A Wireless Inductive Sensing Technology for Soft Pneumatic Actuators Using Magnetorheological Elastomers

This paper presents a novel wireless inductive sensing technology to measure body deformation of soft pneumatic actuators (SPAs). The proposed technology exploits a magnetorheological elastomer (MRE) both as actuator's highly deformable skin and as target of the inductive sensor. When the MRE skin is deformed by internal driving and/or external load., the distance between the MRE and sensing coil changes., thereby the inductance. A flat SPA with an MRE skin is developed as a case study to validate and evaluate the proposed technology. A multiphysics finite element model is built to simulate the characteristics of the soft actuator and sensor as a single system. Experimental results highlight that this inductive sensing technology can measure the skin deformation with an effective resolution as high as 3 μm (RMS) at null deformation (50 μm at maximum deformation), without any hysteresis. Moreover., with pressure information, it is possible to retrieve both the deformation caused by internal driving and external load. A typical pneumatic bending actuator was developed to demonstrate its easy implementation in soft actuators. The presented technology does not require wires or mechanical connections between electronics and the deformable body, providing a promising sensing solution for SPAs and other soft systems.