High resolution stepper motor controller for tunable laser

A Dissertation submitted to the Dept. of Electronics & Telecommunication Eng. for thedegree of Master of Science .CD-ROM IncludedTunable laser systems use stepper motors to rotate the wave selective optical elements. Stepper motors can rotate with high accuracy and precision. This research focuses on the stepper motor controller, with the feedback to improve the accuracy and the precision of the movement. Sine cosine and trapezoidal current controlling techniques for micro stepping are analyzed, and used in two different types of situations. The variable step interval technique is proposed to overcome the speed variation in the trapezoidal current controlling technique. The proposed controller uses the linear interpolation and sine cosine current controlling technique to improve the rotation accuracy by two times than the resolution of the encoder. The technique is proposed to detect the obstacle by using the encoder and the static characteristic of the stepper motor. The simulation and the experimental results show that proposed controller can produce the required accuracy, the precision and obstacle detection. Also, the movement smoothness could be achieved by variable step intervals. Therefore, proposed controller has better performance to suit the tunable laser system