This paper presents the temperature-pressure characteristics of a newly developed SMH actuator using hydrogen-absorbing
alloys. The new special metal hydride(SMH) actuator is characterized by its small size, low weight, noiseless
operation, and compliance similar to that of human bodies. The simple SMH actuator, consisting of plated hydrogen-absorbing
alloys as a power source, Peltier modules as a thermal source, and a cylinder with metal bellows as a
mechanical functioning part, has been developed. An assembly of copper pipes has been constructed to improve the
thermal conductivity of the hydrogen-absorbing alloys. It is well known that hydrogen-absorbing alloys can reversibly
absorb and desorb a large amount of hydrogen, more than about one thousand times of their own volume. By heating the
hydrogen-absorbing alloys, the hydrogen equilibrium pressure increases due to desorption of hydrogen, whereas, by
cooling the alloys, the hydrogen equilibrium pressure drops due to absorption of hydrogen by the alloys. The new SMH
actuator utilizes the reversible reaction between the thermal energy and mechanical energy of the hydrogen absorbing
alloys. To be able to use the SMH actuator in medical and rehabilitation applications, the desirable characteristics of the
actuator have been studied. For this purpose, the detailed characteristics of the new SMH actuator for different
temperature, pressure, and external loads were explored.
The dynamic characteristics of the special metal hydride(SMH) actuator using hydrogen absorbing alloys has been studied through the experiments on the characteristics of the temperature-pressure relation using a Peltier module. The SMH actuator uses the reversible reactions between thermal energy and mechanical energy inside hydrogen-absorbing alloys. It is well known that hydrogen-absorbing alloys can reversely absorb and desorb a large volume of hydrogen gas, more than about 1000 times of their own volume. By using Peltier element, we can actively control the energy conversion through hydrogen-absorbing alloys through hydriding and dehydriding reactions. Heating hydrogen-absorbing alloys using Peltier element will increase the equilibrium pressure of hydrogen gas resulting in the desorption of hydrogen gas by the alloys. Whereas, by cooling the alloys, the equilibrium pressure of hydrogen gas will decrease and hydrogen gas will be absorbed. In the present study, a simple special metal hydride (SMH) actuator, consisting of plated hydrogen-absorbing alloys as a power source, Peltier elements as a heat source, and a cylinder with metal bellows as a mechanical functioning part, has been developed. An electro-less copper plating has been used to improve the thermal conductivity of the hydrogen-absorbing alloys. To study the effects of the electro-less copper plating and the dynamic characteristics of the newly developed SMH actuator, a series of experiments has been performed and analyzed. The experiment demonstrated that the SMH actuator, which contains only 14.5 g of hydrogen-absorbing alloys, was able to easily lift 40 kg of weight with the displacement of 35 mm. The displacement of the cylinder was controlled in the periodic movement. The developed SMH actuator has merits in its small size, light weight, noiseless operation, and compliances similar to those of human bodies. Therefore, the SMH actuator is suitable for uses in medical and rehabilitation applications.
It proposed a new early rehabilitation training system for postural control using a tilting bed, a visual display and a force plate. The conventional rehabilitation systems for postural control can't be applied to the patients lying in bed because the rehabilitation training using those systems is only possible when the patient can stand up by himself or herself. Moreover, there did not exist any device that could provide the sense of balance or the sensation of walking to the patients in bed. The software for the system consists of the training program and the analysis program. The training program was designed to improve the ability of postural control of the subjects by repeated training of moving the center of pressure (COP) applied to the forceplate. The training program consists of the COP maintaining training and the COP movement training in horizontal, vertical, 45° and -45° directions. The analysis program consists of the COP moving time analysis modules, the COP maintaining time analysis module. Through the experiments with real people, it verified the effectiveness of the new early rehabilitation training system. The results showe that this system is an effective system for early rehabilitation training and that our system might be useful as clinical equipment.
There developed a lower limb orthosis with a pneumatic rubber actuator, which can assist and improve the muscular activities in the lower limb of the elderly. For this purpose, the characteristics of the lower limbs muscle activities for various pressures in the pneumatic actuator for the lower limb orthosis was investigated. To find out the characteristics of the muscle activities for various pneumatic pressures, it analyzed the flexing and extending movement of the knees, and measured the lower limbs muscular power. The subjects wearing the lower limbs orthosis were instructed to perform flexing and extending movement of the knees. The variation in the air pressure of the pneumatic actuator was varies from one kgf/cm<sup>2</sup> to four kgf/cm<sup>2</sup>. The muscular power was measured by monitoring electromyogram using MP100 (BIOPAC Systems, Inc.) and detailed three-dimensional motions of the lower limbs were collected by APAS 3D Motion Analysis system. Through this study, it expected to find the most suitable air pressure for the improvement of the muscular power of the aged.