BLDC motor output feedback velocity tracking control with trapezoidal approximation and no angular velocity

In this work, a velocity tracking control strategy is presented using passivity methodology for a permanent magnet synchronous machine with uniformly distributed windings, which is known as a brushless direct current (BLDC) motor. The trapezoidal components of back electromotive force (EMF) are here modeled by using a novel differentiable approximation. The proposed control scheme is constructed by employing only measurements of the shaft position and stator currents. The use of a second-order filter makes it possible to solve the velocity tracking control problem without measuring the actual rotor velocity. A formal stability analysis of the closed-loop system consisting of the motor, the controller, and the second-order filter is presented using partial stability theory. By applying partial stability, the relevant variables are shown to converge, while the behavior of the rest of the variables that are not relevant to the control objective can be disregarded, which makes the theoretical analysis simpler. A numerical simulation is constructed to verify the applicability of the control law. The results show that all the variables of the BLDC motor are below the nominal values of the machine. Therefore, the physical implementation of the controller is feasible.