| 摘要 |
The invention provides a method and apparatus for determining the angular displacement of a rotating shaft, and for commutation of a brushless motor. At least two analog sensors, mounted near the shaft, generate phase-displaced analog signals responsive to the angular position of the shaft. A logic circuit produces a digital code indicating the region of the cycle in which the shaft is instantaneously located. An analog multiplexor selects a unique pair of analog signals from the group of the original analog signals and their analog complements, according to the value of the digital code. An analog to digital converter then generates a digital signal proportional to the quotient of the analog signals produced by the multiplexor, and this digital signal, together with the digital code, is used to activate an address in a memory device. The memory device, such as an EPROM, is programmed with a large number of binary digits, which define a train of pulses. As the shaft turns, the addresses in the EPROM are activated in a predetermined order, producing a train of pulses whose frequency is directly proportional to the angular velocity of the shaft. The EPROM can be programmed to generate parallel trains of pulses, including "quadrature" pulses, which encode the direction as well as the displacement of the shaft, and commutation pulses, for controlling a brushless motor. The circuit therefore can be used to monitor the angular displacement of the shaft and, at the same time, to control the motor which drives that shaft.
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