Four legged locomotion behavior has been studied and developed widely for the application on the uneven environments such as military services, space exploration, volcanic zone survey, power plan inspection, disaster zone rescue, and other rough terrain area. The gait planning of a quadruped robot should be proceeded intensively for the stable and effective working.
Existing organisms have been evolved optimally over a long time to survive in a variety of habitats. Numerous researchers have studied on
imitating the skeletal structure and the gait of legged animals in order to develop legged robots which have an ability to adapt to atypical environments. There have already been lots of researches on the gait of mammals that walk with an upright posture. Several quadruped robots mimicking the gait of horses or dogs have been developed. In the case of reptiles, the snake robots that mimic the shape and motion of snakes, and robots that mimic the ability of the gecko to move along a vertical wall have been developed. However, the development of the robots that mimic the gait of lizards is still in the beginning stage.
In this paper, the locomotion of a lizard was measured using the motion capture system. The walking motion of the lizard which trots in a sprawled posture was analyzed. A kinematic model was proposed to faithfully represent the sprawled walking motion of a lizard. The kinematic model has 25 degrees of freedom including four redundant limbs. The kinematics of redundant limb was solved using the plane equations of the shoulder, elbow, and ankle joints in order to mimic the gait of a lizard. The gait parameter of the lizard was derived by the analyzing the gait of the lizard and finally the sprawled gait was formulated using the gait parameter. The lizards'' kinematic parameters and dynamic parameters were applied in the commercial dynamic simulation software for the lizard dynamic modelling. The validity of the sprawled gait was verified with simulations to select trotting gait parameters.