Precision concurrent speed and position tracking of brushed dc motors using nonlinear time-frequency control

Abstract

Brushed DC motors are essential components in a wide range of applications in which their unique benefits are explored. However, their being inherently nonlinear and sensitive to system based uncertainties such as load variation and process noise has made improving the precision control of brushed DC motors a challenging task. To mitigate such negative effects that invariably undermine motor stability and controllability, a novel wavelet-based nonlinear time-frequency control scheme viable for the concurrent speed and position tracking of brushed DC motors is presented. The control approach has its basis in discrete wavelet transformation and adaptive control. Considering system response in the wavelet domain allows the true dynamics of the system as delineated by both the time and frequency information of the response to be faithfully resolved without being distorted or misinterpreted. By employing adaptive theory, the undesirable features typical of nonlinear brushed DC motor systems such as being highly unstable and energy inefficient are also properly addressed. The validity of the controller design are demonstrated by evaluating its performance and the power requirement against PID control and fuzzy logic control in mitigating the speed, position, and armature voltage responses of a permanent magnet brushed DC motor under severe system uncertainties. The proposed nonlinear controller is shown to be accurate, robust, energy efficient, low in power requirement, and easy to switch between speed and position control.