Stabilization of a servomechanism subject to large amplitude oscillation

The saturation of an amplifier is found to cause large amplitude oscillations in a conditionally stable servomechanism. The employment of a suitable nonlinear element in the stabilizing network may prevent such oscillations. For a particular system containing a saturable amplifier, frequency response analyses are used to find the magnitude and frequency of the oscillation and to determine the design of a nonlinear filter which will prevent large amplitude oscillation. Laplace transformation theory is employed to justify the use of a frequency response analysis, and to prove that the combination of a saturable amplifier and an unstable inner loop will cause oscillations in both conditionally and unconditionally stable systems. Results obtained from an analogue computer are compared with the results of the frequency response analyses.