Design of Vibration-Isolating Bed for Ambulances Using Inerter

A vibration-isolating bed for ambulances using an inerter is proposed. The structure of the bed is assumed to consist of a bottom frame fixed to the ambulance floor and an upper frame on which the stretcher is placed. Both are connected only by the suspension, including the inerter, in the vertical and horizontal directions. Because the inerter can reduce the gain of the high frequency band and delay the response, the time when maximum acceleration is applied to bed can be shortened by passively in a limited space in ambulance. We consider the bed as a plant and the suspension as a controller, and then formulate the state equation. To reduce the acceleration within the movable range of the bed, the controller that minimizes the H∞ norm of the transfer function from the external force acting on the bed to acceleration is calculated by bilinear matrix inequality. The transfer function determines the structure and coefficient of the suspension. The usefulness of the bed is verified by numerical simulations.