Actively-controlled beds for ambulances

During transportation by ambulance,a patient is exposed to inertial acceleration when an ambulance decelerates or turns a corner.Such acceleration often gives a patient physical stress such as blood pressure variation or body sway,which causes strong pain,feeling of discomfort or sometimes critical damage for seriously injured persons.To reduce this undesirable effect of the acceleration,the authors developed the actively-controlled bed (ACB) which controls the posture of a stretcher in real time to reduce foot-to-head and lateral acceleration acting on a supine person.This paper describes development of the ACB,including control system design and performance evaluation.The control system is designed by Zakian's framework,which comprises the principle of matching and the method of inequalities,so that the design specifications on the tracking error and the motor torque are satisfied.From the results of driving experiments and simulation,it is estimated that the ACB can reduce the acceleration acting on a patient by 65% in the foot-to-head direction and by 75% in the lateral direction.