WO2009123535A1

WO2009123535A1 - Method and apparatus for adjusting and controlling a parameter

Info

Publication number: WO2009123535A1
Application number: PCT/SE2009/000173
Authority: WO
Inventors: Jonas Sinnerstad; Magnus Olsson
Original assignee: Atlas Copco Rock Drills Ab
Priority date: 2008-04-01
Filing date: 2009-04-01
Publication date: 2009-10-08
Also published as: FI20106140A; SE534665C2; FI125984B; SE1051134A1; SE533084C2; SE0800745L

Abstract

A method and a control system for regulating at least one drilling parameter when drilling in rock. An impulse-generating device is arranged via an impact means to induce shock waves in a tool acting on the rock during the drilling. The impulse- generating device is arranged with a control unit, designed to set a reference rate, determine a current feed rate, and calculate a control signal as a function of the reference rate and the current feed rate. Moreover, the control unit is designed to automatically regulate a new feed rate for said impulse-generating device.

Description

Method and apparatus for adjusting and controlling a parameter

Technical field

The present invention concerns a method for controlling at least one drilling parameter for an impulse-generating device when drilling in rock, wherein the impulse-generating device is arranged via an impact means to induce shock waves in a tool acting on the rock during the drilling, wherein the impulse-generating device is arranged so that it can be moved in the drilling direction relative to a sup- port means. The invention also specifies a computerised control system, which comprises means of carrying out the method. Furthermore, the invention comprises a drill rig which contains a computerised control system according to the invention.

Prior art

In rock drilling one often makes use of percussion drilling, wherein a usually hy- draulically driven striking piston is used to create a shock wave by the force of a blow generated with a hydraulic pressure (percussion pressure), which is transported via drill steel (the drill string) to a drill bit and then to the rock. When the shock wave hits the drill bit, its hard metal button is pressed into the rock, which generates so great a force that the rock is crushed. The crushed rock, known as drill cuttings, is then transported out from the drilling hole with water pressure or air pressure, which is brought through a hole in the drill steel and down to the drill bit. The drill steel is rotated so that the hard metal pin can make contact with un- crushed rock, which is done for example by a transmission and hydraulic motor.

The drilling machine itself can for example be fixed to a sled, which in turn runs along a support means, such as a feed beam, fastened to a carrier, such as a vehicle. By driving the sled, and thus the drilling machine, along the feed beam toward the rock, the drill bit is pressed against the rock. The sled can be driven by a hydraulic cylinder, usually called a feed cylinder. Alternatively, the drilling ma- chine can be driven forward by use of a so-called chain feeder, where the feed cylinder is replaced by a hydraulic gear motor (feed motor). The sled with drilling machine can then be driven forward and back along the beam by a chain secured to the sled and driven by the feed motor, running along the feed beam. The hydraulic pressure driving the feed cylinder/feed motor is generally called the feed pressure and it indicates the force pressing the drill bit against the rock. The speed of the drilling machine and sled during the drilling is generally called the drilling rate or feed rate. The feed rate (drilling rate) is usually governed by controlling the feed cylinder/feed motor with an electronically controlled hydraulic valve.

The flow equation for a hydraulic valve states that the flow q from the valve is equal to the opening area A of the valve times the root of the pressure difference Δp across the valve, where C 1 , C2 are constants:

q = C₁ * A * J^* C₂ (1)

By holding the pressure difference Δp constant, the flow q from the valve through the valve remains directly proportional to the opening area A. Thus, the flow q can be controlled by controlling the opening area A if the pressure difference Δp is held constant.

To control the drilling rig when performing various drilling applications, and when manoeuvring and moving the rig around, the drilling rig usually comprises a control system comprising a control unit. The control system is adjusted by entering drill parameters, such as the desired feed pressure, for different applications. The control system is adjusted with general drill parameters in the beginning. The rig's program contains a large number of drilling functions, corresponding to these applications, and some of these are designed for different situations, such as collaring, i.e., the starting process before the drill bit reaches the rock, drilling, fixed drilling, deceleration of the sled, or backing off of the drill steel. A number of drill parameters are set for each drilling function. These parameter values have been tested in advance for each particular rig.

When the present-day control system has to be adjusted, the operator or service technician enters a number of values for the drill parameters. The desired feed pressure adjusted corresponds to the actual pressure in the system, which means it is relatively easy to make a prognosis for this drill parameter, since the setpoint value for the feed pressure and the actual pressure are directly related to each other.

To adjust the feed rate (drilling rate), i.e., how fast the sled/drilling machine is driven forward, the feed rate (drilling rate) must be adjusted according to the flow. The electronically controlled hydraulic valve is usually controlled by making the flow through the valve directly proportional to a control current going to the valve. Each desired flow is determined by the operator or service technician setting a corresponding control current as a drill parameter for the electronically controlled hydraulic valve. If the pressure difference across the valve is main- tained constant, the opening area of the pressure-compensated valve will be proportional to the setpoint current and in this way one gets a flow that governs the feed rate. Each current value corresponds to a specific rate, but since the current is not a direct value of the rate, it is quite difficult for the operator to get a feel as to what current will result in what rate when setting up the rig. It requires long ex- perience with the control system to know what rate corresponds to a specific current value. Thus, when the operator or service technician is working with a different drill rig with a different valve or different dimensions for the feed cylinder/feed motor, the same control current will correspond to a totally different feed rate. This often results in the operator/service technician adjusting the control sys- tern with presumably suitable values for the drill parameters and then testing the values by performing test drillings. During the test drillings, manual corrections are made to the control currents of the hydraulic valve to suit the present application. If the operator/service technician is relying on test drilling to correct the parameters, there is always a risk of omitting the test drilling for a certain applica- tion, and thus the corresponding parameters will not be corrected. It also happens that the settings no longer apply when the drill rig is used for some time and the tooling gets worn down. Moreover, the control current depends on which feed cylinder or feed motor is being used in the particular case.

When drilling with a drilling machine of the above type, it is common that the prevailing drilling conditions often change. There are many rock types, and depending on their structure, such as the hardness, they are not the same to drill in. As a general rule, an increase in the feed rate (drilling rate) is an indication that the rock is becoming softer.

The preceding also means it is hard to make general recommendations on how to adjust the rigs, since the control currents seldom correspond to the same speed for different kinds of rigs. This means it is hard to adjust the drill rig in place for drilling at a new location. Thus, there is a need for an improved method and device for regulating the feed rate.

Presentation of the invention

A first purpose of the invention is to create a method of the above indicated kind that solves the aforementioned problem.

The solution is a method having the characteristic features of claim 1 and a control system having the characteristic features of claim 10.

Such a method for control of a feed rate for a rock drilling machine when rock drilling, wherein the rock drilling machine is arranged with a control unit, comprises: a) entering a reference rate in the control unit, b) automatically regulating the feed rate for as a function of the reference rate.

Such a computerised control system for controlling of a feed rate for a rock drilling machine when rock drilling, wherein control system is arranged with a control unit, and a display for entering a reference rate in the control unit, wherein the control unit is arranged so that it is automatically regulating the feed rate for the rock drilling machine as a function of the reference rate.

By regulating the feed rate automatically as a function of the reference rate by using the desired rate, the reference rate, as a regulation parameter it is possible for the operator to make a precise and simple rate adjustment applicable for the cho- sen application instead of taking a current value that represents a presumed rate and thus is not adapted to the individual drill rig. Since each drill rigs has different applications depending on individual parameters for the drill rig and the feed motor and the feed cylinder has individual differences and do not result in the same modulation of the hydraulic valve despite the fact that it is the same model it is not possible to set a generally applicable control current for each application. The current modulation of the hydraulic valve is also not a linear function, but is linear within a predefined interval. A benefit from determining the feed rate automatically is thus that is made possible to make individual and precise setting of the feed rate for each drill rig in a simple way. With our invention a more simple, quicker and more correct adjustment than what is brought about if the operator instead takes a current value that represents a presumed rate which has to be tested by performing test drillings several times with a following correction of the control current of the hydraulic valve each time to adapt the settings of the current application. Since the adjustment process is hereby simplified and the risk of wrong settings for the rig is minimised, there is less need for training of the operator, which also means a savings of resources.

In one embodiment of the invention, the method further comprises determining a control signal as a function of the reference rate, and regulating the feed rate as a function of the control signal. In yet another embodiment of the method of the invention, the method comprises determining a current feed rate calculating the control signal as a function of the reference rate and the current feed rate. Thereby using a computerised control system according to the invention comprising means for determining a current feed rate, and a calculator unit arranged to calculate a control signal as a function of the reference rate and the current feed rate, and regulating the new feed rate as a function of the control signal.

One benefit of the invention is that the actual present feed rate is used as regulating parameter. It is both intuitively easier for an operator/service technician and time-saving, since the operator/service technician does not need to try out several different current values and then make a choice among them for each speed, but instead the system makes this setting automatically. Since the regulating is automatic, as compared to the actual present feed rate, it is possible to correctly adjust specific parameters for a specific drill rig with greater certainty.

In one embodiment of the invention, steps b-d are repeated. This is an advantage, since an iteration process can give a more accurate result. This makes it possible to successively adjust the control signal to a desired rate. Furthermore, this makes it possible to speed up the process, since the process is well controlled. In one embodiment of the invention, the control signal is calculated as a function of the difference between the current feed rate and the reference rate. Since the current feed rate is an actually measured feed rate, this enables a quick and effective adjustment of the system.

In one embodiment of the invention, the control signal is calculated as a function of the mean value of a plurality of consecutively determined values for the current feed rate and the reference rate. This makes it possible to filter out noise and any isolated abnormal value.

In one embodiment of the invention, the new feed rate is regulated so that it equals the reference rate or is lower than the reference rate. Then the rate is limited partly by the current drilling rate and partly by environmental conditions, for example, the drill bit passes through an air pocket in the rock, which causes the rate to increase suddenly and the motor accelerates quickly. Since the reference rate is an upper bound on the new rate, the motor does not accelerate in a way that would otherwise have been damaging to the drilling machine. The new feed rate is also limited by the physical drilling rate. This makes it possible to regulate the rate to avoid sudden accelerations of the drilling machine.

In one embodiment of the invention, the method further comprises PI regulation (proportional and integrating regulation) of the feed flow as a function of a refer- ence rate. This is an advantage, for example, when the control system regulates against a reference rate which is constant over a period of time.

In one embodiment of the invention, the method further comprises PID regulation (proportional, integrating and differentiating regulation) of the feed flow as a function of a reference rate. This is an advantage if the current rate increases and decreases suddenly and unpredictably, for example, due to the drill bit encountering cavities or air pockets in the rock or loose rock material.

In one embodiment of the invention, the method further comprises regulating the new feed rate so that it is within an interval containing the reference rate. This is an advantage when a relatively constant drilling rate is needed. A typical value for the interval is ±5% of the reference rate. An even tighter interval is preferable. In one embodiment of the invention, the control signal is taken from a reference table in dependence of the reference rate.

In one embodiment of the invention, the current feed rate is determined as a function of a change in position of the impulse-generating device relative to the sup- port means. In one preferred embodiment, the current position is measured with a position transmitter. This is an advantage, since drill rigs are easily outfitted with position transmitters in order to indicate the position of the sled on the feed beam. The current speed is calculated, for example, as a function of a change in position during a measured period of time.

In one embodiment of the invention, the current speed is determined by calculating the acceleration of the impulse-generating device. This makes use of an accel- erometer, for example, to determine the acceleration, and then the speed is computed as a function of the output signal from the accelerometer.

In one embodiment of the invention, the current rate is measured with a speed transmitter. It is easy to outfit a sled or feed beam with a speed transmitter and connect this to the control unit.

In one embodiment of the invention, a flow-regulated feed pressure regulates the movement of the impulse-generating device along the support means, the flow being regulated as a function of the control signal. This makes it possible to con- trol the motion of the drilling machine with a hydraulic valve.

In one embodiment of the invention, the method further comprises regulating the feed flow. This makes it possible to control the motion of the drilling machine with an electrically controlled hydraulic valve, for example. In another embodiment, a hydraulic pilot can also be used to control the hydraulic valve.

The invention also includes a computer program directly downloadable into a computer's internal memory, which program comprises program code to control a method according to method claims 1-9 of the invention. The invention, furthermore, involves a computer-readable medium with a recorded computer program, which is designed to make a computer carry out the steps according to any one of claims 1-9. The invention furthermore involves a drill rig, comprising a computerised control system, according to claim 20.

Advantageous modifications of the invention will appear in the following specification and the patent claims.

Description of figures

The invention shall be explained more closely with sample embodiments making reference to enclosed figures, where

Figure 1 shows a rock drilling rig according to one embodiment of the invention, Figure 2 shows a feed beam with drilling machine on the drill rig of figure 1 in more detail,

Figure 3 shows a regulating system according to one embodiment of the invention,

Figure 4 A shows a computer display of the prior art, Figure 4B shows a computer display according to one embodiment of the inven- tion,

Figure 5 A shows a flow chart according to one embodiment of the invention, Figure 5B shows a further flow chart according to one embodiment of the invention.

Description of sample embodiments

The following specification describes an underground rig, but the invention can also be applied above ground.

Figure 1 shows a rock drilling rig 10 for tunnelling, ore mining, or installation of rock reinforcing bolts, e.g., when tunnelling or mining. The drill rig 10 includes a boom 11, whose one end 1 Ia is hinged to a support means 12, such as a vehicle, via one or more links, and at whose other end 1 Ib is arranged a feed beam 13 which carries an impulse-generating device in the form of a drill machine 14. The drill machine 14 can move along the feed beam 13, and it generates shock waves which are transmitted by a drill string 15 and a drill bit 18 to the rock 17. The rig 10 furthermore comprises a computerised control system, having a control unit 16, which can be used to control the drilling parameters according to the invention, as shall be described below. The control unit 16 can be used to monitor position, direction and drilled distance, etc., with respect to the drill machine and support. The computerised control system can also be used to move the rig 10, even though of course a separate control unit can be used for this. The computerised control system is also used to monitor position, direction and drilled distance, etc., with respect to the drill machine and support.

Figure 2 shows the feed beam 13 with the drilling machine 14 in more detail. The drilling machine 14 is secured to a sled 20 movable along the feed beam 13, whose movement along the feed beam 13 is controlled by a feed cylinder 22, which in this example is a hydraulic cylinder. An alternative for driving the drilling machine 14 forward is to use a so-called chain feed, where the feed cylinder is replaced by a hydraulic gear motor, which is mounted furthest back on the feeder. Thanks to a chain, which is secured to the sled, and a gear at the very front of the feeder, the sled with drilling machine moves forward and back. When drilling, the feed beam 13 is placed in the drilling position, preferably with the drilling machine 14 moved as back far as possible to allow a drill string component 24, in said drill string 15, to be coupled to the drilling machine via an adapter 26 comprised in the drilling machine 14. The adapter is fastened by one end to the drill- ing machine 14 and at its other end provided with means, such as threads (not shown), for connection to the drill string component 24. In this way, the drill bit 18 is located relatively close to a front drill support 27 arranged at the feed beam 13. At the farther end of the feed beam, there is also arranged a hose drum 28 in this case, which controls hoses for supply of to the various units of the drilling machine 14 during the drilling. After the drilling advances, the feed cylinder will push the drilling machine toward the rock so that, when the sled 20 is moved toward the rock into a forward end position, it is released from the drill string component which has bored into the rock so that a new drill string component of suitable length can be connected between the drilling machine and the drill string component 24, whereupon the drilling can continue until a hole of desired length is obtained. If the drill string component 24 itself provides the desired hole depth, of course no further drill string component is needed. On the feed beam 13 of the support there is mounted a position transmitter, not shown in the figure. The position transmitter measures the position of the sled 20 and, thus, the drilling machine 14 relative to the feed beam 13 and sends the position data to the control unit 16. The control unit 16 calculates how long a length has been drilled with the help of the position data.

Figure 3 shows a schematic embodiment of a regulating system 30 which regulates a drilling machine 31. The drilling machine 31 is arranged on a sled which can slide on a feed beam 32. The regulating system 30 comprises a control unit 33 for regulating the movements of the drilling machine 31. A feed cylinder 35 is arranged at the beam to regulate the movement of the sled and thus the drilling machine, the drilling rate, forward and backward along the feed beam 32, by regulating the movements of the feed cylinder 35. On the piston rod 35a of the feed cylinder 35 there is fixed a cable wheel 37 in the direction of movement of the feed cylinder. The cable wheel 37 drives a cable 38, which is attached to the feed beam at one end 38a and to the sled at its other end 38b. Thus, the feed cylinder 35 is designed to regulate the movements of the drilling machine 31 forward or backward in that the feed cylinder drives the cable wheel 37 to rotate clockwise or anticlockwise. Instead of moving the drilling machine with a cable wheel and a cable, a cogwheel and a chain can also be used. Cable operation is preferred when using a feed cylinder 35. When using a hydraulic motor, chain operation is preferred.

The control unit 33 thus controls the movements of the drilling machine 31 by regulating the movements of the feed cylinder 35. When setting up the control system in this embodiment, the operator 39 enters various drilling parameters, such as feed pressure, and various reference speeds for different applications of the drill rig, into the control unit 33 via a display (not shown). An electronically controlled hydraulic valve 40 is connected to the control unit 33. The control unit 33 controls the movements of the drilling machine by controlling the flow q from the electronically controlled hydraulic valve 40 to the feed cylinder 35. The elec- tronically controlled hydraulic valve 40 is connected to the feed cylinder so that it regulates the movements of the piston rod 35a of the feed cylinder 35. The flow q is controlled by maintaining constant pressure difference Δp across the valve, so the flow q stays directly proportional to the opening area A of the valve. The feed flow q is current-regulated, so that the opening area A of the hydraulic valve 40 is proportional to a control current.

The hydraulic valve 40 is arranged at a tank 41. The pressure difference is equal to the pressure difference of the flow from the hydraulic valve 40, i.e., the pressure going to the feed cylinder p2, and the pressure pi of the flow to the hydraulic valve 40:

Δp = p2 - pl (2)

The feed pressure p2 is limited to a maximum desired feed pressure with a hy- draulic valve 42. The hydraulic valve 42 is controlled by the control system 33. The hydraulic valve 42 is arranged at the tank 41. The system pressure limits the maximum feed pressure that can be obtained. The system pressure is regulated with a pump, operated by the main motor of the drill rig, in this case, a diesel motor 36. It can also be an electric motor, especially when the rig is an underground rig.

The pressure difference Δp across the electronically controlled hydraulic valve 40 is kept basically constant by controlling the pressure pi to the valve with a mechanical pressure-regulating valve 43. The pressure difference Δp across the electronically controlled hydraulic valve 40 is controlled by controlling the pressure to the hydraulic valve 40 by controlling the pressure pi with a pressure-regulating valve 43.

Moreover, on the feed beam 33 of the rig there is a position transmitter 45, designed to determine the position X of the drilling machine relative to the feed beam. The position transmitter 45 is connected to the control unit 33. The position transmitter 45 sends information about the position X of the drilling machine to the control unit 32. Based on the ongoing position of the drilling machine, the control unit calculates how long the drilling has gone on. The control unit 33 is also outfitted with a time-recording device. In this embodiment, the control unit 33 calculates the change in position of the drilling machine as a function of in- formation from the position transmitter 45 and the time-recording device, and then a current feed rate. Depending on the desired reference rate and the current feed rate, the control unit 33 computes a control signal S. The control unit then automatically computes a new feed rate for said impulse-generating device in dependence on the control signal S. The reference rate is taken, for example, from the drilling parameters for the present application or from a previously measured value for the present application. Finally, the control unit 33 computes a control current S in dependence on the control signal S. The control unit 33 automatically regulates the hydraulic valve 40 by regulating the control current of the valve so that the flow across the valve changes to correspond with the new feed rate of the drilling machine.

The control unit 33 in this case regulates the new rate as a PID regulator, but of course it can also regulate the new rate as any other type of regulator, such as a PI regulator, or an adaptive regulator.

If the feed cylinder is replaced by a hydraulic gear motor in another embodiment, not shown, the drilling machine is driven forward by using a so-called chain feed. The sled with drilling machine is driven forward and back along the beam by a chain fixed to the sled and driven by the hydraulic motor, running along the feed beam. The electronically controlled hydraulic valve here is connected to the control unit 33. The control unit in this case controls the movements of the drilling machine by controlling the flow q from the electronically controlled hydraulic valve to the hydraulic motor. The electronically controlled hydraulic valve is connected to the hydraulic motor so it regulates the movements of the hydraulic motor's piston rod. The flow q is controlled in the same way as described above, by maintaining constant pressure difference Δp across the valve, so that the flow q is directly proportional to the opening area A of the valve. The feed flow q is current-regulated, so that the opening area A of the hydraulic valve is proportional to a control current.

In a first embodiment of a drilling application, limited control is exercised: the operator determines for this application a maximum speed for the drilling ma- chine as a reference speed. When the current feed rate approaches the given maximum speed, the control unit computes a new control current designed to choke the flow from the hydraulic valve, thus braking the feed cylinder. In this way, the control unit ensures that the speed does not increase further. When the speed drops, the control unit further computes and sends a new control current to the hydraulic valve so that its opening increases to prevent a worsening of the drilling. In this embodiment, where a maximum speed is allowed, the maximum speed is not attained when drilling in solid rock, since the penetration rate through the rock limits the drilling rate. Only when the drilling machine encounters cavities or easily bored parts of rock the feed rate can increase too fast and the control unit initiates a limiting of the speed when it approaches the given maximum speed. This protects the equipment from having too high a speed or accelerating too fast, or else the equipment might break or cuttings might clog the drill bit or the drill bit might get stuck, since the flushing agent used to remove the cuttings will drain away through cracks in the rock.

In another embodiment of a drilling application, a desired speed is regulated: the operator indicates a particular mean speed as a reference speed for the feed rate. This means that if the current rate is too low, the control unit 33 increases the modulation of the hydraulic valve 40. Moreover, if the current rate is too high, the control unit diminishes the modulation of the hydraulic valve 40. This control algorithm is suitable, for example, during entry and exit of the drill steel. It is important then to maintain a predetermined speed so as not to needlessly wear out the threads. The drilling machine is then controlled so the new speed is within an interval. A typical interval is reference rate of ±5%. An even tighter interval is advantageous.

In another embodiment, the control signal is rough-regulated by furnishing the control unit a reference table, giving a specific valve modulation for a particular feed rate. The control unit then fine-tunes the current rate by regulating the control signal during operation of the drill rig.

In another embodiment, not shown, instead of the position transmitter an acceler- ometer (not shown) is arranged at the feed beam to determine the acceleration of the drilling machine relative to the feed beam and the current feed rate is then cal- culated as a function of said acceleration.

In yet another embodiment of a drilling application, one uses a calibration func- tion carried out in the computerised control system or in an external computer to enter a reference table. The calibration is done when the rig is new and when a component of the rig is replaced.

In yet another embodiment of a drilling application, the rig is driven in an "emer- gency situation", for example, if the position transmitter breaks. One then uses a reference table, in the same way as described above. To be sure, this does not give the same correct speed, but still a sufficiently accurate setting to allow for continued drilling with the rig, such as until spare parts arrive.

Figure 4A shows two computer displays 50a, 50b of the prior art, where reference parameters are entered as starting parameters, for example, various feed pressures (bar) and various current values (rnA) representing different rates for different applications of the drill rig, taken from a reference table. Various drilling parameters can be the maximum feed pressure, minimum feed pressure, desired feed pressure during drilling, feed pressure during collaring, current for calibration, current corresponding to maximum forward speed, current corresponding to minimum forward speed, current corresponding to forward drilling speed, current corresponding to backward drilling speed and/or current corresponding to maximum collaring speed.

Figure 4B shows two computer displays 50c, 50d according to one embodiment of the invention, where an operator enters starting parameters, such as various feed pressures (bar) and various speeds (m/min) for different applications of the drill rig. Various drilling parameters can be the collaring feed pressure, the desired feed pressure during drilling, maximum feed pressure during drilling, minimum feed pressure during drilling, calibration speed, desired drilling speed, col- laring speed, maximum forward speed, and/or maximum backward speed. Other drilling parameters are also possible.

Figure 5 A shows a flow chart for a method of control of at least one drilling parameter when drilling rock, wherein an impulse-generating device drills the rock with a striking means designed to induce shock waves in a tool acting on the rock. The impulse-generating device can be moved in the drilling direction relative to a supporting means. The impulse-generating device is arranged with a control unit. The method comprises the following steps:

a) A first drilling parameter is set by determining a reference speed, in that the operator enters a value for the reference speed manually into the control system, or the control unit automatically fetches the reference speed from a reference ta- ble (60).

b) A second drilling parameter, a current feed rate, is determined (61). The current feed rate is a measured value for the rate or a computed value for the rate depending on a measured value for the acceleration.

c) A control signal is computed as a function of the reference speed and the cur- rent speed by a predetermined computing method in the control unit (64). The computation method can be one of the variants of PI or PID regulation or adaptive regulation. The control signal can also be computed as a function of the difference between the absolute magnitude of the current feed rate and the desired feed rate.

d) A new feed rate is automatically regulated as a function of the control signal.

In one embodiment, the control signal regulates a valve, which controls the movements of the impulse-generating device relative to a support means (66).

Figure 5B shows a flow chart for another embodiment of the method for controlling at least one drilling parameter when drilling rock. The method comprises the above steps and the following step:

e) Steps b-d are repeated (68). This is done, for example, until the new speed is within a preferred interval of the reference speed. In another embodiment, this step is executed so that the new speed approaches the reference speed without going over it.

In a physical implementation of the control unit, it comprises a logic unit, a com- puter unit or a calculator unit comprising a microprocessor or processors comprising a CPU (Central Processing Unit) or a FPGA (field-programmable gate array) or some other semiconductor unit comprising programmable logic components and programmable circuits to carry out the method according to one aspect of this invention. This is done with the help of one or more computer programs saved at least partly in a program memory which the control unit has access to. The computer program comprises program code elements or software that can make the computer carry out the method by using equations, algorithms, data and computations as previously described.

The invention is not limited to the sample embodiments shown, but the person skilled in the art can of course modify it in many ways within the scope of the invention defined by the patent claims. Thus, for example, instead of a position transmitter, one can use a speed transmitter, wherein a special transmitter indicating the speed of the drilling machine is arranged at the feed beam. Moreover, the movements of the drilling machine can be controlled hydraulically or pneumatically, instead of electrically. Various feeder designs can be used, e.g., with electric motor or with a ball screw.

Claims

1. A method for control of a feed rate of a rock drilling machine ( 14, 31 ), when drilling rock (17), wherein the rock drilling machine is arranged with a con- trol unit (33), characterised in that the method comprises: a) entering a reference rate in the control unit, b) automatically regulating the feed rate for as a function of the reference rate.

2. The method according to claim 1, wherein the method further comprises: a) determining a control signal (S) as a function of the reference rate, b) regulating the feed rate as a function of the control signal.

3. The method according to claim 2, wherein the method further comprises: a) determining a current feed rate, b) calculating the control signal (S) as a function of the reference rate and the current feed rate.

4. The method according to any one of claims 2-3, wherein the control signal (S) is calculated as a function of the difference between the current feed rate and the reference rate.

5. The method according to any one of claims 2-4, wherein the reference rate is obtained from a reference table (50a-d) in dependence of the reference rate.

6. The method according to any one of claims 2-5, wherein the control signal (S) is also calculated as a function of the mean value of a plurality of consecutively determined values for the current feed rate and the reference rate.

7. The method according to any one of claims 1-6, wherein the new feed rate is regulated so that it is lower than or equal to the reference rate.

8. The method according to any one of claims 1-7, wherein the new feed rate is regulated so that it is within an interval comprising the reference rate.

9. The method according to any one of the preceding claims, wherein the reference rate is obtained from a reference table (50a-d) giving a specific valve modulation for a given rate.

10. A computerised control system for controlling of a feed rate for a rock drilling machine when rock drilling, wherein the control system is arranged with a control unit, characterised in that the control system also comprises: a display for entering a reference rate in the control unit, wherein the control unit is arranged so that it is automatically regulating the feed rate for the rock drilling machine as a function of the reference rate.

11. A computerised control system according to claim 10, wherein the control system further comprises means for determining a current feed rate, and a calculating unit arranged to calculate a control signal (S) as a function of the reference rate and the current feed rate, and regulate the new feed rate as a function of the a control signal.

12. A computerised control system according to claim 11, wherein the current rate is measured with a speed transmitter.

13. A computerised control system according to claim 11, wherein the control system further comprises a position transmitter arranged to measure the current position (X) of the rock drilling machine, wherein the rock drilling machine can move along a feed beam in the drilling direction and the position transmitter is arranged at the feed beam (13,32) wherein the control unit calculates the current feed rate as a function of a change in position of the impulse-generating device (14, 31) relative to the support means (13, 32).

14. A computerised control system according to claim 11, wherein the control system further comprises an accelerometer, wherein the rock drilling machine can move along a feed beam in the drilling direction and the accelerometer is arranged at the feed beam (13, 32) and determines the acceleration of the rock drilling ma- chine (14,31) relative the feed beam, wherein the control unit calculates the current feed rate as a function of a said acceleration.

15. A computerised control system according any of claims 11-14, wherein a flow-regulated feed pressure regulates the movement of the impulse-generating device (14, 31) along the support means (13, 32), the flow (q) being regulated as a function of the control signal (S).

16. The method according to claim 15, wherein the method further further automatically regulating the feed rate as a function of a reference rate, according to one of the following regulation methods: PI, PID.

17. A computerised control system according to claim 16, wherein the method further comprises current regulation of the feed flow.

18. A computer program directly downloadable into a computer's internal memory, which program comprises program code to control a method according to claims 1-9.

19. A computer-readable medium with a recorded computer program, which is designed to make a computer carry out the steps according to any one of claims

1-9.

20. A drill rig comprising a computerised control system according to any of the claims 10-17.