Importance

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Abstract

A control system for a brushless DC torque motor is disclosed. The motor comprises three coils, the wires at the end of each coil being brought out and connected to an amplifier that provides the current control signals to the coils. These control signals are generated based on a combination of commutation input command bits which are effectively multiplied by a pulse-width modulation control input word to form a pseudo-sine wave current signal at the input to each coil. By combining the pulse width modulated (pwm) current command word with an input command which defines a square wave, a pseudo-sine wave signal is provided for each coil which effectively controls the current to the motor coil in accordance with the value of the pwm commands. In each amplifier, the current control signal is compared with a servo feedback signal from the coil to define an error signal which, when amplified, becomes the actual input current signal to the coil. In order to allow for the fact that this is a bipolar system, a dead zone is defined between positive and negative drive signals so that no overlap occurs in the signals which could cause undue stress to the output transistors. Appropriate protection is also provided against numerous fault conditions, for example, any open circuit or short circuit condition.

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First Claim