Adaptive force control of a two-actuator system in dynamic structural testing

A model of a two-actuator system operating on a cantilever beam is presented. Results obtained from simulations of single and two-actuator systems operating on the beam confirm that a pole-placement self-tuner is adequate for controlling the applied forces in accordance with prescribed patterns even when the flow gain varies significantly and other nonlinearities are included. Application of the self-tuner to a nonlinear high order model is presented and discussed. It is found that the estimator may fail due to the low frequency of the demand signal but this failure can be avoided by using a variable forgetting factor or by resetting the covariance matrix. In the multivariable case, the results obtained demonstrate the feasibility of controlling a strongly coupled two-actuator system. It is found that by appropriate selection of the desired closed-loop polynomial matrix such that it contains a faster pole for the loop associated with the actuator closer to the root of the cantilever, the interaction effect can be reduced considerably