The invention relates to mobile offshore jack-up structures and provides
for a self-regulating jacking system for elevating and lowering of the
legs and the hull. A central controller assembly regulates movement of
each of the legs, depending on the relative speed of movement of each leg
and inclination of the hull along two independent axes: forward-aft and
starboard-port. Each chord of the supporting legs is inverter driven to
ensure a bi-directional full rated torque control of the associated
pinion assemblies at very low speeds. By regulating the relative speed of
the leg vertical movement, the system monitors the hull inclination
within allowable limits and prevents an excessive differential vertical
travel of any of the leg chords, thereby minimizing a possibility of leg
bending or jamming of the screw jacks of the jacking assemblies 30.