A Flexible Concept for Designing Multiaxis Force/Torque Sensors Using Force Closure Theorem

Multiaxis force/torque sensors have many applications in the areas of robotics and automation. A building blocks concept to design multiaxis force/torque sensors is introduced to provide a flexible and low-cost solution to measure multidimensional force/torque signals using a modularized assembly of several off-the-shelf 1-D force sensors. Based on the force closure theorem, we first identify the relationship between the required number of the 1-D force sensors and the dimensions of the measured force/torque signal. Furthermore, we formulate alternatives of the design solution for a multiaxis force/torque sensor, including the location and direction of each 1-D sensor. A virtual prototype of a six-axis force/torque is developed using this concept. Matrix-based force measuring models are derived to compute the six-axis force/torque signals from the output signals of seven 1-D force sensors. The matrix-based force measuring equations are validated using automatic dynamic analysis of mechanical systems. The output signals of the six-axis force/torque signal is consistent with the reference signals measured by an ATI Nano-17 force/torque sensor. One major advantage of this design concept is its flexibility; we can easily adapt the mechanical structure to design multidimensional force/torque sensors ranging from two degrees of freedom (2-DOFs) to 6-DOFs.