Ultrastretchable Segmented Sensors for Functional Human-Machine Interfaces.

The key feature that enables soft sensors to shorten the performance gap between robots and biological structures is their deformability, coupled with their capability to measure physical changes. Robots equipped with these sensors can interact safely and proprioceptively with their environments. This has sparked interest in developing novel sensors with high stretchability for application in human-robot interactions. This study presents a novel ultrasoft optoelectronic segmented sensor design capable of measuring strains exceeding 500%. The sensor features an ultrastretchable segment physically joined with an asymmetrically configured soft proprioceptive segment. This configuration enables it to measure high strain and to detect both the magnitude and direction of bending. Although the sensor cannot decouple these types of deformations, it can sense prescribed motions that combine stretching and bending. The proposed sensor was applied to a highly deformable scissor mechanism and a human-robot interface (HRI) device for a robotic arm, capable of quantifying parameters in complex interactions. The results from the experiments also demonstrate the potential of the proposed segmented sensor concept when used in tandem with machine learning, affording new dimensions of proprioception to robots during multilayered interactions with humans.

Thermo-Pneumatic Artificial Muscle: Air-Based Thermo-Pneumatic Artificial Muscles for Pumpless Pneumatic Actuation.

To make robots more human-like and safer to use around humans, artificial muscles exhibiting compliance have gained significant attention from researchers. However, despite having excellent performance, pneumatic artificial muscles (PAMs) have failed to gain significant traction in commercial mobile applications due to their requirement to be tethered to a pneumatic source. This study presents a thermo-PAM called Thermo-PAM that relies on heating of a volume of air to produce a deformation. This allows for pneumatic actuation using only an electrical power source and thus enables pumpless pneumatic actuation. The actuator uses a high ratio between the heating volume and the deformable volume to produce a high actuation force throughout its entire motion and can produce either contractile or extension motions. The controllability of the actuator was demonstrated as well as its ability to handle heavy payloads. Moreover, it is possible to rely on either positive or negative pressure actuation modes where the positive pressure actuation mode actuates when heated and the negative pressure actuation mode relaxes when heated. The ability to use Thermo-PAMs for different modes of actuation with different operation methods makes the proposed actuator highly versatile and demonstrates its potential for advanced pumpless robotic applications.

Design of a Novel Sensing Method for a Pneumatic Artificial Muscle Actuator-Driven 2-Degrees of Freedom Parallel Joint.

The development of soft actuators and robots has spurred interest in human-friendly robots and devices that can operate in proximity with living things. Researchers have used soft actuators to drive hybrid soft/rigid mechanical platforms with multiple degrees of freedom (DOFs) that are both compliant and produce precise motions. However, the addition of sensors on these systems for feedback control remains a critical issue as they require multiple sensors operating simultaneously while the system undergoes complex motions. This article introduces the use of two spring-tensioned tendons passing through angular encoders for yaw and pitch orientation measurement into a pneumatic artificial muscle-driven two DOFs platform. This system possesses several advantages such as having a large range of motion and enables feedback control of the joint for position control. The joint is shown to be able to follow diverse motion patterns and capable of operating through external disturbances and was implemented as the base joint of an inflatable member.

Low-Powered and Resilient IR-Based Pigmented Soft Optoelectronic Sensors.

Soft optoelectronic sensors capable of multimodal sensing have high repeatability, which makes them an attractive choice for applications requiring deformable sensors. A weakness of these sensors is the constant supply of electrical power input required to pass the light signal through their core, which can lead to excessive power requirements for portable devices. Using an infrared (IR) spectrum signal that requires very low power for signal propagation should help alleviate this issue. However, soft optoelectronic sensors can be easily disturbed by external light sources or even suffer from cross-interference, and IR-based sensors are more susceptible to such interferences since IR wavelengths can penetrate the cladding material generally used in soft optical waveguides. This paper presents a highly stretchable low-powered IR-based soft optoelectronic stretchable sensor with pigmented cladding capable of multimodal sensing. The use of an IR-spectrum signal makes it consume a fraction of the power of what a visible spectrum-based optoelectronic sensor would consume. Pigmented elastomers are used as the cladding of the waveguides of these sensors, which makes them highly resilient. These sensors are embedded in a resilient soft robotic gripper capable of controlling its contact force even with significant external disturbances.

Fabric Vest Socket with Embroidered Electrodes for Control of Myoelectric Prosthesis.

Myoelectric prostheses assist users to live their daily lives. However, the majority of users are primarily confined to forearm amputees because the surface electromyography (sEMG) that understands the motion intents should be acquired from a residual limb for control of the myoelectric prosthesis. This study proposes a novel fabric vest socket that includes embroidered electrodes suitable for a high-level upper amputee, especially for shoulder disarticulation. The fabric vest socket consists of rigid support and a fabric vest with embroidered electrodes. Several experiments were conducted to verify the practicality of the developed vest socket with embroidered electrodes. The sEMG signals were measured using commercial Ag/AgCl electrodes for a comparison to verify the performance of the embroidered electrodes in terms of signal amplitudes, the skin-electrode impedance, and signal-to-noise ratio (SNR). These results showed that the embroidered electrodes were as effective as the commercial electrodes. Then, posture classification was carried out by able-bodied subjects for the usability of the developed vest socket. The average classification accuracy for each subject reached 97.92%, and for all the subjects it was 93.2%. In other words, the fabric vest socket with the embroidered electrodes could measure sEMG signals with high accuracy. Therefore, it is expected that it can be readily worn by high-level amputees to control their myoelectric prostheses, as well as it is cost effective for fabrication as compared with the traditional socket.