A depressurization assistance control based on the posture of a seated patient on a wheelchair

For reducing the risk of pressure sore caused by long period sitting on a wheelchair, we develop a depressurization motion assistance system which is low cost and suitable for practical use. Our developing system consists of a seating cushion which the patient sits on and four air cells which can lift or incline the seating cushion. Each air cell is actuated by small air compressor, which can drive using batteries on the wheelchair respectively, and each compressor has a pressure sensor on its body. In this paper, our key ideas are two topics. One topic is mechanical design for practical use. We realize thin mechanism which enables easy implementation to the general wheelchair. For realizing this thinly design, we develop the tilt mechanism using elasticity of acrylic resin and the controller which uses only pressure sensors for estimating its lifting height and inclination. The other topic is assistance control scheme based on the patient's depressurization operation for increasing a rehabilitation performance. For realizing the proposed control scheme, we analyze the hip depressurization operation by the nursing specialists and use its results for estimating the patient's condition. Using our system, the patient can depressurize by his own will on the general wheelchair easily. The performance of our system is verified by experiments using our prototype.