Air-Chamber-Based Soft Six-Axis Force/Torque Sensor for Human-Robot Interaction

Soft multiaxis force/torque sensors provide safe and precise force interaction. Capturing the complete degree-of-freedom of force is imperative for accurate force measurement with six-axis force/torque (6-F/T) sensors. However, cross-axis coupling can lead to calibration issues and decreased accuracy. In this instance, developing a soft and accurate six-axis sensor is a challenging task. In this article, a soft air-chamber type 6-F/T sensor with 16-channel barometers is introduced, which is housed in hyper-elastic air chambers made of silicone rubber. Additionally, an effective decoupling method is proposed, based on a rigid-soft hierarchical structure, which reduces the six-axis decoupling problem to two three-axis decoupling problems. Finite element model simulation and experiments demonstrate the compatibility of the proposed approach with reality. The prototype's sensing performance is quantitatively measured in terms of static load response, dynamic load response, and dynamic response characteristics. It possesses a measuring range of 50 N force and 1 Nm torque, and the average deviation, repeatability, nonlinearity, and hysteresis are 4.9%, 2.7%, 5.8%, and 6.7%, respectively. The results indicate that the prototype exhibits satisfactory sensing performance while maintaining its softness due to the presence of soft air chambers.