GB2491648A

GB2491648A - Motion simulator

Info

Publication number: GB2491648A
Application number: GB1109781.3A
Authority: GB
Inventors: Christopher Shane Huxley-Reynard
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-06-11
Filing date: 2011-06-11
Publication date: 2012-12-12
Anticipated expiration: 2031-06-11
Also published as: GB201109781D0; GB2491648B

Abstract

A motion simulator comprises a fixed base (1) to which is mounted a main boom (2) which pitches about a horizontal axis under the action of a first actuator (4). A capsule support arm (5) is mounted on the end of the main boom and is able to pitch relative to it under the action of a second actuator (7). A capsule capable of carrying persons is mounted to the capsule support arm and is able to roll relative to it under the action of a third actuator (10). The main boom is pitched back and forth in a vertical plane by the first actuator to induce a varying linear acceleration at the capsule. The direction in which this acceleration is perceived to act by persons inside the capsule is controlled by the second and third actuators. Figure

Description

Motion Simulator

Background

A wide range of motion simulators already exist to simulate the motion of land and water based vehicles, aircraft and spacecraft. Different types of simulator are suited to different types of vehicle simulation. important considerations when designing a simulator are: -what degrees of freedom are required to replicate the range of attitudes and directions of motion that a person experiences in the real vehicleS -what range of motion is required in each direction to allow accelerations to be simulated which are of sufficiently high magnitude or of sufficiently prolonged duration to feel like the real vehicle.

-whether high frequency, small amplitude accelerations important for the particular vehicle being simulated.

-whether linear accelerations of less than 1.Og magnitude need to be simulated (e.g a flight simulator).

-whether sustained accelerations above of greater than 19 magnitude are desirable (eg rocket launch simulation).

-how the simulator avoids impacting the ground or its end stops in the event of a systems failure.

Prior Art

Some examples of prior art are cited below with their advantages and disadvantages.

Many different designs of Stewart Platform motion simulators are already commercially available. They offer 6 degrees of freedom motion over a limited linear and angular range and can induce linear accelerations less than ig magnitude. They are the normal choice for commercial flight simulators where they offer a very authentic motion simulation for normal aircraft attitudes / manoeuvres. They cannot usually induce prolonged accelerations above a fraction of a g, nor can they invert the occupant capsule. By virtue of their limited range of physical motion they do not usually pose a significant safety hazard in terms of hitting end stops or the ground too hard.

Centrifuges can induce high and varying g for a sustained period. If the occupant capsule is mounted on a gimble frame at the end of the centrifuge arm this acceleration can be made to act in any direction as perceived by persons onboard the occupant capsule. Centrifuges generally require a long arm to minimise the rate of rotation required to simulate a given g level, otherwise the occupant will suffer disorientation/vertigo. As a result centrifuges can be large in physical size requiring powerful drive motors, and therefore tend to be expensive to build. They cannot simulate accelerations of less than ig magnitude without complex modification and this limits their applicability for many vehicle simulations where reduced g is required.

The "Robocoaster" device as proposed in European patent EP 1437162 "Ride Apparatus" is a 6 degree of freedom motion simulator based around an industrial robot arm that is capable of inducing high magnitude and prolonged accelerations for a wide range of capsule orientations. lf the main arm of the Robocoaster is yawed continuously it is also capable of inducing sustained accelerations on the capsule acting like a centrifuge. Prolonged accelerations are possible because of the length of the mechanical linkages on the Robocoaster which allow the occupant capsule to be swung several metres away from the central body of the unit. Due to the kinematic design of the linkage arrangement of the Robocoaster, a controller or actuator malfunction could in theory cause the capsule to hit the ground or the linkages to come up hard against their end stops, causing unacceptably high impulses to be imparted to the capsule. This potential safety issue is mitigated by the use of sophisticated control/safety systems to prevent such a malfunction in the first place, backed up by the use of impact absorbing crush elements which limit the impulse experienced in the unlikely event that such a failure should occur.

The performance of this simulator is impressive and it appears to offer significant advantages over a Stewart Platform in terms of the range of motion, attitudes and duration of accelerations induced. The high number of degrees of mechanical freedom combined with its physical size, sophisticated control system and failsafe crushable element mechanical backup system add significant complexity and expense to the device however.

The "Maxf light" simulator as proposed in European patent EP 0 808 493 "Improved Flight Simulator" has 2 degrees of freedom and is significantly simpler than the Robocoaster. The occupant compartment is mounted on the end of a boom which can pitch in a vertical plane through 360 degrees. The capsule can also roll through 360 degrees on the end of said boom. By controlling the pitch and roll orientations of the capsule the 1 g acceleration due to gravity can be made to act in any direcUon as perceived by persons onboard the simulator. Angular acceleration of the boom also allows a linear inertial acceleration component to be induced in addition to that experienced from gravity alone, by virtue of the fact that the occupant compartment centre of gravity is removed from the pitch axis. This allows increased and reduced g to be usefully simulated over a limited range of movement of the boom. The main limitation of this design is that the direction in which this inertial acceleration acts relative to the direction that gravity acts changes as the occupant compartment is pitched through 360 degrees. As such it is not possible to simultaneously control the magnitude and direction of the net linear acceleration (inertial acceleration plus gravity) through the full range of vertical plane motion of the boom. In practice this means that increased and reduced g can only be usefully simulated when the boom is substantially horizontal and the inertial acceleration acts roughly in line with gravity. This limitation essentially arises because of the limited degrees of freedom of the simulator.

A second Maxf light" simulator is described WO 03/100749 "Improved Flight Simulator" which incorporates several additional degrees of rotational and linear freedom, improving the performance of the device but adding to its complexity. A centrifuge arrangement allows sustained g accelerations of magnitude above ig to be induced on the capsule. The capsule is mounted on the end of the boom in such a manner that it can both pitch and roll relative to the end of the boom allowing the sustained g induced by the centrifuge action to be vectored to act in any direction as perceived by persons onboard the occupant compartment. As described in the patent application the device can only simulate reduced g when the main boom is substantially horizontal, as is the case for the 2 degree of freedom version of the Maxf light simulator. The proposed system is mechanically complex and would be relatively expensive to build.

Other motion simulators embody 3 degrees of freedom to independently raise, pitch and roll an occupant capsule. Examples of such devices are: -US Patent 5388991 "Simulation Device and System", Donald L. Morris -US Patent 4019261 "Motion System for a flight Simulator", Edward C, Pancoe These simulators offer a limited range of movement and/or the risk of impacting the occupant capsule against the ground in the event of systems malfunction.

Statement of the invention

The present invention seeks to improve on the Stewart platform in terms of the magnitude and duration of induced accelerations, whilst avoiding the risk of the simulator hitting the ground or its end stops. It retains the ability to simulate accelerations of less that one g magnitude unlike a centrifuge, although it cannot simulate sustained accelerations, It seeks to achieve these improvements at an affordable cost through a simple and inherently failsafe mechanical design.

The proposed motion simulator comprises a main boom attached towards its bottom end to a fixed base. The main boom pitches about a horizontal axis relative to the fixed base, driven by a first actuator. Attached towards the top end of the main boom is a capsule mounting arm which further pitches relative to the main boom under the action of a second actuator. Attached to the capsule mounting arm is a capsule capable of carrying persons aboard which rolls relative to the capsule mounting arm under the action of a third actuator.

in operation, the body of the capsule swings back and forth in a vertical arc on the end of the main boom under the action of the first actuator, whilst the capsule is further pitched and rolled relative to the end of the main boom under the action of the second and third actuators.

During operation a control system controls the magnitude of net linear acceleration seen by the capsule through the first actuator and the apparent direction this acceleration acts as perceived by those onboard the capsule through the second and third actuators. By pitching the main boom using the first actuator an angular acceleration is induced at the capsule about the bottom end of the main boom. A centripetal acceleration about the same point is also induced, being a function of the pitch rate of the main boom. These 2 components of acceleration are vectorially combined with the acceleration due to gravity to result in a net linear acceleration at the capsule which can be actively controlled by the first actuator within a defined acceleration operating envelope. By simultaneously pitching and roiling the capsule on the end of the main boom using the second and third actuators respectively, the direction in which the net linear acceleration acts as perceived by persons in the capsule is controlled in real time. By way of example, it is possible to make an occupant feel that they are experiencing increased g pushing them straight down into their seat even though the main boom may be orientated vertically upwards or vertically downwards.

There are limits on the instantaneous net linear acceleration that can be induced at the capsule. These limits will depend on the dimensions of the motion simulator as well as the instantaneous pitch angle of the main boom and its angular pitch rate. in some instances the controller will be forced to induce an acceleration that is different from the demanded value in order to keep the motion simulator operating within its working limits of main boom pitch angle and pitch rate.

In one embodiment of the invention the main boom is able to swing through 36Odegrees without the capsule hitting the ground or another part of the simulator. This is a safety feature which prevents injury to occupants onboard the capsule in the event of control system or actuator failure.

In another embodiment of the invention the first actuator is a linear ram attached between the fixed base and the main boom. Use of a linear actuator (for example a hydraulic ram) allows high torques to be transmitted to the main boom, and rapid changes in torque to be achieved at potentially lower cost than a rotary actuator. Use of such an actuator limits the controllable pitch angle range for the main boom to less than 180 degrees since. However if the working stroke of the linear actuator is designed to be within its maximum stroke, the inertia of the capsule could drive the main boom past this 180 degree working range in the event of a control system or actuator failure without causing the actuator to hit its end stops. This is a useful safety feature.

Advantages The proposed invention has the following principal advantages: -accelerations can be induced for a longer period compared to a Stewart Platform.

-accelerations below ig magnitude can be simulated over a larger range of motion than other comparable motion simulators.

-the system can be designed to be inherently safe avoiding collision of the capsule with the ground or another part of the simulator in the event of control system or actuator failure.

-it is mechanically simple and thereby affordable to build.

-it can make use of a cheap linear actuator to power the main boom where most of the mechanical work is done, further reducing cost.

Introduction to drawings

Figures 1 a and 1 b show front and side elevations respectively of a first embodiment of the present invention in which the main boom is able to swing through a complete revolution without causing the capsule to impact the ground or any other part of the motion simulator.

Figures 2a and 2b show front and side elevations respectively of the same embodiment of the invention as illustrated in Figures 1 a and 1 b, but with the main boom and capsule in different orientations.

Figures 3a and 3b show front and side elevations respectively of an embodiment of the invention in which the first actuator used for driving the main boom pitch angle is a linear hydraulic ram.

Detailed description with reference to drawings

Different versions of the invention will now be described, by way of example and not in any limiting sense, with reference to the accompanying drawings.

Referring to Figures 1 a and 1 b, the fixed base (1) supports the main boom (2) via a horizontal axis bearing (3). The main boom pitches in an arc in the vertical plane under the action of a rotary actuator (4). The capsule support arm (5) is mounted to the main boom via a second horiztonal axis bearing (6) and driven by a second actuator (7), which in this case is a rotary actuator.

This enables the capsule pitch angle to be controlled independently of the pitch angle of the main boom. The capsule (8) is mounted to the capsule support arm via a third bearing (9) which is orthogonal to the second bearing (6). A third actuator (10), which in this case is a rotary actuator, drives the roll angle of the capsule relative to the capsule support arm. A controller (11) controls the three actuators in real time according the the methodology described under the statement of the invention. As shown in these figures the main boom is in a raised position with the capsule mounting arm pitched such that the capsule points roughly towards the centre of rotation of the main boom. The roll angle of the capsule is zero in these figures.

Referring to Figures 2a and 2b, the motion simulator is the same device that is shown in Figures 1 a and 1 b however the position of the main boom, capsule mounting arm and capsule are different. The main boom (2) is in a lowered position with the capsule mounting arm pitched such that the capsule pointing approximately at right angles to the main boom. The capsule is rolled at an angle of approximately 45degrees relative to the capsule mounting arm.

Referring to Figures 3a and 3b, the motion simulator shown is an alternative embodiment in which the first actuator which drives the pitch angle of the main boom is a hydraulic ram (4). In this embodiment the hydraulic ram is connected at its bottom end to the fixed base (1) and at its top end to a main boom extension arm (12). The main boom extension arm is coupled directly to the main boom itself through the inside of the horizontal axis bearing (3).

During normal operation the pitch angle of the main boom is driven between the vertically up and vertically down positions by the extension and retraction of the hydraulic ram. The ram has sufficient working stroke such that in the event of controller or actuator failure the mechanical arrangement allows the main boom (2) to over-rotate and swing through a complete revolution without causing any part of the motion simulator to impact another part or the ground.

It will be appreciated to persons skilled in the art that there are other arrangements for connecting the Unear actuator (4) to the main boom (2) which are within the scope of this invention.

Claims

Claims 1. A motion simulator comprising a fixed base; a main boom rotatably connected to the fixed base allowing pitching of the main boom about a first axis which is horizontal under the action of a first actuator; a capsule mounting arm which is bodily removed from the first axis, rotatably connected to the main boom allowing pitching of the capsule mounting arm relative to the main boom about a second axis which is horizontal under the action of a second actuator; a capsule capable of carrying persons rotatably connected to the capsule mounting arm allowing rolling of the capsule relative to the capsule mounting arm about a third axis which is perpendicular to the second axis, wherein the second and third axes pass through the body of the capsule, and wherein said rolling of the capsule occurs under the action of a third actuator; a control system controlling the three fore-mentioned actuators; a control method for controlling the magnitude and direction of the acceleration experienced by persons onboard the capsule, said method using the first actuator primarily to rotate the main boom back and forth in the vertical plane to induce a net linear acceleration on the capsule by virtue of the combined angular, centripetal and gravitational accelerations acting upon it, and using the second and third actuators primarily to pitch and roll the capsule relative to the main boom to control the direction in which said net linear acceleration acts as perceived by persons onboard the capsule.
2. A motion simulator as claimed in claim 1 wherein the capsule can roll through a complete turn about the third axis without hitting the ground or any other part of the motion simulator.
3. A motion simulator as claimed in any previous claim wherein the capsule mounting arm can pitch through a complete turn about the second horizontal axis without causing the capsule to hit the ground or any other part of the motion simulator.
4. A motion simulator as claimed in any previous claim wherein the main boom can rotate by a complete turn about the first horizontal axis without the capsule hitting the ground or another part of the motion simulator.
5. A motion simulator as claimed in any previous claim wherein the first actuator is a linear actuator connected between the main boom and the fixed base.
6. A motion simulator as claimed in any previous claim wherein the motion simulator is principally controlled by the persons located in the capsule by means of controls located therein.
7. A motion simulator as claimed in claim 6 wherein the persons in the occupant compartment can experience force feedback on the controls linked to the motion they experienceS 8. A motion simulator as claimed in any previous claim wherein the persons in the occupant compartment may experience additional vibration or discrete mechanical impulses in the occupant compartment, such vibration being intentionally superimposed upon the normal motion of the simulator by means of additional actuators fitted to the motion simulator.9. A motion simulator substantially as claimed and described herein.Amendments to the claims have been filed as follows: 1. A motion simulator comprising a fixed base; a main boom rotatably connected to the fixed base allowing pitching of the main boom about a first axis which is horizontal under the action of a first actuator; a capsule mounting arm which is bodily removed from the first axis, rotatably connected to the main boom allowing pitching of the capsule mounting arm relative to the main boom about a second axis which is horizontal under the action of a second actuator; a capsule capable of carrying persons rotatably connected to the capsule mounting arm allowing rolling of the capsule relative to the capsule mounting arm about a third axis which is perpendicular to the second axis, wherein the second and third axes pass through the body of the capsule, and wherein said rolling of the capsule occurs under the action of a third actuator; V-' a control system controlling the three fore-mentioned actuators.(\J 2. A motion simulator as claimed in claim 1 wherein the capsule can roll C through a complete turn about the third axis without hitting the ground or any other part of the motion simulator.3. A motion simulator as claimed in any previous claim wherein the capsule mounting arm can pitch through a complete turn about the second horizontal axis without causing the capsule to hit the ground or any other part of the motion simulator.4. A motion simulator as claimed in any previous claim wherein the main boom can rotate by a complete turn about the first horizontal axis without the capsule hitting the ground or another part of the motion simulator.5. A motion simulator as claimed in any previous claim wherein the first actuator is a linear actuator connected between the main boom and the fixed base.6. A motion simulator as claimed in any previous claim wherein the motion simulator is principally controlled by the persons located in the capsule by means of controls located therein.7. A motion simulator as claimed in claim 6 wherein the persons in the occupant compartment can experience force feedback on the controls linked to the motion they experience.
8. A motion simulator as claimed in any previous claim wherein the persons in the occupant compartment may experience additional vibration or discrete mechanical impulses in the occupant compartment, such vibration being intentionally superimposed upon the normal motion of the simulator by means of additional actuators fitted to the motion simulator.
9. A motion simulator substantially as claimed and described herein.
10. A method for controlling a motion simulator as described in any previous claim, wherein the magnitude and direction of the acceleration experienced by persons onboard the capsule are controlled by using the first actuator primarily to rotate the main boom back and forth in the vertical plane to induce a net linear acceleration on the capsule by virtue of the combined angular, centripetal and gravitational accelerations acting upon it, and using the second and third actuators primarily to pitch and roll the capsule relative to the main boom to control the direction in which said net linear acceleration acts as perceived by persons onboard the capsule. (4 (4N