Caretaker-Machine Collaborative Manipulation With an Advanced Hydraulically Actuated Patient Transfer Assist Device

A significant market need has been identified for an improved assist device for transferring mobility limited patients, particularly those who are heavier or bariatric. This paper discusses our needs assessment for a new patient transfer assist device (PTAD), an initial design for a multiple degree of freedom hydraulically actuated device, and possible solutions for the caretaker interface design. The relevant patient population includes those with spinal cord injuries, neuromuscular disorders, and the elderly; most patients are wheelchair users and unable to perform independent transfers. The caretaker interface design for the PTAD presents a unique challenge in terms of human-machine collaborative manipulation, as well as control of a powerful and intrinsically stiff machine in a delicate environment with both the caretaker and patient in the workspace. This paper presents a needs assessment to determine the specific problems with the antiquated current market patient lifts, as well as user input on proposed improvements. It also presents the design of a functional first prototype PTAD, a mechanical simulation, preliminary simulation results on an impedance control approach, and next steps toward design and implementation of a caretaker- and patient-friendly operator interface and control system.