Development of a Variable Stiffness Handle to Reduce the Wheelchair Caregiver’s Pushing Force

Abstract

It is necessary to reduce the large burden on caregivers pushing wheelchairs. A spring handle has been proposed as a solution to reduce burden on caregiver ’s upper limb. A spring handle consists of a spring built into the handle. By using this handle, the integral value of the pushing force can be reduced at a steady velocity. However, during acceleration, the integral value of the pushing force may become large because of the large contraction of the spring. Therefore, it is considered effective to reduce the burden by increasing the spring constant during acceleration and decreasing it at steady velocity. The objective of this study was to develop a variable stiffness handle that can switch the spring constant between the acceleration and steady velocity sections. Experimental results suggest the effectiveness of the variable stiffness handle.