Hybrid controller of magnetorheological semi-active seat suspension system for both shock and vibration mitigation

The impact caused by the detonation of landmines and improvised explosive devices may directly lead to spine fracture and injury of seated occupants on special vehicles. The vibration transmitted from the uneven road surface is another important factor affecting ride comfort/health, on the other hand. Aiming at minimizing the injury to spine and "discomfort" due to the shock and vibration from the terrain or blast, a magnetorheological (MR) energy absorber (EA)-based semi-active seat suspension system for both shock and vibration mitigation is proposed and investigated in this article. The proposed MR semi-active seat suspension system consists of a coil spring supporting the seat and the occupant, a MREA, and a fail-safe EA rod. The dynamic model of the MR semi-active seat suspension system with a 4-degree-of-freedom lumped-parameter model for seated occupant is established. A concept of integrated hybrid controller combining strategies for shock and vibration control is proposed and designed. The hybrid controller employs the skyhook control strategy to achieve vibration control and the "soft-landing" control strategy to achieve shock control, and it switches between the two control strategies according to the system dynamic states. Based on the real-time velocity of the seat, the motion process of the "vehicle-seat-human" system can be pre-judged, and the critical point for switching the two control strategies can be determined. A feedforward control strategy based on a hysteresis model with a resistor-capacitor (RC) operator is proposed and realized to high-efficiently output desired damping force of the hybrid controller from the employed MREA. Sequentially, both ride comfort (i.e. vibration control) and vertical safety (i.e. shock control) of the MR semi-active seat suspension system are analyzed and evaluated under different excitations.