Reduced DOF Type Walking Robot Based on Closed Link Mechanism

Abstract

The types of mobile robot can be roughly divided into three categories, wheeled type, crawler type and legged type. In these types, walking machine (legged type robot) has some of noteworthy strong points that other types of mobile robot don't have. Especially, high adaptability to the terrain is one of the most important strong points of walking machine. The fact that general type of walking machine has many numbers of DOF is essential reason of the above mentioned strong point. However, this fact causes a serious problem that it is very difficult to build up a walking machine that can be into practical use. The following matters are the main reason that disturbs to make walking machine into practical use. 1. Automatic control is required for each DOF (Degrees Of Freedom) 2. Energy cost of walking machine is fully worse than that of other kinds of mobile machines It goes without saying that automobile that is typical type of wheeled machines has been already made into practical use. In case of automobile, its essential DOF is only two. Therefore, it is able to put the DOF of them under human control. On the contrary, in case of walking machine, number of DOF is too many to put them under human control. Thus, technique of automatic control including complex calculation of kinematics is absolutely required for walking machine. The second matter is more serious. The fact that walking machine requires many DOF means that many actuators corresponding to the number of DOF are required. Although increasing of number of actuators does not always influenced to efficiency of energy cost, it is very difficult to realize mechanical design that can keep superior energy efficiency. As a result of it, energy costs of walking machine is often made be so bad. Some design technique is required to solve this problem. To overcome the problem, a new notion that is called reduced DOF design has been proposed. Generally, conventional walking robot requires three DOF for each leg. Therefore, 12 DOF and 18 DOF are required for general type of quadruped machine and that of hexapod machine for each. However, these numbers are not always minimum required number for walking machine. On this point of view, to improve energy efficiency of walking machine by reducing number of DOF is main purpose of the notion of reduced DOF. Based of this notion, some types of walking robot has been developed (Yoneda et al. 2001), (Ota et al. 2001), (Iida 2003) and (Behzadipour 2004). O pe n A cc es s D at ab as e w w w .ite ch on lin e. co m