Abstract: The absolute encoder utilizes two or more sensors per track and the output of each sensor is modulated by the track to generate a multiphase analog signal from each track. An analog to digital converter converts each analog signal to a digital value. The multiphase cyclic digital values are combined into a single linear output per track that increases linearly from zero to a maximum over the full span of the measuring scale. Corrections are made for zero drift in the analog signals, for changes in amplitude (gain) of the analog signals and for deviations in the linear values from a perfect straight line. When measuring rotary displacement the methods disclosed may be used to combine the outputs of the geared scales.

Abstract: An incremental encoder comprises a rotatable disc having an axis of rotation and a plurality of circumferentially arranged slots formed in the disc at equal angular increments. Light source is so positioned on one side of the disc so as to illuminate the slots. A first light sensor is so positioned on the other side of the disc as to receive light from the source means transmitted through the slots. A second light sensor is so positioned on the other side of the disc farther from the axis than the first sensor so as to receive light from the source transmitted through the slots out of phase with the light transmitted to the first sensor. A third light sensor is so positioned on the other side of the disc as to receive light from the source transmitted through the slots for control purposes.

Abstract: A multi-turn shaft position encoder employs a plurality of encoder discs with successive speed reductions of 1:2.sup.n and the generation of n+1 bits of binary data representative of the angular position of the respective discs as the input shaft rotates. Specifically, a high-speed disc is coupled to an input shaft and low-speed disc means is coupled to the input shaft with a speed reduction of 1:2.sup.n relative to the high-speed disc. At least one group of n+1 bits of binary data representative of the angular position of the high-speed disc are generated as the input shaft rotates. A group of n+1 bits of data representative of the angular position of the low-speed disc means is generated as the input shaft rotates. Thus, the low-speed disc is divided in to 2.sup.n units per revolution but produces 2.sup.n+1 bits of data. The data is generated by the encoder in unit distance code and is then converted into fewer bits of data in natural binary code.

Abstract: An induction motor is coupled to a movable load to be positioned. The induction motor has two or more stator windings. Alternating current power is connected to the stator windings to energize the motor. A transducer senses the position of the load. Responsive to the transducer, the alternating current power is disconnected from the stator windings as the motor approaches a predetermined load position. Also responsive to the transducer, a direct current energy storage device is connected to the motor as the motor approaches more closely to the predetermined load position to apply direct current to the stator windings and to stop the motor at the predetermined load position. Preferably, the storage device comprises a capacitor connected in series with a rectifier across two input terminals of the motor and the storage device is connected to the motor by a relay coupled from the junction of the rectifier and capacitor to one of the input terminals of the motor.

Abstract: A first signal representative of the position of a movable member, such as a machine tool slide, is generated. A plurality of second signals each representative of one or more positions and one of a plurality of actuatable output switches is stored in an addressable memory. The first signal is compared with each of the plurality of second signals stored in the memory. Responsive to the comparison, the output switch represented by one of the plurality of second signals is actuated when the one or more positions represented by such one of the plurality of second signals coincides with the position represented by the first signal.