EP3775484B1

EP3775484B1 - A percussion device and a method for controlling a percussion mechanism of a percussion device

Info

Publication number: EP3775484B1
Application number: EP19775902.0A
Authority: EP
Inventors: Mahdi SAADATI; Mattias GÖTHBERG; Kenneth Weddfelt
Original assignee: Epiroc Rock Drills AB
Current assignee: Epiroc Rock Drills AB
Priority date: 2018-03-28
Filing date: 2019-03-26
Publication date: 2023-09-27
Anticipated expiration: 2039-03-26
Also published as: EP3775484C0; WO2019190381A1; EP3775484A1; SE542131C2; EP3775484A4; SE1850350A1

Description

FIELD OF THE INVENTION

The invention relates to the field of rock breaking or rock drilling.

BACKGROUND OF THE INVENTION

Rock drilling or rock breaking is today widely used in many industries, such as oil, gas, well drilling, mining, civil engineering etc. There are a number of different drilling techniques used, e.g. percussive drilling and rotary drilling. The choice of drilling technique depends on the specific application where the type of rock formation, depth and diameter of the drilling hole are of fundamental importance.
In percussive drilling a drill bit strikes the rock, creating fissures in the rock formation and breaking chips loose. After the strike, a rotary mechanism causes the drill bit to rotate, thereby achieving a varying impact distribution on the rock. During drilling a constant feed force may keep the drill bit in contact with the rock, providing maximal energy transfer. Finally, chips and loose rock material is flushed from the drill-hole by a flushing medium introduced to the bottom of the hole through flushing holes in the drill bit. The flushing medium can e.g. be water or air. This sequence of steps is then repeated. The striking force on the drill bit can be achieved in a number of different ways. According to the "Top Hammer" (TH) method, a piston inside the rock drill strikes a drilling rod, thus creating a compressive stress that travels through the rod to the bit. A percussion mechanism/hammer is arranged at the top of the drill string. Alternatively, in the so called "Down-The-Hole" (DTH) or "In-The-Hole" (ITH) methods, the piston strikes the drill bit directly, i.e. a percussion mechanism/hammer is located down in the hole, close to the bit. In the COPROD method impact rods are stacked inside a drill pipe or tube. The impact rods transfer the impact energy and feed force down the hole to the drill bit, while the pipe is used to transmit rotation.
Regardless of the technique used, the drilling equipment will often be exposed to very harsh conditions, resulting in high wear and tear. In addition, environmental considerations, inaccessibility of the work site and complex equipment drive up costs. Thus, it is desirable to increase drilling efficiency, thereby reducing cost and tool wear.
DE2541795 discloses a rotary-percussion drill where the frequency of the oscillatory motion in the axial direction of the drill bit can be constantly varied between an upper and a lower limit.
WO2013095164 discloses a drill arrangement with masses arranged as part of the impact device. These masses act as impedances and will decouple the drill bit from the drill string, i.e. the drill bit will oscillate at a different frequency than the drill string. The input strike is also broken into multiple frequencies where the larger amplitude vibrations cause the majority of the rock breaking while the higher frequencies assist in localized rock fracturing but also cause fluidization thereby minimizing "frictional grab" on the drill rods.
US7717190 discloses a percussion drill where the impact frequency of the percussion device is set proportional to the propagation time of the stress waves in the tool material in order to achieve a specific superposition of waves in the tool material for increased drilling efficiency.
SE1151155 discloses a percussion drill capable of varying the strike frequency. The impact power of the device is directly set by the strike frequency. Two modes are defined in the document; a first high-frequency mode and a second low-frequency mode.
EP0426928 discloses a percussion apparatus able to adapt the power and frequency of a percussion appliance to the hardness of the material where it works, the power of the tool being determined by the piston rebound velocity through the tools mechanical features.
EP2979818 discloses a hydraulic breaker system arranged with a sensor to detect vibrations generated when the chisel breaks rocks and capable of adapting the stroke of a piston so as to break the rock in an efficient manner, thereby avoiding idle blows and increasing the life span of the breaker.
US8353368 discloses a drilling apparatus with a drill bit capable of rotary and high frequency oscillatory loading having means for controlling the applied rotary and/or oscillatory loading based on the conditions of the material through which the drill is passing. According to a preferred embodiment a resonance between the drill bit and the material being drilled is maintained. To this end a frequency sweeping range is estimated in order to find the optimum resonant frequency.
WO2008/127172 A1 discloses a background art method and percussion device for controlling a percussion mechanism, wherein the basic principle involves controlling the percussion pressure as a function of the damping pressure. Other background art is found in WO03/033873 A1 , WO 2010/037905 A1 , WO99/47313 A1 , and US5174387 A .
The apparatuses according to the described prior art are either quite complex or not very flexible resulting in high cost and suboptimal drilling procedures. There is thus still a need for improvement in this technical field.

BRIEF DESCRIPTION OF EMBODIMENTS HEREIN

It is an object of embodiments herein to enhance the drilling performance in rock drilling applications with regards to energy expenditure and drilling efficiency, or at least to achieve an alternative to known solutions within the technical field.
The above-mentioned object is achieved by a method and percussion device as defined in the independent claims.
The percussion device comprises a percussion mechanism, percussion means and a drill bit. The percussion mechanism is adapted to provide the percussion means with a motion. The controller is arranged to control the percussion mechanism such that it imparts the percussion means with a force causing the motion, whereby the percussion means during drilling impacts the drill bit, or a drill string connected to the drill bit, with an impact force having a specific magnitude.
A method for controlling the percussion mechanism comprises, continuously during drilling, determining a desired magnitude of the impact force of the percussion means and controlling the percussion mechanism such that the impact force of the percussion means is changed according to the desired magnitude.
The controller is arranged to, continuously during drilling, determine a desired magnitude of the impact force of the percussion means and control the percussion mechanism such that the impact force of the percussion means is changed according to the desired magnitude.
By determining a desired magnitude of the impact force and controlling the percussion mechanism continuously during drilling such that the impact force of the percussion means on the drill bit or drill string connected to the drill bit is changed according to the desired magnitude, the impact force on the drill bit can be adapted, which may also be referred to as changed, as the drilling proceeds. As a consequence, the force with which the drill bit impacts the rock being drilled will be adapted continuously during drilling. This results in a more efficient drilling procedure since the impact force can be optimized for each strike. Thus, since the impact force is determined and adapted continuously there will be a reduction of strikes with a suboptimal impact force, such as e.g. an impact force higher than is needed to break the rock. The amount of energy expended on each impact will be then the amount needed to achieve an optimal drilling procedure through the bedrock. As a result, the drilling procedure will be more efficient and therefore require less energy. Less amount of power, e.g. hydraulic or electric power, will therefore be needed in order to achieve the same drilling rate. Furthermore, the average feed force will be reduced compared to ordinary drilling machines, which may overshoot in order to break the rock. A more optimized drilling procedure will furthermore lead to a decreased wear and tear of the tools since the force of the impacts need not be higher than is necessary to break the rock.
Consequently, a method and a device for enhanced drilling performance in rock drilling applications with regards to energy expenditure and drilling efficiency is provided.

BRIEF DESCRIPTION OF THE FIGURES

Further objects and advantages, as well as technical features of the invention will become apparent through the following description of one or several embodiments given with reference to the appended figures, where:

Fig. 1 is a schematic view of an exemplifying percussion device adapted for rock drilling,
Fig. 2 is a flow chart showing a method for controlling a percussion mechanism of a percussion device adapted for rock drilling.

DETAILED DESCRIPTION OF EMBODIMENTS HEREIN

The present invention is described in more detail below with reference to the appended figures, in which examples of embodiments are shown. The invention is not limited to the described examples of embodiments; it is rather defined by the appended patent claims. Like numbers in the figures refer throughout to like elements.
Based on the drop hammer experiments, laboratory drilling and rock fracturing simulations it can be seen that using high energy impact is not the only way to break hard rocks into chips. Also multiple impacts with lower energy levels are capable of achieving the same result. Thus, if the impact energy level is high enough, the rock is eventually broken into pieces and flushed out of the drill hole. Hence, instead of having a constant impact force, it would be advantageous to change the impact force during drilling.
Figure 1 schematically illustrates an exemplified percussion device 1 adapted for rock drilling. In figure 1, the percussion device 1 is located partly inside a drill hole 17 in a rock 15. The percussion device 1 comprises a controller 3, a percussion mechanism 5, a percussion means 7 and a drill bit 9. The percussion mechanism 5 is adapted to provide the percussion means 7 with a motion. The controller 3 is arranged to control the percussion mechanism 5 such that it imparts the percussion means 7 with a force causing the motion, whereby the percussion means 7 during drilling impacts the drill bit 9, or a drill string 11 connected to the drill bit 9, with an impact force having a specific magnitude.
The term "motion" refers to a movement in a broad sense, it may e.g. be a linear back-and-forth motion of a piston or a propagation of a pressure pulse in a fluid.
The percussion means 7 may be any means that in cooperation with the percussion mechanism 5 can provide a percussive effect. For instance, the percussion means 7 may be a piston which is movable linearly back and forth. The percussion mechanism could then be any mechanism providing the back-and-forth movement of the piston, such as e.g. a hydraulic or electric mechanism. The percussion means 7 may also be a hydraulic fluid capable of causing an impact force on the drill bit 9 directly, such as e.g. by hydraulic pressure pulses, in which case the percussion mechanism 5 may be a series of valves and chambers capable of increasing and decreasing the hydraulic pressure on the drill bit. Thus, within the scope of the invention it is conceivable to use both piston-based and piston-less drill machines. The percussion mechanism 5 and the percussion means 7 are not limited to the examples given here. Any known mechanism for causing a percussive effect on the drill bit known in the art could conceivably be used, such as e.g. hydraulic pressure pulses, pneumatically accelerated pistons, ex-center driven impacts, electrical, piezo-electrical, magnetic such as e.g. magneto restriction, acceleration of piston by magnetism, Lorentz force and electromagnetic mechanisms and means. Since the specific details regarding the percussion mechanism 5 and the percussion means 7 are not important for the invention described herein they will not be discussed further.
A drill rod or a drill string 11 may be connected to the drill bit 9. In such a case the energy transferred from the percussion means 7 to the drill string 11 will propagate through the drill string 11 to the drill bit 9. The force with which the drill bit impacts the rock will in this case be somewhat attenuated because of energy losses during the energy transfer at the boundaries as well as during the propagation.
The controller 3 is further arranged to continuously during drilling determine a desired magnitude of the impact force of the percussion means 7 and to control the percussion mechanism 5, such that the impact force of the percussion means 7 is changed, which may also be referred to as adapted, according to the desired magnitude.
Thus, the percussion device 1 described herein is capable of changing or adapting the magnitude of the impact force of the percussion means 7 on the drill bit 9 continuously during drilling resulting in a more efficient drilling procedure.
The parameter determining the drilling impact on the rock or substrate 15 is actually the force with which the drill bit 9 impacts the rock or substrate 15. However, the impact force of the percussion means 7 needed to achieve a desired impact force of the drill bit 9 on the substrate 15 may be calculated by the controller 3. Furthermore, the controller 3 may transform the impact force into an impact velocity or similar parameter in case the percussion means 7 is e.g. a piston. Thus, the controller 3 may, depending on the application, adapt or change other parameters such as impact velocity, impact energy, pressure etc. to achieve a specific impact force.
The dashed arrow in figure 1 pointing from the controller 3 to the percussion mechanism 5 represent data being sent from the controller 3 to the percussion mechanism 5. The data may be transmitted in any known manner, such as e.g. by wire or wirelessly.
According to some embodiments, the controller 3 may further be arranged to determine the desired magnitude of the impact force of the percussion means 7 based on one or several out of: in-situ data, experimental data and simulation data, wherein the data relates to one or several out of: type of rock, rock formation, type of drilling machine, and/or drill bit used.
Thus, data related to the type of rock, rock formation, type of drilling machine and/or the drill bit used may be used as input information for the algorithm determining the desired magnitude of the impact force of the percussion means 7. By adapting the impact force based on the working condition the drilling process may be tailored to the specific application, resulting in more efficient drilling with less wear and tear on the equipment. Data related to the type or formation of rock may for instance be characteristics such as e.g. hardness, brittleness, stiffness, compressive strength, tensile strength, "impact force threshold" or crack zone distribution. Data related to the type of drilling machine may be characteristics such as e.g. pulse/piston length, timing, feed force, impact frequency, rotation speed, shank and drill steel material properties such as Young's modulus, area and length. Data related to the drill bit used may be characteristics such as e.g. the number of buttons on the drill bit, button geometry, button circumferential distances, diameter, section areas or length and Young's modulus.
The data may be obtained experimentally, such as e.g. based on drop hammer or laboratory drilling experiments, force indentation curves for different rocks, impact force required and optimal indexation. Simulations can be performed on a computer system, simulating a drilling procedure with a certain combination of characteristics, such as e.g. a certain drill bit type, a certain type of drilling machine, a rock with a certain porosity etc. The magnitude of the impact force can then be varied during the simulation and over a high number of different simulations in order to obtain a recommended drilling scheme.
The in-situ data is obtained at the drilling site, or at a similar site during an earlier drilling procedure. The data may e.g. be gathered using sensors arranged at the drill site, for instance measuring the rock formation characteristics using sensors in the drill hole or sensors arranged on the drill. In figure 1 a sensor 13 is schematically shown in the drill hole. The data may be transmitted from the sensor 13 using commonly known techniques such as by wire or wirelessly. Examples of sensors used may e.g. be capacitive displacement sensors, strain gauges, inductive displacement or velocity sensors, optical stress measurements via laser or camera, force sensors and extensometers.
In figure 1 the dashed arrow pointing from the sensor 13 to the controller 3 represent data being sent from the sensor 13 to the controller 3. The data may be sent in any known manner, such as e.g. by wire or wirelessly.
According to some embodiments, the controller 3 may further be arranged to collect the in-situ data during drilling, and determine the desired magnitude of the impact force of the percussion means 7 based on the collected data.
Thus, the in-situ data may be gathered or obtained during the drilling process and used as input for the algorithm determining the desired magnitude of the impact force in real time. In this way the drilling procedure can be adapted to unanticipated variations or changes in the rock formation, thereby achieving a drilling procedure which is adapted to the actual characteristics of the rock being drilled, resulting in an efficient and thus less energy-consuming drilling procedure. In addition, less data-gathering and analysis prior to drilling is needed. Furthermore, by adapting the drilling to real-time changes in the rock the machine can be stopped quickly if need be. In addition, since data regarding the drill bit as well as the drilling machine can be gathered, the drilling procedure can be adjusted in accordance with the status of the machine, conceivably in combination with the rock characteristics. In this way, possible damage of the machine during drilling can be avoided or at least alleviated.
According to the invention, the controller 3 is further arranged to determine a desired impact force pattern. The desired magnitude of the impact force is thenbedetermined according to the desired impact force pattern for each impact of the percussion means. The controller then controls the percussion mechanism 5 such that the impact force of the percussion means 7 is changed or adapted during drilling according to the desired impact force pattern and the desired magnitude of the impact force.
Thus, the controller may control the percussion mechanism 5 such that the impact force for a number of consecutive impacts follow a specific pattern while still having a desired magnitude. For instance, if A = high impact force and B = medium impact force, a desired impact force pattern may be A B B B, i.e. one impact with a high force followed by three impacts of medium force. The specific magnitude of the force may then be determined based on other characteristics, such as e.g. the type of rock, while still following the pattern. For example, a high impact force (A) corresponding to e.g. 10 kN and a medium impact force (B) corresponding to e.g. 7 kN would follow the pattern (10-7-7-7), as would a scheme with a high impact force (A) of e.g. 5 kN and a medium impact force (B) of e.g. 3 kN (5-3-3-3).
By changing or adapting the impact force according to a desired impact force pattern in addition to the desired impact force magnitude, the drilling will be performed according to a pre-set pattern. By doing this, the drilling process can follow a higher order pattern achieving a certain effect, such as e.g. removing chips after each break of the rock, while adjusting the force according to the specific application, such as e.g. depending on the hardness of the rock. Thus, a more efficient rock drilling procedure is achieved whereby the drilling can be adapted both to a primary result such as e.g. to be able to break the rock via the magnitude of the force, and to achieve a specific secondary result, such as e.g. chip removal via the force pattern. This more efficient drilling will in turn result in less energy expenditure, less wear and tear and less downtime of the equipment.
According to some embodiments, the controller 3 may further be arranged to determine a desired cycle frequency for the impact force pattern and control the percussion mechanism 5 such that the percussion means 7 repeats the desired impact force pattern in a cyclic manner having the desired cycle frequency.
Thus, the pattern may be repeated during the entire drilling process according to a certain cycle frequency. "Cyclic" here means that an impact force pattern is repeated with a certain frequency, i.e. the cycle frequency. The cycle frequency corresponds to the number of times the pattern is repeated during a predetermined time interval, such as e.g. the number of times the pattern is repeated during a second. By repeating the pattern at a certain frequency the entire drilling procedure can be pre-set, thereby minimizing the analysis required during drilling. Furthermore, the repeated pattern can be chosen in order to achieve a certain effect which is general in applicability, i.e. an effect which is always sought in rock drilling independent of the specific application. An example of this could be the removal of chips which have been broken loose from the bedrock, as will be explained in greater detail below.
In a similar manner as for the magnitude of the impact force of the percussion means, the controller 3 may according to some embodiments, further be arranged to determine the desired impact force pattern and/or the desired cycle frequency of the impact force pattern based on one or several out of: in-situ data, experimental data and simulation data; wherein the data relates to one or several out of: type of rock, rock formation, type of drilling machine and/or the drill bit used.
According to some embodiments, the controller may be arranged to collect the in-situ data during drilling, and determine the desired impact force pattern and/or the desired cycle frequency of the impact force pattern based on the collected data.
Furthermore, the controller may, according to some embodiments, be arranged to adjust the desired impact force pattern and/or the desired cycle frequency of the impact force pattern continuously during drilling.
Thus, the data may relate to the same type of characteristics and be obtained in the same manner as mentioned earlier with regards to the changes of the magnitude of the impact force, though this time the data is used to determine the desired impact force pattern and/or the desired cycle frequency. The same kind of advantages as described above is therefore achieved. Furthermore, the data may be collected and used to determine all three of these parameters, i.e. the magnitude of impact force, the impact force pattern and the cycle frequency. In fact, by collecting the data and taking all three parameters and how they interact into consideration, an optimized drilling procedure with regards to those parameters can be obtained.
Thus, the magnitude of the impact force, the impact force pattern and the frequency of the pattern can all be varied in order to achieve a drilling procedure which is optimal with regards to efficiency, reducing energy consumption, wear and tear and force requirements. A couple of exemplifying ways of choosing the pattern follows below.
If A is a high impact force, B is a medium impact force and C is a low impact force, examples of the patterns may be A,B,B,B or A,B,C,C. There are many alternatives to set these patterns as well as the right impact force and frequency. As has been described above these parameters may be based on experimental, simulation or in-situ observations.
For instance, in one embodiment one hard impact to chip the rock is followed by a few moderate impacts to facilitate the flushing or removal of the chips from the drill hole, e.g. A, B, B, B or A,B,B.
According to another embodiment no high force impacts are used. Instead a higher number of moderate force impacts mixed with low force impacts achieve the same result, e.g. B, B, B, C, C, C, C. In this case the frequency may be increased in order to provide the required drilling rate.
According to another embodiment, the changing pattern and/or the changing magnitude and/or the changing frequency could for instance be an adaptive change every n^th impact, where the changes or adaptations of the pattern and/or magnitude and/or frequency are determined based on the different characteristics mentioned above, such as e.g. characteristics of the rock, the drill bit etc. Thus, the changes to the parameters may be performed continuously during drilling, but only every n^th impact, where n could be any integer value, such as e.g. an integer value above a certain threshold value. Another possibility would be to perform the change after a specific time interval. A reason for doing this would be to avoid too frequent regulation of the percussion mechanism 5, thereby reducing the risk of swings in the regulation which may happen when the rock or substrate 15 is rapidly varying and the controller 3 tries to adapt to the changes. Too frequent regulation may result in increased wear of components. Thus, by performing the changes only every n^th impact or after a certain time interval too frequent changes are avoided, resulting in decreased wear of components.
The pattern could also be changed or adapted continuously during drilling while still being repeated in a cyclic manner. For instance, the impact force could follow a first pattern for a certain number of cycles repeated with a first frequency and then be changed to a second pattern which is repeated for a number of cycles with the first frequency or with a second frequency. The change of the pattern and/or frequency could for instance be based on changing rock characteristics detected during drilling.
It should be mentioned that if the impact energy is less than a certain level, even multiple impact may fail to break the material. This phenomenon may be explained by the fact that there is a certain compressive stress level needed to first crush the rock deep enough and then a certain tensile stress level needed in the rock to overcome its tensile strength and open the cracks. If the energy level is lower than a certain level, these cracks may not form or their length may be so small that the chipping does not occur. Thus, a minimum or lower threshold for the magnitude of the impact force may be determined and the subsequent changes or adaptations of the impact force may be set to always be equal to or higher than the lower threshold, in order to create the chipping and thus subsequently break the rock.
Thus, the optimal value of the parameters mentioned above, i.e. the magnitude of the impact force, the impact force pattern and the frequency of the pattern, for a specific application may be determined by e.g. experimentation, observation and/or simulation. These parameters can then be set during drilling according to their optimal values. This will lead to an increased efficiency of the drilling machine which will save energy, lead to less wear and tear and reduce the feed force requirements.
Figure 2 illustrates an exemplifying method 200 for controlling a percussion mechanism 5 of a percussion device 1 adapted for rock drilling. Dashed boxes and lines represent optional method steps.
The percussion device 1 comprises the percussion mechanism 5, a percussion means 7 and a drill bit 9. The percussion mechanism 5 is adapted to provide the percussion means 7 with a motion. The method comprises controlling the percussion mechanism 5 such that it imparts the percussion means 7 with a force causing the motion, whereby the percussion means 7 during drilling impacts the drill bit 9, or a drill string 11 connected to the drill bit 9, with an impact force having a specific magnitude.
The method may for instance be performed by a controller 3. In order to be able to control the percussion mechanism 5 in an optimal manner the controller 3 is configured to change or adapt the magnitude of the impact force. Therefore, the method comprises: determining 201, continuously during drilling, a desired magnitude of the impact force of the percussion means 7. The method further comprises: controlling 209, continuously during drilling, the percussion mechanism 5 such that the impact force of the percussion means 7 is changed, which may also be referred to adapted, according to the desired magnitude.
By following the above described method, the percussion mechanism 5 of the percussion device 1 is controlled in such a manner that the impact force of the percussion means 7 is changed continuously during drilling. For sake of clarity it should be understood that the steps may be repeated a number of times. Since the method is performed continuously during drilling this is usually the case.
According to some embodiments, the method step of determining 201 may further comprise determining the desired magnitude of the impact force based on one or several out of: in-situ data, experimental data and simulation data. The data may relate to one or more out of: type of rock, rock formation, type of drilling machine and/or drill bit used.
According to some embodiments, the method step of determining 201 may further comprise: collecting the data in-situ during drilling, and determining the desired magnitude of the impact velocity based on the collected data.
According to some embodiments, the method may further comprise: determining 203 a desired impact force pattern. The desired magnitude of the impact force may then be determined 205 according to the desired impact force pattern for each impact of the percussion means 7. The method may then further comprise: controlling 209 the percussion mechanism 5 such that the impact force of the percussion means 7 is changed during drilling according to the desired impact force pattern determined in step 203 and the desired magnitude of the impact force determined in step 205.
According to some embodiments, the method may further comprise: determining 207 a desired cycle frequency for the impact force pattern and to then control 209 the percussion mechanism 5 such that the percussion means 7 repeats the desired impact force pattern in a cyclic manner having the desired cycle frequency as determined in step 207.
In figure 2 an arrow pointing back from step 209 to step 201 indicates that the pattern may be repeated.
According to some embodiments, the method may further comprise determining the desired impact force pattern and/or the desired cycle frequency of the impact force pattern based on one or several out of: in-situ data, experimental data and simulation data. The data may relate to one or several out of: type of rock, rock formation, type of drilling machine and/or the drill bit used.
According to some embodiments, the method may further comprise collecting the data in-situ during drilling, and determining the desired impact force pattern and/or the desired cycle frequency of the impact force pattern based on the collected data.
Furthermore, according to some embodiments, the method may further comprise: to adjust the desired impact force pattern and/or the desired cycle frequency of the impact force pattern continuously during drilling.
By performing the method above, the desired magnitude of the impact force and/or the desired impact force pattern and/or the desired cycle frequency of the impact force pattern may be adjusted continuously during drilling.

Claims

A method for controlling a percussion mechanism (5) of a percussion device (1) adapted for rock drilling, the percussion device (1) comprising a controller (3), the percussion mechanism (5), percussion means (7) and a drill bit (9), where the percussion mechanism (5) is adapted to provide the percussion means (7) with a motion and where the controller (3) is arranged to control the percussion mechanism (5) such that it imparts the percussion means (7) with a force causing the motion, whereby the percussion means (7) during drilling impacts the drill bit (9), or a drill string (11) connected to the drill bit (9), with an impact force having a specific magnitude;
characterized in that the method comprises, continuously during drilling:
- determining (201) a desired magnitude of the impact force of the percussion means by determining (203) a desired impact force pattern for a number of consecutive impacts and determining (205) the desired magnitude of the impact force according to the desired impact force pattern for each impact of the percussion means (7); and

- controlling (209) the percussion mechanism (5) such that the impact force of the percussion means (7) is changed during drilling according to the desired impact force pattern and the desired magnitude of the impact force.
The method according to claim 1, characterized in that the method further comprises: determining the desired magnitude of the impact force based on one or several out of:
in-situ data, experimental data and simulation data;

wherein the data relates to one or several out of:
- type of rock

- rock formation

- type of drilling machine, and/or

- drill bit used
The method according to claim 2, characterized in that the method further comprises:
collecting the data in-situ during drilling, and

determining the desired magnitude of the impact force based on the collected data.
The method according to any of claims 1-3, characterized in that the method further comprises:
determining a desired cycle frequency for the impact force pattern;

controlling the percussion mechanism (5) such that the percussion means (7) repeats the desired impact force pattern in a cyclic manner having the desired cycle frequency.
The method according to claim 4, characterized in that the method further comprises:
determining the desired cycle frequency of the impact force pattern based on one or several out of: in-situ data, experimental data and simulation data; wherein the data relates to one or several out of:
- type of rock,

- rock formation,

- type of drilling machine, and/or

- the drill bit used.
The method according to any of claims 1-5, characterized in that the method further comprises:
determining the desired impact force pattern based on one or several out of: in-situ data, experimental data and simulation data; wherein the data relates to one or several out of:
- type of rock,

- rock formation,

- type of drilling machine, and/or

- the drill bit used.
The method according to claim 5, characterized in that the method further comprises:
collecting the data in-situ during drilling, and

determining the desired impact force pattern and/or the desired cycle frequency of the impact force pattern based on the collected data.
A percussion device (1) adapted for rock drilling comprising a controller (3), a percussion mechanism (5), a percussion means (7) and a drill bit (9), the percussion mechanism (5) being adapted to provide the percussion means (7) with a motion, the controller (3) being arranged to control the percussion mechanism (5) such that it imparts the percussion means (7) with a force causing the motion, whereby the percussion means (7) during drilling impacts the drill bit (9), or a drill string (11) connected to the drill bit (9), with an impact force having a specific magnitude; characterized in, that the controller (3) is further arranged to, continuously during drilling,
- determine a desired magnitude of the impact force of the percussion means by determining a desired impact force pattern for a number of consecutive impacts and determining the desired magnitude of the impact force according to the desired impact force pattern for each impact of the percussion means (7); and

- control the percussion mechanism (5) such that the impact force of the percussion means (7) is changed during drilling according to the desired impact force pattern and desired magnitude of the impact force.
The percussion device (1) according to claim 8, characterized in that the controller (3) is further arranged to determine the desired magnitude of the impact force of the percussion means (7) based on one or several out of: in-situ data, experimental data and simulation data;
wherein the data relates to one or several out of:
- type of rock

- rock formation

- type of drilling machine, and/or

- drill bit used
The percussion device (1) according to claim 9, characterized in that the controller (3) is arranged to collect the in-situ data during drilling, and determine the desired magnitude of the impact force of the percussion means (7) based on the collected data.
The percussion device (1) according to any of claims 8-10, characterized in that the controller (3) is further arranged to:
determine a desired cycle frequency for the impact force pattern;

control the percussion mechanism such that the percussion means repeats the desired impact force pattern in a cyclic manner having the desired cycle frequency.
The percussion device (1) according to claim 11, characterized in that the controller (3) is further arranged to:
determine the desired cycle frequency of the impact force pattern based on one or several out of: in-situ data, experimental data and simulation data; wherein the data relates to one or several out of:
- type of rock,

- rock formation,

- type of drilling machine, and/or

- the drill bit used.
The percussion device (1) according to any of claims 8-12, characterized in that the controller (3) is further arranged to:
determine the desired impact force pattern based on one or several out of: in-situ data, experimental data and simulation data; wherein the data relates to one or several out of:
- type of rock,

- rock formation,

- type of drilling machine, and/or

- the drill bit used.
The percussion device (1) according to claim 12, characterized in that the controller (3) is further arranged to:
collect the in-situ data during drilling, and

determine the desired impact force pattern and/or the desired cycle frequency of the impact force pattern based on the collected data.