LAUSR

Instability caused by emergency braking and steering during ambulance operation would easily lead to a sharp rise of blood pressure in patient’s head, which would further cause a secondary injury to the patient. Furthermore, the vibration generated by uneven road would result in patient’s nausea and deterioration of patient’s condition. This article proposes a pitch–roll-interconnected hydro-pneumatic suspension system which can achieve the resistance control for pitch, roll, and bounce modes of ambulances to improve the stability and attenuate the vibration for the lying patients. The ambulance with pitch–roll-interconnected hydro-pneumatic suspension is characterized by 7 degrees of freedom dynamic model, in which the characteristics of pitch–roll-interconnected hydro-pneumatic suspension are explicitly formulized using hydrodynamic equation derivation. A motion-mode energy spectral density method is proposed to decouple the vibration energy for bounce, pitch, and roll modes in frequency domain. Subsequently, the parameter design approach incorporated with the suspension characteristic equations and motion-mode energy spectral density method is also presented to optimize the lying patient’s ride comfort and ambulance’s handling stability. The numerical simulation results show that the proposed pitch–roll-interconnected hydro-pneumatic suspension system can simultaneously provide pitch–roll–stiffness and damping without generating additional bounce-stiffness, resulting in superior ride comfort and handling stability compared to the conventional suspension.