Stabilisation of control systems by the use of driven limiters

Phase-advance stabilisation of servosystems frequently fails, owing to the consequent accentuation of the high-frequency spectrum. The use of limiters controlled by the error signal is shown to be capable of removing this defect. The system is linear when considered on a describing-function basis, and it is shown to confer a high degree of stabilisation on both analogue and practical servosystems. The system is shown to possess a similar phase characteristic to that of the linear counterpart, but to give a gain characteristic that falls with increasing frequency. The calculated and measured results are shown to be in agreement on a describing-function basis. The effect of on the noise system is examined briefly, and noise is shown to have less effect than when the linear circuit is used. Comment is made upon the effect of preceding nonlinearities.