Jumping Leg:
The model of the jumping robot is planar and is composed of four
segments which represent the foot, shank, thigh and trunk.
The segments are connected by frictionless rotational hinges whose axes
are perpendicular to the sagittal plane. The model consists of two parts,
the model of the robot in the air and the model of the robot in contact
with the ground. While the tip of the foot is on the ground, the contact
between the foot tip and the ground is modelled as a rotational hinge
joint between the foot tip and the ground at point F. Therefore, the
robot has six degrees of freedom during flight and four degrees of freedom
during stance (with the assumption that the foot tip of the robot does
not slip and does not bounce back). The generalized coordinates used
to describe the motion of the robot are coordinates xF and yF of the
foot tip measured in the reference frame and joint angles α, β, γ, δ.