A Novel Six-Axis Force/Torque Sensor With Integrated Omnidirectional Overload Protection Mechanism

Abstract

Six-axis force/torque (F/T) sensors often encounter intense, unexpected external forces during robot interactions, which can easily lead to overload damage. Therefore, the sensors require omnidirectional mechanical overload protection devices to enhance their reliability. For the current issues in overload protection mechanisms, such as nonomnidirectional overload protection, difficulty in ensuring installation accuracy, and lack of physical verification, a novel six-axis F/T sensor based on cross beam structure with an integrated omnidirectional overload protection structure is proposed and developed. The simplified static model of its elastomer is optimized using the sequential quadratic programming (SQP) algorithm. The overload protection structure limits forces <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$F_{x}$</tex-math></inline-formula>, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$F_{y}$</tex-math></inline-formula>, and torque <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$M_{z}$</tex-math></inline-formula> using circular arc limits, while <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$F_{z}$</tex-math></inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$M_{x}$</tex-math></inline-formula> and, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$M_{y}$</tex-math></inline-formula> are restricted by rectangular limit structures. First, the feasibility of the sensor is validated through finite element method (FEM). Second, the static calibration experiment is completed and the calibration data are decoupled. The results indicate that the sensor’s linear accuracy can reach 1% and the coupling error is below 3%. Finally, the overload protection experiments verify that the sensor has at least ten times overload protection capacity. The proposed overload protection structure is applicable to various measurement systems.