Development of tactile force sensor for robot finger that can measure force and its center position unaffected by the contact area with the object and pressure distribution

Abstract

As an alternative to the paralyzed arm of hemiplegics, if there is a robot arm and hand that is the same size as a human arm and hand, can grasp daily necessities and work cooperatively with the user’s healthy arm, it would help hemiplegics lives. If the weak force on the grasped object and how the grasped object is pulled can be detected on the robot's finger surface, the robot can grasp objects of various hardness with appropriate forces according to the work, prevent dropping the objects and estimate the user’s handling intention to the objects. The purpose of this study is to propose and develop a small and thin tactile force sensor and a calibration method for correcting nonlinearity to realize the measurement of force and its center position on the robot's finger surface irrespective of the loading area and pressure distribution, and to confirm the usefulness through an evaluation experiment. Measuring force regardless of the shape of the object is difficult for conventional sensors because they are affected by the loading area and pressure distribution. Therefore, we developed a small and thin sensor whose contact surface is a single plate unaffected by the object shape. And this sensor has a structure that the capacitance distributions in the sensor are uniquely determined from the applied pressure distribution to calculate the force and its center position. Additionally, we developed its calibration method to correcting uncertain elements due to the nonlinear property. Through the evaluation experiment, we confirmed that the developed sensor can measure the force and its center position. In conclusion, we confirmed that the proposed method can realize a small and thin tactile force sensor capable of measuring force and its center position irrespective of the loading area and pressure distribution.