Driver electronics for efficient low noise stepper motor operation

Stepper motors are a very convenient and economical solution for accurate positioning applications where long lifetime and low wear are required. Their particularly simple open-loop operation reduces the number of control components to a minimum. However, the price for open-loop operation is an overdimensioned system in terms of available motor torque and electric input power in order to satisfy step synchronicity. Consequences of an over-powered motor are waste of energy, dissipative heating and excessive noise. Closed-loop motor commutation in brushless DC motors (BLDC) is typically accomplished with an appreciable electronic effort based on evaluation of digital Hall sensor signals which correlate with discrete rotor positions. Alternatively, sensorless commutation estimates the rotor movement from an analysis of the phase currents. This method fails at slow or no movement due to lack of induced voltage. The goal of this Master thesis is evaluation and analysis of optimum driver circuitry which attempts to overcome the disadvantages listed above. The drive system is required to be highly robust (at automotive conditions) with minimum power consumption, reduced noise and lowest count of components.