A Novel Force Sensing Method Based on Stress Imaging Analysis

This paper presents a new approach to the design of multi-axial force sensing elements. We show that it is possible to measure multiple forces by detecting stress components-namely, normal stress, shear stress, and torque-with a single sensing element. Multi-axis force-torque sensors have become popular in the field of robotics, because they provide valuable information to robots during physical interaction; but these sensors have posed a challenge to researchers during fabrication, as they typically require multiple uni-axial sensing elements scattered over the mechanical structure of the force-torque sensor. We solve this problem by accomplishing the same functionality with just one sensing element. Our sensing element is composed of layers of elastomer, with conductive electrodes integrated within the two sensitive layers. When a force is applied, some (or all) of the electrodes within each layer are compressed, changing the capacitance and providing stress images. A stress-imaging analysis, thus, allows us to reliably infer the applied force. In this paper, we describe the design, fabrication, and characterization of our triaxial sensing element. After constructing the prototype, we validate its performance using a series of experiments. The results demonstrate that our stress-imaging analysis method does indeed allow the measurement of multiple force components with a single sensing element.