An omnidirectional gait control using a graph search method for a quadruped walking robot

Two major approaches exist for devising gait control for a legged machine: 1) finding a sequence of leg and body movements of a robot on the basis of kinematic and possibly dynamic considerations assuming all foot placements are valid; and 2) selecting leg and body movements first on the basis of feasibility of foot placements and then accepting those that also satisfy kinematic and possibly dynamic constraints. Consider now the problem of a legged robot pursuing a quarry. With the first approach, the robot will be limited to operating over a relatively flat terrain. If the terrain is uneven, however, the robot will have no choice but to take recourse to the second approach even though it is computationally more demanding. The work done so far in the second approach is limited by either the constraint that the overall direction of ambulation of the robot is known in advance, or by the constraint that the foot placements are limited to the points of a grid superimposed on the topographic map of the terrain. In this paper, the authors discuss how a free gait can be generated for following a quarry without invoking such constraints.