External Force Estimation of Pneumatic Soft Actuator with Built-in Displacement Sensor

We have proposed an extension-type pneumatic soft actuator made of a silicone tube covered by a metal spring. The spring is used to reinforce the outer periphery and to estimate the extension of the actuator from its change in inductance. However, the repeatability of the measurement needs to be improved since neither side of the spring is firmly fixed to the silicone tube. In this study, we newly designed and developed a soft actuator to improve the repeatability of the measurement. Then, we estimated the external force applied to the actuator using the supply pressure and the estimated displacement of the spring. In our experiments, we used an external force sensor, and its measured value was compared with the estimated force value. We confirmed the effectiveness of the force estimation by performing experiments with a low-frequency sinusoidal input of 0.1 Hz.