METHOD AND APPARATUS FOR ACCURATELY POSITIONING A TOOL ON A MOBILE MACHINE USING ON-BOARD POSITIONING SYSTEM AND OFF-BOARD ADJUSTABLE LASER REFERENCE

摘要

A method and apparatus for accurately positioning a tool on a mobile machine are provided. The machine operates within a work area about which one or more stationary laser-based subsystems are positioned. The machine includes an on-board subsystem, which comprises a processor, a satellite positioning system (SPS) receiver, a stored digital terrain model (DTM), and a photosensor for detecting a laser beam. The laser beam provides a reference level that is used to adjust the position of the tool. The on-board subsystem determines the current position of the machine using the SPS receiver and accesses the DTM to determine a design elevation corresponding to the current location of the machine. Based on the design elevation, the on-board subsystem computes a height command and transmits the height command to at least one of the laser-based subsystems. Each stationary subsystem includes a vertically telescoping mast on which a laser is mounted, a servo mechanism for raising or lowering the mast, and a receiver for receiving a height command from the on-board subsystem in the machine. The stationary subsystem raises or lowers the mast to adjust the elevation of the laser beam according to the height command.