Patent ID: 6132005
Filing Date: 2000-10-17
Classification: E21C,G01H,G01N

Abstract:
A method of detecting when picks of a cutting head of a machine for breaking up a compacted layer of material stray beyond the boundary of the layer, comprising:detecting in the vicinity of the head sets of predetermined air-borne sound frequencies corresponding to resonant frequencies of the picks of the cutting head,converting these sets of frequencies into electrical signals,filtering the electrical signals and applying correction factors to them in order to provide corrected signals corresponding to the respective amplitudes of a unique combination of frequencies making up each of the different sets, wherein the correction factors are related to physical dimensions of the picks and the nature of the material being broken up, andusing the relative changes of the corrected signal amplitudes to control the position of the head so that the amplitudes of the frequencies of the sets are restored to a predetermined relationship.