Passive-type Intelligent Walker Controlled Based on Caster-like Dynamics

With the coming of aging societies, many elderly people have serious problems for their locomotion, because of the decline of the physical strength for walking. If they could not use their legs for walking, their physical strength would be weak gradually and they could not walk finally without assistance of other people or some assist system such as wheel chairs, etc. The walking using legs of themselves is very important for improving the quality of their lives, even if they use several kinds of tools for walking such as cane, walker, etc. In this paper, we pay attention to the walker which support the human based on the physical interaction between the human and the walker. The simple walkers, which consist of support frame, wheels/casters and hand-brakes, are used commercially in many fields such as home, hospital, outside, and so on. On the other hand, to develop the intelligent walkers, many researchers have been proposed several kinds of walkers. Manuel et al. have proposed non-holonomic navigation system of a walking-aid robot referred to as “Care-Obot II” [1]. Savaniti et al. have developed the motorized “Rollator” [2]. Dubowsky et al. have proposed “PAMM” system to provide a mobility assistance and monitoring for the health status of the user [3]. Fujie et al. have developed the power assisted walker for physical support during walking [4]. We have developed the motion control algorithm of intelligent walker with omni-directional mobile base in which the system is moved based on the intentional force/moment applied by user [5]. Kotani et al. have also proposed “HITOMI” system for permitting outdoor navigation of blind people [6]. The most of the conventional intelligent walkers utilize the servo motors and control them by using the information of sensors such as force/torque sensor, ultra sonic sensor, laser range finder, and so on, to realize the several kinds of functions. Although the active-type walkers using servo motors could realize many functions such as collision avoidance, path following, variable motion characteristics, and so on for supporting the user, the safety issues of this active-type system should also be considered. If we can not control the servo motors of the active-type walker appropriately, the system would move unintentionally and be a dangerous system for human being. In addition, the active-type system might be heavy and its structure might be complicated, because it consists of servo motors, reduction gears, sensors, controller, batteries, and so on. The battery problem is also very severe for its long time working, because the servo motors need much electricity to work. Therefore, the active-type systems still have many problems for their practical use.