Patent Publication Number: US-2023136108-A1

Title: A method performed by a control device for controlling the feeding distance and feeding rate in a rock drilling unit, a rock drilling unit and a rock drilling rig

Description:
TECHNICAL FIELD 
     The present disclosure relates to a method performed by a control device for controlling the feeding distance and feeding rate in a rock drilling unit, a rock drilling unit and a rock drilling rig. The present disclosure further relates to computer program and a computer-readable medium. 
     BACKGROUND ART 
     When performing drilling operations in rock-type materials generally special kinds of drilling rigs are used. There are different types of drilling rigs, wherein “DTH” (down the hole)-drilling rigs and top hammer drilling rigs are two commonly used rigs for drilling operations. The drilling rig may comprise a rock drilling unit. A feeding device may be arranged on the drilling unit. The feeding device may be configured for feeding a drill rod with a drill bit in an axial direction. As rock drilling is performed in hard materials special kinds of drill bits are used for such operations. The drill bits will however require maintenance in the form of replacement and/or re-grinding, which in turn leads to a need to remove and attach such drill bits to the drilling rig every now and then. For this reason, the feeding device may be configured for feeding the drill rod with and the drill bit in a forward and backward axial direction. 
     The rock drilling unit may be provided with a rod handling system, comprising a magazine of drill rods. The drill rods may be brought from the magazine by gripping elements during the boring operation for assembling a bore string with drill rods and thus make it possible to bore deeper into the rock. When changing drill bit, the drill rods are disassembled from each other and successively are brought back to the magazine by the gripping elements. 
     The feeding device may thus be configured for feeding the drill rod and the drill bit in an axial direction, both during the drilling operation and also during assembling of the bore string and changing of a drill bit. The feeding device may be axially driven in relation to the rock drilling unit and in the direction of the drill centre axis by means of a hydraulic or pneumatic actuator. 
     A distance sensor may be arranged in the hydraulic or pneumatic actuator for measuring the feeding distance of the drill rod and the drill bit in an axial direction. By means of the distance sensor the depth of the drill hole may be determined. 
     When the feeding device has reached one of its axial end positions, the actuator stops the axial movement of the feeding device. 
     SUMMARY OF THE INVENTION 
     Due to the above described properties and circumstances surrounding drilling operations in rock-type materials and handling of drill bits, the distance measuring arrangements used in rock drilling units are sensitive for aggressive environment connected to the performance of drilling operations in rock-type materials. In addition, the distance measuring arrangements used in rock drilling units are expensive to manufacture and also complicated to protect from the aggressive environment connected to the performance of drilling operations in rock-type materials. In addition to the feeding distance measuring, it would also be convenient to measure the axial feeding rate of the feeding device during drilling the bore. An optimal axial feeding rate of the feeding device, and thus also the drill bit in the axial direction will increase the bore hole quality and also save the drill bit from excessive load. In addition, depending on the configuration of the a rock drilling rig and the a rock drilling unit it would be convenient to arrange a distance and rate measurement device at a position, which has a low exposure for the aggressive environment. 
     There is thus a need for an improved method for measuring the feeding distance and feeding rate in a rock drilling unit. There is also a need to develop an improved control device configured to perform measurement of the feeding distance and feeding rate in a rock drilling unit. There is also a need to develop a rock drilling unit comprising such a control device, a rock drilling rig comprising such a rock drilling unit, a computer program and a computer-readable medium for executing the method. There is also a need to develop a rock drilling unit and a rock drilling rig, which may be autonomously controlled. 
     An object of the invention is thus to provide an improved method for measuring the feeding distance and feeding rate in a rock drilling unit. Additional objects are respectively to develop a rock drilling unit, a rock drilling rig comprising such a rock drilling unit, a computer program and a computer-readable medium for executing the method. A further object is to develop a rock drilling unit and a rock drilling rig, which may be autonomously controlled. 
     These objects are achieved by a method performed by a control device for controlling the feeding distance and feeding rate in a rock drilling unit, a rock drilling unit and a rock drilling rig. These objects are also achieved by a computer program and a computer-readable medium according to the appended claims. 
     According to an aspect of the invention, a method performed by a control device for controlling the feeding distance and feeding rate in a rock drilling unit is provided, the rock drilling unit comprising: a feeding device for feeding at least one drill rod and a drill bit in an axial direction; a rotating device, which is configured to generate a rotational movement of the at least one drill rod and the drill bit; and a distance and rate measuring device comprising at least one rotational target wheel configured to be driven by the feeding device and at least one sensor device connected to the control device, which sensor device is configured to sensing the rotating motion of the at least one rotational target wheel; the method comprising: controlling the feeding device to move in the axial direction; determining the feeding distance from a first position and the feeding rate of the feeding device from the rotational motion of the at least one rotational target wheel; and controlling the feeding device depending on the determined feeding distance and feeding rate of the feeding device. 
     This has the advantage that the control device may control the feeding distance and feeding rate of the feeding device based on the determined feeding distance and feeding rate of the feeding device. The instructions from the control device may be based on information received from the at least one sensor device connected to the control device. The control device may be configured to initiate the movement in the axial direction of the feeding device. The axial movement of the feeding device will generate a rotational motion of the at least one rotational target wheel. The sensor device senses the rotating motion of the at least one rotational target wheel. The sensor device also senses if the at least one rotational target wheel rotates or stands still. If there is no rotational motion of the rotational target wheel, there is no axial motion of the feeding device. The feeding distance from a first position and the feeding rate of the feeding device is determined from the rotational motion of the at least one rotational target wheel. The first position of the feeding device may be a predetermined position, a position wherein the drill bit resting on the surface of a rock to be drilled and/or a position, which depends on a specific drilling operation. The method also provides for a flexibility of arranging the rotational target wheel at different positions on the rock drilling rig and/or the rock drilling unit, which positions have low exposure for the aggressive environment. The controlling of the feeding distance and feeding rate of the feeding device may be initiated automatically during a drilling operation, an addition of drilling rods to the drill string and/or at a drill bit changing operation. The controlling of the feeding distance and feeding rate of the feeding device may also be initiated automatically during any other operation related to the rock drilling rig and/or the rock drilling unit, such as an maintenance operation. 
     According to an aspect of the invention, a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method. A computer-readable medium comprising instructions, which when executed by a computer, cause the computer to carry out the method. This has the advantage that the method may be comprised in pre-programmed software, which may be implemented into the drilling unit suitable for utilizing the method. 
     According to an aspect of the invention, a rock drilling unit is provided. The rock drilling unit comprises: a control device; a feeding device for feeding at least one drill rod and a drill bit in an axial direction; a rotating device, which is configured to generate a rotational movement of the at least one drill rod and the drill bit; and a distance and rate measuring device comprising at least one rotational target wheel configured to be driven by the feeding device and at least one sensor device connected to the control device, which sensor device is configured to sensing the rotating motion of the at least one rotational target wheel, wherein the control device being configured to: control the feeding device to move in the axial direction; determine the feeding distance from a first position and the feeding rate of the feeding device from the rotational motion of the at least one rotational target wheel; and control the feeding device depending on the determined feeding distance and feeding rate of the feeding device. 
     This has the advantage that the control device of the rock drilling unit may control the feeding distance and feeding rate of the feeding device based on the determined feeding distance and feeding rate of the feeding device. The instructions from the control device of the rock drilling unit may be based on information received from the at least one sensor device connected to the control device. In addition, the instructions from the control device may be based on experience data from earlier drilling operations. The control device may be configured to initiate the movement in the axial direction of the feeding device. The movement in the axial direction of the feeding device may be completely handled by means of instructions from the control device. The axial movement of the feeding device will generate a rotational motion of the at least one rotational target wheel. The sensor device senses the rotating motion of the at least one rotational target wheel. The sensor device also senses if the at least one rotational target wheel rotates or stands still. If there is no rotational motion of the rotational target wheel, there is no axial motion of the feeding device. The feeding distance from a first position and the feeding rate of the feeding device is determined from the rotational motion of the at least one rotational target wheel. The first position of the feeding device may be a predetermined position, a position wherein the drill bit resting on the surface of a rock to be drilled and/or a position, which depends on a specific drilling operation. The rotational target wheel may be arranged at different positions on the rock drilling rig and/or the rock drilling unit, which positions have low exposure for the aggressive environment. The control device may be configured to control the feeding distance and feeding rate of the feeding device automatically during a drilling operation, an addition of drilling rods to the drill string and/or at a drill bit changing operation. The control device may also be configured to control the feeding distance and feeding rate of the feeding device automatically during any other operation related to the rock drilling rig and/or the rock drilling unit, such as an maintenance operation. 
     According to an aspect of the invention, a rock drilling rig is provided, which rock drilling rig comprises the rock drilling unit disclosed herein. Different types of drilling rigs may be used depending on demands for typical rock drilling. The rock drilling rig may be configured for vertical drilling or drilling in an angled direction. The rock drilling rig may be a top hammer drilling rig or a “DTH” (down the hole)-drilling rig, or any other drilling rig suitable for rock drilling. 
     Further objects, advantages and novel features of the present invention will become apparent to one skilled in the art from the following details, and also by putting the invention into practice. Whereas examples of the invention are described below, it should be noted that it is not restricted to the specific details described. Specialists having access to the teachings herein will recognise further applications, modifications and incorporations within other fields, which are within the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For fuller understanding of the present disclosure and further objects and advantages of it, the detailed description set out below should be read together with the accompanying drawings, in which the same reference notations denote similar items in the various figures, and in which: 
         FIG.  1    illustrates a view in perspective of a rock drilling rig according to an example; 
         FIG.  2    schematically illustrates a side view of a rock drilling unit according to an example; 
         FIGS.  3   a  and  3   b    illustrate side views of distance and rate measuring devices configured to be connected to a rock drilling unit according to different examples; 
         FIGS.  4   a - 4   c    illustrate side views of distance and rate measuring devices configured to be connected to a rock drilling unit according to different examples; 
         FIG.  5    shows a flowchart of a method according to an example; 
         FIG.  6    shows a flowchart of a method according to an example; and 
         FIG.  7    schematically illustrates a control device or computer according to an example. 
     
    
    
     DETAILED DESCRIPTION 
     The detailed description with reference to the examples depicted are to be viewed as examples comprising a combination of certain features, which features have been described in detail above. It is thus to be understood that additional examples may be achieved by combining other features into examples not depicted herein. The figures are to be viewed as examples and not mutually exclusive combinations. It should also be noted that all figures shown and described are schematically represented, wherein generic parts of machinery or similar is not depicted for the sake of simplicity. 
     According to an aspect of the present disclosure, a method performed by a control device for controlling the feeding distance and feeding rate in a rock drilling unit is provided, the rock drilling unit comprising: a feeding device for feeding at least one drill rod and a drill bit in an axial direction; a rotating device, which is configured to generate a rotational movement of the at least one drill rod and the drill bit; and a distance and rate measuring device comprising at least one rotational target wheel configured to be driven by the feeding device and at least one sensor device connected to the control device, which sensor device is configured to sensing the rotating motion of the at least one rotational target wheel; the method comprising: controlling the feeding device to move in the axial direction; determining the feeding distance from a first position and the feeding rate of the feeding device from the rotational motion of the at least one rotational target wheel; and controlling the feeding device depending on the determined feeding distance and feeding rate of the feeding device. 
     The control device may be arranged on the rock drilling unit or at a distance to the rock drilling unit. The control device connected to the sensor device and also to other sensors, which are arranged on the rock drilling unit or at components connected to the rock drilling unit. The sensor device may be configured to sense the rotating motion of the at least one rotational target wheel. However, other sensors may detect activities or characteristics of the rock drilling unit or of the components connected to the rock drilling unit. The control device may comprise a memory in which experience data may be stored. 
     The drill bit is adapted for rock drilling in hard materials. The drill bit may be designed and provided with a shape adapted to the boring operation to be performed. The drill bit may be provided with a thread, which is adapted to be connected to a corresponding thread on the drill rod to form a first threaded connection. 
     The rock drilling unit may comprise an elongated frame or beam, on which the first feeding device and the rotating device are arranged. The rock drilling unit may be arranged on and connected to a vehicle by means of a boom, so that the rock drilling unit can be arranged in different positions in relation to the vehicle and to the rock to be drilled. Together, the rock drilling unit, the boom and the vehicle form a rock drilling rig. The drilling unit may be configured for vertical drilling, or in a direction deviating from the vertical direction. The drilling unit may thus be able to be tilted and drill at an angled direction relative a vertical line. 
     The feeding device is configured for feeding the drill rod and the drill bit in an axial direction, both during the drilling operation and also during changing of a drill bit. The feeding device may be axially driven in relation to the rock drilling unit and in the direction of the drill centre axis by means of a hydraulic or pneumatic actuator. 
     The rotating device, which is configured to generate a rotational movement of the drill rod and the drill bit may be driven by a first hydraulic or pneumatic machine. The rock drill unit may also be provided with an impact device for providing impact pulses on the at least one drill rod and the drill bit may be driven by a second hydraulic or pneumatic machine. The impact pulses will thus be provided on the drill rod in the direction of the drill centre axis and the impact pulses are transferred from the drill rod to the drill bit. 
     The distance and rate measuring device comprises at least one rotational target wheel configured to be driven by the feeding device. The distance and rate measuring device also comprises at least one sensor device connected to the control device. The sensor device is configured to sense the rotating motion of the at least one rotational target wheel. The sensor device may be arranged in close proximity to the rotational target wheel. The sensor device will generate a large number of electronic, magnetic or light pulses for each revolution of the rotational target wheel. In addition, a second rotational target wheel may be configured to be driven by the feeding device. The sensor device or a second sensor device may be configured to sense the rotating motion of the second rotational target wheel. Arranging two sensors sensor devices and two rotational target wheel provides two advantages. First, the direction in which the two rotational target wheel are rotating in will be known by which sensor device is triggered first. Second, a pulse will be generated by each sensor device, thereby doubling the number of pulses, which increases the accuracy of the measured distance and rate. 
     By the method step of controlling the feeding device to move in the axial direction, the control device may receive information from a memory in which operational data are stored. Alternatively or in combination, the control device may receive information from a device, which provides operational data. The operational data may be data comprising any one or a combination of a specific drilling operation, an addition of drilling rods to a drill string and/or at a drill bit changing operation. The control device may initiate controlling the feeding device to move in the axial direction automatically. The operational data may also be data comprising any one or a combination of: time spent drilling, time spent drilling since last maintenance, expected time left until change is needed, meters drilled, meters drilled since last maintenance, or other. 
     By the method step determining the feeding distance from a first position and the feeding rate of the feeding device from the rotational motion of the at least one rotational target wheel, the control device communicates with the sensor device and receives signals for determining the feeding distance and feeding rate. 
     By the method step controlling the feeding device depending on the determined feeding distance and feeding rate of the feeding device, the control device communicates with the feeding device and sends signals for controlling the feeding device. The feeding rate and feeding distance of the feeding device may be controlled depending on the determined feeding distance and feeding rate of the feeding device at the specific drilling operation, at the addition of drilling rods to a drill string and/or at the drill bit changing operation, or a combination of these. Other parameters, such as the length of the drill string and/or also on the depth of the drilled bore in the rock may be considered. The feeding rate and feeding distance of the feeding device may also be controlled depending on the type of drill bit. 
     Even though the feeding device is controlled to move in the axial direction in a first method step, the movement of the feeding device may result in a feeding distance and feeding rate, which deviate from the determined feeding distance and feeding rate in the next method step. Feedback of this deviation may be communicated to the control device, which results in the third method step of controlling the feeding device depending on the determined feeding distance and feeding rate of the feeding device. 
     Thus, the control device may be configured to initiate the movement in the axial direction of the feeding device. The axial movement of the feeding device will generate a rotational motion of the at least one rotational target wheel. The sensor device senses the rotating motion of the at least one rotational target wheel. The sensor device also senses if the at least one rotational target wheel rotates or stands still. If there is no rotational motion of the rotational target wheel, there is no axial motion of the feeding device. The feeding distance from a first position and the feeding rate of the feeding device is determined from the rotational motion of the at least one rotational target wheel. The first position of the feeding device may be a predetermined position, a position wherein the drill bit resting on the surface of a rock to be drilled and/or a position, which depends on a specific drilling operation. The method also provides for a flexibility of arranging the rotational target wheel at different positions on the rock drilling rig and/or the rock drilling unit, which positions have low exposure for the aggressive environment. The controlling of the feeding distance and feeding rate of the feeding device may be initiated automatically during a drilling operation, an addition of drilling rods to the drill string and/or at a drill bit changing operation. The controlling of the feeding distance and feeding rate of the feeding device may also be initiated automatically during any other operation related to the rock drilling rig and/or the rock drilling unit, such as an maintenance operation. 
     According to an aspect, the method comprises the further step of: determining the axial feeding direction of the feeding device based on the rotational direction of the at least one rotational target wheel. 
     In this method step, the sensor device of the distance and rate measuring device communicates with the control device and provides the control device with information about the rotational direction of the rotational target wheel. The axial movement of the feeding device will generate a rotational motion of the at least one rotational target wheel. The sensor device senses the rotating motion of the at least one rotational target wheel. In a first axial feeding direction of the feeding device the rotational target wheel will rotate in a first rotational direction. In a second axial feeding direction of the feeding device, opposite to the first axial feeding direction of the feeding device, the rotational target wheel will rotate in a second rotational direction, which is opposite to the first rotational direction. 
     According to an aspect, determining the feeding distance and feeding rate of the feeding device from the rotational motion of the at least one rotational target wheel comprises receiving at least one signal from the at least one sensor device. 
     In this method step, the sensor device of the distance and rate measuring device communicates with the control device and provides the control device with at least one signal. The sensor device is configured to sense the rotating motion of the at least one rotational target wheel. The sensor device may be arranged in close proximity to the rotational target wheel. The sensor device will generate a large number of electronic, magnetic and/or light pulses for each revolution of the rotational target wheel. The electronic, magnetic and/or light pulses generated by the sensor device are signals communicated to the control device. The at least one signal generated by the sensor device may correspond to the feeding distance and feeding rate of the feeding device. In addition, the at least one signal generated by the sensor device may correspond to the axial feeding direction of the feeding device. 
     According to an aspect, the method comprises the further steps of: resetting the feeding distance from the first position to zero at a predetermined position of the feeding device; and determining the feeding distance of the feeding device from the predetermined position of the feeding device from the rotational motion of the at least one rotational target wheel. 
     By this method step, the control device may receive information from the sensor device, at the feeding device is at a predetermined position. The predetermined position may be a position on the drilling unit, where the drill bit is resting on the surface of a rock to be drilled and/or a position, which depends on a specific drilling operation. At the predetermined position of the feeding device, the feeding distance from the first position is resetted to zero. The feeding distance may be determined from the predetermined position to a position at a distance from the predetermined position. 
     According to further steps, the method may comprise: determining a first and second end position for the feeding device; and controlling the feeding device to stop at the first and second end positions. The method may also comprise: adding a number of determined feeding distances to each other in order to achieve a total feeding distance. 
     The present disclosure also relates to a computer program comprising instructions which, when the program is executed by a computer, causes the computer to carry out the method disclosed above. The invention further relates to a computer-readable medium comprising instructions, which when executed by a computer causes the computer to carry out the method disclosed above. The method may be comprised in pre-programmed software, which may be implemented into the drilling unit suitable for utilizing the method. The pre-programmed software may be stored in the control device. Alternatively, or in combination, the software may be stored in a memory or in computer at a distance from the control device. 
     Furthermore, the present disclosure relates to a rock drilling unit, the rock drilling unit comprises: a control device; a feeding device for feeding at least one drill rod and a drill bit in an axial direction; a rotating device, which is configured to generate a rotational movement of the at least one drill rod and the drill bit; and a distance and rate measuring device comprising at least one rotational target wheel configured to be driven by the feeding device and at least one sensor device connected to the control device, which sensor device is configured to sensing the rotating motion of the at least one rotational target wheel, wherein the control device being configured to: control the feeding device to move in the axial direction; determine the feeding distance from a first position and the feeding rate of the feeding device from the rotational motion of the at least one rotational target wheel; and control the feeding device depending on the determined feeding distance and feeding rate of the feeding device. 
     The control device of the rock drilling unit may control the feeding distance and feeding rate of the feeding device based on the determined feeding distance and feeding rate of the feeding device. The instructions from the control device of the rock drilling unit may be based on information received from the at least one sensor device connected to the control device. In addition, the instructions from the control device may be based on experience data from earlier drilling operations. The control device may be configured to initiate the movement in the axial direction of the feeding device. The movement in the axial direction of the feeding device may be completely handled by means of instructions from the control device. The axial movement of the feeding device will generate a rotational motion of the at least one rotational target wheel. The sensor device senses the rotating motion of the at least one rotational target wheel. The sensor device also senses if the at least one rotational target wheel rotates or stands still. If there is no rotational motion of the rotational target wheel, there is no axial motion of the feeding device. The feeding distance from a first position and the feeding rate of the feeding device is determined from the rotational motion of the at least one rotational target wheel. The first position of the feeding device may be a predetermined position, a position wherein the drill bit resting on the surface of a rock to be drilled and/or a position, which depends on a specific drilling operation. The rotational target wheel may be arranged at different positions on the rock drilling rig and/or the rock drilling unit, which positions have low exposure for the aggressive environment. The control device may be configured to control the feeding distance and feeding rate of the feeding device automatically during a drilling operation, an addition of drilling rods to the drill string and/or at a drill bit changing operation. The control device may also be configured to control the feeding distance and feeding rate of the feeding device automatically during any other operation related to the rock drilling rig and/or the rock drilling unit, such as an maintenance operation. 
     It will be appreciated that all the examples described for the method aspect of the disclosure performed by the control device are also applicable to the rock drilling unit and the control device aspect of the disclosure. That is, the control device of the rock drilling unit may be configured to perform any one of the steps of the method according to the various examples described above. Thus, according to the following aspects, the control device of the rock drilling unit may be configured to perform the method steps according to the corresponding examples described above. 
     According to an aspect, the control device may thus be configured to determine the axial feeding direction of the feeding device based on the rotational direction of the at least one rotational target wheel. According to an aspect determine the feeding distance and feeding rate of the feeding device from the rotational motion of the at least one rotational target wheel comprises to receive a signal from the at least one sensor device. According to a further aspect, the control device may be configured to reset the feeding distance from the first position to zero at a predetermined position of the feeding device; and determine the feeding distance of the feeding device from the predetermined position of the feeding device from the rotational motion of the at least one rotational target wheel. 
     According to a further aspect, the at least one rotational target wheel is connected to a hose drum, which hose drum is rotatably driven by the motion of the feeding device. The feeding device may be axially driven in relation to the rock drilling unit and in the direction of the drill centre axis by means of a hydraulic or pneumatic actuator. Further, the rotating device, which is configured to generate a rotational movement of the drill rod and the drill bit may be driven by a first hydraulic or pneumatic machine. A possible impact device on the drilling unit for providing impact pulses on the at least one drill rod and the drill bit may be driven by a second hydraulic or pneumatic machine. The actuator and machines may be connected to hydraulic pump or a compressor by hoses arranged on the drilling unit or at a distance from the drilling unit. The hoses may be winded on a hose drum. During the feeding motion of the feeding device, the hoses may be unwinded from the hose drum or winded up on the hose drum depending on the feeding direction of the feeding device. When feeding the feeding device in first direction, which may be a direction from the hose drum, the hoses may be unwinded from the hose drum and the hose drum may rotate in a first rotational direction. When feeding the feeding device in a second direction, which may be a direction towards the hose drum, the hoses may be winded up on the hose drum and the hose drum may rotate in a second rotational direction. The feeding distance and feeding rate of the feeding device may be proportional to the rotational motion of the hose drum. The target wheel will follow the rotational motion and rotational direction of the hose drum. The target wheel may be arranged directly on a rotational axis of the hose drum. Alternatively, the target wheel may be arranged at distance from the hose drum, and connected to the hose drum by a transmission, such as a shaft or a belt. The transmission may have a gear ratio. According to example, if the transmission is connected to the rotational target wheel having a gear ratio of G:1, this means that there would be G x the number of pulses of the rotational target wheel for each rotation of the hose drum, making it possible to control the movement of the feeding device very accurately. Since the rotational motion of the hose drum is generated by the feeding device, the distance and rate measuring device comprising the at least one rotational target wheel may be configured to be driven by the feeding device. 
     According to a further aspect, the at least one rotational target wheel is connected to a drive shaft of a hydraulic motor, which hydraulic motor is configured to drive the feeding device. The feeding device may be axially driven in relation to the rock drilling unit and in the direction of the drill centre axis by means of a hydraulic motor. During the feeding motion of the feeding device, a drive shaft of the hydraulic motor will rotate in a first or second direction depending on the feeding direction of the feeding device. When feeding the feeding device in a first direction, the drive shaft of the hydraulic motor may rotate in a first rotational direction. When feeding the feeding device in a second direction, the drive shaft of the hydraulic motor may rotate in a second rotational direction. The feeding distance and feeding rate of the feeding device may be proportional to the rotational motion of the hose drum. The target wheel will follow the rotational motion and rotational direction of the drive shaft of the hydraulic motor. The target wheel may be arranged directly on drive shaft of the hydraulic motor. Alternatively, the target wheel may be arranged at distance from the hydraulic motor, and connected to the drive shaft of the hydraulic motor by a transmission, such as a shaft or a belt. The transmission may have a gear ratio. According to example, if the transmission is connected to the rotational target wheel having a gear ratio of G: 1 , this means that there would be G x the number of pulses of the rotational target wheel for each rotation of the drive shaft of the hydraulic motor, making it possible to control the movement of the feeding device very accurately. Since the rotational motion of the drive shaft of the hydraulic motor generates a motion of the feeding device, and the feeding device comprises the hydraulic motor, the distance and rate measuring device comprising the at least one rotational target wheel may be configured to be driven by the feeding device. 
     According to a further aspect, the at least one rotational target wheel is connected to an elongated frame or beam of the rock drilling unit or on the feeding device, which the at least one rotational target wheel is configured to be driven by the motion of the feeding device in relation to the elongated frame or beam. The feeding device may be axially driven in relation to an elongated frame or beam of the rock drilling unit and in the direction of the drill centre axis by means of an actuator, such as a hydraulic motor. During the feeding motion of the feeding device, a relative motion between the feeding device and the elongated frame or beam of the rock drilling unit will occur. The at least one rotational target wheel is driven by the relative motion between the feeding device and the elongated frame or beam of the rock drilling unit. The axial motion of the feeding device may be transferred to the at least one rotational target wheel by a transmission, such as a friction wheel which is rotatably arranged on the feeding device and resting at its periphery on the elongated frame or beam of the rock drilling unit. The rotational motion of the friction wheel may be transmitted from the friction wheel to the at least one rotational target wheel by a transmission, such as a shaft or a gearbox. Alternatively, the at least one rotational target wheel may be provided with a peripheral friction surface resting directly on the elongated frame or beam of the rock drilling unit. The feeding device may move in a first or second axial direction in relation to the elongated frame or beam of the rock drilling unit. When feeding the feeding device in an axial first direction, the at least one rotational target wheel may rotate in first rotational direction. When feeding the feeding device in an axial second direction, the at least one rotational target wheel may rotate in a second rotational direction. The feeding distance and feeding rate of the feeding device may be proportional to the rotational motion of the at least one rotational target wheel. The transmission connected to the at least one rotational target wheel may have a gear ratio. According to example, if the transmission is connected to the rotational target wheel having a gear ratio of G:1, this means that there would be G x the number of pulses of the rotational target wheel for each rotation of the drive shaft of the hydraulic motor, making it possible to control the movement of the feeding device very accurately. Since the rotational motion of the at least one rotational target wheel is generated by the motion of the feeding device, the distance and rate measuring device comprising the at least one rotational target wheel may be configured to be driven by the feeding device. 
     Furthermore, the present disclosure relates to a rock drilling rig comprising the rock drilling unit as disclosed herein. The rock drilling rig comprises the rock drilling unit as disclosed herein. In addition the rock drilling rig may also comprise a drilling platform, such as a vehicle. Connecting the rock drilling unit to a vehicle results in the rock drilling rig may easily be moved to different places and to different positions between drilling operations. The rock drilling unit may be arranged on and connected to a vehicle by means of a boom, so that the rock drilling unit can be arranged in different positions in relation to the vehicle and to the rock to be drilled. The rock drilling rig may be configured for vertical drilling or in an angled direction, relative a vertical line. 
     The drilling rig may comprise an interchangeable plurality of drill rods, wherein drill bits may be arranged at an end section of an end drill rod. The drill bit may be attached to the end section by means of a threaded connection. The rock drilling rig is configured for vertical drilling. However, the rock drilling rig may also be configured for drilling in a direction which deviates from vertical drilling. The drilling rig may be a top hammer drilling rig. This has the advantage that a commonly used drilling rig may be provided having a drill bit changer for at least semi-automatic changing of drill bits. The commonly used top hammer drilling rig may be provided with a reliable and safe system for changing the drill bits of said drilling rig. An efficient and reliable drilling rig is thus provided, which by means of the system arranged thereto provides a safe and convenient work environment due to not having the need to change drill bits manually. 
     The present invention will now be further illustrated with reference to the appended figures. 
       FIG.  1    shows a rock drilling rig  5  in a view of perspective according to an example. The rock drilling rig  5  comprises a rock drilling unit  8 , which may comprise an elongated frame or beam  2 . The rock drilling unit  8  may be arranged on and connected to a vehicle  6  by means of a boom  4 , so that the rock drilling unit  8  can be arranged in different positions in relation to the vehicle  6  and to the rock to be drilled. Together, the rock drilling unit  8 , the boom  4  and the vehicle  6  form the rock drilling rig  5 . The drilling rig  5  is configured for vertical drilling, which is to be perceived as completely vertical or deviating from vertical to some extent. The drilling rig  5  may comprise an interchangeable plurality of drill rods  7  ( FIG.  2   ), arranged to form a drill string within a rock drilling unit  8  of the drilling rig  5 . Each drill rod  7  comprises threads providing the option of connecting additional drill rods  7  as a drill bore  50  ( FIG.  2   ) being drilled gets deeper. A drill bit  3  is then arranged at an end section of an end drill rod  7 , wherein said drill bit  3  may be attached to the end section by means of a first threaded connection  40 . 
     The rock drilling rig  5  comprises a distance and rate measuring device comprising at least one rotational target wheel, which may be arranged at different positions on the rock drilling unit  8 . The drilling rig  5  may further comprise a support device  9 , such as a lower support device, which may be arranged at a lower portion of the rock drilling unit  8  and being arranged for supporting and/or holding/gripping a drill bit  3  or a drill rod  7 , which may be utilized for maintenance and/or assembly/disassembly or such parts. In addition, the support device  9  may guide the drill rod  7 . The drilling rig  5  shown in  FIG.  1    may further comprise a drill bit changer  1  for automatically or at least semi-automatic changing of drill bits  3 . The drilling unit  8  comprises a drill centre axis  15 . The term drill centre axis  15  may be perceived as a centre line in a drill bore  50  ( FIG.  2   ) being drilled by means of the drilling rig  5 . 
       FIG.  2    schematically illustrates a side view of a rock drilling unit  8  according to an example. The drill bit  3  is configured to be connected to a drill rod  7  by the first threaded connection  40 . The rock drilling unit  8  comprising a feeding device  42 , which is configured for feeding the at least one drill rod  7  and the drill bit  3  in an axial direction. A rotating device  44  is configured to generate a rotational movement of the at least one drill rod  7  and the drill bit  3 . An impact device  46  may be configured for providing impact pulses on the at least one drill rod  7  and the drill bit  3 . Such impact device  46  is not necessary, but may be useful depending on the type of drilling operation. The drill bit changer  1  is arranged on the rock drilling unit  8  for changing drill bits  3  on the drill rod  7 . The rotating device  44  and the impact device  44  are arranged on the first feeding device  42 . The rotating device  44  and the impact device  44  are configured to be displaced by means of the first feeding device  42 . The first feeding device  42  is arranged on elongated frame or beam  2 . The first feeding device  42  is configured for feeding the drill rod  7  and the drill bit  3  in an axial direction, both during the drilling operation and also during changing of a drill bit  3 . The first feeding device  42  may be axially driven in relation to the rock drilling unit  8  and in the direction of the drill centre axis  15  by means of a hydraulic or pneumatic actuator  10 . The hydraulic or pneumatic actuator  10  may be a hydraulic motor  10  provided with a drive shaft  17 . 
     The rotational target wheel  60  of the distance and rate measuring device  60 ,  62  is arranged on and driven by the feeding device  42 . The rotational target wheel  60  is in  FIG.  2    connected to the elongated frame or beam  2  of the rock drilling unit  8  or on the feeding device  42 . The rotational target wheel  60  is configured to be driven by the motion of the feeding device  42  in relation to the elongated frame or beam  2 . The rotational target wheel  60  may also or alternatively, as been disclosed in  FIG.  2   , be connected to a drive shaft  65  of the hydraulic motor  66 , which hydraulic motor  66  is configured to drive the feeding device  42 . At least one sensor device  62  is connected to the control device  100 , which sensor device  62  is configured to sense the rotating motion of the at least one rotational target wheel  60 . 
     The control device  100  is connected to the feeding device  42 , the rotating device  44 , the impact device  46  and to the drill bit changer  1 . The control device  100  may be connected to sensors  11 , which are arranged on the rock drilling unit  8  or at the components connected to the rock drilling unit  8 . The control device  100  may receive information from a memory  12  in which operational data are stored. 
     The control device  100  is configured to control the feeding device  42  to move in the axial direction; to determine the feeding distance from a first position and the feeding rate of the feeding device  42  from the rotational motion of the at least one rotational target wheel  60 ; and to control the feeding device  42  depending on the determined feeding distance and feeding rate of the feeding device  42 . Further the control device  100  being configured to determine the axial feeding direction of the feeding device  42  based on the rotational direction of the at least one rotational target wheel  60 . Determine the feeding distance and feeding rate of the feeding device  42  from the rotational motion of the at least one rotational target wheel  60  may comprise to receive at least one signal from the at least one sensor device  62 . Further, the control device  100  may also be configured to receive information about changing the drill bit  3  and to control the drill bit changer for changing and replacing the drill bit  3 . 
       FIG.  3   a    illustrates a side view of the distance and rate measuring device  60 ,  62  configured to be connected to the rock drilling unit  8  according to a first example. The sensor device  62  is configured to sense the rotating motion of the rotational target wheel  60 . The sensor device  62  may be arranged in close proximity to the rotational target wheel  60 . The sensor device  62  will generate a large number of electronic, magnetic or light pulses for each revolution of the rotational target wheel  60 . In the example shown in  FIG.  3   a    a number of magnets  64  are arranged on the periphery of the rotational target wheel  60 . 
       FIG.  3   b    illustrates a side view of the distance and rate measuring device  60 ,  62  configured to be connected to the rock drilling unit  8  according to a second example. A number of protrusions  66  and recesses  68  similar to a cogwheel are arranged on the periphery of the rotational target wheel  60 . Two sensor devices  62 ,  62 ′ may be arranged in close proximity to the rotational target wheel  60 . This will increase accuracy of the measured distance and rate. In addition, the rotational direction of the rotational target wheel  62  may be detected. 
     In addition, a second rotational target wheel  60 ′ may be configured to be driven by the feeding device  42 . The second rotational target wheel  60 ′ may be arranged at the same rotational shaft  70  as the first rotational target wheel  60 . The sensor device  62  and/or a second sensor device  62 ′ may be configured to sense the rotating motion of the second rotational target wheel  60 ′. Arranging two sensor devices  62 ,  62 ′ and two rotational target wheels  60 ,  60 ′ provides two advantages. First, the direction in which the two rotational target wheels  60 ,  60 ′ are rotating in will be known by which sensor device  62 ,  62 ′ is triggered first. Second, a pulse will be generated by each sensor device  62 ,  62 ′, thereby doubling the number of pulses, which increases the accuracy of the measured distance and rate. 
       FIG.  4   a    schematically illustrates a side view of distance and rate measuring device  60 ,  62  configured to be connected to a rock drilling unit  8  according to a first example. The rotational target wheel  60  is connected to a hose drum  72 , which hose drum  72  is rotatably driven by the motion of the feeding device  42 . The feeding device  42  may be axially driven in relation to the elongated frame or beam  2  of the rock drilling unit  8  and in the direction of the drill centre axis  15  by means of the hydraulic or pneumatic motor  10 . The motor  10  may be connected to hydraulic pump  74  or a compressor by hoses  76  arranged on the drilling unit  8  or at a distance from the drilling unit  8 . The hoses  76  may be winded on the hose drum  72 . During the feeding motion of the feeding device, the hoses  76  may be unwinded from the hose drum  72  or winded up on the hose drum  72  depending on the feeding direction of the feeding device  42 . When feeding the feeding device  42  in first direction, which may be a direction from the hose drum  72 , the hoses  76  may be unwinded from the hose drum  72  and the hose drum  72  may rotate in a first rotational direction. When feeding the feeding device in a second direction, which may be a direction towards the hose drum  72 , the hoses  76  may be winded up on the hose drum  72  and the hose drum  72  may rotate in a second rotational direction. The target wheel  60  will follow the rotational motion and rotational direction of the hose drum  72 . The target wheel  60  may be arranged directly on a rotational axis of the hose drum  72 . Alternatively, the target wheel  60  may be arranged at distance from the hose drum  72 , and connected to the hose drum  72  by a transmission  78 , such as a shaft or a belt. 
       FIG.  4   b    schematically illustrates a side view of distance and rate measuring device  60 ,  62  configured to be connected to a rock drilling unit  8  according to a second example. The rotational target wheel  60  is connected to a drive shaft  17  of a hydraulic motor  10 , which hydraulic motor  10  is configured to drive the feeding device  42 . The feeding device  42  may be axially driven in relation to the rock drilling unit  8  and in the direction of the drill centre axis  15  by means of the hydraulic motor  10 . The feeding distance and feeding rate of the feeding device  42  may be proportional to the rotational motion of the drive shaft  17 . The target wheel  60  will follow the rotational motion and rotational direction of the drive shaft  17  of the hydraulic motor  10 . The target wheel  60  may be arranged directly on drive shaft  17  of the hydraulic motor  10 . Alternatively, the target wheel  60  may be arranged at distance from the hydraulic motor  10 , and connected to the drive shaft  17  of the hydraulic motor  10  by a transmission  78 . 
       FIG.  4   c    schematically illustrates a side view of distance and rate measuring device  60 ,  62  configured to be connected to a rock drilling unit  8  according to a third example. The rotational target wheel  60  is connected to the elongated frame or beam  2  of the rock drilling unit  8  or on the feeding device  42 , which target wheel  60  is configured to be driven by the motion of the feeding device  42  in relation to the elongated frame or beam  2 . The feeding device  42  may be axially driven in relation to an elongated frame or beam  2  of the rock drilling unit  8  and in the direction of the drill centre axis  15  by means of an actuator, such as a hydraulic motor  10 . During the feeding motion of the feeding device  42 , a relative motion between the feeding device  42  and the elongated frame or beam  2  of the rock drilling unit  8  will occur. The at least one rotational target wheel  60  is driven by the relative motion between the feeding device  42  and the elongated frame or beam  2  of the rock drilling unit  8 . The axial motion of the feeding device  42  may be transferred to the at least one rotational target wheel  60  by a friction wheel  80  which is rotatably arranged on the feeding device  42  and resting at its periphery on the elongated frame or beam  2  of the rock drilling unit  8 . The rotational motion of the friction wheel  80  may be transmitted from the friction wheel  80  to the at least one rotational target wheel  60  by a transmission  78 , such as a shaft or a gearbox. Alternatively, the rotational target wheel  60  may be provided with a peripheral friction surface resting directly on the elongated frame or beam  2  of the rock drilling unit  8 . The feeding device  42  may move in a first or second axial direction in relation to the elongated frame or beam  2  of the rock drilling unit  42 . When feeding the feeding device  42  in an axial first direction, the at least one rotational target wheel  60  may rotate in first rotational direction. When feeding the feeding device  42  in an axial second direction, the at least one rotational target wheel  60  may rotate in a second rotational direction. The feeding distance and feeding rate of the feeding device  42  may be proportional to the rotational motion of the at least one rotational target wheel  60 . 
       FIG.  5    shows a flowchart of a method according to an example. The method is performed by a control device  100 , for controlling the feeding distance and feeding rate in a rock drilling unit  8 . The method thus relates to the controlling of the feeding distance and feeding rate in a rock drilling unit  8  disclosed in  FIGS.  1 - 4   . The rock drilling unit  8  comprising: a feeding device  42  for feeding at least one drill rod  7  and a drill bit  3  in an axial direction; a rotating device  44 , which is configured to generate a rotational movement of the at least one drill rod  7  and the drill bit  3 ; and a distance and rate measuring device  60 ,  62  comprising at least one rotational target wheel  60  configured to be driven by the feeding device  42  and at least one sensor device  62  connected to the control device  100 , which sensor device  62  is configured to sensing the rotating motion of the at least one rotational target wheel  60 . 
     The method comprising: controlling s 101  the feeding device  42  to move in the axial direction; determining s 102  the feeding distance from a first position and the feeding rate of the feeding device  42  from the rotational motion of the at least one rotational target wheel  60 ; and controlling s 103  the feeding device  42  depending on the determined feeding distance and feeding rate of the feeding device  42 . 
       FIG.  6    shows a flowchart of a method according to an example. The method is performed by a control device  100 , for controlling the feeding distance and feeding rate in a rock drilling unit  8 . The method thus relates to the controlling of the feeding distance and feeding rate in a rock drilling unit  8  disclosed in  FIGS.  1 - 4   . The method comprising: controlling s 101  the feeding device  42  to move in the axial direction; determining s 102  the feeding distance from a first position and the feeding rate of the feeding device  42  from the rotational motion of the at least one rotational target wheel  60 ; and controlling s 103  the feeding device  42  depending on the determined feeding distance and feeding rate of the feeding device. 
     The method comprises the further step of: determining s 104  the axial feeding direction of the feeding device  42  based on the rotational direction of the at least one rotational target wheel  60 . 
     Determining s 102  the feeding distance and feeding rate of the feeding device  42  from the rotational motion of the at least one rotational target wheel  60  comprises receiving at least one signal from the at least one sensor device  62 . 
     The method comprises the further steps of: resetting s 105  the feeding distance from the first position to zero at a predetermined position of the feeding device  42 ; and determining s 106  the feeding distance of the feeding device  42  from the predetermined position of the feeding device  42  from the rotational motion of the at least one rotational target wheel  60 . 
       FIG.  7    is a diagram of a version of a device  500 . The control device  100  described with reference to  FIG.  2    and  FIG.  3    may in a version comprise the device  500 . The device  500  comprises a non-volatile memory  520 , a data processing unit  510  and a read/write memory  550 . The non-volatile memory  520  has a first memory element  530  in which a computer programme, e.g. an operating system, is stored for controlling the function of the device  500 . The device  500  further comprises a bus controller, a serial communication port, I/O means, an A/D converter, a time and date input and transfer unit, an event counter and an interruption controller (not depicted). The non-volatile memory  520  has also a second memory element  540 . 
     There is provided a computer programme P which comprises routines for controlling the rock drilling rig  5 . The programme P may be stored in an executable form or in a compressed form in a memory  560  and/or in a read/write memory  550 . 
     Where the data processing unit  510  is described as performing a certain function, it means that the data processing unit  510  effects a certain part of the programme stored in the memory  560  or a certain part of the programme stored in the read/write memory  550 . 
     The data processing device  510  can communicate with a data port  599  via a data bus  515 . The non-volatile memory  520  is intended for communication with the data processing unit  510  via a data bus  512 . The separate memory  560  is intended to communicate with the data processing unit  510  via a data bus  511 . The read/write memory  550  is adapted to communicating with the data processing unit  510  via a data bus  514 . 
     When data are received on the data port  599 , they are stored temporarily in the second memory element  540 . When input data received have been temporarily stored, the data processing unit  510  is prepared to effect code execution as described above. 
     Parts of the methods herein described may be effected by the device  500  by means of the data processing unit  510  which runs the programme stored in the memory  560  or the read/write memory  550 . When the device  500  runs the programme, methods herein described are executed. 
     The foregoing description of the embodiments has been furnished for illustrative and descriptive purposes. It is not intended to be exhaustive, or to limit the embodiments to the variations described. Many modifications and variations will obviously be apparent to one skilled in the art. The embodiments have been chosen and described in order to best explicate principles and practical applications, and to thereby enable one skilled in the arts to understand the invention in terms of its various embodiments and with the various modifications that are applicable to its intended use. The components and features specified above may, within the framework of the disclosure, be combined between different embodiments specified.