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

Abstract

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.

Soft Inductive Tactile Sensor Using Flow-Channel Enclosing Liquid Metal

“…Magnetic tactile sensors, which consist of a magnet embedded in a soft material and a magnetic sensor placed outside the soft material, measure the applied force based on the change in magnetic field [17]- [19]. As another type of tactile sensor employing an electromagnetic phenomenon, inductive tactile sensors, which measure the change in electromagnetic field around sensor bodies with coils, have been proposed [10], [11], [20]- [24]. In this structure, some metallic ingredients, such as iron particles [10], [20], [21], [24] and liquid metal [11], are locally placed in a soft material, and a coil circuit is mounted around these ingredients outside the soft material.…”

“…As another type of tactile sensor employing an electromagnetic phenomenon, inductive tactile sensors, which measure the change in electromagnetic field around sensor bodies with coils, have been proposed [10], [11], [20]- [24]. In this structure, some metallic ingredients, such as iron particles [10], [20], [21], [24] and liquid metal [11], are locally placed in a soft material, and a coil circuit is mounted around these ingredients outside the soft material. Upon applying a contact force to the soft material, the iron particles or liquid metal displaces in the material, following which the positional relationship between the coil and them changes.…”

Development of Fully Shielded Soft Inductive Tactile Sensors

“…However, the complex fabrication of micro-channels makes it not ideal to be used as "shielding box" for the FS-SITS. Another solution is to use magnetorheological elastomers (MRE) as soft sensing target [25,26], but MRE cannot provide the shielding effect.…”

“…4a). The experimental setup used to characterize and evaluate the FS-SITS in this paper is similar to [25]. A LabVIEW program is developed to acquire data from the FS-SITS and a commercial force/torque sensor (Nano17-E, ATI, USA), and to control the motorized micropositioning stages (M-111.1DG, Physik Instrumente, Germany).…”

Inexpensive monolithic additive manufacturing of silicone structures for bio-inspired soft robotic systems

“…In the present paper, an inexpensive ($250) custom-made MEX-based silicone 3D printer has been used in conjunction with a custom-made cartesian pick and place robot (CPPR) to create bio-inspired silicone structures with embedded shape memory alloy (SMA) actuators. The novelty of the present study is the one-shot fabrication of extremely soft structures as shown in figure 1 (elastic modulus 0.045 MPa [14]) that are immediately usable following 3D printing. When actuators of soft structures are activated, animal-like behavior and out-of-plane motions have been achieved.…”