A dozer blade control system controls the position of a bulldozer blade,
maintaining the blade at a constant position as the dozer travels through
a worksite. The control system monitors the angle of the dozer blade with
respect to the earth and when it senses that the dozer blade is tilting,
it corrects the dozer blade's position by extending or retracting
hydraulic cylinders that couple the dozer blade to the chassis of the
crawler-tractor. When the dozer chassis pitches forwards, the blade
begins to tilt forward and to drop closer to the ground. The control
system senses this forward rotation of the blade and retracts the
hydraulic cylinders that couple the blade to the chassis, causing the
blade to return to and maintain its original position. Conversely, when
the dozer chassis pitches backwards and the blade begins to tilt backward
and rise higher above the ground, the control system extends the
hydraulic cylinders coupling the blade to the chassis and lowers the
blade, causing the blade to return to and maintain its original position
with respect to the earth.