Wearable Vibration Research Articles

Basic Analysis for Evaluation of Tennis Volley Skill Using Body Propagated Vibration Sensing

In sports that use tools, it is necessary to master tool manipulation with a high degree of accuracy because proficiency in tool manipulation leads to victory or defeat in a competition. The purpose of this study was to clarify the force transfer of the body, including the racket, from the perspective of vibration analysis to realize training to efficiently improve tennis skills. In this study, we measured the propagating vibration, surface electromyography of finger flexors and extensors, and racket movement under two conditions of strong- and weak-volleying in tennis and aimed to explain the meaning of the measured propagating vibration in terms of muscle control and racket kinematics. Based on the experimental results, it was confirmed that it is feasible to measure the change in stiffness from the racket to the wrist due to the muscle co-contraction owing to the propagating vibration signal intensity. These results indicate the possibility of evaluating tennis shot skill by analyzing the propagating vibrations measured using a wearable vibration measurement system.

Piezoelectric-electromagnetic collaborative energy extraction circuit for wearable vibration energy harvester

A piezoelectric-electromagnetic collaborative energy extraction circuit (PEC-EC) is presented in this paper to extract low-frequency vibration energy from arm swinging for wearable devices. This circuit simultaneously harvests energy from both the piezoelectric transducer (PZT) and electromagnetic coil generator (ECG). When the piezoelectric output voltage reaches its peak, the peak detection circuit becomes conductive, and the energy of the piezoelectric material is extracted at this moment. At the same time, the PEC-EC circuit can also harvest electromagnetic energy. Especially, even at low electromagnetic voltage input, the electromagnetic voltage can be extracted through the designed switch. The experimental results show that the circuit starts up only when the input voltage reaches 0.5V. The electromagnetic energy conversion efficiency can reach 53 %, and the piezoelectric energy conversion efficiency can reach 56 %. The effectiveness of collaborative extraction was also verified through experimental validation.

Development of an On-Shaft Vibration Sensing Module for Machine Wearable Rotor Imbalance Monitoring

Rotor imbalance is considered to be one of the main mechanical faults of rotating machinery; it may result in bearing damage and even catastrophic system failure. Recent progress in the Internet of Things (IoT) has promoted the application of novel sensing and computing techniques in the industry, and it is promising to employ novel IoT techniques for imbalance detection to avoid potential failures. Existing sensing techniques suffer from the impact of bearing structure dynamics, loss of accuracy during their lifetime, and security risks introduced by the sensor cabling and supports, which may, in turn, interfere with the machine operations due to inappropriate design and installation. This investigation provides an on-shaft machine wearable vibration sensing technique for effectively monitoring the running state of rotors while minimizing the interference with their operations. In this work, key investigations include the following: (1) theoretical modeling and an analysis of rotor imbalance, and its measurement with an on-shaft micro-electromechanical system (MEMS) accelerometer; (2) the development of a wirelessly powered, cordless on-shaft vibration measurement (OSVM) sensor for unobtrusive sensing of the vibration of rotating shafts; (3) the in-sensor computing design for optimizing the distribution of computing resources and decreasing data transmission. The tests and evaluation of the proposed techniques were conducted with a rotor test rig to demonstrate their feasibility. The presented investigation is a typical example of applying new sensing and computing paradigms to improve the flexibility and convenience of applications, which is a good reference for related investigations and practices.

Study on the combination of virtual machine tools and wearable vibration devices for operators experiencing cutting forces in the milling process

The primary goal of this study is to develop a wearable system for providing CNC machine operators with visual and tactile perception of triaxial cutting forces, thereby assisting operators in industrial environments to enhance work efficiency and prevent mechanical failures. To achieve this goal, we successfully integrated a virtual machining tool simulator with the remote-control wearable system (RCWS). Using the ‘King Path’ milling parameters, we employed the simulation software developed by the AIM-HI team to calculate static and dynamic cutting forces, converting this data into vibrational commands for the RCWS to generate corresponding tactile feedback. Furthermore, we conducted extensive experiments, testing various data conversion methods, including three sampling techniques and two data compression strategies, aiming to provide accurate tactile feedback related to cutting forces under different operating conditions.

Application of modulated vibration to restore driver alertness

Since driving while drowsy is a significant cause of vehicle accidents, road safety could be improved if more effective methods were available for improving driver alertness. The present paper investigated whether it is possible to improve alertness via a wearable device that applied somatosensory vibration to the driver's wrist. The vibration used modulation frequencies ranging from 12 Hz to 50 Hz and a carrier frequency of 250 Hz. Random on-and-off intervals and variable vibration amplitudes were used to minimise sensory adaptation. Fifteen participants undertook a sixty-minute simulated driving task that caused drowsiness. Karolinska Sleepiness Scale (KSS), Power Spectral Density (PSD) and Higuchi's Fractal Dimension (HFD) analyses of brainwave signals were used to identify variations in driver alertness. The vibration stimulus was found to significantly improve alertness when compared to a no-vibration condition. Participants experienced an immediate improvement in alertness that reached significance within 9 min and was then sustained at the level seen at the beginning of the experiment, indicating a full restoration of alertness. This result demonstrates that wearable vibration devices have the potential to improve alertness in drivers.

Effect of Wearable Vibration Therapy on Muscle Soreness, Joint Position Sense and Dynamic Balance

The aim of this study is to investigate the effects of wearable local vibration therapy (VT) on muscle soreness, joint position sense, and dynamic balance in recovery after squat exercise. Twenty males (age: 22.25±1.97 years) participated in the study. Muscle soreness, joint position sense, and dynamic balance were evaluated before exercise, 24 and 48 hours after exercise. All participants performed six sets of 10 repetitions of squat exercises. VT was applied to one thigh of the participants randomly for 10 minutes after exercise, and the other thigh was determined as the control. The muscle soreness increased significantly for VT (p.05). No significant difference was found between VT and control (p>0.05). No significant difference was found after exercise at knee joint position sense for both conditions (p>.05). No significant difference was observed between VT and control (p>.05). There was a significant difference between before exercise and 48 hours after exercise at anterior direction of the modified Star Excursion Balance Test for VT (p=.033). A significant difference was found between before exercise and 24 hours after exercise at posteromedial (p=.012) direction for VT. There was only significant difference at posteromedial (p=.028) direction at 24 hours after exercise between VT and control. The wearable local VT after squat exercise did not affect muscle soreness and knee joint position sense. However, local VT contributed to the improvement of dynamic balance.

Highly stable and ultra-fast vibration-responsive flexible iontronic sensors for accurate acoustic signal recognition.

Wearable verbal language servers function as sophisticated and effective tools for fostering intelligent interactions between humans and machines. In the realm of collecting acoustic vibration signals, flexible iontronic pressure sensors have demonstrated their efficacy by incorporating microstructures into the functional layer, resulting in heightened pressure sensitivity. However, the substantial viscosity of the integrated iontronic materials or the lack of bonding at the heterogeneous interface emerges as a significant hindrance to capacitance recovery, leading to sluggish response speeds and mechanical instability. Here, we address the issue by introducing hydrogen bonding between naturally microstructured protein micro-fibers and hydrophilic ionic hydrogel into the dielectric layer. Due to the good resilience of protein micro-fibers and the enahnced interfacial bonding, this flexible vibration sensor demonstrates outstanding performance characteristics, featuring exceptional signal stability, a high-pressure resolution of 522 pF kPa-1, an ultra-fast response time of 0.6 ms, and a relaxation time of 0.6 ms, with a limit of detection (LOD) of 0.12 Pa, making it well-suited for acoustic vibration acquisition. By using a one-dimensional convolutional neural network (1D-CNN) deep learning to process and recognize collected acoustic signals, our sensor achieved an impressive accuracy of 98.2%. These wearable vibration sensors exemplify promising versatile applications in biometric authentication, personalized services, and human-computer interaction.

Validation of Snaptics: A Modular Approach to Low-Cost Wearable Multi-Sensory Haptics.

Wearable haptic devices provide touch feedback to users for applications including virtual reality, prosthetics, and navigation. When these devices are designed for experimental validation in research settings, they are often highly specialized and customized to the specific application being studied. As such, it can be difficult to replicate device hardware due to the associated high costs of customized components and the complexity of their design and construction. In this work, we present Snaptics, a simple and modular platform designed for rapid prototyping of fully wearable multi-sensory haptic devices using 3D-printed modules and inexpensive off-the-shelf components accessible to the average hobbyist. We demonstrate the versatility of the modular system and the salience of haptic cues produced by wearables constructed with Snaptics modules in two human subject experiments. First, we report on the identification accuracy of multi-sensory haptic cues delivered by a Snaptics device. Second, we compare the effectiveness of the Snaptics Vibrotactile Bracelet to the Syntacts Bracelet, a high-fidelity wearable vibration feedback bracelet, in assisting participants with a virtual reality sorting task. Results indicate that participant performance was comparable in perceiving cue sets and in completing tasks when interacting with low-cost Snaptics devices as compared to a similar research-grade haptic wearables.

Efficacy of wearable vibration dressings on full-thickness wound healing in a hyperglycemic rat model.

Local low-frequency vibration promotes blood flow and wound healing in hard-to-heal diabetic foot ulcers (DFUs). However, vibration treatment is challenging in patients with DFUs due to wound management difficulties and low adherence. Consequently, developing wearable self-care devices becomes imperative for effective wound healing. This study introduces a wearable vibration dressing and assesses its impact on wound healing in hyperglycemic rats. Low-frequency vibration at 52 Hz was applied to the wound for 40 min/day in awake rats. Relative wound areas on post-wounding days (PWDs) 4-7 were significantly smaller and the wound closure rate was significantly higher in the vibration group than in the control group (p < 0.05, respectively). The total haemoglobin at baseline and after vibration on post-wounding day 7 was significantly larger in the vibration group than in the control group (p < 0.05). On PWD 7, the thickness of the granulation tissue was significantly higher in the vibration group than in the control group (p < 0.05). Moreover, the number of blood vessels at the wound site and vascular endothelial growth factor A protein expression were significantly higher in the vibration group than in the control group (p < 0.05, respectively). The ratio of (CD68+ /iNOS+ )/(CD163+ ) macrophages in the vibration group was significantly lower than that in the control group (p < 0.05). These results indicate the potential of wearable vibration dressings as new self-care devices that can promote angiogenesis and blood flow, improve inflammation, and enhance wound healing in DFUs.

Machine learning-assisted wearable triboelectric-electromagnetic vibration sensor for monitoring human rehabilitation training

Wearable vibration sensors for human motion monitoring are beneficial for doctors to observe the process of patient rehabilitation diagnosis and treatment in real-time. However, realizing smart sensing and self-powering of wearable devices is still challenging. Herein we developed a portable and reproducible triboelectric-electromagnetic vibration sensor (TE-VS) composed of a rolling-type triboelectric nanogenerator (R-TENG) and a slider-type electromagnetic generator (S-EMG), which aims to achieve highly sensitive detection and rapid identification of human motion. The ingenious mechanical design of the TE-VS enables the R-TENG component to adopt tangential contact friction and the S-EMG component to mutually move between magnets and coils in a non-contact way, which greatly improves the capture efficiency of weak motion, reduces material wear and increases the service life of the device. Multi-channel self-powered sensing signals fusion in a miniaturized space aims to enhance the algorithms detection accuracy of TE-VS. Importantly, the spring damping system improves the device's response speed to external vibrations and reduces the impact of shocks, which contributes to improving operation stability. The output responses of different frequency responses and different accelerations were characterized, which validated the potential of TE-VS in gesture recognition and limb disorder detection. Additionally, TE-VS was also demonstrated as a powerful vibration energy harvester to fully charge a μF-level commercial capacitor in a short time. The proposed TE-VS realizes battery-free operation, solves the long-term power supply problem of wearable devices, and facilitates the real-time monitoring application of human rehabilitation exercises. This is definitely a promising application for human rehabilitation medical devices.

Ultra-Low-Power Wearable Vibration Sensor with Highly Accurate Embedded Classifier.

Reducing the power consumption of wearable sensors is a very important issue in relation to the device usage time and form factor. However, continuous wireless communication to analyze the measured signal in real-time significantly increases the power consumption of the wearable sensor. In this study, we propose a wearable vibration sensor that operates with extremely low power through an embedded signal classifier, which exhibits high accuracy and low calculation load. We demonstrate cough detection through the proposed sensor system. The result exhibits an accuracy of 93.0%, which is 24.3% higher than the conventional embedded classification algorithm. Also, the proposed approach reduces the average power consumption of the wearable sensor by 8.8 times. Clinical Relevance-People can measure the vibration from the body using an ultra-low-power wearable sensor. It provides a solution to automatically monitor cough symptoms in numerous patients.

Применение параллельных вычислений для аннотирования сенсорных данных

Sensor data annotation involves automated marking of a time series of readings taken from the sensor, which highlights various activities specified by the specified series. Activity marking has a wide range of practical applications: predictive maintenance, intelligent management of life support systems, climate modeling, etc. Previously, we developed a parallel PSF algorithm for annotating sensor data using a GPU based on the concept of snippets. Snippet is a subsequence that many other subsequences of a given series resemble in the sense of a specialized similarity measure based on Euclidean distance. This article describes two case studies performed using the PSF algorithm: annotation of the readings of a wearable vibration accelerometer mounted on a person and a stationary vibration accelerometer mounted on a small crusher. As part of the research, computational experiments were conducted to evaluate the speed and accuracy of the developed algorithm. Also there was the research on the dependence of the efficiency of the algorithm on the values of the input parameters: the number of the desired snippets and the length of the subsequence.

User Participatory Design of a Wearable Focal Vibration Device for Home-Based Stroke Rehabilitation.

Stroke often leads to the significant impairment of upper limb function and is associated with a decreased quality of life. Despite study results from several interventions for muscle activation and motor coordination, wide-scale adoption remains largely elusive due to under-doses and low user compliance and participation. Recent studies have shown that focal vibration has a greater potential to increase and coordinate muscle recruitment and build muscle strength and endurance. This form of treatment could widely benefit stroke survivors and therapists. Thus, this study aimed to design and develop a novel wearable focal vibration device for upper limb rehabilitation in stroke survivors. A user participatory design approach was used for the design and development. Five stroke survivors, three physical therapists, and two occupational therapists were recruited and participated. This pilot study may help to develop a novel sustainable wearable system providing vibration-based muscle activation for upper limb function rehabilitation. It may allow users to apply the prescribed vibratory stimuli in-home and/or in community settings. It may also allow therapists to monitor treatment usage and user performance and adjust the treatment doses based on progression.

Evaluation of Skin Squeakiness Feeling with a Wearable Skin Vibration Sensor

Evaluation of Skin Squeakiness Feeling with a Wearable Skin Vibration Sensor

Transparent and Flexible Vibration Sensor Based on a Wheel-Shaped Hybrid Thin Membrane.

With the advent of human–machine interaction and the Internet of Things, wearable and flexible vibration sensors have been developed to detect human voices and surrounding vibrations transmitted to humans. However, previous wearable vibration sensors have limitations in the sensing performance, such as frequency response, linearity of sensitivity, and esthetics. In this study, a transparent and flexible vibration sensor was developed by incorporating organic/inorganic hybrid materials into ultrathin membranes. The sensor exhibited a linear and high sensitivity (20 mV/g) and a flat frequency response (80–3000 Hz), which are attributed to the wheel-shaped capacitive diaphragm structure fabricated by exploiting the high processability and low stiffness of the organic material SU-8 and the high conductivity of the inorganic material ITO. The sensor also has sufficient esthetics as a wearable device because of the high transparency of SU-8 and ITO. In addition, the temperature of the post-annealing process after ITO sputtering was optimized for the high transparency and conductivity. The fabricated sensor showed significant potential for use in transparent healthcare devices to monitor the vibrations transmitted from hand-held vibration tools and in a skin-attachable vocal sensor.

Vibration warning design for reaction time reduction under the environment of intelligent connected vehicles

Scenario-based warnings for road safety can be provided in the environment of intelligent connected vehicles via Bluetooth earphones or smart wristbands; designing an optimal means of presentation to drivers is an important point of consideration. Vibration warnings have been widely studied owing to their unique benefits. This experimental study aims to identify suitable body parts for vibration warnings during driving. The independent variables were the vibration position (three levels of stimulus, i.e., wrist, shin, and upper jaw) and response effector (two levels, i.e., hand and foot). Experiment Tasks 1 and 2 measured participants’ simple reaction time and choice reaction time, respectively, when providing vibration warnings in non-driving situations. The results demonstrate that the vibration on the upper jaw has the shortest simple reaction time and choice reaction time. The effect of stimulus-response consistency on choice reaction time was insignificant. Task 3 was similar to Task 2, with the exception of simulated driving. Compared to the result in Task 2, the choice reaction time in Task 3 was approximately 200 ms longer. Vibration of the upper jaw was reported to have the highest perceived intensity and preference. Based on the study results, the design implications for wearable vibration warnings of collision avoidance systems are presented

Vibrotactile Feedback System From the Fingertip to the Temples for Perceptual Enhancement of Contracture Palpation.

Contractures are generally assessed by a physician or physical therapist through palpation. However, contracture palpation requires skill and experience. The frictional vibration, which has a pulse-like vibration due to sliding disturbances around the affected area during palpation, is important in assessing the degree of contracture progression. This paper aims to enhance the perceptual sensitivity of frictional vibration for contracture palpation using a vibrotactile feedback system. We previously proposed an evaluation system for palpation with a wearable skin vibration sensor that detects skin-propagated vibration, allowing touch with a bare fingertip. In this paper, we propose the vibrotactile feedback system that presents the tactile information of the fingertip detected by the wearable tactile sensor to the temples with a vibrotactile display. A stimulator that gives vibrations similar to those during the palpation, which include pulse-like vibration and small vibration, was assembled. Then, psychophysical experiments on the vibrotactile feedback system were conducted using this stimulator. The results showed that the detection sensitivity of the pulse-like vibration was significantly enhanced with the feedback.

Wearable Vibration Sensor for Measuring the Wing Flapping of Insects.

In this study, we fabricated a novel wearable vibration sensor for insects and measured their wing flapping. An analysis of insect wing deformation in relation to changes in the environment plays an important role in understanding the underlying mechanism enabling insects to dynamically interact with their surrounding environment. It is common to use a high-speed camera to measure the wing flapping; however, it is difficult to analyze the feedback mechanism caused by the environmental changes caused by the flapping because this method applies an indirect measurement. Therefore, we propose the fabrication of a novel film sensor that is capable of measuring the changes in the wingbeat frequency of an insect. This novel sensor is composed of flat silver particles admixed with a silicone polymer, which changes the value of the resistor when a bending deformation occurs. As a result of attaching this sensor to the wings of a moth and a dragonfly and measuring the flapping of the wings, we were able to measure the frequency of the flapping with high accuracy. In addition, as a result of simultaneously measuring the relationship between the behavior of a moth during its search for an odor source and its wing flapping, it became clear that the frequency of the flapping changed depending on the frequency of the odor reception. From this result, a wearable film sensor for an insect that can measure the displacement of the body during a particular behavior was fabricated.

Body-Mounted Vibrotactile Stimuli: Simultaneous Display of Taps on the Fingertips and Forearm.

In this article, we present a body-mounted tactile display to deliver haptic feedback to the forearm and user-initiated haptic feedback to the fingertips. The display mounts two vibrotactile actuators on the forearm, leaving the user's hands free for manipulation tasks when the hands are not interacting with the tactile display, while also exploiting the tactile sensitivity of the fingertips when needed. We test the effectiveness of the display using paired vibrotactile taps sensed through the forearm and the fingertips, either separately or simultaneously. We measure the ability of participants to identify the vibrotactile taps. The results show that mounting the device on the forearm, so that the participant touches the forearm-mounted device with their fingertips receiving feedback to both locations simultaneously, decreases performance relative to mounting on the fingertips unless large amplitudes are used. We also test the accuracy with which participants identified different numbers of vibration taps (4, 8, 16, and 25 signals). The results show that as the number of signals changes, participant accuracy is not different when stimulating the fingertips alone compared to stimulating the fingertips and forearm together. We conclude with an example of a portable and wearable vibration display, and discuss future use cases of such a display.

Development of a wearable vibration device for preventing dozing driving

Development of a wearable vibration device for preventing dozing driving