Automatic rear leg control for cold planers

A method of maintaining a cold planer substantially level to a first surface as the machine traverses a second surface and a third surface cut from the first surface, the cold planer including a front leg having a front leg length and a rear leg having a rear leg length, a frame supported by the front and rear legs, and a rotatable drum mounted on the frame between the front and rear legs, the front leg disposed on a first surface having a first grade, the method comprising:

• determining a desired second grade of the second surface;
• determining a desired third grade of the third surface;
• determining an electronic travel path based on the desired grade of the second surface and the desired grade of the third surface, the electronic travel path including a first point corresponding to a beginning of the second surface, a second point corresponding to a subsequent portion of the second surface, and a third point subsequent to the second point and corresponding to a portion of the third surface, the second point on the second surface at the desired second grade and the third point on the third surface at the desired third grade, wherein the first grade, the desired second grade, and the desired third grade are different and the first point is disposed directly adjacent to the first surface;
• determining a desired length change of the rear leg based on the electronic travel path, the desired length change of the rear leg being selected to maintain the frame substantially level to the first surface from the first point to the third point of the electronic travel path;
• advancing the machine with the tool operative to create the second and third surfaces;
• determining when the rear leg reaches the first point of the electronic travel path;
• adjusting an actual length of the rear leg based on the desired length change of the rear leg as the rear leg traverses the electronic travel path from the first point to the second point;
• determining when the rear leg reaches the second point of the electronic travel path;
• and
• adjusting the actual length of the rear leg based on the desired length change of the rear leg as the rear leg traverses the electronic travel path from the second point to the third point.

A machine for planing a road defining a first surface to form a second surface different from the first surface, the machine comprising:

• a frame;
• a plurality of ground engaging units,
• a plurality of vertically adjustable legs, each leg connecting one of the plurality of ground engaging units to the frame, the plurality of legs including at least one rear leg having a rear leg length and at least one front leg having a front leg length, the front leg disposed on the first surface;
• and
• a controller operably coupled to the ground engaging units and the plurality of vertically adjustable legs and configured to:
• determine a desired grade of the second surface;
• determine an electronic travel path based on the desired grade of the second surface, the electronic travel path including a first point corresponding to a beginning of the second surface and a second point corresponding to a subsequent portion of the second surface;
• determine a desired length change of the rear leg based on the electronic travel path, the desired length change of the rear leg being selected to maintain the frame substantially level to the first surface from the first point to the second point of the electronic travel path;
• advance the machine with the tool operative to create the second surface;
• determine when the rear leg reaches the first point of the electronic travel path;
• and
• adjust an actual length of the rear leg based on the desired length change of the rear leg as the rear leg traverses the electronic travel path from the first point to the second point.