Falls in nursing homes and hospitals are common occurrences and a significant problem in the healthcare industry. A large number of accidents occur during sit to stand transitions. Not only patients with lower limb weakness are prone to injury after falls, but the healthcare workers are prone to musculoskeletal injuries when helping individuals transitioning from sitting to a standing position. Sit to stand devices are currently being used in hospitals, but the current models are expensive and do not allow patients to use any of their lower body strength in the process. We proposed the design of a device adjustable to each user in order to maximize the use of their own strength and allow them to stand up comfortably and safely. The design is innovative, customizable, and enables the device to be used as a walker as well. We propose an actuation system that combines a set of elastic bands to modulate the force used for lifting and gravity compensation. The system comprises of two sets of rubber bands that can modulate the force profile as a function of the height of the seat. Furthermore, this device offers a potential solution to the disproportionate number of workers injured in the healthcare field during lifting and assisting patients during the sit to stand transition.The adjustable actuation system is the defining feature of this device. The lifting system will consist of an L-shaped seat connected by two rods, forming a four-bar mechanism with the chassy. The rods are connected to the frame with a hinge on either side of the rod. The purpose of the hinges is to keep the seat always parallel with the floor. Each of the rods is provided with an adjustable slider. The sliders are movable in order to adjust the moment arm of the force. Lift bands will be connected to the sliders and to the frame. The lift band will apply an upward force to cause the seat to move. The lower band will apply a downward force increasingly higher as the seat nears to top to slow down the velocity of the seat.This actuation mechanism can be very customizable and provide a reliable and comfortable sit to stand movement. It can be customized by differing the strengths of the bands, changing the slider length, and/or changing the number of bands used. The lower band provides the system with a way of slowing itself down and flattening the curve so that users are elevated without being propelled from the seat.Future work will concentrate on the use of multiple rubber bands to build further customizable force profiles. This will allow for adjustments of the moment arm and remote induction of net effective torque.

Sit to Stand Gait Trainer: Modulation of Lift Force via Elastic Network

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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