A Controlled Mechanical–Electronic Hybrid Commutation Theory and Position Sensorless Control

Abstract

Both brushed dc motors and brushless dc motors have a wide range of applications, but mechanical commutating devices have the problem of harmful commutation arcs, and electronic commutating devices increase the cost of control systems. The uncontrolled mechanical–electronic hybrid commutating device passively controls the voltage of the freewheeling commutator segment through the capacitor, but the capacitor, inductor and resistor with fixed parameters in the freewheeling circuit are difficult to apply to the entire operating range. Therefore, this article proposes a controlled mechanical–electronic hybrid commutating device and a position sensorless control method. The mechanical component realizes the conduction mode of 120 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> square waves through brushes and a mechanical commutator. The electronic component actively controls the voltages of the commutator segments through the power electronic switches in the commutation circuit so that the brush and the newly separated commutator segment remain equipotent, and the gap between them does not bear voltage, which is equivalent to operating in the brush-slip ring state and completely solves the problem of sparking and arcing during the commutation process. The controlled hybrid commutating device requires only two switches to obtain the same commutation effect as the electronic commutating device with six switches and does not require a position sensor or control chip, which reduces the system cost. The validity and feasibility of the controlled mechanical–electronic hybrid commutation theory and device are verified by experiments.