MOTION PLATFORM

Abstract

A motion platform (2) comprises a base portion (6) and an occupant carrier portion (4). The occupant carrier portion (4) is linearly moveable along, and rotationally moveable about, first, second, and third orthogonal axes. The base portion (6) comprises first, second, and third control pillars (16, 18, 20) each extend along the third axis with a predetermined height. The control pillars (16, 18, 20) are linearly moveable in a plane defined by the first and second axes and are mechanically constrained to move only in that plane. The occupant carrier portion (4) comprises first, second, and third guide portions (28, 30, 32) that are pivotally connected to the first, second, and third control pillars (16, 18, 20) respectively by a respective coupling member (22, 24, 26). Each of the guide portions (28 30, 32) is angled with respect to the plane defined by the first and second axes such that they are not parallel to the plane. The guide portions (28, 30, 32) are also angled with respect to each other such that they are not parallel with each other.

Claims

1. A motion platform comprising a base portion and an occupant carrier portion, said occupant carrier portion being linearly moveable along first, second, and third orthogonal axes, and rotationally moveable about said first, second, and third axes, wherein: the base portion comprises first, second, and third control pillars each extending substantially along the third axis, each of said control pillars being linearly moveable in a plane defined by the first and second axes, wherein the control pillars are mechanically constrained such that they move only in said plane; the occupant carrier portion comprises first, second, and third guide portions, said first, second, and third guide portions being pivotally connected to the first, second, and third control pillars respectively by a respective coupling member; the first, second, and third guide portions are each angled with respect to the plane defined by the first and second axes such that said guide portions are not parallel to said plane; the first, second, and third guide portions are angled with respect to each other such that each guide portion is not parallel with the other guide portions; said motion platform being arranged such that, in use, the first, second, and third control pillars each have a respective height of a predetermined value along the third axis.

2. The motion platform as claimed in claim 1, wherein the base portion comprises an X-Y table portion, wherein the X-Y table portion is arranged to provide independent in-plane movement of the first, second, and third control pillars along a respective first direction and a respective second direction, said first and second directions defining a plane normal to the third axis.

3. The motion platform as claimed in claim 2, wherein the first direction is along the first axis and/or the second direction is along the second axis.

4. The motion platform as claimed in claim 2 or 3, wherein the X-Y table portion comprises an X-Y table comprising a first slide rail and a second slide rail, said slide rails being slideably moveable relative to one another, wherein at least one control pillar is mounted on said X-Y table such that a sliding movement of the first slide rail moves the at least one control pillar along the first direction and such that a sliding movement of the second slide rail moves the at least one control pillar along the second direction.

5. The motion platform as claimed in any of claims 2 to 4, wherein the X-Y table portion comprises first, second, and third X-Y tables, each of said X-Y tables comprising respective first and second slide rails, said slide rails being slideably moveable relative to one another, wherein the first, second, and third control pillars are mounted on the first, second, and third X-Y tables respectively such that a sliding movement of the first slide rail moves the corresponding control pillar along the first direction and such that a sliding movement of the second slide rail moves the corresponding control pillar along the second direction. Thus, in accordance with such embodiments, each control pillar may be mounted on a separate X-Y table, where each X-Y table moves a control pillar in-plane.

6. The motion platform as claimed in claim 5, wherein each X-Y table respectively comprises a first carriage and a second carriage, said first and second carriages being arranged in a stack, wherein: the first carriage comprises the respective control pillar and one or more bearings that move along the first direction with respect to the second carriage, and a motor arranged to drive said motion of the first carriage along the first direction; the second carriage comprises one or more bearings that move along the second direction with respect to a base of the X-Y table, and a motor arranged to drive motion of the second carriage along the second direction; the second carriage further comprises one or more bearing rails aligned along the first direction, wherein the bearings of the first carriage engage with the one or more bearing rails of the second carriage; and the base of the X-Y table comprises one or more further bearing rails aligned along the second direction, wherein the bearings of the second carriage engage with the one or more bearing rails of the base.

7. The motion platform as claimed in claim 5 or 6, wherein the X-Y tables comprise one or more ironless linear motors, optionally wherein one or more of the X-Y tables employ a linear shaft motor comprising a plurality of magnets arranged in a cylindrical shaft, and a forcer comprising an electromagnet coil that surrounds the circumference of said shaft along a portion of the length of the shaft.

8. The motion platform as claimed in claim 1, wherein the base portion comprises a substantially circular support rail, said support rail defining a plane normal to the third axis, wherein the first, second, and third control pillars are connected to a plurality of radially moveable actuators, each connection between the control pillars and the respective radially moveable actuators being provided by a respective tension member, wherein the radially moveable actuators are arranged to move around the circumference of the circular support rail.

9. The motion platform as claimed in claim 8, wherein the tension members each comprise a cable, wherein each of the radially moveable actuators comprise a cable motor arranged to vary an effective length of the cable.

10. The motion platform as claimed in claim 8 or 9, wherein each of the radially moveable actuators comprise a respective radial linear motor arranged to move said radially moveable actuator around the substantially circular support rail.

11. The motion platform as claimed in any of claims 8 to 10, wherein the control pillars are supported above a flatbed on an air bed or on low friction bearings.

12. The motion platform as claimed in any of claims 8 to 11, wherein the base portion is arranged such that: the first control pillar is connected to first and second radially moveable actuators; the second control pillar is connected to third and fourth radially moveable actuators; and the third control pillar is connected to fifth and sixth radially moveable actuators.

13. The motion platform as claimed in claim 12, wherein the base portion is arranged such that: the first radially moveable actuator is radially adjacent the second radially moveable actuator; the third radially moveable actuator is radially adjacent the fourth radially moveable actuator; and the fifth radially moveable actuator is radially adjacent the sixth radially moveable actuator.

14. The motion platform as claimed in claim 12 or 13, wherein the base portion is further arranged such that: the first control pillar is connected to a seventh radially moveable actuator; the second control pillar is connected to an eighth radially moveable actuator; and the third control pillar is connected to a ninth radially moveable actuator.

15. The motion platform as claimed in claim 14, wherein the base portion is arranged such that: the seventh radially moveable actuator is radially adjacent the third and sixth radially moveable actuators; the eighth radially moveable actuator is radially adjacent the second and fifth radially moveable actuators; and the ninth radially moveable actuator is radially adjacent the first and fourth radially moveable actuators.

16. The motion platform as claimed in claim 14 or 15, wherein the tension members each comprise a cable, wherein each of the radially moveable actuators comprise a cable motor arranged to vary an effective length of the cable.

17. The motion platform as claimed in any of claims 12 to 15, wherein the tension members each comprise a piston, wherein each of the radially moveable actuators comprise a piston driver arranged to vary an effective length of the piston.

18. The motion platform as claimed in any preceding claim, wherein the control pillars are cylindrical, pyramidal or conic.

19. The motion platform as claimed in any preceding claim, wherein the respective heights of the first, second, and third control pillars are substantially the same.

20. The motion platform as claimed in any preceding claim, wherein a plane of the base portion is parallel to the plane in which the first, second, and third control pillars move, wherein the plane of the base portion is preferably coplanar with the plane in which the first, second, and third control pillars move.

21. The motion platform as claimed in any preceding claim, wherein the guide portions are arranged such that: the first guide portion is located at a central front portion of the occupant carrier portion; the second guide portion is located at a rear-left portion of the occupant carrier portion; and the third guide portion is located at a rear-right portion of the occupant carrier portion.

22. The motion platform as claimed in any preceding claim, wherein the base portion comprises one or more further control pillars each extending substantially along the third axis, each of said further control pillars being linearly moveable in the plane defined by the first and second axes, wherein the further control pillars are mechanically constrained such that they move only in said plane.

23. The motion platform as claimed in any preceding claim, wherein the guide portions each comprise a guide rail, wherein the guide rail defines a track along which motion of the respective coupling member is constrained.

24. The motion platform as claimed in any preceding claim, wherein one or more of the guide portions comprises a gas strut, optionally wherein all of the guide portions comprise a respective gas strut.

25. The motion platform as claimed in claim 24, wherein the gas strut(s) comprise a rod end and a cylinder end, wherein the coupling member connects the control pillar to the rod end of the respective gas strut.

26. The motion platform as claimed in any preceding claim, wherein an angle between at least one guide portion and the plane defined by the first and second axes is between 10 degrees and 70 degrees, preferably between 20 degrees and 60 degrees, more preferably between 25 degrees and 55 degrees.

27. The motion platform as claimed in claim 26, wherein an angle between at least one guide portion and the plane defined by the first and second axes is approximately 26.5 degrees.

28. The motion platform as claimed in claim 26 or 27, wherein an angle between at least one guide portion and the plane defined by the first and second axes is approximately 45 degrees.

29. The motion platform as claimed in any preceding claim, wherein an angle between the first, second, and third guide portions is between 70 degrees and 150 degrees, preferably between 80 degrees and 140 degrees, more preferably between 90 degrees and 135 degrees.

30. The motion platform as claimed in claim 29, wherein an angle between the first guide portion and each of the second and third guide portions is approximately 135 degrees.

31. The motion platform as claimed in claim 29 or 30, wherein an angle between the second and third guide portions is approximately 90 degrees.

32. The motion platform as claimed in claim 29 or 30, wherein an angle between the second and third guide portions is approximately 100 degrees.

33. The motion platform as claimed in any preceding claim, wherein one or more of the coupling members comprise a spherical ball joint.

34. The motion platform as claimed in any preceding claim, wherein one or more of the coupling members comprises a gimbal, optionally wherein the gimbal comprises a steel gimbal.

35. The motion platform as claimed in claim 34, wherein the gimbal is arranged at approximately 90 degrees to the respective guide portion.

36. The motion platform as claimed in any preceding claim, wherein the occupant carrier portion has a monocoque structure.

37. The motion platform as claimed in claim 1, wherein the base portion comprises: a primary stage comprising an X-Y table portion, wherein the X-Y table portion is arranged to provide independent in-plane movement of the first, second, and third control pillars along a respective first direction and a respective second direction, said first and second directions defining a plane normal to the third axis; and a secondary stage comprising a substantially circular support rail, said support rail defining a plane normal to the third axis; wherein the X-Y table portion is mounted to the support rail via a radially moveable bearing members arranged to move around the circumference of the circular support rail; wherein the secondary stage further comprises a radial motor arranged to drive rotational motion of the primary stage relative to the secondary stage.

38. The motion platform as claimed in claim 37, wherein the secondary stage comprises a plurality of concentric substantially circular support rails, each support rail being coplanar and defining a respective plane normal to the third axis.

39. The motion platform as claimed in claim 38, wherein each of the concentric support rails has one or more radially moveable bearing members arranged to move around its respective circumference.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0096] Certain embodiments of the present invention will now be described with reference to the accompanying drawings, in which:

[0097] FIG. 1 is an isometric view of a motion platform in accordance with an embodiment of the present invention;

[0098] FIG. 2 is an isometric view of the occupant carrier portion of the motion platform of FIG. 1;

[0099] FIG. 3 is a plan view schematic that shows the central position of the motion platform of FIG. 1;

[0100] FIGS. 4a-f are plan view schematics that show the six degrees of freedom provided by the motion platform of FIG. 1;

[0101] FIG. 5 is an isometric view of a guide portion employing a gas strut in accordance with an embodiment of the present invention;

[0102] FIG. 6 is a plan view of a motion platform on an X-Y table base portion in accordance with an embodiment of the present invention;

[0103] FIG. 7 is an isometric view of a section of the X-Y table base portion of FIG. 6;

[0104] FIG. 8 is an isometric view of the X-Y table base portion of FIG. 6;

[0105] FIG. 9 is a plan view of a motion platform on an unlimited yaw base portion in accordance with an embodiment of the present invention;

[0106] FIG. 10 is an isometric view of the unlimited yaw base portion of FIG. 9;

[0107] FIG. 11 is a plan view of a motion platform on a further unlimited yaw base portion in accordance with an embodiment of the present invention;

[0108] FIG. 12 is an isometric view of the unlimited yaw base portion of FIG. 11;

[0109] FIG. 13 is an isometric view of a motion platform in accordance with a further embodiment of the present invention;

[0110] FIG. 14 is a plane view of the motion platform of FIG. 13;

[0111] FIG. 15 is a further isometric view of the motion platform of FIG. 13 showing an integral chassis;

[0112] FIG. 16 is an isometric view of a guide portion employing a gimbal;

[0113] FIG. 17 is an isometric view of a stacked X-Y table base portion;

[0114] FIG. 18 is an isometric view of a motion platform with a yaw table stage in accordance with an embodiment of the present invention;

[0115] FIGS. 19A and 19B are further isometric views of the motion platform of FIG. 18; and

[0116] FIG. 20 is a plan view of the yaw table used in the motion platform of FIG. 18.

DETAILED DESCRIPTION

[0117] FIG. 1 is an isometric view of a motion platform 2 in accordance with an embodiment of the present invention. The motion platform 2 comprises an occupant carrier portion 4 and a base portion 6. In the example shown in FIG. 1, the base portion 6 includes an X-Y table, however a circular ‘unlimited yaw’ base could be used instead, as outlined below with reference to FIGS. 9 and 10.

[0118] The six degrees of freedom of the motion platform 2 correspond to linear movements in the surge, sway, and heave directions (i.e. along the x-, y-, and z-axes respectively), and rotational motions in the roll, pitch, and yaw directions (i.e. about the x-, y-, and z-axes respectively).

[0119] The occupant carrier portion 4 comprises a seat 8, steering column 10, and pedals 12 mounted within a frame 14. It will be appreciated that, in practice, there may be more or fewer components, and the layout of the occupant carrier portion 4 may vary depending on the application (e.g. if it is to be used as a flight simulator instead of an automotive simulator). The occupant carrier portion 4 of the motion platform 2 can be seen in more detail in FIG. 2, which provides an isometric view of the occupant carrier portion 4.

[0120] The base portion 6 comprises three control pillars 16, 18, 20, where two of these control pillars 16, 18—the front control pillar 16 and the rear-left control pillar 18—are shown in FIG. 1 while the rear-right control pillar 20 is obscured from view by the occupant carrier portion 4. The layout of all three control pillars 16, 18, 20 may be readily understood from FIGS. 3, 4a-f, and 8.

[0121] In this example, each control pillar 16, 18, 20 is constructed as a cylindrical ‘post’. Importantly, each pillar 16, 18, 20 is of a fixed height such that the distance from the top to the bottom of the pillar 16, 18, 20 (i.e. in the z-direction) cannot change. A spherical ball joint 22, 24, 26 is provided at the top of each control pillar 16, 18, 20.

[0122] In this particular example, the spherical ball joints 22, 24, 26 are connected to a respective threaded bolt 23, 25, 27 (i.e. a threaded member), which can be loosened or tightened so as to change the predetermined height of the corresponding control pillar 16, 18, 20. Any adjustment in the predetermined heights of the control pillars 16, 18, 20 is carried out while the motion platform 2 is not in operation, as the respective heights of the control pillars 16, 18, 20 remain constant while the motion platform 2 is in use.

[0123] The occupant carrier portion 4 comprises three guide rails 28, 30, 32, where two of these rails 28, 30—the front rail 28 and the rear-left rail 30—are shown in FIGS. 1 and 2 while the rear-right guide rail 32 is obscured from view by the rest of the occupant carrier portion 4. The layout of all three guide rails 28, 30, 32 may be readily understood from FIG. 6.

[0124] The angle θ between the front guide rail 28 and the x-y plane defined by the x- and y-axes is approximately 26.5 degrees. The angle φ between the rear guide rails 30, 32 and the x-y plane is approximately 45 degrees. An angle φ of 45 degrees advantageously decreases the in-plane force required from each actuator to lift the occupant carrier portion 4, i.e. out-of-plane heave motions in the z-axis direction.

[0125] As may be more readily seen with reference to the plan view of the motion platform 2 shown in FIG. 6, the guide rails 28, 30, 32 are also angled with respect to each other. The angle a between the front guide rail 28 and each of the rear guide rails 30, 32 is approximately 135 degrees while the angle β between the rear guide rails 30, 32 is approximately 90 degrees.

[0126] By way of non-limiting example, by angling the rear rails (in plan view) at 90 degrees to each other such that when the platform is in the centre (i.e. null) position, the angle is at 45 degrees to both the x and y axis, the force required to move the rear left or right corners is shared equally by the x and y actuators. However, when in the centre position, the guide is parallel to the y axis, meaning that lifting the front of the occupant carrier portion up and down may require the y actuator to provide all of the required force. If, by design, the centre of gravity is over the rear pillars, the force required to lift the front is significantly less than the rear so this is generally not an issue. As a consequence, an actuator in the x axis does not have to provide any force in order to move the front of the occupant carrier up and down, meaning there may be maximum force available for yaw movements, which is highly desirable in some applications.

[0127] The spherical ball joints 22, 24, 26 provided at the top of each control pillar 16, 18, 20 are pivotally connected to the guide rails 28, 30, 32. Specifically, the ball joint 22 at the top of the front control pillar 16 is connected to the front guide rail 28; the ball joint 24 at the top of the rear-left control pillar 18 is connected to the rear-left guide rail 30; and the ball joint 26 at the top of the rear-right control pillar 20 is connected to the rear-right guide rail 32. These spherical ball joints 22, 24, 26 are thus coupling members that may slide along the respective guide rail 28, 30, 32 and allow the occupant carrier portion 4 to tilt.

[0128] As the control pillars 16, 18, 20 are each of a fixed height, the occupant carrier portion 4 is unable to move in any axis without moving a control pillar 16, 18, 20 and is mechanically constrained by the control pillars 16, 18, 20. This motion platform 2 could also use a circular ‘unlimited yaw’ platform as described with reference to FIGS. 11 and 12 below (or another suitable arrangement), but in any such arrangement, the underlying design principle is that it is possible to convert movements of the control pillars 16, 18, 20 in the x- and y-directions (i.e. in the x-y plane) into an out-of-plane motion in the z-direction by means of positioning the control pillars 16, 18, 20 in a known position so as to force the platform 2 to move into the desired attitude. Such movements are outlined in further detail with reference to FIGS. 3 and 4a-f.

[0129] FIG. 3 is a plan view schematic that shows the central position of the motion platform 2 of FIG. 1. The control pillars 16, 18, 20 may each move, independently, in the x- and y-directions, i.e. they may move within the x-y plane. For ease of understanding, the schematic drawings of FIGS. 3 and 4a-f simplify the construction of the motion platform 2 for illustrative purposes only.

[0130] In this central or ‘null’ position, the motion platform 6 has not undergone any surge, sway, heave, roll, pitch, or yaw motions, i.e. it is the ‘default’ position of the motion platform 2.

[0131] FIGS. 4a-f are plan view schematics that show the six degrees of freedom provided by the motion platform 2 of FIG. 1. Specifically, these schematics illustrate the movements of the control pillars 16, 18, 20 that are carried out to achieve surge, sway, heave, pitch, roll, and yaw motions. It will, of course, be appreciated that the specific set of motions shown are a limited set shown for illustrative purposes in order to depict the respective positions of the control pillars 16, 18, 20 for the maximum of each motion in one direction. In practice, the control pillars 16, 18, 20 to move the occupant carrier portion 4 will shift between these positions as appropriate for the desired cues.

[0132] FIG. 4a shows the position of the control pillars 16, 18, 20 that achieves maximum positive surge movement, i.e. in the x-axis. In order to achieve this, all three control pillars 16, 18, 20 are moved in the positive x-axis direction, while the y-axis position of the control pillars 16, 18, 20 is not changed. Moving all three control pillars 16, 18, 20 in the negative x-axis direction would instead result in a negative surge movement.

[0133] FIG. 4b shows the position of the control pillars 16, 18, 20 that achieves maximum positive sway movement, i.e. in the y-axis. In order to achieve this, all three control pillars 16, 18, 20 are moved in the positive y-axis direction, while the x-axis position of the control pillars 16, 18, 20 is not changed. Moving all three control pillars 16, 18, 20 in the negative y-axis direction would instead result in a negative sway movement.

[0134] FIG. 4c shows the position of the control pillars 16, 18, 20 that achieves maximum positive heave movement, i.e. in the z-axis. In order to achieve this, all three control pillars 16, 18, 20 are moved toward the centre of the base portion 4, by moving in the x- and y-axis directions as appropriate. In this example, the guide rails 28, 30, 32 are all angled ‘upwards’ such that moving the three control pillars 16, 18, 20 toward the centre means that the mass of the occupant carrier portion 4 is pushed upwards (i.e. as the pivotal connection of the control pillars 16, 18, 20 shifts toward the lowest point of the guide rails in the z-axis direction).

[0135] Moving all three control pillars 16, 18, 20 away from the centre of the base portion 4 would lead to a negative heave motion, i.e. the opposite direction in the z-axis.

[0136] If the guide rails 28, 30, 32 were all angled ‘downwards’ instead, moving the control pillars 16, 18, 20 in this way would instead result in a negative heave motion. The angling of the guide rails 28, 30, 32 could also be ‘non-matching’ instead such that some of the guide rails 28, 30, 32 are angles upwards and some downwards, with appropriate changes to which control pillars 16, 18, 20 move inwards or outwards.

[0137] FIG. 4d shows the position of the control pillars 16, 18, 20 that achieves maximum positive pitch movement, i.e. about the y-axis. In order to achieve this, the front control pillar 16 is moved toward the centre of the base portion 6 while the rear control pillars 18, 20 are moved away from the centre of the base portion 6. Due to the angling of the guide rails 28, 30, 32, this causes the occupant carrier portion 4 to rotate about the y-axis such that the ‘nose’ of the occupant carrier portion 4 tilts upwards.

[0138] Moving the front control pillar 16 away from the centre of the base portion 6 while moving the rear control pillars 18, 20 toward the centre of the base portion 6 would result in a negative pitch movement instead.

[0139] FIG. 4e shows the position of the control pillars 16, 18, 20 that achieves maximum positive roll movement, i.e. about the x-axis. In order to achieve this, the front control pillar 16 is left in the null position while the rear-left control pillar 18 is moved away from the centre of the base portion 6 and the rear-right control pillar 20 moves toward the centre of the base portion 6. This causes the occupant carrier portion 4 to rotate about the x-axis such that the occupant carrier portion 4 ‘banks’ to one side. If the movements of the rear control pillars 18, 20 were reversed (i.e. the rear-left control pillar 18 toward and the rear-right control pillar 20 away from the centre), the occupant carrier portion 4 would rotate about the x-axis in the other direction such that the occupant carrier portion 4 would bank to the other side.

[0140] FIG. 4f shows the position of the control pillars 16, 18, 20 that achieves maximum positive yaw movement, i.e. about the z-axis. In order to achieve this, all three control pillars 16, 18, 20 are moved toward the position of the next control pillar 16, 18, 20 clockwise. This causes the occupant carrier portion 4 to rotate about the z-axis such that the occupant carrier portion 4 ‘pivots’ in place. Moving the three control pillars 16, 18, 20 anticlockwise instead would, of course, result in a negative yaw movement, i.e. about the z-axis in the other direction.

[0141] FIG. 5 is an isometric view of a guide portion employing a gas strut in accordance with an embodiment of the present invention. As can be seen in FIG. 5, the guide rails 28, 30, 32 described above may be provided with a gas strut (i.e. a gas spring) 34. The gas strut 34 is constructed from a cylinder end 36 and a rod end 38, where the cylinder end 36 is filled with a gaseous medium that is sealed in by the rod end 38. This gaseous medium is increasingly compressed and the rod end 38 moves into the cylinder end 36.

[0142] The spherical ball joint 22, 24, 26 at the top of the appropriate control pillar 16, 18, 20 may be connected to one end, e.g. the rod end 38, of the gas strut 34. The gas strut 34 provides damping and helps to support the mass of the occupant carrier portion 4. However, the use of gas strut(s) is not essential, and the spherical ball joints 22, 24, 26 may be connected so as to slide along the guide rails 28, 30, 32 instead.

[0143] FIG. 6 is a plan view of a motion platform on an X-Y table base portion 6 in accordance with an embodiment of the present invention. The X-Y table base portion 6 is seen closer up in FIG. 7 which is an isometric view of a section of the X-Y table base portion of FIG. 6, specifically one of the three X-Y tables 7a-c. FIG. 8 provides an isometric view of the entire X-Y table base portion 6 of FIG. 6.

[0144] The X-Y table base portion 6 is constructed from three X-Y tables 7a-c, one for each control pillar 16, 18, 20.

[0145] Each of said X-Y tables 7a-c comprises first and second slide rails 38a-c, 40a-c that are slideably moveable relative to one another, i.e. they can slide adjacent to each other under control of e.g. a linear motor. There are a number of X-Y table arrangements known in the art per se, however in this example the X-Y table base portion 6 uses six ball screw actuators, i.e. two per X-Y table 7a-c.

[0146] Each slide rail 38a-c, 40a-c provides for movement along one of two orthogonal directions, either the x-axis direction or the y-axis direction (with one slide rail 38a-c, 40a-c per direction). In this example, the first slide rail 38a-c provides motion in the x-axis direction and the second slide rail 40a-c provides motion in the y-axis direction. Thus a sliding movement of the first slide rail 38a-c moves the corresponding control pillar 16, 18, 20 along the x-axis (i.e. surge) direction and the second slide rail 40a-c moves the corresponding control pillar 16, 18, 20 along the y-axis (i.e. sway) direction. Thus each X-Y table 7a-c moves a control pillar 16, 18, 20 in the x-y plane.

[0147] FIG. 9 is a plan view of a motion platform 102 on an unlimited yaw base portion 106 in accordance with an embodiment of the present invention. FIG. 10 is an isometric view of the motion platform 102 of FIG. 9. The motion platform 102 comprises an occupant carrier portion 104 and base portion 106, where the occupant carrier portion is provided with at least three guide rails (not shown in FIGS. 9 and 10) that are angled both with respect to the x-y plane and to each other as described previously with regard to the motion platform 2 of FIG. 1.

[0148] The base portion 106 comprises first, second, and third control pillars 110, 112, 114 that are connected to a plurality of radially moveable actuators 116a-f. The connection between the control pillars 110, 112, 114 and the angled guide rails on the occupant carrier portion 104 is provided by a pivotal connection as described previously. The control pillars 110, 112, 114 of the base portion 106 shown in FIGS. 9 and 10 are conic, rather than cylindrical, but still have a fixed height. It will be appreciated that these control pillars 110, 112, 114 could be cylindrical instead (and similarly, the control pillars 16, 18, 20 described above could be conic; and any of the control pillars 16, 18, 20, 110, 112, 114 described herein could take any suitable shape).

[0149] Each control pillar 110, 112, 114 is connected to two of the actuators 116a-f such that the first (i.e. front) control pillar 110 is connected to first 116a and second 116b, radially moveable actuators; the second (i.e. rear-left) control pillar 112 is connected to third 116c and fourth 116d radially moveable actuators; and the third (i.e. rear-right) control pillar 114 is connected to fifth 116e and sixth 116f radially moveable actuators.

[0150] Each connection between the control pillars 110, 112, 114 and the respective radially moveable actuators 116a-f is provided by a respective piston 118a-f (i.e. a tension member). The radially moveable actuators 116a-f are arranged to move around the circumference of the circular support rail 108, which provides a track for the movement of the actuators 116a-f.

[0151] The radially moveable actuators 116a-f each comprise a piston driver 120a-f arranged to vary an effective length of the corresponding piston 118a-f. The piston driver 120a-f may extend or retract the piston 118a-f to lengthen or shorten the piston 118a-f. The actuators 116a-f also each comprise a respective radial linear motor 122a-f that provides for movement of the radially moveable actuator 116a-f around the circular support rail 108, where motion of the control pillars 110, 112, 114 is mechanically constrained to in-plane movements only (i.e. within the x-y plane).

[0152] The configuration of the motion platform 102 with the circular support rail 108 advantageously provides for unlimited yaw (i.e. in-plane rotation in the x-y plane), where the centre of rotation may be varied as required. Unlimited yaw with a variable highly desirable in a vehicle simulator as doing because this makes it possible to match the yaw and change in slip of a real car in a 1:1 ratio which is crucial for cueing the feeling of oversteer and understeer to the occupant's vestibular.

[0153] By moving the radially moveable actuators 116a-f around the circumference of the circular support rail 108 and by lengthening and shortening the pistons 118a-f as appropriate, the motion platform 102 provides surge, sway, heave, pitch, roll, and yaw movements by moving the control pillars 110, 112, 114 only in the x-y plane using a ‘scissor-like’ movement of the actuators 116a-f. The configurations of the control pillars 110, 112, 114 that provide each of these motions is substantially the same as those described in FIGS. 4a-f (assuming that the guide rails of the occupant carrier portion 104 in the motion platform 102 match those of the occupant carrier portion 4 in the motion platform 2 of FIG. 1), however there is no longer a ‘central’ position with respect to the in-plane (i.e. in the x-y plane) rotation of the occupant carrier portion 104.

[0154] FIG. 11 is a plan view of a motion platform 202 on an unlimited yaw base portion 206 in accordance with a further embodiment of the present invention. FIG. 12 is an isometric view of the motion platform 202 of FIG. 11. The motion platform 202 comprises an occupant carrier portion 204 and base portion 206, where the occupant carrier portion is provided with at least three guide rails (not shown in FIGS. 11 and 12) that are angled both with respect to the x-y plane and to each other as described previously with regard to the motion platform 2 of FIG. 1.

[0155] In the motion platform 202 of FIG. 11, the base portion 206 comprises a substantially circular support rail 208. This circular support rail 208 provides a track around which a number of radially moveable actuators can move in the x-y plane, i.e. the plane of the support rail 208 is normal to the z-axis.

[0156] The base portion 206 comprises first, second, and third control pillars 210, 212, 214 that are connected to a plurality of radially moveable actuators 216a-i. The connection between the control pillars 210, 212, 214 and the angled guide rails on the occupant carrier portion 204 is provided by a pivotal connection as described previously. The control pillars 210, 212, 214 of the base portion 206 shown in FIGS. 11 and 12 are conic, rather than cylindrical, but still have a fixed height. It will be appreciated that these control pillars 210, 212, 214 could be cylindrical instead (and as outlined above, the control pillars 210, 212, 214 described could take any suitable shape).

[0157] Each control pillar 210, 212, 214 is connected to three of the actuators 216a-i such that the first (i.e. front) control pillar 210 is connected to first 216a, second 216b, and seventh 216g radially moveable actuators; the second (i.e. rear-left) control pillar 212 is connected to third 216c, fourth 216f, and eighth 216h radially moveable actuators; and the third (i.e. rear-right) control pillar 214 is connected to fifth 216e, sixth 216f, and ninth 216i radially moveable actuators.

[0158] Each connection between the control pillars 210, 212, 214 and the respective radially moveable actuators 216a-i is provided by a respective cable 218a-i (i.e. a tension member). The radially moveable actuators 216a-i are arranged to move around the circumference of the circular support rail 208, which provides a track for the movement of the actuators 216a-i.

[0159] The radially moveable actuators 216a-i each comprise a cable motor 120a-i arranged to vary an effective length of the corresponding cable 218a-i. The cable motor 120a-i may ‘wind in’ the cable 218a-i to shorten the effective length and/or allow the cable 218a-i to unwind or unravel. The actuators 216a-i also each comprise a respective radial linear motor 122a-i that provides for movement of the radially moveable actuator 216a-i around the circular support rail 208, where motion of the control pillars 210, 212, 214 is mechanically constrained to in-plane movements only (i.e. within the x-y plane).

[0160] The configuration of the motion platform 202 with the circular support rail 208 advantageously provides for unlimited yaw (i.e. in-plane rotation in the x-y plane), where the centre of rotation may be varied as required. Unlimited yaw with a variable highly desirable in a vehicle simulator as doing because this makes it possible to match the yaw and change in slip of a real car in a 1:1 ratio which is crucial for cueing the feeling of oversteer and understeer to the occupant's vestibular.

[0161] By moving the radially moveable actuators 216a-i around the circumference of the circular support rail 208 and by lengthening and shortening the cables 218a-i as appropriate, the motion platform 202 provides surge, sway, heave, pitch, roll, and yaw movements by moving the control pillars 210, 212, 214 only in the x-y plane. The configurations of the control pillars 210, 212, 214 that provide each of these motions is substantially the same as those described in FIGS. 4a-f (assuming that the guide rails of the occupant carrier portion 204 in the motion platform 202 match those of the occupant carrier portion 4 in the motion platform 2 of FIG. 1), however there is no longer a ‘central’ position with respect to the in-plane (i.e. in the x-y plane) rotation of the occupant carrier portion 204.

[0162] FIG. 13 is an isometric view of a motion platform 302 in accordance with a further embodiment of the present invention. Further views of the motion platform 302 can be seen in FIGS. 14 and 15. Specifically, FIG. 14 is a plane view of the motion platform 302, and FIG. 15 provides a further isometric view of the motion platform 302 showing the integral chassis used in the occupant carrier portion 304 (where this is simplified in FIGS. 13 and 14 for ease of illustration).

[0163] In this embodiment, the occupant carrier portion 304 is mounted to three X-Y tables 306a-c via respective pillars 316, 318, 320. However, in this embodiment, the pillars 316, 318, 320 are of a pyramid-shaped construction.

[0164] Each of the pillars 316, 318, 320 is connected to a respective guide portion 328, 330, 332 on the underside of the occupant carrier portion 304 via a gimbal 334, as can be seen more clearly in the close-up view of FIG. 16. The gimbal 334 is connected to a pair of bearing rails 336 on the guide portion 328, 330, 332 via bearings 338 positioned on the gimbal 334. These allow the gimbal 334 to slide along the bearing rails 336.

[0165] A further difference from the earlier-described embodiments is that, in the motion platform 302 of FIG. 13, the X-Y tables 306a-c are each constructed from stacked carriages, where the carriages 308a-c for motion in the y-direction are positioned at the bottom and the carriages 310a-c for motion in the x-direction are mounted on top of the y-carriages 308a-c. The carriages 308a-c, 310a-c are constructed from a composite material. Of course, other arrangements in which the x-carriage is at the bottom with the y-carriage on top could be used instead.

[0166] FIG. 17 provides a close-up view of a portion of the X-Y table, in which a closer view of the construction of the x-carriages 310a-c and y-carriages 308a-c can be seen.

[0167] The y-carriages 308a-c each include a respective linear motor 312. These ‘U-channel’ linear motors 312 of the y-carriages 308a-c run along a respective magnet way 313. Each y-carriages 308a-c has a number of bearings 350 on its underside that allows the y-carriage 308a-c to slide along bearing rails 352 on the base 315 under the respective y-carriage 308a-c.

[0168] The x-carriages 310a-c include the respective pillar 316, 318, 320. As the x-carriages 310a-c are mounted on top of the corresponding y-carriages 308a-c, motion of any given y-carriage 308a-c along the y-axis also causes the respective x-carriage 310a-c, and therefore the control pillar 316, 318, 320 thereof, to move along the y-axis.

[0169] The x-carriages 310a-c also include a number of bearings 344 that slide along a bearing rail 346 on the y-carriage 308a-c beneath. This allows the x-carriage 310a-c—and thus the pillars 316, 318, 320—to move along the x-axis, on top of the corresponding y-carriage 308a-c. The x-carriages 310a-c also include respective linear motors 314 that provide this motion along the x-axis.

[0170] The particular construction of the linear motors 314 used in the x-carriages 310a-c is discussed in detail below, however it will be appreciated that similar operational principles apply in respect of the U-channel linear motor of the y-carriages 308a-c.

[0171] Each of the linear motors 314 in the x-carriages 310a-c utilises a cylindrical stack of disk-shaped magnets surrounded by an electromagnet coil. These magnets form a shaft 340 that contains the disk-shaped magnets referred to above. Generally, the disk-shaped magnets are arranged such that like poles are next to one another, i.e. the orientation of the disk-shaped magnets alternates along the stack: N-S; S-N; N-S; etc. This shaft 340 is arranged to move through a forcer 342.

[0172] Thus the forcer 342 includes the electromagnet coil, where passing a current through the coil induces a magnetic field that results in the forcer 342 being pushed in the desired direction along the shaft 340.

[0173] An electrical current through the coil is controlled to cause a varying magnetic field from the coil that, due to the permanent magnetic field from the disk-shaped magnet stack, causes actuation of the forcer 342.

[0174] The forcer 342 is connected to the underside of the respective pillar 316, 318, 320. The pillars 316, 318, 320 have a number of bearings 344 that engage with bearing rails 346 that run along the x-carriage 310a-c in the x-direction. This allows the pillar 316, 318, 320 to move back-and-forth along the x-direction as the forcer 342 moves along the shaft 340.

[0175] Due to the fixed connection between the forcer 342 and the surrounding x-carriage 310a-c (in particular to the pillar 316, 318, 320), motion of the forcer 342 causes motion of the x-carriage 310a-c (and thus the corresponding pillar 316, 318, 320) along the x-direction as appropriate. Furthermore, as the pillar 316, 318, 320 is connected to the underside of the occupant carrier portion 304 (via the respective guide portion), movement of the forcer 342 causes movement of the occupant carrier portion 304 along the x-axis.

[0176] At each end of the travel of the x-carriage 310a-c within the y-carriage 308a-c are resilient bumpers 348 (in this case, coil springs), which ‘cushion’ motion at the end of the travel of the x-carriage 310a-c.

[0177] On the underside of the y-carriage 308a-c are several further bearings 350 that engage with bearing rails 352 on the respective base 315 that run along the length that the y-carriage 308a-c can travel (i.e. in the y-direction). The linear motor 312 of the y-carriage 308a-c provides motion using a forcer containing an electromagnet coil that runs along the magnet way 313, in a manner conventional to U-channel linear motors, known in the art per se. The linear motor 312 of the y-carriage 308a-c causes the y-carriage 310a-c, and therefore the x-carriage 310a-c mounted on it to move along the y-axis. Due to the connection between the pillars 316, 318, 320 and the occupant carrier portion 304, this also causes the occupant carrier portion 304 to move along the y-axis.

[0178] Similar to the bumpers 348 discussed above, at each end of the travel of the y-carriage 308a-c along the base 315 are resilient bumpers 349 (in this case, coil springs), which ‘cushion’ motion at the end of the travel of the y-carriage 308a-c.

[0179] FIG. 18 is an isometric view of a motion platform 402 in which the occupant carrier portion 404 is mounted on a stacked base portion, in which an X-Y table stage 406 is positioned on top of a yaw table stage 408, in accordance with an embodiment of the present invention. FIGS. 19A and 19B are further isometric views of the motion platform of FIG. 18, showing cut-away views of the monocoque occupant carrier portion 404. FIG. 20 provides a plan view of the yaw table stage 408.

[0180] The ‘primary’ X-Y table stage 406 of the motion platform 402 is of the same construction, and works in the same way, as the arrangement described above with reference to FIGS. 13 to 17. However, rather than relying solely on the X-Y table stage 406 to provide yaw motion (i.e. rotation around the z-axis), the X-Y table stage 406 is mounted on the ‘secondary’ yaw table stage 408, that can provide unlimited yaw.

[0181] The yaw table stage 408 compliments the X-Y table stage 406 to ensure that yaw travel remains both highly dynamic and unlimited. As long as the yaw table stage 408 can accelerate to the maximum velocity within the time taken at the X-Y table stage 406 stage to reach its limit of rotation, there should be no degradation in performance when these stages 406, 408 are mounted on top of each other.

[0182] As can be seen in the plan view of FIG. 20, the yaw table stage 408 includes three concentric circular support rails 410, which act as bearing rails. The primary X-Y table stage 406 (omitted from view in FIG. 20) includes a number of bearing blocks 412, which are arranged to move around the circumference of the concentric rails 410. Only a select number of the bearing blocks 412 are labelled on FIG. 20 for ease of illustration

[0183] These bearing blocks 412 are connected to the underside of a bed 414, which is positioned between the bearing blocks 412 and the X-Y table stage 406, such that the X-Y table stage 406 is mounted on the bed 414, and the bed 414 is mounted on the bearing blocks 412 of the yaw table stage 408. This structure could be made from steel or carbon or both.

[0184] The yaw table 408 includes a radial linear motor 416 that drives the rotational movement of the X-Y table stage 406 about the z-axis, i.e. to provide yaw motion, where the bearing blocks 412 slide over the rails 410 as the X-Y table stage 406 rotates. The forcer of the motor 416 is connected to the bed 414, while the stationary magnets of the motor 416 are connected to the base of the yaw table 408.

[0185] The number of bearing blocks 412 may be selected as a trade-off between stiffness and friction.

[0186] Thus it will be appreciated by those skilled in the art that embodiments of the present invention provide an improved motion platform having six degrees of freedom, where all motions are imparted through in-plane movement of the control pillars. The motion platform of the present invention may be readily scaled, e.g. in the surge direction, without requiring a substantial increase in the footprint of the motion platform. Furthermore, because out-of-plane motions are achieved only through in-plane movement of the control pillars, there is no need to stack layers of actuators, resulting in a lighter system that will typically exhibit an improved frequency response compared to conventional motion platforms.

[0187] While stacking layers of actuators is not required, this may still be beneficial while retaining the benefits of using fixed-height control pillars. By stacking the actuators as separate carriages, mounted one on top of another, the moving mass may be kept down when used with a large motion envelope.

[0188] While specific embodiments of the present invention have been described in detail, it will be appreciated by those skilled in the art that the embodiments described in detail are not limiting on the scope of the claimed invention.