An optical sensor for tracking hand articulations

Recognizing and tracking articulations of the human hand is key to the development of areas such as robotics, virtual reality systems and physical rehabilitation. Based on the principle of crossed-polarization detection, a novel optical sensor with a hinge configuration, is proposed to monitor finger articulation. Using 3D printing technology, we fabricated a lightweight and compact sensor suited to attaching on fingers. The weighted average method was applied to the sensor's output data to determine angular positions corresponding to finger joint articulations. The experimental results show excellent consistency with theoretical predictions. The sensor features good accuracy (±0.5% of full scale) and repeatability, improved sensitivity, and an improved measuring range of 180°. The performance of the sensor is a promising development for monitoring finger articulation. Future work will focus on integrating multiple sensors as part of an instrumented glove to evaluate the true potential for monitoring hand articulation

Learning from Long-Tailed Noisy Data with Sample Selection and Balanced Loss

The success of deep learning depends on large-scale and well-curated training data, while data in real-world applications are commonly long-tailed and noisy. Many methods have been proposed to deal with long-tailed data or noisy data, while a few methods are developed to tackle long-tailed noisy data. To solve this, we propose a robust method for learning from long-tailed noisy data with sample selection and balanced loss. Specifically, we separate the noisy training data into clean labeled set and unlabeled set with sample selection, and train the deep neural network in a semi-supervised manner with a novel balanced loss based on model bias. Experiments on benchmarks demonstrate that our method outperforms existing state-of-the-art methods

A Two-Axis Goniometric Sensor for Tracking Finger Motion

The study of finger kinematics has developed into an important research area. Various hand tracking systems are currently available; however, they all have limited functionality. Generally, the most commonly adopted sensors are limited to measurements with one degree of freedom, i.e., flexion/extension of fingers. More advanced measurements including finger abduction, adduction, and circumduction are much more difficult to achieve. To overcome these limitations, we propose a two-axis 3D printed optical sensor with a compact configuration for tracking finger motion. Based on Malus’ law, this sensor detects the angular changes by analyzing the attenuation of light transmitted through polarizing film. The sensor consists of two orthogonal axes each containing two pathways. The two readings from each axis are fused using a weighted average approach, enabling a measurement range up to 180 ∘ and an improvement in sensitivity. The sensor demonstrates high accuracy (±0.3 ∘ ), high repeatability, and low hysteresis error. Attaching the sensor to the index finger’s metacarpophalangeal joint, real-time movements consisting of flexion/extension, abduction/adduction and circumduction have been successfully recorded. The proposed two-axis sensor has demonstrated its capability for measuring finger movements with two degrees of freedom and can be potentially used to monitor other types of body motion

Compatibility-tuned distribution of nanoparticles in co-continuous rubber structures toward microwave absorption enhancement

Development of novel and versatile approaches to engineer composites with light density, broad effective bandwidth and high microwave absorption (MA) capacity is of great importance. Here, co-continuous natural rubber/epoxidized natural rubber (NR/ENR) blends with a selective distribution of conductive carbon black nanoparticles (CCBs), have been fabricated by tow-roll mixing. ENR with abundant epoxide groups shows inferior wettability to CCB than NR, which is responsible for the preferential location of CCB in the NR/ENR blend. Increasing the epoxidation level of ENR promotes the preferential location of CCB and creates stronger dielectric loss, thus enhancing the MA properties of CCB/NR/ENR composites. When the epoxidation level increases to 40 mol%, the MA capacity of the composite has been significantly enhanced by 40%. Meanwhile, the qualified frequency bandwidth (RL < −10 dB) of composites with ENR is 85% broader than that of CCB/NR composites. Such a novel approach of compatibility-tuned nanoparticles distribution in co-continuous rubber blends will significantly promote the multi-functional use of rubber and carbonaceous resources

The development of an electro-optical goniometric sensor for tracking articulated hand motion

The study of hand kinematics has developed into an important research area. Several techniques have been proposed for recording hand movements, however the majority suffer from poor accuracy and limited functionality. To overcome these limitations, this research aims to develop a novel goniometric sensor for tracking articulated hand motion. This research is the first attempt to use Malus’ law as a sensing principle for monitoring human hand kinematics. Three distinct electro-optical sensors (sensor#1, sensor#2, and sensor#3) with compact configurations are developed. They are coupled with the rotation of the finger joints and detect angular motion by analysing the attenuation of light transmitted through linear polarising films. The three goniometric sensors are designed with different measurement capabilities to suit different types of finger articulation. Sensor#1 has a single rotation axis and a measuring range of 0◦ to 90◦, which can be used for the distal interphalangeal joints. Sensor#2 can measure the movements spanning 180◦ with an improved sensitivity in a single plane; this is ideal for the proximal interphalangeal joints. Sensor#3 consists of two measurement axes, each having a measurement range up to 180◦. These properties make sensor#3 suitable for monitoring the finger joints with two degrees of freedom (DOFs), e.g. the metacarpophalangeal joints; this is unique in designing a single sensor for monitoring the two-DOF finger joints. In comparison with a commonly used commercial bend sensor, the electro-optical sensors demonstrate higher measurement accuracy (mean absolute error: ≤0.28◦) and faster response time under laboratory conditions. Furthermore, the developed sensors all successfully tracked the dynamic finger motion when attached to human finger joints. This work verifies that the developed electro-optical sensors offer a viable sensing technique for tracking articulated human motion directly with high measurement accuracy

A proposed optical-based sensor for assessment of hand movement

The purpose of this research is to evaluate two types of sensor that can be applied to monitor human finger flexion in real time. Currently, flex sensors are the most commonly used resistance sensors in glove-based systems. However, measurements show that current flex sensors have problems associated with hysteresis error, low sensitivity at small angles, and considerable time drift with large bending angles which render them unsuitable for tracking hand motion at low speed. In contrast, the developed optical sensor prototype has good repeatability, sensitivity and low temporal drift, as well as offering the capability of accurate measurements in both clockwise and anticlockwise directions. The sensor is based on the principle of crossed-polarization detection, and consists of one LED, two rotatable polarizers and one photodiode amplifier which enables the detection of changes in polarized light intensity proportional to angular rotation

Numerical Analysis on the Mechanical Properties of the Concrete Precast Pavement of Runways under the Wheel Load

This study aims to investigate the mechanical characteristics of precast concrete runway cement pavement under the wheel load of aircraft, and to promote the construction of precast concrete pavement. In this study, based on the elastic layered Boussinesq calculation theory and ABAQUS finite element numerical model, the distribution law of stress, the displacement of the aircraft wheel load acting on different positions of the pavement slab, the influence of the added dowel bar on the pavement slab, and the load transfer between adjacent slabs are obtained. The results revealed that when the wheel load of the aircraft acts on the edge and joint of the slab, the vertical stress of the adjacent slab edge is largest, followed by the middle of the slab, and then the joint; the maximum vertical stress is 0.295 MPa. Furthermore, the aircraft wheel load on the slab edge, and the joint vertical displacement, is larger than that of the slab middle, and the adjacent slab edge transverse displacement attenuation coefficient is approximate. Moreover, the load transfer efficiency of the dowel bar was lower when the wheel load of the aircraft was closer to another unloaded slab. Finally, the validity and sensitivity of the simulation results are verified by laboratory test data. These results can provide a reference and suggestions for the design and production of the precast concrete pavement of airport runways

Numerical Analysis on the Mechanical Properties of the Concrete Precast Pavement of Runways under the Wheel Load

This study aims to investigate the mechanical characteristics of precast concrete runway cement pavement under the wheel load of aircraft, and to promote the construction of precast concrete pavement. In this study, based on the elastic layered Boussinesq calculation theory and ABAQUS finite element numerical model, the distribution law of stress, the displacement of the aircraft wheel load acting on different positions of the pavement slab, the influence of the added dowel bar on the pavement slab, and the load transfer between adjacent slabs are obtained. The results revealed that when the wheel load of the aircraft acts on the edge and joint of the slab, the vertical stress of the adjacent slab edge is largest, followed by the middle of the slab, and then the joint; the maximum vertical stress is 0.295 MPa. Furthermore, the aircraft wheel load on the slab edge, and the joint vertical displacement, is larger than that of the slab middle, and the adjacent slab edge transverse displacement attenuation coefficient is approximate. Moreover, the load transfer efficiency of the dowel bar was lower when the wheel load of the aircraft was closer to another unloaded slab. Finally, the validity and sensitivity of the simulation results are verified by laboratory test data. These results can provide a reference and suggestions for the design and production of the precast concrete pavement of airport runways