Abstract：The equivalent force control (EFC) method replaces the mathematical iteration with a force feedback control loop for solving nonlinear equations of motion in a real-time substructure test (RST) using implicit integration algorithm. In this paper numerical simulations and actual tests of structures in which the elastic element was used as the experimental substructure are introduced to further validate effectiveness of the EFC method. Firstly, the EFC method is introduced. Then, one single-degree-of-freedom (SDOF) system is used as an example to introduce the design method of the proportional-derivative equivalent force controller, and its stability is analyzed with the Routh stability criterion. Furthermore, numerical simulations of step, free-vibration, and forced-vibration responses of a SDOF system, in which the elastic element was used as the experimental substructure, are introduced. Lastly, actual RSTs of step, free-vibration, and forced-vibration responses of structure, in which the spring was used as the specimen, are introduced to further validate the effectiveness of the method. The analytical result shows that the feedback control system is stable as long as all control gains are positive. The numerical and experimental results show that the EFC method may exhibit excellent performance in terms of stability and accuracy.
2010, Vol. 29 
