Multilayered Center-of-Pressure Sensors for Robot Fingertips and Adaptive Feedback Control

This letter proposes a sheet-shaped force sensor for covering a robot fingertip. The sensor consists of flexible materials and can be adaptively designed to the shape of the fingertip. When a load acts on the sensor, the contact position and both normal and tangential forces can be detected. Experimental results show the sensor characteristics as follows: The contact position can be estimated in high accuracy if it is enough separated from the boundary of the sensing area, the normal force up to 4 N can be estimated independent with the contact position, and the tangential force can be estimated by calibration while the sensitivity remains to be improved. This letter also presents two feedback control laws of a robot finger mounted with the proposed sensor. One is to keep both a contact position and normal force at constant to a target object, and the other is to keep rolling contact even if the object moves while touching. The availability of the control laws are confirmed through motion experiments.