Abstract: A stability control system for a vibration test device having an acceleration control system and using an electro-hydraulic servo-system is disclosed. The stability control system comprises a model operation circuit which simulates a model response corresponding to value representing the states of a vibration table in response to command signals produced from a signal generator and associated with the displacement, velocity and acceleration of the table, and a gain-adjusting circuit which produces gain-adjusting signals to gain-adjusting sections in response to model response signals produced from the model operation circuit, state-representing signals produced from a feedback circuit and the command signals produced from the signal generator. The gain of each gain-adjusting section is automatically controlled in such a manner that the state-representing values of the parts of the control system coincide with the corresponding state-representing values in the model operation circuit.

Abstract: A servosystem in which means are provided so as to prevent impartation of an excessively high acceleration to its movable part even when an abnormal input signal is applied to the servosystem. The apparatus comprises an acceleration limiter circuit which modifies such an abnormal input signal so that an acceleration higher than a predetermined level may not be imparted to the movable part.