A Novel Elastic Structure for Three-Axis Force/Torque Sensor: Kinematic Design and Feasibility Study

In this paper, we present a new elastic structure for a three-axis force/torque (F/T) sensor to enhance the compliant characteristics of an F/T sensor. Compliant sensor structure is desirable for safe human-robot interaction when the F/T sensor is used to measure the interaction force. The proposed structure is composed of a serial connection of three flexure hinges. While elastic structures of most F/T sensors are determined by experience and experiments, the proposed sensor structure is determined by analyzing the geometric structure of the desired compliance matrix. Observing the geometric characteristics of the desired compliance matrix reveals a unique form of the spring model, which consists of three serially connected torsional springs whose axes lie on the same plane. From this spring model, a new concept of a serial-based sensor structure is designed to sense the magnitude and point of action of an applied force. Feasibility of the proposed concept as an F/T sensor structure is confirmed by a finite-element analysis and experiments with a sensor test bed.