Caterpillar has expanded its autonomous solutions portfolio to its PM series of cold planers (milling machines), integrating 3D machine control directly into the rotor and steering systems. Traditionally, milling operations rely on physical string lines set by surveyors to guide the machine's depth and slope. This manual process is labor-intensive and prone to errors if the machine operator loses sight of the line or if the line is disturbed by site traffic.
The new Cat Grade Control for Millers utilizes a total station or GNSS base station to create a digital design surface of the road. The milling machine is equipped with sensors on the front and rear of the track frames, as well as on the rotor housing. As the machine advances, the system automatically adjusts the hydraulic cylinders controlling the drum depth to precisely match the digital design profile.
A critical engineering feature is the "stitching" capability. When the planer approaches a manhole cover or utility casting, the system automatically raises the drum slightly to pass over the obstacle without damaging it, then instantly lowers the drum back to the precise grade on the other side. This eliminates the manual process of "ramping" over castings, which traditionally leaves bumps in the road surface.
During a recent highway rehabilitation project, the autonomous planer achieved a vertical tolerance of ± 5 millimeters over a 5-kilometer stretch without a single string line stake. This level of precision ensures that the new asphalt overlay sits perfectly flush with existing manholes and curbs, drastically reducing the need for costly rework and grinding.
