Development of a SMH actuator system using hydrogen-absorbing alloys

A special type of metal hydride (SMH) actuator has been developed and the pressure response inside the actuator has been studied against changing temperature controlled by Peltier elements. The newly developed SMH actuator is characterized by its smaller size, lower weight, noiseless operation, and compliance similar to that of human bodies. The simple SMH actuator, consisting of powdered hydrogen-absorbing alloys as a source of mechanical power, Peltier elements as a thermal source, and a cylinder with metal bellows as a mechanical element, has been developed. An assembly of copper pipes, which has good thermal conductivity, has been constructed to contain hydrogen-absorbing alloys. Hydrogen-absorbing alloys can reversibly absorb and desorb a large volume of hydrogen, more than about one thousand times their own volume. The new SMH actuator utilizes the reversible reactions between thermal energy and mechanical energy of hydrogen-absorbing alloys. Furthermore, the characteristics of the actuator for different temperature, pressure, and external loads were studied and explored to allow the developed SMH actuator to be used in medical and rehabilitation applications.