Magnetorheological energy absorbers (MREAs) are widely used in vertical shock mitigation systems for occupant protection. However, conventional soft landing control strategies are generally derived from rigid-body or single-degree-of-freedom assumptions, and the influence of occupant compliance on control effectiveness remains insufficiently clarified. This study proposed three semi-active control strategies explicitly considering occupant biodynamics: occupant-compliance-based optimal constant controllable damping force control (OC-OCCDF), occupant-compliance-based optimal constant-load control (OC-OCL), and minimum occupant injury control (MOI). A coupled five-degree-of-freedom shock mitigation model integrating a four-degree-of-freedom occupant biodynamic representation was adopted. The results showed that occupant compliance changed the force requirement for soft landing, such that control parameters derived from an ideal SDOF system could no longer guarantee zero terminal seat velocity. The proposed OC-OCCDF and OC-OCL strategies restored soft landing performance, while the MOI strategy achieved superior biomechanical injury mitigation.
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