GB2277069A - Track mounted camera system - Google Patents

Abstract

A camera (64) is carried by a vehicle (1) along an extruded track (3) driven through a rack and pinion drive by a motor (5) onboard the vehicle (1). Power is delivered to the motor (5) via a power bus (20) and pick-up (21) from a servo amplifier (19) under the control of a processor (13). An operator inputs a demand signal (15) which is processed by the processor (13) to generate a control signal (18) which is proportional to motor speed and feedback as to the position of the vehicle (1) is derived via a telemetry link (10, 11) which transmits displacement information from the vehicle (1). The apparatus can be used for remote inspection or surveillance, or for cinematographical filming. <IMAGE>

Description

"APPARATUS FOR REMOTELY DEPLOYING A CAMERA" This invention relates to apparatus for remotely deploying a camera and in particular but not exclusively to apparatus in which a camera is mounted on a vehicle deployed on an overhead track and driven along the track under remote control.

It is known to provide remote camera deployment using a vehicle which is moved along a track by means of an endless belt conveyor driven by a motor mounted at a fixed control station. Such systems have their limitations particularly in the length of track over which such a system can satisfactorily be operated.

It is also difficult for such systems to accommodate curves in the track.

According to the present invention there is disclosed apparatus for use in remotely deploying a camera comprising a vehicle supporting a camera mount, the vehicle being movable relative to a control station along a path defined by a track, drive means operable to drive the vehicle relative to the track and control means operable at the control station to control the drive means wherein the drive means comprises a motor mounted on the vehicle.

An advantage of such an arrangement is that the track can conveniently be extended to any length and may include curved portions without the inherent disadvantages of the belt drive mechanism.

The control means may comprise a digital electronic motion control processor operable to output a power control signal to a power regulator supplying power to the motor.

Such a processor may be programmed to regulate the motor power in such a way as to effect smooth acceleration and deceleration when deploying the vehicle to a required position along the track.

Preferably the motion control processor is connected to an operator input device operable to input command signals representative of required values of displacement and/or velocity of the vehicle relative to the track.

The motion control processor may be connected to a progammable input device operable to provide command signals of required vehicle displacement and/or velocity to effect vehicle motion in a predetermined cycle.

Conveniently the apparatus further comprises a displacement sensor mounted on the vehicle and communicating means operable to transmit a displacement signal therefrom to the control means.

The displacement and velocity of the vehicle relative to the control station may thereby be determined automatically and remotely and may be continuously utilised to provide a feedback signal to control the operation of the drive means.

Conveniently the communication means comprises a telemetric link.

The use of a telemetric link avoids the need for any umbilical cabling between the vehicle and the control station.

Advantageously the telemetric link may comprise a leaky coaxial waveguide extending along the track.

The telemetric transmisiion may thereby be localised to the vicinity of the track to minimise interference effects.

Alternatively the communciation means may comprise a displacement signal bus extending along the track and co-operable with a co-operating pick-up mounted on the vehicle.

Preferably the sensor comprises an incremental encoder which may be responsive to rotational movement of the drive means.

Such encoders have the advantage of providing high definition displacement information and enable the motor speed to be accurately monitored. The control means may then be operable to determine the displacement of the vehicle relative to the control station by counting encoder output signals representative of increments of displacement.

Alternatively the motion control processor may be operable to generate an estimated value of displacement of the vehicle from an initial position by performing an integration with respect to time of the power control signal.

This is made possible by the use of a motor having a speed which is directly proportional to voltage so that by appropriate calibration the power control signal can be taken as being directly proportional to vehicle velocity.

Conveniently the apparatus may further comprise position sensors at spaced locations along the track operable to input signals to the motion control processor representative of measured values of displacement of the vehicle whereby the processor may be operable to update the estimated value of displacement with a measured value of displacement on receipt of such a signal.

In effect this allows the motion of the vehicle to be modelled within the processor and for the measured values to be used periodically to correct any errors in the estimated values.

Conveniently a power bus extends along the track and the drive means may be supplied with power by means of a power pick-up co-operable with the power bus.

Conveniently the drive means comprises a toothed rack extending along the track and the motor is operatively connected to a pinion engageable with the rack to effect longitudinal displacement along the track.

Advantageously a spring means is operable to bias the pinion into operative engagement with the rack.

The pinion may be mounted directly on a driven shaft of the drive means and the drive means may be mounted on a mounting which is transversely movable relative to the vehicle so as to maintain the pinion in engagement with the rack.

A spring means may be operable between the pinion and a roller disposed such that the rack is gripped between the pinion and the roller.

By this arrangement the pinion may be biassed into positive contact with the rack without exerting any reactive spring bias against the vehicle.

Conveniently the drive means may comprise a gear box connected to the motor and having an output shaft constituting the driven shaft upon which the pinion is directly mounted.

Preferably the track comprises a plurality of extruded sections of generally inverted U-shaped profile adapted to provide the track in an overhead configuration in which the camera mount is supported beneath the vehicle.

The extruded sections may comprise both linear and curved sections of track.

The track may alternatively comprise a pair of tubular members extending in uniformly spaced relationship.

Conveniently the vehicle comprises a first portion within which the drive means is located, a second portion supporting the camera mount and an articulatable linkage connecting the second portion to the first portion.

The first and second portions may thereby be articulated to accommodate relatively tight curves in the track.

Advantageously the linkage may comprise a link having first and second ends pivotally connected to respective first and second portions of the vehicle and whereby a load is connected to and supported by the link.

Such a load may conveniently comprise a processor housing containing operating circuits for the camera.

Conveniently the track comprises a generally tubular enclosure within which the vehicle is longitudinally movable and wherein the enclosure comprises a longitudinally extending window.

Preferably the window provides substantially one way transmission of light in a direction allowing light to enter the enclosure.

Preferably a camera is mounted on the camera mount and the camera mount is operable to orient the camera relative to the vehicle in response to camera control signals conducted from the control station by means of a camera control signal bus extending along the track.

Conveniently the camera may be a video camera linked to a receiver by a further telemetry link.

According to a further aspect of the present invention there is disclosed a method of deploying a camera mounted on a vehicle which is movable along a track relative to a control station, comprising the steps of inputting to a motion control processor at the control station signals representative of a desired position and/or velocity of the vehicle, delivering to a drive means of the vehicel a d.c.

voltage via a power bus from a power regulator drive by the motion control processor, determining a parameter representative of the displacement of the vehicle from an initial position and using the parameter in a feedback loop to control a power control signal generated by the motion control processor to drive the power regulator such that the vehicle travels in the desired manner.

The parameter may be a measured value of displacement derived from operation of a displacement sensor.

Alternatively the parameter may be an estimated value of displacement derived from an integration over time of the power control signal.

A preferred embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings of which: Figure 1 is a schematic diagram of apparatus having a displacement sensor with a telemetry link transmitting displacement information to a control station; Figure 2 is a sectioned plan view illustrating a vehicle having a drive means coupled to a track; Figure 3 is a sectioned elevation of the vehicle and track of Figure 2; Figure 4 is a sectioned elevation of part of the vehicle and track of the apparatus of Figures 2 and 3 illustrating the pick-up of power and signals from the track; Figure 5 is a transverse sectioned elevation of the lower part of the track of Figures 2, 3 and 4 showing a window; Figure 6 is a schematic diagram of the circuitry handling the encoder output;; Figure 7 is a side elevation of the vehicle and track showing a mounted camera; and Figure 8 is a perspective view of the extrusion forming the track; Figure 9 is a schematic view of an alternative apparatus; Figure 10 is a schematic view of one portion of the vehicle shown in Figure 9 illustrating the mechanism by which the pinion is biassed against the track; Figure 11 is a transversely section elevation of the vehicle portion shown in Figure 10; Figure 12 is a plan view showing a motor mounting of the vehicle portion shown in Figure 11; and Figure 13 is a schematic diagram illustrating a further alternative apparatus.

In Figure 1 a vehicle 1 is movable relative to a control station 2 along a track 3 by action of a vehicle mounted drive means 4 driven by a motor 5.

Details of the drive means 4 and track 3 will be described below with reference to later Figures.

The motor 5 is provided with an optical incremental encoder 6 which is mounted on a driven shaft 7 of the motor. In response to rotation of the shaft 7, the encoder 6 produces output signals A and B in the form of square wave pulses at a frequency proportional to the speed of rotation and such that each pulse of signals A and B constitutes an incremental displacement signal representing movement of the vehicle relative to the track by a known incremental displacement. Signals A and B are 0 generated so as to be 90 out of phase in a sense which identifies the direction of rotation and hence the direction of vehicle displacement. A third output of the encoder is provided as a reference signal 8 giving one square pulse per completed revolution of the shaft 7.

Signals A, B and the reference signal 8 are input to a telemetry input circuit 9 which encodes the signals using a frequency division multiplexing technique described below with reference to Figure 6 and generates a frequency modulated radio signal transmitted by a transmitter 10. The radio signal is conducted by a leaky coaxial waveguide (not shown) extending along the track in proximity with the transmitter. The waveguide may for example comprise a co-axial cable having an incomplete external earth screen provided by a coarse metal mesh. A receiver 11 at the control station receives the frequency modulated radio signal and re-constitutes the encoder output signals by means of a telemetry output circuit 12.

A motion control processor 13 receives these re-constituted signals and computes the displacement of the vehicle 1 relative to the control station 2 by summation of the incremental displacements taking account of the direction of travel indicated by the relative phase of A and B.

The motion control processor 13 receives command signals 14 and 15 from input devices 16 and 17 respectively, the command signals identifying the position to which the vehicle 1 is required to be located, and the motion control processor effects motion of the vehicle accordingly by outputting a power control signal 18 as a d.c. voltage in the range -10 to +10 volts which controls the operation of a motor power regulator 19.

Power from a power supply 69 is conducted via the power regulator 19 into a power bus 20 extending along the track 3, the vehicle 1 being provided with a power pick-up 21 making sliding contact with the power bus 20 as described below with reference to Figure 4.

The motion control processor 13 is programmed with a suitable motion algorithm so as to smoothly regulate the motor speed in a manner which achieves smooth acceleration and deceleration of the vehicle in travelling to the desired position.

Input device 16 is a programmable input device generating commands defining a predetermined cycle of operation in which the vehicle 1 is to perform a required cycle of movement. Input device 17 is an operator controlled input device allowing the vehicle 1 to be controlled directly by the operator in response to the observed position and speed of the vehicle.

The track 3 is indicated in this example as being a linear track of finite length and is provided with limit switches 22 and 23 at the respective end limits of vehicle travel. The limit switches 22 and 23 provide inputs to the motion control processor 13 indicating that the limits of travel have been reached by the vehicle 1, the motion control processor being programmed to shut-off power to the motor 5 accordingly.

In Figure 2 a first portion 24 of vehicle 1 is shown to have four running wheels 25 arranged to run along parallel tracks 26 and 27. The wheels 25 are bevelled at a suitable angle to avoid hunting as the vehicle 1 runs along the rails 26 and 27.

The motor 5 is mounted such that driven shaft 7 extends vertically upwardly of the motor, the motor being a d.c. motor of a type referred to as a "pancake motor" having an armature printed on to a rotating disc structure mounted on the driven shaft.

As seen in the corresponding elevation view of Figure 3, the shaft encoder 6 is mounted beneath the motor 5 on a downwardly projecting portion of the shaft 7.

The driven shaft 7 carries a first geared pulley 28 which is coupled to a second geared pulley 29 by a toothed belt 30 so as to drive a second shaft 31 in unison with the driven shaft 7. A pinion 32 is mounted on the second shaft 31 and is held in meshed engagement with a linear toothed rack 33 which extends along the track. The rack 33 is formed of a hard plastics material bonded to a vertical plate 34 formed integrally with the track 3. Rotation of the motor 5 thereby drives the pinion 32 and results in the vehicle 1 being driven longitudinally relative to the track 3.

The second shaft 31 is journalled in the free end portion 35 of a first swing arm 36 which is pivotally mounted about a pivot 37 and spring biassed by action of a spring 38 in a direction which urges the pinion 32 into engagement with the rack 33. A second swing arm 39 is similarly pivotally mounted about a pivot 40 and has a free end portion 41 carrying a roller 42 which makes rolling contact with the plate 34. The spring 38 biases together the swing arms 36 and 39 such that equal and opposite transverse forces are exerted on the rack 33 and plate 34 by the pinion 32 and roller 42 respectively.

The track 3 is comprised of an aluminium extrusion of generally inverted U-shape so as to comprise a horizontal upper plate 43 and left and right-hand depending side plates 44 and 45 respectively. A suspension bracket 46 projects upwardly from the upper plate 43 thereby providing means for attaching the track to an overhead support.

The plate 34 projects downwardly from the upper plate 43. The extrusion forming the track 3 is shown in perspective view in Figure 8.

Inwardly facing projections 47 and 48 are formed integrally with the extruded track 3 to receive the linear tracks 26 and 27 which are formed of hard plastics material.

As shown in Figure 3, the upper plate 43 is keyed to receive left and right-hand inserts 49 and 50 respectively formed of a hard plastics material and defining parallel longitudinally extending slots 51 to 54. As shown in Figure 4, the slots 51 to 54 are engageable by pick-up shoes 55 to 58 respectively, the slots and shoes being provided with respective electrical contact surfaces such that each slot defines three contact surfaces making electrical connection with three corresponding contact surfaces of a respective shoe.

The slots 51 to 54 and shoes 55 to 58 together allow signals and power to be communicated between the track and the vehicle 1. The track may thereby incorporate a power bus together with signal buses which may for example include a camera signal bus giving control signals to an active camera mount.

Other signals may similarly be conducted using this pick-up arrangement depending on the type of communication system adopted between the vehicle and the control station. The method of pick-up is an alternative to the use of telemetry links in so far as the communication of signals between vehicle and control station is concerned.

Figure 5 shows the addition of a perspex window 59 depending from the left and right side plates 44 and 45 such that the track 3 and window 51 together comprise a tubular enclosure through which the vehicle can run.

The track is formed on sections of equal length which are coupled together to form any desired length of track which may if required be a continuous loop.

The window 51 is similarly formed in sections assembled with the track sections. The window 59 incorporates an internal reflective layer which allows sufficient light to enter the enclosure for a camera mounted on the vehicle 1 to make observations of the surroundings whilst substantially preventing an outside observer from viewing the interior of the enclosure. In this way the position of the vehicle along the track cannot readily be discerned by an outside observer.

Figure 6 illustrates schematically the way in which encoder outputs A, B and reference signal 8 are multiplexed. Signals A and B are input to respective frequency modulators 60 and 61 at distinct modulation frequencies in the audio bandwidth and the reference signal 8 is converted to an audio pulse by a tone burst generator 62. Outputs from the modulators 60, 61 and the generator 62 are mixed in a mixer 70 and the mixed audio output in the range 1 to 2 kilohertz is then input to a frequency modulation circuit 63 prior to transmission by FM transmitter 10.

The telemetry output circuit 12 contains respective band-pass filters corresponding to the characteristic frequencies of the modulators 60, 61 and generator 62 enabling the encoder signals to be recovered and interpreted by the motion control processor 13.

In Figure 7 the mounting of a camera 64 on a camera mount 65 is illustrated. The camera mount 65 is mounted on a second portion 66 of the vehicle 1 which has its own wheeled chassis 67 and is towed or pushed by the first portion 21 of the vehicle by means of a linkage 68.

The linkage 68 is arranged to allow articulation between the first and second portions 24 and 66 so that the vehicle 1 can more readily negotiate bends in the track 3. In this way bends having a radius of 0.75 metres may be accommodated with each of the first and second portions having a wheel base of 134 millimetres and an axle length of 142 millimetres. It is envisaged that several kilometres of track could be utilised in such apparatus and over such extended distances that the motion controlled processor would be programmed to automatically compensate for the expected power losses as a function of vehicle distance with an appropriate adjustment to the power control signal 18.

In the above example a power output having a maximum of 80 volts, 10 amps during normal running conditions could be used to power a motor having a maximum speed of 6,000 rpm. Position resolution to 0.5 metres is readily achievable in such apparatus and will suffice for most applications.

The programmable input device 16 may be a computer allowing programming to be carried out in a high level language and can be also used for programming the motion control processor 13 with the motion control algorithm during an initialisation process in which the compiled programme is down loaded for subsequent execution.

An alternative apparatus 100 will now be described with reference to Figures 9, 10, 11 and 12 using corresponding references to those of previous Figures where appropriate for corresponding elements.

As shown schematically in Figure 9 the apparatus 100 comprises a vehicle 1 having a first portion 101 carrying a camera 64 and a microphone 102 with a second portion 66 of the vehicle carrying a motor 5 which is responsible for driving the vehicle longitudinally relative to a track 3.

The first and second portions 101,66 are connected by a linkage 68 allowing articulation and comprising a link plate 103 having first and second end portions 104,105 which are respectively pivotally connected to the first and second portions of the vehicle. By this arrangement the vehicle is capable of negotiating tight bends in the track 3.

The link plate 103 also serves as a support for a processor housing 106 which contains digital electronic processing circuits for encoding and transmitting the outputs of the camera and microphone and for processing instructions for the control of the camera and microphone in order to provide actuating signals driving transducers which control their respective positions and functions.

The track 3 is provided in this embodiment by a pair of aluminium tubes which extend in uniformly spaced apart relationship and which for most applications will be positioned in the same horizontal plane. The tubes are connected at intervals along the track by bracing members (not shown) and are supported by suspension brackets.

The track 3 is engaged by running wheels 25, each of the first and second portions 66,105 being provided with eight running wheels arranged in pairs as illustrated in Figure 11 so as to prevent transverse movement of the vehicle relative to the track in both horizontal and vertical directions.

The schematic drawing of Figure 9 omits for clarity detail of a rack 33 of the type shown in Figure 2 which extends in a vertical plane and is engaged by a pinion 107 as shown in Figure 12. Figure 9 also omits detail of a power bus and power pick-up arrangement which may be generally equivalent to that described with reference to Figure 3 above.

As shown schematically in Figure 10, the motor 5 together with its associated gear box 108 is rigidly connected to a mounting 109 in the form of a horizontal rectangular metal plate through which the gear box projects upwardly. A drive shaft 110 delivers the output of the gear box and pinion 107 is directly mounted on the drive shaft so as to directly engage the rack 33 which is in the form of a toothed belt supported vertically and extending along the length of the track 3.

A roller 42 engages the opposite side of the rack 33 to that side of the rack which is engaged by the pinion 32 and the roller 42 is freely rotatable on a vertical shaft 111. A spring 112 is arranged to bias together the shaft 111 and the mounting 109 such that the rack 33 is positively gripped between the roller 42 and the pinion 107.

The mounting 109 is freely movable in a horizontal transverse direction relative to the track 3 and for this purpose is supported on guide rods 113,114 which extend horizontally and transversely in parallel spaced relationship and which are fixed to the structure of the second portion 66 of the vehicle 1.

Bearing blocks 115 project downwardly from each of the four corners of the mounting 109 and are journalled to receive the guide rods 113,114 in axially slidable relationship.

The position of the pinion together with the motor 5 will therefore tend to move laterally as the vehicle 1 moves along the track 3 to allow compensation for misalignment of the rack 33, this being particularly important when negotiating bends in the track. The above described arrangement has been found to avoid jamming associated with yaw in the vehicle induced by torque applied by the motor, the pinion and motor being essentially freely floating in the transverse direction relative to the vehicle.

Flexible conductor leads (not shown) are required between the motor and the vehicle 1 for the transmission of power.

The relationship between the motor 5, mounting 109 and the guide rods 113,114 is shown in transverse section in Figure 11 which also illustrates the relative position of the running wheels 25 to the track 3. The running wheels 25 are mounted on longitudianlly extending struts 116, the wheels being arranged in pairs which when viewed longitudinally with respect to the track engage the track at angles of 600 above and below the horizontal respectively.

Both transverse and vertical movement of the vehicle relative to the track 3 is thereby constrained.

Figure 11 also illustrates generally a power and signal bus 117 which extends longitudinally of the track and which is engaged by pick-up shoes (not shown) carried by the vehicle 1.

The second portion 66 as shown in Figure 11 is constructed to include upwardly extending cheek plates 118 arranged in transversely opposite pairs both fore and aft of the motor, the cheek plates being interconnected by the horizontally extending struts 116 such that the overall structure resembles a cage.

This construction is inherently rigid and allows the wheels 25 to be covered by the cheek plates 118.

The configuration of the rack 33 relative to the pinion is illustrated in plan view in Figure 12.

Alternative arrangements based on any of the above described embodiments are envisaged in which the displacement sensor could utilise an absolute position encoding technique such as a binary code placed on the track and read by a suitable reader carried on the vehicle. The coding may be any suitable code such as a Gray code.

The camera mount may if required incorporate a gyroscopic stabilising platform or an air bearing suspension.

The camera may alternatively be a conventional cine film camera, stills camera or a combination of camera types.

The vehicle is capable in the above examples of travelling at a speed in excees of 12 metres per second.

Apparatus in accordance with the present invention may be utilised for the remote inspection of otherwise inaccessible areas or for routine surveillance. The apparatus also has application for filming outdoor events and cinematographical filming.

The apparatus described above with reference to the above Figures may be modified to include an alternative arrangement for determining and controlling the displacement and speed of the vehicle relative to the track as illustrated schematically in Figure 13. A further alternative apparatus 120 will therefore be described using corresponding references to those of previous Figures where appropriate for corresponding elements.

As with previous apparatus, a vehicle 1 is movable along a track 3 relative to a control station 2 and is driven by a motor 5 powered by a motor power regulator 19 at the control station, power being conducted along a power bus 20 extending along the track and conducted to the motor via a power pick-up 21 carried by the vehicle.

Limit switches 22 and 23 are provided on the track to indicate to the control station 2 when the vehicle 1 has reached its allowed limits of longitudinal travel.

The motion control of the vehicle 1 is governed by a motion control processor 13 within the control station 2 which receives input demands either from a programmable input device 16 or from an operator controlled input device 17 which generate respective command signales 14 and 15.

The motion control processor 13 provides a power control signal 18 which is input to the motor power regulator 19, the motor power regulator 19 being a servo amplifier selected for its extremely linear properties of controlling motor speed in a linear relationship to the power control signal 18. The power control -signal 18 is a d.c. voltage in the range -10 to +10 volts. The motor 5 is selected to be a d.c. servo motor providing a high degree of linearity between speed and voltage delivered via the bus 20.

The servo amplifier or motor power regulator 19 is of a type which employs known IR compensation technique in order to ensure that the motor speed corresponds virtually exactly in proportion to the control signal 18.

In this arrangement the motor control processor 13 is arranged to estimate the position of the vehicle relative to the control station relative to an initialising calibration position which may be sensed used one of the limit switches 22,23, the estimated value of displacement from the initial position being calculated by integrating the power control signal 18 with respect to elapsed time. It is found in practice that reasonably accurate estimates of displacement for most purposes can be developed in this manner.

Optionally, in order to improve accuracy of the estimated displacement position over extended operating times, position sensors 119 are placed at intervals along the track 3 and arranged to provide input signals to the motion control processor 13 whenever the vehicle 1 moves into registration with one of the sensors. The position sensors 119 may conveniently be proximity sensors such as capacitive or ultrasonic sensors or may be optical sensors.

The position of the vehicle 1 may thereby be controlled by inputting a command signal 14 or 15 representative of a desired displacement, the motion control processor 13 then comparing the estimated value of displacement with the desired displacement and generating a suitable power control signal 18 required to move the vehicle so as to null the difference.

Claims (35)

CLAIMS:

1. Apparatus for use in remotely deploying a camera comprising a vehicle supporting a camera mount, the vehicle being movable relative to a control station along a path defined by a track, drive means operable to drive the vehicle relative to the track and control means operable at the control station to control the drive means wherein the drive means comprises a motor mounted on the vehicle.

2. Apparatus as claimed in claim 1 wherein the control means comprises a digital electronic motion control processor operable to output a power control signal to a power regulator supplying power to the motor.

3. Apparatus as claimed in claim 2 wherein the motion control processor is connected to an operator input device operable to input command signals representative of required values of displacement and/or velocity of the vehicle relative to the track.

4. Apparatus as claimed in any preceding claim wherein the motion control processor is connected to a progammable input device operable to provide command signals of required vehicle displacement and/or velocity to effect vehicle motion in a predetermined cycle.

5. Apparatus as claimed in any preceding claim further comprising a displacement sensor mounted on the vehicle and communicating means operable to transmit a displacement signal therefrom to the control means.

6. Apparatus as claimed in claim 5 wherein the communication means comprises a telemetric link.

7. Apparatus as claimed in claim 6 wherein the telemetric link comprises a leaky coaxial waveguide extending along the track.

8. Apparatus as claimed in claim 5 wherein the communciating means comprises a displacement signal bus extending along the track and co-operable with a co-operating pick-up mounted on the vehicle.

9. Apparatus as claimed in any of claims 5 to 8 wherein the sensor comprises an incremental encoder.

10. Apparatus as claimed in claim 9 wherein the encoder is responsive to rotational movement of the drive means.

11. Apparatus as claimed in any of claims 9 and 10 wherein the control means is operable to determine the displacement of the vehicle relative to the control station by counting signals representative of increments of displacement from the encoder.

12. Apparatus as claimed in any of claims 2 to 4 wherein motion control processor is operable to generate an estimated value of displacement of the vehicle from an initial position by performing an integration with respect to time of the power control signal.

13. Apparatus as claimed in claim 2 comprising position sensors at spaced locations along the track operable to input signals to the motion control processor representative of measured values of displacement of the vehicle and wherein the processor is operable to update the estimated value of displacement with a measured value of displacement on receipt of such a signal.

14. Apparatus as claimed in any preceding claim wherein a power bus extends along the track and the drive means is supplied with power by means of a power pick-up co-operable with the power bus.

15. Apparatus as claimed in any preceding claim wherein the drive means comprises a toothed rack extending along the track and the motor is operatively connected to a pinion engageable with the rack to effect longitudinal displacement along the track.

16. Apparatus as claimed in claim 15 comprising spring means operable to bias the pinion into operative engagement with the rack.

17. Apparatus as claimed in claim 16 wherein the pinion is mounted directly on a driven shaft of the drive means and wherein the drive means is mounted on a mounting which is transversely movable relative to the vehicle so as to maintain the pinion in engagement with the rack.

18. Apparatus as claimed in claim 17 wherein the spring means is operable between the pinion and a roller disposed such that the rack is gripped between the pinion and the roller.

19. Apparatus as claimed in any of claims 17 and 18 wherein the drive means comprises a gear box connected to the motor and having an output shaft constituting the driven shaft upon which the pinion is directly mounted.

20. Apparatus as claimed in any preceding claim wherein the track comprises a plurality of extruded sections of generally inverted U-shaped profile adapted to provide the track in an overhead configuration in which the camera mount is supported beneath the vehicle.

21. Apparatus as claimed in any of claims 1 to 19 wherein the track comprises a pair of tubular members extending in uniformly spaced relationship.

22. Apparatus as claimed in any of claims 20 and 21 wherein the extruded sections comprise both linear and curved sections of track.

23. Apparatus as claimed in any preceding claim wherein the vehicle comprises a first portion within which the drive means is located, a second portion supporting the camera mount and an articulatable linkage connecting the second portion to the first portion.

24. Apparatus as claimed in claim 23 wherein the linkage comprises a link having first and second ends pivotally connected to the respective first and second portions of the vehicle and wherein a load is connected to and supported by the link.

25. Apparatus as claimed in claim 24 wherein the load comprises a processor housing containing operating circuits for the camera.

26. Apparatus as claimed in any preceding claim wherein the track comprises a generally tubular enclosure within which the vehicle is longitudinally movable and wherein the enclosure comprises a longitudinally extending window.

27. Apparatus as claimed in claim 26 wherein the window provides substantially one way transmission of light in a direction allowing light to enter the enclosure.

28. Apparatus as claimed in claimed in any preceding claim further comprising a camera mounted on the camera mount and wherein the camera mount is operable to orient the camera relative to the vehicle in response to camera control signals conducted from the control station by means of a camera control signal bus extending along the track.

29. Apparatus as claimed in any preceding claim comprising a microphone carried by the vehicle.

30. Apparatus as claimed in claim 20 wherein the camera is a video camera and further comprising a further telemetry link operable to transmit camera and or microphone output signals to a co-operating receiver.

31. A method of deploying a camera mounted on a vehicle which is movable along a track relative to a control station, comprising the steps of inputting to a motion control processor at the control station signals representative of a desired position and or velocity of the vehicle, delivering to a drive means of the vehicle a d.c. voltage via a power bus from a power regulator driven by the motion control processor, determining a parameter representative of the displacement of the vehicle from an initial position and using the parameter in a feedback loop to control a power control signal generated by the motion control processor to thereby drive the power regulator such that the vehicle travels in the desired manner.

32. A method as claimed in claim 31 wherein the parameter is a measurement value of displacement derived from operation of a displacement sensor.

33. A method as claimed in claim 31 wherein the parameter is an estimated value of displacement derived from an integration over time of the power control signal.

34. Apparatus substantially as hereinbefore described with reference to and as shown in any of the accompanying drawings.

35. A method substantially as hereinbefore described with reference to and as shown i any of the accompanying drawings.