A Novel Method for Simultaneous Control of Speed and Torque of the Motors of a Cable Suspended Robot for Tracking Procedure

Abstract

In this paper, a new method is proposed for controlling the motors of ICaSbot (IUST Cable Suspended Robot) which is a modified version of crane aiming to object handling in industrial environments. In order to provide more accurate tracking, torque and speed of the motors are controlled simultaneously using inverse kinematics and inverse dynamics of the robot. The equations of the motors are evaluated as a look up table by conducting some special experimental tests and calibrations while their data sheets and motor parameters were not available. Required feed forward signal of the motors are estimated by the aid of inverse dynamics of the robot while its error are compensated by the aid of PID controller on the speed and torque of the motor. As a result, required (Pulse Width Modulation) PWM of the motor are exerted to produce a desired angular velocity while a specific amount of torque is applied on the motors. Not only the voltage of the motors is controlled using the mentioned PWM, but also the current are improved using the feedback control of the torques. PID gains are optimized using Ziegler-Nicholsmethod. By the aid of the mentioned combination of feed forward and feedback controlling terms of motor speed and torque, the desired trajectory is tracked with the highest possible accuracy. The efficiency of the proposed method is eventually proved by comparing the experimental tests with simulation results.