METHOD OF CONTROLLING A DRILLING PROCESS OF A PERCUSSION DRILLING MACHINE

Abstract

The drilling machine comprises a control unit and at least one sensor. The drilling machine further comprises a percussive element and a tool, wherein an end of the tool comprises a drill bit configured to strike rock. The percussive element is configured to impact the tool and the tool is configured to transfer impulse energy generated by the percussive element to the drill bit. The method during drilling comprises collecting data depending on force fed into the rock and indentation depth into the rock at an impact of the percussive element. The method further comprises determining a percussion procedure based on the collected data, and determining a deviation between the percussion procedure and a reference percussion procedure. The method further comprises adjusting one or more drilling parameters related to the drilling process based on the deviation.

Claims

1. A method of controlling a drilling process of a drilling machine, wherein the drilling machine comprises a control unit, at least one sensor, a percussive element and a tool, wherein an end of the tool comprises a drill bit configured to strike rock, wherein the percussive element is configured to impact the tool and the tool is configured to transfer impulse energy generated by the percussive element to the drill bit characterized in that the method during drilling comprises: collecting data depending on force fed into the rock and indentation depth into the rock at an impact of the percussive element, determining a percussion procedure based on the collected data, determining a deviation between the percussion procedure and a reference percussion procedure, adjusting one or e drilling parameters related to the drilling process based on the deviation.

2. The method according to claim 1, wherein the reference percussion procedure describes a desired drilling process.

3. The method according to claim 1, wherein the step of adjusting one or more drilling parameters comprises: adjusting said one or more drilling parameters such that the deviation is reduced.

4. The method according to claim 1, wherein the method further comprises: analyzing properties of the deviation, based on said analysis, determine one or more first drilling parameters that need to be adjusted to reduce the deviation, out of said one or more drilling parameters, wherein the step of adjusting said one or more drilling parameters comprises: adjusting said one or more first drilling parameters such that the deviation reduced,

5. The method according to claim 1, wherein the method further comprises: analyzing properties of the deviation, based on said analysis, determining a first manner of adjusting the one or more drilling parameters such that the deviation is reduced, wherein the step of adjusting said one or more drilling parameters comprises: adjusting said one or more drilling parameters in said first manner such that the deviation is reduced.

6. The method according to claim 1, wherein the percussion procedure consists of a force-displacement curve determined based on the collected data and wherein the reference percussion procedure consists of a reference force-displacement curve determined based on the desired drilling process.

7. The method according to claim 1, wherein the method further comprises: executing a critical action if the deviation exceeds a threshold value, wherein the critical action comprises one or more of: visually indicating that the threshold value has been exceeded, indicating that the threshold value has been exceeded by emitting an audio signal, interrupting the drilling process.

8. The method according to claim 1, wherein the method further comprises: evaluating how the deviation has changed after the adjustment, adjusting said one or more drilling parameters based on the evaluation such that the deviation is reduced.

9. The method according to claim 8, wherein the evaluation comprises: collecting a subsequent set of data depending on force fed into the rock and indentation depth into the rock at a subsequent impact of the percussive element, determining a subsequent percussion procedure based on the collected data, determining a subsequent deviation between the subsequent percussion procedure and the reference percussion procedure, evaluating how the deviation has changed after the adjustment based on a comparison between the deviation and the subsequent deviation.

10. The method according to claim 1, wherein the method is performed with each impact of the percussive element.

11. The method according to claim 1, wherein the one or more drilling parameters relate to one or more of: flushing flow, rotation speed of the rock drill, feed force, percussion power, percussion frequency, stroke length, percussion speed, rotational torque, waveform of an impulse

12. The method according to claim 1, wherein said collected data comprises data related to strain of the tool in operation.

13. A drilling machine comprising a control unit, at least one sensor, a percussive element and a tool, wherein an end of the tool comprises a drill bit configured to strike rock, wherein the percussive element is configured to impact the tool and the tool is configured to transfer impulse energy generated by the percussive element to the drill bit, wherein the control unit is configured to control the drilling machine during drilling according to the method of claim 1.

14. The drilling machine according to claim 13, wherein the at least one sensor is configured to collect data depending on force fed into the rock and indentation depth into the rock at an impact of the percussive element.

15. The drilling machine according to claim 1, herein the drilling machine is a rock drilling machine.

Description

DESCRIPTION OF DRAWINGS

[0038] Further objects and advantages of, and features of the invention will be apparent from the following description of one or more embodiments, with reference to the appended drawings, where:

[0039] FIG. 1 shows a schematic view of an exemplary drilling machine,

[0040] FIG. 2 shows a number of number of force-displacement curves,

[0041] FIG. 3 shows a schematic force-displacement curve and a schematic reference force-displacement curve,

[0042] FIG. 4a shows a schematic force-displacement curve and a schematic force-displacement curve according to a first example,

[0043] FIG. 4b shows a schematic force-displacement curve and a schematic force-displacement curve according a second example,

[0044] FIG. 5 shows a flow chart of a method of controlling a drilling process of a drilling machine.

DETAILED DESCRIPTION

[0045] The present invention is described in more detail below, with references to the appended drawings showing examples of embodiments. The invention should not be viewed as limited to the described examples of embodiments, instead it is defined by the appended patent claims. Like numbers refer to like elements throughout the description.

[0046] FIG. 1 shows very schematically an exemplary drilling machine 1. The drilling machine 1 comprises a control unit 3 and at least one sensor 5. The drilling machine 1 further comprises a percussive element 7 and a tool 9. The percussive element 7 may for instance be a percussive piston and the tool 9 may for instance be a drill string consisting of an adapter, one or more connected drill rods and a drill bit 11 configured to strike rock 13. An end of the tool 9 comprises the drill bit 11. The percussive element 7 is configured to impact the tool 9 at high speed. The tool 9 is in turn configured to transfer 5 impulse energy generated by the percussive element 7 to the drill bit 11. The drill bit 11 will then strike the rock 13, whereby buttons (not shown) arranged on the drill bit will indent the rock 13 and will make progress into the rock 13, making a hole 15 in the rock.

[0047] As described above, rock drilling is an energy-consuming activity. Both properties and features of the rock, the properties of the tool 9, such as type of bits, material, size, etc., as well as the drilling parameters that are used, will affect the drilling process. By drilling parameters is hereby meant flushing pressure, flushing flow, percussion speed, rotational speed, feed force, etc.

[0048] It is often desirable to determine whether the current drilling proceeds in a desirable manner and, if that is not the case, adjust the drilling so that it better corresponds to a desired drilling process. This is especially important for autonomous or semi-autonomous drilling, where the control unit 3 controls large parts, or the whole, drilling process.

[0049] The desired drilling process may vary. The desired drilling process may for instance be to drill using a minimum of energy for a given depth of the hole 15. Or a fast drilling process may be desired. Some of these wishes may counteract each other. A fast drilling process may for instance lead to increased wear of the tool 9. Other wishes may cooperate.

[0050] Regardless of the desired drilling process, the efficiency or capability of the current drilling process has to be quantifiable. The know methods of prior art, for quantifying the current drilling process, do not describe the actual drilling process well enough, and therefore the control of the drilling process becomes blunt.

[0051] To solve this problem, the sensor 5, according to the invention, collects measured data depending on force fed into the rock 13 and indentation depth into the rock 13 at an impact of the percussive element 7. Thus, when the percussive element 7 impacts the tool 9 and the tool 9 impacts the rock 13 and recoils, the sensor 5 collects these measurement data. The sensor 5 may for instance collect these data by measuring the axial strain of the tool 9 at the impact. A percussion procedure is thereafter determined based on the collected data. The percussion procedure describes the whole course of the impact and is therefore based on the force fed into the rock 13 as well as the indentation depth into the rock 13. The percussion procedure may then be compared to a reference percussion procedure. The reference percussion procedure may describe a desired drilling process. The current percussion procedure may be compared to the reference percussion procedure by determining a deviation between the two percussion procedures. Based on 5 that deviation, one or more drilling parameters related to the drilling process may then be adjusted. The drilling parameters may for instance be adjusted such that deviation is reduced. Naturally, it may always be determined that the deviation will be reduced upon adjustment of the drilling parameters. Therefore, the expression “such that deviation is reduced” should be interpreted such that the drilling parameters are adjusted with the intention to reduce the deviation by the adjustment.

[0052] The drilling machine 1 is configured to at least partly be controlled by the control unit 3, based on the measured data collected by the sensor 5 and the comparison between the percussion procedure and the reference percussion procedure.

[0053] The percussion procedure may be represented by a force-displacement curve determined based on the collected data. FIG. 2 shows a number of force-displacement curves based on data provided by lab measurements and exemplifies how the force-displacement curve may vary during drilling. The force F fed into the rock is shown along the y-axis and the indentation depth into the rock is shown along the x-axis. As demonstrated by FIG. 2, the force-displacement curve may vary considerably during drilling, in the same rock and with the same drilling parameters. The change in the force-displacement curve is correlated with the drilling efficiency. The force-displacement curves describe a percussion procedure of the tool, with an initial load phase of the tool when the buttons indent the rock and a concluding unload phase when the tool is retracted from the newly made hole.

[0054] A desired force-displacement curve which represents a desired drilling process having a desired drilling efficiency may be determined by studying force-displacement curves for different drilling processes and by correlating efficient drilling processes with a certain type of force-displacement curve. In this manner, a reference percussion procedure is obtained, which is represented by a reference force-displacement curve. By thereafter determining force-displacement curves for impacts of the tool 9 into the rock 13 during drilling, these may be compared to the desired force-displacement curve. The drilling parameters may later be adjusted based on this comparison.

[0055] The force-displacement curve may for instance be determined by selecting a time window from the time data of the axial wave of the incident and reflected impulse. A known length of the drill bit is used for the time window, as well as a sensor giving the axial strain wave in the drill bit. The sensor may also be arranged in different positions on 5 the drill bit or on the neck. The position will affect the measured signal, which has to be taken into consideration. The force-displacement curve may be determined according to the following.

[00001]${\sigma }_{inc}={\mathrm{.Math.}}_{inc}E{\sigma }_{\mathrm{ref}}={\mathrm{.Math.}}_{\mathrm{ref}}EF=A_{rod}\left({\sigma }_{inc}+{\sigma }_{\mathrm{ref}}\right)$$v_{\mathrm{bit}}=\frac{1}{c\rho }\left({\sigma }_{inc}-{\sigma }_{\mathrm{ref}}\right)$$d=\int v_{bit}\mathrm{dt}$

where σ.sub.inc is the stress of the incident wave, σ.sub.ref is the stress of the reflected wave, E is the module of elasticity. Further: [0056] ε.sub.inc=selected strain signal around the incident wave, selected by using a trigger from the time data or a reference pulse from the impact and geometry and wave velocity in the rod. [0057] ε.sub.ref=selected strain signal around the reflected wave, selected by determining a selection time in relation to sensor position of ε.sub.inc and geometry of the rod and of the drill bit as well as wave velocity.

[0058] Other methods of determining the force-displacement curves are also comprised by the invention. For instance, the calculation has to be adjusted when multiple sensors are used. The methods are generally known in the fields of signal processing and wave propagation and will consequently not be further discussed here.

[0059] FIG. 3 shows an example of a schematic force-displacement curve represented by three vectors ki, kc, kr. Force fed into the rock is shown along the y-axis and the indentation depth is shown along the x-axis. The vectors ki and kc represent the load phase and kr represents the unload phase.

[0060] The reference percussion procedure may also be constituted by a force-displacement curve determined by the desired drilling process. In FIG. 3 the reference curve is shown as a dashed line. The force-displacement curves, and thereby the percussion procedures, may for instance be compared to the method of least squares to 5 obtain a deviation between the curves. Other ways of comparing the curves may for instance be to compare part-curves via measurement data, such as slope and length. The measurement data may be expressed in absolute numbers as well as in relative terms, i.e. in relation to each other. Other examples comprise studying the angle of the vectors ki, kc and kr. By determining a percussion procedure, the deviation between the current percussion procedure and the reference percussion procedure may be analyzed. FIGS. 4a and 4b illustrate how a comparison between the force-displacement curve of the current percussion procedure and the force-displacement curve of the reference percussion procedure may be used to analyze the deviation.

[0061] In FIG. 4a a schematic current percussion procedure is shown as a continuous line and a reference percussion procedure is shown as a dashed line. The reference percussion procedure represents a desired percussion procedure. As shown in FIG. 4a, the buttons do not seem to penetrate very deep into the rock. Concurrently, the feed force is high for a short time. This may mean that the rock is too hard or that the rotational speed of the drill string is too low. This information may thus be used to determine which drilling parameters to adjust, i.e. rotational speed, and how it should be adjusted, i.e. to increase the speed.

[0062] Also FIG. 4b schematically shows a current percussion procedure as a continuous line and a reference percussion procedure as a dashed line. The reference percussion procedure represents a desired percussion procedure. As can be seen in FIG. 4b, the buttons seem to penetrate deeper than expected and the force fed into the rock is lower than expected. This may mean that the flushing flow is too low, resulting in drill cuttings remaining in the hole 15, or that the rock 13 is too soft. This analysis may therefore be used to increase the flushing pressure or the flow, i.e. selecting a drilling parameter to adjust and deciding how this drilling parameter should be adjusted.

[0063] Thus, based on this analysis, it is possible to determine one or more first drilling parameters from said one or more drilling parameters that need to be adjusted to reduce the deviation. In addition, based on this analysis, it is possible to determine a first manner of adjusting the one or more drilling parameters such that the deviation is reduced.

[0064] The deviation between the percussion procedure and the reference percussion procedure may also be used to ensure that the drilling process proceeds in a manner that is safe for the equipment and for its surroundings. By making sure that the deviation is below a certain threshold value it may be assured that the drilling process is running normally. If the drilling machine 1 should penetrate into a tunnel and no longer hit rock, the deviation would increase abruptly and exceed the threshold value. In such an occurrence, the control unit 3 may execute a critical action. The critical action may for instance comprise visually indicating that the threshold value has been exceeded, such as to an operator. An alarm may be made to sound when the threshold value has been exceeded, or the drilling process may be interrupted to ensure that the machine does not suffer damage.

[0065] A method 500 of controlling a drilling process of a drilling machine 1 will now be described, referring to FIG. 5. Optional method steps are shown with dashed lines in the drawings.

[0066] The method steps described below may for instance be carried out by the control unit 3.

[0067] FIG. 5 shows an exemplary method 500 of controlling a drilling process of drilling machine 1. The drilling machine 1 comprises a control unit 3, at least one sensor 5, a percussive element 7 and a tool 9. An end of the tool 9 comprises a drill bit 11 configured to strike rock 13. The percussive element 7 is configured to impact the tool 9, and the tool 9 is configured to transfer impulse energy generated by the percussive element 7 to the drill bit 11. The method during drilling comprises collecting 501 data depending on force fed into the rock and indentation depth into the rock at an impact of the percussive element 7. The method further comprises determining 502 a percussion procedure based on the collected data. The method further comprises determining 503 a deviation between the percussion procedure and a reference percussion procedure. The method further comprises adjusting 507 one or more drilling parameters related to the drilling process based on the deviation.

[0068] The deviation between the reference percussion procedure and the actual percussion procedure may be determined in a number of different ways depending on how the percussion procedures are represented as describe above.

[0069] The reference percussion procedure may for instance be determined empirically, based on previous drilling processes which were considered, or which have proved to be efficient, e.g. from an energy point of view or in terms of progress into the rock. The reference percussion procedure may describe a drilling process where a certain 5 parameter is optimized, such as drilling speed, energy consumption or minimized wear of the drill. Optimization of these parameters may then be made at the cost of some other parameter, such as energy efficiency, etc. Alternatively, the reference percussion procedure may describe a drilling process which is considered to be an optimal or efficient drilling when a number of parameters are balanced against each other. It is also conceivable that the reference percussion procedure has been determined by calculations or simulations and therefore describes and optimized procedure. The reference percussion procedure may for instance be picked from a database.

[0070] According to certain embodiments, the step of adjusting 507 said one or more drilling parameters may comprise adjusting 507 said one or more drilling parameters such that the deviation is reduced.

[0071] The method may further comprise analyzing 504 properties of the deviation and based on said analysis, determine 505 one or more first drilling parameters that need to be adjusted to reduce deviation, out of said one or more drilling parameters. The step of adjusting 507 said one or more drilling parameters comprises adjusting 507 said one or more first drilling parameters such that the deviation is reduced.

[0072] The method may further comprise analyzing 504 properties of the deviation, and based on said deviation determining 506 a first manner of adjusting the one more drilling parameters such that the deviation is reduced. The step of adjusting 507 said one or more drilling parameters then comprises adjusting 507 said one or more drilling parameters in said first manner such that the deviation is reduced.

[0073] What is meant by “a first manner” depends on what drilling parameter should be changed. If it relates to percussion speed, the first manner may be to increase or to decrease the percussion speed. If it relates to flushing pressure, the first manner may be to increase or decrease the flushing pressure, etc. A skilled person would immediately realize what it means to adjust a parameter in a certain manner, i.e. a first manner, given that the parameter is known. This will therefore not be further described.

[0074] The method may further comprise executing 513 a critical action if the deviation exceeds a threshold value, wherein the critical action comprises one or more of visually indicating that the threshold value has been exceeded, indicating that the threshold value has been exceeded by emitting an audio signal, and interrupting the drilling process.

[0075] The method may further comprise evaluating 511 how the deviation has changed after the adjustment 507. The method then further comprises adjusting 512 said one or more drilling parameters based on the evaluation such that the deviation is reduced. According to some embodiments, the method may then further comprise collecting 508 a subsequent set of data depending on force fed into the rock and indentation depth into the rock at a subsequent impact of the percussive element. The method then further comprises determining 509 a subsequent percussion procedure based on the collected data and determining 510 a subsequent deviation between the subsequent percussion procedure and the reference percussion procedure. The step to evaluate 511 how the deviation has changed after the adjustment is then based on a comparison between the deviation and the subsequent deviation.

[0076] By adhering to the method described above, the drilling process of the drilling machine 1 will be controlled. For the sake of clarity it should be noted that the above steps may be executed a number of times during drilling, such as with each impact of the percussive element 7.

[0077] The reference percussion procedure may describe a desired drilling process. The one or more drilling parameters may relate to one or more of flushing, rotational speed of the rock drill, feed force, percussion power, percussion frequency, stroke length, percussion speed, rotational torque or the waveform of the impulse. Said collected data may comprise data related to strain of the tool during operation.