Robust MPC-PIC force control for an electro-hydraulic servo system with pure compressive elastic load

For accurate force tracking of an electro-hydraulic servo system (EHSS), this paper presents a state-space representation of model predictive control (MPC). EHSS is highly nonlinear because of the transmission nonlinearities, variations of the trapped fluid volume, internal friction, and nonlinear load-based nonlinearities. A nonlinear mathematical model is built, and model parameters are identified using a grey-box system identification method. Then MPC is firstly designed, and to improve the robustness, a nominal mathematical model with proportional integral control (PIC) is constructed for MPC design. Three implementation scenarios are investigated in MATLAB/Simulink and real-time LabVIEW-based experimental rig. The control performance is compared between and among PIC, MPC, and hybrid MPC-PIC controller.