Apparatus and method for determining position of drilling tool during drilling

Abstract

An apparatus and method of determining position of a drilling tool during drilling is disclosed. The apparatus includes a magnetic source mounted to a rotating drilling tool and at least three magnetometers, which are located outside a drilled hole. Sensing data of the rotating magnetic field is transmitted from the magnetometers to a control unit (CU) provided with a position calculation algorithm. The control unit is also provided with pose data of the magnetometers. The control unit compares the received sensing data and determines phase angles from the sensing data. The algorithm utilizes the phase angles and the known positions of the magnetometers when calculating the 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 direction of axis of the magnetic field deviates from the drilling axis;   at least one magnetometer configured to sense the magnetic field generated by the magnetic source; and   at least one control unit configured to receive sensing data from the magnetometers and is configured to examine the rotating magnetic field; and   at least three magnetometers, which are all located external relative to the drilling tool, wherein the control unit is provided with data on position and orientation of the magnetometers, wherein the control unit is configured to detect phase differences between the sensing data received from the magnetometers, determine phase angles between the magnetometers and the rotating magnetic source in response to the detected phase differences, and calculate data on a position of the magnetic source on the basis of the detected phase angles and the input positions and orientations of the magnetometers, and wherein the control unit is further provided with data on advanced distance of the magnetic source inside the drilled hole, the control unit being configured to calculate three dimensional position data of the drilling tool using the calculated data on position of the magnetic source and the data on the advance distance.   
     
     
         2 . The apparatus as claimed in  claim 1 , wherein the control unit is configured to implement triangulation in the position calculation of the magnetic source. 
     
     
         3 . 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 corresponding rotation angle of the magnetic source relative to the examined magnetometer; and the control unit is configured to determine the phase angles between the sensing data by comparing the determined rotation angles of the detected maximum strength values. 
     
     
         4 . The apparatus as claimed in  claim 1 , wherein the magnetometers are located on a rock surface surrounding the drill hole being drilled. 
     
     
         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, and the control unit is 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  claim 1 , wherein the control unit is provided with data on coordinates of the magnetometers in a work site coordinate system, and the control unit is 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 provided with a processor configured to execute a position detection algorithm, an 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 position data. 
     
     
         8 . 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. 
     
     
         9 . The apparatus as claimed in  claim 1 , wherein the magnetic source is a permanent magnet. 
     
     
         10 . The apparatus as claimed in  claim 1 , wherein the magnetic source is mounted to a drill bit locating at a distal end of the drilling tool. 
     
     
         11 . 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, the rock drilling unit including a feed beam and a rock drilling machine supported movably on the feed beam; and   at least one apparatus according to  claim 1  arranged to determine a position of the drilling tool connectable to the drilling unit.   
     
     
         12 . 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 drilling and feeding of the drilling tool axially forward in an advance direction;   detecting a 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 one magnetometer;   generating a rotating magnetic field by rotating the magnetic source together with the drilling tool;   sensing the rotating magnetic field by means of the at least one magnetometer and producing sensing data;   implementing at least three magnetometers in the sensing and generating at least three sensing data;   executing a comparison between the generated sensing data and determining phase differences and phase angles; and   calculating a position of the magnetic source relative to known poses of the magnetometers ( 12   a - 12   c ) on a basis of the determined phase angles, wherein a control unit is configured to receive the sensing data from the magnetometers and further provided with data on an advanced distance of the magnetic source inside the drilled hole; and   the control unit is configured to calculate three dimensional position data of the drilling tool using the calculated data on a position of the magnetic source and the data on the advance distance.   
     
     
         13 . The method as claimed in  claim 12 , 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.   
     
     
         14 . A computer program product comprising program code means configured to execute the method of  claim 12  when being run on a computer or a data processing device.