Suspension height tune-up with constant stiffness properties through motor-driving double-gas-chamber hydro-pneumatic strut: Experimental study and modeling

In vehicle suspension, it is important to achieve continuous height adjustment to reduce the possibility of unstable and off-tracking caused by uneven postures. It is usually solved by air suspension, in which the dynamic properties will change under the adjusting process and these changes are not conducive to control. Considering the above, in this paper a double-gas-chamber hydro-pneumatic strut (DHPS) with the constant and/or predicted stiffness during continuous height adjustment, as masses (oil and gas) conversation are guaranteed in the whole system, which is achieved by volume variation of auxiliary gas chamber through motor-driving piston, is proposed. The dynamic properties and mathematic model of the proposed DHPS are investigated and established through bench test applying to the designed prototype. The system response speed has been evaluated through experimental data that for harmonic test the system can reach the stable condition in 1 (2) cycle subjected to 50mm/s (25mm/s) motor-driving piston moving speed. Finally, a typical quarter-car model is utilized to evaluate the performance of the proposed DHPS. It has been shown that the system takes 0.40s and 0.50s (200mm/s moving speed), and 0.76s and 1.36s (40mm/s moving speed) subjected to step test (25 and 50 mm), respectively.