CA2182372A1 - Motion control systems - Google Patents
Motion control systemsInfo
- Publication number
- CA2182372A1 CA2182372A1 CA 2182372 CA2182372A CA2182372A1 CA 2182372 A1 CA2182372 A1 CA 2182372A1 CA 2182372 CA2182372 CA 2182372 CA 2182372 A CA2182372 A CA 2182372A CA 2182372 A1 CA2182372 A1 CA 2182372A1
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- CA
- Canada
- Prior art keywords
- actuator
- signals
- motion
- control
- monitoring
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09B—EDUCATIONAL OR DEMONSTRATION APPLIANCES; APPLIANCES FOR TEACHING, OR COMMUNICATING WITH, THE BLIND, DEAF OR MUTE; MODELS; PLANETARIA; GLOBES; MAPS; DIAGRAMS
- G09B9/00—Simulators for teaching or training purposes
- G09B9/02—Simulators for teaching or training purposes for teaching control of vehicles or other craft
- G09B9/08—Simulators for teaching or training purposes for teaching control of vehicles or other craft for teaching control of aircraft, e.g. Link trainer
- G09B9/12—Motion systems for aircraft simulators
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60G—VEHICLE SUSPENSION ARRANGEMENTS
- B60G17/00—Resilient suspensions having means for adjusting the spring or vibration-damper characteristics, for regulating the distance between a supporting surface and a sprung part of vehicle or for locking suspension during use to meet varying vehicular or surface conditions, e.g. due to speed or load
- B60G17/015—Resilient suspensions having means for adjusting the spring or vibration-damper characteristics, for regulating the distance between a supporting surface and a sprung part of vehicle or for locking suspension during use to meet varying vehicular or surface conditions, e.g. due to speed or load the regulating means comprising electric or electronic elements
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- Engineering & Computer Science (AREA)
- Theoretical Computer Science (AREA)
- Aviation & Aerospace Engineering (AREA)
- Business, Economics & Management (AREA)
- Physics & Mathematics (AREA)
- Educational Administration (AREA)
- Educational Technology (AREA)
- General Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Vehicle Body Suspensions (AREA)
Abstract
The motion of a member such as a simulator plane and a "virtual reality" cabin, or a vehicle, is controlled by apparatus comprising one or more preferably electromagnetic actuators disposed between the member and a ground level, and a control arrangement for providing signals to the actuator whereby to cause the actuators to generate thrust. In order to allow the motion of the member to be influenced by factors such as the movement of a user on the simulator plane, or the detection of other movements, the apparatus further comprises means for monitoring characteristics of the relative positions or movements of the member and the ground level, or the forces between the ground level, the actuator and the member, and providing signals indicative of said characteristics. The control arrangement is responsive to signals provided by the monitoring means and comprises means for generating or modifying the control signals to be provided to the actuator.
By controlling the motion of a member in this way, it is possible to make motion systems such as "virtual reality" system more convincing. It is also possible to construct stabilizing systems such as active suspension systems for vehicle.
By controlling the motion of a member in this way, it is possible to make motion systems such as "virtual reality" system more convincing. It is also possible to construct stabilizing systems such as active suspension systems for vehicle.
Description
o 2182372 MOTION CONTROL SYSTEMC
- The present invention relate~ to an apparatus for controlling the motion of an object. In particular it relates to motion control apparatus wherein forces are generated by actuators such as electromagnetic actuators having a piston and a cylinder and in which relative motion is caused to happen between the piston and the cylinder by means of electromagnetic force.
Examples of such electromagnetic rams are disclosed in International Patent Application No. PCT/GB92/01277, published as WO 93/016J.6.
The present invention also relates to a corresponding method for controlling the motion of an object or objects by means actuators such as for example, electromagnetic actuators.
The present invention has applications in the field of motion simulation. Motion simulators are now used in, for example, flight simulators for training pilots, an~ in arcade games based on activities such as motor-cycle racing. In these examples, motion simulation is generally f-nh~nred by the provision of audio visual signals to the user ir. order to make the experience of actual motion seem more realistic. Such motion simulators are now known to the general public as "virtual reality" ~--hin~c and are becoming more widely available for recreational and educational uses. In general motion simulators are known which utilize hydraulic or pneumatic rams as the actuators providing the n~ress~ry forc~s to move a user who may be in a simulator cabin or on a simulator plane. More recently it has been proposed by the inventor of the present application to utilize ele~L~ ~ gn~tic actuators as the thrust producers in motion simulation devices ~see, for example, International Application PCT/GB92/01279, published as Wo 93/01577 ) .
. ~ 2182372 It is knl~wn for motion simulators, comprising a set of actuators arranged between a base plane and a simulator plane or cabin, to provide motion simulation according to a predetPnmi ned program, wherein each actuator operates according to predetPnmi nPd time pPn~lPnt functions or to stored data in order to cause a sequence of thrusts or moves to be applied to a simulator cabin or simulator plane. In this way a user on the simulator plane may experie~ce a "virtual reality ride" around a well-known motor racing circuit or down a well-known t~hqgg~ll run, for example. Such simulators may be said to pro~ide "hard" simulation of a predetPnrni nPd experience in the sense that the actuators apply set sPtIupn~-pq of thrusts or moves to the simulator plane or cabin irrespective of ally action on the part of a user in a cabin or on a simulator plane. It is also known for a user, or an externaL controller, to be able to control the thrusts to be applied to the cabin or simulator plane, by operation of, for exa~ple a steering wheel or a joy-stick control system. Such simulators are able to provide si 1;~ n of a non-predetprmi npd experience, but may still be said to be providing "hard"
simulation since tlle motion or thrusts applied to the cabin or simulator plane are still detPrminP~, albeit contemporaneously, by a computer contro1 ~ni 1'."
responsive only to external ~ '-.
A particular example of motion simulator employing a combination of the above two types of "hard"
simulation would be a flight simulator in which a user in a cabin, the inside of which is intended to look and feel like a cock pit, controls an "aeroplane" by operating controls similar to those of a real aircraft.
Signals from these controls are processe~ and applied to a set of actuators arranged to change the position and orientation of the cock pit in order that the user experiences the ef Fects of his own control of the plane 0 ~182372 until such time as his actions, if carried out in an aeroplane, would have resulted in an unrecoverable crash. At such a time as this, the control of the actuators may be ta~ken completely away from the user and instead, the actuators may be controlled to simulate a crash by running a predetPrr~i nPd sequence of moves .
Irrespective of whether the f light simulator according to this example is in the first mode ~i.e. under the user's control), or in the second mode ~i.e. performing the predetPrminpd "crash" routine), the simulation may be said to be "hard" on account of the fact that the actuators are only responsive to externally driven It is desired to provide motion simulators in which signals provided to an actuator or to a set of actuators are detPrminPd not only from external .ic but also, for example, from L..~v~ L of a user in a cabin or on a simulator plane. Signals determined as a result of v L of the user may thus be provided to the actuators in acdition to a predet~rmi nP-i sequence of signals such that the user feels that his changes in position are affecting the motion of the object whose motion is being simulated. For example in a simulator for simulating surfing on the sea, wherein a surf-board is placed on a simollator plane, the actuators may be provided with signals such that the simulator plane moves as if under the action of waves, and in addition to this, they may be provided with additional signals if a "surfer" on the surf-board shifts his weight relative to the surf-board, such that the motion of the surf-board is affected by the v~ Ls of the surfer. Such simulation may be referred to as "soft" simulation.
According to the present invention there is provided apparatus for controlling the motion of a member, comprising an actuator disposed between the member and a ground level, and a control aLLa~ L
0 2182~72 for providing control signals to the actuator whereby to cause the actu~tor to generate thrust, characterised in that said apparatus further comprises means for monitoring cha:racteristics of the relative positions or movements of tlle member and the ground level or the forces between ground level, actuator and member, and providing signals indicative of said characteristics, and in that the control arrangement is responsive to signals provided by the monitoring means and comprises means for modi~ying or generating the control signals to be provided to the actuator.
Preferred 'i Ls of the invention utilize electromagnetic actuators and make use of the feature of these that in ~ddition to converting electrical signals to thrust, they may produce electrical signals directly as a result of force being applied to them.
In the field of motion simulation outlined above, apparatus according to an : ' of the present invention in general comprises a plurality of actuators disposed between a plane resting on the ground and an object on which a user may "ride". The object on which the user rides may be located on a plane which is attnched to the actuators, or may be attached to the actuators itself.
In order for motion simulation to be "soft" it is generally necessary for the apparatus to include means for monitoring characteristics of the position or v~ of the member of a user on the member, although it may be necessary also to monitor ~uLL-7~ i characteristics of the ground plane in some circumstances . In motion simul2tors ~ i ng a preferred: ' i L of the apparatus according to the present invention, use is preferably made of the fact that currents are generated in the coils of an electromagnetic actuator when there is relative movement between the pis~on and the cylinder, and by monitoring these currents, the extension or reduction of the actuators as a ~esult of ~c L of the user may be monitored without the need for further connections or sensors to be mounted on the actuators. Alternatively, however movemenl:s of the user may be detected by 1~ 218237~
monitoring other characteristics, such as the angles between the actuators, the lengths of the actuators, or the rate of change of extension or reduction of the length of the actuators. Also, .~ Ls of the user may be detected more directly by attaching .c sensors of any convenient type to the user or to the member, or by any other convenient means.
Signals indicative of characteristics of the position of movement of the member, having been obtained by any chosen form of monitoring means, may be processed by computer contro l means such as to provide contro l signals to the actuator which are the sole control signals to the act~ators. AlternatiYely, a predetPrminPri sequence of control signals may be modified as a result of signals received from the monitoring means in order to "superimpose" the effects of a users I ~, Ls on a prede~Prmi nPd ride. In either such situation, the simulated motion may be said to be "soft" .
As PYrl iinP~ above, motion simulators Utili71ng -j ts of the present invention generally include more than one electL, - ~ic ram, and may also include other support means such as air springs. It is not, however, nPcPqs~ry for there to be a plurality of actuators, and a f~rther application of -'i Ls of the present invention, in which a single actuator may suffice, will be ou~tlined below.
It is well known that spring systems and spring damper combinations can be modelled by computer and that ideal spring and/or damper systems can be designed in this w~y. However, when putting such computer modelling into practice it is often the case that design, ~ , i CP9 have to be made. In the past, spring and damper combinations have been adjustable to the extent that th~ damper characteristics may be switched but again these are very crude systems when ~182372 comp~red with the comput~r modelling which is possible.
The adv~nt of electromagnetic piston and cylinder devices capable oE producing high thrusts has allowed designers to produce any desir~d thrust characteristic prof i le .
~ le now propose utilizing the controllable aspect of a~ elec~romagnetic piston and cylinder device to drive the pistcn forwards and backwards at rates det~rrni n~d by the designer and between limit positions also det~rmi n~ b~y the designer in order to simulate a specific spring o~- combination of springs or in:~t1~n of springs and daupers. The advantage of using an ~lectromagnetic r~lm system is that because the switching of the coils whic}l causes the relative ~ b~twee~
the pisto~ and cylinder i already under computer control, it is possible to feed new pL~L~ to the ~ r which wi:Ll 71ter the characteristics of the piston and cylind~r device.
Piston and cylinder actuators controlled according to some: i ~5 of the present invention as set out above uay be made to act as "virtual springs", "virtua3. dampers " or "virtual spring/damper ' inA1 l~n~ ti~li7ing terminology used in the field of "virtual reality". A particular application of such ~ is in the field of suspension systems, such a~ active s~Cp~n~L~n systems for vehicles. As explained above, an ele_Ll, Lic actuator controlled according to ~ '' ~ of the precent invention may be controlled such t}lat it acts as a sprinq or a combination of splings, a damper or a - inAtinn of dampers, or a, inJ-rir~n of spri~gs and damperY. In s~Cponci~n systems, the aim of controlling the motion may be thought of as the reverse of that Ln motion simulatlon, since it is generally desired to allow a user a smooth a ride as possible in, for example, situations whe~eill a vehicle is travelling over ` 218237~
irregular terrain. The monitorinq of v L is thus principally directed to that of a base plane or a set of wheels, which may be considered to travel across the "ground level", but monitoring means similar to those described in relation to motion simulators may be used.
Other applications of the present invention will become appare~t from a full description of Ls of the invention.
r ~ rlts of the prese~t invention will now be described with reference to the Ar- -nying figures in which:
Figure 1 shows in diagrammatical form a motion simulator of a kno~n type which may be controlled according to an: 'i L of the present invention;
Figure 2 shows a perspective view of a simulator Pni~-" such as that shown in Fig. l;
Figure 3 shows the two principal parts of an electromagnetic actuator;
Figure 4 shows a piston suitable for use in an alternative type of electromagnetic actuator;
Figures 5, 6 and 7 show alternative arr In; c of an electromagnetiC actuator;
Flgure 8 shows a circuit for supplying current to, and receiving current from, an electromagnetic actuator;
Figure 9 shows, in diagrammatical form, an -~i L of a motion control apparatus accordin~ to the present invention;
Figure 10 shows, in diagrammatical form, an active suspension system of a car, controlled according to an 'i L of the present invention;
Referring to Figure 1, there is shown in diagrammatical form a motion simulator to which an _'i L of the motion control apparatus of the present invention may be applied. A motion simulator of this type, but for "hard" simulation was the subject ~182372 of In~rnA~ nA1 Publication W094/10665, filed by the applicant of the present application, the subject matter of which is incorporated herein by reference.
As shown, there is a base plane 10, which may rest on a floor or be otherwise stably supported, and a simulator plane 40 on which may be mounted a capsule motor-cycle, or surf-~oard, for example, (not shown) that is to undergo simulated motion. The capsule may represent a cabin, such as an aircraft cabin, in which a user would stay during use in order to be subjected to v~ L .
On the base plane 10 are mounted three actuators 30 which are linearly ~yt~nrlihle elect-, ~..e~ic ra~,s. ~iote that although no connections to the actuators 3a are shown in Figure l, connections would in general be required for electrical power and signals, and possikly for fluid, as will be r~ lAin~d later. The actuators are mounted in such a way that each is free to rotate in direction A with one deqree of freedom about a point 24 on the base plane 10. For example, the actuators 30 may be mounted by means of hinges 26 whose axes each lie in the base plane 10. In general, the axes about which the acLue-Lu~ . are free to rotate ( in the example, the axes of the hinges ) can be extended so as to intersect with each other at points forming a notional triangle 20 with sides 22 on the base plane 10. This notional triangle 20 is in this 'i L an equilateral triangle. The axes of the actuators 30 intersect with the axes about which they are free to rotate at points 24 which are midpoints of the sides 22 of the triangle 20 on the base plane 10.
These points 24 can be thought of as the coupling points of the actuators 30. In this example, each coupling point 24 is the midpoint of one of the sides 22 of the triangle 20. They thus form a smaller triangle within the triangle 20. On account of this, the axes of the 2~2372 _ 9 _ actuators 30 diverge from points on a common line irrespective of their angular positions, this line preferably being the line perpPnAic~ r to the base plane, passing through the centroid of one or both of the triangles.
Each act~lator 3 0 may be extended or shortened in directions B by a length up to that of piston 32 which in general has a length less than or equal to the length of the actuator, bu~ may be longer if it is extendible in stages, with for example a telescopic action or if the cylinder is open-ended and the piston is allowed to move through it. The piston 32 may be supported by a slide bearing 38, to further strengthen the structure of the simulation ;~ni cn- The pistons 32 of the actuators 30 are each ~oined to a point of the simulator plane 40 by means of a uniYersal bearing 36, the three bearings forming a notional triangle 50. This notional triangle S 0 is in this case an equilateral triangle and is in the simulator plane 40. The two notional triangles 20 and 50 may be of a similar size or of different slzes, ~PpPnriing on the required extent of the motion and the stability required. Generally however the centre of mass of the capsule should be aboYe the centroid of the triangle 50. In addition, the centre of mass of the capsule should be kept, to a required level of accuracy, above the centroid of the -points at which the actuators are coupled to the base plane. This condition may be maintained by suitable choices of sizes a~d positions of the triangles 20 and 50, lengths of the actuators 30 and/or external control of the types of v~ Ls that are caused by PYtF~n~linq and shortening the actuators. (This external control may be by physically preventing the actuators from reaching angles outside a required range, or by computer control of the lengths of the actuators according to prP~Pt~rminpr1 algorithms or contemporaneous 1-- 2~82372 calculations. ) The coupling points of the actuators 30 to the triangle 20 on the base plane 10 should thus be separated sufficielltly from each ol;her for the triangle 20 to be sufficiently large to provide a means of transferring the forces produced by the actuators to the stable base plane 10.
Referring to Figure 2, there is shown a perspective view o~ a simulator -- ~ni ~m such as that shown diagrammatically in Figure 1.
Prior to explaining how a simulator ;Ini~
such as that shown in Figs. 1 and 2 may be controlled according to the present invention, some types of electromagnetic actuator suitable for use in such a -hlni~ Will be clescribed with reference to Figures 3, 4, 5 and 6. Such ~.ctuators are the subject of International Publi.cation WO 93/01646, filed by the applicant of the present invention, the subject matter of which is incorporated herein by reference.
Referring to Figure 3, there are shown the two principal parts of an electromagnetic actuator, which are, respectively, the cylinder 130 and the piston 135.
In this example, the cylinder 130 houses a plurality of annular coils 131 which are separated from each other by pole-piece rings 132. The piston 135 is of a suitable size to slide within the central bore of the cylinder 130, and comprises a cylindrical steel sleeve 136 on the exterior of which are mounted a plurality of segme~ted windings 137. Currents in the coils 131 on the cylinder may be proYided such that radial magnetic fields are produced which interact with currents in the piston coils 137, whose phase is controlled according to the position of the piston and the required thrust direction. Alternatively, currents flowing in the piston coils 137 may produce radial magnetic fields which interact with ~ILL~IlLS in the cylinder windings 131. A piston for an actuator such as this is shown in 237~
Fig. 4, in which the piston comprises a steel core 140 provided with annular pole-pieces 141 and coils 142.
Alternative actuator arrA~ are possible. Two further examples are shown in Figs. S and 6. In Fig. 5, there is shown, al~ actuator wherein a cylinder 191 carries a plurality oE annular coils 192, and wherein a piston 190 carries radially magnetised ring-magnets 193. By applying suitable currents to the coils 192, the pisl:on 190 may be made to experience an electromagnetic fo3 ce such as to extend or shorten the actuator. In Fig. 6, however, the steel cylinder 201 carries a series 03f ring magnets 202 which are radially magnetised, while the piston 20~ carries segmented coils 204, to which current may be applied to cause electromagnetic force to be generated such as to extend or shorten the actwator.
As is evident from the above electromagnetic actuators for use in ~ -'i Ls of the present invention may be 03- a variety of types, providing it is possible to energise coils in either the piston or the cylinder such as to generate electromagnetic forces between the coils ~nd a magnetic system in the other one of the piston and the cylinder. The ~--gnPri, system may be a single p~3~-n~nt magnet, a series of p~r~-n,-nt magnets, or one or more current-carrying coils.
While th~ principal function of the electromagnetic actuators is to produce thrusts, it is advantageous in embodiments of the present invention if the actuators are adapted to perform the reverse operation, this being the generation of currents in coils in either the piston or cylinder as a result of relative motion between the piston and the cylinder. ~y virtue of this it is possible to detect slight changes in the positional relatic~nchip of the piston and the cylinder by monitoring currents in the coils. It is further possible to utilize the currents in the coils to , ~ ~lg2372 recharge a battery, for example or to provide power for use in the apparatus.
A further type of electromagnetic actuator which is suitable for use in 'l Ls of the present i~Lvention, will briefly be described with reference to Figure 7. A full description of the unit, and in particular its electromagnetic properties will not be given as the basic unit may be o~ any of the types referred to earlieJ~ or referred in our International Patent Application W093/01646, or otherwise. In this example, however t~1e principal features of the electL - ~ic r~l include a cyli~der 230 having stator coils 231, and pis1:on 232 having p~ n~nt magnets 233, 234 mounted thereoll. Additionally, the stator i nrl conductive rings 2:15 at either end of the stator which may be made of cop~er or ;,1 'ni for example, and act electrical c~ch~nn~ to pr~vent violent impact by the piston at th~ extremes of L,~ L~
The above! description refers pr;nrirJl Iy to electromaLg~Letic ac~.uators 11~Lving a piston and a cylinder, ho~ever in certain applications of the invention it may be~ advantageous to utilize other types of actuators, such as rotary torque a- LuaL~ s. rt is thu$ not i n~on~lod that this inve~Ltion is limited to ~y~tem~ in which piston and cylinder a~ LuaLora are or sy~tem~ in whic~ the actuators are el~_L. ic.
In general, it is rL~c~c~-ry for an elccLL -~ic ra~L to hav~ means to allow fluid to pass out from the inside of the cylinder a~ it isl _ _~sed by the ~. of the piston. In this example, ports ar~ irLdicated as being connected to an air reservoir which also in v.~o.~Les a~L air-pump. This may be used to assist the elect~, Lic ram i~L providing large thrusts, or by controlling the f luid pL~3~ to a required level, it may be possible for a load to be supported completely by fluid pressure, until such ti~Le as the loa~ changes or moves. once such a chan~e alters ~ 2372 the pressure from the load on the piston, the piston will move due to the pressure in the piston from the air reservoir/pump and due to the effect described above in which relative motion of the piston and cylinder will generate an electr~ ~nf~tc current, it will be possible to detect the ~ v~ .L of the piston by virtue of the monitoring of the detected currents, and it is also envisaged that the currents generated by such relative motion may be used to supply power to the system, or may be stored f or use in the system or elsewhere .
A circuit for supplying current to and monitoring and~or receiving current from an electromagnetic actuator will briefly be explained with reference to Figure 8.
The syste!l~ comprises an electromagnetic device such as a ,~ i nF~d actuator/damper unit 310 which is normally fed with power from an energy store 311 such as a battery via a pow,~r switching device 312. In order to provide the desired motion of the unit, the power switching device 31Z is controlled by a controller 314 which pulse width modulates the supply to the actuator/damper uni-t 310. The energy store 311 can be re-charged, if appropriate, from an alternating supply via a rectif ier 315 .
The actuator/damper unit 310 and drive a~a~.-, L is, thus far, as descri~ed in our ~nternAtinn~l Patent Application WO93/01646.
When not being supplied with power to drive the unit 310, it ma~ be used to generate electrical power as a result of relative motioll of the piston and cylinder of the unit 310. This power can be fed back to the electrical store 311, if required. The controller 314 is therefore used to control a :Eurther power switch 320 for receiving current form nit 310 and feeding it via a current transformer 312 and a rectifier 322 to the store 311.
1-- 2~8237~
Although the above described system contemplates the d~mping action of the system being used to replenish an energy store for activating the actuator/damper unit, it could be used for other purposes not nPc~ss~rily connected with the actuator~damper unit 310. It is preferred to use it, however, for some immediately useful purpose associated with the damped action. In the case of an air-sprung motion base, energy recovered from the unit 310 could be used to drive a co~cpressor which charges an air reservoir, for example. An ' ~';- L of the invention will now be described with reference to Figure 7. This shows motion control apparatus according to a preferred 'i ~ of the present invention, incorporating an electromagnetic actuator which may be of any suitable type as explained earlier, but in this example is of a type with current carrying coils on the cylinder. A
computer control means supplies signals to a set of pulse-width modulating switches which control the supply oi' power to the coils in the cylinder in response to the control signals rec~ived from the computer control means. As a result of the supply of power to the coils, the piston is suojected to thrusts qenerated as a result of electromagnetic forces.
With the f eatures described aoove, the apparatus would be capable of achieving "hard"
simulation. In order to allow the apparatus to provide "soft" simulation, l:here is provided means for sensing the relative positions of points on the cylinder and piston, or other characteristics of the actuator parts, such as the relative velocity of the piston with respect to the cylinder. T~le position sensinq means provides signals indicative of, in this example, the relative positions of the piston and cylinder, to the computer control means, which may then modify or generate control signals to be sent to the switching means such that - ~ 2182372 forces with any descri~ed relatinnchip to the positional relationship may be yLuduced.
The response det~rmi ne-1 by the computer and control means may be detPrminP-I in a variety of ways.
Two simple applica~.ions of the above apparatus are as a "virtual spring", or as a "virtual damper". These illustrate manners in which the response may be decided .
To simulate a convPnti~n~l spring it is necessary for the restoring forces to be directly proportional to the piston displacement over a predetPrmi nPd distance . This is known as the characteristic of the spring, and is summarised by the equation P = -kx, where P is the restoring force, x is the displacement from a reference point, and k is the spring constant or spring rate. A chosen spring rate is thus entered by a user, and is stored as data which is supplied to the , ~Pr control means in order that a response to a sensed positional relation~hi~ may be detPrmin~-d.
Similarly, to simulate a conventional damper, it is nPCPCcAry for the restoring force ~ppncin J the motion to be proportional to the rate of change of displA~ L, i.e. ~he velocity of a moving point relative to a reference point. This may be summarised by the equation P-- -qv, where v is the velocity of the point and q is the dampinq coef f icient .
A chosen damping coefficient is thus entered by a user and is stored as data which is utilized by the computer control means in order that a response to a sensed velocity may be detPrn~i nPd .
The above two applications of the invention may be superimposed, for example, if it desired to 218237~
simulate a spring and a damper in parallel, by calculating a restoring force according to the equation .
P = - kx - qv.
The coefficients k and q may be chosen int~ n~l~ntly, and may, for example, be chosen in accordance with the dynamic mass of the object being positioned in order to achieve critical damping.
Features of actual springs which are not summarised by the principal linear relationship above include springs reaching their elastic limit and springs breaking. These features can also be imitated by a virtual spring according to an _; of the present invention. In order to simulate a spring reaching its elastic limit, the restoring force is made to become very large at a predetF-nmi n~d /1; cp~ L from a reference point, su~h that the "spring" resists any further stretching. On the other hand, in order to simulate a spring breaking, the restoring force could suddenly be reduced to zero by reducing the spring rate to zero.
It will be clear that it is possible to imitate a wide ranqe of spring or damper characteristics, including many which are unattainable with real springs alld dampers.
In some applications it would be an advantage to use the apparatus as a spring whose characteristics can ~e changed to suit with the dynamics of the load.
For example, it would be possible to tune the resonant fLeyuen y of a system whose mass is not prede~rm;n-od or is actually unknown, ~y altering the spring rate to suit. Further, if t:he mass changes in time, perhaps as a result of a controlled process, the force:distance characteristic of the actuator can also be changed in real time so as to achieve the desired resonance characteristic .
0 ~1~237~
As explained a~30ve, a particular application of an ' 'i~ L of the preferred invention is in virtual reality motion simulators. Referring again to Figures 1 and 2, a surf-board may be placed on simulator plane 40 in order to provide "virtual-reality surfi3ng".
In the absence of a user, the actuators 30 could be supplied with signals such that the simulator plane 40 imitates the motion of a surf-board under the action of waves, either when stationary or when moving across the water. The actuators could be caused to produce regular motion or a preder~rmi n~d sequence according to prede~F-nmi n~r1 algorithms, or could he caused to produce random or pseudo-ra3ldom motion within pre~i~fin~i3 limits, by the control means (see Fig. 9).
A user cli333bing on hoard, or alternatively onto the simulator plane 40 itself, would alter the condition of the acl:uators and would continue to alter this whenever he mo~ed his weight relative to the centre of gravity of the simulator plane. On detection of such changes in the cond~Ltion of the actuators, as monitored by the sensing means (see Fig. 9 ), the control signals to each actuator could be modified by ~h ingin~ the algorithms by which they are controlled, or by introducing damping co~ffi~ i~onts and spring rates, which may be time-varying, for example, as well as ~rf-~-r3 L
on further changes in the position of the user on the simulator plane . By virtue of such control, the user will feel that his own v ts are affecting the v~ L of the surf-board or simulator plane.
It will be noted that in motion contro}
systems having a pl~3rality of actuators, it may be sufficient for the control signals to the actuators to be supplied in-3.op~n~ntly, possibly by separate computer control systems, in order to cause a predet~-nminf-d sequence of moves such as, for example, to simulate the effect of waves on the surfboard described above. If, however, it is desired that the motion control apparatus is ~o superimpose "soft" simulatioll effects on the prede~Prmin-d "hard" simulation by detecting and responding to v, ~c of a user, it is generally necessary for more than one sensor to monitor ~ Ls of the user. In preferred embodiments, in which movements of the user are monitored by monitoring ef f ects on the actuators such as the generation of currents in conduct:ive loops in the cylinders of the actuators as a res~llt of relative motion between magnets mounted on the pistons and the conductive loops in the cylinders, it will generally be n~cF-s5:1ry for signals by some or all of the actuators to be monitored by a central computer me!ans in order for a realistic response to be calculated. If, for example, a user moves his weight towards one of the three actuators in the simulator shown in Figs. 1 and 2, and away from the other two actuators, the first actuator may generate a "positive error signal" while the other two generate "negative error signals". It will generally be nf'C~SSAry to compare or analyse the three signals in order to determine new control signals.
A further particular Arpl 1 cati nr~ of Ls of the present invention is in the field of ac~ive suspension for vehicles Cars and other vehicles generally are provided with a suspension system. A typical sUCp~nci~n system for a car consists of a set of Ls equivalent to a complex spring/da~mper combination, mounted between the main body of the car and the wheels. By selecting appropriate sprin~ and damper characteristics it is possible to provide a suspension system offering two particular advantages to the driver of the car. The first of these is tllat the effect of sudden jolts, such as those caused whe~l a wheel of the car encounters a bump or a hole in tlle road, may be absorbed by the 21~237~
system such as to allow the driver of the car a more comfortable ride. The second af these is that the wheels of the car may remain in contact with the road even in situations in which a car without a 5ll~p~ncinn system would temporarily lose contact with the road, such as may occur, for example, i~ one drives with excessive speed o~er a ramp. This advantage is linked to the ~irst advarLtage, and additionally allows for better road-holding, leading to more effective steerlng and ~reaking, and to decrease wear and tear of the vehicle in general.
~ nown types of sllcp~ncinn systems for cars and other vehicles include - - nir~l, hydraulic and p~eumatic sllcpPncinn systems.
It is gen¢rally possible to ad~ust the spring and damper characteristic of suspension systems of vehicles. It may be n~ceas~ry to stop the car in order to allow such adj~i c to be ~ade, but it is possible to ad~ust the sllcpPncinn characteristics of some cars, and in particular those for use in motor-racing, hy means of controls within the car while the car is in motion. It is thu~ possible to adjust the firmness of the 51lcponc i nr~ in (~c~coLddnce with rhAn~Ji n~ road conditions, such a~ to allow the car to be approximately "critically dampedl' as it passes over varying terrain.
More recently, and in particular in the field o~ motor-racing, a type of 5llcp~n~inr~ known as "active S" r~ncinn" has be~ developed With active Sl-cr~ncinn, the spring and daml~er characteri_tic5 of the 5l-cp~-ncinn system are ad}usted ~ icllly in L~ ",6e to detected changes ill driving conditions, such as changes i~ steering, tiltillg of the car due to irr~gular or cambered road surfaces, changes in the distribution and/or amount of mass being carrled by the car, and other changes. A t:ypical aim of all active s--c~.-ncinn system i5 to alter the spring and damper characteristiC
.
0 ~2372 C~ fln~ ly as t~le Yehicle moves over a surface haviAg a~ variety of irre~3ularities, such a~ to in~Ain the system iA a condi1:ion of critical damping, the spring aQd damper charact:eristics beiAg set aAd altered in L~ 0118_ to dc L~_ L.e1 changes iA driviQg conditions, without the need for the driver to provide direct ~ '- to the suspension system. Known active sllqp~n~ n systems iA motor-racing geAerally utilize a hydr~7 ir~lly damped suspeAsion system iQ which the hydraulic pressure or the volume cf water in the system is alter~di as a result of the detection of changes in driving conditioAs. Such changes may be detected by means of straiA gauge3 attached to the wheel support structure, or otherwise.
ReferriA~ now to Figure I0, a S--~r--nci~n system of a car iq shown in dia~ ic form. The diagra~ ir~lr~tos a front view of a car, and illustrates OAly those features of relevaQce to an 09rl.-n-l ~nn of aA
active sll~pencirn ~ystem.
The car }~ody indicated by box 60 is liAlced to a steering box 70 by steeriAg colu~Q 65, which ,~ i r~tes steeri Ag '~ provided to it by a steering control means 62 to the s1:eeriAg box 70. These m~ly be el~!ctronic, --lir-l, hydraulic or p tr 9ignals, or may be other typ~s of signals.
Tl~ steeri7~g box 7CI is liA~ced to the front wheels 80 by au~-.rLs 75 via axle~ 78, the ,u~po, Ls being movable in to steeriDg - suc7~ as to alter the axis of rotation of the wheels and thu~s to chaQge the direction of the car. 8etween the body of the car 60 Qd the wheel suppcrts 75 are s~qr~"Qir~ system~ a5, shown iQ this diagram a~ piston aQd cyliQder syst~ms.
The suspeAsion systems 85 are shown a boiAg controlled by S-l~ponqi~n coAtrol systems 82. The S17qponq jnn control systems 82 need not be withiA the car body 60.
Further there may be a single suspension control system 82 controlling all of the Sllcppncit~n systems, or there may be a suspension control system for each sllcpPncil n system or for each pair of suspension systems, for example. Sensors of a variety of types, such as strain gauges, may be mounted within the support structures 75 or elsewhere in order to detect changes in driving conditions such as irregularities in the road surface 95. In the diagram, these sensors are indicated as strain gauges 76 mounted on a leaf spring 77, the strain gauges being connected electrically to the S-lcp~ncinn contrDl means 82 by connection means which are not shown .
The suspension systems 85 may initially be controlled to act as spring/damper combinations having predetenni nP~l spring/damper characteristics that approximate to, for example critical damping for the car moving at an averagi speed over an averagely bumpy road while carrying an average load. The spring/damper characteristics may be adjusted such as to provide critical damping under changed conditions by providing different signals from the suspension control systems 82, which may be hydraulic signals if the suspension systems are hydraulic. In order for the sucppncinn to be considered "active suspension" however, the suspension systems 85 must be controlled in a manner de~Pnmin~d at least partially from the results of the detection of a characteristic of the driving conditions, such as for example, irregularities in the surface over which the wheels are travelling, or changes in the steering direction of the wheels. The control of the suspension systems 8~ may be the alteration of the damping factor, whic,~ may ~e done for example at regular intervals, or wherever a change above a threshold level is detected, or continuously. Alternatively the control may be of the length of the piston and cylinder 21~2372 assembly. With control of this type, it may be possible to maintain the car body at a prede~F~rmi n~ absolute height irrespective of any holes or bumps ~nrollnrpred by the wheels 80 by adjusting the length between the car body 60 and the support stLU-.:LULt:s 75 in response to the estimated size of each irregularity.
Other types of control, with alternative aims, utilizing the concept of monitoring driving conditions and controlling the suspension system accordingly, will be apparent.
The applicability of the present invention to the field of suspension systems alld to active 5llcpf~ncion systems in particular, stems in part from the speed and accuracy with which electromagnetic rams may be controlled. It also stems in part from the fact that suitably constructed actuators, preferably electromagnetic, may serve not only as force ~ eL~, but also as sensors of their own motion as a result of other forces.
Referring again to Figure 10, if each suspension system 85 contains an elect~, , Lic ram, the support structures 75 or the wheels 80 are rnn~ red to be on a notional "ground level", and the car body 60 is cnnqi~i~red to be the member whose motion it is intended to control. It will be noted that in contrast to the field of motion simulation, in which the int~nticn is to cause a member to move in relation to a stably mounted groun~ plane, in the field of active s--cp~nci nn it is gen~erally intended to decrease the motion of a member such as a car body in spite of the motion of a ground plane such as a wheel or support structure, caused fo!r example by a wheel rolling over a hole or a bump in the road.
Utili2ing suitably constructed electromagnetic actuators in the suspension systems 85, characteristics of the relative motion between the car body 60 and the support structures 75 may be monitored by detecting i~ 2~g23~ ?
currents generated in the electromagnetic: ~ of the pistons or cylinders of the electromagnetics rams.
Signals indicative of those generated currents may then l~e 'supplied (by connection means not shown in ~igure 10 ) to the suspension control means 82 which are thus able to alter the spring and damper characteristics or other characteristics of the suspension systems 75 in accordance with predet~nmi n~d functions of the slgnals or in accordance with other data ~p~n~ nt on the conditions of the electromagnetic rams. It is thus possible to dispense with the i n~iop~n~ nr sensor systems 76, 77 while still allowing for sufficient monitoring of driving conditions to enable active suspension to be provided. In fact, by monitoring the signals from the electromagnetic rams instead of those from; nA-~p~n~l~nt sensors, it is genel-ally possible to monitor characteristics more directly indicative of relative motion between the car body 60 and the wheels 80 or support structures 75, and thus to ~onitor relevant characteristics of driving conditions more directly. It is thus preferab}e that the "error signals" are produced by the actuators themselves in this manner, but it is envisaged that the ~rror signals may be produced to other ways according to other ' ~i Ls of the invention .
In addition to the f ields of motion simulation and suspension systems, it is envisaged that; ' 'i Ls of the present invention will have applications in many otl1er fields. U~ 7ing the particular advantages of electromagnetic actuators over most types of force generator it is fore~eeable that ' _ 'i Ls of the present invention will have applications, in particular, in situations in which people and objects must be moved, or stAhi 1 i 7~ despite v~-- L of their support, wherein the control of motioll depends in some way on the detection of characteristics within or outside the 2~8237~
system. For example, if electromagnetic rams are used as the force-generators in elevators, characteristics such as changes in the total weight of the p~qs~n1~rs in the lift as people enter and exit the lift could be monitored, thus allowing the control signals to the rams to be altered according to such changes. Transport of delicate objects which may be damaged by jolts may be effected very smoothly by use of suitably controlled electromagnetic rams.
The particular adYantages of electromagnetic actuators have been explained above. These stem in particular from the feature that in addition to being able to produce thrusts when energized by a suitable electrical signal, they are also able to produce electrical signals directly when sub~ected to forces which cause relative motion between the - c of the actuator. r -'i Ls of the present invention are not limited to those utilizing electromagnetic actuators, however. Other types of actuators, such as for example ball-screw actuators may be used, having means within or thereon with which to monitor characteristics of the relative positions or ~,~ Ls of the member and the ground level, or the forces between the ground level, the actuator and the member, in order to obtain slgnals from whicll to estimate or calculate ~ Ls, or changes in the forces applied to the system. It is foreseeable that sensors able to monitor forces, i n~l~pen~ntly of monitoring any relative motion between the actuator ~ ~ Ls, may be used.
- The present invention relate~ to an apparatus for controlling the motion of an object. In particular it relates to motion control apparatus wherein forces are generated by actuators such as electromagnetic actuators having a piston and a cylinder and in which relative motion is caused to happen between the piston and the cylinder by means of electromagnetic force.
Examples of such electromagnetic rams are disclosed in International Patent Application No. PCT/GB92/01277, published as WO 93/016J.6.
The present invention also relates to a corresponding method for controlling the motion of an object or objects by means actuators such as for example, electromagnetic actuators.
The present invention has applications in the field of motion simulation. Motion simulators are now used in, for example, flight simulators for training pilots, an~ in arcade games based on activities such as motor-cycle racing. In these examples, motion simulation is generally f-nh~nred by the provision of audio visual signals to the user ir. order to make the experience of actual motion seem more realistic. Such motion simulators are now known to the general public as "virtual reality" ~--hin~c and are becoming more widely available for recreational and educational uses. In general motion simulators are known which utilize hydraulic or pneumatic rams as the actuators providing the n~ress~ry forc~s to move a user who may be in a simulator cabin or on a simulator plane. More recently it has been proposed by the inventor of the present application to utilize ele~L~ ~ gn~tic actuators as the thrust producers in motion simulation devices ~see, for example, International Application PCT/GB92/01279, published as Wo 93/01577 ) .
. ~ 2182372 It is knl~wn for motion simulators, comprising a set of actuators arranged between a base plane and a simulator plane or cabin, to provide motion simulation according to a predetPnmi ned program, wherein each actuator operates according to predetPnmi nPd time pPn~lPnt functions or to stored data in order to cause a sequence of thrusts or moves to be applied to a simulator cabin or simulator plane. In this way a user on the simulator plane may experie~ce a "virtual reality ride" around a well-known motor racing circuit or down a well-known t~hqgg~ll run, for example. Such simulators may be said to pro~ide "hard" simulation of a predetPnrni nPd experience in the sense that the actuators apply set sPtIupn~-pq of thrusts or moves to the simulator plane or cabin irrespective of ally action on the part of a user in a cabin or on a simulator plane. It is also known for a user, or an externaL controller, to be able to control the thrusts to be applied to the cabin or simulator plane, by operation of, for exa~ple a steering wheel or a joy-stick control system. Such simulators are able to provide si 1;~ n of a non-predetprmi npd experience, but may still be said to be providing "hard"
simulation since tlle motion or thrusts applied to the cabin or simulator plane are still detPrminP~, albeit contemporaneously, by a computer contro1 ~ni 1'."
responsive only to external ~ '-.
A particular example of motion simulator employing a combination of the above two types of "hard"
simulation would be a flight simulator in which a user in a cabin, the inside of which is intended to look and feel like a cock pit, controls an "aeroplane" by operating controls similar to those of a real aircraft.
Signals from these controls are processe~ and applied to a set of actuators arranged to change the position and orientation of the cock pit in order that the user experiences the ef Fects of his own control of the plane 0 ~182372 until such time as his actions, if carried out in an aeroplane, would have resulted in an unrecoverable crash. At such a time as this, the control of the actuators may be ta~ken completely away from the user and instead, the actuators may be controlled to simulate a crash by running a predetPrr~i nPd sequence of moves .
Irrespective of whether the f light simulator according to this example is in the first mode ~i.e. under the user's control), or in the second mode ~i.e. performing the predetPrminpd "crash" routine), the simulation may be said to be "hard" on account of the fact that the actuators are only responsive to externally driven It is desired to provide motion simulators in which signals provided to an actuator or to a set of actuators are detPrminPd not only from external .ic but also, for example, from L..~v~ L of a user in a cabin or on a simulator plane. Signals determined as a result of v L of the user may thus be provided to the actuators in acdition to a predet~rmi nP-i sequence of signals such that the user feels that his changes in position are affecting the motion of the object whose motion is being simulated. For example in a simulator for simulating surfing on the sea, wherein a surf-board is placed on a simollator plane, the actuators may be provided with signals such that the simulator plane moves as if under the action of waves, and in addition to this, they may be provided with additional signals if a "surfer" on the surf-board shifts his weight relative to the surf-board, such that the motion of the surf-board is affected by the v~ Ls of the surfer. Such simulation may be referred to as "soft" simulation.
According to the present invention there is provided apparatus for controlling the motion of a member, comprising an actuator disposed between the member and a ground level, and a control aLLa~ L
0 2182~72 for providing control signals to the actuator whereby to cause the actu~tor to generate thrust, characterised in that said apparatus further comprises means for monitoring cha:racteristics of the relative positions or movements of tlle member and the ground level or the forces between ground level, actuator and member, and providing signals indicative of said characteristics, and in that the control arrangement is responsive to signals provided by the monitoring means and comprises means for modi~ying or generating the control signals to be provided to the actuator.
Preferred 'i Ls of the invention utilize electromagnetic actuators and make use of the feature of these that in ~ddition to converting electrical signals to thrust, they may produce electrical signals directly as a result of force being applied to them.
In the field of motion simulation outlined above, apparatus according to an : ' of the present invention in general comprises a plurality of actuators disposed between a plane resting on the ground and an object on which a user may "ride". The object on which the user rides may be located on a plane which is attnched to the actuators, or may be attached to the actuators itself.
In order for motion simulation to be "soft" it is generally necessary for the apparatus to include means for monitoring characteristics of the position or v~ of the member of a user on the member, although it may be necessary also to monitor ~uLL-7~ i characteristics of the ground plane in some circumstances . In motion simul2tors ~ i ng a preferred: ' i L of the apparatus according to the present invention, use is preferably made of the fact that currents are generated in the coils of an electromagnetic actuator when there is relative movement between the pis~on and the cylinder, and by monitoring these currents, the extension or reduction of the actuators as a ~esult of ~c L of the user may be monitored without the need for further connections or sensors to be mounted on the actuators. Alternatively, however movemenl:s of the user may be detected by 1~ 218237~
monitoring other characteristics, such as the angles between the actuators, the lengths of the actuators, or the rate of change of extension or reduction of the length of the actuators. Also, .~ Ls of the user may be detected more directly by attaching .c sensors of any convenient type to the user or to the member, or by any other convenient means.
Signals indicative of characteristics of the position of movement of the member, having been obtained by any chosen form of monitoring means, may be processed by computer contro l means such as to provide contro l signals to the actuator which are the sole control signals to the act~ators. AlternatiYely, a predetPrminPri sequence of control signals may be modified as a result of signals received from the monitoring means in order to "superimpose" the effects of a users I ~, Ls on a prede~Prmi nPd ride. In either such situation, the simulated motion may be said to be "soft" .
As PYrl iinP~ above, motion simulators Utili71ng -j ts of the present invention generally include more than one electL, - ~ic ram, and may also include other support means such as air springs. It is not, however, nPcPqs~ry for there to be a plurality of actuators, and a f~rther application of -'i Ls of the present invention, in which a single actuator may suffice, will be ou~tlined below.
It is well known that spring systems and spring damper combinations can be modelled by computer and that ideal spring and/or damper systems can be designed in this w~y. However, when putting such computer modelling into practice it is often the case that design, ~ , i CP9 have to be made. In the past, spring and damper combinations have been adjustable to the extent that th~ damper characteristics may be switched but again these are very crude systems when ~182372 comp~red with the comput~r modelling which is possible.
The adv~nt of electromagnetic piston and cylinder devices capable oE producing high thrusts has allowed designers to produce any desir~d thrust characteristic prof i le .
~ le now propose utilizing the controllable aspect of a~ elec~romagnetic piston and cylinder device to drive the pistcn forwards and backwards at rates det~rrni n~d by the designer and between limit positions also det~rmi n~ b~y the designer in order to simulate a specific spring o~- combination of springs or in:~t1~n of springs and daupers. The advantage of using an ~lectromagnetic r~lm system is that because the switching of the coils whic}l causes the relative ~ b~twee~
the pisto~ and cylinder i already under computer control, it is possible to feed new pL~L~ to the ~ r which wi:Ll 71ter the characteristics of the piston and cylind~r device.
Piston and cylinder actuators controlled according to some: i ~5 of the present invention as set out above uay be made to act as "virtual springs", "virtua3. dampers " or "virtual spring/damper ' inA1 l~n~ ti~li7ing terminology used in the field of "virtual reality". A particular application of such ~ is in the field of suspension systems, such a~ active s~Cp~n~L~n systems for vehicles. As explained above, an ele_Ll, Lic actuator controlled according to ~ '' ~ of the precent invention may be controlled such t}lat it acts as a sprinq or a combination of splings, a damper or a - inAtinn of dampers, or a, inJ-rir~n of spri~gs and damperY. In s~Cponci~n systems, the aim of controlling the motion may be thought of as the reverse of that Ln motion simulatlon, since it is generally desired to allow a user a smooth a ride as possible in, for example, situations whe~eill a vehicle is travelling over ` 218237~
irregular terrain. The monitorinq of v L is thus principally directed to that of a base plane or a set of wheels, which may be considered to travel across the "ground level", but monitoring means similar to those described in relation to motion simulators may be used.
Other applications of the present invention will become appare~t from a full description of Ls of the invention.
r ~ rlts of the prese~t invention will now be described with reference to the Ar- -nying figures in which:
Figure 1 shows in diagrammatical form a motion simulator of a kno~n type which may be controlled according to an: 'i L of the present invention;
Figure 2 shows a perspective view of a simulator Pni~-" such as that shown in Fig. l;
Figure 3 shows the two principal parts of an electromagnetic actuator;
Figure 4 shows a piston suitable for use in an alternative type of electromagnetic actuator;
Figures 5, 6 and 7 show alternative arr In; c of an electromagnetiC actuator;
Flgure 8 shows a circuit for supplying current to, and receiving current from, an electromagnetic actuator;
Figure 9 shows, in diagrammatical form, an -~i L of a motion control apparatus accordin~ to the present invention;
Figure 10 shows, in diagrammatical form, an active suspension system of a car, controlled according to an 'i L of the present invention;
Referring to Figure 1, there is shown in diagrammatical form a motion simulator to which an _'i L of the motion control apparatus of the present invention may be applied. A motion simulator of this type, but for "hard" simulation was the subject ~182372 of In~rnA~ nA1 Publication W094/10665, filed by the applicant of the present application, the subject matter of which is incorporated herein by reference.
As shown, there is a base plane 10, which may rest on a floor or be otherwise stably supported, and a simulator plane 40 on which may be mounted a capsule motor-cycle, or surf-~oard, for example, (not shown) that is to undergo simulated motion. The capsule may represent a cabin, such as an aircraft cabin, in which a user would stay during use in order to be subjected to v~ L .
On the base plane 10 are mounted three actuators 30 which are linearly ~yt~nrlihle elect-, ~..e~ic ra~,s. ~iote that although no connections to the actuators 3a are shown in Figure l, connections would in general be required for electrical power and signals, and possikly for fluid, as will be r~ lAin~d later. The actuators are mounted in such a way that each is free to rotate in direction A with one deqree of freedom about a point 24 on the base plane 10. For example, the actuators 30 may be mounted by means of hinges 26 whose axes each lie in the base plane 10. In general, the axes about which the acLue-Lu~ . are free to rotate ( in the example, the axes of the hinges ) can be extended so as to intersect with each other at points forming a notional triangle 20 with sides 22 on the base plane 10. This notional triangle 20 is in this 'i L an equilateral triangle. The axes of the actuators 30 intersect with the axes about which they are free to rotate at points 24 which are midpoints of the sides 22 of the triangle 20 on the base plane 10.
These points 24 can be thought of as the coupling points of the actuators 30. In this example, each coupling point 24 is the midpoint of one of the sides 22 of the triangle 20. They thus form a smaller triangle within the triangle 20. On account of this, the axes of the 2~2372 _ 9 _ actuators 30 diverge from points on a common line irrespective of their angular positions, this line preferably being the line perpPnAic~ r to the base plane, passing through the centroid of one or both of the triangles.
Each act~lator 3 0 may be extended or shortened in directions B by a length up to that of piston 32 which in general has a length less than or equal to the length of the actuator, bu~ may be longer if it is extendible in stages, with for example a telescopic action or if the cylinder is open-ended and the piston is allowed to move through it. The piston 32 may be supported by a slide bearing 38, to further strengthen the structure of the simulation ;~ni cn- The pistons 32 of the actuators 30 are each ~oined to a point of the simulator plane 40 by means of a uniYersal bearing 36, the three bearings forming a notional triangle 50. This notional triangle S 0 is in this case an equilateral triangle and is in the simulator plane 40. The two notional triangles 20 and 50 may be of a similar size or of different slzes, ~PpPnriing on the required extent of the motion and the stability required. Generally however the centre of mass of the capsule should be aboYe the centroid of the triangle 50. In addition, the centre of mass of the capsule should be kept, to a required level of accuracy, above the centroid of the -points at which the actuators are coupled to the base plane. This condition may be maintained by suitable choices of sizes a~d positions of the triangles 20 and 50, lengths of the actuators 30 and/or external control of the types of v~ Ls that are caused by PYtF~n~linq and shortening the actuators. (This external control may be by physically preventing the actuators from reaching angles outside a required range, or by computer control of the lengths of the actuators according to prP~Pt~rminpr1 algorithms or contemporaneous 1-- 2~82372 calculations. ) The coupling points of the actuators 30 to the triangle 20 on the base plane 10 should thus be separated sufficielltly from each ol;her for the triangle 20 to be sufficiently large to provide a means of transferring the forces produced by the actuators to the stable base plane 10.
Referring to Figure 2, there is shown a perspective view o~ a simulator -- ~ni ~m such as that shown diagrammatically in Figure 1.
Prior to explaining how a simulator ;Ini~
such as that shown in Figs. 1 and 2 may be controlled according to the present invention, some types of electromagnetic actuator suitable for use in such a -hlni~ Will be clescribed with reference to Figures 3, 4, 5 and 6. Such ~.ctuators are the subject of International Publi.cation WO 93/01646, filed by the applicant of the present invention, the subject matter of which is incorporated herein by reference.
Referring to Figure 3, there are shown the two principal parts of an electromagnetic actuator, which are, respectively, the cylinder 130 and the piston 135.
In this example, the cylinder 130 houses a plurality of annular coils 131 which are separated from each other by pole-piece rings 132. The piston 135 is of a suitable size to slide within the central bore of the cylinder 130, and comprises a cylindrical steel sleeve 136 on the exterior of which are mounted a plurality of segme~ted windings 137. Currents in the coils 131 on the cylinder may be proYided such that radial magnetic fields are produced which interact with currents in the piston coils 137, whose phase is controlled according to the position of the piston and the required thrust direction. Alternatively, currents flowing in the piston coils 137 may produce radial magnetic fields which interact with ~ILL~IlLS in the cylinder windings 131. A piston for an actuator such as this is shown in 237~
Fig. 4, in which the piston comprises a steel core 140 provided with annular pole-pieces 141 and coils 142.
Alternative actuator arrA~ are possible. Two further examples are shown in Figs. S and 6. In Fig. 5, there is shown, al~ actuator wherein a cylinder 191 carries a plurality oE annular coils 192, and wherein a piston 190 carries radially magnetised ring-magnets 193. By applying suitable currents to the coils 192, the pisl:on 190 may be made to experience an electromagnetic fo3 ce such as to extend or shorten the actuator. In Fig. 6, however, the steel cylinder 201 carries a series 03f ring magnets 202 which are radially magnetised, while the piston 20~ carries segmented coils 204, to which current may be applied to cause electromagnetic force to be generated such as to extend or shorten the actwator.
As is evident from the above electromagnetic actuators for use in ~ -'i Ls of the present invention may be 03- a variety of types, providing it is possible to energise coils in either the piston or the cylinder such as to generate electromagnetic forces between the coils ~nd a magnetic system in the other one of the piston and the cylinder. The ~--gnPri, system may be a single p~3~-n~nt magnet, a series of p~r~-n,-nt magnets, or one or more current-carrying coils.
While th~ principal function of the electromagnetic actuators is to produce thrusts, it is advantageous in embodiments of the present invention if the actuators are adapted to perform the reverse operation, this being the generation of currents in coils in either the piston or cylinder as a result of relative motion between the piston and the cylinder. ~y virtue of this it is possible to detect slight changes in the positional relatic~nchip of the piston and the cylinder by monitoring currents in the coils. It is further possible to utilize the currents in the coils to , ~ ~lg2372 recharge a battery, for example or to provide power for use in the apparatus.
A further type of electromagnetic actuator which is suitable for use in 'l Ls of the present i~Lvention, will briefly be described with reference to Figure 7. A full description of the unit, and in particular its electromagnetic properties will not be given as the basic unit may be o~ any of the types referred to earlieJ~ or referred in our International Patent Application W093/01646, or otherwise. In this example, however t~1e principal features of the electL - ~ic r~l include a cyli~der 230 having stator coils 231, and pis1:on 232 having p~ n~nt magnets 233, 234 mounted thereoll. Additionally, the stator i nrl conductive rings 2:15 at either end of the stator which may be made of cop~er or ;,1 'ni for example, and act electrical c~ch~nn~ to pr~vent violent impact by the piston at th~ extremes of L,~ L~
The above! description refers pr;nrirJl Iy to electromaLg~Letic ac~.uators 11~Lving a piston and a cylinder, ho~ever in certain applications of the invention it may be~ advantageous to utilize other types of actuators, such as rotary torque a- LuaL~ s. rt is thu$ not i n~on~lod that this inve~Ltion is limited to ~y~tem~ in which piston and cylinder a~ LuaLora are or sy~tem~ in whic~ the actuators are el~_L. ic.
In general, it is rL~c~c~-ry for an elccLL -~ic ra~L to hav~ means to allow fluid to pass out from the inside of the cylinder a~ it isl _ _~sed by the ~. of the piston. In this example, ports ar~ irLdicated as being connected to an air reservoir which also in v.~o.~Les a~L air-pump. This may be used to assist the elect~, Lic ram i~L providing large thrusts, or by controlling the f luid pL~3~ to a required level, it may be possible for a load to be supported completely by fluid pressure, until such ti~Le as the loa~ changes or moves. once such a chan~e alters ~ 2372 the pressure from the load on the piston, the piston will move due to the pressure in the piston from the air reservoir/pump and due to the effect described above in which relative motion of the piston and cylinder will generate an electr~ ~nf~tc current, it will be possible to detect the ~ v~ .L of the piston by virtue of the monitoring of the detected currents, and it is also envisaged that the currents generated by such relative motion may be used to supply power to the system, or may be stored f or use in the system or elsewhere .
A circuit for supplying current to and monitoring and~or receiving current from an electromagnetic actuator will briefly be explained with reference to Figure 8.
The syste!l~ comprises an electromagnetic device such as a ,~ i nF~d actuator/damper unit 310 which is normally fed with power from an energy store 311 such as a battery via a pow,~r switching device 312. In order to provide the desired motion of the unit, the power switching device 31Z is controlled by a controller 314 which pulse width modulates the supply to the actuator/damper uni-t 310. The energy store 311 can be re-charged, if appropriate, from an alternating supply via a rectif ier 315 .
The actuator/damper unit 310 and drive a~a~.-, L is, thus far, as descri~ed in our ~nternAtinn~l Patent Application WO93/01646.
When not being supplied with power to drive the unit 310, it ma~ be used to generate electrical power as a result of relative motioll of the piston and cylinder of the unit 310. This power can be fed back to the electrical store 311, if required. The controller 314 is therefore used to control a :Eurther power switch 320 for receiving current form nit 310 and feeding it via a current transformer 312 and a rectifier 322 to the store 311.
1-- 2~8237~
Although the above described system contemplates the d~mping action of the system being used to replenish an energy store for activating the actuator/damper unit, it could be used for other purposes not nPc~ss~rily connected with the actuator~damper unit 310. It is preferred to use it, however, for some immediately useful purpose associated with the damped action. In the case of an air-sprung motion base, energy recovered from the unit 310 could be used to drive a co~cpressor which charges an air reservoir, for example. An ' ~';- L of the invention will now be described with reference to Figure 7. This shows motion control apparatus according to a preferred 'i ~ of the present invention, incorporating an electromagnetic actuator which may be of any suitable type as explained earlier, but in this example is of a type with current carrying coils on the cylinder. A
computer control means supplies signals to a set of pulse-width modulating switches which control the supply oi' power to the coils in the cylinder in response to the control signals rec~ived from the computer control means. As a result of the supply of power to the coils, the piston is suojected to thrusts qenerated as a result of electromagnetic forces.
With the f eatures described aoove, the apparatus would be capable of achieving "hard"
simulation. In order to allow the apparatus to provide "soft" simulation, l:here is provided means for sensing the relative positions of points on the cylinder and piston, or other characteristics of the actuator parts, such as the relative velocity of the piston with respect to the cylinder. T~le position sensinq means provides signals indicative of, in this example, the relative positions of the piston and cylinder, to the computer control means, which may then modify or generate control signals to be sent to the switching means such that - ~ 2182372 forces with any descri~ed relatinnchip to the positional relationship may be yLuduced.
The response det~rmi ne-1 by the computer and control means may be detPrminP-I in a variety of ways.
Two simple applica~.ions of the above apparatus are as a "virtual spring", or as a "virtual damper". These illustrate manners in which the response may be decided .
To simulate a convPnti~n~l spring it is necessary for the restoring forces to be directly proportional to the piston displacement over a predetPrmi nPd distance . This is known as the characteristic of the spring, and is summarised by the equation P = -kx, where P is the restoring force, x is the displacement from a reference point, and k is the spring constant or spring rate. A chosen spring rate is thus entered by a user, and is stored as data which is supplied to the , ~Pr control means in order that a response to a sensed positional relation~hi~ may be detPrmin~-d.
Similarly, to simulate a conventional damper, it is nPCPCcAry for the restoring force ~ppncin J the motion to be proportional to the rate of change of displA~ L, i.e. ~he velocity of a moving point relative to a reference point. This may be summarised by the equation P-- -qv, where v is the velocity of the point and q is the dampinq coef f icient .
A chosen damping coefficient is thus entered by a user and is stored as data which is utilized by the computer control means in order that a response to a sensed velocity may be detPrn~i nPd .
The above two applications of the invention may be superimposed, for example, if it desired to 218237~
simulate a spring and a damper in parallel, by calculating a restoring force according to the equation .
P = - kx - qv.
The coefficients k and q may be chosen int~ n~l~ntly, and may, for example, be chosen in accordance with the dynamic mass of the object being positioned in order to achieve critical damping.
Features of actual springs which are not summarised by the principal linear relationship above include springs reaching their elastic limit and springs breaking. These features can also be imitated by a virtual spring according to an _; of the present invention. In order to simulate a spring reaching its elastic limit, the restoring force is made to become very large at a predetF-nmi n~d /1; cp~ L from a reference point, su~h that the "spring" resists any further stretching. On the other hand, in order to simulate a spring breaking, the restoring force could suddenly be reduced to zero by reducing the spring rate to zero.
It will be clear that it is possible to imitate a wide ranqe of spring or damper characteristics, including many which are unattainable with real springs alld dampers.
In some applications it would be an advantage to use the apparatus as a spring whose characteristics can ~e changed to suit with the dynamics of the load.
For example, it would be possible to tune the resonant fLeyuen y of a system whose mass is not prede~rm;n-od or is actually unknown, ~y altering the spring rate to suit. Further, if t:he mass changes in time, perhaps as a result of a controlled process, the force:distance characteristic of the actuator can also be changed in real time so as to achieve the desired resonance characteristic .
0 ~1~237~
As explained a~30ve, a particular application of an ' 'i~ L of the preferred invention is in virtual reality motion simulators. Referring again to Figures 1 and 2, a surf-board may be placed on simulator plane 40 in order to provide "virtual-reality surfi3ng".
In the absence of a user, the actuators 30 could be supplied with signals such that the simulator plane 40 imitates the motion of a surf-board under the action of waves, either when stationary or when moving across the water. The actuators could be caused to produce regular motion or a preder~rmi n~d sequence according to prede~F-nmi n~r1 algorithms, or could he caused to produce random or pseudo-ra3ldom motion within pre~i~fin~i3 limits, by the control means (see Fig. 9).
A user cli333bing on hoard, or alternatively onto the simulator plane 40 itself, would alter the condition of the acl:uators and would continue to alter this whenever he mo~ed his weight relative to the centre of gravity of the simulator plane. On detection of such changes in the cond~Ltion of the actuators, as monitored by the sensing means (see Fig. 9 ), the control signals to each actuator could be modified by ~h ingin~ the algorithms by which they are controlled, or by introducing damping co~ffi~ i~onts and spring rates, which may be time-varying, for example, as well as ~rf-~-r3 L
on further changes in the position of the user on the simulator plane . By virtue of such control, the user will feel that his own v ts are affecting the v~ L of the surf-board or simulator plane.
It will be noted that in motion contro}
systems having a pl~3rality of actuators, it may be sufficient for the control signals to the actuators to be supplied in-3.op~n~ntly, possibly by separate computer control systems, in order to cause a predet~-nminf-d sequence of moves such as, for example, to simulate the effect of waves on the surfboard described above. If, however, it is desired that the motion control apparatus is ~o superimpose "soft" simulatioll effects on the prede~Prmin-d "hard" simulation by detecting and responding to v, ~c of a user, it is generally necessary for more than one sensor to monitor ~ Ls of the user. In preferred embodiments, in which movements of the user are monitored by monitoring ef f ects on the actuators such as the generation of currents in conduct:ive loops in the cylinders of the actuators as a res~llt of relative motion between magnets mounted on the pistons and the conductive loops in the cylinders, it will generally be n~cF-s5:1ry for signals by some or all of the actuators to be monitored by a central computer me!ans in order for a realistic response to be calculated. If, for example, a user moves his weight towards one of the three actuators in the simulator shown in Figs. 1 and 2, and away from the other two actuators, the first actuator may generate a "positive error signal" while the other two generate "negative error signals". It will generally be nf'C~SSAry to compare or analyse the three signals in order to determine new control signals.
A further particular Arpl 1 cati nr~ of Ls of the present invention is in the field of ac~ive suspension for vehicles Cars and other vehicles generally are provided with a suspension system. A typical sUCp~nci~n system for a car consists of a set of Ls equivalent to a complex spring/da~mper combination, mounted between the main body of the car and the wheels. By selecting appropriate sprin~ and damper characteristics it is possible to provide a suspension system offering two particular advantages to the driver of the car. The first of these is tllat the effect of sudden jolts, such as those caused whe~l a wheel of the car encounters a bump or a hole in tlle road, may be absorbed by the 21~237~
system such as to allow the driver of the car a more comfortable ride. The second af these is that the wheels of the car may remain in contact with the road even in situations in which a car without a 5ll~p~ncinn system would temporarily lose contact with the road, such as may occur, for example, i~ one drives with excessive speed o~er a ramp. This advantage is linked to the ~irst advarLtage, and additionally allows for better road-holding, leading to more effective steerlng and ~reaking, and to decrease wear and tear of the vehicle in general.
~ nown types of sllcp~ncinn systems for cars and other vehicles include - - nir~l, hydraulic and p~eumatic sllcpPncinn systems.
It is gen¢rally possible to ad~ust the spring and damper characteristic of suspension systems of vehicles. It may be n~ceas~ry to stop the car in order to allow such adj~i c to be ~ade, but it is possible to ad~ust the sllcpPncinn characteristics of some cars, and in particular those for use in motor-racing, hy means of controls within the car while the car is in motion. It is thu~ possible to adjust the firmness of the 51lcponc i nr~ in (~c~coLddnce with rhAn~Ji n~ road conditions, such a~ to allow the car to be approximately "critically dampedl' as it passes over varying terrain.
More recently, and in particular in the field o~ motor-racing, a type of 5llcp~n~inr~ known as "active S" r~ncinn" has be~ developed With active Sl-cr~ncinn, the spring and daml~er characteri_tic5 of the 5l-cp~-ncinn system are ad}usted ~ icllly in L~ ",6e to detected changes ill driving conditions, such as changes i~ steering, tiltillg of the car due to irr~gular or cambered road surfaces, changes in the distribution and/or amount of mass being carrled by the car, and other changes. A t:ypical aim of all active s--c~.-ncinn system i5 to alter the spring and damper characteristiC
.
0 ~2372 C~ fln~ ly as t~le Yehicle moves over a surface haviAg a~ variety of irre~3ularities, such a~ to in~Ain the system iA a condi1:ion of critical damping, the spring aQd damper charact:eristics beiAg set aAd altered in L~ 0118_ to dc L~_ L.e1 changes iA driviQg conditions, without the need for the driver to provide direct ~ '- to the suspension system. Known active sllqp~n~ n systems iA motor-racing geAerally utilize a hydr~7 ir~lly damped suspeAsion system iQ which the hydraulic pressure or the volume cf water in the system is alter~di as a result of the detection of changes in driving conditioAs. Such changes may be detected by means of straiA gauge3 attached to the wheel support structure, or otherwise.
ReferriA~ now to Figure I0, a S--~r--nci~n system of a car iq shown in dia~ ic form. The diagra~ ir~lr~tos a front view of a car, and illustrates OAly those features of relevaQce to an 09rl.-n-l ~nn of aA
active sll~pencirn ~ystem.
The car }~ody indicated by box 60 is liAlced to a steering box 70 by steeriAg colu~Q 65, which ,~ i r~tes steeri Ag '~ provided to it by a steering control means 62 to the s1:eeriAg box 70. These m~ly be el~!ctronic, --lir-l, hydraulic or p tr 9ignals, or may be other typ~s of signals.
Tl~ steeri7~g box 7CI is liA~ced to the front wheels 80 by au~-.rLs 75 via axle~ 78, the ,u~po, Ls being movable in to steeriDg - suc7~ as to alter the axis of rotation of the wheels and thu~s to chaQge the direction of the car. 8etween the body of the car 60 Qd the wheel suppcrts 75 are s~qr~"Qir~ system~ a5, shown iQ this diagram a~ piston aQd cyliQder syst~ms.
The suspeAsion systems 85 are shown a boiAg controlled by S-l~ponqi~n coAtrol systems 82. The S17qponq jnn control systems 82 need not be withiA the car body 60.
Further there may be a single suspension control system 82 controlling all of the Sllcppncit~n systems, or there may be a suspension control system for each sllcpPncil n system or for each pair of suspension systems, for example. Sensors of a variety of types, such as strain gauges, may be mounted within the support structures 75 or elsewhere in order to detect changes in driving conditions such as irregularities in the road surface 95. In the diagram, these sensors are indicated as strain gauges 76 mounted on a leaf spring 77, the strain gauges being connected electrically to the S-lcp~ncinn contrDl means 82 by connection means which are not shown .
The suspension systems 85 may initially be controlled to act as spring/damper combinations having predetenni nP~l spring/damper characteristics that approximate to, for example critical damping for the car moving at an averagi speed over an averagely bumpy road while carrying an average load. The spring/damper characteristics may be adjusted such as to provide critical damping under changed conditions by providing different signals from the suspension control systems 82, which may be hydraulic signals if the suspension systems are hydraulic. In order for the sucppncinn to be considered "active suspension" however, the suspension systems 85 must be controlled in a manner de~Pnmin~d at least partially from the results of the detection of a characteristic of the driving conditions, such as for example, irregularities in the surface over which the wheels are travelling, or changes in the steering direction of the wheels. The control of the suspension systems 8~ may be the alteration of the damping factor, whic,~ may ~e done for example at regular intervals, or wherever a change above a threshold level is detected, or continuously. Alternatively the control may be of the length of the piston and cylinder 21~2372 assembly. With control of this type, it may be possible to maintain the car body at a prede~F~rmi n~ absolute height irrespective of any holes or bumps ~nrollnrpred by the wheels 80 by adjusting the length between the car body 60 and the support stLU-.:LULt:s 75 in response to the estimated size of each irregularity.
Other types of control, with alternative aims, utilizing the concept of monitoring driving conditions and controlling the suspension system accordingly, will be apparent.
The applicability of the present invention to the field of suspension systems alld to active 5llcpf~ncion systems in particular, stems in part from the speed and accuracy with which electromagnetic rams may be controlled. It also stems in part from the fact that suitably constructed actuators, preferably electromagnetic, may serve not only as force ~ eL~, but also as sensors of their own motion as a result of other forces.
Referring again to Figure 10, if each suspension system 85 contains an elect~, , Lic ram, the support structures 75 or the wheels 80 are rnn~ red to be on a notional "ground level", and the car body 60 is cnnqi~i~red to be the member whose motion it is intended to control. It will be noted that in contrast to the field of motion simulation, in which the int~nticn is to cause a member to move in relation to a stably mounted groun~ plane, in the field of active s--cp~nci nn it is gen~erally intended to decrease the motion of a member such as a car body in spite of the motion of a ground plane such as a wheel or support structure, caused fo!r example by a wheel rolling over a hole or a bump in the road.
Utili2ing suitably constructed electromagnetic actuators in the suspension systems 85, characteristics of the relative motion between the car body 60 and the support structures 75 may be monitored by detecting i~ 2~g23~ ?
currents generated in the electromagnetic: ~ of the pistons or cylinders of the electromagnetics rams.
Signals indicative of those generated currents may then l~e 'supplied (by connection means not shown in ~igure 10 ) to the suspension control means 82 which are thus able to alter the spring and damper characteristics or other characteristics of the suspension systems 75 in accordance with predet~nmi n~d functions of the slgnals or in accordance with other data ~p~n~ nt on the conditions of the electromagnetic rams. It is thus possible to dispense with the i n~iop~n~ nr sensor systems 76, 77 while still allowing for sufficient monitoring of driving conditions to enable active suspension to be provided. In fact, by monitoring the signals from the electromagnetic rams instead of those from; nA-~p~n~l~nt sensors, it is genel-ally possible to monitor characteristics more directly indicative of relative motion between the car body 60 and the wheels 80 or support structures 75, and thus to ~onitor relevant characteristics of driving conditions more directly. It is thus preferab}e that the "error signals" are produced by the actuators themselves in this manner, but it is envisaged that the ~rror signals may be produced to other ways according to other ' ~i Ls of the invention .
In addition to the f ields of motion simulation and suspension systems, it is envisaged that; ' 'i Ls of the present invention will have applications in many otl1er fields. U~ 7ing the particular advantages of electromagnetic actuators over most types of force generator it is fore~eeable that ' _ 'i Ls of the present invention will have applications, in particular, in situations in which people and objects must be moved, or stAhi 1 i 7~ despite v~-- L of their support, wherein the control of motioll depends in some way on the detection of characteristics within or outside the 2~8237~
system. For example, if electromagnetic rams are used as the force-generators in elevators, characteristics such as changes in the total weight of the p~qs~n1~rs in the lift as people enter and exit the lift could be monitored, thus allowing the control signals to the rams to be altered according to such changes. Transport of delicate objects which may be damaged by jolts may be effected very smoothly by use of suitably controlled electromagnetic rams.
The particular adYantages of electromagnetic actuators have been explained above. These stem in particular from the feature that in addition to being able to produce thrusts when energized by a suitable electrical signal, they are also able to produce electrical signals directly when sub~ected to forces which cause relative motion between the - c of the actuator. r -'i Ls of the present invention are not limited to those utilizing electromagnetic actuators, however. Other types of actuators, such as for example ball-screw actuators may be used, having means within or thereon with which to monitor characteristics of the relative positions or ~,~ Ls of the member and the ground level, or the forces between the ground level, the actuator and the member, in order to obtain slgnals from whicll to estimate or calculate ~ Ls, or changes in the forces applied to the system. It is foreseeable that sensors able to monitor forces, i n~l~pen~ntly of monitoring any relative motion between the actuator ~ ~ Ls, may be used.
Claims (31)
1. Apparatus for controlling the motion of a member, said apparatus comprising an actuator disposed between the member and a ground level and a control arrangement for providing signals to the actuator whereby to cause the actuator to generate thrust, characterised in that said apparatus further comprises means for monitoring characteristics of the relative positions or movements of the member and the ground level or the forces between the ground level, actuator and member, and providing signals indicative of said characteristics, and in that said control arrangement is responsive to signals provided by the monitoring means and comprises means for generating or modifying the control signals to be provided to the actuator.
2. Apparatus according to claim 1, wherein said actuator comprises a piston and a cylinder.
3. Apparatus according to claim 2, wherein said monitoring means is for monitoring characteristics of the relative positions or movements of the piston and the cylinder.
4. Apparatus according to claim 1, 2 or 3 wherein the actuator is an electromagnetic actuator.
5. Apparatus according to claim 2, 3 or 4, wherein said monitoring means is for monitoring electrical signals generated as a result of relative movement between a magnetic element mounted on the piston and an electrically conductive circuit mounted on the cylinder.
6. Apparatus according to claim 2, 3 or 4, wherein said monitoring is for monitoring electrical signals generated as a result of relative movement between a magnetic element mounted on the cylinder and an electrically conductive circuit mounted on the piston.
7. Apparatus according to claim 5 or 6, wherein said magnetic element is a permanent magnet.
8. Apparatus according to claim 5 or 6, wherein said magnetic element is an electrically conductive circuit.
9. Apparatus according to any of the preceding claims wherein said control arrangement comprises means for providing a predetermined sequence of control signals to the actuator whereby to cause the actuator to generate a predetermined sequence of thrusts.
10. Apparatus according to claim 9, wherein said control arrangement further comprises means for modifying said predetermined sequence of control signals in response to signals received from the monitoring means, whereby to modify the thrusts generated by the actuator.
11. Apparatus according to any of claims 1 to 10, wherein said control arrangement comprises means for providing control signals according to a predetermined function of the signals received from the monitoring means.
12. Apparatus according to claim 11, wherein said predetermined function is such that the control signals cause the actuator to generate thrusts which are a function of change in the relative positions of the member and the ground level.
13. Apparatus according to claim 12, wherein said predetermined function is such that the control signals cause the actuator to generate thrusts which are proportional to the relative displacement of the member and the ground level from a predetermined equilibrium displacement.
14. Apparatus according to claim 11, 12 or 13 wherein said predetermined function is such that the control signals cause the actuator to generate thrusts which are a function of the rate of change of the relative positions of the member and the ground level.
15. Apparatus according to claim 14, wherein said predetermined function is such that the control signals cause the actuator to generate thrusts which are proportional to the rate of change of the relative positions of the member and the ground level.
16. A motion control system comprising one or more actuators disposed between a ground level and a member, said motion control system comprising apparatus according to any of claims 1 to 15 for causing the or each actuator to generate thrust.
17. A motion control system according to claim 16, wherein a lower end of the or each actuator is mounted on a stable base.
18. A motion control system according to claim 17 wherein a movable surface is mounted on an upper end of the or each actuator, whereby thrusts generated by the or each actuator cause motion of the surface.
19. A motion control system according to claim 18 wherein motion of the surface causes forces to be applied to the or each actuator.
20. A motion control system according to claim 16 wherein a lower end of the or each actuator is mounted on a means for moving said system across a surface.
21. A motion control system according to claim 20 wherein forces applied to said moving means are communicated to the or each actuator.
22. A motion control system according to any of claims 16 to 21 wherein the control means is for controlling the or each actuator such as to minimize or stabilize forces applied to the member.
23 A motion control system according to any of claims 16 to 22 wherein the or each actuator is an electromagnetic actuator.
24. A motion control system according to any of claims 16 to 23, comprising a plurality of actuators, monitoring means for monitoring characteristics of position or movement of each actuator and providing signals indicative of said characteristics to a common control arrangement being responsive to said signals and having means for generating or modifying control signals to be provided to each actuator.
25. A motion control system according to any of claims 16 to 24 wherein said control arrangement comprises means for providing a predetermined sequence of control signals to the or each actuator.
26. A motion control system according to any of claims 16 to 25 wherein said control arrangement comprises means for providing control signals to the or each actuator in response to signals received from an external control means.
27. A motion control system according to any of claims 16 to 26 wherein said control arrangement comprises means for providing random or pseudo-random control signals to the or each actuator.
28. A motion control system according to claims 25, 26 or 27 wherein said control means further comprises means for altering said control signals in response to signals received from said monitoring means.
29. A suspension system comprising a motion control system according to any of claims 16 to 24.
30. A method of controlling the thrust generated by an actuator disposed between two members comprising steps of monitoring characteristics of the relative positions or movements of the members, or of the forces between the members, and providing signals indicative of said characteristics to a control means, whereby said control means generates or modifies control signals in response to signals from the monitoring means and supplies said control signals to said actuator, said actuator generating thrust in accordance with said control signals.
31. A method according to claim 30 wherein said actuator is an electromagnetic actuator.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB939325234A GB9325234D0 (en) | 1993-12-09 | 1993-12-09 | Controlling an electromagnetic ram |
| GB9325234.4 | 1993-12-09 | ||
| GB9400303.5 | 1994-01-10 | ||
| GB9400303A GB9400303D0 (en) | 1994-01-10 | 1994-01-10 | Responsive motion base/platform |
| GB9411152A GB9411152D0 (en) | 1994-06-03 | 1994-06-03 | Electromagnetic motion system |
| GB9411152.3 | 1994-06-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2182372A1 true CA2182372A1 (en) | 1995-06-15 |
Family
ID=27266973
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2182372 Abandoned CA2182372A1 (en) | 1993-12-09 | 1994-12-09 | Motion control systems |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0733253A1 (en) |
| JP (1) | JPH10501897A (en) |
| AU (1) | AU1196395A (en) |
| CA (1) | CA2182372A1 (en) |
| WO (1) | WO1995016253A1 (en) |
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| AUPN613095A0 (en) * | 1995-10-20 | 1995-11-16 | Simtech Australia Pty Ltd | Simulator assembly |
| AUPN613295A0 (en) * | 1995-10-20 | 1995-11-16 | Simtech Australia Pty Ltd | System & method for controlling a simulator assembly |
| GR1002953B (en) * | 1997-06-17 | 1998-08-07 | Virtual reality simulator for educational and entertainment purposes | |
| DE19901570C2 (en) * | 1999-01-16 | 2000-08-03 | Johannes Kotschner | Movement device for a driving or flight simulator |
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| GB2480098A (en) * | 2010-05-07 | 2011-11-09 | Paul Hughes | Flight simulator motion platform |
| DE102011109786B4 (en) | 2011-08-08 | 2014-01-23 | Festo Ag & Co. Kg | driving device |
| FR2995561B1 (en) * | 2012-09-18 | 2015-06-05 | Soben | SUSPENSION DEVICE WITH INTEGRATED ELECTROMAGNETIC ENERGY RECOVERY DEVICE |
| GB2509053B (en) | 2012-12-06 | 2018-02-07 | Williams Grand Prix Engineering Ltd | Motion control apparatus |
| JP6035590B2 (en) | 2014-05-27 | 2016-11-30 | 株式会社国際電気通信基礎技術研究所 | Actuator device, humanoid robot and power assist device |
| KR102053898B1 (en) * | 2017-11-23 | 2019-12-09 | (주)에이스카이 | Surfing Simulator and Surfing Training Method Using the Same |
| CN109745664B (en) * | 2019-02-26 | 2020-11-06 | 浙江师范大学 | Running machine |
| CN110975255A (en) * | 2019-11-28 | 2020-04-10 | 北京小米移动软件有限公司 | Surfing simulation device and surfing simulation method |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4892328A (en) * | 1988-05-27 | 1990-01-09 | Aura Systems, Inc. | Electromagnetic strut assembly |
| US4969662A (en) * | 1989-06-08 | 1990-11-13 | Aura Systems, Inc. | Active damping system for an automobile suspension |
| US4981309A (en) * | 1989-08-31 | 1991-01-01 | Bose Corporation | Electromechanical transducing along a path |
| US5028073A (en) * | 1990-01-08 | 1991-07-02 | General Electric Company | Dynamic vehicle suspension system including electronically commutated motor |
| US5605462A (en) * | 1991-07-12 | 1997-02-25 | Denne Developments Ltd. | Motion imparting apparatus |
| JPH0565007A (en) * | 1991-09-09 | 1993-03-19 | Nissan Motor Co Ltd | Active suspension |
| ATE167945T1 (en) * | 1992-08-21 | 1998-07-15 | Denne Dev Ltd | PRESSURE CUSHION SYSTEMS |
-
1994
- 1994-12-09 EP EP95902873A patent/EP0733253A1/en not_active Withdrawn
- 1994-12-09 JP JP7516051A patent/JPH10501897A/en active Pending
- 1994-12-09 WO PCT/GB1994/002697 patent/WO1995016253A1/en not_active Application Discontinuation
- 1994-12-09 CA CA 2182372 patent/CA2182372A1/en not_active Abandoned
- 1994-12-09 AU AU11963/95A patent/AU1196395A/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| WO1995016253A1 (en) | 1995-06-15 |
| EP0733253A1 (en) | 1996-09-25 |
| AU1196395A (en) | 1995-06-27 |
| JPH10501897A (en) | 1998-02-17 |
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