A Novel Geometric Design Method of Elastic Structure for 6-Axis Force/Torque Sensor

We present a novel design method of a 6-axis Force/Torque (F/T) sensor with identical stiffness in all directions. In contrast to common F/T sensor designs, the proposed method is an analytical approach to the realization of a desired diagonal stiffness matrix which implies the complete decoupling of the stiffnesses in all directions. The first step of the design is to group the column vectors of a given rank 6 diagonal stiffness matrix into in-plane type and out-of-plane type stiffnesses. Each type of stiffnesses is then synthesized by means of three line vectors and designed as the corresponding serial-chain for a limb of an F/T sensor using only circular hinges. The F/T sensor can be formed by connecting the designed two serial-chains in series. However, for a practical design with minimum structural error and better strength, each of two type stiffnesses is further divided into a set of n separate serial-chains. Finally, the n-sets of serial-chains each consisting of six circular hinges that correspond in-plane and out-of-plane type stiffnesses are connected to the moving platform in parallel to complete the design. The FEM analysis and experiments are conducted to verify the proposed design method.