Sensitivity of starting force, piston mass, and load pressure in nonlinear electro–hydro–mechanical hybrid power systems

Global energy conversion systems increasingly rely on highly integrated thermo–electro–mechanical processes, in which nonlinear vibration strongly affects efficiency, stability, and power density. Nonlinear electro–hydro–mechanical hybrid power systems (NEHMS), without crank mechanisms, exhibit strong multifield coupling, while the sensitivity of their dynamic behavior to key parameters remains insufficiently understood. In this study, a unified nonlinear multiphysics framework is developed using real-time MATLAB/Simulink–AMESim cosimulation to couple a nonlinear vibration combustor, a permanent magnet linear generator, and a hydraulic recovery subsystem. The model is validated experimentally, with an average error below 5%. Sensitivity analyses are performed for three key parameters: starting force, piston assembly mass, and hydraulic load pressure. Results show that starting force is the dominant control parameter. Increasing the starting pressure from 9 MPa to 10 MPa raises the peak motor power from 2804.9 W to 3729.3 W during compression and from 7309.2 W to 8875.4 W during expansion, while the maximum hydraulic output power increases by 816.6 W. Increasing piston mass from 4.5 kg to 5.5 kg improves the combined system efficiency from 42.84% to 44.98%, but reduces piston velocity and peak power density. In contrast, changing hydraulic load pressure from 12 MPa to 15 MPa causes little change in total efficiency, indicating that it mainly redistributes energy between the electrical and hydraulic subsystems. These results provide quantitative guidance for NEHMS optimization.