Multi-objective optimization design of hydraulic servo screw based on MOPSO algorithm

Hydraulic servo screw (HSS) is a hydraulic pilot structure with high power-to-weight ratio and fast response. Its performance is strongly affected by several coupled structural parameters. This study develops a Pareto-based multi-objective particle swarm optimization (MOPSO) method for HSS design. A co-simulation model is first established using the bond graph method and AMESim, and its feasibility is verified experimentally. The spiral groove angle, initial opening, and orifice radius are selected as design variables. Rise time, overshoot, and hysteresis are defined as independent objectives. A resonance stability criterion is imposed as a feasibility constraint. MOPSO is used to obtain the Pareto solution set, and NSGA-II is introduced for comparison. TOPSIS is then used to determine the final compromise design. Experiments show that the optimized prototype reduces the rise time from 25.2 to 20.9 ms. The amplitude bandwidth increases from 58 to 63 Hz, while the phase bandwidth increases from 66 to 74 Hz. The hysteresis remains nearly unchanged. These results demonstrate that the proposed method improves the dynamic response and frequency tracking capability of the HSS.