Sensitivity of a position servo system to variations in the constructive parameters in transient and steady state

Abstract

In this paper parameter sensitivity of constructive parameters are studied. A heavily loaded flexible ( ω h = 9.6 Hz) electrohydraulic position servo system typical in the paper industry was used in the research. There are cases where servo systems are critical either in the transient state or the steady state. The usual way of presenting the sensitivity of a servo system to variation in the parameters gives only the maximum values or the diagram of the sensitivity function. It is very difficult to find out the total effect of this data or its location in the time scale. The new method introduced in this paper gives a clear comparison of values of the parameter sensitivity both in the transient state and the steady state. With the new method, systems, or for instance different control methods in the same servo, could be compared quite easily. This method (like sensitivity theory generally) can be applied also to other physical systems provided that state models can be derived. Sensitivity analysis works well also when digitally controlled systems are used. This only brings one more nonlinearity to the system.