Patent Application
20180096622
This invention relates to a motion arrangement for moving a load. The motion arrangement may be especially suitable for use for a motion simulator, particularly a land vehicle motion simulator.
Motion simulators are widely used for simulating the motion of vehicles for training purposes and in games installations. A position for an occupant is mounted on a movable platform, and the platform is moved, usually by pistons that are mounted to it, to simulate the motion of the vehicle. In applications such as games where low fidelity of movement is acceptable a simple pivoting arrangement can be used to mount the platform. In higher fidelity applications such as aircraft training simulators the platform is normally mounted on a Stuart platform or hexapod. The Stuart platform has a platform which is connected to a base by six hydraulic or electromechanical pistons. The pistons are pivotally mounted to the base and to the platform. The occupant position is fixed on the platform. The pistons are operated in order to move the platform in three dimensions. Since there are six pistons the platform can be moved in six degrees of freedom, thereby offering realistic simulation.
The Stuart platform is well suited for simulating aircraft motion because it allows substantial movement of the platform in three dimensions. However, in order for significant horizontal motions to be imparted to the platform it must be located well above the base; otherwise the pistons do not have sufficient freedom of movement in the horizontal plane. Typically the base is mounted at ground level, so in order to simulate substantial horizontal motion the platform, with the occupant on it, must be lifted some distance off the ground. This is inconvenient for the occupant. It also means that a large volume of space around the simulator must be available in order to allow the simulator to move freely over its full spatial operating envelope.
Normally a structure is built on the platform to hold the occupant and to give the appearance of the environment that is being simulated. Another problem with the Stuart platform is that the entire weight of the platform and any occupant structure must be borne by the pistons. Therefore, the pistons must be powerful enough not just to move the platform and the structure but also to carry its weight. Applications in which substantial horizontal forces must be imparted include the simulation of motion of land vehicles such as racing cars.
In an alternative design of simulator the load could be supported on six or more rigid rods. At their upper ends the rods are attached to the load by flexible joints. At their lower ends each rod is attached by a spherical joint to a respective sled which runs on one of three horizontal tracks. The tracks are arranged spaced apart but parallel. By moving the sleds on the tracks the load can be moved with six degrees of freedom.
Another design of motion simulator is disclosed in GB 2 378 687. A simulator platform is supported on rocker mechanisms. Each rocker mechanism comprises a rocker arm slidably linked to the side of the platform. The base of the rocker arm is mounted on a first sled which can move the base of the arm along a linear track. A connecting rod extends between the upper end of the rocker arm and a second sled also movable on the track. The attachment point between the platform and each rocker arm can be moved vertically and in one horizontal direction by means of the sleds. Coordinated operation of all the rocker mechanisms is used to manipulate the simulator platform as required. This arrangement has some advantages over other structures described above, but has some drawbacks. In particular the rocker mechanisms must be large if the system is to impose larger amounts of vertical travel, as is required if the system is to simulate the motion of conventional road cars.
There is a need for an improved form of motion system, for example for road vehicle simulators.
According to the present invention there is provided a motion arrangement for moving a load with six degrees of freedom, the motion arrangement comprising: first, second and third primary link elements, each primary link element being (i) rotatably attached to a respective linearly movable driver element and (ii) slidably and rotatably attached to the load; a first intermediate link element attached to the first primary link element and to a fourth linearly movable drive element; a second intermediate link element attached to the second primary link element and to a fifth linearly movable drive element; the first intermediate link element being attached to the first primary link element at a location between the locations where the first primary link element is attached to its respective driver element and to the load, and the second intermediate link element being attached to the second primary link element at a location between the locations where the second primary link element is attached to its respective driver element and to the load.
The motion arrangement may comprise a third intermediate link element attached to the third primary link element and to a sixth linearly movable drive element, the third intermediate link element being attached to the third primary link element at a location between the locations where the third primary link element is attached to its respective driver element and to the load.
The driver elements may be sleds driveable relative to a base.
The motion arrangement may comprise a fourth primary link element, the fourth primary link element being (i) rotatably attached to a respective linearly movable driver element and (ii) slidably and rotatably attached to the load.
The locations at which the first, second and third primary links are coupled to the load may be non-collinear.
There may be means mounted between the load and the driver elements for moving the load relative to a ground or base in a direction parallel to a basal plane. Such means may be slidable couplings between each primary link element and the load.
The linearly movable driver elements may be configured for exclusively linear motion. The linearly movable drivable elements may each be drivable only along a single linear path. Those paths may be coplanar. Those paths may be parallel. The first and second drivable elements may be drivable along a common path. That/those paths may be parallel with the paths along which the first to third drivable elements are drivable. The first and second drivable elements may be drivable by a common linear motor. The fourth and/or fifth drivable elements may be drivable along/by the same path/motor. The third drivable element may be drivable along a path orthogonal to that along which the first and second drivable elements are drivable.
The first primary link element may be slidably attached to the load such that the load can translate with respect to the first primary link element along a first axis. The second primary link element may be slidably attached to the load such that the load can translate with respect to the second primary link element along a second axis. The first and second axes may be convergent. The first and second axes may be coplanar.
The driver elements of the first, second and third primary link elements may be linearly movable in a common plane.
The driver elements of the first, second and third primary link elements may be linearly movable in mutually parallel directions.
The range of motion of the motion arrangement may be such that for all configurations of the arrangement the locations of attachment of the first intermediate link element to the first primary link element and of the second intermediate link element to the second primary link element are lower than the locations of attachment of the first and second primary link elements to the load. The point of attachment of one or more of the intermediate link elements to the respective primary link elements may be such that it is between (a) a plane perpendicular to a line joining the points of attachment of that primary link element to its respective linearly drivable element and to the load and passing through the point of attachment of that primary link element to its respective linearly drivable element and (b) a plane parallel to that plane and passing through the point of attachment of that primary link element to the load. The range of motion of the motion arrangement may be such that that criterion is satisfied for all configurations of the arrangement.
One or more primary link elements may be attached by a respective revolute joint to their respective driver element.
One or more primary link elements may be attached by a respective spherically mobile joint to the load.
Each intermediate link element may be attached by a revolute joint to its respective primary link element. One or more primary link elements may be attached to the load at an attachment joint, and at least one intermediate link may be attached to its respective primary link element by the attachment joint. The attachment joint may be a respective spherically mobile joint to attach the respective primary link element to the load. One or more primary link elements may comprise an element such as a linear coupler by means of which it is slidably attached to the platform.
The driver element of each intermediate link element may be moveable along an axis collinear with the axis along which the driver element of the respective primary link element is movable.
The driver element of each intermediate link element is located inboard or outboard, with respect to the load, of the driver element of the respective primary link element.
Each primary link element may be in the form of a wishbone. Each wishbone may be broader at its attachment to its respective driver element than at its attachment to the load.
Each driver element may be a drivable component of a linear motor. Each driver element may be drivable with respect to a ground.
The motion arrangement may comprise an elastic element acting between components of the motion arrangement to at least partially support the weight of the load. The elastic element may be coupled to act between one of the primary link elements and one of the linearly movable driver elements. The elastic element may be coupled to act between (i) the linearly movable driver element to which one of the first, second and third primary link elements is attached and (ii) one of the fourth and fifth linearly movable driver elements.
The motion arrangement may comprise four primary sleds, each primary sled being coupled to the load by a respective connector strut that is attached to its primary sled by a revolute or spherical joint and to the load by a joint that permits rotation and linear motion, for example a cylindrical joint. Two, three or four of the connector struts may be coupled to respective secondary sleds by further connector struts, each further connector strut being attached to its connector strut by a revolute or spherical joint and to a respective secondary sled by a revolute or spherical joint. One or two of the connector struts may be not provided with such a further connector strut.
The sleds may be arranged so that the primary and secondary sleds serving a particular connector strut are constrained to slide along a common motion axis, for example defined by a single rail.
The load may include a cockpit for an occupant of the simulator.
The load platform 1 of
In more detail,
The load platform may be generally shaped as two trapezoids joined together at one of their parallel sides. Such a load platform may be a six-sided polygon. In this case, the side edges 14, 15 may be convergent with each other at each of their ends. The angle at which the side edges 14, 15 are convergent with each other at each of their ends may be different.
A first portion of the platform may have a pair of tracks attached to the platform and disposed such that they converge. The tracks may be co-planar or not. The tracks may be linear or not. The tracks may be defined by rails or channels or other suitable formations that permit constrained motion, along paths defined by the tracks, between the platform and runners supporting the platform. The tracks may be at the edge of the platform, or the platform may sit on or be suspended from the tracks. There may be a second portion of the platform with a second pair of tracks as set out above. The tracks of the first pair may be co-planar with or not coplanar with the tracks of the second pair. The tracks of the first pair may converge in a direction that is the same or different (e.g. opposite) to the direction in which the tracks of the second pair converge.
In the example of
Four rigid wishbones 4, 5, 6, 7 run between the tracks 2, 3 and the load platform 1. Each wishbone is arranged so that at its upper end it has a single attachment point to the load platform; and at its lower end, where it is broader than at the upper end, it has two attachment points to a respective sled. The attachment structure at the upper end of the wishbones will be discussed in detail below with reference to
In the case of the load platform being generally shaped as two trapezoids joined together, one wishbone of each of the sides 14, 15 are attached to one of the trapezoids and one wishbone of each of the sides 14, 15 are attached to the other trapezoid.
The intermediate links 24, 25 are rigid and extend between respective ones of the wishbones and further sleds 9, 10. Intermediate link 24 extends between wishbone 4 and sled 9. Intermediate link 25 extends between wishbone 5 and sled 10. In this example the sled of each intermediate link runs on the same track as the sled of the wishbone to which it is attached, but it could run on another track, which need not be a track on which the sled of any wishbone runs. In this example the sled of each intermediate link is arranged inboard of the sled of the wishbone to which it is attached, but it could be arranged outboard. In this example the intermediate links are attached to the rear wishbones 4, 5, but they could instead be attached to the front wishbones or to one of the front wishbones and one of the rear wishbones. Each intermediate link is attached flexibly to its sled by a joint 26, 27. This may be a spherical joint or a revolute joint whose axis is perpendicular to the axis of the track on which the sled of that intermediate link runs. Each intermediate link is attached flexibly to its wishbone by a joint 28, 29. This may be a spherical joint or a revolute joint whose axis is perpendicular to the axis of the track on which the sled of that intermediate link runs. Whilst joints 28, 29 are shown being attached to respective wishbone 4, 5, it will be appreciated that one or more of joints 28, 29 may be attached to respective runner 31 associated with its respective wishbone 4, 5.
The linear motors for the front sleds could have common magnetways. The individual linear motors for moving each front sled would then be defined electrically in operation of the motors. The same could be done for the rear sleds.
The rails (e.g. rail 30) along the sides of the platform are non-parallel. They are closer together where they pass over one of the tracks (3) than where they pass over the other of the tracks (2).
The operation of the system will now be described. The positions of the sleds 8-13 are independently controllable by a controller 50. (See
The individual motions described above can be combined to give composite motions of the platform. The intermediate links may be attached to other ones of the wishbones, in which case the behaviours described above can be adapted accordingly.
To provide feedback to the control system illustrated in
In operation the controller 50 receives inputs 56 from position sensors on the sleds 8-13 and control inputs 57 from the user input devices 41, 42. By executing the code 53 processor 51 forms a model of how the simulated vehicle defined by data 55 would behave under those control inputs in the environment defined by data 54. The outputs of that model are a desired position of the platform 1 with six degrees of freedom, sound to be played out by loudspeakers 44 and a video feed to appear on display screen 43. The sound and video are passed at 58 and 59 to the loudspeakers and the display. The desired position is passed to a sled controller 60. The sled controller receives the current positions of the sleds as input at 56 and the desired position and acceleration of the platform with six degrees of freedom at 61 and forms control outputs 62 for each of the six sleds so as to drive them to cause the platform to adopt the required position. The sled controller 60 could be implemented in software or hardware. The processor 51 could be implemented by one or more CPUs. The memory 52 could be implemented by one or multiple physical memory units. The controller 50 could be in a single physical unit or divided between multiple such units.
Springs (not shown in the figures), which could be mechanical or gas springs, can be coupled between each intermediate link 24, 25 and its respective wishbone 4, 5 to help support the weight of the platform. In the case of gas springs the pressure in the springs could be actuated by the controller, e.g. in dependence on the static weight of the load. Mechanical or air springs could be provided so as to act between any pair of the wishbones and/or between any wishbone and its sled and/or between any wishbone and the load. End stop buffers (not shown) can be provided at the ends of the rails to prevent over-travel.
In addition to achieving surge through urging the sleds of each side together or apart, as described above, one or more actuators could be added to drive the surge axis more directly. For example, this could be achieved by mounting one or more linear motor magnetways on the platform, parallel to the platform rails. The slider of each motor would be attached to one of the brackets (e.g. 31) on the distal ends of the wishbones.
To reduce the load on the sled motors during prolonged surge excursions a movable counter-weight could be attached to the mechanism (e.g. to the load or to the distal ends of the wishbones). The counter-weight is arranged to be driven in the opposite direction to the principal load in surge. Motion of the counter-weight could be driven by a motor carried by the load and arranged to drive the counter-weight relative to the load in the surge direction, or by the action of the wishbones on a second pair of rails which are attached to the counterweight and which converge in the opposite direction to the rails that are attached to the load. In one convenient arrangement the counterweight could be provided with one or more pair of rails that converge in the opposite direction to the rails on the load. Those rails could be slidably attached to a pair of the primary supports/wishbones which are attached to opposing rails of the load so that when the attachment points of those supports move together or apart the load and the counterweight will move in opposite directions.
In the arrangement shown in the figures the load is supported by four wishbones, two of which are attached to independently controllable intermediate links. In an alternative configuration the load could be supported by only three wishbones, each of which is flexibly attached to an independently controllable intermediate link. In the latter configuration, there are three linearly movable primary sleds, each of which is carries a respective primary support strut (e.g. a wishbone) which is also flexibly attached to the load. There could be a revolute joint between each primary strut and its sled and a spherical joint between each primary strut and the load. The primary struts are rigid, and preferably attached at their opposite ends to the sleds and the load. There are also three secondary sleds. Each secondary sled is linearly movable and is flexibly attached to a respective secondary support strut which is in turn flexibly attached to a respective one of the primary support struts at a point intermediate between its connection to its primary sled and to the load. Each secondary strut may be attached by a revolute joint to its sled and by another revolute joint to its primary strut. The secondary struts are rigid, and preferably attached at their opposite ends to the sleds and the primary struts. The sleds of each pair of an interattached primary and secondary strut may be movable linearly along parallel axes, and optionally collinearly. Two of the primary sleds may be attached to the side rails of the load so as to oppose each other for forcing the load to move in surge. The remaining primary strut may be attached centrally to the load, for example by a single rail running along the centreline of the side-rails by which the other wishbones are attached to the load, or by one of those other side-rails, or by a side-rail at a different angle to those other side-rails.
In the example shown in
Instead of a secondary sled and additional connector element connecting that sled to the respective support 4, 5, 6, 7, other mechanisms could be used to constrain the inclination of the support relative to the sled. For example a rotational drive could be implemented at the rotational joint between the support and its primary sled.
The present structure is arranged to provide a compact mechanism for driving the motion platform with principal motions in the X and Y axes. In comparison to the Stuart platform the present structure allows substantial forces in the X and Y directions to be imparted without requiring the platform to be far above the base. This makes it significantly more convenient for the occupant to enter the chassis. The platform rails and especially the base rails can straightforwardly be made relatively long, allowing relatively large displacements to be imparted in the horizontal plane. For many road vehicles the greatest potential forces are in the surge and sway directions, which correspond to cornering and straight-line acceleration and braking. Therefore, it is preferred that the chassis is mounted relative to the platform rails and the base rails so that the sway and surge axes are in a plane parallel to all those rails. The surge axis is preferably parallel to the forward axis of the chassis and the sway axis is preferably perpendicular to the forward axis and the upward axis of the chassis. The forward and upward axes of the chassis will typically be defined by reference to an occupant/operator position in the chassis. Where the occupant position has a seat the forward axis is typically the forward-facing direction of the seat. The highest potential for force may often be in the sway axis since higher forces may often be expected during cornering than in straight-linear acceleration and braking. Therefore, it is most preferred that the sway axis is parallel to the base rails. This implies that the forward orientation of the chassis is perpendicular to the base rails.
The platform 1 need not be trapezoidal: for instance the platform rails (e.g. 30) could be attached in their tapering configuration to the underside of a square plate. Alternatively, the platform could be omitted and platform rails could be attached directly to the chassis.
In
Each revolute joint could be a conventional rotating hinge joint, or a flexure joint, or of another form.
One or more of the intermediate links could have spherical joints at its connection to the respective sled and/or its connection to the respective primary link/wishbone.
The primary links/wishbones and the intermediate links could be rigid. Alternatively any of those links could be flexible and/or elastic, for example a spring cantilever.
The simulator could be configured for simulating a vehicle, such as a road vehicle.
Additional means for supporting the load could be provided, for example an elastic element such as a spring or a driven element such as a hydraulic piston. Such means could be provided under the load and extending between the load and a base, or above the load and extending between the load and an upper support structure such as a gantry or ceiling. Such means could be mounted to the load and/or the base or upper support in such a way that it can accommodate lateral motion of the load with respect to the base or support.
The arrangement described above could be used for other applications such as machine tools, vibration test equipment, pick-and-place machines, and tracking systems.
The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1505800.1 | Apr 2015 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2016/050939 | 4/1/2016 | WO | 00 |
