A mass measurement system using the self-excited oscillation of a relay feedback system was proposed. The system contains an on-off relay with dead zone and switches force acting on the object in relation to the position. An analytical study showed that the mass of the object is determined from the time interval measurement of the on-state and off-state periods. An apparatus was developed for experimental study. It uses a voice coil motor for generating force, and a pair of photo interrupters for detecting the switching positions. The effects of system parameters on measurement accuracy were studied experimentally. Under the tuned conditions, the measurement errors were within 0.2%. The effects of damping on measurement accuracy were also studied experimentally.

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Relay feedback was applied to measuring mass even under weightless conditions. A measurement object is driven by a force-output actuator. The motion of the object is controlled by a relay feedback system. The used relay element has dead zone and switches force acting on the object in relation to the position of the measurement object. The mass of the object is determined from the time interval measurement of the on-state and off-state periods. An apparatus was developed for experimental study. It uses a voice coil motor as an actuator, and a pair of photo interrupters for detecting the switching positions. The effects of system parameters on measurement accuracy were studied experimentally. Under the tuned conditions, the measurement errors were within 0.2[%]. Measurement on a base moving freely was also carried out.