A Wearable Soft Fabric Sleeve for Upper Limb Augmentation

Soft actuators (SAs) have been used in many compliant robotic structure and wearable devices, due to their safe interaction with the wearers. Despite advances, the capability of current SAs is limited by scalability, high hysteresis, and slow responses. In this paper, a new class of soft, scalable, and high-aspect ratio fiber-reinforced hydraulic SAs is introduced. The new SA uses a simple fabrication process of insertion where a hollow elastic rubber tube is directly inserted into a constrained hollow coil, eliminating the need for the manual wrapping of an inextensible fiber around a long elastic structure. To provide high adaptation to the user skin for wearable applications, the new SAs are integrated into flexible fabrics to form a wearable fabric sleeve. To monitor the SA elongation, a soft liquid metal-based fabric piezoresistive sensor is also developed. To capture the nonlinear hysteresis of the SA, a novel asymmetric hysteresis model which only requires five model parameters in its structure is developed and experimentally validated. The new SAs-driven wearable robotic sleeve is scalable, highly flexible, and lightweight. It can also produce a large amount of force of around 23 N per muscle at around 30% elongation, to provide useful assistance to the human upper limbs. Experimental results show that the soft fabric sleeve can augment a user’s performance when working against a load, evidenced by a significant reduction on the muscular effort, as monitored by electromyogram (EMG) signals. The performance of the developed SAs, soft fabric sleeve, soft liquid metal fabric sensor, and nonlinear hysteresis model reveal that they can effectively modulate the level of assistance for the wearer. The new technologies obtained from this work can be potentially implemented in emerging assistive applications, such as rehabilitation, defense, and industry.

Developing Student-Teachers’ Understanding of Geometrical Figures/Objects Using a Bicycle Rubber Tube

This paper addresses the ways that a bicycle rubber tube can be used to develop learners’ understanding of geometrical figures/objects. The use of a bicycle rubber tube is important because student-teachers and in-service teachers can use the material to teach learners in schools to understand various geometrical figures/objects. In doing so, geometrical figures and objects, metric, and metric space are understood relationally. Using a bicycle rubber tube, it was found that various geometrical figures and objects were formed, including rectangle, triangle, square, and pentagon. The finding has implications in teaching geometrical figures/objects, including teachers can use a bicycle rubber tube to develop learners’ understanding of a circle, rectangle, triangle, square, pentagon and hexagon.

A new incremental calculated approach to predict maximum contact stress of compressed packer in large deformation

Compressed packer rubber is large deformation material, which endures biaxial contact friction between oil-pipe and casing-pipe in sitting and sealing process. Large-deformation theory analysis of rubber brings huge difficulties to solve, this is due to the material, geometry and contact non-linearity should be considered. In this article, the deformation of compressed packer rubber tube (CPRT) is divided into free deformation, unidirectional and bidirectional constrained deformations. Based on the theory of thick-wall-cylinder and the linear constitutive of rubber material segment, the CPRT mathematical model in different deformation processes is established and the influences of axial load, axial height of CPRT and contact friction coefficient of casing inner wall etc are considered. Based on incremental calculated approach, the mathematical model is solved. By comparing the results of the theoretical model with the results of finite element method and experimental results, it is found that the theoretical maximum contact stress is more conservative than the FEM and experimental solutions, so the sealing reliability of packer effectively predicted under the premise of allowable contact stress and the theoretical results can provide a lower limit reference value for the contact stress of the packer in the actual seal process. Meanwhile, the deviation of contact stress in FEM and theoretical value at z150 height of CPRT is among 1.13%∼4.90%, which can predict the contact stress in the compressed area near the stress concentration upper end-face of CPRT under the low friction factor, the results provide a reference for the compressed packer design.

A modified physical model of high-strength water hydraulic artificial muscles considering the effects of geometry and material properties

Compared with pneumatic artificial muscles (PAMs), water hydraulic artificial muscles (WHAMs) have the advantages of high force/weight ratio, high stiffness, rapid response speed, large operating pressure range, low working noise, etc. Although the physical models of PAMs have been widely studied, the model of WHAMs still need to be researched for the different structure parameters and work conditions between PAMs and WHAMs. Therefore, the geometry and the material properties need to be considered in models, including the wall thickness of rubber tube, the geometry of ends, the elastic force of rubber tube, the elongation of fibers, and the friction among fiber strands. WHAMs with different wall thickness and fiber materials were manufactured, and static characteristic experiments were performed when the actuator is static and fixed on both ends, which reflects the relationship between contraction force and pressure under the different contraction ratio. The deviations between theoretical values and experimental results were analyzed to investigate the effect of each physical factor on the modified physical model accuracy at different operating pressures. The results show the relative error of the modified physical model was 7.1% and the relative error of the ideal model was 17.4%. When contraction ratio is below 10% and operating pressure is 4 MPa, the wall thickness of rubber tube was the strongest factor on the accuracy of modified model. When the WHAM contraction ratio from 3% to 20%, the relative error between the modified physical model and the experimental data was within ±10%. Considering the various physical factors, the accuracy of the modified physical model of WHAM is improved, which lays a foundation of non-linear control of the high-strength, tightly fiber-braided and thick-walled WHAMs.

Determination of Fracture Toughness of Mode I Fractures from Three-Point Bending Tests at Elevated Confining Pressures

Fracture toughness is one of the key parameters for the characterization of brittle rock fracturing. Yet, constraints on it mainly rest on measurements performed at ambient pressure, although rock fracturing frequently occurs at elevated pressures even in geotechnical applications. To address the lack of a generally accepted evaluation procedure for tests at elevated pressure we explored the conditions for initiation and propagation of mode I fractures in samples subjected to bending at elevated pressure by numerical modeling and analytical considerations of the involved angular moments. We derived an evaluation procedure and applied it to experimental observations for specimens with either a chevron or a single-edge notch of four different rocks (a granite, a limestone, a marble and a sandstone) subjected to three-point bending at confining pressures up to 30 MPa. Two sealing methods were considered. Specimens were either varnished or jacketed by a rubber tube, differing in whether pressure is allowed to build up inside the pre-fabricated notch or not, respectively. Irrespective of notch geometry and sealing method, the determined toughness values increase significantly with confining pressure. The apparent toughness determined for jacketed specimens is, however, larger than that for varnished specimens, for which toughness seems to reach a plateau with increasing pressure. The similarity of the pressure dependence of the toughness determined for varnished, i.e., uniformly pressurized, samples with that of other physical properties suggests that it is controlled by the closure of pre-existing micro-cracks; the absence of pressure dependence beyond some tens of MPa suggests that non-linearity effects may not be as severe at depths beyond a few kilometers as previously discussed. Our study points to the necessity of resolving numerical issues associated with compressed fractures and of further improving experimental facilities for the determination of fracture toughness at elevated pressure.

Design and Optimization of Rubber Tube of Orifice BoP

The rubber tube is made of rubber material. It is the important part of the orifice boP. The rubber tube is squeezed and deformed to contact with the drill pipe to achieve the sealing function. There are large deformation and contact problems in the sealing process of rubber, which is difficult to calculate theoretically. In this paper, finite element analysis software is used to analyze the contact stress between the designed rubber cylinder and the drill pipe under different loads and the influence of friction factor on the contact stress. The influence rules are summarized, the structure of the rubber cylinder is optimized, and the contact stress of the optimized rubber cylinder is analyzed. The results meet the design requirements.

Development of Soft Pneumatic Actuators Using High-Strain Elastic Materials with Stress Anisotropy of Short Fibers

In recent years, soft robots, such as those with high human affinity and those that excellently imitate the movements of natural creatures, have gained considerable attention. In soft robots, structurally flexible soft actuators need to be used, not conventional motors or hydraulic/pneumatic cylinders. Various types of soft actuators have been developed depending on the driving principle. A pneumatic rubber artificial muscle is a kind of soft actuator that acquires power through injection of a working fluid, such as air, into an elastic structure, such as rubber. In this study, the authors developed an actuator, namely, the straight-fiber-type artificial muscle, which exhibits excellent contraction characteristics. This artificial muscle consists of a rubber tube that contains reinforcing fibers arranged in the axial direction. When air pressure is applied to the rubber tube, the artificial muscle expands only in the radial direction and contracts in the axial direction due to the restraining effect of the reinforcing fiber. While this artificial muscle exhibits excellent contraction properties, it has some drawbacks. One is the difficulty in enclosing the reinforced fibers that have accumulated in the rubber tube, making this artificial muscle difficult to manufacture. In this study, we investigated short-fiber-reinforced artificial muscles that can be easily manufactured. First, a short-fiber-reinforced rubber was prepared, and anisotropy was evaluated via a tensile test. Then, the short-fiber-reinforced artificial muscles were prepared, and their contractions rates were evaluated. The results confirmed that a short-fiber-reinforced rubber can be useful for the manufacture of artificial muscles.

Designing and manufacturing of a user friendly and affordable nasal suction machine for Acute Bronchiolitis treatment of children in Oman

Acute Bronchiolitis is a disease which usually infects children of the age 0 to 6 years old. The patients infected by this disease require medical attention at hospitals. The patients must be admitted in the hospitals for a period of 2-3 days. Parents of the patients must stay in the hospital along with them. This causes lack of hospital beds, more expense of the hospital to provide extra food for the parents. By a qualitative research, it was found that parents would want an affordable device so that they could care for their children from home instead of staying at the hospital. Parents from all over Oman come to the capital so that their children can be treated. Children also tend to get exposed to more sickness by being around sick children at the hospital. Taking this problem into consideration, a circuit has been designed in such a way it was easy to use and that it could be used by parents to treat their children at home without the need to visit a hospital. The circuit works on Arduino Uno and has various pre-existing modules attached to it , the estimated cost of the device is far lesser than what the mainstream industrial devices cost. The device consists of a Bluetooth Module for the purpose of connectivity via cellphone ,a 12V vacuum pump to suck the mucus out of the patient’s lungs, variable resistor to control the force of vacuum and a rubber tube capable of fitting into the nostril to allow suction of mucus. This simple device made from the counter parts can offer significant benefits to patients affected by Acute Bronchitis.

Two Methods to Assess Aortic Compliance Using Blood Pressure and Pulse-Wave Velocity

Aortic compliance has been well established as an independent predictor of cardiovascular morbidity and mortality. The current "gold standard" for assessing aortic compliance is to use the carotid-femoral pulse-wave velocity (PWV) as a surrogate; however, PWV alone has been discussed in the literature as being inadequate for assessing compliance, especially for elderly patients and others who have a stiff aorta. In this paper an equation for the aortic compliance is developed using two approaches: 1) lumped-parameter modeling based on blood-pressure data and 2) distributed modeling based on the PWV. In-vitro experiments are conducted using a silicone-rubber tube which simulates the aorta, and an actual aorta harvested from a 1-year old, Holstein heifer. For both the rubber aorta and the Holstein aorta, a comparison is made between the blood-pressure model and the PWV model. In conclusion it is shown that good agreement exists between the two models, suggesting that either model may be used depending upon the available data. Furthermore, due to differences in material properties, it is shown that the compliance of the rubber aorta increases with mean arterial-pressure, while the compliance of the Holstein aorta decreases with mean arterial-pressure. Clinical implications of this research are also discussed.

A Water-Hydraulic Upper-Limb Assistive Exoskeleton System with Displacement Estimation

This paper describes the development of an angle-sensorless exoskeleton with a tap water-driven artificial muscle actuator. The artificial muscle actuator consisted of an elastic rubber tube reinforced by braided fiber. Such actuators are highly flexible, lightweight, and water-resistant, and thus are inherently safe even for operations in direct contact with humans. An estimation system for the displacement of the artificial muscle actuator based on the water flow rates detected by flowmeters was constructed for the water-hydraulic exoskeleton. In addition, estimators of the velocity and acceleration of the actuator based on the estimated displacement and the measured flow rates were derived and incorporated into the estimation system. With this system, our previous wearable upper-limb assistive exoskeleton prototype was converted into an angle-sensorless version with higher safety in wet conditions. Its assistive performance was evaluated through experiments with research participants. Experimental results demonstrated that muscle activity could be reduced, although an assistive control strategy was executed with the variables estimated, excluding force.