Abstract

The conventional gurneys used in hospitals to move patients from room to room have one main disadvantage: they are difficult to control. A typical gurney has a form of an oblong table moving on four castor wheels. The vehicle is difficult to maneuver, especially on corridor turns, and usually requires two operators — each at one end.

Dr. J. Bleicher from the St. Joseph’s Hospital in Omaha, Nebraska suggested a new type of a self-propelled gurney which would be a cross-breed of a motorized wheelchair and a gurney.

A new type of a gurney would have two additional wheels in the center of the gurney, each connected to a separate DC motor. The torques developed by the motors would be controlled by one operator using a joystick. Applying opposite torques to the controlled wheels would rotate a stationary gurney in place, or would curve the path of a moving gurney.

The position of two additional wheels can be changed, so that the gurney can move sideways, translate in chosen direction or move along a curvelinear path.

The work presented in the paper contains an analysis of the dynamics of such a gurney. A mathematical model of the vehicle was developed to check how much effort is needed on the part of the operator in straight path motion and during negotiating a corner.

The most difficult part of the modelling was a proper description of forces and torques exerted by the ground on the wheels.

The differential equations of motion of the gurney have been numerically integrated, and the dynamical response of the vehicle studied. The results of the computer simulation show a transient oscillatory response of the castor wheels (shimmying) which can be controlled by a proper choice of design parameters of the vehicle.

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