Abstract: First and second similar rotary encoders are interconnected such that the first encoder actuates the second encoder to advance one position for each half revolution of the first encoder. The first encoder is coupled to monitor the position of a rotary component. If the encoders are shifted or off-set by up to 90.degree. to either side of precise zero crossover alignment, a logic comparator modifies the reading of the second encoder to create a true read-out. During each half revolution of the first encoder, the second encoder should read even or odd if a proper phasing exists. If the second encoder produces an opposite reading, a phase shift is indicated. A logic circuit, preferably a microprocessor is provided for combining and modifying the readout in accordance with the logic. A microprocessor includes a program to continuously sample the position of the successive encoders with an internal table applied to the position readouts to provide a correct and true value of the rotary component position.

Abstract: A filament winding machine includes a servomotor connected to position a filament distributing carriage relative to a rotating mandrel to form a tubular member. An incremental encoder is connected to the mandrel and produces a pulse related output per mandrel revolution. An absolute encoder is connected to the servomotor and provides an absolute position number. The encoders are sampled at a fixed rate. A mathematical calculating circuit reads the incremental encoder and based on a predetermined movement design for the gear drive, the desired winding configuration and the like determines the proper position, which is compared to the absolute encoder reading to produce an error control signal to the servomotor. A preselected sequence of actual position numbers and the corresponding calculated position numbers are continuously updated in a temporary memory.