CA2052344C - Apparatus for mounting a camera on a vehicle - Google Patents

Abstract

Apparatus for mounting a camera on a vehicle, such as a helicopter, to dampen the transmission of undesired motion from the vehicle when moving to the camera. The apparatus includes an elongated suspendable structure with a large inertia relative to the camera. The structure has a boom, for supporting the camera, extending from one end of an attachment portion of the structure, and a counter-balance beyond an opposite end of the attachment portion. The apparatus is rigidly securable to the vehicle and resiliently compliant damping is operable between the vehicle and the attachment portion of the suspendable structure to dampen the transmission of undesired motion from the vehicle to the camera. The damping has a center of compliance substantially at the center of gravity of the suspendable structure.

Description

20~23~
APPARATUS FOR MOUNTING A CAMERA ON A VEHICLE

This invention relates to apparatus for mounting a camera on a vehicle such as a helicopter, so that image motion is reduced.
Many devices have been disclosed which provide ways to reduce unwanted image motion while viewing remotely and/or recording images (video/film) from moving vehicles and the like, and to control the format of the scene viewed.
Unwanted image motion caused by flight of a helicopter may be considered to be of two kinds, namely rapid "vibration" and slower oscillatory (flight) motion. The rapid vibration is generally due to lack of sufficient rigidity of the camera mounting apparatus. Multiple resonances and low damping coefficients of resonating members contribute to n jittery" images.
Slower unwanted image motion results from aircraft oscillations and/or angular oscillations of the support structure either as it attempts to follow the aircraft fuselage or as it has angular deviations induced when responding to the (lateral) acceleration forces imposed on it.
Existing systems, such as helicopter nose-mounts, side-mounts and underslung mounts, generally yield unsatisfactory results, particularly with respect to unwanted image motion. This is because most mounts are rigidly attached to the helicopter fuselage and thus impart either excessive high frequency image motion (vibration) ~05~
and/or residual perturbations known as "flight-motiona or in the case of gyrostabilized mounts, are concentrated masses, and thus incapable of being positioned on a helicopter to provide unencumbered views (e.g.
"forward looking" aspects with large elevation field-of-view), without severly altering the weight and balance of the helicopter.
It is an object of this invention to provide a simple mount to reduce the random image motion which would otherwise occur, for a large camera system(s) on a moving vehicle or the like, particularly a helicopter, in a position such that the extremities of the vehicle do not intercept even a very large (both high and wide) field of view.
Another object of the invention is to meet the requirements of flight worthiness on a variety of helicopters, while retaining the facility for average-skilled personnel to assemble and disassemble the apparatus to allow for shipping in an economical fashion.
According to the invention there is provided an apparatus for mounting a camera on a vehicle, including an elongated suspendable structure with a large inertia relative to the camera. The suspendable structure has a boom, extending from one end of an attachment portion of the structure, that is rigidly attachable to the camera, and a counter-balance beyond an opposite end of the attachment portion. Attachment means are provided and are rigidly securable to the vehicle and resiliently compliant damping 20523~

means are operable between the attachment means and the attachment portion of the suspended structure to dampen the transmission of undesired motion from the vehicle to the camera. The center of compliance of the damping means is substantially at the center of gravity of the suspended structure.
In one embodiment of the invention, the damping means is preferably gaseous and may include at least one resiliently compliant gaseous cushion connected to a reservoir to receive from and return gas to the cushion.
The suspended structure may have a structural tube and the reservoir could include the structural tube. There may also be a variable size orifice at or between the reservoir and the gaseous cushion to enable the damping characteristics to be altered.
In a preferred embodiment, there are four resiliently compliant gaseous cushions disposed in a rectangular configuration in a substantially horizontal plane. There may also be an angularly movable platform on which the camera is mounted during use, that is angularly movable by controlled counter-torqued motors which provide smooth motion during angular movement and a rigid connection between the camera and the suspendable structure at other times.
The suspendable structure may also be made from light weight tubing in a form of a truss which is readily assembled and disassembled.
Also in accordance with the invention is a helicopter 2~23~4 having a fuselage with the apparatus for mounting the camera rigidly secured by the attachment means to the underside thereof. The helicopter may have a cargo hook and the attachment means may be secured to the cargo hook.
The invention will be more fully understood with reference to the following description and drawings, in which:
Fig. 1 is an elevational view of a camera mounting apparatus in accordance with a preferred embodiment of the invention attached to the underside of a helicopter fuselage and carrying a camera;
Fig. 2 is a perspective view of the suspended structure of the camera mounting apparatus;
Fig. 3 is a perspective view (partly in dotted outline) of a typical cargo hook assembly of a helicopter in engagement with a securing pin of the attachment means of the camera mounting apparatus;
Fig. 4 is a perspective view of the attachment means;
Fig. 5 is a perspective view of the attachment means carrying the medial portion of the suspendable structure through the intermediary of four gaseous cushions;
Fig. 6 is a perspective view of two gaseous cushions and surrounding parts;
Fig. 7 is a perspective view of a platform for the camera; and Fig. 8 is an exploded view of a joint which allows the platform to be tilted.
Reference is made to Fig. 1 which illustrates a 20~23~
preferred embodiment of the invention as an apparatus represented generally by the number 30, in its operational position under the fuselage of a helicopter 32 (chain dotted line). It can be seen that a suspended structure 34 has a camera 36 mounted ahead of the nose of the helicopter 37, on a front boom 38 which extends forwardly (left as drawn) from a medial portion 40. This allows the camera 36 to record a large field of view without including the helicopter. The weight of the camera 36 and front boom 38 is balanced by a rear boom 42 which extends rearwardly (right as drawn) to a counter-balance 44 and also carries a battery (not shown) in a battery carrier 46, to supply power to the camera 36 and its mount (to be described). The importance of balancing the suspended structure will become evident later in this description.
To hold the suspended structure 34 under the helicopter 32 between laterally spaced landing skids 47 (only one of which is shown), there is an attachment section (to be described) which is rigidly connectable to the helicopter by means of its cargo hook, thus placing the centre of gravity of the apparatus 30 at the location usually used to carry loads (below the center of gravity of the helicopter).
Additionally, so that transmission of motion from the helicopter to the suspended structure is compliant yet damped, there are four gas cushions 48, 50, 52, 54 disposed between the attachment section (not shown) and the suspended structure 34 (gas cushions 50, 52 are hidden behind gas cushions 48, 54 in Fig. l).

20523~
Fig. 2 is a perspective view of the suspended structure 34 which has a truss configuration of minimum weight tubing that will provide a rigid structure to carry the camera.
The camera (not shown) is mounted on platform 56 which is supported by joint assemblies 58, 60 which allow tilt articulation (to be described). The joint assemblies 58, 60 are carried on strut assemblies 62, 64 rigidly attached to cross struts 66, 68. The rear ends of the strut assemblies 62, 64 are slotted to receive the ends of a forwardly extending truss assembly 70 where they are held in place by pins (not shown) extending through holes provided. A
similar rearwardly extending truss assembly 72 supports the battery carrier 46 and the counter-balance 44. Both truss assemblies 70, 72 have two rigid side assemblies 74, 76, 78, 80 each having diagonal struts 82, 84, 86, 88 to provide rigidity, and reinforcing transversely extending box structures 90, 92, 94, 96 positioned at points along their length.
Each side 74, 76 of the forwardly extending truss assembly 70 is connected to the corresponding side 78, 80 of the rearwardly extending truss assembly 72 by upper and lower longitudinal tubes 98, 100, 102, 104 which form the frame of the medial portion 40. Each tube 98, 100, 102, 104 is provided with an end fitting 106 which seals the tube against a small positive air pressure within and provides means for connecting the tube to the end of one truss side.
The upper and lower tubes on each side are connected by spacers 108, 110, 112, 114 so as to form a rigid rectangular 20~23~4 structure, which may be made more rigid, if desired, by diagonal guy wires 116 (shown on one side only, dashed lines).
Fig. 3 is a perspective view of a standard cargo hook attachment for a Bell 206 type helicopter. Such an accessory is normally fitted with a hook member 118, which is used to carry external loads beneath the fuselage, and to be remotely n unhooked" by the pilot so as to jettison the load in the event of an emergency. A pin 120 engages the hook 118 to secure the attachment section 122 (Fig. 4) to the helicopter.
The steps involved in securing the attachment section 122 will be described with reference to Fig. 4. The attachment section 122 has transversely-extending channel sections 124, 126 forward and rearward of the pin 120. The pin 120 is held by two screws 128, 130 so that, by rotating the screws 128, 130, the pin 102 can be raised and lowered relative to the channel sections 124, 126 to adjust the height of the attachment section 122 to meet mounting requirements. Channel sections 124, 126 support a length of "I" section 132, 134 on either side, each of which carries at both ends a block 136 shaped and padded so as to engage the generally horizontal, lower surface of the corresponding tube section which forms part of the landing skid assembly 47 of the helicopter 32 (not shown). The screws 120, 130 cause the pin 120 to pull against the cargo hook 118 (Fig.

3), and can thus be made to apply more or less equally distributed upward forces on all four points of contact of 20~234~
the blocks 136 with the skid tubes (not shown), resulting in a rigid external connection securing the attachment section 122 to the helicopter 32.
So that undesired motion is not transmitted from the rigidly secured attachment section 122 to the suspended structure, Fig. 5 shows one means of providing a resiliently compliant and energy absorbing (cushioned) support for the suspended structure 34 of Fig. 2. The lower sides of the ends of the upper tubes 98, 100 are fitted with the gas cushions 48, 50, 52, 54 which are of a type commonly found on commercial road vehicles and which, when suitably inflated, have both compliant and damping (energy dissipative) properties. The lower sides of the air cushions 48, 50, 52, 54 are supported on two cross members 138, 140 held by four hangers 142, 144, 146, 148 attached at the four corners of the "I" beams 132, 134 so that the center of gravity of the suspended structure lies in essentially the same plane as the air cushions. Cross struts 150, 152, 154, 156 transfer the side forces imparted at the gas cushions, through the blocks 136 to the helicopter skid tubes.
Gas cushions 48, 54 are shown in Fig. 6. The gas in the upper tube 98 is connected with the front gas cushion 48 through a hole 158 within the end fitting 106, and the rear air cushion 54 is connected with the lower tube 102 through a pipe 160 arranged externally to the end fittings 106. In both cases, the gas is "pumped" from the cushion to the tube during operational flexing of the cushion and is "metered"

20a23~4 through an orifice 162 in its associated end fitting 106.
The size of the orifice 162 is adjustable to provide the dissipative damping required for a given loading (camera system payload) and particular helicopter flight conditions. The compliant characteristics and damping characteristics of the system may be further refined by selectively cross coupling the various air cushions either directly in a fixed fashion or through valves which may in turn be (passively) operated by the accelerations imposed by the flight motions or actively operated by electronic means from appropriate acceleration sensors on the mount itself and/or on the helicopter fuselage.
The damping in the case of the helicopter should optimally result in a natural resonance of the suspended structure at a frequency below 2 Hertz, and also a controlled amount of energy absorption, having characteristics that optimally dissapate more energy as the fuselage vibration is increased. Fluidics are to be avoided as they result in frequency dependent characteristics.
Assembly and disassembly of the apparatus 30 will be explained with reference to Figs. 4 and 5. The hangers 142, 144, 146, 148 are bolted to the ~I" beams 132, 134 and may be, but are not intended to be, removed on a regular "pack-up-and-move" basis. Similarly, the channels 124, 126 may be disassembled from the ~I~ beams 132, 134. The cross members 146, 148 are attached to the hangers 142, 144, 146, 148 with removable pins and secured by standard cowling lock pins (not shown).

20~23~4 The gas cushions 48, 50, 52, 54 are secured by screws to the end fittings 106 and are clamped to the cross members 138, 140. The truss assemblies 70, 72 (Fig. 2) may be dismantled to four simple one-plane entities for high density packing. If more guy wires 164 (Fig. 2) are used to make the truss assemblies more rigid, they can remain in place in the dismantled trusses for transportation.
However, they can be readily detached if required.
Referring now to Fig. 2, the battery carrier 46 is located at the rear of the rear truss 72 and may carry a gel cell battery suitable for operation of the remote controls associated with the mount, the camera, lens(es) and other accessories. The counter-balance 44 is similarly attached and weights are used for adjusting the postion of the center of gravity of the assembly to coincide with the gas-suspension center (and the cargo-hook attachment point). The rear truss 72 may also carry a lightweight electrical gas pump connected to the tubes 98, 100, 102, 104 through unidirectional regulator valves to compensate for variations in temperature and altitude, and maintain the desired difference in gas pressure within and outside the systems. Carbon dioxide, air or other gas(es) may be used as pressurizing gas.
The operational effectiveness of the apparatus 30 is attributable to: the rigidity of the entire suspended structure 34; its large inertia; the long and wide "support base~ of the compliant cushions 48, 50, 52, 54; the suspended structure 34 being mounted with compliance and 20~'~344 damping relative to the semi-flexible ~vibrating) fuselage, (which in flight is subjected to continuous small attitudinal adjustments about all three axes as it is dragged through the air by the helicopter rotor); and the mass distribution of the suspended body about the effective "compliance centre", particularly in the same horizontal plane. These factors effectively reduce the tendency for the lateral accelerations of the fuselage to cause angular motion of the suspended structure 34 (Fig. 2). The "compliance center~ is defined as a point at the intersection of the lines joining diagonally disposed gas cushions, when the gas cushions are inflated to equal pressures. As mentioned, the compliance center is ideally located to be coincident with the center of gravity of the suspended body, in all three directions, but may be located somewhat forwardly or rearwardly, for different helicopter requirements of center of gravity position relative to the cargo hook, by adjusting the gas pressure difference accordingly in the forward and rear gas cushions 48, 50, 52, 54 so as to maintain the coincidence of the center of gravity of the helicopter and the compliance center.
The adaptibility of the system to different payloads (camera/lens systems) is readily apparent, since the mass balance and the gas pressure as well as the variable orifices may be adjusted to cater for a large variation of payload weights and distributions, and the apparatus can be mounted on a wide range of helicopters by suitable modification to the attachment section 122 (Fig. 4).

20~2344 Figs. 7 and 8 show details of how the camera moves and is mounted on the suspended structure 34. The "tilt-cradle"
platform 56 (Fig. 7) comprises rectangular tubing suspended from an attachment plate 166 at either end, with a joint assembly 168, 169 allowing the platform and therefore the camera view to be tilted up or down. The preferred joint assembly 168, 169 has high rigidity about two axes and low friction/stiction properties about the rotational axis. The rigidity of the "tilt-cradle" platform 56 is augmented by the camera base plate 170, the camera body 36 (chain dotted lines) and the securing clamps 172. The platform 56 is an integral part of an independently rigid "tilt-joint"
structure having two mirror-image joint assemblies 168, 169 using opposing pairs of large angular contact ball bearings, or a combination of one such bearing 174 (see Fig. 8) and a roller thrust bearing 176, assembled with appropriate separators and sleeves 177. The outboard ends of the joint assembly have an end-plate 178 which is rigidly attached to strut assemblies 62, 64 (Fig. 7). The two end-plate and strut assemblies are separated and secured by cross-struts 66, 68.
The bearings 174, 176 allow a support plate 180, which is mounted on the attachment plate 166, to rotate freely about the joint assemblies 168, 169.
Each tilt joint has a large "driven" pulley 182 mounted independently on its own bearing 184 (Fig. 8) which is free to rotate relative to both the support plate 180 and the end plate 178. This freedom allows manual balancing of the 2Q~2344 platform 56 about its tilt axis. A screw 184 near the periphery of the pulley can be engaged in the appropriate hole 186 in the support plate 180 to transmit torque to the platform 56 when the pulley 182 is driven by a belt 188 (Fig. 7) guided by rollers 190 around a small sprocket 192 driven by a motor-gearhead 194. The motor provides for remote controlled tilting of the camera with a proportional velocity, or a position servo system, the input to which may be from a manual/electric transducer such as a joystick or potentiometer or an "automatic" source such as an analogue or digital recording (tape or other) or a "tracking" signal derived electronically from an on-board video image (not shown).
Smooth tilt rotation is achieved against varying (balance and aerodynamic) loads by using two tilt drives, one at each end of the tilt platform (set up as previously described), which are continuously torqued in opposing directions to the extent needed to counteract externally applied torques (aerodynamic drag and "unbalance").
Electrical commands can be sent to each drive independently so as to retain the "opposing bias", but superimpose equal directional drive torques to each.
A cable with a suitable umbilical disconnect can be provided to interconnect a control box with a console in the fuselage to provide an operator with all the controls for the camera and tilt platform.
Airworthiness is achieved by the lightweight rigid structure, the small frontal area presented to the airstream 2a52344 and the "floating" inertia of the structure resisting transmission of small flight perturbations of the fuselage in all directions, but (softly) constrained to follow the longer term fuselage attitude changes about all three axes.
The separate power source to operate the system eliminates a requirement for aircraft power. The cargo-hook attachment and umbilical disconnect provide for jettison of the entire structure in flight under emergency conditions.
Various structures to support the camera and connect the suspended structure through the gas cushions to the helicopter or other vehicle, and doing so in an equivalent manner to those described in this specification, are within the scope of this invention defined in the following claims. Also use with other arrangements and types of compliant damping means having a gaseous cushion with or without a secondary volume to change the damping characteristics, as well as other types of compliant damping means such as rubber or eurathane springs are also within the scope of the invention defined in the following claims.
From the foregoing description of a preferred embodiment, it will be noted that the present invention also provides:-a) Apparatus for mounting a camera(s) to a vehicle to reduce undesired coupling between them, comprising, an elongated rigid structure, compliantly suspended at its mass center, such that the natural resonance is significantly below the frequencies applied by the vehicle; and an attachment means rigidly securable to said vehicle with a resilient means of fastening said structure to said attachment means.
b) A compliance means comprised of at least one gaseous cushion connected to a reservoir to receive gas from and return gas to the cushion.
c) A structural member, integral to the said rigid structure, containing inherently, the said reservoir.
d) A suspended structure which carries an angularly movable platform on which the camera(s) is mounted during use, said platform being rotatable by two servo-controlled motors and appropriate drive means, which separately also apply preset, but counter-directional torques through the drive means to the said platform.

Claims (9)

1. Camera mounting apparatus securable to a helicopter by attachment to a raisable cargo hook carried by the helicopter on the bottom of the fuselage thereof, said apparatus comprising:
an attachment frame securable to the cargo hook so as to rigidly engage the bottom of the helicopter, when the cargo hook has been raised, with the centre of gravity of the apparatus being located essentially below the cargo hook, an elongated rigid structure having a front end portion for carrying a camera and a rear end portion carrying a counterweight, said elongated rigid structure having a medial portion suspended from at least three spaced resilient compliant members carried by the attachment frame and being essentially parallel to the helicopter yaw plane, when the attachment frame is secured to the helicopter, said resilient compliant members providing an effective compliant couple to the helicopter fuselage about all three axes with the compliance centre coinciding approximately with the centre of gravity of the apparatus, whereby the effects of helicopter fuselage vibration and higher oscillatory frequencies of flight motion are reduced and the camera can be mounted so that no part of the helicopter appears in the field of view of the camera.

2. Camera mounting apparatus according to claim 1 wherein said compliant members comprise gas-filled cushions inflated so as to provide the suspended mass with a resonance frequency which best attenuates undesired forces from being applied to the camera.

3. Camera mounting apparatus according to claim 1 wherein said compliant members comprise gas-filled cushions connected to closed reservoirs which receive and return gas from and to their respective cushions through a controlled or preset orifice to create controlled dissipation of vibrational energy.

4. Camera mounting apparatus according to claim 3 wherein said reservoirs are formed by structural tubes of the suspended structure and are connected to the gas cushions through respective variable size orifices.

5. Camera mounting apparatus according to claim 1 wherein the suspended structure comprises a truss of light-weight tubing which is readily assembled and disassembled.

6. Camera mounting apparatus according to claim 3 wherein the counterweight comprises a battery to operate the camera, and an air compressor, air regulator and control means to maintain a constant differential pressure in the gas-filled cushions regardless of temperature changes or of natural atmospheric pressure changes or atmospheric pressure changes resulting from altitude changes.

7. Camera mounting apparatus according to claim 1 wherein the counterweight comprises a wheel rotatable about a substantially vertical axis, said axis being rigidly connected to the suspended rigid structure in such a manner as to couple roll moment, which is significantly smaller than moment about the other two axis to pitch moment through its gyroscopic moment, thereby lowering the natural frequency of the suspended structure about the roll axis and making the vibrational response of the system more nearly equal about all three axes.

8. Camera mounting apparatus according to claim 1 wherein the camera is mounted on a platform slung from a pair of horizontal joints rigidly attached tothe front of the structure and which provide for tilting the camera by a remote operator during flight, but otherwise rigidly connected to the structure, each joint being rotated by a motor coupled through gears and/or belts and having small fixed electrical currents applied to the motors such that small opposing torquesare applied to the platform from each side so as to remove any lost-motion inherent in the drive trains and to prevent rotation unless commanded by the operator.

9. Camera mounting apparatus according to claim 8 wherein the drive motors are individually connected to the output terminals of servo-amplifiers located adjacent to the motors and which are adjusted to provide a small fixed offset current in each motor, the polarity of which causes opposing torques to be applied to the ends of the camera platform, an identical command voltage being applied to the inputs of the servo-amplifiers by the cameraman's controller.