A 3-D Force Sensor Based on Combination of Magnetic and Piezoresistive Transduction

Tactile sensors have been playing a crucial role in the operation of robot hands, especially in the analysis of grasping stability. However, the current three–dimensional (3-D) force sensors generally adopt the single sensing transduction(such as the capacitive 3-D force sensor only includes capacitance as a sensing transduction) and output the coupled signals, lacking accurate force decoupling. Here, we present a 3-D force sensor with self-decoupling by combining magnetic and piezoresistive transduction. Based on the characteristics of axially magnetized circular magnet, we explain the sensing principle of shear force which is using four Hall elements mounted with the cross-type to measure the shear force by detecting the sliding distance and direction of the magnet (can only move horizontally), and utilize a piezoresistive element to measure the normal force. In addition, we use a neural network to model the sensor response to improve the detection accuracy of shear force. The sensor resolutions for normal force and shear force are 0.3N and 0.2N, respectively, and the measurement ranges are more than 20N and 6N, respectively. By mounting our sensor at the gripper, we further show the performance of sensor for detecting 3-D force in the process of grasping object. The proposed 3-D force sensor could be beneficial for the adaptive grasping of robot hands.