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G. Retscher, U. Egbonu:
"3-D Blade Guidance and Control Systems for Construction Machines";
Talk: Symposium on Geodesy for Geotechnical and Structural Engineering, Berlin; 2002-05-21 - 2002-05-24; in: "Geodesy for Geotechnical and Structural Engineering II", Berlin (2002), ISBN: 3-9501492-1-x; 539 - 540.

In recent years new developments for the construction industry have led to an increase in productivity of construction works and corresponding cost savings. Whether the given application is in general construction, earthmoving or civil engineering, nowadays advanced surveying techniques using lasers, total stations and GPS positioning solutions and software are available that can provide more control over the job task and site. For site preparation, powerful software for design and estimating takeoff as well as a complete line of machine control systems for the smallest skid steer to the largest bulldozer can be employed. Thereby modern machine control systems use a variety of technologies, either in combination or alone, including laser, GPS systems, total station, sonic or laser tracers and software. Using advanced machine control systems operators have the information they need in the cab, allowing them to significantly increase productivity, reduce material overages and work with greater precision.

For road and railway construction using dozers and graders, modern 3-D guidance and control systems consists usually of RTK GPS systems or total stations with automatic targeting and tracking for absolute position determination and additional sensors to measure attitude parameters (i.e., heading, pitch and roll) of the machine and/or its blade. The main system are either a GPS rover antenna of the RTK system or a remote target of the total station is mounted above the machine baldes. Electronic inclinometers (or tiltmeters) are employed to measure the longitudinal and transversal tilt (i.e., pitch and roll) and a longitudinal sensor (so-called long slope sensor) to measure the vehicle pitches in the direction of travel and hub for all system sensors. In addition, a precise determination of blade rotation using a so-called rotation compensator provides for optimum lateral inclination compensation. All the sensors are integrated as a component of the multi-sensor system.

To guide the machine blades along the designed alignment, the position and orientation of the blades in a 3-D coordinate system (e.g. the coordinate system of the construction site) has to be determined in real-time. The task can be solved if a coordinate frame, i.e., the so-called body frame, is used that has its origin embedded in the rotation point or centre of gravity of the machine blade. Then the heading and rotation of the blades in 3-D space are described by three attitude parameters of the body frame in respective to the coordinate frame of the construction site. They can be measured directly with the sensors of the employed multi-sensor system. The deviations from the designed surface are estimated in real-time together with the movements of the blades using a kinematic approach based on a Kalman filter.