Noise tolerant brushless motor position monitoring apparatus and method

Abstract

A noise tolerant motor position monitoring circuit having a digital filter section receives and filters noisy hall effect sensor inputs for use in determining rotational motor position. The motor position monitoring circuit exchanges information and instructions with a microprocessor which utilizes the motor position information to calculate motor distance traveled, motor speed, etc. The hall effect sensor signals are noisy due to the particular environment in which the sensed motor is placed, such as in industrial process and automotive applications. Each monitored segment of rotation corresponds to the motor rotational switching sequence of a motor driver circuit, a digital counter generates a running total rotational count and increments or decrements the total count depending upon the direction of motor rotation. A programmable digital filter time constant is generated and, via state machine operation, a hall sensor signal duration range is implemented for differentiating valid motor rotation signals from spurious noise signals. The desired operating range is programmably altered via the microprocessor and programmable digital filter time constant to allow the motor position monitoring circuit to operate for a broad range of motors having divergent characteristics.