The analysis and synthesis of contactor servomechanisms
This investigation is concerned with the analysis and synthesis of contactor servomechanisms. The techniques employed are based on Kochenburger's quasi-linear representation of the contactor describing function for sinusoidal input signals to the contactor. The frequency-response method of analysis and synthesis, which has been found practical for treating linear servomechanisms has been applied by Kochenburger to the contactor servomechanism and is explained here. By this method it is possible
... to determine whether the system possesses absolute stability. The root-locus method of synthesis which has been applied to linear servomechanisms is applied to the contactor servomechanism. The root-locus describes the roots of the closed-loop system for all values of the control signal amplitude. The root-locus method is valuable when considering the problem of relative stability. For a simple contactor with no hysteresis effect, Kochenburger's vector form of the contactor describing function can be used directly to obtain the root-locus. The contactor appears as a variable gain element for the various control signal amplitudes. The contactor has no effect on the open-loop roots but the variations in the contactor gain cause the roots of the closed-loop to travel along the root-locus obtained from the open-loop roots of the system. The root-locus can also be obtained when the contactor possesses hysteresis. Kochenburger's vector form is modified to the Laplace transform form of the contactor describing function. This form of the describing function shows that not only are the positions of the roots varying for the closed-loop but also for the open-loop. A model was constructed to check some of the theory. The assumed over-all open-loop transfer functions approximated the actual. Even for the assumptions made, the experimental work has verified qualitatively and to some degree quantitatively the prediction of the model performance.