Design and Implementation of a Feedback Control System for a Stepper Motor

Abstract

Stepper motors are motors that indexes by digital pulses that turn their rotors a fixed fraction of a revolution where they will be clamped securely by their inherent holding torque. Stepper motors are a cost-effective and a reliable choice for many applications such as CNC and Robotics. They are used as open loop control systems which are in no need for feedback devices. Being open loop control systems, their major drawback is that if they were not used within their specified range of load and speed, then their positioning accuracy will be jeopardized. However, a feedback loop can improve the positioning accuracy of a stepper motor without incurring the higher costs of a complete servo system. In this research work a stepper motor position control system was designed and implemented using a computer and an Arduino micro-controller as a monitoring controller, which will detect the position of the motor shaft via an optical encoder. The computer was used to input the data and to display a message if the stepper motor`s operation was interrupted. This control system was tested to detect if the motor was stopped or delayed for a casual reason and then derive the motor to the correct required position. Also the system was tested for accuracy. A steady error of 10% was detected and was attributed to the poor resolution of the encoder used.