed in advance, so that the deflection motor of the decoupled active swivel caster of the omnidirectional mobile robot obtains a fixed speed consistent with the final speed direction in advance, thereby guiding the deflection of the decoupled active swivel caster in advance. The wheel reaches the final target position with the deflection speed limit in advance, thereby avoiding the situation of sudden turning when it runs to a higher speed, improving the stability of the omnidirectional mobile robot, and reducing the vibration during the motion of the omnidirectional mobile robot.

In some embodiments, the yaw speed limit is adjustable based on the state of motion of the omnidirectional mobile robot.

In some implementations, the motion state includes switching the forward/left-running state of the omnidirectional mobile robot to the backward/right-running state, and switching the forward/reverse state of the omnidirectional mobile robot to left-running/right-running, etc.

In some embodiments, when the omnidirectional mobile robot is in the forward motion state and suddenly receives the instruction of the backward motion state, the deflection angle π of the decoupled active universal caster is just the singular point. The smaller deflection speed control results in different response times of the deflection of the decoupled active swivel casters, resulting in poor stability of the omnidirectional mobile robot. Using the proposed control algorithm, the singular point of the decoupled active swivel caster is predicted in advance, and the pre-deflection speed is given to the caster to avoid the singular point, so as to realize the synchronous response of multiple decoupled active swivel casters to the target angle.

Based on the above technical solutions, the kinematics solution and control method provided by the present invention is suitable for all omnidirectional mobile robots with two degrees of freedom of rolling and rotation, and the deflection angle π of the decoupled active universal caster is just singular Point, if the existing control method is used, that is, the speed control after inverse kinematics solution, when the calculated given deflection speed is low, the deflection response time of the decoupled active caster will be different, resulting in omnidirectional The switching of the forward state of the mobile robot to the backward state is discontinuous and the stability is poor. Using the proposed control method, it can be judged in advance whether the casters move to the singular point and whether the given deflection speed is small, so that multiple decoupled active universal casters can be synchronously responded to deflect to the designated target position, and the motion stability of the omnidirectional mobile robot is improved. Sex and movement precision.

An embodiment of the present invention further provides a kinematics solution and control device for an omnidirectional mobile robot, including a memory and a processor, wherein the memory stores a computer program, and the computer program executes any one of the above when the processor is run. Steps of a kinematic solution and control method in an embodiment.

Continuing to refer to FIG. 1 to FIG. 2, an embodiment of the present invention further provides an omnidirectional mobile robot, including a robot chassis 20, a decoupled active universal caster, and the above kinematics calculation and control device; the decoupled active universal caster; The casters are arranged on the robot chassis 20 and can be controlled by the kinematics solution and control device to deflect and roll relative to the robot chassis 20 .

Wherein, the robot chassis 20 may 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 may only include the above-mentioned structures, such as a robot for carrying goods , you can also continue to set other components on the chassis, such as manipulators, detectors and other components to achieve specific functions.

In some embodiments, the decoupled active swivel caster includes a wheel frame 10 , a pedestal 11 , a roller 12 , a steering drive motor 13 , a rolling drive motor 14 and a differential 15 ; The end is rotatably connected to the wheel frame 10, the roller 12 is rotatably connected to the second end of the axle frame 11 through its rotating shaft; the steering drive motor 13, the rolling drive motor 14 and the differential 15 are fixed On the wheel frame 10 , the power output shafts of the steering driving motor 13 and the rolling driving motor 14 are all connected to the roller 12 through the differential gear 15 .

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

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

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

The kinematics solution and control device mainly includes 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 in structure. The encoder is used to read the actual position value of the rolling drive motor 14 and the steering drive motor 13; the driver receives the motion control card information instruction to control the motion 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 then It is transmitted to the driver; the industrial computer is used to calculate the motion control algorithm to issue control instructions, and to receive the encoder information through the driver and the motion control card, wherein the industrial computer can be made to store the above kinematics solution and control method for the omnidirectional mobile robot The computer program of the invention uses the processor in the industrial computer to execute the steps of the above method.

As another typical application example, the kinematics solution and control method of the omnidirectional mobile robot in the above technical solution can preferably be implemented by the following steps:

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

Obtain the actual deflection angle of the current caster deflection motor in real time.

Calculate the deviation between the two angles to determine the magnitude of the deviation.

If the deviation between the two is greater than π/2, and the current speed of the deflection wheel is small, it will be sent to the deflection motor at the set smaller limit speed.

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

The aforementioned kinematics calculation and control method provided in the previous embodiment of the present invention is applicable to all decoupled omnidirectional mobile robots with offset casters or without offset. After receiving any motion control command, the omnidirectional mobile platform can Accurate and smooth movement is achieved. For example, when the angle of rotation of the active swivel casters to the target position is greater than π/2, in order to avoid different steering directions and response times of the four casters, the casters are turned in the same direction in advance, for example, they are all deflected by an angle in the counterclockwise direction. This can smoothly avoid the singular point of the caster; the control method effectively improves the motion control precision of the omnidirectional mobile robot, and avoids the vibration caused by the sudden change of the direction of the caster when the mobile robot moves at a high speed.

The above is a statement of some preferred embodiments of the present invention. It should be understood that the above-mentioned embodiments are only to illustrate the technical concept and characteristics of the present invention, and the purpose is to enable those who are familiar with the art to understand the content of the present invention and to use it accordingly. Implementation does not limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be included within the protection scope of the present invention.

Claims (10)

1. a kind of kinematics solution and control method of omnidirectional mobile robot, described omnidirectional mobile robot has a plurality of decoupling active universal casters, it is characterized in that, described kinematics solution and control method comprise: 1) Calculate and obtain the target deflection angle of the decoupled active swivel caster; 2) Obtain the actual deflection angle of the decoupled active universal caster; 3) Calculate 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, the decoupling active universal caster is deflected to the target deflection angle at a preset deflection speed by a preset time period in advance, wherein the preset Duration=(absolute value of the deviation angle-π/2)/preset deflection speed. 2. kinematics solution and control method according to claim 1, is characterized in that, in step 1), according to the current position and target position of described omnidirectional mobile robot, utilize inverse kinematics model to solve to obtain described solution The target deflection angle of the coupled active swivel caster. 3. The kinematics solution and control method according to claim 2, wherein the omnidirectional mobile robot comprises a plurality of decoupled active universal casters arranged in a rectangle, and the inverse kinematics model adopts the following The calculation method to solve: Using kinematic equations

Obtain the solution formula of the target deflection angle

Wherein, R represents the radius of the decoupled active swivel caster, B represents the offset distance of the decoupled active swivel 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, and H represents the solution set diagonally Half of the distance between the installation points of the coupled active casters, ω is the rotational angular velocity of the omnidirectional mobile robot, and β represents the aspect ratio of the rectangle; Preferably, the value range of the offset distance B of the decoupled active swivel caster is a non-negative value. 4. kinematics solution and control method according to claim 1, is characterized in that, the deflection angle of described decoupling active universal caster is controlled by steering drive motor, in step 2), measure described steering drive in real time The position angle of the motor, and the actual deflection angle is calculated based on the position angle. 5 . The kinematics solution and control method according to claim 1 , wherein, in step 3), the deviation angle is equal to the subtraction of the target deflection angle and the actual deflection angle. 6 . 6. kinematics solution and control method according to claim 1, is characterized in that, step 4) also comprises: Calculate the given deflection speed of the decoupled active swivel caster through kinematic equations; When the given deflection speed is above the deflection speed limit value, the preset deflection speed is equal to the given deflection speed; When the given yaw speed is less than the yaw speed limit value, the preset yaw speed is equal to the yaw speed limit value. 7. The kinematics solution and control method according to claim 6, wherein the deflection speed limit value can be adjusted based on the motion state of the omnidirectional mobile robot; Preferably, the motion state includes switching the omnidirectional mobile robot's forward or left travel state to reverse or right travel state, and the omnidirectional mobile robot's forward or backward state switching to left or right travel state. or a combination of both; Preferably, when the omnidirectional mobile robot is in a forward motion state and suddenly receives an instruction in a backward motion state, the singular point of the decoupled active caster is predicted in advance and given to the decoupled active caster. The deflection speed is preset to the casters to avoid the singular point, and the plurality of decoupled active swivel casters are synchronously responded to deflect to the target deflection angle. 8. A kinematics solution and control device of an omnidirectional mobile robot, comprising a memory and a processor, wherein the memory stores a computer program, wherein the computer program is executed by the processor when executing claim 1 Steps of the kinematics solution and control method described in any one of -7. 9. An omnidirectional mobile robot, characterized in that it comprises a robot chassis, a decoupling active universal caster and the kinematics solution and control device of claim 8; The decoupled active universal caster is disposed on the robot chassis, and can be controlled by the kinematics solution and control device to deflect and roll relative to the robot chassis. 10. The omnidirectional mobile robot according to claim 9, wherein the decoupled active universal caster comprises a wheel frame, an axle frame, a roller, a steering drive motor, a rolling drive motor and a differential; The first end of the axle frame is rotatably connected to the wheel frame, and the roller is rotatably connected to the second end of the axle frame through its rotating shaft; The steering driving motor, the rolling driving motor and the differential are fixed on the wheel frame, and the power output shafts of the steering driving motor and the rolling driving motor are all connected to the roller through the differential; Preferably, a plurality of the decoupled active universal casters are symmetrically installed on the robot chassis; Preferably, a plurality of the decoupled active swivel casters are installed in a rectangular shape on the robot chassis.

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