Real-time electro-hydraulic hybrid system for structural testing subjected to vibration and force loading

Real-time electro-hydraulic hybrid system (REHS) with shaking table and force loading simulator is an essential experimental facility for evaluating structural performance subjected to simultaneously vibration excitation and force loading. The key feature of this paper is combination of a feedforward force controller including modified force inverse model compensator (MFIMC) and velocity feedforward compensator (VFFC) with an internal model control (IMC) to compensate the surplus force disturbance caused by active motion of shaking table and to obtain high fidelity force loading tracking performance. An acceleration tracking controller is also designed with modified acceleration inverse model compensator (MAIMC) to extend the acceleration tracking frequency bandwidth and to improve the acceleration tracking performance. The acceleration/force closed-loop transfer function model and their inverse model are identified and designed by multi-step recursive extended least squares (RELS) algorithm and zero magnitude error tracking controller (ZMETC) technology respectively because the identified transfer function model of the acceleration and force loading closed-loop systems may be a nonminimum-phase (NMP) system and their inverse model are instable. An acceleration and force modeling error compensator (MEC) are utilized in MFIMC and MAIMC to minimize the effect of the inaccuracy of identified model and designed inverse model. Experimental results obtained on a real uniaxial REHS with xPC rapid prototyping technology clearly demonstrate the benefit of the proposed compensation method.