Locomotion analysis of hexapod robot

Multi-legged robots display significant advantages with respect to wheeled ones for walking over rough terrain because they do not need continuous contact with the ground. In Multi-legged robots, hexapod robots, mechanical vehicles that walk on six legs, have attracted considerable attention in recent decades. There are several benefits for hexapods rover. (a) Hexapod robot is easy to maintain static stability on three or more legs, (b) It has a great deal of flexibility in how it can move. (c) Hexapod robot is the most efficient one for statically stable walking. Preumount et al. 1991, observed that a larger number of legs more than six do not increase walking speed. (d) Hexapod robots show robustness in case of leg faults (e) Hexapods makes it possible for the robot to use one, two or three legs to work as hand and perform complex operations. The most studied problem for multi-legged robots concerns how to determine the best sequence for lifting off and placing the feet (gait/locomotion planning). From the stability point of view, robot locomotion can be classified into dynamic locomotion, such as running and hopping, and statically stable locomotion as walking. Statically stable locomotion has the constraint that the moving body is stable at all times. The vertical projection of the centre of gravity of the robot must be within the convex of the supporting polygon linked positions of all supporting feet. Statically stable gait is solely dependent on the design of bodies and legs. Hexapod gaits have been widely investigated as a function of shape and characteristics of the robot structure. In 1985, Kaneko et al. addressed the gait of a rectangular hexapod with decoupled freedoms where the propelling motion was generated by one degree of freedom (DOF). In 1988, Lee et al. realized an omnidirectional walking control system for a rectangular hexapod robot with adaptive suspension. A circular gait was studied for a layered hexapod robot (called Ambler) at the Carnegie Mellon University [Bares et al., 1989; Krotkov & Bares, 1991; Wettergreen, 1990] with rotating legs connected to the same vertical axis at six different heights. Hirose et al. in 1992 and 1998 and Gurocak in 1998 developed other two hexapods whose bodies were consisting of two different layers, each connected to three legs. The relative motion of the layers realized the omnidirectional robot gait in a simple way, but limiting the walking capability under leg faults. Two Lees in 2001 studied the gait of a special robot whose body was composed of three parts connected by revolute joints. Its 18