Iterative drive-signal determination for nonlinear and deadtime plants

Considers the control procedure for a class of servohydraulic vibration test benches. These systems are highly nonlinear and strongly coupled MIMO-systems, making it impossible for conventional controllers to meet the requirements on the accuracy of the output signals. Instead a two-level strategy is used. The system test bench plus specimen is firstly controlled by underlying analog-controllers, and the input signals to this overall system are prefiltered by the inverse of a frequency-response model of this system to decrease the couplings between the control loops. Remaining errors are then reduced by a drive-signal iteration. The paper mainly deals with further developments of this approach. By extended identification nonlinear effects are included in the system model allowing a better control of the iteration process and making it possible to assure convergence even for strongly nonlinear systems