WO2007073327A1

WO2007073327A1 - Control system and method for controlling a drilling rig

Info

Publication number: WO2007073327A1
Application number: PCT/SE2006/050558
Authority: WO
Inventors: Johan Larsson
Original assignee: Atlas Copco Rock Drills Ab
Priority date: 2005-12-23
Filing date: 2006-12-07
Publication date: 2007-06-28
Also published as: SE0502872L; SE531293C2

Abstract

The present invention is intended to reduce the effect of a backlash in a swivel joint (7) for rotation of a feeder (3) on a boom (2) in a drilling rig, when the feeder (3) is to be brought into a new spatial position, through a measure and means to rapidly rotate the drive member, at least in the swivel joint (7) which has the greatest susceptibility to said backlash, into a position in which further adjustment results in a physical movement of the feeder (3). This is achieved in that when a movement of the relevant swivel joint (7) is ordered by the control system, a control loop in the drilling rig control system is initiated, which for a short time adjusts and drives the drive member in the swivel joint (7) at a high rate of adjustment until a movement of the feeder (3) can be detected, following which the control system adjusts the entire movement of the boom (2) and the feeder (3) at the speed ordered by the control system.

Description

Control system and method for controlling a drilling rig

TECHNICAL FIELD

[001] The present invention relates to a control system for a drilling rig which comprises a carrier, a boom capable of rotating in relation to the carrier, and a feeder for a drilling machine connected to the boom via an angle unit, in which the position and direction of the feeder are adjusted by means of a rotation of the feeder by changing angle at least about a transverse axis to the longitudinal direction of the boom, and in which the control system is designed to eliminate the effect of a physical play in a swivel joint in the angle unit during the adjustment.

PRIOR ART

[002] When drilling in rock, as when tunnelling, for example, a drilling rig is commonly used, which includes a carrier, which may consist of a plant vehicle of suitable size. In order to be able to place a drilling machine arranged on the drilling rig in the desired position for drilling, the drilling machine is arranged on a feeder, which in turn is articulated on a moveable arm, commonly referred to as a boom. The boom is rotatably coupled to the carrier by way of articulated joints, so that the boom can be rotated, suitably about a vertical axis and a horizontal axis. Various sizes and numbers of booms can be constructed on a carrier. The design of the joints and the drive arrangement for the joints may vary. On larger drilling rigs an arm movement in the joints of the boom has traditionally been powered by means of tripods, in which two hydraulic cylinders and the driven arm in a joint are arranged as a tripod, so that the arm can be rotated in the required directions. This construction has the advantage of a constant load direction between the arms in a joint, the backlash in the joints being of no concern since the backlash is small or has only a negligible effect on an adjustment of the drilling machine.

[003] A front tripod construction has also conventionally been used in order to rotate the feeder in relation to the boom. In order to improve the accessibility when drilling, the feeder is furthermore rotatable about an axis in the longitudinal direction of the feeder. This latter joint is arranged in front of the front tripod and is used partly in order to rotate the feeder to a position in which a drilling rod on the feeder is fully visible to an operator during drilling, and partly in order to improve the accessibility when drilling close to the floor and tunnel walls.

[004] The conventional tripod construction for powering the arm in a joint has certain disadvantages, however. One of these is that a boom on a drilling rig equipped with said tripods becomes heavy. Another problem is that the tripods take up space. In order to cope with these and other disadvantages, a variant of the boom has been developed for smaller drilling rigs. This boom variant has a tripod on the rear part of the boom, that is to say where the boom is articulated on the carrier. In the front part a combination of two swivel joints and a joint operated by means of a hydraulic cylinder is used instead of a front tripod and the aforementioned feeder swivel joint. As stated, this configuration of the joints has been used previously, but only for smaller booms on small drilling rigs, in which there are no exacting requirements for precise adjustment of the feeder.

[005] In drilling by means of the drilling rig, the carrier is first stably positioned and fixed. The boom and feeder are then adjusted, either manually or by means of an electronic control system. The boom is adjusted, as required, in a horizontal and vertical direction by powering the hydraulic cylinders which are fitted in the tripod between the carrier and the boom and the first of the swivel units (having an axis of rotation which is parallel to the longitudinal direction of the boom) between boom and feeder, so that the feeder assumes the required position right at the front of the boom. The direction for the feeder is in turn adjusted by powering the front swivel unit together with the front hydraulic cylinder joint between boom and feeder, so that the drilling machine on the feeder can introduce a drill into the rock in a predefined spatial direction.

[006] In manual positioning of the boom use is often made of parallel displacement of the feeder, when the feeder has to be shifted from one drilling position to another. The front swivel unit and the front hydraulic cylinder joint on the boom are here set to rotate the feeder in relation to the boom in order to compensate for a rotation which the boom is required to make in relation to the carrier in order to shift the feeder to the new position. The compensation which is calculated is intended to maintain the spatial direction of the feeder whilst shifting the feeder to the new position.

[007] An electronic control system is capable of calculating and controlling the movements in the front joints in order to compensate for the rotations of the rear joints. Hydraulically powered mechanical systems are also used in applications, in which the precision requirements are limited. In order to be able to control the parallel displacement of the feeder electronically, all joints need to be equipped with sensors which continuously measure the rotational position of the arms in a joint. By reading off said rotational positions, a central control unit in the control system can be constantly updated with the rotational position for each of the arms in a joint. [008] In order to achieve an acceptable efficiency and service life, the gears, commonly planetary gears, which are used in the swivel joints, must have a certain play. This play gives rise to a backlash in a swivel joint, which means that a drive element, which is rotated by a drive member in the swivel joint, can move between a first and a second angle of rotation without an outgoing arm, which is to be rotated by the drive element in the joint moving, the angle between these constituting said play. The angle of the play may be in the order of 0.3°. The relationship between the angular position of the drive element and the arm running out from the joint gives rise to said backlash, which has an effect on the control mainly in two operating instances: 1. In movements in which the centre of gravity of rotatable units, which lie in front of the swivel joint in question, changes load direction, this will give rise to backlash.

2. When the direction of rotation of an arm, which is rotated by a swivel joint is changed, or when a rotation of the arm is initiated by means of a drive arrangement, the backlash must be made up for before the arm begins to move.

[009] Having such a physical play in the joints of a boom, which is intended for applications with high requirements as to performance and precision, is not satisfactory. By fitting a brake in the swivel joint, it is possible to eliminate the backlash in the first operating instance above, although it is considerably more complicated in the second instance.

[0010] Under certain circumstances in the second instance above, when a rotation of an arm is to be initiated, the arm may be situated in a limit position for the play, that is to say at the angle of rotation for the play in the joint remote from the direction of rotation to be described by the arm. In this case the backlash is equal to the full play. This manifests itself through the absence of any physical rotation of the arm until the entire backlash has been made up on commencement of the rotation of the arm in the joint in said direction of rotation (that is to say despite a drive member working to rotate a drive element in the joint). The problem is greatest in small adjustments, that is to say at low moving speeds, when it may take several seconds for the drive member of the swivel joint to make up the backlash which exists and to generate a physical movement of the arm in the joint which is to be rotated. The problem manifests itself primarily during manual positional adjustment with a need for parallel displacement of the feeder, when a slow lifting of the boom, and/or swivelling of the boom, must be compensated for by the control system through in some cases an even slower movement in the feeder, in which this has to be swivelled or raised in order to maintain the direction of the feeder during movement of the boom. The resulting absence of any movement by the swivel unit, due to the backlash, is very perturbing, since in the worst case the entire traversing movement may be performed before any compensation for parallel displacement of the feeder movements, that is to say alignment, of the feeder commences.

[0011] US 3,828,238 shows an example of a solution to the problem of play that occurs where a mechanical part is to be shifted to a required position. A servo system controls the movement. The solution means that the intensification in the servo system is instantaneously increased when a change in the direction of movement of the mechanical part is to be performed. The mechanical play will hereby be rapidly taken up, shortening the time lag in the control operation.

[0012] US 4 742 284 shows another variant for controlling a valve, for instance, which is driven by an electric motor, in which a lag occurs. The control is performed by means of motor control pulses. If the last movement performed by the motor occurred in an opposite direction to the required direction, the control pulse to the motor is prolonged in order to overcome the time lag caused by the reversal in the direction of rotation of the motor.

[0013] An object of the present invention is to find a solution to the disadvantages identified in the prior art.

SUMMARY OF THE INVENTION

[0014] According to one aspect of the invention an arrangement is described having the characteristics according to claim 1 attached.

[0015] According to a further aspect of the invention a method is described having characteristics according to the method claim attached.

[0016] Further embodiments of the invention are set forth in the dependent claims.

[0017] As will be apparent from the patent claims, one aspect of the invention is concerned with reducing the effect of a backlash in a swivel joint for rotating the feeder, when this is to be brought into to a new spatial position, by rapidly rotating the drive member, at least in the swivel joint which has the greatest susceptibility to said backlash, to a position in which further adjustment results in a physical movement of the feeder. This is achieved in that when a movement of said swivel joint is ordered by the control system, a control loop is initiated, which for a short time controls and drives the drive member in the swivel joint at a high rate of adjustment until a movement of the feeder can be detected, following which the control system controls the entire movement of the boom and feeder at the speed dictated by the control system.

[0018] Some advantages of the solution described are that:

- standard components can be used instead of special gears having an unreliable service life,

- the precision in adjusting drilling positions and drilling directions is improved,

- the swivel joints which are used take up less space than equivalent conventional hydraulic cylinders in a tripod structure,

- embodiment of the arrangement and the method according to the invention results in scarcely any additional product costs, since no additional hardware in the form of sensors and/or computer capacity is required, other than what is already needed for the conventional equipment for the parallel displacement of the feeder described in a drilling rig.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a schematic figure of a boom according to one aspect of the invention, in which the boom is equipped with a feeder provided with a rock drilling machine.

Fig. 2 shows a simplified representation of a linkage model which schematically describes the control and degrees of freedom of the boom and the feeder.

Fig. 3 is a flow chart which illustrates a control loop according to one aspect of the invention, in which a drive member brings a swivel joint to a limit position for the play in the swivel joint.

Fig. 4 shows a drilling rig equipped with a boom and a feeder.

EMBODIMENTS

[0019] A number of embodiments of the invention are described below with reference to the drawings attached.

[0020] Fig. 1 shows a sphere of application for the control system according to one aspect of the present invention. A carrier 1 for a drilling rig is merely symbolized by an arrow which indicates the direction for connection to the carrier of a boom 2. The carrier 1 may consist of a suitable plant vehicle. The boom 2 is articulated on the carrier 1. Hydraulic cylinders 2a, 2b are pivotally connected to both the carrier 1 and the boom 2 for manoeuvring the boom. Thus if the drilling rig plant vehicle is assumed to be fixed in a horizontal plane, the boom can swivelled in a horizontal direction about a vertical axis 1a (see fig. 2) and raised by an angle of elevation about a horizontal axis 1 b by means of the hydraulic cylinders 2a, 2b. These two movements of the boom are termed boom swivel and boom lift. A feeder 3 for a rock drilling machine 4 is shown right out at the end of the boom 2. The drilling machine 4 is of known type and will not be described further here.

[0021] A complete drilling rig is shown in Fig. 4 with carrier 1 , boom 2 and feeder 3. It can also be seen from the figure that the carrier 1 is situated in a fixed position for drilling in a drilling surface 9.

[0022] Fig. 2 schematically shows the degrees of freedom for the boom 2 and the feeder 3 in the form of a linkage model. The drilling rig, as will be seen from Fig. 2, has more axes and degrees off freedom than will be explained in this description. These further degrees of freedom are not relevant to the invention and will not be discussed further here.

[0023] An angle unit 5 is arranged between the boom 2 and the feeder 3. The angle unit 5 is designed with a first swivel joint 6 and a second swivel joint 7, fitted basically at 90 degrees to one another at each end of the angle unit. The first swivel joint 6 is here mounted against the boom 2, the angle unit 5 being rotatable by means of the first swivel joint about a longitudinal axis 6a to the longitudinal direction of the boom 2 (feeder rotation). A second swivel joint 7 of the angle unit 5 is correspondingly fixed against the feeder 3, the feeder 3 being rotatable by means of the second swivel joint 7 about a transverse axis 7a to the longitudinal direction of the boom (feeder swivel). A drive member is applied inside each of the swivel joints so that an arm running out from the joint is rotated. The drive member suitably comprises an electric, electro-hydraulic or hydraulic motor.

[0024] Both the first swivel joint 6 and the second swivel joint 7 are of mechanical construction and thereby exhibit a play which is characterised by an angular range of a drive element in the swivel joint between two angles of rotation, which constitutes limit positions for the play exhibited. When the drive element, which drives an arm running out from the swivel joint, is at an angle of rotation situated between said limit positions, the outgoing arm will not be rotated by the drive member until the drive element in the joint has been rotated to the play limit position, that is to say no physical movement will be exhibited by the outgoing arm until the drive member and outgoing arm have direct mechanical contact in the current direction of rotation.

[0025] Since keeping the feeder parallel when moving the drill to new drilling positions is mainly influenced by backlash in the feeder pivot joint, that is to say the swivel joint 7, under this aspect of the invention measures for reducing the effect of backlash varying as a function of the play will be discussed here only with reference to the swivel joint 7. There is obviously nothing to prevent the play in other swivel joints being addressed in a similar way to that described here.

[0026] The disadvantage of the play in the second swivel joint 7 has greatest effect in manual positional adjustment of the feeder 3 and above all in parallel displacement of the feeder 3 during rotation of the boom 2. The aim of a parallel displacement of the feeder movement is to shift the tip 3a of the feeder 3 to a new position in which a new hole is to be drilled on a drilling surface and where the spatial direction is to be maintained for the feeder 3 and the drilling machine 4. The parallel displacement of the feeder movement is characterised in that an operator gives a control command via a control device, which consists, for example, of a joystick, a control ball or other man-machine interface. This control command is translated into signals in the control system and causes the boom 2 to rotate about an axis 1a and/or 1b and/or 6a, that is to say the boom swivel and/or boom lift and/or feeder rotation are activated so as to cause the feeder 3 to be shifted in the required direction to a new position. At the same time the front joints, in this case the second swivel joint 7 and a feeder tilting joint 8 must be made to rotate in order to compensate for the rotation of the rear joints on the axes 1a, 1b and/or the first swivel joint 6 on the axis 6a, in order that the direction of the feeder 3 will at all times be parallel to the direction of the feeder before movement commenced.

[0027] For the sake of simplicity, movement of the outgoing arm in the swivel joint 7 is in this description termed or equated with the feeder movement in its entirety. In the feeder 3 multiple swivel joints may be present on said outgoing arm. Telescopic displacement also occurs in the feeder. These other swivel joints and displacements will be ignored when describing the parallel displacement of the feeder 3.

[0028] One aspect of the invention is that when a movement of the drilling rig units commences, or changes direction in order to locate the feeder tip 3a at a new point on the drilling surface 9, where a swivel joint exhibits said play, use is made of the fact that the position of the feeder 3 in the swivel joint will be known. This can be established by determining the angular position of the feeder in the joint at the outset, that is to say its starting angle. Since it is impossible for the control system to know beforehand whether an activation of the swivel joint drive member will immediately result in a movement in the swivel joint, causing the outgoing arm in the joint to move (in this case an arm coupled to the feeder 3) or will initially only make up for the backlash, sensors are used in the joint in order to permit measurement of the angular position of the feeder 3 in the swivel joint (the sensor measures the true angle of rotation in the joint between a rear fastening of the swivel joint and the arm running out from the joint, that is to say irrespective of any backlash in the joint). Thus when a rotation of the swivel joint is ordered by the control system, the angular position of the feeder is read off, following which the drive member rotates the swivel joint in the direction of rotation ordered, until a movement of the outgoing arm in the swivel joint causing the feeder to be rotated in this direction of rotation can be detected at a time to. At the time t₀ the backlash has therefore been made up and further rotation of the drive member will produce movement of the feeder 3.

[0029] Since the backlash due to play in the joint is perceptible only in the case of slow movements, the function for reducing the effect of the backlash according to this aspect of the invention may be limited to activation solely when the rate of adjustment for the backlash- compensated swivel joint lies below a specific limit.

[0030] The course of events for controlling a swivel joint according to the aspect of the invention is set out in the flow chart shown in Fig. 3. Measures relating to the second swivel joint 7 will be described here by way of example, but corresponding control can be applied to other swivel joints. In box 11 it is specified that the control system receives input data for control of the boom 2 and the feeder 3 from a control element, such as a joystick which is manoeuvred by an operator, or from a control routine. In the next step, in box 12, it is analysed whether a control loop (according to box 13, 14, 15, 16, 18, 19) for reducing the effect of backlash in the swivel joint is to be activated. If, as stated, the rate of adjustment in the swivel joint in question exceeds a set limit, the control loop is not activated, all joints in the boom 2 and feeder 3 without delay being adjusted according to input data which are delivered to and stored in the control system. If, on the other hand, the limit values show that the control loop is to be activated, the control system reads off and stores the angular position of the outgoing arm in the joint, according to box 13, that is to say the outgoing arm in the joint which directly affects the movement of the feeder 3. Thereafter the drive member of the swivel joint, box 14, is made to rotate a drive element in the joint in the required direction of rotation. At brief time intervals, a new angular position of the outgoing arm in the swivel joint is read off and stored, according to box 15, in order to allow detection of the time to, at which the outgoing arm exhibits a rotation. A condition is examined, box 16, after each new read-off of the angular position according to box 15 to see whether the condition is fulfilled, that is to say whether the outgoing arm is just starting to move and the time t₀ is reached. If the condition according to box 16 is fulfilled, the control loop is abandoned and the control returns to the main program, the control routine adjusting all joints according to box 17.

[0031] A flag, M, is used in order to determine whether the backlash in the joint has yet been made up. This flag M is set to false in box 12 if the required direction of rotation for the joint has been changed or was previously zero. The flag M then acquires the true value if the answer "yes" is obtained in box 16, that is to say it the joint has begun to move.

[0032] If the condition in box 16 is not fulfilled, it is examined in the control loop whether original control data still apply. For example, an operator may have changed the prerequisites for the control by inputting new control data. In order to examine this, input data are collected according to box 18, following which the program in box 19 analyses whether these data are unchanged. If the input data are unchanged the control loop reverts to continued adjustment, according to box 14, of the drive element in the swivel joint in the required direction of rotation for acting upon the outgoing arm in the joint. If, on the other hand the input data have changed, the entire control sequence will have been changed, the control according to the control program returning to the entrance to box 12, that is to say in order to re-determine whether the control loop is to be run by the control program.

[0033] The rate of adjustment while the program is running the control loop is high, so that any backlash is made up in a short time, which means that the waiting time until the backlash has been made up will be short, so that the control of all joints can be performed in a predefined way with little delay. Reducing the effect of backlash in the manner demonstrated by means of a software solution according to the invention, means that the hardware in the form of the boom 2 and the feeder 3 with associated joints will be free from backlash.

[0034] In the description and the patent claims the rotations performed by the feeder have been described as being performed around the longitudinal axis (6a) of the boom, or its transverse axis (7a). If it is thought desirable, there is nothing to prevent rotation of the feeder (3) at an angle which deviates from the longitudinal axis of the boom by an angle of deviation, for example, of 20 degrees. Similarly, the rotation of the feeder can be designed to occur about an axis which deviates from the transverse axis by a desired angle of 20 degrees, for example. Such deviations must be deemed to be included in the term longitudinal axis of the boom or its transverse axis. The only complementary additions that need to be made in the event of such angular deviations are revisions to the programming of the control for the drilling rig, in which compensation for such deviations is incorporated into the program.

Definitions: In the present text: Play: refers to the angle of rotation of a drive element in a swivel joint between a first angular position and a second angular position, between which an outgoing arm in the swivel joint is not rotated by the drive element. Backlash: refers to the angle of rotation of the drive element in the swivel joint between its current angular position and its angular position in the direction of rotation at which an outgoing arm begins to be rotated by the drive element.

Claims

PATENT CLAIMS

1. Control system for a drilling rig which comprises: - a carrier (1), - a boom (2) suspended on the carrier (1) and arranged so that it can rotate in relation to the carrier (1),

- a feeder (3) for a drilling machine (4) arranged on the boom (2),

- at least one swivel joint (7) arranged between the boom (2) and the feeder (3), by means of which the feeder (3) can be rotated in relation to the boom (2) and where said swivel joint (7) exhibits a play on rotation of the feeder (3); in which the control system is further designed to adjust a position, which comprises a position and a direction for the feeder, through at least one of the following:

- a rotation of the boom (2) in relation to the carrier (1 ),

- a rotation of the feeder (3) in relation to the boom (2) by means of a rotation of the swivel joint (7) in a first direction of rotation, characterised in that:

- the control system is designed with a control loop which, before the control system steers the feeder (3) from a first position to a second position, causes the swivel joint (7) to perform a rotation in the first the direction of rotation until a limit position for said play is detected in the swivel joint (7).

2. The control system according to Claim 1 , in which the detection of said play is achieved by means of a sensor in the swivel joint (7), in which the sensor measures a true angle of rotation in the joint between a fastening of the swivel joint (7) and an arm running out from the swivel joint (7), which in this case is an arm which adjusts the feeder (3).

3. The control system according to Claim 1 , in which the second the swivel joint (7) comprises a drive member, which by means of control signals causes a drive element to rotate the feeder (3).

4. Method for controlling a drilling rig, which comprises: - a carrier (1),

- a boom (2) suspended on the carrier (1) and arranged so that it can rotate in relation to the carrier (1), - a feeder (3) for a drilling machine (4) arranged on the boom (2),

- at least one swivel joint (7) arranged between the boom (2) and the feeder (3), by means of which the feeder (3) can be rotated in relation to the boom (2), and where said swivel joint (7) exhibits a play in rotation of the feeder (3);

in which the method is characterised by steps in which: - the drilling rig is made to assume a position, which comprises a position and a direction for the feeder (3), through at least one of the following: a rotation of the boom (2) in relation to the carrier (1), a rotation of the feeder (3) in relation to the boom (2) by means of a rotation of the swivel joint (7) in a first direction of rotation and - before shifting the feeder (3) from a first position to a second position, the swivel joint (7) is made to perform at least one rotation in the first direction of rotation until a limit position for said play in the swivel joint (7) is detected.

5. The method according to Claim 4, further comprising the step in which: - shifting of the feeder (3) to a new position is performed by means of control signals which are generated by a control device or a control routine.

6. The method according to Claim 5, further comprising the step in which:

- the control activates a control loop (13, 14, 15, 16, 18, 19) if a backlash is present in the second swivel joint (7).

7. The method according to Claim 6, further comprising the step in which:

- the control loop drives a drive element intended for rotation of the feeder (3) in the swivel joint (7) in the first the direction of rotation, - the control loop regularly detects whether the feeder (3) has moved.

8. The method according to Claim 7, further comprising the step in which:

- if the control loop detects a movement of the feeder (3), the control is given over to the control loop and further control of the drilling rig is performed by way of the control signals.

9. The method according to any one of Claims 6 to 8, further comprising the step in which:

- it is detected within the control loop whether the control signals have changed, - on detection of modified control signals the control reverts to the step in the method according to Claim 5.

10. Drilling rig comprising a carrier (1) with at least one boom (2), which at its front end supports a feeder (3) for a drilling machine (4), characterised in that the drilling rig is equipped with the control system according to Claim 1.