Method and a device for ascertaining the degree of compaction of a bed of material with a vibratory compacting device

Abstract

A device for ascertaining the degree of compaction of beds of material with a vibratory compaction device as a function of the vibratory amplitude of the motion of the compaction device at selected frequencies is described. The amplitude of vibratory motion of a compaction device is measured at a fundamental frequency and at least the second harmonic of the fundamental frequency and a ratio of the measured signals is computed. The ratio or quotient of the two signals provides a representation of the degree of compaction of the material being compressed by the compaction device. The ratio or quotient may be utilized either as a direct indication to an operator of the degree of compaction or as a control signal in an automated servo control compaction system.

It is claimed: 
     
       1. A method for measuring the degree of compaction achieved in a bed of material by a vibratory compaction device comprising the steps of: vibrating the compaction device against the bed of material to be compacted to generate a characteristic signal of the vibratory motion of the compacting device against said material, said characteristic vibratory motion signal having a fundamental frequency and a plurality of harmonic frequencies;   measuring the amplitude of said characteristic vibratory motion signal at said fundamental frequency;   measuring the amplitude of said characteristic vibratory motion signal for at least the second harmonic of said fundamental frequency; and   comparing the measured amplitudes of said fundamental frequency and said at least second harmonic frequency to ascertain the degree of compaction of said bed of material.   
     
     
       2. The method of claim 1, wherein said step of comparing comprises computing the quotient between the measured amplitude of said fundamental frequency and said second harmonic frequency. 
     
     
       3. The method of claim 1, comprising the further steps of: measuring the amplitude of the third harmonic of said characteristic signal of said vibratory motion;   weighting and adding the measured amplitudes of the second and third harmonic frequencies to provide a weighted sum thereof; and   comparing the weighted sum with the measured amplitude of the fundamental frequency to ascertain the degree of compaction of the bed of material.   
     
     
       4. The method of claim 3, wherein said characteristic signal of vibratory motion has both vertical and horizontal amplitude components with respect to said bed of material and only said vertical components are measured at said fundamental and harmonic frequencies. 
     
     
       5. The method of claim 3, wherein said characteristic signal of vibratory motion has both vertical and horizontal amplitude components and both said vertical and horizontal amplitude components at said fundamental and harmonic frequencies are measured for comparison. 
     
     
       6. A system for measuring the degree of compaction achieved in a bed of material by a vibratory compaction device comprising: means for vibrating the compaction device against the bed of material to be compacted;   transducer means for generating a characteristic signal of the vibratory motion of the compacting device against said material, said characteristic vibratory motion signal having a fundamental frequency and a plurality of harmonic frequencies;   first filter means for filtering said fundamental frequency from said characteristic frequency to obtain a fundamental amplitude signal;   means for measuring the amplitude of said fundamental amplitude signal;   second filter means for filtering at least one harmonic frequency component from said characteristic signal to obtain a harmonic frequency signal;   means for measuring the amplitude of said harmonic frequency signal; and   means for comparing the amplitudes of said fundamental and harmonic frequency signals to generate a signal representative of the degree of material compaction of said material.   
     
     
       7. The system of claim 6, wherein said means for comparing comprises divider means for determining the ratio between the amplitude of said fundamental frequency signal and the amplitude of said harmonic frequency signal. 
     
     
       8. The system of claim 6 further including: third filter means for filtering an additional harmonic component of said characteristic signal to obtain an additional harmonic frequency signal;   means for measuring the amplitude of said additional harmonic frequency signal;   means for adding the respective measured amplitudes of harmonic signals; and   means for comparing the amplitude of the fundamental signal to the sum of the amplitudes of the harmonic signals.   
     
     
       9. The system of claim 6 further including means for applying the signal from said means for comparing to said means for vibrating to control the degree of compaction. .Iadd. 10. A method for measuring the degree of compaction achieved in a bed of material by a vibratory roller of a compaction device comprising steps of: vibrating the vibratory roller of the compaction device such that said vibratory roller vibrates against the bed of material to be compacted to generate a characteristic signal of the vibratory motion of the vibratory roller against said material, said characteristic vibratory motion signal having a fundamental frequency and a plurality of harmonic frequencies;   measuring the amplitude of said characteristic vibratory motion signal at said fundamental frequency;   measuring the amplitude of said characteristic vibratory motion signal for at least the second harmonic of said fundamental frequency; and   comparing the measured amplitudes of said fundamental frequency and said at least second harmonic frequency to ascertain the degree of compaction of said bed of material. .Iaddend..Iadd. 11. The method of claim 10, wherein said step of comparing comprises computing the quotient between the measured amplitude of said fundamental frequency and said second harmonic frequency. .Iaddend..Iadd. 12. The method of claim 10, comprising the further steps of:   measuring the amplitude of the third harmonic of said characteristic signal and said vibratory motion;   weighting and adding the measuring amplitudes of the second and third harmonic frequencies to provide a weighted sum thereof; and   comparing the weighted sum with the measured amplitude of the fundamental frequency to ascertain the degree compaction of the bed of material. .Iaddend..Iadd. 13. The method of claim 12, wherein said characteristic signal of vibratory motion has both vertical and horizontal amplitude components with respect to said bed of material and only said vertical components are measured at said fundamental and harmonic frequencies. .Iaddend..Iadd. 14. The method of claim 12, wherein said characteristic signal of vibratory motion has both vertical and horizontal amplitude components and both said vertical and horizontal amplitude components at said fundamental and harmonic frequencies are measured for comparison. .Iaddend..Iadd. 15. A system for measuring the degree of compaction achieved in a bed of material by a vibratory compaction device comprising:   roller means;   means for vibrating said roller means for compaction device against the bed of material to be compacted;   transducer means for generating a characteristic signal of the vibratory motion of said roller means of the compacting device against said material, said characteristic vibratory motion signal having a fundamental frequency and a plurality of harmonic frequencies;   first filter means for filtering said fundamental frequency from said characteristic frequency to obtain a fundamental amplitude signal;   means for measuring the amplitude of said fundamental amplitude signal;   second filter means for filtering at least one harmonic frequency component from said characteristic signal to obtain a harmonic frequency signal;   means for measuring the amplitude of said harmonic frequency signal; and   means for comparing the amplitudes of said fundamental and harmonic frequency signals to generate a signal representative of the degree of material compaction of said material. .Iaddend..Iadd. 16. The system of claim 15, wherein said means for comparing comprises divider means for determining the ratio between the amplitude of said fundamental frequency signal and the amplitude of said harmonic frequency signal. .Iaddend..Iadd. 17. The system of claim 15, further including:   third filter means for filtering an additional harmonic component of said characteristic signal to obtain an additional harmonic frequency signal;   means for measuring the amplitude of said additional harmonic frequency signal;   means for adding the respective measured amplitude of harmonic signals; and   means for comparing the amplitude of the fundamental signal to the sum of the amplitudes of the harmonic signals. .Iaddend..Iadd. 18. The system of claim 15, further including means for applying the signal from said means for comparing to said means for vibrating to control the degree of compaction. .Iaddend.