Sampled Data Feedback-Feedforward Control of Structures with Time Delays

A sampled data control algorithm taking into account external excitations was developed for structural engineering applications. The structure was modeled as a continuous system controlled by a digital control system. In addition to the feedback gain obtained using a conventional control design method, a linear feedforward gain was proposed to improve control efficiency. In order to ensure a satisfactory control performance, an adaptive scheme was developed to adjust this feedforward gain in real time according to the measurement history. The conventional sampled data linear quadratic regulator design was used as a baseline to evaluate the effectiveness of the proposed control algorithm. Some practical issues such as the effects of sampling frequency, time delay and actuator dynamics were addressed. This method was validated on the examples of two multistory shear beam lumped mass models. The numerical examples show that combining both the feedforward and feedback terms can improve the control efficiency significantly as compared to the case with feedback control only. It is also shown that the improvement on the control efficiency obtained with the proposed method is still noticeable when time delay is considered and compensated properly.