WO1998059330A1

WO1998059330A1 - G-seat

Info

Publication number: WO1998059330A1
Application number: PCT/GB1998/001845
Authority: WO
Inventors: David Burgoyne
Original assignee: Cranfield Aerospace Limited
Priority date: 1997-06-24
Filing date: 1998-06-24
Publication date: 1998-12-30
Also published as: GB9713339D0; AU8121298A

Abstract

A G-seat (200) comprising a seat portion (12); a back portion (14); and a modular G-force simulator associated with the seat portion (12) and the back portion (14). The modular G-force simulator comprises a seat module (202) for providing heave cues and a back module (240) for providing surge and/or sway cues. The seat module (202) comprises a drive sub-module, a transmission sub-module operatively connected to the drive sub-module and an adaptor sub-module operatively connected to the transmission sub-module and adapted to secure the transmission sub-module to the seat portion. The back module (240) comprises a drive sub-module, a transmission sub-module operatively connected to the drive sub-module and an adaptor sub-module operatively connected to the transmission sub-module and adapted to secure the transmission sub-module to the back portion. The structure of the drive sub-module and the transmission sub-module of the seat and back modules are sufficiently similar to enable them to be used interchangeably in either the seat or back module.

Description

G-SEAT

This invention relates to a G-seat, ie, a seat that is adapted to simulate a G-force in at least one direction. In flight simulators it is important to provide effective motion cueing for the pilot using the simulator. Humans can sense motion through the eyes, through vestibular organs in the inner ear, through somatic sensors in the skin, and through kinaesthetic sensors (which detect limb movement).

One way to provide motion cueing is to use a motion platform having a seat attached to it. The platform is movable by a control system, in response to flight control signals generated by the simulator. Motion platform systems can provide effective vestibular cueing, but tend to be less effective at providing somatic and kinaesthetic cueing. Furthermore, motion platforms have the considerable disadvantage that they are extremely expensive. Furthermore, motion platforms are unable to sustain G-cues.

G-seats (which are also known as dynamic seats) have been developed in an attempt to mitigate the disadvantages of motion platforms. They contain movable panels, within the seat, which act on parts of the pilot's body in order to simulate the effects of motion. G-seats can simulate G-forces by providing G-cues to the pilot; the G-forces can be simulated in one direction, or in a plurality of directions. Moreover, G-seats, unlike motion platforms, can provide sustained G- cueing.

The simplest G-seats provide heave cueing (which is also known as normal G cueing). Heave cueing simulates forces applied upwardly and downwardly to the aircraft. This is achieved by a mechanism in the seat portion of the G-seat, which can increase or decrease pressure onto the pilot's thighs and buttocks. Simultaneously, the pilot's shoulder straps can be loosened or tightened, and the pilot's height, relative to a visual display system, can be raised or lowered.

More complicated G-seats also provide surge cueing (which is also known as longitudinal cueing). Surge cueing provides simulation of acceleration and deceleration of the aircraft. This is achieved by a mechanism in the back portion of the G-seat, which can increase or decrease the pressure on the pilot's back

More complicated G-seats may also provide sway cueing (which is also known as lateral cueing) Sway cueing provides simulation of sideways movement of the aircraft This is achieved by a mechanism that drives the seat portion and/or the back portion from side to side

The earliest G-seats provided only heave cueing The seat cushion consisted of a number of air bags, which deflated under the application of positive

G in order to expose protrusions which increased the pressure on the pilot's buttocks This deflation simultaneously lowered the pilot in the seat and relieved tension in the pilot's shoulder straps

Subsequently, developers aimed to increase the response time, le, the speed at which the cues were generated, so that the onset of the cue occurred at the same time as it would in a real flight environment - the early pneumatic G-seats were not suitable for this purpose, due to their limited bandwidth This led to the development of sophisticated G-seats having electro-hydraulic elements

We have previously developed a G-seat having electro-hydraulically actuated plates in the seat portion and the back portion thereof This G-seat was capable of providing the pilot with rapid motion cues corresponding to heave, surge and sway The design of this seat was very complicated, involving a large number of moving parts and complex hydraulic mechanisms

We have now found a way to simplify the construction of a G-seat, while providing improved response and smoothness Broadly, we achieve this by providing a G-seat with a means to apply and remove pressure to selected parts of the pilot's anatomy using modular units that operate entirely non-hydraulically We have also made significant improvements to the structure of the apparatus used to provide the G-cues

According to one aspect of the invention we provide a G-seat comprising a seat portion, a back portion, and a modular G-force simulator associated with the seat portion and the back portion, wherein the modular G-force simulator comprises a seat module for providing heave cues and a back module for providing surge and/or sway cues, wherein the seat module comprises a drive sub- module, a transmission sub-module operatively connected to the drive sub-module and an adaptor sub-module operatively connected to the transmission sub-module for providing an interface between the transmission sub-module and the seat portion, wherein the back module comprises a drive sub-module, a transmission sub-module operatively connected to the drive sub-module and an adaptor sub- module operatively connected to the transmission sub-module for providing an interface between the transmission sub-module and the back portion, and wherein the drive sub-module and the transmission sub-module of the seat and back modules are sufficiently similar to enable them to be used interchangeably in either the seat or back module

The drive sub-module creates a driving force which is transmitted through the transmission sub-module to the adaptor sub-module and into the seat or back portion Thus, by correct control of each drive sub-module, movement can be imparted to the seat and/or back portion in order to provide the required G-cues The provision of a modular construction for the drive sub-modules and the transmission sub-modules simplifies the design of the G-seat considerably, and makes it possible for parts of the G-force simulator to be replaced easily The modular construction also makes it possible to reduce the manufacturing cost of the components Whilst the construction of the drive sub-module and transmission sub- module of the seat and back portion may be substantially identical, there will usually be minor differences in the design For example, in practice, the amount of movement required in the seat portion is different from the amount of movement required in the back portion, and the drive and/or transmission sub-modules may be adapted to cope with this difference The important point is that the drive and transmission sub-moαules are interchangeable with only relatively minor modifications being required This is different from the prior art, where it would simply not be possible to interchange the components for the seat portion with the components for the back portion It is preferred that the G-seat provides both surge cueing and sway cueing In order to achieve this, the back module advantageously comprises a for/aft module for providing surge cues and a lateral module for providing sway cues, the for/aft module comprising a drive sub-module, a transmission sub-module operatively connected to the drive sub-module and an adaptor sub-module operatively connected to the transmission sub-module for providing an interface between the transmission sub-module of the for/aft module and the lateral module, and the lateral module comprising a drive sub-module, a transmission sub-module operatively connected to the drive sub-module and an adaptor sub-module operatively connected to the transmission sub-module for providing an interface between the transmission sub-module of the lateral module and the back portion, the drive sub-modules and the transmission sub-modules of the seat module, the for/aft module and the lateral module being sufficiently similar to enable them to be used interchangeably in either the seat module, the for/aft module or the lateral module This arrangement could be provided the other way around, i e , with the lateral module connected to the for/aft module, and the for/aft module connected to the back portion

It should be understood that, in accordance with this aspect of the invention, and the other aspects of the invention discussed below, it is possible for the seat module to be provided with an up/down module for providing heave cues, and a lateral module for providing sway cues The arrangement of the up/down module and the lateral module may be the same as the arrangement of the for/aft module and the lateral module described above

The interface that the adaptor sub-module provides with the seat and/or back portion may include a direct connection to the seat and or back portion However, it is not essential that the adaptor sub-module is secured to the seat or back portion All that is necessary is that an interface is provided between the adaptor sub-module and the seat and/or back portion, so that the motion generated by the drive and transmission sub-modules can be transmitted to the seat or back portion Preferably, the adaptor sub-module of the seat module includes a pressure plate which is disposed in or next to the seat portion, and preferably the adaptor sub-module of the back module includes a back pressure plate which is disposed in or behind the back portion The pressure plate can engage a cushion of the seat or back portion in order to provide the required G-cues When the pressure plate is acting on the seat portion, it is preferred that the pressure plate acts through a cut-out in the seat portion, so that the pressure plate acts directly on the seat cushion In a first preferred embodiment the drive sub-module comprises a drive means having an output shaft, and the transmission means comprises a mechanical linkage directly secured to the output shaft and directly secured to the adaptor sub-module In accordance with the first embodiment of the present invention, the output shaft is rotatably movable, and the mechanical linkage is secured thereto in such a way that it pivots about the axis of rotation of the output shaft, the arrangement being such that the pivotal movement of the mechanical linkage directly moves the seat or back portion By means of this arrangement, rotation of the output shaft of less than 360° can cause movement of the seat or back portion Preferably the arrangement is such that a rotation of the output shaft of 5° to 50° causes the full range of movement of the seat or back portion

The mechanical linkage may be rigid with the seat or back portion, but it is preferred that the mechanical linkage is such that relative pivotal movement is possible between the mechanical linkage and the seat or back portion This aim can be achieved, for example, by providing a pivotal connection between the mechanical linkage and the adaptor sub-module In one construction, the mechanical linkage may comprise two portions, a first of which is fixed to the output shaft, and a second of which is fixed to adaptor sub-module, the first and second portions being pivotally connected to one another In another construction, mechanical linkage may be secured to the adaptor sub-module by means of a connection that allows pivoting, such as a spherical bearing A combination of these two constructions may be used, if desired

In a particularly preferred construction we provide shoulder strap tensioning means preferably in the form of a shoulder strap attachment formation on the mechanical linkage, the shoulder strap attachment formation being provided with means for attaching a shoulder strap thereto This arrangement makes it possible for the amount of movement of the pressure plate during movement thereof to be different from the amount of movement of the shoulder straps Preferably, the shoulder strap attachment formation extends further away from the output shaft than the point at which the mechanical linkage is secured to the adaptor sub-module (which point may be the point at which the mechanical linkage is secured to the seat pressure plate of the adaptor sub-module) This has the effect that when the mechanical linkage pivots, the seat pressure plate moves a smaller amount than the shoulder strap attachment means, hence the change in the pressure applied by the seat pressure plate can be different to the tension applied through the shoulder straps In the preferred construction, the shoulder strap attachment formation is secured to the first portion of the mechanical linkage

As the shoulder strap attachment formations move downwardly, the shoulder straps apply a force to the shoulders of the pilot It is possible to set the maximum force applied by the shoulder straps by setting the maximum load that can be applied by the heave cue drive means Alternatively, or in addition, a suitable safety spring assembly, such as a tensator spring associated with each shoulder strap, may be provided to prevent the load exceeding a maximum value The maximum load for the shoulder straps would usually be 260 N in order to comply with standard safety regulations

In the first embodiment, the seat and/or back modules preferably include feedback means for providing information about the displacement of the seat and/or back portions The feedback means of the seat module is preferably sufficiently similar to the feedback means of the back module to enable it to be used interchangeably in either the seat module or the back module The feedback means may be a part of either the drive sub-module, the transmission sub-module or the adaptor sub-module The feedback means may take a number of different forms For example, the feedback means may be adapted to measure the angular displacement of the output shaft of the drive means a rotary potentiometer, a resolver, an encoder, or an AC or DC rotary or variable differential transformer would be suitable for this purpose In addition, or instead, the feedback device may be adapted to measure the linear displacement of the pressure plate - this may be achieved by measuring the displacement of the pressure plate itself or of part of the mechanical linkage, a linear voltage displacement transducer (LVDT) or a potentiometer would be suitable for this purpose Control means can be provided to control operation of the seat and/or back modules The control means is preferably operatively connected to the feedback means, and can be connected to flight controls operated by the pilot

In a second preferred embodiment the drive sub-module comprises a drive means having an output shaft, and a translation means secured to the output shaft for translating rotary movement of the output shaft into a linear movement of the translation means The translation means is operatively connected to the transmission sub-module

Advantageously, the translation means comprises a planetary roller screw assembly Planetary roller screw assemblies are, in themselves, well known, although they have not previously been used in this application We have found that the use of a planetary roller screw assembly results in a particularly smooth movement of the transmission and adaptor sub-modules, which makes it possible to produce excellent G-cues

The planetary roller screw assembly comprises a threaded shaft rotatable with the output shaft of the drive means, and a nut mounted on the threaded shaft and in contact with the shaft through a plurality of roller screws arranged in a planetary fashion around the shaft Rotational movement of the threaded shaft relative to the nut causes linear movement of the nut along the shaft It will, of course, be appreciated that the threaded shaft of the planetary roller screw assembly may be secured to the output shaft of the drive means or it may be integral therewith In the second embodiment, the transmission sub-module preferably comprises a first transmission arm operatively connected to the drive sub-module, and a second transmission arm pivotally connected to the first transmission arm The second transmission arm is operatively connected to the adaptor sub-module Most preferably, the first transmission arm is operatively connected to the nut of the planetary roller screw assembly The first transmission arm is preferably arranged such that the linear movement of the translation means causes the first transmission arm to pivot about a point spaced from the point at which it is connected to the second transmission arm The transmission sub-module desirably includes a guide means in which the second transmission arm is received, the guide means serving to guide the movement of the second transmission arm along a substantially linear path

Each module may be provided with a single transmission sub-module or with more than one transmission sub-module Preferably, the seat module and the for/aft modules are provided with a pair of the transmission sub-modules, and the lateral module is provided with a single one of the transmission sub-modules In the second embodiment, the most important common features of the sub-modules are the provision of a substantially identical motor as the drive means, a substantially identical planetary roller screw assembly, and a substantially identical guide means for receiving the second transmission arm

In the second embodiment, the adaptor sub-module is preferably operatively connected to the second transmission arm The precise form of the adaptor sub-module depends upon whether the module is being used to provide heave, surge or sway cues The adaptor sub-module may be partially integral with the second transmission arm, in which case the second transmission arm may be replaced depending on the particular application of the module Advantageously, the seat module of the second embodiment is provided with shoulder strap tensioning means The shoulder strap tensioning means preferably comprises a shoulder strap tensioning member pivotally mounted to the seat module and adapted to be secured to a shoulder strap The tensioning member is desirably arranged so that when the drive sub-module drives the transmission sub-module in one direction, the tension in the shoulder strap is increased, and when the drive sub-module drives the transmission sub-module in an opposite direction, the tension in the shoulder strap is decreased In the preferred construction, the tensioning member is engaged and pivoted by the first and/or second transmission arm when it/they move in one direction, thereby increasing the tension in the shoulder strap, and the tensioning member is disengaged by the first and/or second transmission arm when it/they move in an opposite direction, thereby decreasing the tension in the shoulder strap

In the second embodiment, the seat and/or back modules preferably include feedback means for providing information about the displacement of the seat and or back portions The feedback means of the seat module is preferably sufficiently similar to the feedback means of the back module to enable it to be used interchangeably in either the seat module or the back module The feedback means may be a part of either the drive sub-module, the transmission sub-module or the adaptor sub-module The feedback means may be arranged to measure the rotation of the output shaft of the drive means, in which case the feedback means may comprise a resolver, an encoder or a rotary potentiometer However, it is preferred that the feedback means is arranged to measure the linear displacement of the translation means, in which case the feedback means is preferably a LVDT Control means can be provided to control operation of the seat and/or back modules The control means is preferably operatively connected to the feedback means, and can be connected to flight controls operated by the pilot

The seat and/or back modules may be provided with a housing which houses, or provides a support for, at least part of the drive sub-module, the transmission sub-module and, possibly, the adaptor sub-module The translation means and the drive means may be completely enclosed within the housing in order to provide soundproofing against the noise created by the module It is preferred that the guide means comprises linear recess provided in the housing As noted above, it is preferred that the seat module and the for/aft module comprise a pair of the transmission sub-modules we prefer that said transmission sub-modules are disposed on opposite sides of the housing According to another aspect of the present invention there is provided a G-seat comprising a seat portion, a back portion, and a G-force simulator associated with the seat portion and/or the back portion, wherein the G-force simulator comprises a seat module for providing heave cues and/or a back module for providing surge and/or sway cues, and wherein the seat and/or back module comprises a drive sub-module, a transmission sub-module operatively connected to the drive sub-module and an adaptor sub-module operatively connected to the transmission sub-module for providing an interface between the transmission sub- module and the seat or back portion, and wherein the transmission sub-module provides a mechanical, non-hydraulic linkage between the drive sub-module and the adaptor sub-module, whereby G-cues can be transmitted non-hydraulically from the drive means to the seat portion and/or the back portion

It is preferred that the G-seat can provide heave, surge and sway cueing To achieve this, the G-seat is preferably provided with a seat module and a back module, and that the back module comprises a for/aft module and a lateral module as described above In this aspect of the invention the G-seat may be operated entirely by means of non-hydraulic components, i e , the operation is entirely electromechanical

According to another aspect of the present invention there is provided a G-seat comprising a seat portion, a back portion, and a G-force simulator associated with the seat portion and/or the back portion, wherein the G-force simulator comprises a seat module for providing heave cues and/or a back module for providing surge and/or sway cues, and wherein the seat and/or back module comprises a drive sub-module comprising a drive means having an output shaft, a transmission sub-module having a mechanical linkage directly secured to the output shaft, and an adaptor sub-module directly secured to the mechanical linkage for providing an interface between the transmission sub-module and the seat or back portion, whereby rotational movement of the output shaft is translated directly to the mechanical linkage and through the mechanical linkage to the seat or back portion In the most advantageous embodiment the direct mechanical linkage is such that the mechanical linkage is fixed to the output shaft, so that it rotates therewith, and applies a force to the seat or back portion, whereby movement of the output shaft results in movement of the seat or back portion Other preferred features of the seat and/or back modules are described above in the description relating to the first embodiment

It is possible for the mechanical linkage associated with the back pressure plate to have substantially the same structure as the mechanical linkage associated with the seat pressure plate However, when the G-force simulator is used to provide both surge and sway cues, it is preferred that the means for providing the surge and sway cues are integrated In this embodiment, the back module includes a drive means for providing surge cues and separate drive means for providing sway cues, each having an output shaft, and the output shafts are operatively connected to the back portion by means of a single surge/sway mechanical linkage and a single adaptor sub-module, le the mechanical linkage for providing surge cueing is the same as the mechanical linkage for providing sway cueing

In this embodiment, the surge/sway mechanical linkage preferably comprises a first portion mounted to the output shaft of the surge cue drive means The output shaft of the surge cue drive means is preferably rotatably movable, and the first portion of the surge/sway mechanical linkage is desirably secured to the output shaft such that it pivots about the axis of rotation of the output shaft It is preferred that the sway cue drive means is mounted to the first portion of the surge/sway mechanical linkage - the surge cue drive means can be arranged at one end of the first portion, with the sway cue drive means at the other end of the first portion The surge/sway mechanical linkage preferably comprises a second portion mounted to the output shaft of the sway cue drive means The output shaft of the sway cue drive means is preferably rotatably movable, and the second portion of the surge/sway mechanical linkage is desirably secured to the output shaft such that it pivots about the axis of rotation of the output shaft Preferably the second portion of the surge/sway mechanical linkage is secured to the adaptor sub- module The second portion is preferably pivotally mounted to the adaptor sub- module, this pivotal mounting is preferably such that the second portion can pivot freely in all directions relative to the adaptor sub-module (and hence to the back portion) - this can be achieved, for example, by means of a spherical bearing When the output shaft of the surge cue drive means is driven, it causes the first portion and the sway cue drive means to pivot towards or away from the back portion This causes the back portion to move forwardly, or rearwardly, owing to the provision of the second portion between the sway cue drive means and the adaptor sub-module When the output shaft of the sway cue drive means is driven, it causes the second portion to pivot laterally with respect to the back portion This causes the back portion to move laterally, leftwards or rightwards

According to another aspect of the present invention there is provided a G-seat comprising a seat portion, a back portion, and a G-force simulator associated with the seat portion and/or the back portion, wherein the G-force simulator comprises a seat module for providing heave cues and/or a back module for providing surge and/or sway cues, and wherein the seat and/or back module comprises a drive sub-module comprising a drive means having an output shaft, and a translation means secured to the output shaft for translating rotary movement of the output shaft to a linear movement, a transmission sub-module comprising a first transmission arm operatively connected to the translation means of the drive sub-module, a second transmission arm pivotally connected to the first transmission arm, and a guide means, the first transmission arm being arranged such that the linear movement of the translation means causes the first transmission arm to pivot about a point spaced from the point at which it is connected to the second transmission arm, and the guide means receiving the second transmission arm and serving to guide the movement of the second transmission arm along a substantially linear path, and an adaptor sub-module operatively connected to the second transmission arm of the transmission sub-module for providing an interface between the second transmission arm and the seat or back portion

Advantageously, the translation means comprises a planetary roller screw assembly, as described above Other preferred features of the seat and back modules are described above in the description relating to the second preferred embodiment

The G-seat according to the aspects of the invention described above can be used to provide any one of heave cues, surge cues and sway cues, or combinations thereof We prefer that the G-seat is used to provide heave cueing, surge cueing and sway cueing In order to provide heave cues, part of the seat module is movable upwardly to simulate positive G and is movable downwardly to simulate negative G The uppermost position represents the maximum positive G, and the lowermost position represents the maximum negative G In order to provide surge cues, part of the for/aft module is movable forwardly to simulate acceleration and is movable rearwardly to simulate deceleration The forwardmost position represents the maximum acceleration, and the rearmost position represents the maximum deceleration In order to provide sway cues, part of the lateral module is movable leftward to simulate lateral movement in a πghtward direction and is movable πghtward to simulate lateral movement in a leftward direction Although it is possible to simulate sway cues in either or both of the seat and the back portion, we prefer to simulate sway cues in the back portion only

The seat and/or back modules may be provided with stop means for limiting the extent to which the transmission means can move For example, the stop means may be arranged to act on the drive means, on the output shaft of the drive means, on part of the transmission sub-module or on part of the adaptor sub- module In the first embodiment described above, the drive means and the output shaft may be disposed in a housing, and the mechanical linkage may protrude through an aperture in the housing, so that the walls of the aperture in the housing act as the stop means The seat pressure plate may also be provided with means for attaching a lap strap thereto In some circumstances it may be desirable to provide the seat pressure plate with means to attach a vee strap thereto The attachment of the lap strap and/or vee strap to the seat pressure plate has the effect of loosening or tightening the straps as the seat pressure plate rises or lowers It is possible for a tensator spring to be used in association with the lap strap and the vee strap

The attachment means for the shoulder strap, the lap strap and the vee strap may be conventional fasteners for the straps used in aircraft seats

The seat and back portions are preferably supported by a support frame that is fixed relative to a support surface such as the floor The seat portion would normally include a seat cushion, and the back portion would normally include a backrest or back cushion It is desirable that any shoulder straps extend through apertures provided in the backrest or back cushion A headrest may also be provided on the back portion

As noted above, in order to simulate positive G the seat pressure plate moves upwardly, and in order to simulate negative G the seat pressure plate moves downwardly In order to improve the quality of the simulation an eye height module is preferably provided for moving the seat and back portions relative to the frame This enables the pilot's eye height to be changed when the seat pressure plate is moved upwardly or downwardly by the seat module For example, when the seat pressure plate is moved upwardly, the seat portion can be moved downwardly relative to the frame by the eye height module, and when the seat portion is moved downwardly, the seat portion can be moved upwardly relative to the frame by the eye height module The amount of the movement caused by the eye height module may be greater than, less than, or equal to the amount of the movement caused by the seat module

Preferably the eye height module comprises a drive sub-module adapted to be secured to the frame, a transmission sub-module operatively connected to the drive sub-module, and an adaptor sub-module operatively connected to the transmission sub-module for providing an interface between the frame and the seat and/or back portion The drive sub-module of the eye height module preferably comprises a drive means having an output shaft, and a translation means secured to the output shaft for translating rotary movement of the output shaft into a linear movement of the translation means, the translation means being operatively connected to the transmission sub-module of the eye height module The translation means preferably comprises a planetary roller screw assembly comprising a threaded shaft rotatable with the output shaft of the drive means, and a nut mounted on the threaded shaft and in contact with the shaft through a plurality of roller screws arranged in a planetary fashion around the shaft

It is possible for the drive sub-module and the transmission sub- module of the eye height module to be sufficiently similar to the drive sub-module and the transmission sub-module of the seat and back modules to enable them to be interchangeably used in the seat module and the back module.

Advantageously, the means to displace the seat portion relative to the frame can also be used to generate other effects such as buffeting and runway rumble. The drive means of the seat module, the for/aft module, the lateral module and the eye height module may comprise a conventional electric motor. We prefer that the drive means comprises a DC brushless motor.

The seat module, the back module and/or the eye height module can incorporate a gearing means to provide a gear change between the drive means and the adaptor sub-module. The planetary roller screw assembly can provide the desired gearing means. Gearing is especially important for the seat module, the for/aft module and the eye height module; it is less important for the lateral module, as the forces involved are smaller.

The eye height module is a particular feature of the invention and it could be used in G-seats that do not incorporate the types of seat and back module described above.

It is preferred that the G-seat according to the invention is powered using a single phase power source. Thus, a single phase power source may be providing to power the seat module and/or the back module and/or the eye height module. This is different from earlier G-seats, and motion platforms, which use a 3- phase power source. This can be achieved by providing a power supply unit, adapted to be connected to the single phase power source, in combination with one or more power amplifiers. Each power amplifier can be connected to a respective one of the drive means of the drive sub-modules. This feature enables the G-seat to be powered from a standard A/C mains source, such as the 240V source available in the UK. This feature may also be used with G-seats that do not include the mechanical linkage described above.

According to another aspect of the present invention there is provided a flight simulator comprising: a visual display means for simulating an environment surrounding an aircraft; a G-seat as described above; a flight control system operable by a pilot sitting in the G-seat; and control means for controlling the visual output of the visual display means and the drive means of the G-seat at least partly in response to commands given to the flight control system by the pilot

The visual display means may comprise a conventional VDU for use with a personal computer Alternatively, the visual display unit comprises a dome display system Preferably the display system has a relatively high resolution forward area and a relatively low resolution peripheral area

The control means may comprise a conventional computer processor, programmed with appropriate flight simulator software In complex flight simulators the control means may be quite complicated, incorporating flight models specific to the aircraft being simulated

It will be clear from the foregoing that the invention can be used to provide a multi-axis G-seat, le, a G-seat in which G-forces are simulated in more than one direction By using the heave, surge and sway G-simulators described above, it is possible to simulate G-forces in three mutually perpendicular directions, le, up and down, forwards and backwards, and from side to side

The G-seat according to the present invention has a number of advantages over the prior art The provision of a direct non-hydraulic mechanical linkage makes it possible to dispense with complex mechanisms, and also makes it possible to reduce the number of parts of the G-seat It also enables the G-seat to respond more quickly - this causes the onset of the heave, surge and/or sway cues to occur more quickly, which provides a more realistic simulation of the forces to which a pilot would be subjected in a real aircraft The provision of a modular structure makes it possible to manufacture G-seats less expensively, and makes them simpler to repair or replace The G-seat according to the invention may be used to simulate a wide variety of aircraft seats It is especially useful for simulating the seats of high performance aircraft and helicopters It may also be used in simulating the seats of ground vehicles

According to another aspect of the invention there is provided a transmission apparatus for controlling movement of a movable structure, comprising drive means having an output shaft, a planetary roller screw assembly compπsing a threaded shaft rotatable with the output shaft of the drive means, and a nut mounted on the threaded shaft and in contact with the shaft through a plurality of roller screws arranged in a planetary fashion around the shaft, whereby rotation of the threaded shaft causes linear movement of the nut therealong, a first transmission arm operatively connected to the nut, a second transmission arm pivotally connected to the first transmission arm, a guide means, and an adaptor operatively connected to the second transmission arm, the adaptor providing an interface between the second transmission arm and the movable structure, wherein the first transmission arm is arranged such that movement of the nut causes the first transmission arm to pivot about a point spaced from the point at which it is connected to the second transmission arm, and the guide means receives the second transmission arm and serves to guide the movement of the second transmission arm along a substantially linear path

The movable structure may be, for example, a seat portion or a back portion of a G-seat, in which case the transmission apparatus may be provided in the form of a seat module, a back module, a for/aft module or a lateral module, and the adaptor is equivalent to the adaptor sub-module described above

The transmission apparatus may have any of the features of the seat or back modules described above The transmission apparatus according to the invention can be arranged to work with equipment other than G-seats It may be used in any application where a controlled displacement of a piece of equipment is required The transmission apparatus may be arranged to receive information from an input device, such as a control loader The transmission apparatus may be used, for example, with a throttle box or a helmet loader

Reference is now made to the accompanying drawings, in which Fig 1 is a side view of a first embodiment of a G-seat according to the invention,

Fig 2 is a rear view of a seat shown in Fig 1 , Fig 3 is a view of part of the G-seat shown in Fig 1 , on an enlarged scale, Fig. 4 is a view on lines 4-4 of Fig. 3;

Fig. 5 is a view on lines 5-5 of Fig. 3;

Fig. 6 is a view of part of the G-seat shown in Fig. 1 , on an enlarged scale; Fig. 7 is a view on lines 7-7 of Fig. 6;

Fig. 8 is a schematic diagram of a flight simulator incorporating the G- seat shown in Fig. 1 ;

Fig. 9 is a view similar to Fig. 5, showing an alternative embodiment; and Fig. 10 is a side view of a seat module attached to a second embodiment of a G-seat according to the invention;

Fig. 11 is an end view of the seat module shown in Fig. 10;

Fig. 12 is a bottom view of the seat module shown in Fig. 10;

Fig. 13 is a view of part of the seat module shown in Fig. 10, on an enlarged scale;

Fig. 14 is a view of part of the seat module shown in Fig. 12, on an enlarged scale;

Fig. 15 is a side view of a back module attached to the second embodiment of G-seat according to the invention; Fig. 16 is a side view of an embodiment of an eye height module for use in a G-seat according to the invention;

Fig. 17 is a top view of the eye height module shown in Fig. 16;

Fig. 18 is a side view of the second embodiment of G-seat incorporating the seat module, the back module and the eye height module shown in Figs. 10 to 17; and

Fig. 19 is a rear view of the G-seat shown in Fig. 18.

In the drawings a first embodiment of a G-seat generally designated

10 has a seat portion generally designated 12 and a back portion generally designated 14. The seat portion 12 and the back portion 14 are provided on a chassis 16 which is slidably mounted to a frame 18. The frame 18 is fixed to a support surface (not shown) such as the floor. The seat portion 12 includes a seat cushion 20, and the back portion 14 includes a backrest 22 A headrest cushion 24 is secured to the frame 18, above the backrest 22

The G-seat includes a G- force simulator for simulating the G-forces to which a pilot is exposed during flight The G-force simulator includes a seat module generally designated 26 (Figs 3, 4 and 5), for providing heave cues, and a back module generally designated 28 (Figs 6 and 7) for providing surge and sway cues

The seat module 26 comprises an adaptor sub-module including seat pressure plate 30, a drive sub-module including drive means in the form of a DC brushless motor 32 having an output shaft 34, and a transmission sub-module including a seat mechanical linkage 36 directly connecting the output shaft 34 to the seat pressure plate 30 The output shaft 34 is rotatable about an axis extending normal to the plane of the drawing The mechanical linkage 36 comprises a rigid first portion comprising two arms 38, one end of each arm 38 is secured to the output shaft 34 so that rotation of the output shaft 34 causes the arms 38 to pivot about the axis of rotation of the output shaft 34 The mechanical linkage 36 also comprises a rigid second portion 40 which is fixedly secured to the underside of the seat pressure plate 30 The second portion 40 comprises two spaced plates 42 Each arm 38 is secured to one of the plates 42 by means of a pin 44 which extends through an aperture 46 in each of the arms 38, and through an aperture 47 in each of the plates 42 This arrangement enables the arms 38 to pivot about the pins 44

A shoulder strap attachment formation 48 is integral with the arms 38 The formation 48 is provided with attachment means 50 and 52 to which shoulder straps 54 and 56 are attached The attachment means 50 and 52 are provided at an end of the formation 48 that is remote from the pin 44 The shoulder straps preferably extend through cut-outs provided in the backrest 22

For safety reasons, the maximum pilot shoulder load is set at 130 N per shoulder, so the motor 32 is selected to provide a maximum load of 260 N at the point of attachment of the shoulder straps 54 and 56 to the formations 48 The seat pressure plate 30 is provided with two spaced raised formations 58 thereon, which serve the function of applying pressure to the thighs of the pilot The seat pressure plate is also provided with lap strap attachment means 60 and 62, to which lap straps 64 and 66 are attached In addition, the seat pressure plate is provided with a vee strap attachment means 68, to which a vee strap 70 is attached

The drive motor 32 is provided with a housing 140 having a slot 142 therein The slot 142 allows the arms 38 to extend from the output shaft 34, through the housing 140 to the second portion 40 The slot 142 is large enough to permit the arms 38 to pivot through the angle necessary to move the seat pressure plate 30 between its uppermost and lowermost positions The slot 140 has walls 142 which act as a stop means to limit the amount of pivotal movement of the arms 38 - this is an important safety feature The limitation on the maximum load of the motor 32 provides a secondary safety feature in the event that the walls 142 fail to stop the arms 38 A tensator spring (not shown) may also be provided for each shoulder strap 54 and 56 to prevent the force through the shoulder straps from exceeding a predetermined maximum value

The back module 28 comprises an integrated for/aft module and lateral module The for/aft and lateral module include an integrated adaptor sub- module comprising a back pressure plate 72 The for/aft module comprises a surge cue drive sub-module in the form of a DC brushless motor 74 having an output shaft 76 The lateral module comprises a sway cue drive sub-module in the form of a DC brushless motor 78 having an output shaft 80 The for/aft module and the lateral module include an integrated surge/sway transmission sub-module comprising a mechanical linkage 82 directly connecting the output shafts 76 and 80 to the back pressure plate 72 The output shaft 76 is rotatable about an axis extending normal to the plane of the drawing, while the output shaft 80 is rotatable about an axis in the plane of the drawing

The mechanical linkage 82 comprises a rigid first portion comprising two arms 84, one end of each arm 84 is secured to the output shaft 76 so that rotation of the output shaft 76 causes the arms 84 to pivot about the axis of rotation of the output shaft 76 The first portion of the mechanical linkage 82 is further provided with an interconnecting member 86, which extends between the arms 84 at the end of the arms 84 remote from the output shaft 76, this provides the first portion of the mechanical linkage 82 with a generally U-shaped configuration The motor 78 is fixedly secured to the interconnecting member 86

The surge/sway mechanical linkage 82 also comprises a rigid second portion 88, one end of which is secured to the output shaft 80 so that rotation of the output shaft 80 causes the second portion 88 to pivot about the axis of rotation of the output shaft 80 The other end of the second portion 88 is secured to the rear of the back pressure portion 72 by means of a spherical bearing 90 which enables the second portion 88 to pivot freely relative to the back pressure portion 88

The drive motor 74 is provided with a housing 146 having a slot 148 therein The slot 148 allows the arms 84 to extend from the output shaft 76, through the housing 146 The slot 148 is large enough to permit the arms 84 to pivot through the angle necessary to move the back pressure plate 72 between its forward most and rearward most positions The slot 146 has walls 150 which act as a stop means to limit the amount of pivotal movement of the arms 88 - this is an important safety feature

The G-seat 10 is also provided with an eye height module 92 for displacing the chassis 16 - and hence the seat portion 12 and the back portion 14 - relative to the support frame 18 The eye height module 92 comprises a drive sub- module comprising drive means, in the form of a DC brushless motor 94, and a planetary roller screw assembly The planetary roller screw assembly comprises a threaded shaft 96 and a flanged roller screw nut 100 which is mounted on the shaft 96, and has an internal screwthread adapted to cooperate with the external screwthread on the shaft 96 The shaft 96 is secured to an output shaft (not shown) of the motor 94 A bearing assembly 98 is provided at the end of the shaft 96 remote from the motor 96 The bearing assembly 98 is secured to the frame 18 and serves to prevent vibration or deflection of the shaft 96 The roller screw nut 100 is fixedly secured to the chassis 16 by means of a mounting bracket 102 The roller screw nut 100 is rotatably mounted on the shaft 96, so that rotation of the shaft 96 causes the roller screw nut 100 to move along the shaft 96 This movement causes the chassis 16 to slide upwardly or downwardly relative to the frame 18

The motor 94 includes a resolver (not shown) for providing feedback about the amount of rotation of the shaft 96, but the feedback provided by the resolver is inadequate when the shaft 96 rotates through more than 360° In order to solve this problem a LVDT 104 is provided, in addition to the resolver, to facilitate control of the amount of displacement of the chassis 16 relative to the frame 18 In Fig 8 the G-seat 10 is shown incorporated in a flight simulator Some of the parts in Fig 8 are the same as the parts in Figs 1 to 7, and like parts have been designated with like references numerals However, the representation of the components in Fig 8 is highly diagrammatic

The G-seat 10 in the flight simulator shown in Fig 8 is provided with the seat module 26, the back module 28 and the eye-height module 100 shown in Figs 1 to 7 Fig 8 illustrates one form of flight simulator, and it will be appreciated that it could be provided in many different forms The flight simulator illustrated in Fig 8 is of a relatively simple type the G-seat 10 could, of course, be used in more complicated types of flight simulator, if desired

The flight simulator is provided with flight control means 106 by means of which the pilot controls the simulated flight Typically the flight control means includes a joystick for controlling pitch and roll, a rudder for controlling yaw, and other controllers for controlling other aircraft functions, such as throttle or collective

The signals generated by the flight control means 106 are fed to a simulator controller 107, which generates signals representing the inputs made to the flight control means 106 by the pilot, these signals are fed to a G-seat controller

108 via a line 150 The simulator controller 107 also generates signals for controlling the visual output of a display system 112

The control means 108 also generates signals for controlling the G- seat 10 In order to control the heave G-simulator 26 a heave control signal is fed to the drive motor 32 via a line 116 in order to control the surge and sway simulator

28, a surge control signal is fed to the drive motor 74 via a line 118, and a sway control signal is fed to the drive motor 78 via a line 120 In order to control the displacement of the chassis 16 relative to the support frame 18, a displacement control signal is fed to the drive motor 94 via a line 122

The control means 108 requires feedback from the drive motors 32, 74, 78 and 94 in order to tell it when the correct position has been reached To this end the drive motors 32, 74, 78 and 94 are provided with feedback devices in the form of resolvers 124, 126, 128 and 130 respectively The resolvers 124, 126, 128 and 130 measure the amount of rotation of the output shafts of the motors 32, 74 and 78 and 94, and pass this information back to the control means via lines 132, 134, 136 and 138 respectively The motor 94 also incorporates the linear displacement transducer 104 as part of its feedback device

From the foregoing description the operation of the flight simulator will be clear to a person skilled in the art

When the pilot pulls the joystick backwards the flight simulator will simulate an upward movement of the aircraft The control means 108 receives an appropriate signal via the line 150 and instructs the drive motor 32 to raise the seat pressure plate 30, thereby applying pressure to the buttocks and thighs of the pilot Simultaneously, the control means 108 instructs the drive means 94 to lower the chassis 16 relative to the frame 18, so that the eye height of the pilot is lowered Similarly, when the pilot pushes the joystick forwards the flight simulator will simulate a downward movement of the aircraft The control means 108 receives an appropriate signal via the line 150 and instructs the drive motor 32 to lower the seat pressure plate 30, thereby reducing pressure on the buttocks and thighs of the pilot Simultaneously, the control means 108 instructs the drive means 94 to raise the chassis 16 relative to the frame 18, so that the eye height of the pilot is raised

When a pilot pushes the joystick to the left, or activates a rudder pedal to yaw to the left, the flight simulator will simulate an leftward movement of the aircraft The control means 108 receives an appropriate signal via the lines 150 and instructs the drive motor 78 to move the back pressure plate 72 laterally to the right Similarly, when a pilot pushes the control stick to the right, or activates a rudder pedal to yaw to the right, the flight simulator will simulate an rightward movement of the aircraft The control means 108 receives an appropriate signal via the lines 150 and instructs the drive motor 78 to move the back pressure plate 72 laterally to the left

When the pilot increases the throttle setting, the flight simulator will simulate acceleration of the aircraft The control means 108 will instruct the drive motor 74 to move the back pressure plate 72 forwardly This will increase the pressure on the back of the pilot Similarly, when the pilot decreases the throttle setting, or activates the air brakes, the flight simulator will simulate deceleration of the aircraft The control means 108 will instruct the drive motor 74 to move the back pressure plate 72 rearwardly This will decrease the pressure on the back of the pilot

It will be appreciated that more than one of the motors 32, 74, 78 and 94 may be operated simultaneously Also the motors 34, 74, 78 and 94 may be used to simulate effects other than those described above For example by making very rapid small changes in the height of the chassis 16 relative to the support frame 18 with the motor 94 it is possible to simulate effects such as buffeting and runway rumble

Fig 9 shows an alternative embodiment of mechanical linkage between the seat pressure plate 30 and the output shaft 34 Many of the parts in the embodiment of Fig 9 can be identical to the parts in Fig 3, and like parts have been designated with like reference numerals

In Fig 9, the plate 42 has been replaced with a Y-shaped member 80 and a spherical bearing 82, and the pins 44 have been replaced with a single pin 86 The Y-shaped member 80 is secured to the seat pressure plate 30 via the spherical bearing 82, which will permit the Y-shaped member to pivot laterally (as well as forwardly and rearwardly) with respect to the seat pressure plate 30

The Y-shaped member 80 is provided with two arms 88 and 90, each of which is pivotally secured to the pin 86 Two sleeves 84 are provided around the pin 86 Each sleeve 84 extends between one of the arms 88 and 90 and one of the arms 38 The sleeves 84 serve to maintain the Y-shaped member 80 at the correct position on the pin 86 The components of the G-seat can all be provided with their own housings so that no moving parts are visible

In Figs 10 to 19 a second embodiment of G-seat according to the invention is generally designated 200 A number of the components of the G-seat 200 have been identified by the same reference numerals as some of the components of the G-seat 10 Such components are either identical or very similar Figures 10 to 14 illustrate an embodiment of a seat module generally designated 202 The seat module 202 comprises a housing 202a which houses a drive sub-module, two transmission sub-modules and an adaptor sub-module The drive sub-module includes a drive means in the form of a DC brushless motor 204 which is secured to the housing 202a The motor 204 has an output shaft (not shown), and a resolver 208 provides feedback by measuring the angular displacement of the output shaft The resolver 208 also provides commutation for the motor 204 A rotary-to-linear movement translation means in the form of a planetary roller screw assembly 210 is secured to the output shaft The planetary roller screw assembly 210 includes a threaded shaft 212 fixed at one end to the output shaft for rotation therewith, and fixed at the other end to the housing 202a via a bearing 214 The planetary roller screw assembly 210 also includes a nut 216 mounted on the shaft 212 The nut 216 is rotatable relative to the shaft 212 and is fixed against rotation so that rotation of the shaft 212 causes axial movement of the nut 216 along the shaft 212 A member 218 is rigidly secured at one end to the nut 216 through a mounting plate 217 A LVDT 224 is secured to the housing 202a by a clamp 222, and provides feedback by measuring the displacement of the nut 216 As shown in Fig 12, the member 218 is substantially T-shaped Each transmission sub-module comprises a first transmission arm 222, and an end of each first transmission arm 222 is secured to a respective end of the top of the "T" of the member 218 Each first transmission arm 222 is pivotally secured to the housing 202 via a pivot 226, and is pivotally secured to the member 218 via a pivot 228

Each transmission sub-module further includes a second transmission arm 229 which is pivotally secured to the first transmission arm 222 at a pivot 230 Each transmission sub-module further includes a guide means in the form of a linear slot 232 provided in the housing 202a The second transmission arm 229 of each transmission sub-module is slidably received in the slot 232, as illustrated in

The adaptor sub-module comprises the upper end of the second transmission arms 229 of the transmission sub-modules, together with a seat pressure plate 234 to which said second transmission arms 229 are secured The seat pressure plate 234 performs the same function as the seat pressure plate 30 (and may have a substantially identical construction)

The seat module 202 also includes a shoulder strap tensioning means in the form of a pair of substantially L-shaped strap tensioning members 236 The members 236 are pivotally mounted to the housing 202a at pivots 238 A first portion 236a of the members 236 is adapted to be engaged by a respective one of the first transmission arms 222, and a second portion 236b of the members 236 is adapted to be secured to a respective one of the shoulder straps 54 and 56

When the motor 204 rotates the output shaft, the shaft 212 of the planetary roller assembly 210 rotates therewith, and this is translated into an axial movement of the nut 216 of the planetary roller screw assembly 210 The axial movement of the nut 216 causes the member 218 to move with the nut 216 The movement of the member 216 causes the first transmission arms 222 to pivot about the pivots 226 The pivotal movement of the first transmission arms 222 causes the second transmission arms 229 to slide upwardly or downwardly in the slots 232 The direction of movement of the second transmission arms 229 depends upon the direction of movement of the nut 216 if the nut 216 moves away from the motor 204, the second transmission arms 229 move upwardly, and if the nut 216 moves towards the motor 216, the second transmission arms 229 move downwardly The movement of the second transmission arms 229 is transmitted to the pressure plate 234 and hence to the seat cushion 20 of the seat portion 12 The movement can be controlled to provide the appropriate cues to a pilot in the seat 200

It will be clear that the rotational movement of the shaft 212 is converted into a linear movement of the nut 216 by the planetary roller screw assembly 210 Furthermore, the linear movement of the nut 216 is converted into a pivotal movement of the first transmission arms 222, and the pivotal movement of the first transmission arms 222 is converted into a substantially linear movement of the second transmission arms 229 It will be appreciated that, in the absence of the guide slots 232, the second transmission arms would move through a slight arc, for this reason, the width of the guide slot 232 is made slightly larger than the width of the second transmission arms 229 in order to ensure that the arms 229 can move freely in the slot 232 It will be appreciated that there are other ways of solving this problem, such as providing an undercut portion on the second transmission arms 229

As the second transmission arms 229 are moved downwardly, the first transmission arms 222 will engage the portion 236a of the strap tensioning members 236 This causes a tension to be applied to the shoulder straps 54 and 56 As the second transmission arms 229 are moved upwardly, the first transmission arms 222 will disengage from the portion 236a of the strap tensioning members 236

This causes the tension applied to the shoulder straps 54 and 56 to be released

Fig 15 illustrates a back module, generally designated 240, in position on a back portion 14 of the G-seat 200 The back module 240 comprises a for/aft module 242 and a lateral module 244

The for/aft module 242 comprises a drive sub-module which is substantially identical to the drive sub-module of the seat module 202 and a transmission sub-module which is substantially identical to the transmission sub- module of the seat module 202 The adaptor sub-module of the for/aft module 242 is different from the adaptor sub-module of the seat module 202 The adaptor sub- module of the for/aft module 242 is provided with a formation 246 on the end of each of the second transmission arms 229, which is adapted to be secured to the housing 202a of the lateral module 244 (in Fig 15 only one of the two formations 246 is shown) The lateral module 244 comprises a drive sub-module which is substantially identical to the drive sub-module of the seat module 202 and a transmission sub-module which is substantially identical to the transmission sub- module of the seat module 202 However, the lateral module 244 has only one of the transmission sub-modules The adaptor sub-module of the for/aft module 242 is different from the adaptor sub-module of the seat module 202 The adaptor sub- module of the for/aft module 242 is arranged to provide an interface between the second transmission arm 228 and the back portion 14 of the G-seat 200

The lateral module 244 is also provided with an alignment means 248 which is adapted to engage a cooperating alignment means 248a on the back portion 14 The alignment means comprise cooperating formations (such as, for example, a wheel and a horizontally arranged track for receiving the wheel) which ensure that when the back portion 14 is moved laterally by the lateral module 244, the movement of the back portion is kept horizontal

In Figs 16 and 17 an alternative embodiment of eye height module is generally designated 250 The specific construction of the eye height module 250 is different from the eye height module 92, but the principles of its operation are much the same It will be seen from Figs 18 and 19 that the eye height module 250 is secured to the G-seat 200 near the head rest 24 The eye height module 250 comprises a housing 252 attached to mounting plates 254 and 256 The module 250 is fixed to the chassis 16 of the G-seat 200 by means of the mounting plates 254 and 256

The module 250 further comprises a drive means in the form of a DC brushless motor 258 A planetary roller screw assembly 260 is secured to an output shaft of the motor 258 The planetary roller screw assembly 260 comprises a threaded shaft 262 having a nut 264 mounted rotatably thereon The shaft 262 is mounted to the chassis 16 via the mounting 256 and a roller bearing assembly 266 The roller bearing assembly helps to reduce vibration or displacement of the screw 262, and takes the vertical load generated by moving the seat up and down It will be appreciated that the assembly 266 should be retained vertically to the mounting 256 by a suitable mounting (not shown) or suitable adhesive attached to the outer surface of the assembly 266 and an inner counter bore surface on the mounting 256 A resolver 268 is provided to provide feedback about the amount of rotation of the screw 262 As noted above, the feedback provided by the resolver 268 is inadequate when the screw 262 rotates more than 360°, so a LVDT 270 having an LVDT rod 272 is employed to provide additional information about the displacement of the nut 264 along the shaft 262 (and hence the displacement of the chassis 16 relative to the frame 18)

The nut 262 is mounted to an output mounting plate 274 which is secured to the chassis 16 in the region of the seat portion 12 The seat portion 12 is driven up and down via this attachment An electro-brake assembly 276 provides braking by clamping the end of the shaft 262 The brake body of the electro-brake assembly 276 is attached to the housing 256 A voltage needs to be applied to the electro-brake assembly 276 in order to release the shaft 262 If a voltage is not applied, then the shaft 262 is locked Figs 18 and 19 are similar to Figs 1 and 2 respectively, and show how the seat and back modules 202 and 240, and the eye height module 250, are arranged in the G-seat 200

It will be appreciated that modifications may be made to the invention described above For example the DC brushless motors could be replaced with torque motors Also, the resolvers could be replaced with rotary potentiometers or encoders, or with a feedback device adapted to measure linear displacement, such as a linear voltage displacement transducer or a potentiometer

In another modification the back portion 14 can be provided with a cushion, and the back pressure plate 72 can be arranged to move the cushion This arrangement may be used, for example, when it is desired to simulate a helicopter seat

Claims

1 A G-seat comprising a seat portion, a back portion, and a modular G-force simulator associated with the seat portion and the back portion, wherein the modular G-force simulator comprises a seat module for providing heave cues and a back module for providing surge and/or sway cues, wherein the seat module comprises a drive sub-module, a transmission sub-module operatively connected to the drive sub-module and an adaptor sub-module operatively connected to the transmission sub-module for providing an interface between the transmission sub- module and the seat portion, wherein the back module comprises a drive sub- module, a transmission sub-module operatively connected to the drive sub-module and an adaptor sub-module operatively connected to the transmission sub-module for providing an interface between the transmission sub-module and the back portion, and wherein the drive sub-module and the transmission sub-module of the seat and back modules are sufficiently similar to enable them to be used interchangeably in either the seat or back module

2 A G-seat according to claim 1 , wherein the back module comprises a for/aft module for providing surge cues and a lateral module for providing sway cues

3 A G-seat according to claim 2, wherein the for/aft module comprises a drive sub-module, a transmission sub-module operatively connected to the drive sub- module and an adaptor sub-module operatively connected to the transmission sub- module for providing an interface between the transmission sub-module of the for/aft module and the lateral module, and the lateral module comprises a drive sub- module, a transmission sub-module operatively connected to the drive sub-module and an adaptor sub-module operatively connected to the transmission sub-module for providing an interface between the transmission sub-module of the lateral module and the back portion, and wherein the drive sub-modules and the transmission sub-modules of the seat module, the for/aft module and the lateral module are sufficiently similar to enable them to be used interchangeably in either the seat module, the for/aft module or the lateral module

4 A G-seat according to claim 2, wherein the lateral module comprises a drive sub-module, a transmission sub-module operatively connected to the drive sub- module and an adaptor sub-module operatively connected to the transmission sub- module for providing an interface between the transmission sub-module of the lateral module and the for/aft module, and the for/aft module comprises a drive sub- module, a transmission sub-module operatively connected to the drive sub-module and an adaptor sub-module operatively connected to the transmission sub-module for providing an interface between the transmission sub-module of the for/aft module and the back portion, and wherein the drive sub-modules and the transmission sub-modules of the seat module, the for/aft module and the lateral module are sufficiently similar to enable them to be used interchangeably in either the seat module, the for/aft module or the lateral module

5 A G-seat according to claim 3 or 4, wherein the seat module and the for/aft module include two of said transmission sub-modules and the lateral module comprises one of said transmission sub-modules

6 A G-seat according to any preceding claim, wherein the adaptor sub-module of the seat module includes a pressure plate which is disposed in or next to the seat portion and the adaptor sub-module of the back portion includes a back pressure plate which is disposed in or next to the back portion, and wherein the seat pressure plate engages the seat portion and the back pressure plate engages the back portion order to transmit the required G-cues to the seat and back portions

7 A G-seat according to any preceding claim, wherein the seat and/or back modules include feedback means for providing information about the displacement of the seat and/or back portions

8 A G-seat according to claim 7, wherein the feedback means of the seat module is sufficiently similar to the feedback means of the back module to enable it to be used interchangeably in either the seat module or the back module

9 A G-seat according to claim 7 or 8, wherein the feedback means comprises a rotary potentiometer, a resolver, an encoder, an AC or DC rotary or variable differential transformer and/ or a linear voltage displacement transducer (LVDT)

10 A G-seat according to any preceding claim, further comprising control means to control operation of the seat and/or back modules

11 A G-seat according to claim 10, wherein the control means is operatively connected to the feedback means

12 A G-seat according to any preceding claim, wherein the seat and/or the back module further comprises a housing which houses, or provides a support for, at least part of the drive sub-module and the transmission sub-module

13 A G-seat according to any preceding claim, further comprising a support frame, and wherein the front and back portions are movable relative to the support frame

14 A G-seat according to claim 13, further comprising an eye height module mounted on the frame, which is adapted to move the seat and back portions relative to the frame, wherein the eye height module comprises a drive sub-module adapted to be secured to the frame, a transmission sub-module operatively connected to the drive sub-module, and an adaptor sub-module operatively connected to the transmission sub-module for providing an interface between the frame and the seat and/or back portion

15 A G-seat according to claim 14, wherein the drive sub-module comprises a drive means having an output shaft, and a translation means secured to the output shaft for translating rotary movement of the output shaft into a linear movement of the translation means, the translation means being operatively connected to the transmission sub-module of the eye height sub-module

16 A G-seat according to claim 15 wherein the translation means comprises a planetary roller screw assembly comprising a threaded shaft rotatable with the output shaft of the drive means, and a nut mounted on the threaded shaft and in contact with the shaft through a plurality of roller screws arranged in a planetary fashion around the shaft

17 A G-seat according to claim 16, wherein the drive means of the drive sub- module of the eye height module comprises a DC brushless motor

18 A G-seat according to any preceding claim, wherein the drive sub-module comprises a drive means having a rotatable output shaft, and the transmission means comprises a mechanical linkage directly secured to the output shaft and directly secured to the adaptor sub-module, and wherein the mechanical linkage is secured to the output shaft in such a way that it pivots about the axis of rotation of the output shaft, the arrangement being such that the pivotal movement of the mechanical linkage directly moves the seat or back portion

19 A G-seat according to claim 18, wherein the drive means of the drive sub- module of the seat and/or back module comprises a DC brushless motor

20 A G-seat according to claim 18 or 19, wherein the arrangement is such that a rotation of the output shaft of 5° to 50° causes the full range of movement of the seat or back portion

21 A G-seat according to claim 18, 19 or 20, wherein there is a pivotal connection between the mechanical linkage and the adaptor sub-module 22 A G-seat according to claim 21 , wherein the mechanical linkage comprises two portions, a first of which is fixed to the output shaft, and a second of which is fixed to adaptor sub-module, and a pivotal connection is provided between the first and second portions

23 A G-seat according to any one of claims 18 to 22, wherein a shoulder strap attachment formation is provided on the mechanical linkage, the shoulder strap attachment formation being provided with means for attaching the shoulder strap thereto

24 A G-seat according to claim 23, wherein the shoulder strap attachment formation extends further away from the output shaft than the point at which the mechanical linkage is secured to the adaptor sub-module

25 A G-seat according to any one of claims 1 to 17, wherein the drive sub- module comprises a drive means having an output shaft, and a translation means secured to the output shaft for translating rotary movement of the output shaft into a linear movement of the translation means, the translation means being operatively connected to the transmission sub-module

26 A G-seat according to claim 25, wherein the drive means of the drive sub- module of the seat and/or back module comprises a DC brushless motor

27 A G-seat according to claim 25 or 26, wherein the translation means comprises a planetary roller screw assembly comprising a threaded shaft rotatable with the output shaft of the drive means, and a nut mounted on the threaded shaft and in contact with the shaft through a plurality of roller screws arranged in a planetary fashion around the shaft

28 A G-seat according to claim 25, 26 or 27, wherein the transmission sub- module comprises a first transmission arm operatively connected to the drive sub- module, and a second transmission arm pivotally connected to the first transmission arm and operatively connected to the adaptor sub-module

29 A G-seat according to claim 27 and 28, wherein the first transmission arm is operatively connected to the nut of the planetary roller screw assembly

30 A G-seat according to claim 29, wherein the first transmission arm is arranged such that the linear movement of the translation means causes the first transmission arm to pivot about a point spaced from the point at which it is connected to the second transmission arm

31 A G-seat according to claim 28, 29 or 20, wherein the transmission sub- module also includes a guide means in which the second transmission arm is received, the guide means serving to guide the movement of the second transmission arm along a substantially linear path

32 A G-seat according to claim 31 , wherein the guide means comprises a linear recess provided in the seat module or the back module

33 A G-seat according to claim 32, when dependent upon claim 12, wherein the guide means comprises a linear recess provided in the housing

34 A G-seat according to any one of claims 25 to 33, wherein the seat module is provided with shoulder strap tensioning means comprising a tensioning member pivotally mounted to the seat module and adapted to be secured to a shoulder strap, the tensioning member being arranged so that when the drive sub-module drives the transmission sub-module in one direction, the tension in the shoulder strap is increased, and when the drive sub-module drives the transmission sub- module in an opposite direction, the tension in the shoulder strap is decreased

35 A G-seat according to claim 34, wherein the tensioning member is engaged and pivoted by the first and/or second transmission arm when it/they move in one direction, thereby increasing the tension in the shoulder strap, and the tensioning member is disengaged by the first and/or second transmission arm when it/they move in an opposite direction, thereby decreasing the tension in the shoulder strap

36 A G-seat comprising a seat portion, a back portion, and a G-force simulator associated with the seat portion and/or the back portion, wherein the G-force simulator comprises a seat module for providing heave cues and/or a back module for providing surge and/or sway cues, and wherein the seat and/or back module comprises a drive sub-module, a transmission sub-module operatively connected to the drive sub-module and an adaptor sub-module operatively connected to the transmission sub-module for providing an interface between the transmission sub- module and the seat or back portion, and wherein the transmission sub-module provides a mechanical, non-hydraulic linkage between the drive sub-module and the adaptor sub-module, whereby G-cues can be transmitted non-hydraulically from the drive means to the seat portion and/or the back portion

37 A G-seat according to claim 36, wherein the back module comprises a for/aft module for providing surge cues and a lateral module for providing sway cues

38 A G-seat comprising a seat portion, a back portion, and a G-force simulator associated with the seat portion and/or the back portion, wherein the G-force simulator comprises a seat module for providing heave cues and/or a back module for providing surge and/or sway cues, and wherein the seat and/or back module compπses a drive sub-module comprising a drive means having an output shaft, a transmission sub-module having a mechanical linkage directly secured to the output shaft, and an adaptor sub-module directly secured to the mechanical linkage for providing an interface between the transmission sub-module and the seat or back portion, whereby rotational movement of the output shaft is translated directly to the mechanical linkage and through the mechanical linkage to the seat or back portion 39 A G-seat comprising a seat portion, a back portion, and a G-force simulator associated with the seat portion and/or the back portion, wherein the G-force simulator comprises a seat module for providing heave cues and/or a back module for providing surge and/or sway cues, and wherein the seat and/or back module comprises a drive sub-module comprising a drive means having an output shaft, and a translation means secured to the output shaft for translating rotary movement of the output shaft to a linear movement, a transmission sub-module comprising a first transmission arm operatively connected to the translation means of the drive sub-module, a second transmission arm pivotally connected to the first transmission arm, and a guide means, the first transmission arm being arranged such that the linear movement of the translation means causes the first transmission arm to pivot about a point spaced from the point at which it is connected to the second transmission arm, and the guide means receiving the second transmission arm and serving to guide the movement of the second transmission arm along a substantially linear path, and an adaptor sub-module operatively connected to the second transmission arm of the transmission sub-module for providing an interface between the second transmission arm and the seat or back portion

40 A G-seat according to claim 39, wherein the translation means comprises a planetary roller screw assembly comprising a threaded shaft rotatable with the output shaft of the drive means, and a nut mounted on the threaded shaft and in contact with the shaft through a plurality of roller screws arranged in a planetary fashion around the shaft, and wherein the first transmission arm is operatively secured to the nut

41 A flight simulator comprising a visual display means for simulating an environment surrounding an aircraft, a G-seat according to any preceding claim, a flight control system operable by a pilot sitting in the G-seat, and control means for controlling the visual output of the visual display means and the drive means of the G-seat in response to commands given to the flight control system by the pilot 42 A transmission apparatus for controlling movement of a movable structure, comprising drive means having an output shaft, a planetary roller screw assembly comprising a threaded shaft rotatable with the output shaft of the drive means, and a nut mounted on the threaded shaft and in contact with the shaft through a plurality of roller screws arranged in a planetary fashion around the shaft, whereby rotation of the threaded shaft causes linear movement of the nut therealong, a first transmission arm operatively connected to the nut, a second transmission arm pivotally connected to the first transmission arm, a guide means, and an adaptor operatively connected to the second transmission arm, the adaptor providing an interface between the second transmission arm and the movable structure, wherein the first transmission arm is arranged such that movement of the nut causes the first transmission arm to pivot about a point spaced from the point at which it is connected to the second transmission arm, and the guide means receives the second transmission arm and serves to guide the movement of the second transmission arm along a substantially linear path

43 A G-force simulator comprising at least one transmission apparatus according to claim 42