High resolution stepper motor controller for tunable laser

Tunable laser system requires high resolution and accuracy in position of the wave selective optical element, which can be attained through the use of stepper motor. This paper focuses on the stepper motor controller, with the feedback to improve the accuracy and the microstepping technique to improve the resolution. Sine cosine and trapezoidal current controlling techniques for the micro stepping are used in two different types of situations. The proposed controller uses the linear interpolation and sine cosine current controlling technique to double the rotation accuracy than the resolution of the encoder and detect the obstacle by using the encoder and the static characteristic of the stepper motor. Also, the variable step interval technique is proposed to overcome the speed variation in the trapezoidal current controlling technique. The simulation and the experimental results show that, proposed controller can produce the accuracy at 0.0045°, the resolution at 0.0009° and obstacle detection. Therefore, proposed controller has better performance to suite the tunable laser system.