GB2522922A

GB2522922A - Electronic guard systems

Info

Publication number: GB2522922A
Application number: GB1402321.2A
Authority: GB
Inventors: James Michael Unsworth; Bradley Fraser Jepson
Original assignee: HIGH MEAD DEVELOPMENTS Ltd
Current assignee: HIGH MEAD DEVELOPMENTS Ltd
Priority date: 2014-02-11
Filing date: 2014-02-11
Publication date: 2015-08-12
Also published as: WO2015121634A1; GB201402321D0

Abstract

A drilling rig 100 having a safety monitor 108 to detect the presence of a person within a first predefined volume 110, the monitor being responsive to influence the operation of the drive control system, for example by preventing the drive control system from operating or starting. The monitor may also be responsive to detecting a person within a second volume 116 by producing an audio or visual warning. The monitor may comprise a camera and light projector. Also independently claimed is a monitor for detecting the presence of a person within a volume relative to a vehicle.

Description

Electronic Guard Systems Embodiments of the invention relate to electronic guard or safety systems and can find application in respect of, for example, drilling rigs and associated monitoring systems.

Drilling rigs are known in which a safety cage comprising a number of laser beams and associated detectors are arranged to fence-off a drill. If a laser beam is interrupted, a rotary head drive control system associated with a drill bit or auger immediately terminates drilling.

It can be appreciated that such a safety cage is effective at preventing injury to a person who has inadvertently strayed too close to an operating drill.

However, such a safety cage has the disadvantage that spoil from drilling can also interrupt a laser beam and thereby immediately end drilling operations even though a person is not sufficiently proximate to the auger to be in danger.

Accordingly, embodiments provide a drilling rig comprising a carrier/drill string for carrying a drill having a drilling axis; the rig comprising a monitor for detecting the presence of a person at least partially within a predefined volume relative to the drilling axis, the monitor being responsive to detecting a person within the predefined volume to influence operation of a drive control system for actuating the drill.

Suitably, drilling operations are not inadvertently terminated other than when a person is detected as having an unacceptable proximity to the drill. Furthermore, drilling operations are not commenced when a person is unacceptably proximate to the drill.

Embodiments will now be described, by way of example only, with reference to the accompanying drawings in which: figure 1 shows a drilling rig; figure 2 depicts a monitoring system; figure 3 illustrates a drilling rig control system; figure 4 shows a light pattern; figure 5 illustrates a depth determination technique; figure 6 shows a predefined volume; figure 7 illustrates a second depth determination technique; figure 8 depicts further details of the second depth determination technique; figure 9 shows a flow chart of processing.

Figure 1 shows a drilling rig 100 comprising a Kelly bar/drilling string 102 carrying an auger 104, drill bit or the like. Preferred embodiments are realised using an auger 104 that can be moved in a reciprocating manner on the Kelly bar 102. The auger 104 contains a flight 106 that accumulates spoil during drilling. When the auger 104 is raised, spoil within the flight 106 is also raised. The spoil is spun-off the flight 106 when the auger 104 is rotated above ground level.

The drilling rig 100 also comprises at least one monitoring system 108 arranged specifically to detect a person who is unacceptably proximate to the auger 104 and, more particularly, to detect a person within a predefined volume 110 associated with the auger 104 to influence the operation of the drilling rig 100. It can be appreciated that this is in contrast to merely detecting an interruption in a laser beam, which could relate to spoil as opposed to a person.

A monitoring system is an embodiment of a monitor.

The Kelly bar 102 is driven or actuated by a rotary head 114. The rotary head 114 is, in turn, controlled by a drilling rig control system, which is described below with reference to figure 3.

Referring also to figure 2, there is shown a view 200 of the monitoring system 108. The monitoring system 108 is arranged to illuminate the predefined volume 110 with a light pattern 202. Preferred embodiments use infrared light for the light pattern 202. The light pattern 202 comprises a light pattern axis 204. Furthermore, the light pattern 202 comprises reference indicia (not shown in figure 2). The light pattern 202 is produced using a light source 206, to supply the light, and a diffractive optical element 208 to pattern the light. The light, although illustrated in 2D, is arranged by the diffractive optical element 208 to span a volume that progressively diverges. Therefore, it will be appreciated that the light pattern 202 progressively diverges.

The monitoring system 108 also comprises a camera 210 for detecting reflected light associated with the light pattern 202. Preferred embodiments use an infrared filter 210' in conjunction with the camera 210 to ensure that the image detected by the camera 210 relates only to reflected light associated with the light pattern 202. The camera 210 has a field of view 212. The field of view 212 has a central axis 214. The field of view 212 is arranged to overlap with the light pattern 202. The region or volume of overlap corresponds at least in part with the predefined volume 110 such that the camera 210 is able to capture image data associated with light reflected from any object, within the predefined volume 110, that has been illuminated with the light pattern 202.

An image detected by the camera 210 is passed to an image processor 216. The image processor 216 comprises a filter 218. The filter 218 is arranged to determine at least whether or not an image relates to a person. Embodiments can use one of a number of skeleton tracking algorithms as are known in the art to implement the filter 218. For example, embodiments can use the skeleton tracking algorithm disclosed in Real-Time Human Detection in Uncontrolled Camera Motion Environments by Hussien M. et al, Institute for Advanced Computer Studies, University of Maryland, available from ht.tri!/www. umiacs. urnd.edu/-wamageed!papershcvs2006.pdf, which is incorporated herein for all purposes and a copy of which is included in the appendix. Preferably, an indication that an image relates to a person is output by the image processor 216 to a monitoring system controller 222.

Embodiments also output image data associated with the person to a depth analyser 220.

The image data processed by the depth analyser 220 comprises reference indicia of the light pattern 202 associated with that person.

The image data comprising the reference indicia associated with the person is processed to determine a position of that person. Preferably, such position determination comprises identifying at least an indicium of the reference indicia and preferably a subset of indicia from reflected light associated with the light pattern 202 and the person. The identified indicium is, or subset of indicia are, processed to determine such a position, such as, for example, a normal distance, or other position vector, of the indicium from a reference plane 226 containing the camera 210 and the diffractive optical element 208.

The determined position vector or normal distance is output to the monitoring system controller 222. The monitoring system controller 222 processes the determined distance to determine whether or not the person associated with the determined distance is within the predefined volume 110. If the monitoring system controller 222 determines that such a person is not within the predefined volume 110, no action is taken or an output to that effect is produced for communication to the drilling rig system controller 302. If the monitoring system controller 222 determines that such a person is within, or at least partially within, the predefined volume 110, then a communication 224 to that effect is sent to the drilling rig system controller 302, which is described with reference to figure 3.

Referring to figure 3, there is shown schematically a view of a control system 300 for the drilling rig 100. The control system 300 comprises a drilling rig system controller 302 that controls the actuation of one or more than one valve for operating the rotary head 114 such as, for example, the second valve 304 shown in figure 3. The rotary head drive valve 304 can be one of a plurality of valves in a bank of valves 306 such as, for example, additional valves 308 and 310 shown in figure 3. The additional valves 308 and 310 may control respective aspects of the drilling rig such as, for example, rotational position of the rotary head relative to a further axis on the drilling rig or vertical depth of the auger 104.

In one embodiment, the system controller 302 receives a first signal, via output 224, from the monitoring system 108 indicating that a person has been detected as being at least partially within the defined volume 110. The system controller 302 consequently outputs a signal to an emergency control system 312 for controlling the valve 304 for the hydraulics driving the rotary head 114. The emergency control system 312 operates to prevent the rotary head 114 from at least one of continuing to operate or preventing it from operating. If drilling is in operation at the time the emergency control system 312 receives a signal that there is a person within the predefined volume, the emergency control system 312 actuates the rotary head valve 304 to close immediately, which immediately stops the rotary head 114 from driving the auger 104. Alternatively, or additionally, on the assumption that drilling was yet to commence, an embodiment can be realised in which the emergency control system 312, in response to the signal from the controller 302 indicating that a person is at least partially within the predefined volume 110, prevents the rotary drive hydraulic valve 304 from operating thereby preventing drilling operations from commencing.

In a further embodiment, the system controller 302 uses at least two inputs to determine whether or not to output an emergency stop/inhibit signal to the emergency control system 312. The second input 313 relates to the current speed of the rotary head 114 as determined by a speed measurement system 314. If the system controller 302 determines that the current speed of the rotary head 114 is below a predetermined threshold, even though a person has been detected as being at least partially within the predefined volume 110, then the normal operation of the drilling rig, at that current speed, is not interrupted.

However, if the system controller 302 determines that the current speed of the rotary head 114 meets or exceeds the predetermined threshold, then an emergency stop/inhibit signal is output to the emergency control system 312 to immediately actuate the valve associated with the rotary head 114 to thereby immediately stop the rotary head 114 from rotating or to prevent the rotary head from rotating the auger 104 assuming that rotation had yet to commence.

Additionally, the system controller 302 can issue a signal to generate an audio/visual warning signal via an audio/visual warning generator 316. The system controller 302 can operate the audio/visual warning generator 316 in response to the above determination that a person is at least partially within the predefined volume.

Alternatively, or additionally, the system controller 302 can operate the audio/visual warning generator 316 in response to the monitoring system 108 determining that a person has been detected as being at least partially within a second predefined volume 116. In preferred embodiments, the second predefined volume 116 is larger than the first predefined volume 110. The system controller 302 can be configured to allow the rotary head to continue operating as normal at its present drive setting even though a person has been detected as being at least partially within the second predefined volume 116. Therefore, it can be appreciated that embodiments can be realised in which a warning is issued to such a person who has strayed or is straying too close to the rotary head 114 as a first safety precaution followed by the system controller 302 shutting down, or inhibiting, the drive to the rotary head 114 as a second safety precaution in response to such a person detected as being unacceptably close to the rotary head 114.

Embodiments are provided in which the emergency control system 312 is latched into an emergency stop/inhibit state. Therefore, it will be appreciated that a manual reset 318 is provided to restore the normal operating condition of the drilling rig following an emergency stop/inhibit action. The manual reset 318 is coupled to the emergency control system 312 to reset its latched state. Preferably, resetting the latched state is subject to the system controller 302 indicating that the predefined volume is free from any person. The manual reset is also coupled to the system controller 302 so that normal operation can continue.

Referring to figure 4, there is shown a schematic representation 400 of an embodiment of a light pattern 202 containing reference indicia 402 to 408. In the embodiment illustrated, each reference indicia comprises a plurality of indicium. In preferred embodiments, each indicium corresponds to a light spot of the light pattern 202. For example, the first reference indicia 402 comprises three light spots 402.1, 402.2, 402.3, but some other number of indicia could be used to form the first reference indicia. The reference indicia are arranged in a predetermined configuration. In the embodiment illustrated, the predetermined configuration corresponds to a triangular spatial distribution. Embodiments can be realised in which the reference indicia do not all have the same relative spatial distribution of indicium. The one or more than one of the reference indicia 402 to 408 can, additionally or alternatively, have a predetermined orientation. In the embodiment illustrated, the reference indicia 402 to 408 are oriented upwardly, to the left, downwardly and to the right respectively in a manner similar to arrow heads.

The position of each indicia 402 to 408 is known relative to an origin, 0, via an associated vector. The origin corresponds to the axis 204 of the light pattern 202. It can be appreciated that the first reference indicia 402 has an indicium 402.3 having a position relative to the origin determined by a vector.04. The spatial distribution of the indicia 402.1 to 402.3 constituting a reterence indicia such as indicia 402 is also known via one or more than one vector. In the illustrated embodiment, the spatial distribution of the indicia 402.1 to 402.3 constituting the first reference indicia 402 can be described via a set of vectors. In the illustrated embodiment, the set of vectors describes the relative positions of the centres of the indicia 402.1 to 402.3, that is, via vectors to 1)3 respectively. It will be appreciated that the spatial distribution of the indicia 402.1 to 402.3 will be set using known vectors to achieve a known or real-world coordinates spatial distribution at a known or predetermined real-world reference distance along the axis 204 from the diffractive optical element 208. It will also be appreciated that the spatial distribution of the indicia 402.1 to 402.3 will vary with distance from the diffractive optical element 208 because the light pattern 202 is arranged to be divergent. Furthermore, that spatial variation will be proportional to the distance from the diffractive optical element 208.

Referring to figure 5, there is shown a view 500 of a mathematical basis for depth determination, which can be used by an embodiment of the depth analyser 220. The depth analyser 220 uses the principle of similar triangles to determine the distance of the reference indicia such as, for example, the first reference indicia 402, from the camera 210. The following assumes that the camera axis is in or is parallel to the plane of the page containing figure 5. At the predetermined real-world reference distance, DRRfl, relative to the origin of the diffractive optical element, two of the indicia 402.1 and 402.3 are known to have a separation of D.. Therefore, the separation between the two indicia 402.1 and 402.3, from the perspective of the image plane in the camera 210, will decrease as the light of the light pattern 202 is reflected by an object that is closer to the camera 210 than the predetermined real-world reference distance, L)RWRD, and the separation will increase as the light from the light pattern 202 is reflected by an object that is further away from the camera 210 than the distance DRT.VRD. Therefore, for an apparent separation of indicia 402.1 and 402.3 of (T)+T) ) j) = A RTJRD D can be used the following to determine 1)4 from -1RTfRD -RU) fl (fl sfl \-fl.fl * k"4 RuRfl) -RWRT)' where is the vector of the light spots 502.1 and 502.3, at a distance or vector (1)4 +I)), that corresponds to the vector D-between the light spots 402.1 and 402.3 at a distance or vector of A second embodiment of depth determination that can be undertaken by the depth analyser 220 will be described with reference to figures 6 to 8. Embodiments can use either or both of the depth determination approaches. If both approaches are used, embodiments can be realised that combine the depth determinations via an average such as! for example, a simple mean or a root mean square average.

Referring to figure 6, there is shown a view 600 of the light source 206 and DOE 208, shown as a single entity called a projector 602 hereafter, and the camera 210. It is assumed that a person exists at point A within the first predefined volume 110 surrounding the auger 104 or rotary head 114. Also shown is the optional second predefined volume 116. It can be appreciated that the point A is within a horizontal reference plane, xz plane, containing the camera 210 and projector 602 and is situated at an unknown distance AD from a vertical plane, xy plane, containing the camera 210 and projector 602. It can be appreciated that the point A, the camera 210 and projector 602 define a pair of triangles given by ACD and ABD. The point A is actually, or can be, a normal projection onto the horizontal plane of a reference indicia, or an indicium of such a reference indicia, of the light pattern 202 incident upon the person, which is shown more clearly in figure 7.

Figure 7 is a view 700 of the projection, point A, of a reference indicia or an indicium of such a reference indicia of the light pattern 202 incident upon a person at point A'. The indicium at point A' could, for example, correspond to the third indicium 402.3 of the first reference indicia 402.

In the following, the dimensions, angles, distances, lines, intersections and the like are described with reference to the projections of the corresponding real-world entities in a real-world coordinates system onto the xz plane containing the camera 210 and the projector 602.

Referring to figure 8, there is shown a view 800 of the geometry associated with the second embodiment of depth determination undertaken by the depth analyser 220. The angle BCI between the vertical reference plane 226 containing the projector 602 and camera 210 and the point of intersection I of the central axis 204 of the projector and the central axis 214 of the camera 210 is set at manufacture of the monitoring system 108 to be r /2. Also, the angle BIG, that is, °1YT' is set and known during manufacture of the monitoring system 108.

Therefore, the angle CBI is also known as r / 2-01V7'* The angular position, 0, of a reference indicium, such as, for example, the third indicium 402.3 of the first reference indicia 402 relative to the origin or central 204 axis of the light pattern is known. Therefore, the angle, 0, between the light pattern axis 204 and a line from the origin of the light projector 602, or more particularly the origin of the diffractive optical element, to the indicium, at point A or A', is also known. Therefore, the depth analyser 220, processing data from the camera 210 capturing image data, corresponding to that indicium 402.3, will be able to determine the angle 02 corresponding to the angle ABD/A'BD or ABC/ABC. The equation of the line AB orA'B can be determined, since the gradient is known from 02 and a point on the line is known from the position of the light projector 602, that is, (0,CB). The depth analyser 220 can determine from the image containing the indicium 402.3 the angle 03 between a line from the camera origin to that indicium and the camera axis 214. Therefore, the angle 04 can be determined, which, in tum, leads to an equation for the line AC or A'C being calculated. PointA orA' lies at the point of intersection of the lines AB and AC, orA'B and A'C. That point of intersection can be calculated from the equations of the lines AB and AG or A'B and AG. Once that point of intersection has been calculated, the distance AD or A'D can be calculated by the depth analyser 220. In the case of processing point A' as opposed to its projection, point A, onto the horizontal xz plane, the depth analyser 220 can instead determine the distance from point A' to the vertical plane 226 containing the camera 210 and projector 602. Alternatively, or additionally, once the vector of position A or A' is known, geometry can be used to determine the normal distance from point A or A' to the xy plane 226 since a point on the xy plane 226 and the unit vector defining the orientation of the xy plane 226 are both known.

Referring to figure 9, there is shown a flowchart 900 of the processing undertaken according to an embodiment. At step 902, the light pattern 202 is projected into the predefined volume or the predefined volumes 110/116. Reflected light associated with the light pattern 202 is detected by a sensor of the camera 210 at step 904. The image data detected by the camera sensor is passed to the image processor 216 where it is processed by the person filter/tracker 218 with a view to identifying image data associated with light reflected from a person at step 906. If the person filter 218 identifies light associated with a person from the captured image data, an indication to that effect is output together with image data containing reference indicia associated with light reflected from that person. Step 908 determines whether or not the image data recently processed contains reference indicia associated with a person. If step 908 shows that the image data does not relate to a person, processing resumes at step 904, where the next image captured is processed. However, if step 908 shows that the captured image does contain reference indicia from light reflected from a person, then that image data is processed, at step 910, by the depth analyser 220 to determine the position of the person. The depth analyser 220 can either obtain the image data of interest directly from the person filter 218 or from the original image data subject to the person filter 218 providing a reference to the relevant image data associated with the person. From the depth or position information, the monitoring system controller 222 determines, at step 912, whether or not the person has position data corresponding to a location within the first predefined volume 110. If that determination is positive, the monitoring system controller 222 outputs an indication to that effect to the drilling rig system controller 302 to take a predetermined action, such as, for example, immediately terminating drilling operations or preventing drilling operations from commencing at step 914.

If the determination at step 912 is negative, optionally, the monitoring system controller 222 determines, at step 916, whether or not the position data is within the second predefined volume 116. It the determination at step 916 is negative, processing continues at step 904.

If the determination at step 916 is positive, the monitoring system controller 222 outputs an indication, at step 918, to the rig system controller 302 that a warning should be given via the audio/visual warning system 316. Processing then resumes at step 904 where the next image is processed. Although the embodiment described outputs an audio/visual warning in response to a positive determination at step 916, embodiments are not limited thereto.

Embodiments can be realised in which at least one predetermined action is taken. The predetermined action can comprise the drilling rig system controller 302 slowing the rotary head speed to a predetermined speed such as a nominal rotational speed. This action could be taken in anticipation of the person entering the first, more dangerous, predefined volume so as to effect a more rapid termination of drilling operations.

If the embodiment does not use a second predefined volume, a negative determination at step 912 leads to processing continuing at step 904, where the next captured image is processed.

It will be appreciated that the successful performance of embodiments is predicated upon the interaction between the light projector 602 and the camera 210. If either is obscured then the system cannot operate effectively. Furthermore, if an object obscures the view of the camera 210, the system cannot operate as intended. Suitably, means are provided for detecting whether or not the field of view of the camera 210 is impeded. If the above processing shows an object to be closer than a predetermined threshold distance from the reference plane 226, the operation of the drilling rig is prevented. For example, if the monitoring system 108 detects any object at a distance of 10cm or less or some other relatively proximate distance, then the monitoring system 108 assumes that the field of view of the camera 210 is obscured and instructs the system controller 302 to take at least one predetermined action. Alternatively, or additionally, if the monitoring system 108 is unable to detect any reference indicia, the monitoring system 108 assumes that the field of projection of the projector 602 is obscured and instructs the system controller 302 to take at least one predetermined action. In either case, the at least one predetermined action can be at least one of outputting an alarm containing an indication that the field of projection is obscured, outputting a command to immediately terminate drilling operations and outputting a command to prevent drilling operations from commencing. Alternatively, or additionally, such means can be realised using, for example, a PR motion detection device that uses a combination of IR and microwave technology to detect an obstruction in the field of view.

Referring again to figure 1, embodiments can be shown in which the manual reset 318 is located adjacent to the first monitoring system 108. Preferred embodiments provide a drilling rig comprising a second monitoring system 118 that operates identically to the above described monitoring system 108. The second monitoring system 118 is arranged to that at least one of the fields of projection and the fields of view of the projectors and cameras of the first 108 and second 118 monitoring systems are complementary. In one embodiment, the complementary nature is such that blinds spots are at least minimised and preferably eliminated.

Although embodiments have been described within the context of monitoring systems for drilling rigs, embodiments are not limited thereto. Embodiments can be provided in which the monitoring systems for detecting the presence of a person within one or more than one predefined volume are applied in other contexts such as, for example, on other vehicles.

The vehicles could be motor vehicles such as cars, lorries, movable plant equipment such as, for example, diggers, trucks, cranes and the like, or plant equipment, in addition to or other than drilling rigs, that have moving pads, especially such plant equipment that have moving pads that are potentially dangerous or fatal to people or that are movable as a whole in a manner that could be dangerous or fatal to people. The monitoring system can be especially useful when reversing such vehicles, particularly if they have blind spots. As described above, detecting the presence of a person within such a predefined volume relative to the vehicle would effect a predetermined action such as, for example, at least one of terminating a selective current operation of the vehicle, preventing an intended operation from occurring or outputting an alarm to a driver, operator or the detected person taken jointly and severally in any and all combinations. The current or intended operation could be a reversing manoeuvre, a turn, especially a turn in a direction that is opposite to the driving position of the vehicle, eg a left turn of a right-hand drive vehicle or visa versa, or an unloading or lifting operation.

It will be appreciated from the above that the monitoring systems act as effective electronic guard systems that can potentially save lives or otherwise improve the safety of people near such vehicles or plant.

It will be appreciated that embodiments of the present invention can be realised in the form of hardware, software or a combination of hardware and software. Any such software may be stored in the form of volatile or non-volatile storage such as, for example, a storage device like a ROM, whether erasable or rewritable or not, or in the form of memory such as, for example, RAM, memory chips, device or integrated circuits or machine readable storage such as, for example, DVD, memory stick or solid state medium. It will be appreciated that the storage devices and storage media are embodiments of non-transitory machine-readable storage that are suitable for storing a program or programs comprising instructions that, when executed, implement embodiments described and claimed herein. Accordingly, embodiments provide machine executable code for implementing a system, device or method as described herein or as claimed herein and machine readable storage storing such a program. Still further, such programs may be conveyed electronically via any medium such as a communication signal carried over a wired or wireless connection and embodiments suitably encompass the same.

Claims

CLAIMS1. A drilling rig comprising a carrier or drill string for carrying a drill having a drilling axis; the rig comprising a monitor for detecting the presence of a person at least partially within a first predefined volume relative to the drilling axis, the monitor being responsive to detecting a person within the first predefined volume to influence operation of a drive control system for actuating the drill.
2. A rig as claimed in claim 1, wherein the monitor, responsive to detecting a person within the first predefined volume, is operable to prevent the drive control system from operating/starting.
3. A rig as claimed in any preceding claim, wherein the monitor, responsive to detecting a person within the first predefined volume, is operable to stop the drive control system from actuating the drill.
4. A rig as claimed in any preceding claim, wherein the monitor, responsive to detecting a person within a second predefined volume, is operable to output a signal to produce at least one of an audible and visual warning indicating that a person has been detected at least partially within the second predefined volume, wherein the second predefined volume is different to the first predefined volume.
5. A rig as claimed in claim 4, in which the first predefined volume is a subset or subspace of the second predefined volume.
6. A rig as claimed in any of claims 4 to 5, wherein the monitor, responsive to detecting a person within the second predefined volume, is operable to take a predetermined action such as at least one of instructing the drive control system to slow the rotary head to a predetermined speed or to stop the drive control system from actuating the drill.
7. A rig as claimed in any preceding claim, in which the monitor comprises a first projector arranged to illuminate, within a respective field of illumination, the first predefined volume with a first light pattern of a given wavelength; the first light pattern comprising respective reference indicia.
8. A rig as claimed in claim 7, in which the monitor comprises at least a first camera having a respective field of view arranged to overlap with the field of illumination of the first projector within the first predefined volume.
9. A rig as claimed in claim 8, comprising a filter adapted to process light associated with the light pattern to identify light associated with a person within the predefined volume.
10. A rig as claimed in claim 9, comprising an image processor arranged to identify at least an indicium of the indicia from light associated with the person and to determine a distance relative to a reference plane containing the first camera and the first projector.
11. A rig as claimed in claim 10, in which the monitor determines from the determined distance whether or not the person is at least partially within the first predefined volume.
12. A monitor for detecting the presence of a person at least partially within a first predefined volume relative to a drilling axis of a drill of a drilling rig, the monitor being responsive to detecting a person within the first predefined volume to influence operation of a drive control system for actuating the drill.
13. A monitor as claimed in claim 12, wherein the monitor, responsive to detecting a person within the first predefined volume, is operable to prevent the drive control system from operating/starting.
14. A monitor as claimed in any of claims 12 to 13, wherein the monitor, responsive to detecting a person within the first predefined volume, is operable to stop the drive control system from actuating the drill.
15. A monitor as claimed in any of claims 12 to 14, wherein the monitor, responsive to detecting a person within a second predefined volume, is operable to output a signal to produce at least one of an audible and visual warning indicating that a person has been detected at least partially within the second predefined volume, wherein the second predefined volume is different to the first predefined volume.
16. A monitor as claimed in claim 15, in which the first predefined volume is a subset or subspace of the second predefined volume.
17. A monitor as claimed in any of claims 12 to 16, wherein the monitor, responsive to detecting a person within the second predefined volume, is operable to take a predetermined action such as at least one of instructing the drive control system to slow the rotary head to a predetermined speed or stop the drive control system from actuating the drill.
18. A monitor as claimed in any of claims 12 to 17, in which the monitor comprises a first projector arranged to illuminate, within a respective field of illumination, the first predefined volume with a first light pattern of a given wavelength; the first light pattern comprising respective reference indicia.
19. A monitor as claimed in claim 18, in which the monitor comprises at least a first camera having a respective field of view arranged to overlap with the field of illumination of the first projector within the first predefined volume.
20. A monitor as claimed in claim 19, comprising a filter adapted to process light associated with the light pattern to identify light associated with a person within the predetermined volume.
21. A monitor as claimed in claim 20, comprising an image processor arranged to identify at least an indicium of the indicia from light associated with the person and to determine a distance relative to a reference plane containing the first camera and the first projector.
22. A monitor as claimed in claim 21, in which the monitor determines from the determined distance whether or not the person is at least partially within the first predefined volume.
23. A monitor for detecting the presence of a person at least partially within a first predefined volume relative to a vehicle, the monitor being responsive to detecting a person within the first predefined volume to influence an operation of the vehicle.
24. A monitor as claimed in claim 23, wherein the monitor, responsive to detecting a person within the first predefined volume, is operable to prevent the operation of the vehicle from starting.
25. A monitor as claimed in any of claims 23 to 24, wherein the monitor, responsive to detecting a person within the first predefined volume, is operable to stop the operation of the vehicle.
26. A monitor as claimed in any of claims 23 to 25, wherein the monitor, responsive to detecting a person within a second predefined volume, is operable to output a signal to produce at least one of an audible and visual warning indicating that a person has been detected at least partially within the second predefined volume, wherein the second predefined volume is different to the first predefined volume.
27. A monitor as claimed in claim 26, in which the first predefined volume is a subset or subspace of the second predefined volume.
28. A monitor as claimed in any of claims 23 to 27, wherein the monitor, responsive to detecting a person within the second predefined volume, is operable to take a predetermined action.
29. A monitor as claimed in any of claims 23 to 28, in which the monitor comprises a first projector arranged to illuminate, within a respective field of illumination, the first predefined volume with a first light pattern of a given wavelength; the first light pattern comprising respective reference indicia.
30. A monitor as claimed in claim 29, in which the monitor comprises at least a first camera having a respective field of view arranged to overlap with the field of illumination of the first projector within the first predefined volume.
31. A monitor as claimed in claim 30, comprising a filter adapted to process light associated with the light pattern to identify light associated with a person within the predetermined volume.
32. A monitor as claimed in claim 31, comprising an image processor arranged to identify at least an indicium of the indicia from light associated with the person and to determine a distance relative to a reference plane containing the first camera and the first projector.
33. A monitor as claimed in claim 32, in which the monitor determines from the determined distance whether or not the person is at least partially within the first predefined volume.
34. A computer program comprising instructions arranged, when executed, to realise a monitor or drilling rig as claimed in any preceding claim.
35. Computer readable storage storing a computer program as claimed in claim 34.
36. A rig or vehicle substantially as described herein with reference to and/or as illustrated in one or more than one of the accompanying drawings.
37. A monitoring system substantially as described herein with reference to and/or as illustrated in one or more of the accompanying drawings.
38. A control system for a vehicle, plant equipment or drilling rig substantially as described herein with reference to and/or as illustrated in one or more of the accompanying drawings.