A High Speed Digital Servo

This paper describes a high speed digital servo system which is used mainly as servo drives in numerical control systems.A direct current servo system, when a quick response is required, often requests both position and velocity detectors. Resolvers and direct current tacho-generators are widely used for them. The former has an upper speed limit, and so gears are put between the detector and the motor shaft. As a result, a high performance cannot be expected because of the dead zone of the gears. Also these detectors have mechanical brushes for the transmission of electrical signals so that many troubles occur from non-working contact of brushes.An optical detector is developed for non-contact measurement of position and velocity. Quantization errors due to quantized position and velocity signals in the servo loop are evaluated and the upper bounds of the errors are shown as a function of the damping coefficient of the linear system. The experimental results of the servo system with the quantized position and velocity detectors are given.A pulse-drive servo system which is a digital servo system containing only switching elements in the circuit is proposed. The servo system is completely free from hunting due to the variation of system characteristics because the circuit is constructed with logical elements. The functional descriptions and the experimental results of the system are given.