Repositioning of a rigid body with a flexible sheet and its application to an automated rehabilitation bed

A new method for repositioning a rigid body with a flexible sheet is developed and is applied to a rehabilitation bed for turning and transferring a bedridden patient to alleviate bedsores and other ailments. The patient position and orientation are fully controlled by manipulating a flexible bed sheet under no-slip conditions. The use of a flexible sheet and the untethered nature of manipulation make the repositioning method particularly well suited to handling the human body. First, the basic design concept of the rehabilitation bed for automated patient repositioning is presented. The kinematic and static behaviors of body-sheet interactions are analyzed, and conditions for no-slip, quasi-static repositioning are obtained. In order to prevent injury to the patient´s fragile skin, it must be ensured that the patient does not slip on the sheet during repositioning. A prototype bed with a pair of servoed arms for manipulating the bed sheet is developed, and the no-slip conditions and the repositioning method are experimentally verified. A closed-loop control based on the measurement of a patient´s position and orientation is implemented and tested. Note to Practitioners-This work was motivated by the problems faced by bedridden patients as well as caregivers in the healthcare industry. The labor-intensive repositioning and transfer of bedridden patients are performed with a robotic system supervised by a single caregiver. Our repositioning scheme uses the bed sheet for rolling and moving the patient and closely mimics the current practice prevalent in nursing homes and hospitals. Our approach will be a natural alternative to manual repositioning and transfer and will be acceptable for most caregivers and patients. Initial prototyping and experiments have been completed in consultation with a professional caregiver.