When is fixed to 0, this configuration has the same shape as in Figurea and therefore, it is very similar to PP configuration. It only can move on a straight line, forward and backward. The experimental results are shown in Figureb. The velocity of the movement increases with the amplitude and there is a phase window in which the coordination is better. For the same amplitude, the space roved is less than in PP configuration but the phase window is wider. As the distance between the outermost modules is greater than in PP configuration, it is most difficult for this two modules to carry out the locomotion. Therefore the is smaller.