When the moving piece goes forward, the upper body part
and the thigh part can risen up and lowered down, respectively.
L4 , L5 , and L6 denote the length of the bottom part, the length
of the linkage attached to the upper body part, and the length of
the linkage attached to the shank part, respectively. R3 and R4
denote the radii of the circle centered at K and L, respectively.
LnH and Lnf denote the vertical and horizontal distances between
K and M, respectively. Lnp denotes the distance between
N and M. The angles θn1r and θn3r are the rotated angles of
the upper body part and the thigh part, respectively. The relation
between Lnp and θn1r can be represented as follows