CN110879621A - Speed closed-loop control method applied to balance torque of four-wheel drive wheeled robot - Google Patents

Abstract

The invention discloses a speed closed-loop control method for balancing torque applied to a four-wheel-drive four-wheel robot, which comprises the following steps of calculating a given steering angle α of any wheel according to a given translational linear velocity vector V and a given rotation angular velocity omega_iAnd a rotation speed V_iA one-to-one correspondence of the steering angle α_iAs angular inputs to four wheel steering servo systems; acquiring and acquiring the current actual rotating speed V of any wheel from a servo driver_ri(ii) a Determining the rotational speed V_iWith the current actual speed V_riDifference value delta of_i(ii) a Difference δ for any wheel_iPID adjustment is performed, and the output of the PID adjustment is used as the torque T of any one walking servo motor_i(ii) a Obtaining the average torque of the walking servo motor; and setting a walking servo system to be in a torque closed-loop mode, and outputting the average torque to the walking servo system. Through the scheme, the four-wheel-drive four-wheel robot has the advantages of simplicity and convenience in control, simple logic and the like, and has the advantages in the technical field of four-wheel-drive four-wheel robotsHas high practical value and popularization value.

Description

Speed closed-loop control method applied to balance torque of four-wheel drive wheeled robot

Technical Field

The invention relates to the technical field of four-wheel-drive four-wheel robots, in particular to a speed closed-loop control method for balancing torque, which is applied to the four-wheel-drive four-wheel robot.

Background

A four-wheel drive robot is a flexible novel robot trolley which is provided with four wheels, but unlike the common four-wheel trolley, each wheel of the four-wheel drive robot has two independent degrees of freedom, namely each wheel is provided with two independent servo drive systems, one is responsible for driving the wheels to rotate, and the other is responsible for driving the wheels to steer, and can be respectively called as a walking servo system and a steering servo system.

Because each wheel can independently turn to, consequently, four change four wheel drive robot has very high removal flexibility, can easily accomplish the motion that ordinary four-wheel dolly can not accomplish such as pivot turns to, horizontal, oblique translation. In order to accurately control the position and the speed of the robot, the overall speed closed-loop control of the robot needs to be realized, and an ideal control algorithm is as follows:

as shown in fig. 1, when the robot is viewed as a whole, its motion on a two-dimensional plane includes two given quantities, i.e., a translational linear velocity vector V and a rotational angular velocity ω, by which the steering angles and the rotational speeds of the four wheels can be calculated in combination with the mechanical dimensions of the platform itself. Then respectively outputting the steering angle to the steering servo system of each wheel and outputting the rotating speed to the walking servo system of each wheel, thus realizing the given movement. At this time, the steering servo system works in a position closed loop mode, and the walking servo system works in a speed closed loop mode.

The specific calculation method is as follows:

point O is the geometric center of the robot, O₁、O₂、O₃、O₄Respectively, the projection of the axes of the four wheels on the plane. And establishing a rectangular coordinate system by taking the point O as an origin, taking the right front of the vehicle body as the positive direction of the y axis and the right side of the vehicle body as the positive direction of the x axis.

Setting the current given vehicle linear velocity vectorV and the angular velocity of rotation is ω, then the linear velocity vectors V of the four wheels can be calculated respectively according to the velocity vector composition_iFor example, the top right wheel No. 2 has an axis projection of O₂The translational linear velocity vector is V, and the rotation angular velocity omega is O₂The linear velocity vector of the point generation is set as V omega₂Then V ω₂Is perpendicular to line segment OO₂Let a line segment OO₂Is L, then

Where a is the track width of the robot and b is the wheelbase of the robot.

Vω₂Modulo V ω₂I | ═ ω · L means that the angular velocity of rotation ω is at O₂The linear velocity of the dot generation.

Calculating translation velocity vector V and linear velocity vector V omega generated by rotation₂The vector sum of (1) is the linear velocity vector V of the No. 2 wheel₂。V₂The included angle of the Y axis is set to α₂，V₂Is a modulus of | V₂If α₂The steering angle input of the No. 2 wheel steering servo system and the speed input of the No. 2 wheel traveling servo system are | V₂L, positive or negative of which is vector V₂Is determined. Similarly, the steering angle and the walking speed of the wheels 1, 3 and 4 can be respectively calculated.

However, the above algorithm is based on an ideal situation, it is considered that four wheels of the robot are absolutely symmetrical, and the installation positions and the mechanical states are completely consistent, when in actual application, because the machining precision is limited, the installation position of each wheel has deviation, the rotation angle of the wheel has error with the set value, the circumferential diameters of the wheels are not completely the same, the four wheels of the robot are independently driven, and there is no differential, so the deviation can not be compensated by the differential as for the electric automobile, during the actual moving process, the actual rotation speed that the four wheels need to reach has certain deviation with the theoretical calculated value, so almost all the wheels can not rotate to the set speed, even if the deviation is not large, forcing the wheels to rotate to the theoretical calculated value by using the speed closed loop can cause serious consequences, and the torques and powers of the four motors are seriously unbalanced, some motors do not exert force but block the motion of the platform, other motors work in an overload mode, the problems of overload shutdown and the like of the motors occur, even a driver or the motors can be burnt in severe conditions, and therefore the ideal control method cannot be suitable for the four-wheel drive wheeled robot.

Disclosure of Invention

The invention aims to provide a speed closed-loop control method for balancing torque applied to a four-wheel drive wheeled robot, which adopts the following technical scheme:

a speed closed-loop control method for balancing torque applied to a four-wheel-drive four-wheel robot is characterized in that any wheel of the four-wheel-drive four-wheel robot is driven by an independent walking servo system and a steering servo system, a servo driver and a walking servo motor are arranged in the walking servo system, and the servo driver is electrically connected with the walking servo motor and drives the walking servo motor to rotate; the speed closed-loop control method comprises the following steps:

calculating a given steering angle α of any wheel according to a given translational linear velocity vector V and a given rotational angular velocity omega_iAnd a rotation speed V_i(ii) a The value of i is 1, 2, 3, 4;

one-to-one correspondence will turn angle α_iAs angular inputs to four wheel steering servo systems;

acquiring and acquiring the current actual rotating speed V of any wheel from a servo driver_ri；

Determining the rotational speed V_iWith the current actual speed V_riDifference value delta of_i；

Difference δ for any wheel_iPID adjustment is performed, and the output of the PID adjustment is used as the torque T of any one walking servo motor_i；

Obtaining the average torque of the walking servo motor;

and setting a walking servo system as a torque closed-loop mode, and outputting the average torque to the walking servo system to realize closed-loop control.

Compared with the prior art, the invention has the following beneficial effects:

the four-wheel drive robot is used as a whole to carry out speed closed-loop control, so that the whole speed of the robot is consistent with the set speed, the rotating speed of each wheel is not attempted to be consistent with an ideal calculated value, and the four wheels have the same acting force because the torques output to the four-wheel walking servo system are consistent, so that the motor overload phenomenon can be prevented, and meanwhile, the robot can still be accurately controlled in speed and position by combining with a positioning navigation algorithm on the upper layer; in conclusion, the four-wheel-drive four-wheel robot has the advantages of simplicity and convenience in control, simple logic and the like, and has high practical value and popularization value in the technical field of four-wheel-drive four-wheel robots.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention, and therefore should not be considered as limiting the scope of protection, and it is obvious for those skilled in the art that other related drawings can be obtained according to these drawings without inventive efforts.

FIG. 1 is a schematic diagram of the theoretical calculation of the present invention.

FIG. 2 is a flow chart of the closed loop control of the present invention.

Detailed Description

To further clarify the objects, technical solutions and advantages of the present application, the present invention will be further described with reference to the accompanying drawings and examples, and embodiments of the present invention include, but are not limited to, the following examples. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Examples

As shown in fig. 2, the present embodiment provides a speed closed-loop control method for balancing torque applied to a four-wheel drive wheeled robot, which specifically includes the following steps:

first of all, the first step is to,ideally, the given steering angle α for the four wheels is calculated from the given translational linear velocity vector V and the given rotational angular velocity ω_iAnd a rotation speed V_i(ii) a At the moment, the steering servo system still works in a position closed loop mode, but the walking servo system is switched into a torque mode, and the speed closed loop of the walking servo system is moved to an upper algorithm from a walking servo driver to realize;

then, the given steering angle α is set_iAs angular inputs to four wheel steering servo systems;

then, the current actual rotating speeds V of the four wheels are respectively obtained from the servo drivers_ri(ii) a I.e. V_r1、V_r2、V_r3And V_r4；

Then, the predetermined rotational speeds V are respectively obtained_iWith the actual speed V_riDifference value delta of_i；

For each delta_iPID adjustment is respectively carried out, and the output of the PID adjustment is used as the torque T of each walking servo motor_i(ii) a Namely T₁、T₂、T₃And T₄；

Finally, the average torque T of the four-wheel walking servo system is obtained_m：

And average torque T_mAnd simultaneously output to four walking servo systems as given torque.

The above-mentioned embodiments are only preferred embodiments of the present invention, and do not limit the scope of the present invention, but all the modifications made by the principles of the present invention and the non-inventive efforts based on the above-mentioned embodiments shall fall within the scope of the present invention.

Claims (1)

1. A speed closed-loop control method for balancing torque applied to a four-wheel-drive four-wheel robot is characterized in that the speed closed-loop control method comprises the following steps:

calculating a given steering angle α of any wheel according to a given translational linear velocity vector V and a given rotational angular velocity omega_iAnd a rotation speed V_i(ii) a The value of i is 1, 2, 3, 4;

one-to-one correspondence will turn angle α_iAs angular inputs to four wheel steering servo systems;

acquiring and acquiring the current actual rotating speed V of any wheel from a servo driver_ri；

Determining the rotational speed V_iWith the current actual speed V_riDifference value delta of_i；

Difference δ for any wheel_iPID adjustment is performed, and the output of the PID adjustment is used as the torque T of any one walking servo motor_i；

Obtaining the average torque of the walking servo motor;

and setting a walking servo system as a torque closed-loop mode, and outputting the average torque to the walking servo system to realize closed-loop control.

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