Motion platform

Abstract

A motion platform 10 comprises control and processing means and a heave, pitch and roll, HPR, frame 31 assembly capable of translation in a third z axis, and capable of rotation around the first and s

Description

The present specification relates to motion platforms, that is a moveable platform particularly but not exclusively a platform that is moveable to simulate the motion of a vehicle such as but not limited to, a car, or aircraft. Motion platforms having six Degree of Freedom (6D0F) such as Hexapods and Stewart platforms; have been widely used in the commercial sector for flight simulation and training. They usually have, six actuators which are vertically mounted from the ground, and in order to get a good range of motion, they stand very high from the ground. They require large special rooms built for them. Recently these types of motion platforms have been downsized so that they can be used in the home sector, but these motion platforms due to their reduced size, have very limited ranges of motion, so are not credible for important vehicle dynamics. Alternative motion platforms such as GB2474279, GB 2378687 and GB2509053 have been proposed, which reproduce vehicle dynamics better, but they still have a high complexity and size, which makes them expensive and unsuitable to many markets such as for entertainment purposes. These Motion Platforms also require the control equipment to be external to the platform, either these control systems have to be placed in special rooms, or external boxes need to be created to house them, further increasing the size and complexity of the platform. The object of the present invention is to ameliorate one or more problems of the prior art motion platforms. An alternative object is to provide a useful motion platform. According to the present invention, there is provided a motion platform according to either claim 1 or claim 10. The terms first axis, second axis and third axis are used here synonymously with the x-axis, y-axis and z-axis respectively. The terms surge, sway and yaw are conventionally used to refer to translational movements in the x, y and z-axes respectively, and the terms pitch, roll and heave are conventionally used to refer to rotational movements again in the x, y and z-axes respectively, where the x-axis is the longitudinal axis of a vehicle. This convention will be adopted here, though it is to be realised that the choice of axes designated x y and z are to some extent arbitrary. The invention will now be described, by way of example, with reference to the drawings, of which Figure 1 is a perspective view of an embodiment of the motion platform; Figure 2 is a perspective view of the base frame assembly of the motion platform of figure 1; Figure 3 is a perspective view of the base frame and lateral frame of the motion platform of figure 1; Figure 4 is a perspective view of the base frame, lateral frame and HPR frame of the motion platform of figure 1; Figure 5 is a perspective view of a detail of the lateral frame and HPR frame of the motion platform of figure 1; Figures 6 and 7 are plan views of the base frame, lateral frame and HPR frame of the motion platform of figure 1 in two different orientations; Figure 8 is a plan view of the HPR frame of the motion platform of figure 1; Figure 9 is a plan view of the HPR frame of another embodiment of the motion platform; Figure 10 is a table showing characteristics of the motion platform of figure 8; and Figure 11 is a table showing characteristics of the motion platform of figure 9. Figure 12 is a perspective view of a further embodiment; Figure 13 is a perspective view of a further embodiment; Figure 14 is a perspective view of a further embodiment; Figure 15 is a perspective view of a further embodiment; and Figure 16 is a perspective view of a further embodiment. The same reference numerals are used throughout both different drawings of the same embodiment, and also different embodiments to indicate the same or corresponding parts or features, though some adaption of the same of corresponding parts may be necessary between embodiments. Referring to figure 1, the motion platform 10 comprises a payload 15 and a frame assembly 18, which comprises both the structural components which move the motion platform 10 and the actuators and control means. The translation and rotation of the of the frame assembly 18 is carried out by various subassemblies, each of which will be described in turn. Referring to figure 2, a base frame 11, which forms the lowest section of the frame assembly 18, has two parallel base rails 12, along whose upper surfaces surge base carriages 13 sit and which can run freely along the base rails 12 upon ways provided. Four surge base carriages 13, two on each base rails 12, are provided. The base frame 11 includes cross members or other types of strut to secure the rails in a fixed manner. A surge base plate 17 is also provided, which is secured to the actuator, the actuator secured to the base frame 11 and oriented parallel to both the base rails 12. A space or enclosure 14 may be provided between the base rails 12 for the processor and controller means. Referring to figure 3, a front lateral frame 21 is secured to the surge base plate 17 and two of the surge base carriages 13, and a rear lateral frame 22 is secured on the other two surge base carriage 13, each lateral frame 21, 22 spanning the base rails 12 and oriented perpendicular to the base rails 12, in the axis here designated as the y-axis. The lower part of the front lateral frame 21 is fitted both to the surge base carriages 13 and to the surge base plates 17 such that the front lateral frame 21 can be driven from below, whereas the lower part of the rear lateral frame 22 is attached only to the surge base carriage 13, which therefore acts as a compliant link, that is, the distance between the front lateral frame 21 and the rear lateral frame 22 can vary, which as will be described in greater detail below, allows rotation or yaw to occur in two points. The surge base plate 17 may be driven along the ways of the base rail 12 in either direction by an actuator, such as a hydraulic piston, though the skilled person will realise that many mechanisms may be employed for this purpose, such as a linear motor or a worm gear thread. The base frame 11, and in particular the movement of the front lateral frame 21 and surge base plate 17, and rear lateral frame 22, along the base rail 12, supported by the surge base carriages 13 provides the surge motion (or translation along the x-axis) of the system The front lateral frame 21 and rear lateral frame 22 are similar. Each lateral frame 21, 22 is oriented with its longitudinal axis perpendicular to the longitudinal axes of the base rails 12, and has a sway rail 19 with a way running along its length. The way of each lateral frame 21, 22 has a pair of carriages 23 which can run freely along the length of the lateral frame 21, 22, in the y-axis. A bearing plate 24 is secured to each pair of carriages 23 of each lateral frame 21, 22, and a cross roller bearing (though the skilled person will realise that rotation tracks or different bearings could be used here) 25 mounted on each bearing plate 24. The bearing plates 24 each have an actuator attached to drive it along the way of each lateral frame 21, 22 in either direction. A freely rotatable cross roller bearing 25 is mounted in each bearing plate 24. The HPR (heave, pitch and roll) assembly described in more detail below is secured to the bearing plates 24 and cross roller bearings 25. Since the rear lateral frame 22 is compliantly linked with the front lateral frame 21 by the HPR frame 31 (referred to in figure 4), the front lateral frames 21, 22 provide sway and yaw. Referring to figure 4, the HPR frame 31 has a longitudinal axis that runs between the cross roller bearings 25 of the bearing plates 24, bearing blocks 32 located at opposite ends of the HPR frame 31 being mounted on the cross roller bearings 25. Two wings 33, each comprising a pair of generally parallel beams, extend from either side of the main longitudinal body of the HPR frame 31, and each wings 33 being set at 120 degrees from the HPR frame centre line (i.e. a wing sweep angle of 30 degrees). The HPR frame 31 ideally extends below the height of the surfaces of the lateral components, in particular the upper surfaces of the cross roller bearing 25 and the bearing plate 24 but also may be coextensive or below the front lateral frame 21 and rear lateral frame 22. The HPR frame 31 includes three actuators 34, 35, which are fixed parallel to the longitudinal axis of the HPR frame 31, but each able to rotate. Two actuators 34 face to the rear of the HPR frame 31, and are fixed via centre mounts 42, the centre mounts 42 allowing the actuators to rotate about the z axis, while one actuator 35 faces in the opposite direction (i.e. generally to the front) and is fixed with a centre mount 43 so it can rotate about the y axis. The two actuators 34 are similar, and arranged symmetrically on either side of the centre line of the HPR frame 31; the connections and action of one actuator 34 will be described herein, and it will be understood that the other is similarly arranged with the same connecting components mirrored on the other side of the HPR frame 31. Referring to figure 5, one actuator 34 is fixed to an arm of a rotating horizontal crank 36 (i.e. the crank can pivot around the z axis in the x-y plane) that is fixed to a wing 33. The other arm of the horizontal crank 36 is connected to linking rod 37 to the lower arm of a rotating vertical bell crank 38 via two ball joints, the vertical bell crank 38 also being mounted on the wing 33. Movement of the actuator 34 along its axis causes the horizontal crank 36 to rotate in the x-y plane, and consequently the connecting linking rod 37 causes the vertical bell crank 38 to pivot so that the angle of altitude or elevation is changed and upper arm of the vertical bell crank 38 is raised or lowered (the plane in which the vertical bell crank 38 rotates will of course change as the HPR frame 31 is rotated amount the z axis). It will be realised that alternative equivalent articulated linkages can be provided to couple each rotating horizontal crank 36 to the associated vertical bell crank 38. As previously mentioned, the other actuator 34 is similarly arranged, with its own horizontal crank 36, linking rod 37 and vertical bell crank 38 attached to the other wing 33. The third actuator 35 which faces the front of the HPR frame 31 acts on a vertical bell crank 38', which as for the actuators 34, converts the horizontal translation of the actuator into a vertical displacement of the arm of the vertical bell crank 38 which is distal from the arm of the vertical bell crank 38 which is connected to the actuator 35 (see fig. 4). Since this vertical bell crank 38 is in line with the third actuator 35, a horizontal crank is not necessary, though a linking rod 37 may be used for the linkage between actuator 35 and the vertical bell crank 38' in a similar manner to the other actuators 34 and vertical bell cranks 38. The provision of three vertical bell cranks on the HPR frame 31 and wings 33 with each vertical bell crank separated by an angle of substantially 120 degrees to the adjacent vertical bell cranks means that all bell cranks can tilt the platform from the horizontal in any direction. The vertical bell cranks assemblies are each fitted with a pair of thrust bearings 39 and through those a rotating swing lift assembly 40 (which rotates in one axis only) is attached, with a ball joint 41 mounted on top. However, it will be realised that other articulated joints could be used to connect the vertical bell cranks to the payload. It will also be realised that the angles of the vertical bell cranks 38 could less ideally depart from a strict-equiangularity. That is, referring to Figure 8, considering the motion platform from above, if 0 is the angle subtended by the axis of the longitudinal axis I of the HPR frame 31 and the axis of one of the wings 33 axis m, 0 is ideally 120 degrees. However, a 0 of between 95° and 175°, or more ideally 110° and 130° could be used. The distance along the axis m to the wing's bell crank to the intersection with axis I does not have to be equal to the length along the axis I to the bell crank 38' from the intersection with axis m, however the distance along the axis m to the wing's bell crank to the intersection with axis should be equal for both wings. Provided the three vertical bell cranks 38, 38' are arranged non-colinearly though, heave, pitch and roll can be effectively provided by the HPR frame 31. Referring to figure 6, the HPR frame 31 is fitted via the bearing blocks 32 to the two cross roller bearing 25 that are on the front and rear lateral frames 21, 22, with the HPR frame 31 sitting above and generally between the front &rear lateral frames; this allows the actuators 34, 35 to sit below the top of the lateral frames, allowing for lower centre of gravity for the payload 15. The payload 15 is attached to the three ball joints 41, and then connected to the swing lift assembly 40 and is connected to a metal thrust bearings 39, the payload that has welded parts to coincide with the pattern of the HPR ball joint 41 positions. As an alternative to the metal frame shown in the figures, a GRP (glass reinforced plastic) cockpit or frame could also befitted. The addition of the payload 15 therefore constrains the vertical bell cranks 38, so no stabiliser / guide system is required to remove compliance. The actuators 34, 35 and the associated movement of the three vertical bell cranks 38 set generally equiangularly provides the ability to translate the payload 15 in the z axis (i.e. heave) and rotation of the payload about the x-axis (roll) and y-axis (pitch). The actuator of the surge base plate 17 provides the payload with translation in the x-axis (surge), while the actuators of bearing plates 24 provide the payload with translation in the y-axis (sway) and rotation in the z-axis (yaw). The provision of the six degrees of freedom can be summarised thus: Matrix of Motion Surge layer 1 (the base frame) Sway layer 2 (front and rear lateral frames Yaw layer 2 (front and rear lateral frames^ Heave Iayer3 (HPR frame) Roll Iayer3 (HPR frame) Pitch layers (HPRframe) 1st Motion 2nd &3rd Motion 2nd or 3rd Motion 4th &5th &6th Motion 4th or 5th Motion 4th &5th or 6th Motion This arrangement allows heave, roll and pitch to be provided by the HPR frame 31 with a relatively low total height of the system generally and the payload 15 in particular, as all or most of the vertical bell cranks 38 may be located between the ground and the upper surfaces of the front and rear lateral frames 21, 22. Referring to figures 6 and 7, the cross roller bearings 25 on the front and rear lateral frames 21, 22 provide the ability to rotate the HPR frame 31 and payload 15 between two pivot points (i.e. around a front pivot point shown by arrow a in figure 7, and a rear pivot point shown by arrow b in figure 6) rather than a single fixed pivot point of some previous known systems, which provides better simulation dynamics and avoids or reduces the requirement of compensation through translation. This in particular allows better simulation of Oversteer and Understeer dynamics which are particularly noticeable components of the real characteristics of a car. The vertical bell cranks 38 provide Heave, Pitch and Roll while being fully constrained and compliant, thus obviating the need for an additional guidance system for further compliance, providing comparable performance with known systems while allowing a reduction in size, mass and complexity. The use of the horizontal cranks 36 with the two vertical bell cranks 38 fixed to the wings 33 provides a particular space saving in the width and length of the motion platform 10. Referring to figure 9, less ideally, it would also be possible to have each vertical bell crank 38' on the two wings 33' driven directly from the actuators 34' (gearbox or worm drives etc), with these actuators being aligned with the vertical bell cranks 38'. However, this would require both actuators 34' to extend from the centre line of the HPR frame 31', as shown in figure 9, as compared to the preferred arrangement shown in figure 8, increasing the size of the frame, and also reduces the amount of motion, increasing the load characteristics of the frame, making it far harder to achieve the required stiffness. Representative dimensions and ranges of motion are given for the comparable systems shown in figures 8 and 9 in tables 10 and 11 respectively. The provision of space between the base rails 12 and under lateral frames 21, 22 allows the motion control equipment to be conveniently mounted within the motion platform 10 itself, again reducing the space requirements and complexity of known systems which require external motion control equipment. In this specification an apparatus / method / product "comprising" certain features is intended to be interpreted as meaning that it includes those features, but that it does not exclude the presence of other features. As described here, the base frame, front and rear lateral frames, and HPR frame in combination provide 6 degrees of independent movement. However, these frames also have innovative features that can be advantageously utilised individually or in different combinations, or indeed combined with other movement systems. Some examples are now given. Referring to figure 12, a payload, of which only the tubular frame 16 is shown for simplicity, is mounted on a pitch frame 45, which is mounted on cross roller bearings 25 of a front and rear lateral frames 21, 22. The front and rear lateral frames 21, 22 are mounted on surge base carriages 13 and surge base plate 17 on base rails 12. The base rails 12, front and rear lateral frames 21, 22, and cross roller bearings 25 operate as in the embodiment described in figures 1 to 8, however the pitch frame 45 differs from the HPR frame 31 of figures 1-8 by having a single vertical bell crank 38', and of course does not require wings to carry the additional vertical bell cranks, or horizontal cranks. This system then provides 4 degrees of freedom, being surge, sway, yaw, and pitch. Referring to figure 13, as in the embodiment shown in figures 1 to 8, and the embodiment shown in figure 12, front and rear lateral frames 21, 22 are mounted on surge base carriages 13 and surge base plate 17 on base rails 12, the front and rear lateral frames 21, 22 having cross roller bearing 25. A payload, of which only the tubular frame 16 is shown for simplicity, is mounted on a HPR frame 47. The HPR frame 47 includes four vertical actuators, which could for example be linear actuators, or worm gears. The four vertical actuators are suitable articulated with the tubular frame 16 provide heave, pitch and roll, while the front and rear lateral frames 21, 22 and base rails 12 provide surge, sway and yaw. This, this arrangement provides 6 degrees of freedom. Referring to figure 14, an HPR frame 31 is configured as for figures 1 to 8, including two wings 33 extending from either side of the main longitudinal body of the HPR frame 31, three actuators (only two 34 of which are here visible) which control three vertical bell cranks 38, 38'. As for the HPR frame 31 shown in figures 1 to 8, the two vertical bell cranks 38 mounted on wings 33 have horizontal cranks 36. The payload 15 may be mounted in the same manner as previously described. In this embodiment, no base frame, front and rear lateral frame, or cross roller bearings are included; instead, the HPR frame 31 is mounted on floor pads 48 which rest on the floor. The HPR frame 31 thus supplies 3 degrees of freedom, heave, pitch and roll, while surge, sway and yaw are not provided for. Referring to figure 15, an HPR frame 31 is configured as for figures 1 to 8 and figure 14, including two wings 33 extending from either side of the main longitudinal body of the HPR frame 31, three actuators (only two 34 of which are here visible) which control three vertical bell cranks 38, 38'. As for the HPR frame 31 shown in figures 1 to 8 and figure 14, the two vertical bell cranks 38 mounted on wings 33 have horizontal cranks 36. The payload 15 may be mounted in the same manner as previously described. As for the embodiment shown in figure 14, in this embodiment, no base frame, front and rear lateral frame, or cross roller bearings are included; instead, the HPR frame 31 includes four slidable collars 52 through which surge shafts 50 extend. The slidable collars 52 may be moved along the surge shafts 50 by an actuator (not shown), and the surge shafts 50 are mounted in a conventional manner (not shown) to a fixed structure or the floor. This system thus provides 4 degrees of freedom, the HPR frame 31 providing heave, pitch and roll, while the surge shafts 50 and slidable collars 52 provide surge. Referring to figure 16, an HPR frame 31 mounted on four slidable collars 52 through which surge shafts 50 extend, as previously described and shown in figure 15. The slidable collars 52 are moved along the surge shafts 50 by an surge actuator 55, and the surge shafts 50 are mounted in surge blocks 58 The surge blocks 58 are mounted on cross roller bearings 25 of bearing plates 24. These bearing plates include slidable bores through which lateral shafts 54 extend, these lateral shafts 54 being mounted at their ends in lateral blocks 57 which are fixed or rest upon the floor. Lateral actuators 56 move the bearing plates 24 along the lateral shafts 54. These bearing plates 24 operate then very much like the bearing plates 24 of the embodiment shown and described in figures 1-8, though rather than a lateral frame being mounted on surge plates, instead a surge system (the surge blocks 58, surge shafts 50, surge actuator 55 and slidable collar 52 of the HPR frame 31) is mounted on the lateral movement system. This system thus provides 6 degrees of freedom, the HPR frame 31 providing heave, pitch and roll, while the surge shafts 50 and slidable collars 52 provide surge, and the lateral blocks 57, lateral shafts 54, lateral actuator 56, and cross roller bearings 25 provide yaw and sway. It will be apparent that other combinations could be provide different degrees of freedom and particular movements. Many variations are possible without departing from the scope of the present invention as defined in the appended claims.

Claims

1. A motion platform comprisingcontrol and processing meansan HPR frame assembly capable of translation in a third axis, and capable of rotation around the first and second axes, the first, second and third axes being orthogonal the HPR frame assembly being capable of carrying a payloadcharacterised in that the HPR frame assembly includes at least three independently operable actuators that act in a plane parallel to the first and second axes, each of the three actuators acting on a linkage, such that the three linkages can each be independently translated in the third axis, the linkages being non-colinear.

2. A motion platform according to claim 1 wherein each of the three linkages is a bell crank.

3. A motion platform according to any previous claim wherein each of the three actuators is linear actuator4. A motion platform according to claim 3 wherein the three linear actuators are disposed in parallel, and two of the linkages include a crank which rotates in the plane of a first axis and a second axis, the first axis, second axis and third axis being orthogonal to each other.

5. A motion platform according to any previous claim wherein there is included a lateral frame assembly capable of translation in a second axis perpendicular to a first axis, the first axis being perpendicular to the third axis.

6. A motion platform according to any previous claim wherein there is included a base frame assembly capable of translation in a first axis, the first axis being perpendicular to the third axis, and the first axis being perpendicular to the second axis when dependant on claim 5.

7. A motion platform according to claim 6 when dependant on claim 5, wherein the base frame assembly and lateral frame assembly interacting to be capable of rotation around the third axis.

8. A motion platform according to claim 5 or claims 6 or 7 when dependant on claim 5 wherein the lateral frame assembly includes a front lateral frame having a cross roller bearing and a rear lateral frame having a cross roller bearing.

9. A motion platform according to any of claims 5 to 8 wherein at least part of the three linkages is disposed beneath the upper level of the lateral frame assembly10. A motion platform according to any of claims 5 to 9 wherein at least part of the control and processing means is disposed beneath the upper level of the lateral frame assembly.

11. A motion platform comprisingcontrol and processing meansa base frame assembly capable of translation in a first axisa lateral frame assembly capable of translation in a second axis perpendicular to the first axisthe motion platform being capable of supporting a payload above the base frame assembly and lateral frame assemblythe base frame assembly and lateral frame assembly interacting to be capable of rotation around a third axis, the third axis perpendicular to the first and second axes.

12. A motion platform according to claim 11 wherein the lateral frame assembly includes a front lateral frame having a cross roller bearing and a rear lateral frame having a cross roller bearing.

13. A motion platform according to either of claims 11 or 12 wherein a further frame assembly is included, the frame assembly capable of one or more of the following translations; rotation about the first axisrotation about the second axistranslation through the third axis.AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWSClaims1. A motion platform comprisingcontrol and processing means5 an HPR frame assembly capable of translation in a third axis, and capable of rotationaround the first and second axes, the first, second and third axes being orthogonal the HPR frame assembly being capable of carrying a payloadthe HPR frame assembly includes at least three independently operable actuators that act in a plane parallel to the first and second axes, each of the three actuators acting on a linkage,10 such that the three linkages can each be independently translated in the third axis, the linkages being non-colinear;characterised in that each of the three actuators is linear actuator, the three linear actuatorsbeing disposed in parallel, and two of the linkages include a crank which rotates in the plane of a first axis and a second axis, the first axis, second axis and third axis being orthogonal to15 each other.

2. A motion platform according to claim 1 wherein each of the three linkages is a bell crank that rotates in the vertical plane.20 3. A motion platform according to either previous claim wherein the two cranks which rotatein the plane of a first axis and a second axis are horizontally acting bell cranks.

4. A motion platform according to any previous claim wherein there is included a lateral frame assembly capable of translation in a second axis perpendicular to a first axis, the first 25 axis being perpendicular to the third axis.

5. A motion platform according to any previous claim wherein there is included a base frame assembly capable of translation in a first axis, the first axis being perpendicular to the third axis, and the first axis being perpendicular to the second axis when dependant on claim 5.

6. A motion platform according to claim 5 when dependant on claim 4, wherein the base frame assembly and lateral frame assembly interacting to be capable of rotation around the third axis.

7. A motion platform according to claim 4 or claims 5 or 6 when dependant on claim 4 wherein the lateral frame assembly includes a front lateral frame having a cross roller bearing and a rear lateral frame having a cross roller bearing.16 09 245 8. A motion platform according to any of claims 4 to 7 wherein at least part of the threelinkages is disposed beneath the upper level of the lateral frame assembly9. A motion platform according to any of claims 4 to 8 wherein at least part of the control and processing means is disposed beneath the upper level of the lateral frame assembly.1010. A motion platform comprisingcontrol and processing meansa base frame assembly capable of translation in a first axisa lateral frame assembly capable of translation in a second axis perpendicular to the 15 first axisthe motion platform being capable of supporting a payload above the base frame assembly and lateral frame assemblythe base frame assembly and lateral frame assembly interacting to be capable of rotation around a third axis, the third axis perpendicular to the first and second axes.2011. A motion platform according to claim 10 wherein the lateral frame assembly includes a front lateral frame having a cross roller bearing and a rear lateral frame having a cross roller bearing.25 12. A motion platform according to either of claims 10 or 11 wherein a further frameassembly is included, the frame assembly capable of one or more of the following translations; rotation about the first axisrotation about the second axistranslation through the third axis.15

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