Contents I. Introduction
Robotic gait rehabilitation, which combines a human model and a robot assistance together, has been focused on the rehabilitation or assistance for walking (e.g., the gait training [1]– [9], the augmentation system [10]– [14], the compensation system [15], [16]), although the stability between the human and device is significant. In the view from different standpoint, the stability for the human has been considered in the initial research stage. The well-known body weight-support treadmill training (BWSTT) is a representative system to consider the human stability. It means that the semimounted type of BWSTT is the settled device for the human to pose the stationary walking by remaining balance [1], [2], [12]. Similarly, the nonmounted type assists the walking motion by ensuring the walking stability and mobility [4], [8] , [11], [17]– [25]. However, the assumption that the subject has an ability to walk alone is essential to use the nonmounted type. Many research works on the stability have been studied regarding the semimounted and nonmounted type, while the research on the mounted type rarely exists.
