2013 年 79 巻 807 号 p. 4131-4140
In this paper, a concept of power assistance of human motion, called “nonpositive power assistance” is proposed, mainly targeting the prevention of injuries in nursing-care activities. In this concept, only the human motions accompanied by isometric and eccentric muscle contractions, which are the main cause of the muscle fatigue and muscle fibre damages, are assisted, whereas the motions with concentric contraction, which require positive power input, are not supported. Since the nonpositive power assistance is feasible by using ON/OFF-controlled passive breaks installed in parallel with the muscles, this concept allows a design of an energy-saving power assist apparatus which may effectively prevent the user from muscle fatigue and muscle injury. A single-axis poof-of-concept test apparatus for the cubital joint assistance has been designed, and the experiments of cyclic loading-unloading-holding tasks using eight subjects have been carried out to evaluate the effectiveness of the proposed concept in terms of the surface electromyographic signals from the biceps brachii. It has been concluded that the progress of the muscle fatigue has been significantly reduced (p < 0.05) by using the proposed nonpositive power assist apparatus.