Design and analysis of a Stewart-platform-based six-axis load cell

Abstract

In this work, a six-axis load cell based on the geometry of a Stewart platform was developed. Its geometry and functional requirements were motivated by the needs of robotic limbs designed to be attached to human workers to support them in typically unergonomic positions. The sensor can measure forces and torques in six degrees of freedom, and can stably support the worker in various hanging positions while still being sensitive to load measurements in different directions. Furthermore, it is made from inexpensive, commonly available cantilever beam load cells. In the least accurate direction, Mx, our measurements were consistently 20% below the nominal applied load. In the most accurate directions, Fx, My, and Mz, our measurements were consistently within 5% of the nominal applied loads. Performance can be optimized using the condition number of the transformation matrix. The full-scale version of the hex sensor is also designed and optimized based on its condition number.