Design and fabrication of a soft three-axis force sensor based on radially symmetric pneumatic chambers

In applications of human-robot interactions, accurate measurement of interactive forces between the human and the robot plays a significant role. Such sensors should not only be accurate and reliable, but also be soft enough to guarantee the safe and compliant human-robot interaction. In this aspect, pneumatic sensors with soft air chambers have often been utilized as a soft force measurement system. Although such a sensor system provides a good compliance and softness, however, it measures only a lumped force acting on the chamber, because the measurement of the pneumatic sensor is the pressure change in the air chamber. For the measurement of multi-dimensional interaction forces with high softness and compliance, a three-axis force measurement system is devised by arranging three air chambers in a radially symmetric pattern. Each air chamber embeds a pneumatic sensor, and the pressure changes in the three air chambers are measured in order to distinguish the direction of the applied force. By decoupling the sensor signals from the three pneumatic sensors, the three-dimensional force components can be calculated accurately. Consequently, the proposed sensor system is able to measure the three-axis forces while maintaining the great softness and compliance provided by the soft air chambers. The design, the fabrication method, and the verification of the proposed method are introduced in this paper.