A mechanism design of waist power assist suit for a caregiver by using torsion springs

We currently develop a motor-driven power assist suit for a caregiver that helps his/her waist strain in heaving a load Since the total weight is about 15 kg of which dominant elements are the actuators, any lightweight solution is required toward a practical use in a hospital or at home. Especially, a torque requirement to assist waist muscular power in typical personal care tasks is over 100 Nm, and a weight of high-torque motor tends to be large for a wearable robot suit. Then, we consider a mechanism design with torsion springs as an additional torque supplier to reduce torque requirement for motors. As a first step, in this paper, we design a prototype with torsion springs to investigate which location and how many springs are appropriate. The performance is evaluated with surface EMG in which the activities of some muscles including erector spinae muscles that are used in a lifting motion are observed.