Improved feedforward inverse control with adaptive refinement for acceleration tracking of electro-hydraulic shake table

Abstract

Shake tables are essential facilities in the laboratory for evaluating structural performance subject to vibration excitation. In this paper, to improve the time waveform replication accuracy of electro-hydraulic shake tables (EHSTs), an improved feedforward inverse control algorithm with adaptive refinement is proposed. The EHST system transfer function and stable inverse model is firstly estimated and designed by multi-step recursive extended least squares algorithm and zero magnitude error tracking controller technology, respectively. To reduce the side effect of model identification errors between the estimated and actual system, a system model corrector is further identified based on the previous estimated EHST model and an inverse corrector is obtained so as to constitute the improved feedforward inverse controller (iFIC) by cascading the inverse corrector to the previous designed inverse model. Then, an adaptive refinement controller using a least mean square algorithm is applied to the iFIC controlled system to cope with system uncertainties and nonlinear effects. Therefore, the proposed algorithm combines the merits of feedforward inverse control and adaptive control. Finally, with the help of xPC rapid prototyping technology, experiments are conducted on a real uniaxial EHST system and the experimental results demonstrate that the proposed algorithm exhibits a better tracking accuracy than the conventional controllers for shake tables.