Human-interactive control of a hydraulically actuated patient transfer assist device with redundant obstacle sensing

摘要

A significant need has been identified for an improved device for transferring mobility limited people, for example, from a bed to a wheelchair, a wheelchair to a toilet, a floor to a wheelchair, or a wheelchair into a car. A new prototype concept patient transfer assist device has been developed, using electro-hydraulic pump controlled hydraulic actuation. With such a powerful device working in a relatively delicate and unstructured environment with both the patient and caregiver in its workspace, a form of interaction control to manage any external interaction forces is necessary. This paper presents a form of interaction control using redundant sensing of obstacles, using both proximity sensing from an ultrasonic sensor and external force sensing from a load cell. The control strategy is based on impedance control with force feedback. Experiments on one degree of freedom of the patient transfer device show that the control strategy can significantly reduce external interaction forces, as long as one or both of the sensors detects the obstacle. Further investigations will incorporate the redundant interaction control into multiple degrees of freedom of the patient transfer assist device system, and human operator experiments will be performed.