Hybrid fractional-integer position controller for a DC brushless motor

In this work, a Fractional hybrid controller scheme for position control of a DC brushles motor is presented. The control strategy consists of a standard linear state variables feedback controller followed by a fractional derivative (FD) with unitary static gain, which contributes with a Hat phase lead compensation and higher gain at high frequencies without altering the steady state characteristics. This improves the robustness of the control position for the brushless DC-motor against of changes in its electromechanical parameters. Moreover, an improvement is achieved against the effect of a strong non-linearity due to electric current constraints, thus the available torque. The FD order is and can be easily implemented as a digital filter with a relative short number of coefficients and a reasonable sampling time.