A normalized smoothing control scheme based on fuzzy modeling for the control of DC brushless servo drives

A robust controller design scheme applied to brushless servo drives is proposed. In order to provide smooth torque at various operating conditions, a fully digitized subharmonics PWM implemented on a digital signal processor (DSP TMS320C25) EV board is utilized to make the phase current being sinusoids. For the controller design in current loop, a proportional-integral controller is adopted to eliminate the effects between the currents and the mechanical dynamics; a method of nearly decoupling of d-q axis is used. In position and velocity loops, a normalized smoothing control scheme based on fuzzy modeling is proposed to force the system response constrained on a desired hyperplane without hard chatters. Furthermore, to suppress the steady-state error, a parallel-integral structure based on a pre-set bound on a normalized phase plane is applied. For validation of the proposed scheme, experimental studies under signification load variation and external disturbances are performed in a DC brushless servo drive