Road structure – process – or apparatus – Apparatus – Automatic control
Patent
1996-06-12
1998-03-17
Graysay, Tamara L.
Road structure, process, or apparatus
Apparatus
Automatic control
404 8405, 404122, 73 1212, 73594, 364508, E01C 2307, E01C 1926, G01M 700
Patent
active
057279004
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention concerns methods and devices for automatic control of a compacting machine and for measurement or determination of characteristic mechanical quantities of a "ground" material or segment, the term ground here denoting a surface layer to be compacted, located underneath the compactor, directly from vibratory data measured in a vibrating compacting roller passing over the ground, where the control advantageously can use this measurement or determination.
BACKGROUND OF THE INVENTION
When compacting a ground material using a vibrating compacting machine it is advantageous if an automatic system is built into the compacting machine, the system being able to adjust parameters of the machine such as frequency, amplitude and rolling velocity to the varying conditions of the ground, so that a homogenous compaction of the ground is achieved in the shortest possible time. Such a control should then be performed in such a way that the machine, to the highest possible extent, at all times and at all possible grounds is able to produce a maximum transfer to the ground of energy effective in the compacting work. It is previously known that a vibrating roller rolling over a granular material results in a compression or a compaction in a zone below the contact area between the roller and the ground material whereas at least close to the surface both in front of and behind this zone a decompaction of the material is achieved. The compaction work on each small area segment will therefore comprise a sequence of decompaction, compression or compaction and decompaction for each pass. It is therefore essential to speak in terms of effective compaction energy and not only of the total performed compaction work.
During the compacting work, besides a high compaction effect, a result which is as homogenous as possible is desired, i.e. that the ground material gets an even carrying capacity.
From the U.S. Pat. No. 4,103,554 it is previously known to determine the degree of compaction of a ground material as a function of the amplitude of the compacting cylinder. This amplitude is measured at the ground frequency and at harmonic overtone frequencies and a comparison of the measured frequencies provides a measure of the degree of compaction of the ground. The result of this comparison can be used as a control signal in an automatic control system for the compaction, such as for setting the vibration frequency, the vibration amplitude, etc.
From the International Patent Application WO-A1 82/01905 another method is previously known for measuring the degree of compaction of a ground material using a vibratory apparatus.
In the published German patent application DE-A1 33 08 476 a method for controlling the amplitude of vibrating cylinders is disclosed. The control does not use any estimate of the degree of compaction but merely monitors that the movement of the vibratory roller is sufficiently regular by using signals from two sensors, one at each end of the compacting cylinder.
In a Ph.D dissertation, Grabe, Karlsruhe 1992, a simulation program for vibratory machines is presented, which uses different mechanical parameters for a ground material to be compacted. A method is here also outlined for numerically solving the inverse problem, i.e. for calculating from the signals detected by the machine, the mechanical parameters of the ground, generally a soil material. A concrete method is however not disclosed but a principal discussion is presented, intended to serve as a basis for the future work aiming at automatically controlled rollers.
In the Swedish patent application SE-A 9300776-3, "Optimal control of a compacting machine" ("Optimal styrning av valt"), filed Mar. 8, 1993, a method for controlling a vibrating roller machine in an efficient manner is described. The amplitude and frequency of the vibration and possibly other quantities of the roller machine are controlled so that the resulting vibration movement of the roller cylinder will comprise a predetermined and small proportion of
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Geodynamik H. Thurner AB
Graysay Tamara L.
Hartmann Gary S.
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