PWM nonlinearity reduction in microstepping unit firmware

Abstract

Pulse Width Modulation (PWM) is a popular method for controlling analogue circuits with digital output of a microcontroller. This paper is focused on practical issues of using PWM in precise positioning systems. PWM is easy to grasp intuitively, but due to the motor characteristics, is not as easy to implement as one would expect. There is a distortion or nonlinear gain between the reference and real output voltage in the PWM system. In this paper, we will present a pure software solution to perform the PWM correction. We will introduce a novel algorithm capable of running on a small microcontroller. The algorithm is capable of performing all necessary computations for the PWM compensation without a need of feedback.