The stability, energetic efficiency and walking volume are effected by the geometric structure of legs of walking robot. By the way a pantograph mechanism is used to separate the vertical and horizontal motions and transfer them from the actuators to the foot but sliding joints are difficult to design satisfactory. To investigate the characteristics of 3-D legged motion of pantograph mechanism, a graphic simulator may be used efficiently. In this thesis, the three quadruped robots for the third joint were modeled with data structure. Their kinematics, inverse kinematics, and walk volumes were analyzed, and locomotions were simulated in 2-D space. The locomotions are composed of rotation and side walk, thus leg control is required in rotation walk, and leg sequence are modified due to walking direction for static stability. It is difficult to imagine the joint motion of a robot with pantograph legs so that the graphic simulator can be used to observe the characteristics of the robot easily by animation, and to reduce the development cost and period.
