Gait Rehabilitation System Using a Non-Wearing Type Pneumatic Power Assist Device

In Japan, approximately 1.1 million people suffer from cerebrovascular diseases such as cerebral stroke, which can further increase due to the aging society. Therefore, rehabilitation for the physical recovery of patients with hemiplegia caused by cerebrovascular disease plays an important role in maintaining and improving their quality of life (QoL). In rehabilitation facilities, crutches and parallel bars are the mainstream, but patients support their body with their arms, causing falls and fatigue, leading to deterioration of motivation in long-term rehabilitation. Although a few hanging-type devices have been developed to cope with such issues, they occupy large space, require time to wear, and have a high introduction cost. In this study, we developed a non-wearing-type pneumatic power assist device for gait rehabilitation to ensure patients can sustain their body weight by pushing up their armpit and quantitatively verified the effectiveness of the device.

Electro-pneumatic pumps for soft robotics

Soft robotics has applications in myriad fields from assistive wearables to autonomous exploration. Now, the portability and the performance of many devices are limited by their associated pneumatic energy source, requiring either large, heavy pressure vessels or noisy, inefficient air pumps. Here, we present a lightweight, flexible, electro-pneumatic pump (EPP), which can silently control volume and pressure, enabling portable, local energy provision for soft robots, overcoming the limitations of existing pneumatic power sources. The EPP is actuated using dielectric fluid–amplified electrostatic zipping, and the device presented here can exert pressures up to 2.34 kilopascals and deliver volumetric flow rates up to 161 milliliters per second and under 0.5 watts of power, despite only having a thickness of 1.1 millimeters and weight of 5.3 grams. An EPP was able to drive a typical soft robotic actuator to achieve a maximum contraction change of 32.40% and actuation velocity of 54.43% per second. We highlight the versatility of this technology by presenting three EPP-driven embodiments: an antagonistic mechanism, an arm-flexing wearable robotic device, and a continuous-pumping system. This work shows the wide applicability of the EPP to enable advanced wearable assistive devices and lightweight, mobile, multifunctional robots.

Development of Non-Wearing Type Pneumatic Power Assist Device – Basic Concept and Performance Evaluation –

In Japan, where aging is faster than ever, the shortage of a young labor force is a serious problem, especially in the nursing field to support care recipients and in the primary industrial field to support heavy labor. Hence, the use of power assist devices that mechanically reduce the burden on the body is drawing increasing attention. This study focuses on the lifting motion, which can be performed by two methods, the squat method and the stoop method; the former involves bending the knee and the latter involves using the waist. The squat method is recommended because the burden on the waist is lower than that in the case of the stoop method. Currently, many types of wearable power assist devices to reduce the burden on the waist have been developed; however, they are based on the stoop method because of their assist mechanism. In this study, we developed a non-wearing type pneumatic power assist device that allows the squat method. After describing the basic concept and assist mechanism, the support effects are confirmed through experiments.

Design and Modeling of Soft Pneumatic Helical Actuator with High Contraction Ratio

Soft contraction actuators are becoming important elements particularly for human-friendly robotic applications. However, it is challenging to achieve both a large operating distance while generating practical force. Hence, we present a new soft contraction actuator capable of realizing a high ratio contraction by pneumatic power. It can be easily fabricated using soft materials, including rubber tubes, one-way extensible cloth, and inextensible wire. Its initial shape is tubular but it can curve and coil to a helix shape owing to its different extensibilities on two sides when pressurized. A maximum contraction ratio of 78% and a 23 N contraction force can be achieved with an 11.6 mm initial outer diameter tube under 0.3 MPa. The effect of the tilt angle of a one-way extensible cloth on the helical shape is investigated, and a mathematical model illustrating the relationship between the contraction ratio and force is derived. Our experimental results suggest that this helical actuator has a much higher contraction ratio than a McKibben actuator under the same conditions. Finally, we discuss the potential application of the proposed actuator to a wearable device, i.e., for assisting the dorsiflexion of an ankle joint requiring a wide range of motion.

Parametric Study for an Oscillating Water Column Wave Energy Conversion System Installed on a Breakwater

This study focuses on the analysis of the parameters of an oscillating water column (OWC) wave energy conversion system and wave conditions. Interactions between the dimensions of the OWC chambers and wave conditions are all taken into account to design an alternative OWC converter, called caisson-based OWC type wave energy converting system. A numerical method using an unsteady Navier-Stokes equations theorem in conservation form is used to analyze the proposed analytical model. The objective of this study is to try to apply an OWC wave energy converter to a caisson breakwater, which has been constructed in a harbor. The structure proposed in this study is a series of sets of independent systems, in which each set of converters is composed of three chambers to capture the wave energy, while better ensuring the safety of the caisson breakwater. Responses to be analyzed related to the conversion efficiency of the caisson-based OWC wave energy converting system include the airflow velocity from the air-chamber, the pneumatic power and the conversion efficiency in terms of a ratio between the pneumatic power and the energy of the incident waves. Parameters examined in this study include the dimensions of the OWC chamber features such as the orifice of the air-chamber allowing airflow in/output, the chamber length along the direction of incident waves, the size of the opening gate for incident waves and the submersion depth of the air-chamber. As found from the results, a best conversion efficiency from incident waves of 32% can be obtained for the extreme case where the orifice is very small, but for most other cases in the study, the best efficiency is about 15%.

The Wave-to-Wire Energy Conversion Process for a Fixed U-OWC Device

Oscillating water column (OWC) devices, either fixed or floating, are the most common wave energy converter (WEC) devices. In this work, the fluid dynamic interaction between waves and a U-shaped OWC breakwater embedding a Wells turbine has been investigated through unsteady Computational Fluid Dynamic (CFD) simulations. The full-scale plant installed in the harbor of Civitavecchia (Italy) was numerically modeled. A two-dimensional domain was adopted to simulate the unsteady flow, both outside and inside the U-OWC device, including the air chamber and the oscillating flow inside the conduit hosting the Wells turbine. For the numerical simulation of the damping effect induced by the Wells turbine connected to the air chamber, a porous medium was placed in the computational domain, representing the conduit hosting the turbine. Several simulations were carried out considering periodic waves with different periods and amplitudes, getting a deep insight into the energy conversion process from wave to the turbine power output. For this purpose, the three main steps of the overall energy conversion process have been examined. Firstly, from the wave power to the power of the water oscillating flow inside the U-duct. Secondly, from the power of the oscillating water flow to the air pneumatic power. Finally, from the air pneumatic power to the Wells turbine power output. Results show that the U-OWC can capture up to 66% of the incoming wave power, in the case of a wave period close to the eigenperiod of the plant. However, only two-thirds of the captured energy flux is available to the turbine, being partially dissipated due to the losses in the U-duct and the air chamber. Finally, the overall time-average turbine power output is evaluated showing that it is strongly influenced by a suitable choice of the turbine characteristics (mainly geometry and rotational speed).

Analysis of 6-Pulse and 12-Pulse in Conversion of the 115VAC/400Hz to 270 VDC for Application on Fighter

The development of aircraft secondary power technology is moving from mechanical power, pneumatic power and hydraulic power to electric power. The trend toward electric power is known as More Electric Aircraft (MEA). Modern military aircraft are designed using 270VDC for electric power system. Today, some military aircraft still use 115VAC/400Hz for their electrical power system. If this type of aircraft need provides 270VDC electrical power, then they require Multi-Pulse Transformer Rectifier Unit (TRU). The development of this type TRU has not been aimed to comply with aircraft military standards. This research investigates the variation of the number of pulses (p) and firing angle (α) to the amplitude ripple voltage, output voltage, and distortion factor in order to comply with the MIL-STD-704F standards. The multi-pulse transformer rectifier unit being analyzed consists of 6-Pulse and 12-Pulse. The research shows that the amplitude ripple voltage and distortion factor of the 6-Pulse TRU do not comply MIL-STD-704F. The amplitude ripple voltage and distortion factor of 12-Pulse comply MIL-STD-704F with firing angle (α) ≤4°.Keywords: Transformer Rectifier Unit, thyristor, ripple voltage, distortion factor, firing angle