Patent ID: 7438143

Claim:
A drilling machine, comprising: a frame, a tower supported by the frame and including a drill string, two tracks for movement over the ground, at least four yokes interconnecting the frame and the two tracks, each yoke pivotably connected to the frame and connected to one of the tracks, a plurality of hydraulic cylinders, each hydraulic cylinder being extendible and retractable in response to an associated control signal and connected to the frame and to an associated yoke, a plurality of sensors, each sensor sensing a parameter indicative of force and generating an output signal representing that force, and a controller that receives the output signals from the sensors, determines a center of gravity of the drilling machine with respect to a boundary area, and generates the control signals for the hydraulic cylinders based on the center of gravity, wherein each hydraulic cylinder is controlled to retract or extend to maintain the center of gravity within the predetermined boundary area.