Mechanism and control strategy design of a multi-position nursing bed for bedridden elderly care

Nursing beds equipped with multi-position adjustment capabilities play a crucial role in preventing pressure ulcers and promoting blood circulation in bedridden patients. This study presents a multi-position nursing bed that integrates back-lifting, leg-bending, and lateral positioning functions, ensuring smooth and stable transitions between various care postures. The back-lifting and leg-bending modules are designed using planar linkage mechanisms, while the lateral positioning module combines planar linkage mechanisms with a flexible bedsheet, enabling more compliant posture adjustments. Kinematic analysis of the back-lifting and leg-bending modules is performed using the generalized transmission ratio method, followed by the development of the corresponding dynamic model. For the lateral positioning module, a comprehensive geometric analysis of the positioning process is carried out, leading to the derivation of the input-output motion mapping. In the control system design, an adaptive fast nonsingular terminal sliding mode control (AFNTSMC) strategy is proposed for the back-lifting and leg-bending modules, while a PID control strategy is employed for the lateral positioning module. Finally, a functional prototype of the nursing bed is developed, and its posture transformation capabilities are validated.