Development of an actuation system to apply hydrogen storage alloy for the rehabilitative system.

BACKGROUND: Hydrogen has advantages that can be used as energy, but research on safe use is needed. OBJECTIVE: In this study, an actuation system for rehabilitation is developed to drive the actuator using hydrogen storage alloy and to analyze the hydrogen release characteristics of the alloy. METHODS: The system is automatically control and report the pressure, temperature and hydrogen flow using LabVIEW-based modules and LabVIEW software. Zr0.9Ti0.1Cr0.6Fe1.4 alloy was selected as hydrogen storage alloy. 5 MPa of hydrogen pressure was applied at 8.56 g of alloy powder for activation process and the temperature outside was maintained at 19∘C to 21∘C. The amount of hydrogen absorption was measured about 1.47 wt%. The actuation test was conducted at the temperature from 25∘C to 80∘C, increased by every 5∘C. The actuation height was measured at each load of 5, 10, 15, and 20 kg. The voltage and current which is applied to peltier elements were set to 5.0 V and 2.5 A. The pressure changing in the system was checked for 5 min for each temperature, however, if the temperature at which the pressure inside the system changed, the time to heat the module was increased to 20 min. Hydrogen was first released at 70∘C. RESULTS: The loads of 5 and 10 kg were raised by 87 and 19 mm at 70∘C, respectively. At 75∘C, loads of 5, 10 and 15 kg were raised by 131, 70, and 15 mm, respectively. At 80∘C, 5, 10, 15, and 20 kg were raised by 150, the end of the actuator, 83, 55, and 28 mm, respectively. CONCLUSIONS: The actuation system in this paper can be applied to assistive device and rehabilitation system for assisting the movement of daily life of the elderly or people with disability.

Rehabilitative training system based on a ceiling rail for detecting the intended movement direction of a user.

BACKGROUND: Accurate detection of the intended movement direction of a patient plays an important role in the development of a training system for gait rehabilitation and enables to increase the effect of gait rehabilitation training. OBJECTIVE: This study investigated the detection of the intended movement of a user to operate a ceiling rail-based rehabilitative training system with accurate timing. METHODS: To detect the movement direction intention of a user, two potentiometers were used to measure the movement direction in the anterior, posterior, and left and right directions of the user when operating the driving motor of the rehabilitative training system. A simple test mock-up with two potentiometers was fabricated, and the experiments were conducted to determine the effect of the direction of movement on the measured values of potentiometers. A direction measurement algorithm was developed to control the driving motor of the rail-based gait rehabilitative training system. RESULTS: The intended movement direction of the user could be predicted for eight directions by combining the "positive value, 0, negative value" of each measured value of the two potentiometers. Further, the developed algorithm was effectively used to control the driving function to assist the walking, sitting-standing, and climbing up-down the step activities in daily life. CONCLUSIONS: The movement intention detection function for users developed in this paper can be used to effectively control a rehabilitative training system for patients with hemiplegia to improve gait movement and posture balance, thereby improving their function of activities of daily living.

Study on injection molding analysis of glasses-type wearable device for facial skin care.

BACKGROUND: With the improvement in the standard of living, there has been increasing interest in facial skin care. In particular, it has been observed that people pay extra attention to eye-skin when they visit skin care parlors for special treatment and care. OBJECTIVE: There is a need for skin care devices that would enable convenient skin care anywhere, including at home and on the move. In this research, we developed a prototype of a glasses-type skin care device with a LED (Light-Emitting Diode) irradiation function and performed injection molding analysis of the skin care device model for mass production. METHODS: First, the product was designed using a universal design to improve the wearability of the glasses-type skin care device. The first prototype of the skin care device was produced using an integrated LED optical module capable of irradiating at three LED wavelengths to investigate the structural function of the product. The prototype was classified into three mechanisms and injection molding analysis was performed. The fill time, temperature at flow front, injection pressure, clamp force, and deflection values were analyzed according to the appropriate number and location of gates into which the PC + PBT (Polycarbonate + Polybutylene terephthalate) resin was introduced. RESULTS: We found that all the other parts except the temple section of the device were inferior in moldability. CONCLUSION: In further studies, the 3D prototype will be modified to enhance moldability, and injection molding analysis with other materials as well as with PC + PBT resin will be performed.

Study on an actuation system development using temperature control of metal hydrides.

BACKGROUND: Hydrogen storage using metal hydride (MH) offers various advantages so the global research and development using MH alloys keeps growing. OBJECTIVE: In this paper, we developed a new actuation system using temperature control of the MH module. METHODS: The actuation system consisted of an MH module, fan, mass flow controller (MFC), solenoid valve, actuator, and a temperature and pressure sensor. The MH module, two fans and temperature sensors were set for heating and cooling the MH power by electricity. Two MFCs and four pneumatic solenoid valves were used for controlling the direction and measuring hydrogen flow. Two actuators were used to evaluate performance of the MH alloy, and all the results were measured by LabVIEW software. Hydrogen was absorbed by the MH alloy by pressurizing at 1 MPa, and the absorbed hydrogen was desorbed using a vacuum pump. RESULTS: The temperature condition of the driving test was 20-50∘C. As the module was heated, it was confirmed that the actuator connected to the system was driven by the pressure of desorbed hydrogen. CONCLUSION: It is confirmed that the actuation system is suitable for the evaluation of characteristics of MH alloy. Future studies are planned to develop MH alloys and test the actual driving performance using this system.

Structural analysis of a rehabilitative training system based on a ceiling rail for safety of hemiplegia patients.

The body-weight support (BWS) function, which helps to decrease load stresses on a user, is an effective tool for gait and balance rehabilitation training for elderly people with weakened lower-extremity muscular strength, hemiplegic patients, etc. This study conducts structural analysis to secure user safety in order to develop a rail-type gait and balance rehabilitation training system (RRTS). The RRTS comprises a rail, trolley, and brain-machine interface. The rail (platform) is connected to the ceiling structure, bearing the loads of the RRTS and of the user and allowing locomobility. The trolley consists of a smart drive unit (SDU) that assists the user with forward and backward mobility and a body-weight support (BWS) unit that helps the user to control his/her body-weight load, depending on the severity of his/her hemiplegia. The brain-machine interface estimates and measures on a real-time basis the body-weight (load) of the user and the intended direction of his/her movement. Considering the weight of the system and the user, the mechanical safety performance of the system frame under an applied 250-kg static load is verified through structural analysis using ABAQUS (6.14-3) software. The maximum stresses applied on the rail and trolley under the given gravity load of 250 kg, respectively, are 18.52 MPa and 48.44 MPa. The respective safety factors are computed to be 7.83 and 5.26, confirming the RRTS's mechanical safety. An RRTS with verified structural safety could be utilized for gait movement and balance rehabilitation and training for patients with hemiplegia.