Indirect adaptive robust dynamic surface control of electro-hydraulic fatigue testing system with huge elastic load

In this article, an electro-hydraulic-based fatigue testing system is considered. Electro-hydraulic system suffers from internal parameter uncertainties and external disturbances. Indirect adaptive robust control has been proposed to address these problems; however, since the mathematical model of this electro-hydraulic system has an order of four, the inherent "explosion of terms" problem makes the controller hard to design, and a large computational cost is needed. Thus, dynamic surface control is utilized in the design procedure of indirect adaptive robust control. The proposed indirect adaptive robust dynamic surface controller simplified the design procedure and decreased the computational cost of the controller. Furthermore, due to the fatigue of the elastic load, fast internal parameter change is encountered in this system. A fast parameter estimation scheme is proposed to adapt to the parameter change for a better estimation performance. For the mechanical system, a change in the hydraulic circuit is made to address the problem of chattering and impact caused by huge elastic load and to simplify the system model at the same time. Simulations and experiments show that the proposed controller achieves a better parameter estimation and trajectory tracking performance.