Given v0x, the corresponding vertical speed is determined by
adopting the conditions given by (11). From a practical point of
view, the landing time can be set to 20% longer than tmax.
The required vertical jumping speed is determined by combining
the two constraints. Once this is known, the corresponding
duty ratio needed for the solenoid valve to cause the pneumatic
cylinder rod to exert the desired force on the ground can be determined
from the pneumatic pressure, mass of the cylinder rod, and
mass of the robot body.