A two-degree-of-freedom ambulance stretcher suspension, Part 2: Simulation of system performance with capillary and orifice pneumatic damping

Part 1 of this paper gave an overview of the design and dynamics of a two-degree-of-freedom pneumatic stretcher suspension. Part 2 reviews pneumatic damping methods and then investigates system isolation performance using capillary and orifice damping restrictions. These restrictors are compared by numerical simulation of the suspension response when subjected to vertical transient inputs from the ambulance floor. Very good isolation of the stretcher patient is shown to be possible when a suitable damping restriction is used. Brief observations are also made regarding expected suspension performance in pitch and the potential improvement from introducing semi-active pneumatic damping. Part 3 will report results of suspension tests on a laboratory shaking table and in an ambulance.