Motion simulator

Abstract

A motion simulator 100 with a platform 104 arranged to carry out sway, surge, and yaw movements relative to its base 102. The base comprises first and second linear base rails 110,112, each extending

Description

Technical Field The present invention relates to motion simulators, particularly though not exclusively to motion simulators for automotive, motorsport, and / or aerospace applications. Background Art A motion simulator may provide for various degrees of freedom, allowing an occupant to be subjected to a range of motions that provide a realistic sensation of being in the environment under simulation. For example, a motion platform may provide an occupant with an accurate sensation of being in a motor racing car, e.g. a Formula One™ car. The six degrees of freedom 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). In some cases, however, simpler motion simulators may be arranged to provide only a subset of these degrees of freedom. Some motion simulators provide only for two degrees of freedom, particularly lateral sway movements together with rotational yaw movements, while other motion simulators may provide yaw movements only. Without out-of-plane movement, such a motion simulator avoids issues with a need to hold a state mass. Additionally, an increased payload simply requires more powerful motors. The motions of a motion simulator may be understood as the motions of a 'platform' part relative to a 'base' part. The platform part is the portion of the motion simulator that moves relative to a static base, and the platform normally being arranged to carry a human user, e.g. a driver, for a given simulation. The platform part may carry a cockpit, cabin, hull, or similar in which a user may position themselves, for example by sitting in a seat. Humans use their vestibular system for their sense of balance and spatial orientation. The vestibular system can be cued with stimuli to give a sense of motion, particularly the onset of acceleration. The Applicant has appreciated that some motion simulators, known in the art perse, do not properly account for vestibularbased cueing. As an example, if a motion simulator is simulating a driving scenario in which a car is cornering and starts to experience slip, in which there is an offset between the direction of the wheel axis and the direction that those wheels are travelling. Depending on the relative slip angles between the front and rear axles of the car, the car may experience understeer (where the car turns less than the amount commanded by the driver) or oversteer (where the car turns more than the amount commanded by the driver). For the user of the motion simulator to experience the correct vestibular cues, the centre of rotation of the platform is critical. There are motion simulators with two degrees of freedom (typically yaw and sway), known in the art perse, that use a fixed point - typically the front of the 'vehicle' - as the centre of rotation for yaw motion. However, this leads to the user experiencing a 'disconnect' between their visual and vestibular systems, which can lead to discomfort or motion sickness. While users can get used to this feeling with time, the Applicant has appreciated that it would be beneficial to avoid this issue altogether. The Applicant has appreciated that a motion simulator with three degrees of freedom of movement -specifically surge, sway, and yaw - may provide for a better experience for the user while avoiding the need to provide the more complex mechanics and control associated with fully six degree of freedom motion. The combination of surge, sway, and yaw motion may be sufficient for certain applications, for example for simulating certain driving conditions. Such a simulator may be well-suited to non-motorsport applications, where out-of-plane motion is less relevant. However, these three degrees of freedom may even be sufficient for some motorsport applications too. The sway, and yaw motions may be used in combination to simulate driving, including driving on straight sections of road, cornering, lane changes, and so on. Summary of the Invention When viewed from a first aspect, embodiments of the present invention provide a motion simulator comprising a base and a platform, said platform being arranged to carry out sway, surge, and yaw movements relative to the base, wherein: a) the base comprises first and second linear base rails, wherein each of said base rails extends along a first axis; b) the platform comprises first and second linear platform rails, wherein each of said platform rails extends along a second axis; c) a first base carriage is mechanically constrained to move along the first linear base rail, and a second base carriage is mechanically constrained to move along the second linear base rail; d) a first platform carriage is mechanically constrained to move along the first linear platform rail, and a second platform carriage is mechanically constrained to move along the second linear platform rail; e) a first motor is arranged to actuate motion of the first base carriage along the first linear base rail, and a second motor is arranged to actuate motion of the second base carriage along the second linear base rail; f) a third motor is arranged to actuate motion of the first or second platform carriage along the respective linear platform rail; and g) the first platform carriage is pivotally coupled to the first base carriage, and the second platform carriage is pivotally coupled to the second base carriage, said pivotal couplings providing for a rotational movement of the platform relative to the base about a moveable rotational centre, wherein a position of the moveable rotation centre is determined by the respective positions of the base and platform carriages. Thus it will be appreciated by those skilled in the art that embodiments of the present invention provide an improved motion simulator with three degrees of freedom that advantageously allows the effective centre of rotation for yaw motion to be moved. Furthermore, such a motion simulator can laterally move perpendicularly regardless of where the platform is located and its rotational angle relative to the base at any moment in time. Thus the motion simulator of the present invention provides both for a variable rotation centre and perpendicular sway motion. The pivotal couplings between the platform carriages and the corresponding base carriages allows the platform to rotate relative to the base. Thus by moving the base carriages and / or the platform carriages relative to one another, lateral and rotational movements can be carried out, providing the desired three degrees of freedom. The Applicant has appreciated that this arrangement is particularly beneficial for slip and vestibular cueing. With a user in situ on the platform (for example sitting in a cockpit or similar mounted to the platform), the user's head - and thus their vestibular - can be moved in-plane and the simulator allows for rotation about a variable point. A further benefit of the motion simulator of the present invention is that it is relatively simple in its mechanics and may allow for a single-stage design, which in turn means that the motion simulator can be relatively compact, lightweight and / or power efficient. The motion simulator of the present invention is also scalable for various travel and payloads, simply by the extending rails or increasing the number of motors used. All three degrees of freedom may be achieved using a combination of the three motors. In preferred embodiments, the platform is arranged to carry out only sway, surge, and yaw movements relative to the base. In other words, the platform does not carry out or roll, pitch, or heave movements relative to the base. Thus the platform is preferably restricted to only these three specific degrees of freedom, i.e. sway, surge, and yaw. As is discussed in further detail below, properties of the motion simulator make it capable of being easily portable, such that it can be transported from one location to another. The motion simulator of the present invention is well-suited to not only motorsport applications but also automotive (i.e. non-motorsport) applications too. Due to the potential for being relatively compact, lightweight, portable, low-cost, efficient, and / or inexpensive compared to other motion simulators known in the art perse, the Applicant has appreciated that embodiments of the present invention may be particularly suitable for automotive applications, where these considerations may impose greater restrictions on what types of motion simulator are appropriate. For example, a motion simulator in accordance with embodiments of the invention might be used to simulate how a road vehicle such as a car for 'normal road use' behaves, e.g. when changing lanes on a motorway. In some embodiments, the second axis is perpendicular to the first axis when the platform is in a predetermined position relative to the base. It will be appreciated that typically, the 'predetermined position' may be a 'rest position' of the platform (i.e. its default position when no motion is being applied), which may for example be the platform centred and facing forwards, i.e. with zero yaw angle applied. As the platform moves, the angles between the platform rails and base rails (as well as the associated motors) may change, e.g. during operation of the motion simulator. Those skilled in the art will readily understand that a rail 'extending along' means that the rail runs parallel to that axis. Thus a carriage coupled to and mechanically constrained to move along a rail travels parallel to the corresponding axis along which the rail extends. It will be appreciated that where a motor is said to 'actuate' motion of a particular carriage, this may be directly or indirectly, however preferably the actuation is direct. Typically, each motor is mechanically coupled to the respective base or platform carriage such that the motor directly drives that carriage to move along the corresponding base or platform rail, as appropriate. Thus in some embodiments, each motor may be arranged to directly actuate the corresponding carriage. Unlike motion simulators that use an XY table, embodiments of the present invention allow direct surge along the direction of the base which provides direct authority from the motor in that direction, rather than a sine or cosine of the yaw angle as with certain prior art systems known in the art per se (e.g. the 'S3' motion simulator made by Ansible Motion). Similarly the difference in travel between the front and rear carriages may maximise the authority to generate yaw and sway. For example, two motors (one on the front of the base and one on the rear of the base) travelling in the same or opposite directions (as appropriate) may provide greater torque output and have a higher authority (and therefore better control) than a single motor. The third motor enables motion of the platform in a direction perpendicular to the direction of motion provided by the first and second motors, and may be used for braking and / or acceleration cues. The first and second motors may provide for movement in the sway direction while the third motor may provide for movement in the surge direction. The third motor may provide for actuation in the appropriate direction to one of the platform carriages, and the other may be passive. However, in some embodiments, the third motor is arranged to actuate motion of the first platform carriage along the first linear platform rail, and a fourth motor is arranged to actuate motion of the second platform carriage along the second linear platform rail. In other words, both platform carriages may be provided with a motor for actuation in that direction, e.g. in the surge direction. The three degrees of freedom may be achieved with only two sets of carriages, one per pair of base and platform rails. However, in some embodiments, the motion simulator is further arranged such that: i) the platform further comprises a third linear platform rail, wherein the third platform rail extends along the second axis; ii) a third base carriage is mechanically constrained to move along the first linear base rail; iii) a third platform carriage is mechanically constrained to move along the third linear platform rail; and iv) the third platform carriage is pivotally coupled to the third base carriage. The Applicant has appreciated that the addition of a third pair of carriages may provide for better stability of the motion simulator. In some such embodiments, a further motor is arranged to actuate motion of the third platform carriage along the third linear platform rail. In some potentially overlapping embodiments, the motion simulator is further arranged such that: i) the platform further comprises a fourth linear platform rail, wherein the fourth platform rail extends along the second axis; ii) a fourth base carriage is mechanically constrained to move along the second linear base rail; iii) a fourth platform carriage is mechanically constrained to move along the fourth linear platform rail; and iv) the fourth platform carriage is pivotally coupled to the fourth base carriage. In some such embodiments, a respective further motor is arranged to actuate motion of the fourth platform carriage along the fourth linear platform rail. Each of the platform rails may be physically separate from one another. However, in some embodiments multiple platform rails may together form a continuous platform rail. For example, in embodiments in which only two pairs of base and platform carriages are used (e.g. for front and rear), these may be aligned with one another along the surge direction, in which case a single continuous platform rail may serve as both first and second linear platform rails. Similarly, in embodiments in which four pairs of base and platform carriages are used (e.g. for fro nt-1 eft, front-right, rear-left, and rear-right), these may be aligned with one another along the surge direction such that the front-left and rear-left pairs may share a 'left' platform rail and / or such that the front-right and rear-right pairs may share a 'right' platform rail. Thus one continuous (e.g. 'left') platform rail may comprise both the first and second linear platform rails, while another continuous (e.g. 'right') platform rail may comprise both the third and fourth linear platform rails. The base rails are, at least in some embodiments, physically separate from one another. Having the base rails physically separate is advantageous for portability, as allowing these to be detached from one another may make physically handling and moving the base rails easier, e.g. for transportation. Electronics modules - e.g. any controller, or other electronics such as for power and / or communications functions - may, in some embodiments, be positioned between the base rails. This may advantageously improve the compactness of the design. As outlined above, the pivotal couplings between the platform and base carriages provide for rotational movement of the platform relative to the base. The pivotal coupling may be provided by any suitable type of pivotal coupling member. For example, in some embodiments, one or more (and potentially each) base carriage is pivotally coupled to the corresponding platform carriage via a pivotal coupling member. In some embodiments, the or each pivotal coupling member comprises one or more of: a pivot joint, a pin joint, a revolute joint, a hinge joint, a cylindrical joint, a gimbal, a spherical joint, a spherical bearing, a spherical ball joint, or a universal joint. The Applicant has appreciated that pivotal coupling members that allow for some degree of out-of-plane rotational motion (e.g. a gimbal, spherical joint, spherical bearing, spherical ball joint, or universal joint) may assist in allowing for any inadvertent vertical misalignment between the base rails. Such misalignment may, for example, occur where the motion platform is portable, such that when positioned and installed there may be some unwanted gradient difference between the front and rear base rails. In general, the first and second base rails extend parallel to the sway direction, while the first and second platform rails extend parallel to the surge direction. As such, one of the first and second base rails can be seen as a 'front' base rail, with the other being a 'rear' base rail. In some embodiments, the first base rail is a front base rail, and the second base rail is a rear base rail (though the reverse may be true in other embodiments, with the first base rail being a rear base rail, and the second base rail being a front base rail). In embodiments with three sets of base carriages, these may be arranged such that two of these (e.g. the first and third) are arranged to move along the front base rail, with one base carriage (e.g. the second) arranged to move along the rear base rail. Alternatively, these may be arranged such that two of these (e.g. the first and third) are arranged to move along the rear base rail, with one base carriage (e.g. the second) arranged to move along the front base rail. There are many types of motor, known in the art perse, that may be readily used with embodiments of the present invention. However, in some embodiments, wherein one or more of the motors respectively comprises a linear motor. In a particular set of embodiments, each motor respectively comprises a linear motor. The or each linear motor may, at least in a set of such embodiments, comprise a magnet-free linear motor, for example magnet-free track linear motors. The Applicant has appreciated that magnet-free linear motors are typically cheaper than ironless linear motors, providing a reduction in material costs of the platform for a trade-off in peak force output. While magnet free linear motors may have a lower peak force output than some other types of motors, the Applicant has appreciated such motors may nevertheless be sufficient for moving the platform (where the payload may be limited through advantageous choice of materials) for motorsport applications where accelerations may be approximately 10 ms’2. However, high specification motors could be used if higher accelerations are needed for a particular application. In other embodiments, the linear motors may comprise ironless linear motors. A combination of different types of motors may be used, if appropriate. Control of the motors may be conducted via a suitable controller, which may form part of the motion simulator itself or may be external. However, in some embodiments, the motion simulator further comprises a controller configured to cause the carriages to move relative to one another, optionally wherein the controller is configured to generate a control signal for each carriage dependent on a planned motion input received by said controller. For example, simulation software may be used in conjunction with the motion simulator to provide a user on or in the platform to experience the simulated environment and perceive motions accordingly via the user's senses (e.g. visual and vestibular). The simulation software may generate motion inputs which are supplied to the controller, and the controller generates control signals for actuating the carriage(s) to give rise to the desired motion of the platform. In some embodiments, the first and second linear base rails are of different lengths. In at least some embodiments, the first linear base rail may be longer than the second linear base rail. In certain embodiments, this means that the front base rail is longer than the rear base rail, though in other embodiments the reverse may be true (i.e. the rear base rail may be longer than the front base rail). Having the one base rail longer than the other may enable a greater degree of yaw motion and / or a greater range of travel (e.g. in the sway direction), while minimising the physical footprint of the motion simulator. It will be appreciated that here the term 'length' means in the direction in which the rail extends. As mentioned previously, the motion simulator may be portable, such that it can be moved from one location to another relatively easily. The Applicant has appreciated that certain further features may advantageously further enhance the portability of the motion simulator. The Applicant has appreciated that typically a motion simulator may be fixed to a floor (e.g. with a bolting system) to avoid unwanted movement of the motion simulator itself (e.g. through unwanted motion of its base relative to the surrounding environment). Such a fixing system may make the motion simulator less portable. In some embodiments, the motion simulator may comprise a ballast arrangement. In some such embodiments, the ballast arrangement may comprise a fillable ballast tank. The base may, in some such embodiments, comprise the ballast tank. Conversely, a fillable ballast tank allows the nominal mass of the motion platform to be reduced (enhancing portability), where the ballast tank can be filled with a suitable substance such as water or sand when the motion platform is in situ where it is to be used, potentially temporarily before being moved elsewhere. Additionally, or alternatively, the ballast arrangement may comprise one or more removable ballast weights. The base may, in some such embodiments, comprise the one or more removable ballast weights. Such ballast weights may be of sufficiently high mass to prevent unwanted movement of the motion simulator as a whole but can be removed from the motion simulator to allow it to be moved or transported. The one or more ballast weights may comprise plates, or any other suitable form of weight, as appropriate. The first and second base rails may, in some embodiments, be mechanically coupled to one another via a bracing arrangement. This bracing arrangement may ensure the base rails are aligned correctly, which may be particularly important where the motion simulator is intended to be portable. Such a bracing arrangement may comprise one or more brace brackets. These brace brackets may, in some such embodiments, be detachable such that the base rails can be decoupled from one another for transport. Where a ballast arrangement (e.g. a fillable ballast tank and / or removable ballast plates) is used, this ballast arrangement may be positioned or positionable on the bracing arrangement when installed. Embodiments of the present invention may advantageously provide flexibility in the power supply the motion simulator requires. The Applicant has appreciated that a motion simulator in accordance with certain embodiments of the present invention may be run using a single-phase electricity supply, rather than requiring three-phase power. This is highly advantageous because it enables the motion simulator to be installed in a wider variety of locations where three-phase power is not readily available. This may be particularly advantageous where the motion simulator is portable. However, in some embodiments three-phase power may be used, e.g. where high power motors are required - for example a 40 A three-phase supply may be used. In a particular set of embodiments, the motion simulator is operable in a first power mode in which it receives a single-phase power supply, and is further operable in a second power mode in which it receives a three-phase power supply. In other words, a given motion simulator may be able to use either single-phase or three-phase power, as appropriate for a given installation. In some potentially overlapping embodiments, the motion simulator may comprise a capacitor arrangement configured to provide additional power during an excess load condition. Such a capacitor arrangement (which may be a single capacitor or multiple capacitors) may cover bursts of peak acceleration, which may be typical in motorsport simulation. This may be particularly advantageous when using a single-phase power supply, however this may also be advantageous even with the use of three-phase power. In some embodiments, the or each base carriage comprises aluminium or a composite material. In particular, one or more of the base carriages may comprise one or more of: carbon fibre, aluminium, titanium, and honeycomb / foam. In some potentially overlapping embodiments, the or each platform carriage comprises aluminium or a composite material. In particular, one or more of the platform carriages may comprise one or more of: carbon fibre, aluminium, titanium, and honeycomb / foam. The Applicant has appreciated that an advantageous material choice for these carriage(s) is one that is both light (to keep the moving mass down) and stiff (to improve the performance). Optional features set out in respect of any aspect of the invention are also applicable to the other aspects of the invention as appropriate. In the context of this specification "comprising" is to be interpreted as "including". Approximately as employed herein is defined as + 10%. Aspects of the invention comprising certain elements are also intended to extend to alternative embodiments "consisting" or "consisting essentially" of the relevant elements. Where technically appropriate, embodiments of the invention may be combined. Embodiments are described herein as comprising certain features / elements. The disclosure also extends to separate embodiments consisting or consisting essentially of said features / elements. It should be noted that ordinal terms of a given numeric rank do not necessarily imply the existence of corresponding ordinals of a lower numeric rank. For example, the term 'fourth' in respect of certain elements or features does not necessarily imply the inclusion of a 'third' of such elements or features. Technical references such as patents and applications are incorporated herein by reference. Any embodiments specifically and explicitly recited herein may form the basis of a disclaimer either alone or in combination with one or more further embodiments. Brief Description of the Drawings Certain embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Figs. 1A to IE are mechanical diagrams of a motion simulator in accordance with an embodiment of the present invention; Fig. 2 is a simplified schematic model of the motion simulator of Fig. 1; Figs. 3A to 3D are simplified schematic models showing surge and sway movements of the motion simulator of Fig. 1; Figs. 4A to 4D are simplified schematic models showing yaw and variable yaw movements of the motion simulator of Fig. 1; Fig. 5 is an illustration of an oversteer scenario with a vehicle cornering; Fig. 6 is a simplified schematic models of a motion simulator in accordance with a further embodiment of the invention; Fig. 7 is a simplified schematic models of a motion simulator in accordance with a yet further embodiment of the invention; Fig. 8 is a mechanical diagram showing a bracing arrangement for the base in embodiments of the present invention; Fig. 9 is a mechanical diagram showing a ballast arrangement for use with embodiments of the present invention; Fig. 10 is a mechanical diagram showing a motion simulator in accordance with another embodiment of the invention that is arranged for additional travel; Fig. 11 is a mechanical diagram showing a further ballast arrangement for use with embodiments of the present invention; and Fig. 12 is a mechanical diagram showing a motion simulator in accordance with another embodiment of the present invention in which the rear base rail is longer than the front base rail. Detailed Description Figs. 1A to IE are mechanical diagrams of a motion simulator 100 in accordance with an embodiment of the present invention. The motion simulator 100 comprises a base 102 and a platform 104. The platform 104 is arranged to carry out sway, surge, and yaw movements relative to the base 102. Figs. 1A to ID respectively show perspective, front, size, and top views of the motion simulator 100. Fig. IE shows a cutaway view of the base 102 of the motion simulator 100. The various components of the motion platform 100 are simplified in the schematic model of Fig. 2. The platform 104 carries a cockpit 106 shaped like the cockpit of a motorsport vehicle, where a user 108 can sit during operation of the motion simulator 100. This cockpit 106 could be replaced with, for example, a cabin, hull, etc. corresponding to some other type of vehicle, as appropriate. The base 102 comprises a front linear base rail 110 and a rear linear base rail 112, wherein each of said base rails 110,112 extends along a first axis. The front base rail 110 has a length Lfront and the rear base rail 112 has a length Lrear, as illustrated in Figs. ID and IE. In this particular embodiment, the length LfrOntof the front base rail 110 is longer than the length Lrear of the rear base rail 112. Having one base rail longer than the other may enable a greater degree of yaw motion about the drivers vestibular. It should be noted, however, that it is also possible to have the rear base rail 112 be longer than the front base rail 110 (i.e. such that Lrear is greater than Lfront)- In an example of such an arrangement, a pair of base carriages may travel along the rear base rail 112, with a single base carriage travelling along the front base rail 110, i.e. the 'reverse' of the embodiment shown in Figs. 1A to IE could be used instead. Such a configuration may still allow for more travel at the front in the sway direction. An example of such an arrangement is shown in Fig. 12. The base 102 may include a tillable ballast tank (not shown) which can be used to weigh down the motion simulator 100, e.g. by filling the ballast tank with water, sand, concrete, or some other substance which can be removed to enhance portability of the motion simulator 100. Alternatively, ballast weights (e.g. plates) may be used to weigh down the motion simulator 100. Example of ballast arrangements are described later with reference to Figs. 9 and 11. The platform 104 comprises a front-left linear platform rail 114, a front-right linear platform rail 116, and a rear linear platform rail 118. Each of the platform rails 114,116, 118 extends along a second axis, perpendicular to the first axis. A front-left base carriage 120 and a front-right base carriage 122 are mechanically constrained to move along the front base rail 110. A rear base carriage 124 is mechanically constrained to move along the rear base rail 112. A front-left platform carriage 126 and a front-right platform carriage 128 are mechanically constrained to move along the front-left and front-right platform rails 114,116 respectively. Similarly, a rear platform carriage 130 is mechanically constrained to move along the rear platform rail 118. A motor - the front sway motor 132 - is arranged to actuate motion of the front-left base carriage 120 along the front linear base rail, with the front-right base carriage 122 being passive and 'pushed along', though it will be appreciated that it is possible to motorise both base carriages 120,122. A further motor -the rear sway motor 134 - is arranged to actuate motion of the rear base carriage along the rear linear base rail. The motors that actuate motion of the base carriages are collectively referred to as the 'sway motors'. Another motor - the surge motor 136 - is arranged to actuate motion of the rear platform carriage along the respective linear platform rail. It will be appreciated that the front-left and / or front-right platform carriage(s) 126,128 could be provided with a respective surge motor in addition to, or instead of, the surge motor 136 provided to the rear platform carriage 130. The motors that actuate motion of the platform carriages are collectively referred to as the 'surge motors'. At a minimum, three motors are required for the three degrees of freedom to be achieved - a front sway motor, a rear sway motor, and a surge motor. With these three motors and the pivotal couplings, as explained below, motion in the sway, surge, and yaw directions can be achieved. Each platform carriage 126,128,130 is pivotally coupled to the corresponding base carriage 120,122,124 via a respective pivotal coupling member 138. These pivotal couplings 138 providing for a rotational movement of the platform 104 relative to the base 102 about a moveable rotational centre. The position of the moveable rotation centre is determined by the respective positions of the base carriages 120,122,124 and platform carriages 126,128,130 as explained in more detail later. The various motors 132,134, 136 are, in this embodiment, magnet-free linear motors. Figs. 3A to 3D are simplified schematic models showing surge and sway movements of the motion simulator 100 of Fig. 1. Figs. 3A and 3B respectively show rearward and forward surge motion. As can be seen in Fig. 3A, to achieve rearward surge motion, the surge motor 136 drives the platform carriages 126,128,130 forward along the respective platform rails 114, 116, 118 thereby causing the platform 104 to surge rearwards relative to the base 102. Conversely, to achieve forward surge motion as shown in Fig. 3B, the surge motor 136 drives the platform carriages 126,128,130 rearwards along the respective platform rails 114,116,118 thereby causing the platform 104 to surge forwards relative to the base 102. Figs. 3C and 3D respectively show left and right sway motion. As can be seen in Fig. 3C, to achieve left sway motion, the front sway motor 132 drives the front base carriages 120,122 to the left along the front base rail 110, and the rear sway motor 134 drives the rear base carriage 124 to the left along the rear base rail 112, thereby causing the platform 104 to sway left relative to the base 102. Conversely, to achieve right sway motion as shown in Fig. 3D, the front sway motor 132 drives the front base carriages 120,122 to the right along the front base rail 110, and the rear sway motor 134 drives the rear base carriage 124 to the right along the rear base rail 112, thereby causing the platform 104 to sway right relative to the base 102. Figs. 4A to 4D are simplified schematic models showing yaw movements of the motion simulator 100 of Fig. 1. Fig. 4A shows a left yaw motion of the motion simulator 100. To yaw to the left, the front sway motor 132 drives the front base carriages 120, 122 to the left along the front base rail 110, while the rear base carriage 124 is retained in its central position. Conversely, Fig. 4B shows a right yaw motion of the motion simulator 100. To yaw to the right, the front sway motor 132 drives the front base carriages 120,122 to the right along the front base rail 110, while the rear base carriage 124 is retained in its central position. In both yaw movements, the pivotal coupling members 138 enable the platform 104 to rotate relative to the base 102. Furthermore, the platform carriages 126, 128,130 shift up or down the respective platform rails 114,116, 118 due to the mechanical constraints. Figs. 4C and 4D also illustrate yaw motion to the left and right respectively, however the motions in Figs. 4C and 4D also incorporate sway motion to change the centre of rotation. In Fig. 4C, the left yaw motion of Fig. 4A is combined with the left sway motion of Fig. 3C. Similarly, in Fig. 4D, the right yaw motion of Fig. 4B is combined with the right sway motion of Fig. 3D. In each instance, this causes the effective centre of rotation to move. An example of the impact of this movement of the effective centre of rotation is described below with reference to Fig. 5. It will be appreciated that by combining the sway, surge, and yaw motions to various degrees, the platform 104 can be moved with three degrees of freedom as required during simulation. The above movements shown in Figs. 3Ato 3D and 4A to 4D illustrate specific magnitudes of motion in the yaw, sway, and surge directions, however larger or smaller movements in these directions may be achieved by moving the carriages to larger or smaller extents, as appropriate. The three degrees of motion can also be combined as necessary in accordance with the needs of the simulation. Fig. 5 is an illustration of an oversteer scenario with a vehicle cornering. As explained below, Fig. 5 shows that both the radius of rotation and the centre of rotation shift during such an event. Embodiments of the invention aim to stimulate the vestibular in a similar (intuitive) way by changing both the rotation centre and yaw angle to stimulate the vestibular. As shown in Fig. 5, the motion simulator is being used in the simulation of a car 150 driving around a road corner 152. Initially, as the car 150 begins to turn the corner, the motion simulator carries out a yaw motion as outlined previously, with an effective centre of rotation 154 at the position marked 'A' on Fig. 5. The radius ri to the centre of rotation 154 is measured from the vestibular 109 of the user to the effective centre of rotation 154. This effective centre of rotation 154 is the centre of rotation with no oversteer (or understeer). As the car 150 continues around road corner 152, it enters oversteer. To simulate this, the motion simulator combines sway and yaw motion to shift the effective centre of rotation to a new centre of rotation 154' at the position marked 'B' on Fig. 5. This change in the centre of rotation is marked Ar on Fig. 5. As can be seen from Fig. 5, the radius r2 to the new effective centre of rotation 154' is less than the radius ri to the previous centre of rotation 154. Thus by reducing this radius, this provides the sensation of the car 150 rotating at a greater angular rate than is intended or commanded by the driver, i.e. the motion simulator is correctly simulating the effects of the car 150 being in oversteer. The Applicant has appreciated that the motion simulator does not need to specifically use three pairs of base and platform carriages. While three pairs may be preferred over two pairs for enhanced stability, the motion simulator may nevertheless function using only two pairs. Conversely, more than three pairs of such carriages might be used, for example four. Figs. 6 and 7 are simplified schematic models of two further motion simulators 200, 300 in accordance with further embodiments of the invention. Elements having reference numerals starting '2' in Fig. 6 and / or starting '3' in Fig. 7 are alike in form and function with those elements having reference numerals starting with '1' in Figs. 1A-E, 2, 3A-D, 4A-D, and 5, unless technical context dictates otherwise. In Fig. 6, the motion simulator 200 has four pairs of base carriages and platform carriages, such that there are two base carriages arranged to move along the front base rail 210, and two base carriages arranged to move along the rear base rail 212. The platform 204 is provided with two platform rails 214, 216, which are parallel and each extend in the surge direction. The front-left and rear-left platform carriages are coupled to and mechanically constrained to move along the left platform rail 214, while the front-right and rear-right platform carriages are coupled to and mechanically constrained to move along the right platform rail 216. In this embodiment, two front sway motors 232, 233 are provided on the front-left and front-right base carriages respectively. Similarly, two rear sway motors 234, 235 are provided on the rear-left and rear-right base carriages respectively. Thus in this embodiment, all the base carriages are motorised for sway movement, however it will be appreciated that the front and / or rear base carriages may only have one motor per side (i.e. one for the front and one for the rear), if appropriate, with one base carriage per side being motorised and the other being passive. In this embodiment, there are also two surge motors 236, 237, with one surge motor 236 being provided to the rear-left platform carriage and the other surge motor 237 being provided to the rear-right platform carriage. It will be appreciated that surge motors could, additionally or alternatively, be applied to the front respective platform carriages on the left and / or right platform rail, potentially with surge motors for all platform carriages. As with the previous embodiment, the base and platform carriages are coupled to one another via pivotal coupling members 238 which allow the platform 204 to rotate relative to the base 202. Similarly to the first embodiment, by using the sway motors 232, 233, 234, 235 and / or surge motors 236, 237 (as appropriate), the platform 204 can be moved relative to the base 202 in the sway, surge, and yaw directions, providing three degrees of freedom. Alternatively, as shown in in Fig. 7, a motion simulator 300 in accordance with another embodiment may make use of only two pairs of base and platform carriages. A front base carriage is arranged to move along the front base rail 310, and a rear base carriage is arranged to move along the rear base rail 312. The platform 204 is provided with a single platform rail 314 which extends in the surge direction. Front and rear platform carriages are each coupled to and mechanically constrained to move along the platform rail 314. In effect, in this embodiment the 'front' and 'rear' platform rails form a continuous singular platform rail 314. As with the previous embodiment, the base and platform carriages are coupled to one another via pivotal coupling members 338 which allow the platform 304 to rotate relative to the base 302. In this embodiment, a front sway motor 332 is provided on the front base carriage, and a rear sway motor 334 is provided on the rear base carriage. A surge motor 336 is provided on the rear platform carriage. It will be appreciated that a surge motor could, additionally or alternatively, be applied to the front platform carriage, potentially with surge motors for both platform carriages. As with the previous embodiments, by using the sway motors 332, 334 and / or surge motor 236 (as appropriate), the platform 304 can be moved relative to the base 302 in the sway, surge, and yaw directions, providing three degrees of freedom. Fig. 8 is a mechanical diagram showing a bracing arrangement for the base in embodiments of the present invention. The bracing arrangement can be used with any of the motion simulators 100, 200, 300 outlined above, or any other embodiment of the present invention such as the motion simulator 800 described below with reference to Fig. 12. The base 102, 202, 302 comprises a number of front-to-rear braces 450 which mechanically couple the front base rail 110, 210, 310 to the rear base rail 112, 212, 312. These braces 450 ensure the front and rear rails are aligned correctly. The braces 450 may be detached from one or both of the base rails to assist with transport. Fig. 9 is a mechanical diagram showing a ballast arrangement for use with embodiments of the present invention. The ballast arrangement can be used with any of the motion simulators 100, 200, 300 outlined above, or any other embodiment of the present invention such as the motion simulator 800 described below with reference to Fig. 12. In this arrangement, a number of ballast weights 560 in the form of plates can be positioned on the base 102, 202, 302 to weigh down the motion simulator 100, 200, 300 to prevent the base 102, 202, 302 itself from moving during use. These ballast weights 560 are removable such that they can be taken off to allow for transport of the motion simulator 100, 200, 300. These ballast weights 560 could be positioned on top of the braces 450 as described previously with reference to Fig. 8. It will of course be appreciated that the ballast weights may be positioned elsewhere and still provide the necessary weighting to prevent unwanted movement of the base 102, 202, 302, as appropriate. Fig. 10 is a mechanical diagram showing a motion simulator 600 which is arranged for additional travel compared to the motion simulators 100, 200, 300 described previously. This arrangement can of course be combined with any of the motion simulators 100, 200, 300 outlined above, or any other embodiment of the present invention. Elements having reference numerals starting '6' in Fig. 10 are alike in form and function with those elements having reference numerals starting with '1' in Figs. 1A-E, 2, 3A-D, 4A-D, and 5, unless technical context dictates otherwise. As mentioned previously, in any embodiment of the present invention either the front or rear base rail may be longer than the other base rail. However, in Fig. 10 it can be seen that both the respective lengths LfrOnt', Lrea / of the front and rear base rails 610, 612 are greater than the corresponding lengths LfrOnt, Lrear of the front and rear base rails 110,112 in the motion simulator 100 of the first embodiment, as shown in e.g. Figs. ID and IE. In this case, the front base rail is longer than the rear base rail, but the same principle is applicable in alternative embodiments where the rear base rail is the longer one. By extending the base rails 610, 612 in this way (i.e. by making them longer in the direction along which they extend, in this case the sway direction), the motion simulator 600 is provided with a greater range of motion. In this embodiment, the greater range of sway motion provided may enable one-to-one lane changes or other such motions to be simulated. As can be seen in Fig. 10, the front base rail 110, 210, 310 is coupled to the rear base rail 112, 212, 312 via braces 650 like those described previously with reference to Fig. 8. It will be appreciated, however, that the additional travel may be achieved via the difference in lengths without necessarily including these braces 650. It will also be appreciated that while a motorsport style cockpit 606 is shown in Fig. 10, this arrangement may readily be used for non-motorsport applications, such as for road vehicles. Any of the embodiments described herein may be used for motorsport and / or non-motorsport applications, as appropriate. Fig. 11 is a mechanical diagram showing a further ballast arrangement for use with embodiments of the present invention. The ballast arrangement can be used with any of the motion simulators 100, 200, 300 outlined above, or any other embodiment of the present invention such as the motion simulator 800 described below with reference to Fig. 12. Rather than using ballast weights 560 in the form of plates like in the arrangement of Fig. 9, in the arrangement of Fig. 11 a fillable ballast tank 770 is positioned on the base 102, 202, 302. By filling the ballast tank 770 with a suitable substance (e.g. sand, water, concrete, etc.), this weighs down the motion simulator 100, 200, 300 to prevent the base 102, 202, 302 itself from moving during use. The ballast tank 770 can then be emptied to allow for transport of the motion simulator 100, 200, 300. The ballast tank 770 could be positioned on top of the braces 450 as described previously with reference to Fig. 8. It will of course be appreciated that the ballast tank 770 may be positioned elsewhere and still provide the necessary weighting to prevent unwanted movement of the base 102, 202, 302 as appropriate. Fig. 12 is a mechanical diagram showing a motion simulator 800 in accordance with another embodiment of the present invention in which the rear base rail 812 is longer than the front base rail 810. As can be seen in Fig. 12, the length Lrear" of the rear base rail 812 is greater than the length Lfront" of the rear base rail 810. In an example of such an arrangement, a pair of base carriages may travel along the rear base rail 812, with a single base carriage travelling along the front base rail 810, i.e. the 'reverse' of some of the embodiments described previously. This configuration may still allow for more travel at the front in the sway direction. It will be appreciated that the motion simulator 800 may be combined with the features described above in respect of any of the other embodiments. For example, the motion simulator 800 may utilise more or fewer 5 base and platform carriages (as per Figs. 6 and 7), a bracing arrangement (per Fig. 8), ballast plates (per Fig. 9), a fillable ballast tank (per Fig. 11), and / or lengthened base rails (per Fig. 10), as appropriate. It will be appreciated, therefore, that embodiments of the present invention provide an improved motion simulator with three degrees of freedom that may be relatively compact, lightweight, portable, low-cost, efficient, and / or inexpensive compared to other motion simulators known in the art perse. This motion 10 simulator may therefore be well-suited to both motorsport and non-motorsport applications. 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. 15

Claims

1. A motion simulator comprising a base and a platform, said platform being arranged to carry out sway, surge, and yaw movements relative to the base, wherein:a) the base comprises first and second linear base rails, wherein each of said base rails extends along a first axis;b) the platform comprises first and second linear platform rails, wherein each of said platform rails extends along a second axis;c) a first base carriage is mechanically constrained to move along the first linear base rail, and a second base carriage is mechanically constrained to move along the second linear base rail;d) a first platform carriage is mechanically constrained to move along the first linear platform rail, and a second platform carriage is mechanically constrained to move along the second linear platform rail;e) a first motor is arranged to actuate motion of the first base carriage along the first linear base rail, and a second motor is arranged to actuate motion of the second base carriage along the second linear base rail;f) a third motor is arranged to actuate motion of the first or second platform carriage along the respective linear platform rail; andg) the first platform carriage is pivotally coupled to the first base carriage, and the second platform carriage is pivotally coupled to the second base carriage, said pivotal couplings providing for a rotational movement of the platform relative to the base about a moveable rotational centre, wherein a position of the moveable rotation centre is determined by the respective positions of the base and platform carriages.

2. The motion simulator as claimed in claim 1, wherein the second axis is perpendicular to the first axis when the platform is in a predetermined position relative to the base.

3. The motion simulator as claimed in claim 1 or 2, wherein the third motor is arranged to actuate motion of the first platform carriage along the first linear platform rail, and a fourth motor is arranged to actuate motion of the second platform carriage along the second linear platform rail.

4. The motion simulator as claimed in any preceding claim, wherein the first and second linear platform rails are physically separate from one another.

5. The motion simulator as claimed in any of claims 1 to 3, wherein the first and second linear platform rails together form a continuous linear platform rail.

6. The motion simulator as claimed in any preceding claim, wherein:i) the platform further comprises a third linear platform rail, wherein the third platform rail extends along the second axis;ii) a third base carriage is mechanically constrained to move along the first linear base rail;iii) a third platform carriage is mechanically constrained to move along the third linear platformrail; andiv) the third platform carriage is pivotally coupled to the third base carriage.

7. The motion simulator as claimed in claim 6, wherein a further motor is arranged to actuate motion of the third platform carriage along the third linear platform rail.

8. The motion simulator as claimed in claim 6 or 7, wherein the third linear platform rail is physically separate from the first and second linear platform rails.

9. The motion simulator as claimed in any preceding claim, wherein:i) the platform further comprises a fourth linear platform rail, wherein the fourth platform rail extends along the second axis;ii) a fourth base carriage is mechanically constrained to move along the second linear base rail;iii) a fourth platform carriage is mechanically constrained to move along the fourth linear platform rail; andiv) the fourth platform carriage is pivotally coupled to the fourth base carriage.

10. The motion simulator as claimed in claim 9, wherein a respective further motor is arranged to actuate motion of the fourth platform carriage along the fourth linear platform rail.

11. The motion simulator as claimed in claim 9 or 10, wherein the fourth linear platform rail is physically separate from the first and second linear platform rails.

12. The motion simulator as claimed in claim 9 or 10 when dependent on claim 6, wherein the fourth linear platform rail is physically separate from the third linear platform rail.

13. The motion simulator as claimed in claim 9 or 10 when dependent on claim 6, wherein the third and fourth linear platform rails from a second continuous linear platform rail.

14. The motion simulator as claimed in any preceding claim, wherein one or more base carriages is pivotally coupled to the corresponding platform carriage via a pivotal coupling member, optionally wherein the or each pivotal coupling member comprises one or more of: a pivot joint, a pin joint, a revolute joint, a hinge joint, a cylindrical joint, a gimbal, a spherical ball joint, or a universal joint.

15. The motion simulator as claimed in any preceding claim, wherein the first base rail is a front base rail, and the second base rail is a rear base rail.

16. The motion simulator as claimed in any preceding claim, wherein one or more of the motors respectively comprises a linear motor, optionally wherein the or each linear motor comprises a magnet-free linear motor, further optionally wherein the or each linear motor comprises a magnet-free track linear motor.

17. The motion simulator as claimed in any preceding claim, further comprising a controller configured to cause the carriages to move relative to one another, optionally wherein the controller is configured to generate a control signal for each carriage dependent on a planned motion input received by said controller.

18. The motion simulator as claimed in any preceding claim, wherein the first and second linear base rails are of different lengths, optionally wherein the first linear base rail is longer than the second linear base rail.

19. The motion simulator as claimed in any preceding claim, further comprising a capacitor arrangement configured to provide additional power during an excess load condition.

20. The motion simulator as claimed in any preceding claim, further comprising a ballast arrangement.

21. The motion simulator as claimed in claim 20, wherein the ballast arrangement comprise a fillableballast tank, optionally wherein the one or more fillable ballast tank is positioned or positionable on the base.

22. The motion simulator as claimed in claim 20 or 21, wherein the ballast arrangement comprises one or more removable ballast weights, optionally wherein the one or more removable ballast weights are positioned or positionable on the base.

23. The motion simulator as claimed in any preceding claim, wherein the base comprises a bracing arrangement for detachably coupling the first and second base rails to one another, optionally wherein a ballast arrangement is positioned or positionable on the bracing arrangement.5 24. The motion simulator as claimed in any preceding claim, operable in a first power mode in which itreceives a single-phase power supply, and is further operable in a second power mode in which it receives a three-phase power supply.

25. The motion simulator as claimed in any preceding claim, wherein one or more of the base carriages comprise one or more of: carbon fibre, aluminium, titanium, and honeycomb / foam; and / or wherein 10 one or more of the platform carriages comprise one or more of: carbon fibre, aluminium, titanium,and honeycomb / foam.15

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