Thumb joint angle estimation for soft wearable hand robotic devices

There is a recent increase in development of compact soft wearable robotic devices that are used for rehabilitation and assistance of the hand. In order to rehabilitate or assist natural grasp tasks, the device requires monitoring of hand posture including finger and thumb joint angles. For estimating the finger and thumb joint angles without making the device bulky, bending sensors enable compact design of glove-type hand robotic devices; however, the estimation of the accurate thumb joint angles is challenging due to the highly coupled multi-degree of freedom movement. A bending sensor attached on any hand location tends to be deformed by movement of thumb in all DOFs, i.e., there is significant amount of coupling effect. It is important to find sensor locations that have minimal coupling effect to make the thumb joint angle measurement more accurate. In this paper, we present an experimental study on the optimal sensor location that causes minimal coupling effect on the thumb joint angle measurement.