A novel magnetostrictive curvature sensor employing flexible, figure-of-eight sensing coils

The demand for accurate angle measurements in a form that is robust and small is high, due to the advances in virtual reality applications, primarily the virtual reality headsets. The peripheral devices are required to completely immerse the user in a virtual reality setting, and for this purpose, a robust sensor has been developed. The angle measurements can also be used in motion sensing applications for medical purposes, allowing monitoring of a patient’s condition. This paper presents the development of a planar figure-of-eight coil sensor, which has been designed for the purpose of curvature sensing. The copper-plated polyimide material, FR4 FLEX, was used for the fabrication of the planar figure-of-eight coil. A curvature sensor was designed and consists of the figure-of-eight coil along with the magnetostrictive material Metglas 2605SA1. The sensor was incorporated in an oscillator circuit, where curvature-induced stress within the material changes the amplitude and the frequency of the output signal of the circuit

Developable Rotationally Symmetric Kirigami‐Based Structures as Sensor Platforms

Developable surfaces based on closed‐shape, planar, rotationally symmetric kirigami (RSK) sheets approximate 3D, globally curved surfaces upon (reversible) out‐of‐plane deflection. The distribution of stress and strain across the structure is characterized experimentally and by finite‐element analysis as a function of the material and cut parameters, enabling the integration with strain gauges to produce a wearable, conformal patch that can capture complex, multiaxis motion. Using the patch, real‐time tracking of shoulder joint and muscle behavior is demonstrated. The facile fabrication and unique properties of the RSK structures potentially enable wearable, textile‐integrated joint monitoring for athletic training, wellness, rehabilitation, feedback control for augmented mobility, motion of soft and traditional robotics, and other applications.This work introduces a new paradigm for realizing 2D to curved, 3D, functional surface transformation using rotationally symmetric kirigami as a platform for deploying wearable sensors; here it is demonstrated for real‐time tracking of complex motion of joints within the body and circumventing longstanding tradeoffs in the design of materials, structures, and devices for conformable, wearable electronics.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153082/1/admt201900563-sup-0001-SuppMat.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153082/2/admt201900563.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153082/3/admt201900563_am.pd

Actuating movement in refined wearables

Nowadays it is quite possible to deploy textiles as sensors and avoid traditional hard sensors. Actuation (movement) turns out more difficult. It is advantageous to combine sensing and actuation, similar to ecological perception theory. Although several actuators are known: SMA, voice coil, motors, they all have significant disadvantages. Materials: we explored new ways of using electric motors in feedback loops together with textile sensors (modified servos). Approach: together with Industrial Design (Eindhoven University of Technology, TU/e) and Fashion (Utrecht School of Arts, HKU) students we followed a hands-on approach to come to inspired innovative fashion: garments capable of mechanical change, showing dynamic forms or adapting to the person wearing it. Findings: we obtained six very different concepts, themes ranging from defence, attraction, using daylight, playfulness to breathing and dancing. The noise of the mechanism can strengthen the intended semantics – sometimes it is a problem. The conductive yarn sensors are useful, yet introduce calibration challenges. We have short video-clips of the results which we shall show during our presentation. Implications and relevance: our examples show the potential of actuation as a new semantic language, which will become even more important when new technologies will help us overcome the present-day actuator limitations. Conclusions and recommendations: our students enjoy this way of learning about electronics, programming and video making immensely while also learning about fashion and aesthetics. A new dynamic language is waiting to be discovered. We will share our findings and future propositions for activated fashion

Soft actuation and sensing towards robot-assisted facial rehabilitation

Continuing research efforts in robot-assisted rehabilitation demand more adaptable and inherently soft wearable devices. A wearable rehabilitative device is required to follow the motion of the body and to provide assistive or corrective motions to restore natural movements. Providing the required level of fluidity in wearable devices becomes a challenge for rehabilitation of more sensitive and fragile body parts, such as the face. To address this challenge, we propose a soft actuation method based on a tendon-driven robotic origami (robogami) and a soft sensing method based on a strain gauge with customized stretchable mesh design. The proposed actuation and sensing methods are compatible with the requirements in a facial rehabilitative device. The conformity of robogamis originates from their multiple and redundant degrees of freedom and the controllability of the joint stiffness, which is provided by adjusting the elasticity modulus of an embedded shape memory polymer (SMP) layer. The reconfiguration of the robogami and the trajectory and directional compliance of its end-effector are controlled by modulating the temperatures, hence the stiffness, of the SMP layers. Here we demonstrate this correlation using simulation and experimental results. In this paper, we introduce a thin and highly compliant sensing method for measuring facial movements with a minimal effect on the natural motions. The measurements of the sensors on the healthy side can be used to calculate the required tendon displacement for replicating the natural motion on the paralyzed side of the face in patients suffering from facial palsy

Modeling and Analysis of a High-Displacement Pneumatic Artificial Muscle With Integrated Sensing

We present a high-displacement pneumatic artificial muscle made of textiles or plastics that can include integrated electronics to sense its pressure and displacement. Compared to traditional pneumatic muscle actuators such as the McKibben actuator and other more recent soft actuators, the actuator described in this paper can produce a much higher (40~65%) contraction ratio. In this paper, we describe the design, fabrication, and evaluation of the actuator, as well as the manufacturing process used to create it. We demonstrate the actuator design with several examples that produce 120 and 300 N at pressures of 35 and 105 kPa, respectively, and have contraction ratios of 40–65%

Design and control of a bio-inspired soft wearable robotic device for ankle-foot rehabilitation

Abstract We describe the design and control of a wearable robotic device powered by pneumatic artificial muscle actuators for use in ankle-foot rehabilitation. The design is inspired by the biological musculoskeletal system of the human foot and lower leg, mimicking the morphology and the functionality of the biological muscle-tendon-ligament structure. A key feature of the device is its soft structure that provides active assistance without restricting natural degrees of freedom at the ankle joint. Four pneumatic artificial muscles assist dorsiflexion and plantarflexion as well as inversion and eversion. The prototype is also equipped with various embedded sensors for gait pattern analysis. For the subject tested, the prototype is capable of generating an ankle range of motion of 27 • (14 • dorsiflexion and 13 • plantarflexion). The controllability of the system is experimentally demonstrated using a linear time-invariant (LTI) controller. The controller is found using an identified LTI model of the system, resulting from the interaction of the soft orthotic device with a human leg, and model-based classical control design techniques. The suitability of the proposed control strategy is demonstrated with several angle-reference following experiments

Force Sensors Constructed from Ferromagnetic Particles Embedded Within Soft Materials

The inclusion of magnetic particles as fillers within soft materials has the potential to drive the development of smart materials with high functionality and structural diversity. Six ferromagnetic fillers (i.e., nickel, carbonyl iron, cobalt, iron oxide, magnetite, and neodymium powder) were incorporated within polydimethylsiloxane at concentrations of 0.01 wt %, 0.1 wt %, and 1 wt %. Defined compression tests determined the ability to detect material deformation and the magnetic field response generated during compression cycles. Utilizing iron oxide at 1 wt %, the compressive response of additional silicones and a two-part polyurethane was also investigated. Compression testing of five of the six ferromagnetic fillers in PDMS, with the exception of carbonyl iron, revealed that 1 wt % was the minimum concentration required to detect compression events via the magnetic field response. The findings of carbonyl iron at 1 wt % were not viable as its magnetic field response was similar to that of the PDMS control samples. The neodymium filler particles produced the strongest magnetic field response. However, settling of the neodymium particles became evident during the curing process, which prompted further theoretical exploration at various particle sizes and viscosities. Our findings suggested that smaller neodymium particle sizes should be explored in future analyses. PDMS displayed the optimal relationship between force and displacement amongst the various polymers with 1 wt % iron oxide. The other materials were either too soft or were too resistive to be considered viable as a durable soft sensor material or were limited by an inability to measure magnetic field strength

Soft Wearable Motion Sensing Suit for Lower Limb Biomechanics Measurements*

Abstract — Motion sensing has played an important role in the study of human biomechanics as well as the entertainment industry. Although existing technologies, such as optical or inertial based motion capture systems, have relatively high accuracy in detecting body motions, they still have inherent limitations with regards to mobility and wearability. In this paper, we present a soft motion sensing suit for measuring lower extremity joint motion. The sensing suit prototype includes a pair of elastic tights and three hyperelastic strain sensors. The strain sensors are made of silicone elastomer with embedded microchannels filled with conductive liquid. To form a sensing suit, these sensors are attached at the hip, knee, and ankle areas to measure the joint angles in the sagittal plane. The prototype motion sensing suit has significant potential as an autonomous system that can be worn by individuals during many activities outside the laboratory, from running to rock climbing. In this study we characterize the hyperelastic sensors in isolation to determine their mechanical and electrical responses to strain, and then demonstrate the sensing capability of the integrated suit in comparison with a ground truth optical motion capture system. Using simple calibration techniques, we can accurately track joint angles and gait phase. Our efforts result in a calculated trade off: with a maximum error less than 8%, the sensing suit does not track joints as accurately as optical motion capture, but its wearability means that it is not constrained to use only in a lab. I