Development of elastic finger-like sensor for control of grasping force (Control of grasping force in arbitrary direction using spherical sensor with strain gages arranged on perpendicular axes)

A two axial finger-shaped sensor is developed for controlling grasping force so that an object is lifted with appropriate grasping force at any grasping direction. It consists of silicone rubber having spherical surface and strain gauges arranged in two perpendicular axes. First, the relationship between stick area and the internal strain distribution of the sensor are calculated using FE (finite element) analysis when the sensor is in contact with an object. It is necessary to detect the shear strain distributed in the sensor in order to grasp the object with appropriate force. Then, the method for estimating stick area of the sensor is proposed using FE analysis. Finally, the grasping force control is achieved using the constructed system. It is shown that arbitrary objects with various weight and friction coefficients are lifted using the developed sensor and control method.