Development of a pneumatic-lifting magnetorheological semi-active suspension towards height adjustment capability

Single-chamber air springs (SCAS) suffer from large dynamic stiffness increments and rubber bladder failures. This paper proposes a Pneumatic-Lifting magnetorheological semi-active suspension (PLMRD) integrating a mechanical spring, a magnetorheological damper (MRD), and a rigid Pneumatic Lifting Device (PLD). The mechanical spring bears the main static load and provides fail-safe support in the event of pneumatic leakage. By replacing the rubber bladder with a rigid cylinder and mechanical spring, the large dynamic stiffness increment of SCAS is avoided. A Bingham Plastic (BP) model and a static stiffness model are established for the MRD and PLD, respectively. A combined LuGre friction and fractional-order Kelvin–Voigt model is developed to capture the PLD’s amplitude- and frequency-dependent dynamic stiffness, and the model is validated experimentally. A Displacement-Sensitive Skyhook (DS-Skyhook) control strategy is designed based on a quarter-car model to adapt damping according to suspension deflection. A quarter-car test shows that compared to the passive SCAS, the passive PLMRD reduces the root mean square (RMS) of the sprung mass acceleration by 16.41%; with the conventional Skyhook control, the reduction is 33.98%, and with the DS-Skyhook control it reaches 36.69%, while maintaining stability over a wide amplitude range. The PLMRD also achieves a 103% increase in static lifting speed. The proposed structure and control effectively address key drawbacks of conventional air suspensions.