Designing optimal controllers for nonlinear frames by considering the effect of response feedback

The effect of response feedback on designing optimal controllers for nonlinear frames has been studied. Different combinations of response feedback have been used in the performance index. The Newmark based nonlinear instantaneous optimal control algorithm has been used as the control algorithm in controlling the response of an eight-story bilinear hysteretic frame subjected to white noise excitation and real earthquakes, and controlled by either eight actuators or a single actuator. While the objective has been to minimize the maximum control force for reducing the maximum drift to below the yielding level, the distributed genetic algorithm (DGA) has been used to determine the proper set of weighting matrices in the performance index. Results show that the performance of the active control system depends on the combination of response feedback, where the velocity feedback has been more effective than acceleration and displacement. Also, although using the full feedback of response in the performance index leads to the design of optimal controllers that require the smallest control force, it is costlier, because it requires more online measurements. Finally, it has been concluded that amongst all possibilities, using only velocity feedback can provide the best results regarding the maximum required control force and online measurement, simultaneously.