Apparatus and method for determining position of drilling tool during drilling

Abstract

An apparatus and method of determining the position of a drilling tool during drilling is provided. The apparatus includes a magnetic source mounted to a rotating drilling tool and at least two magnetometers, which are located outside a drilled hole. Sensing data of a rotating magnetic field is transmitted from the magnetometers to a control unit provided with a position calculation algorithm. The control unit is also provided with position data of the magnetometers and a reference position of the drilling tool. The control unit compares the received sensing data when the drilling tool is in the reference position and when being moved to a new position. Phase angles are then detected from the sensing data. The algorithm utilizes the phase angles and the known positions of the magnetometers and the reference point when calculating the changed position.

1 . An apparatus for detecting change of position of a drilling tool of a rock drilling rig during drilling when the drilling tool is rotated around its longitudinal drilling axis, the apparatus comprising:
 at least one magnetic source mounted to the rotatable drilling tool and configured to generate rotating magnetic field, and wherein a direction of axis of the rotating magnetic field deviates from the drilling axis;   at least two magnetometers configured to sense the rotating magnetic field generated by the magnetic source;   at least one control unit configured to receive sensing data from the magnetometers and being configured to examine the rotating magnetic field; and   at least a first magnetometer and a second magnetometer, which are both located external relative to the drilling tool, wherein the control unit is provided with data on position and orientation of the magnetometers, the control unit being provided with reference data including first reference sensing data of the first magnetometer, and second reference sensing data of the second magnetometer, when the magnetic source is located at a known reference position, and wherein the control unit is configured to compare first sensing data of the first magnetometer to the first reference sensing data for detecting a first phase angle between them, and correspondingly, to compare second sensing data of the second magnetometer to the second reference sensing data for detecting a second phase angle, and the control unit being configured to calculate a position change of the magnetic source relative to the known reference position in response to the detected phase angles and the known position of the magnetometers.   
     
     
         2 . The apparatus as claimed in  claim 1 , wherein the control unit is configured to examine the received sensing data by determining maximum strengths of the received magnetic field values and to determine a corresponding rotation angle of the magnetic source relative to the examined magnetometer, and the control unit being configured to determine the phase angles between the reference sensing data and any new sensing data by comparing the determined rotation angles of the detected maximum strength values. 
     
     
         3 . The apparatus as claimed in  claim 1 , wherein the magnetometers are located on a rock surface surrounding the drill hole being drilled. 
     
     
         4 . The apparatus as claimed in  claim 1 , wherein the control unit is provided with data on an advanced distance of the magnetic source inside the drilled hole, the control unit being configured to calculate three dimensional position data on the magnetic source in response to the detected position and the received data on the advance distance. 
     
     
         5 . The apparatus as claimed in  claim 1 , wherein the control unit is provided with sensing data from the magnetometers at several measuring points locating at different advance distances of the magnetic source inside the drilled hole, the control unit being configured to compare the calculated position data of the several measuring points and is configured to determine bending of the drilling tool in response to detected deviations in the position data. 
     
     
         6 . The apparatus as claimed in any  claim 1 , wherein the control unit is provided with data on coordinates of the magnetometers and the reference position in a work site coordinate systems, the control unit being configured to calculate coordinates of the magnetic source in the work site coordinate system. 
     
     
         7 . The apparatus as claimed in  claim 1 , wherein the control unit is configured to calculate position of a face surface of the drilling tool in response to input position data of the magnetic source relative to the face surface, whereby the position of the drilling tool is examined as the position of the face surface. 
     
     
         8 . The apparatus as claimed in  claim 1 , wherein the control unit is provided with a processor configured to execute a position detection algorithm the execution of which is configured to calculate the position of the magnetic source in response to the received sensing data of the magnetometers and the input reference data and position data. 
     
     
         9 . The apparatus as claimed in  claim 1 , wherein the control unit is configured to execute the position determination without comparing strength of the detected magnetic fields. 
     
     
         10 . The apparatus as claimed in  claim 1 , wherein the magnetic source is a permanent magnet. 
     
     
         11 . The apparatus as claimed in  claim 1 , wherein the magnetic source is mounted to a drill bit located at a distal end of the drilling tool. 
     
     
         12 . A rock drilling rig, comprising:
 a movable carrier;   at least one drilling boom connected movably to the carrier and equipped with a rock drilling unit, wherein the rock drilling unit includes a feed beam and a rock drilling machine supported movably on the feed beam; and at least one apparatus according to  claim 1  for determining a position of the drilling tool connectable to the drilling unit; and wherein the apparatus is in accordance with the previous  claims 1 - 11 .   
     
     
         13 . A method of determining position of a drilling tool of a rock drilling rig during drilling operation, the method comprising:
 rotating the drilling tool around its longitudinal drilling axis during the drilling and feeding the drilling tool axially forward in an advance direction;   detecting a change of position of the drilling tool during the drilling by means of an apparatus having at least one magnetic source mounted to the rotating drilling tool and at least two magnetometers;   generating a rotating magnetic field by rotating the magnetic source together with the drilling tool);   sensing the rotating magnetic field by means of the magnetometers and producing sensing data;   generating reference data by rotating the drilling tool at a known reference position and detecting a first reference sensing data by means of a first magnetometer and a second reference sensing data by means of a second magnetometer;   comparing first sensing data of the first magnetometer to the first reference sensing data and detecting a first phase angle therebetween and correspondingly, comparing second sensing data of the second magnetometer to the second reference sensing data and detecting a second phase angle; and   calculating a changed position of the magnetic source relative to the reference position on the basis of the detected phase angles and the position data of the magnetometers and the reference position.   
     
     
         14 . The method as claimed in  claim 13 , further comprising:
 sensing an advanced distance of the magnetic source inside the drilled hole during the drilling;   repeating the position measurement at several measuring points having different depths in the drill hole; and   comparing the calculated positions of the drilling tool at the several measuring points and determining straightness of the drill hole in response to the comparison.   
     
     
         15 . A computer program product having program code means configured to execute the method of  claim 13  when executed by a computer or a data processing device.