Abstract: A circuit is disclosed for controlling the position or velocity of a moving object. The motion of the object may be linear or rotational. The object is moved by an electric motor, or linear actuator, which is driven by a power amplifier. The current output of the amplifier, which drives the motor or linear actuator, is controlled by an input signal based at least in part on the estimated velocity of the object. The control circuit includes a pair of integrators connected in series, the inputs to the integrators being dependent both on the current output from the amplifier, and on the difference between the output of the second integrator and the actual sensed position of the object. The velocity estimation circuit is thus based on a form of Kalman filter. The velocity estimator uses a model of the motor which is extremely simple, and which contains only constants. The velocity estimator can control the motor very accurately without detailed knowledge of the model of the motor.

Abstract: 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.