This thesis provides three solutions for the objective of controllable distance of the Center of Mass traveled: constant spring stiffness, variable spring stiffness and variable wheel speed. The model in this thesis is flexible biped robot with wheeled, which combines the benefits of legged robot and wheeled robot. At the meanwhile, the wheel provides another way to control/increase the distance of center of mass (C.O.M) traversed in the direction of moving. The thesis deduced the formula of position, speed and acceleration of C.O.M in analytical way based on the inverted pendulum model. By experiment in MATLAB/Simscape, the thesis explanate the necessary of introduction of flexible element.