Geometric control for highly accurate construction machine guidance

Research

Exploration of control circuits for machine control under geodesic aspects.

Aims:

General research of control circuits for machine control under geodesic aspects.
Design of the control loops for optimal integration of target-tracking tachymeters as position sensors.
Investigation of geometric management tasks in the accuracy range of a few millimeters.
For the three-dimensional guidance of modern construction machinery, such. As slipform pavers, Gräder, or Dozer be tracking tachymeter or GPS-RTK used. This applies, in addition to other sensors, such. As tilt sensors to integrate as position-determining sensors in the control loops for machine control.

For high-precision management tasks in the range of a few millimeters, only tachymeters can be used due to the measuring accuracy. But since even the most modern target-tracking tachymeters are not very suitable for a scheme per se because of their relatively low sampling rate of up to 10 Hz and a dead time of up to several hundred milliseconds, only very slowly moving machines can be geometrically guided with high accuracy.

The described dynamic behavior of target-tracking tachymeters causes the current position of the machine to be determined too late in curves - larger deviations from the desired trajectory must be compensated by the control.
Figure 1: Closed-loop system with anticipatory precontrol
Closed-loop system with anticipatory precontrol

If the human control behaviour in case of manual machine control is analysed, unfavourable dynamic characteristics similar to a tracking tachymeter can be realized. A human is able to integrate the future track of the desired trajectory into his manual control behaviour – he anticipates. Hence a precontrol is established, that leaves only small deviations for recontrol. Figure 1 schematically shows a closed-loop system with anticipatory precontrol.

This theoretical knowledge is to be realized experimentally and later in practice and its potential is to be investigated.

Experiment with model truck:

Experimental realization is effected with the model truck (scale 1:14), show in picture 2. The truck is automatically guided on a predetermined trajectory. A tachymeter (Leica TCP 1201) is integrated into the closed-loop system. The deviations should not exceed 5 mm. The mentioned control concept with anticipatory precontrol is realized in LabView®. A detailed experiment description can be found in (Gläser 2003).

Modell-Lkw als Simulator (Quelle: iigs)

Erste Ergebnisse:

First results:

Figure 3 shows as a first result the deviation of the model truck to a reference trajectory. The deviations of automatic control with and without precontrol are compared. The speed was increased to 20cm/s, contrary to the speed of 1-2 cm/s used in practice (e.g. slip-form pavers). It can easily be recognized that the anticipatory precontrol increases the quality of automatic guidance considerable, and the aim of a maximum deviation of 5 mm can be reached despite a speed of 20 cm/s.

Deviation of the truck to the given trajectory
Photo: Deviation of the truck to the given trajectory

Publications:

  • Beetz, A., Schwieger, V.: (2008) Integration of Controllers and Filter Algorithms for Construction Machine Guidance. 1st International Conference on Machine Control and Guidance, Zürich, Schweiz, 24.-26-06.2008.
  • Schwieger, V., Beetz, A.: (2007) Optimierung von Regelalgorithmen zur Baumaschinensteuerung am Beispiel eines Simulators. Beiträge zum 15. Internationalen Ingenieurvermessungskurs, Graz, Herbert Wichmann Verlag, Heidelberg, 17.20.04.2007.
  • Gläser, A.(2005): A Modular System for Guidance and Control Applications for Construction Machines. In: Grün, Kahmen (Eds.): 7th Conference on Optical 3-D Measurement Techniques, Volume I, pp. 307-316, Vienna. (Kurzfassung)
  • Gläser, A., Schollmeyer, R. (2004): Messwerterfassung und –synchronisation in Multisensorsystemen. In: Beiträge zum 58. DVW-Seminar, Kinematische Messmethoden – Vermessung in Bewegung, Wißner Verlag, Augsburg.
  • Gläser, A. (2003): Steuerung autonomer Baumaschinen - Ein Simulator. In: Virtuelle Instrumente in der Praxis, National Instruments-VIP2003, Hüthig Verlag, München.

Diploma Thesis:

 
  • Beetz, A. (2003): Entwicklung ausgewählter Komponenten eines Regelkreises zur Fahrzeugsteuerung und deren Realisierung in einem Testsystem. Diplomarbeit am IAGB, unveröffentlicht.
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