MXPA00002689A - Motion-imparting apparatus - Google Patents

Abstract

Apparatus for imparting motion to a load comprises means (25) for applying a force to the load and a compliant support (27) for the load, in which there are provided means (9, 10, 11) for effecting dynamic variation of the compliance of the support during operation of the apparatus so as to optimise the power efficiency. The apparatus may be capable of controlling relative motion in a plurality of degrees of freedom between a platform (42) and a reference plane (41) the compliant means (27) acting to support the weight of the platform, and the force-applying means (25) being one or more actuators for applying perturbing forces between the platform and the reference plane. Control means (11, 12) act to control the or each actuator (43) to move in one direction or the other whereby to displace the platform (42) with respect to the reference plane (41). At least part of the compliant support (27) may be a gas spring and in one embodiment this is in the form of a bellows (45) supporting the platform.

Description

IMPROVED APPARATUS FOR THE IMPARTITION OF MOVEMENT Description of the invention The present invention relates to an apparatus for imparting movement, of a type capable of imparting movement to a load for purposes of placing it or for purposes of controlling or modifying its movement. The present invention finds applications in a wide range of devices including, for example, placement devices for manufacturing machinery. In general, such machinery does not require the device to perform mechanical work on a material (for example to cut it or to deform it) but rather to control the position of a mass moving on a low friction bearing system. Such machines are frequently required to carry out a precisely defined positioning action, at a high repetition rate and with negligible error incidence. In such a machine the use of an electromagnetic stem has advantages over other types of actuator since it is intrinsically simple in its construction, and has a mismatch or zero clearance and has a zero delay in the control conveyance. These valuable properties allow an electromagnetic actuator to produce rapid movement with extreme precision and reliability. It is possible to apply forces of more than 20 tons to be applied at several meters per second with a placement precision of a few micrometers. Such an apparatus is also used, for example, in simulators for training or entertainment. Typically, in such use a platform is moved relative to a static structure in order to create continuous movement sensations for the human occupants of a capsule attached to the mobile platform. Such mechanisms are also used in the testing of suspension systems and stabilization devices, where a movement platform is used to create calibrated disturbance accelerations, against which the operation of the stabilization mechanism will be tested. The mobile platform of the motion imparting apparatus is normally driven by an array of drive units or "rods" that can be driven by hydraulic fluid or gas under pressure, or by rod-like devices that are electronically operated by means of a nut mechanism of ball and screw. More recently, an apparatus has been designed to use a crank with speed reducer, adjusted to a rotary motor, or to employ the direct electromagnetic interaction between a piston, mobile armature, and a cylindrical stator. In the case of the electrical and electromagnetic machines mentioned, there is a requirement for the movement imparting apparatus to be supported against the gravitational forces acting on the capsule and its occupants by some means. This is important because the energy could otherwise be continuously consumed within the electric machine in order to create the thrust required to counter-attack the constant gravitational force acting on the capsule. This could soon cause the engines to overheat. This effect is also found in other applications. An attempt to solve this problem is described in the International Patent Application published under WO93 / 01577. This document describes a technique that carries the load of the movement platform on a counterbalance mechanism that has a low effective spring speed. As a particular example, a gas spring system, bent, is described therein. Experience with mechanisms that have been constructed in accordance with the description of WO93 / 01577 has shown that the counterbalance concept described therein does not provide optimal support for a base of electromagnetic motion. The present invention, in one aspect, is based on the understanding that a controlled spring (or a group of controlled springs) with a significant spring rate, it is required for optimal support. To date, a number of designs of electromagnetic actuator, or linear motor have been produced. Various configurations of prior machines have been described in documents such as WO93 / 01646, which describes an electromagnetic device accommodated to operate with cylindrical symmetry as a piston-in-cylinder machine. The main advantage of this form of construction is that the strong forces of attraction between the permanent magnets inside the machine and the magnetic materials that surround them are balanced around a central axis, so that the bearings of the machine do not need to resist any large magnetic forces. An additional advantage of the cylindrical construction is that the magnetic fields of the machine are contained within the outer steel casing of the actuator or rod, and that these can be arranged to interact with the electrical coils of the machine with a high degree of efficiency. Yet another advantage of the cylindrical construction is that the stem armor can carry a sliding seal between it and the internal surface of the stator of the rod, to form the piston of a fluid actuator device. This is beneficial when there is a requirement to produce fast-acting electromagnetic forces that are superimposed on or intermittent with the forces at rest or slowly changing. The last types of forces are best produced by means of a fluid actuator. Electromagnetic elements could otherwise be required to consume electrical power continuously if these were by themselves to provide static force or slowly changing force. In addition, the cylindrical construction of the cylinder piston is suitable for the application of the rod in many industrial control applications where hydraulic or pneumatic piston rods are now employed. This is because the magnetic fields of the rod are completely contained within the case or cylindrical housing, so that the rod is tolerant to the presence of metal chips or other magnetic powders that are a problem for other types of electromagnetic linear actuator. The present invention seeks to provide a structure in which the cylindrical cavity of the stator, of an electromagnetic actuator, is divided into two parts by a seal on the piston / armature element, and includes means by which the armature assembly can also act as the force producing element of a fluid pressure control system, for example as part of a gas spring. It should be noted that WO93 / 01646 and its associated co-pending application WO93 / 01577 These describe a rod construction for application to motion-based machines, in which the property of the gas spring of the rod * is designed to act in one direction only, as to support the weight, is say to resist a gravitational force. For this purpose WO93 / 01646 describes the construction of a passage for the fluid flow connection of only one part of the rod cylinder (namely the bottom side of the piston) to a forming part of the pressurized fluid reservoir of a gas spring . WO93 / 01646 and WO93 / 01577 disclose that the upper part of the piston is allowed to vent at atmospheric pressure, directly or via an exhaust tank. It is desirable to have a more efficient method of controlling the movement of a driving simulator mechanism, than that of WO93 / 01577, using a combination of air pressure and electromagnetic forces in which the individual forces and force gradients of the springs of gas are optimized in relation to the dimensions of the load, so that the energy consumed by the mechanism is at a minimum. For this purpose the gas springs acting below the piston of each rod should not be designed solely for load bearing as in WO93 / 01577 but rather should function as temporary reservoirs in which the potential energy resulting from the action electromagnetic of the rods is stored and from which it can be recycled soon after. This energy recycling technique results in an energy consumption economy that improves the operation and reduces the construction and operating costs of an electromagnetic actuator. In one aspect, therefore, the present invention seeks to provide a motion imparting system in which a continuous load component is supported in an especially effective manner. A feature of the embodiments of this invention, as applied to the so-called movement bases, is that they have a shape that is easily adapted to support a variety of capsule shapes, which is physically stable and robust, which has an ability to Improved to produce large angles of separation and rotary movement and which is easily accessible for inspection and service. According to one aspect of the present invention, there is provided an apparatus for imparting movement to a load, comprising the means for applying a disturbing force to the load and an elastic support for the load, in which means are provided for the dynamic variation in the elasticity or ease to yield to a load of the support during the operation of the apparatus. In one embodiment of the invention, the force-applying means is an electromagnetic actuator. For many applications, a linear electromagnetic actuator may be preferred, although a rotary actuator may alternatively also be employed. In such a case the variation in elasticity can be controlled by the signals generated as an integral of a signal applied to the electromagnetic actuator. For this purpose it is preferred that the variation in elasticity be controlled in dependence on the electric current required to move the electromagnetic actuator against the load. The elastic means may be a gas spring and the variation in elasticity carried out by the variation of the mass of the gas contained within a chamber of variable volume. Such variation can be achieved by controlling the valves that allow gas to enter and / or exit said chamber. Alternatively, the elastic support may incorporate a fluid actuator, possibly a hydraulic actuator, the working fluid from which it may be directed towards or away from the actuator to vary the elasticity thereof. Variation in elasticity can be achieved, for example, by adjusting the pressures on the individual gas springs. In one embodiment this is effected in accordance with the time integral of the currents extracted by the electromagnetic actuator during the movement. By this means the characteristics of the elastic support means are optimized to allow the electromagnetic rods to operate within their speeds and reduce the energy consumed by the complete mechanism. In one embodiment of the present invention, which incorporates an electromagnetic actuator, the armature and the stator of the electric machine comprise a piston in the cylindrical device, the piston or armature being shorter in length than the cylinder or stator, and completely contained within it at all times, the cylinder being closed at both ends by the end members, the piston is provided with a push rod or element extending through at least one of the end members and which is provided with an air seal or air seals to said end members, the armature or the piston element are also provided with an air seal by which the cylinder is divided into two chambers, the armature including the first means to produce a pattern of magnetic field comprising at least two magnetic poles of opposite polarity and if they are more than two poles, then this includes magnetic fields arranged so as to be of alternating polarity along at least part of the axial length of the armature, and the stator being provided with second means to produce an additional magnetic field pattern of at least two poles of opposite polarity if there are more than two magnetic poles, then the poles accommodated thus are to be of opposite polarity along at least part of the axial length of the stator, the second field pattern being accommodated to interact with the first magnetic field pattern, to produce an axial force directed. Preferably, the physical and electrical parameters of the device are arranged in such a way that the electrical terminals can be connected to one or more conventional electronic drive units for controlling the phase and amplitude of at least one of the magnetic field patterns, for cause a desired electromagnetic force, axially directed, to be created between the piston and the armature. Preferably, the two chambers, one on each side of the piston and having a variable volume in accordance with the position of the piston within the cylindrical armature, are provided with pipe connections so that the mass of the fluid within them can be controlled . This allows the piston to function simultaneously as an electromagnetic device and as a dual action fluid rod. According to still another aspect of the present invention, therefore, there is provided the apparatus for controlling relative movement with a plurality of degrees of freedom between a platform and a reference plane, comprising the elastic means for supporting the weight of a platform, one or more actuators for applying perturbation forces between the platform and the reference plane, and control means for controlling the or each actuator to move in one direction or the other, thereby moving the platform with respect to the reference plane, characterized in that the elasticity or ease to yield to a load, of the elastic support means, is variable, and means are provided for dynamically varying the elasticity thereof depending on the control signals applied thereto. In the modes formed as a base of movement there may be three actuators between the motion platform and the fixed reference plane, which may be a fixed part of the mechanism. The actuators have pivots or hinges that connect them to that part of the apparatus defining the fixed reference plane to constrain the movement site of the actuator within a respective plane. The three planes defined in this way intersect along a vertical line that joins the centroid of a lower triangle formed by the pivots of the actuators to the centroid of the triangle of the movement platform, formed by the connection points of the upper ends of the actuators. The upper ends of the actuators have joints or splices that provide universal freedom, so that by choosing the three individual actuator lengths, the movement platform can be caused to assume any chosen position within reasonable limits of lateral displacement, pitch and roll movement. The center of mass of the load is preferably positioned to lie above and close to the centroid of the movement platform and having a support member connected with universal freedom between the centroid of the lower fixed triangle and the centroid of the upper triangle 'Ü ^ M É &A &z ^ (movement), the elasticity of the support member is optimized according to the dimensions of the movement platform. In a preferred arrangement the upper 5-stroke triangle, defined by the ends of the actuators, is smaller in size than the corresponding triangle on the fixed part of the mechanism that defines the reference plane, so as to allow the stroke actuators The limitation of the capsule will result in acceptable deviations of the movement platform in separation and rotational movement, and will simplify the problems of attaching a capsule to the movement platform. Preferably, the angle between the actuator and the horizontal plane in the straight position and at the (operating) level of the movement platform, is approximately 45 °. The central support can be a simple member or an assembly, and can be a metal or plastic spring, a pneumatic rod or a rod in which a liquid acts on a piston in the actuator, the surface of the liquid distant from the piston is pressurized by a gas inside a reservoir. Alternatively, the elastic support can be a bellows unit, with the advantage of Ess-S-:. -. ± '^ í3 * z * Jfe! Iit :. that universal joints or junctions are not required at the interconnections of the bellows unit with the fixed and mobile platforms, and the collapsed length of the bellows may be less than half their extended length. In addition, a bellows does not need an internal sliding seal as required by a sliding piston. As another alternative, or in addition, the central support can be formed from a plurality of pressurized gas taps, to be accommodated to provide an overcentral oscillating connecting action that eliminates most of the support force when the platform of Movement adopts minimum height or loading position. Preferably, the actuators are electromagnetic actuators and are designed to have sufficient thrust reserve capacity, to be able to accommodate the practical deviations of the position of the center of mass of the movement platform from the ideal position near the exact centroid of the upper movement triangle. It will be understood that when an impactor system of motion (hereinafter referred to as a movement base) is in operation, there is a central, straight and level position, to which the capsule must be continuously returned. The occupant or occupants of the closed capsule 5 are or are not aware of this continuous centering action, which is carefully controlled to mix at the bottom of the other movements. It takes as much energy to return the capsule to its initial position as it took to move it in the first place, and this energy can be stored in a spring system. In addition, because the center of mass of the payload is invariably above the centroid of the movement platform, there is a twist significant that it helps any movement of pitch or roll, which must be opposed by means such as spring action. However, the restoration forces produced by the spring suspension should not be too much.

Large ones or even these will demand disproportionately large actuating forces to cause the initial excursions. When attempts have been made to apply the principles of WO93 / 01577 to a form common six-axis motion platform ~ »Six offshoots (known as a Stewart platform under its designer), have been found a number of difficulties. In particular, it has been shown that if the static load exceeds a certain well-defined boundary, depending on its height above the centroid of the movement platform, the mechanism has a tendency to go 'vertical plunging' by a combined forward movement. and pitching, from which it can not be recovered by electromagnetic forces alone. This defect imposes a strict limit on the payload capacity - and therefore the utility - of the machine. In still another aspect, therefore, the present invention provides a motion imparting system having six degrees of freedom using six accommodated actuators as first described by Stewart, in which the concept described in the International Patent Application is not applied. WO93 / 01577 namely, the weight counterbalance system is not applied, but in which the forces for the static load support are applied in a different, specific and efficient manner, which greatly reduces the energy demands electromagnetic over the actuators for any given payload, thus raising the payload limit and improving the dynamic operation of the device. According to still another aspect of the present invention, therefore, there is provided an apparatus for controlling relative movement at a plurality of degrees of freedom between a moving platform and a reference plane, comprising means for supporting the weight of the motion platform, one or more actuators for applying intermittent disturbance forces between the platform and the reference plane, and control means for controlling the or each actuator, thereby varying the position and / or orientation to the platform with respect to the reference plane, characterized in that the means for supporting the weight of the movement platform comprises respective elastic support members, each associated with a respective actuator. In the present invention, in the idealized case of a Stewart platform, three points of the movement platform that lie on a triangle, are connected to three corresponding points that define a triangle on the part of the mechanism that defines the reference plane by means of of the six electromagnetic actuators that have unions that provide universal freedom of movement in the interconnections between the actuators and the fixed platform, and similar unions between the actuators and the movement platform, so that by choosing the six lengths of the actuators individual the movement platform can be moved to adopt a wide range of orientations by movement which can be any, or any combination of, movements commonly known as lateral displacement movement, wave motion, oscillation, pitch movement and swinging. The center of mass of the load is preferably positioned to lie above and close to the centroid of the movement platform, and the diameter of the circle of the movement platform preferably has an optimum ratio to the diameter of the fixed circle of the reference plane. The term 'circle' of the platform or plane is meant to mean here the circle of circumscription around the points of ^^^^ > ^^ & ^^ coupling at the ends of the actuators to the platform or the reference plane. Each electromagnetic rod may be associated with an individual sp or be designed and mounted to the base of movement so as to also act as an output actuator of an individual sp, the sps being such as to support the weight of the movement platform (and any load on it) in the straight and level position. It is a feature of the present invention that the sp speeds are optimized in relation to the energy consumption of the apparatus and the forces exerted by each individual sp are preferably adjustable by a periodic verification system, to reduce to zero the integral of the current of the associated actuator over a chosen time interval. Preferably, the upper movement circle is smaller in size than the corresponding circle on the fixed part of the mechanism that defines the reference plane, and the ratio of two radii is chosen to optimize the energy demand. The optimal proportion of the base dimensions is close to 1: 1.5.

Preferably, the effective values of the two radii are chosen such that the angle between the actuators and the horizontal plane when the six actuators are at an extent of 50%, is approximately 45 degrees. If a gas sp suspension is employed, preferably the ratio of the sealing volume of each gas sp system, when the actuator is fully extended to the sealed volume, when the actuator is fully retracted, is also chosen to minimize the consumption. of operating energy of the apparatus. This optimum ratio of gas sp volumes is considered to be in the vicinity of 1.8. Preferably, means are provided for periodically verifying the magnitude and direction of the electrical current demand for each actuator, and the pressure in each gas sp is accommodated to be frequently adjusted du the operation in relation thereto, to maintain an integrated symmetry. of the demand for electric power in a chosen period of time. In the embodiments of the present invention, three points of the movement platform can be connected to three corresponding points on the fixed part of the mechanism defining the reference plane by the actuators having universal freedom of movement in the connection between the actuators and the reference plane, and between the actuators and the movement platform, so that by the choice of the three individual rod lengths the movement platform can be moved to adopt any chosen position within the limits of movement of the actuators in the movement of lateral displacement, pitch and roll. The center of mass of the load is preferably positioned to lie above and close to the centroid of the movement platform, and preferably has a support member connected with freedom of universal movement between the centroid of the reference plane and the centroid of the platform of movement. In this context it is assumed that the centroid of a platform or plane is the centroid of the circle that circumscribes the triangle defined by the three points of connection to the three (or six) actuators. The sp or sp speed of the support is preferably optimized to the parameters of the platform and the load. In a preferred embodiment, the circle circumscribing the triangle of the connections of the actuator to the movement platform is smaller in size than the corresponding triangle on the fixed part of the mechanism that defines the reference plane, to allow the actuator rods of limited stroke produce acceptable deviations of the upper platform in pitch and roll, and to simplify the problems of attaching a capsule to the movement platform. Preferably, the ratio of the size of the fixed platform (base) that defines the reference plane to that of the movement platform, is approximately 1.5: 1. Preferably, the angle between the actuators and the horizontal plane when the three actuators are in the straight and level (in operation) position of the movement platform, is approximately 45 °. Preferably the central support is a bellows unit. This has the advantage that the upper and lower ends of the bellows can be fixed directly to the movement platform and to a fixed base defining the reference plane. The collapsed length of the bellows can be less than half of its extended length and there is no need for an internal slide seal. It will be understood that one of the features of a bellows assembly is that in an upright and vertical axis orientation this will allow vertical movement, and the upper end of the bellows may be inclined at any pitch or roll angle with respect to the lower end, but it will not easily allow lateral translation (oscillation or oscillation) nor will it allow axial rotation (yawing) at all. In this way, a bellows assembly can function as a gas spring unit and as a restriction mechanism. Preferably, the actuators are electromagnetic rods designed to have sufficient thrust reserve capacity, to make it possible to accommodate practical deviations from the position of the center of mass of the movement platform from the ideal position near the exact centroid of the upper movement triangle.

The various embodiments of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an axial sectional view of an actuator formed as an embodiment of the present invention; Figure 2 is a schematic view of an actuator and control components, formed as a second embodiment of the invention; Figure 3 is a schematic view of an alternative control configuration for an actuator; Figure 4 is a diagram illustrating an additional control configuration; Figure 5 is a schematic perspective view of a prior art configuration of a motion imparting device; 25 Figure 6 is a schematic perspective view of an alternative configuration of the known motion imparting device of the prior art; Figure 7 is a schematic perspective view of a movement imparting device, formed in accordance with the principles of the present invention; Figure 8 is a schematic perspective view of a further embodiment of the present invention; Figure 9 is a schematic perspective view of a further embodiment of the present invention; Figure 10 is a simplified diagram of a Stewart platform formed as a further embodiment of the present invention; Figure 11 is a top plan view of the platform illustrated in Figure 10; • Figure 12 is a schematic view of the embodiment of Figure 10, shown is a first operation configuration; Figure 13 is a schematic diagram illustrating a further embodiment in which the reference plane is smaller than the movement platform; Figure 14 is a top plan view of the embodiment of Figure 12; Figure 15 is a top plan view of the embodiment of Figure 13; Figure 16 is a top plan view of the platform of Figure 12, shown with the moving platform moved to the right; Figure 17 is a top plan view of the embodiment of Figure 13, with the moving platform moved to the right with reference to the configuration shown in Figure 15; Figure 18 is a schematic plan view illustrating -L ^ ÑIá, anticipated optimal dimensions of a Stewart platform formed as an embodiment of the invention; Figure 19 is a three-dimensional graph of energy consumption of a typical Stewart platform motion imparting apparatus, formed as an embodiment of the present invention; Figure 20 is a diagram illustrating how the energy demand varies over the actuators, with the type of movement; Y Figures 21A and 21B are diagrams illustrating the control sequences for the actuators formed as embodiments of the present invention.

Referring now to the drawings, the actuator shown in Figure 1 comprises a piston or armature 8, which moves inside a cylinder or stator 1. The piston is connected to a push rod or tube 7, which extends to through one of the extreme pieces 2 via a? air seal 3. A sealing ring 5 is fitted to the piston 8 to divide the cylinder into two chambers, which are pressurized or evacuated as appropriate via the pipe connections 4a, 4b. The piston is also adjusted with bearing rings 6, whose function is to constrict the position of the piston, so that it moves smoothly along the central axis of the device. It will be understood that when the gates 4 are closed, the action of the air seal 5 will cause the movement of the piston inside the cylinder, to compress the gas in one of the chambers while allowing the gas in the opposite chamber to expand. In any case, a force that tends to restore the piston to its reference position in the absence of electrical power will be created. By adjusting the mass of the gas sealed inside the two chambers, the forces produced by the two springs can be predetermined, and by the choice of the ratio of the two load positions the reference (or balance) position can be preset. When it is necessary to reduce the proportions or gas spring speeds to a low value, the construction of the end members 2 is modified to allow the connection of an external reservoir to each member. The means by which the pneumatic valves (not shown) in the lines connected to the gates 4, can be controlled in accordance with the electric currents extracted by the rod when energized by a drive unit, will be described later herein. for the cyclical and pseudo-random placement of a load. By providing an installation for the almost continuous adjustment of the parameters of the gas springs in opposition, in relation to the symmetry of the electrical actuation currents in a rod, it is possible to minimize the energy consumed by the rod, with which they are made Significant savings is your physical specification. In Figure 2 the invention is shown applied to an electromagnetic rod. The piston carries a seal 5 by which the interior of the cylinder 1 is divided into two chambers A and B. The mass of the gas in each chamber is controlled by the valves 9 and 10 which are energized by the pressure control unit 11 . The electromagnetic forces produced by the rod are controlled by the unit 12, which receives the position commands 13 and the position feedback signals 14 from a transducer 5 (not shown) connected to the output rod of the rod or tube. 7. The unit 12 provides the energy to the rod along the control lines 17. The signal 15, produced by the controller 12 of the position of the rod, is a is a significant parameter of the process over which the pressure control unit 11 is designed to act, as described below by way of example, if the rod is used as part of a movement base of the type referred to above, is chamber volume B is allowed to remain at atmospheric pressure. The valve unit 9 is not present and the gate 4b to the chamber B is accommodated to have a diameter internal, so that the air can pass freely to and from the surrounding environment. Of course, the rod may be constructed to completely eliminate the B-chamber, by adopting an open-ended configuration. With the final purpose to achieve a sufficient spring speed low, it may be necessary for chamber A to be connected via a tube of large internal diameter to an external reservoir. Similar considerations apply to industrial applications, in which the rod is required to support a load on a vertical or approximately vertical axis, or to other applications such as elevators, for example. The controller 11 then acts via the valve unit 10 to increase the mass of the gas in the chamber A, when the parameter 15 indicates that the current demand by the actuator is predominantly in the direction that could increase the volume of the chamber A, and vice versa. It will be understood that by this means the pneumatic system reduces to a minimum the current demanded by the rod and increases the efficiency of the system. It will also be understood that the arrangement is tolerant to pneumatic leaks in any direction, to changes in temperature and to changes in the operating cycle, or to the almost random sequence of movements made by the rod. This is self-calculated for changes in the valve of the dead load, and adaptable to the movement of the rod in a parking position "at any time." A mathematical analysis of the system also demonstrates that the pressure adjustment is fault-tolerant in the final balance region and that the control cycle is highly stable Consider now the case in which the rod does not experience a force at rest (eg gravitational) that tends to reduce the volume of chamber A. For example, the rod can be used to place an inertial load on a repetitive cycle on a track or horizontal path having a small coefficient of friction The controller 12 is then required to calculate the average position of the rod from the values of the signals 14 of the position transducer, averaged over at least one complete cycle of movements, or in the case of pseudo-random movement, in a range of significant time. The controller 12 is then required to measure the instantaneous current used by the rod and to multiply this value by the distance of the rod from the average position computed at that time. The rounded sum of these products (or "current moments") is then passed to the controller 11 of the valve as parameter 15 of the process. The controller 11 then acts to increase the mass of the gas in the chamber A when the parameter 15 indicates that there is a predominance of current demand in a direction of force that would tend to move the rod towards its central position by increasing the volume of the chamber A. The controller 11 is accommodated to decrease the mass of gas in chamber A, if the opposite predominance is indicated. The pressure of the chamber B is accommodated to be such that the forces on the two opposite sides of the piston 8 are balanced when the arm is in its computed median position. As illustrated in Figure 2 the system includes the pressure transducers 20 and 21 derived in the lines coming from the valve assemblies 9 and 10 via the low pass frs (not shown). The transducer 20 indicates the average pressure in the chamber B and the transducer 21 indicates the average pressure in the chamber A. The controller 11 then acts on the valves 9 so that the pressure value 20, multiplied by the surface area of the piston in chamber B is equal to the value of pressure 21, multiplied by the area of the surface of the piston in chamber A. It will be understood that this balancing function can be carried out from simplest way by using diaphragm-operated pneumatic pressure controllers, which have a pre-adjusted coefficient facility, which may be a preferable arrangement in some machine applications. The external tanks, whose function is to reduce the speed of the gas springs, may or may not be connected to the A and B chambers, according to the dynamic force profiles required of the system. Figure 3 shows the invention applied to an electric linear motion actuator that is not constructed in a way that allows pneumatic forces to be directly applied to the drive output. For example, the linear motor can be of the open, flat configuration, using a permanent magnet armature suitable for connection to a three-phase servo motor drive unit. In this case the linear motor 25 and its output element 26 are coupled by suitable means 28 to a pneumatic rod 27, which has a piston 8 and the chambers A and B, etc., as previously described herein. The mode of operation is the same. If the load is predominantly constant (for example gravitational), the chamber B of the stem 27 (which forms the output element of the gas spring system) is vented to the atmosphere and the mass of the gas in chamber A is thus controlled to balance the current demands for thrust in the opposite directions. If the load is predominantly inertial, the pressure in one chamber is controlled to balance the moments of the current demands around the average position of the actuator, and the pressure in the other chamber is adjusted to balance the forces on the piston 8 in the average position of the system. Figure 4 shows the invention applied to a linear positioning device energized by a rotary motor. In this example we choose a band-driven arrangement, but the invention can equally be applied to a crank actuator with meshing or to a ball screw actuator, for example. * 3C S¡ajS £? R. . 3 §? «**" * Here, the rotary motor 25 moves the carriage 29 by means of the bands 30. The output element 26 is coupled to the gas spring by a suitable connection 28. The operation of the system for the gravitational or inertial loads is as previously described, having the numerations of the various elements the same significance as up to now. It will be understood that the invention is not restricted to the machine in which the full force of the spring is provided by the spring or gas springs, controlled by unit 11 and valves 9 and 10. It may be preferable for the machine, of which the positioning mechanism forms a part, which is equipped with additional springs, either gas or metal, whose characteristics are pre-established to provide part of the energy storage tank of the mechanism. It will be understood that all of the spring force necessary for the efficient operation of the machine can be provided by metal springs or by gas springs, which are manually adjusted to the correct values by a ^ '. a person trained n who obss the current consumption characteristics of the electric motor, in order to make this adjustment. Referring now to Figure 5, the stationary platform or base is designated by the number 31 and the mobile platform is referred to by the reference number 32. The rods 33 form the interconnections between the stationary and moving elements. It will be appreciated that by the implementation of the appropriate variations in the lengths of the rods, the attitude and position of the movable platform relative to the stationary platform can be changed. It will be appreciated that as each rod extends or retracts, the angle between this rod and the horizontal surface must change. The rods rotate in vertical planes around their lower hinges 34. In order to increase the pitch and roll skills of the platform, and improve the accessibility of the mechanism for construction, sce and maintenance, a feature of this invention is that the tripod be constructed so that it adopts the more conventional form illustrated in Figure 6. In this fe ¥ Figure, the upper platform 42 is now smaller than the lower platform 41. It will be noted that the hinges or pivots at the lower ends of the stems 43 (which are the elements of the machine bearing the greatest stresses) are at the outer ends of the movement base, making them and the main bodies of the rods more accessible for assembly, inspection and maintenance. It will also be noted that the surface of the fixed platform is not agglomerated and not obstructed by the restriction structures, allowing free access to the central area, if required. An additional advantage of this configuration is that the interconnection area between the movement platform and the simulator capsule is reduced, which places less restrictions on the design of the capsule floor and arrangements for access to the capsule. The mechanism shown in Figure 6, however, has the disadvantage that under some extremes of movement, the angle between the movement platform 42 and the horizontal may be greater than the angle between at least one of the rods 43 and the horizontal. - so that consequently the mechanism oscillates in a secured position. In order to prevent this, the relative dimensions of the upper moving platform 42, the lower moving platform 41 and the lengths of the rods are provided so that the tilting action can not occur. In general, the size ratio of the fixed platform 41 to that of the mobile platform 42 is small. Figure 7 illustrates this improvement, the elements of the mechanism have the same reference numbers as in the embodiment of Figure 6. Figure 8 shows a modality having a vertical elastic support member, central or assembly 45 by means of which the static load of the movement platform 42 is counterattacked to eliminate the requirement for the electromagnetic rods 43 to generate a continuous force. It will be appreciated that the vertical spring velocity of the central elastic support member will need to be optimized in accordance with the general design of the movement base and its operating parameters. If the support member is a gas spring actuator it may be necessary for it to communicate with an adjacent pressurized gas reservoir (not shown) of the appropriate volume. Alternatively, the simple vertical actuator can be replaced or aided by two or more angled actuators in an inward direction, towards the centroid of the movement triangle, which is provided to rotate through an angle in a vertical plane as the movement platform is moved. It rises and falls. The angled actuators can be pre-pressurized gas taps, such as those used to support a car luggage door, arranged to have an action on the center, which can be used to retain the movement platform in the loading position , when necessary. Figure 9 shows a modality with a vertical, central bellows unit, by means of which the dead load of the movement platform 42 is counterattacked to eliminate the requirement for the electromagnetic rods 43 to generate a continuous force. It will be appreciated that the vertical spring velocity of the center bellows should be optimized according to the general design of the movement base and its parameters of : J * -; «A, operation. This means that the flexible part of the bellows can be mounted on a central plinth or rigid base of a chosen height. (The rigid plinth is not shown separately in Figure 8). The spring action of the bellows can be increased by two or more suitable gas taps (not shown), arranged to rotate through an angle in a vertical plane as the platform of motion rises and falls. These can be designed to have an action on the center, which can be used to hold the mobile platform in the (lower) loading position when necessary, without the requirement to depressurize the bellows unit, thereby reducing the consumption of compressed air. It will be understood that the use of a bellows unit as the central restriction member does not exclude any arrangements for the mounting and connection of the electromagnetic actuators, so that these may also act as individual gas springs, instead of or in combination with the force generated by the bellows and / or the gas spigots. When the electromagnetic actuators are also used as snap-on spring elements, it is preferable that means are provided for the frequent adjustment of the pressure to minimize the long-term integral of the actuating current - and thus the consumption of Energy. The motion imparting device of the invention consists of a mechanism in which one of the members (the base platform) can be considered as the stationary member, and the other member (the movement platform) can be considered as placed by means of the actuators. Figure 10 is a simplified diagram of a Stewart platform, showing the movement platform 51 supported by the rods 53 above the base platform 52. In this diagram, the radius 54 of the movement platform circle is smaller than the radio 55 of the base platform. Figure 11 shows this in plan. Figures 12 and 13 show the conceptual difference between a Stewart platform in which the radius 54 is smaller than the radius 55 as in Figure 12 and a Stewart platform in which the radius 54 is greater than the radius 55, as in the Figure 13. Consider the forces on the gas springs if the motion platform undulates forward (to the right in Figure). For the case in which the movement platform is smaller than the base platform, the rods 5 56 on the "front" of the movement platform are compressed, producing forces that tend to push the edge of the platform upwards, while that the rods 57 on the "back" of the platform are extended, by reducing the upward component of its force and allowing the trailing edge of the moving platform to fall. One might therefore expect that such movement would cause the platform of movement to nod upwards when moving back and forth (Figure 16). Conversely, by similar reasoning, the behavior of a mechanism in which the radius of the movement platform is greater than that of the base platform could be expect it to cause the movement platform to pitch down when moving forwardly (Figure 17). Therefore, what follows is that between the two extremes there must be a configuration optimum in which a reciprocating oscillating movement e ^ ü? ^ - ^ ^ also does not cause escalation or diving tendencies. When any given group of rod dimensions is taken into account, the optimum ratio of the size of the lower platform to the size of the upper platform could be expected to be 2: 1, as shown in the simplified diagram of Figure 18. Figure 19 is a three-dimensional graph of the energy consumption of a Stewart platform motion base, typical for a reasonable simultaneous combination of the six possible movements (up and down movement), swell, sway, pitch, roll and swing). One axis shows how the energy consumption of the movement base varies with the size ratio of the fixed and mobile platforms and the other axis shows how it varies with the volume ratio of the gas spring system (or with the velocity of spring of an equivalent solid spring system). It will be noted that the best proportion of platform size falls in the region of 1.5 and that the best proportion of gas spring falls in the region of 1.8. This is true for all types of shanks and movement bases examined so far.

Figure 20 shows how the energy demands of the rod vary with the type of movement and the "type of axing" of the mechanism, as determined by the ratio of the gas spring volumes. It should be noted that a base of smooth or "counterbalanced" movement would have a large gas spring reservoir and a small volume ratio and lie to the left of the diagram, while a base of movement "on hard springs" could fall to the right. As expected, the energy consumption rises sharply for all movements as the hardness of the sprue increases at the edge of the diagram. However, it will be noted that the energy consumed by a pitch movement is very large when the spring is optimized for the up and down movement, this is when the mechanism is "counterbalanced". It will also be noted that the energy consumed by the pitch movement can be much reduced by increasing the system spring to an optimum value, which is less than that at which the "hard" spring forces begin to dominate. There are optimal suspension characteristics, similar ! hfc for the other base movement modes but the pitch movement is dominant. (It will be recalled that the concept of WO93 / 01577 mainly failed in the pitch mode). It will be understood that while the principles of this invention have been set forth with reference to the six-axis movement system, known as the Stewart platform, these also refer to the movement bases of other types, such as the three-axis system referred to above. in WO93 / 01577 and to various other movement base designs described in our co-pending patent applications. It will be further understood that the simulator mechanism has an equivalent mirror image on the stabilized platform, in which (for example) the lower platform is subject to the movements that must be denied by the relative movements of the rods to maintain the upper platform stationary The optimized design of the base movement mechanism described herein therefore also refers to stabilized platforms based on a Stewart configuration and the principles in general refer to stabilized platforms of other types.

Returning now to Figure 21A this shows the main sequence of the control functions of an electromagnetic actuator with an associated or incorporated elastic support in which the elasticity is variable to take into account the variant parameters such as the instantaneous position, the position to demand, load, acceleration, speed, etc. In this mode, the elasticity is varied depending on the instantaneous load, which is determined as a function of the current taken by the electromagnetic actuator in response to demand signals. Figure 21A shows the sequence of steps followed in varying the elasticity of a gas spring. In step 201, the drive current, detected by the appropriate sensors, is applied at an input to the control system. The signal is integrated in step 202 as a rolling integral over the successive sampling periods, the length of which depends on the specific circumstances but which may be, for example, in the region of three seconds in the case from a base of entertainment movement.

The integral formed in this way is then compared with the predetermined threshold values, in step 203. The excess over the threshold (if it exists) then controls the generation of a control signal or "drive pulse", the length of the which is proportional to the excess. This signal controls the opening of a valve to admit or release gas from the closed chamber, of a gas spring (not shown) associated with an electromagnetic actuator in any of the ways described hereinabove. This varies the support given to the load by the gas spring by continuously varying or "tuning" its elasticity to the dynamic condition of the actuator. For example, if an actuator is spreading rapidly, the valve is opened to allow the gas to enter a chamber, the volume of which is increasing, thereby reducing the resistance to movement that could otherwise be exerted. The thresholds are selected such that the "tuning" of the gas spring takes into account the possibility of the return movement in the short term, so that the chamber has no gas admitted to it that must be immediately released, but rather the determination of the The requirement for the introduction or release of the gas is computed over a sufficient time to smooth the transient rapid movements. Figure 21B shows the major steps in a system for supporting an alternating mass of movement, the displacement of which is driven by an electromagnetic actuator. As for a base of movement, the current of movement in the electromagnetic actuator is detected and applied in 206, but in this case the position of an alternating movement piston or other alternating movement member of the actuator is detected in 207 and, in addition, the central reference signal 208 is also applied in step 209. From these signals a calculation of the current moment around the central position of the mobile member is made, after which, in step 210, a integral of the actuation current valve for a period of time that represents an exact number of cycles of the mass of alternating movement, with a compensation of time to face the cessation of movement.

As described above, this integral is compared to the threshold values in step 211 and the pulse length of a signal applied to a valve is determined in step 212. This signal is applied to one side of the piston, in this case the side of the gas pressure rod shown in step 213, and the pressure as a predetermined fraction of the average pressure value is determined in step 214 to determine the required gas pressure, on the other side of the piston in step 215, to balance the variations that are introduced into the chamber on the first side of the piston.

Claims (17)

1. An apparatus for imparting movement to a load-comprising means, for applying a disturbing force to the load and an elastic support for the load, in which means are provided for effecting the dynamic variation in the ease of yielding to the load or elasticity of the support during the operation of the apparatus.

2. The apparatus according to claim 1, wherein the actuator controls the position of the load with at least one degree of freedom, and comprises means for applying a disturbing force to the load, thereby causing displacement of the load. same, and the elastic support is able to apply a force to the load in addition to the intermittent force, the means for dynamically varying the elasticity or ease of yielding to the load, of the elastic support means, which acts in a manner related to the force applied to the load, which actively cooperates in the displacement of the same.

3. The apparatus according to claim 1 or claim 2, wherein the means for applying the perturbation force is an electromagnetic actuator.

4. The apparatus according to claim 3, wherein the actuator is a linear electromagnetic actuator.

5. The apparatus according to claim 3 or claim 4, wherein the variation in elasticity is controlled in dependence on the electric current required to accelerate the charge.

6. The apparatus according to any of claims 3 to 5, wherein the variation in elasticity is controlled by the signals generated as an integral of a position demand signal applied to the electromagnetic actuator.

7. The apparatus according to any of claims 1 to 5, wherein at least part of the elastic means is a '** • > * • r .- ^ ».- gas spring and the variation in the capacity to support load or elasticity is achieved by varying the mass of the gas contained within a chamber of variable volume.

8. The apparatus according to claim 7, wherein at least part of the elastic means is a gas spring and the variation in elasticity is achieved by controlling the 10 valves that allow gas to enter and / or exit the chamber.

9. The apparatus for controlling relative movement in a plurality of degrees of 15 freedom between a platform and a reference plane, comprising elastic means for supporting the weight of a platform, one or more actuators for applying perturbation forces between the platform and the reference plane, and Control means for controlling the or each actuator, to move in one direction or in the other, thereby moving the platform with respect to the reference plane, characterized in that the ability to withstand load or The elasticity of the elastic support medium is variable, and means are provided to dynamically vary the elasticity thereof in dependence on the input signals to them.

10. The apparatus according to claim 9, wherein the actuators have pivot connections to the part of the apparatus defining the fixed reference plane, whereby each actuator is constrained to rotate about the pivot connection within a plane respective.

11. The apparatus according to claim 9 or claim 10, wherein a support member is connected with universal freedom between the movement platform and the reference plane.

12. The apparatus according to claim 11, wherein the elasticity of the support member is selected according to the parameters of the movement platform.

13. The apparatus according to claim 12, wherein the inclination between The actuators and the horizontal plane with the movement platform in a resting position, is approximately 45 °.

14. The apparatus for controlling relative movement at a plurality of degrees of freedom between a moving platform and a reference plane, comprising means for supporting the weight of the moving platform, one or more actuators for applying perturbation forces between the platform and the reference plane, and control means for controlling the or each actuator, whereby the position and / or orientation of the platform with respect to the reference plane is varied, characterized in that the means to support the weight of the platform mobile comprise respective resilient support members, each associated with a respective one of the actuators.

15. The apparatus according to claim 14, wherein the ratio between the diameter circumscribing the circle around the coupling points of the ends of the actuators to the movable platform, with respect to the diameter of the circle of circumscription around the points coupling around the ends of the actuators to the part of the apparatus that defines the reference plane, is in the region of 1: 1.5.

16. The apparatus for controlling relative movement in a plurality of degrees of freedom between a moving platform and a reference plane, comprising elastic means for supporting the weight of a platform, one or more actuators for applying a force of disturbance between the platform and the reference plane, and control means for controlling the or each actuator, to vary the position and / or orientation of the platform with respect to the reference plane, by the operation of the accusers, in which they are also provided restriction means for preventing undesired movements of the actuators between the mobile platform and the reference plane.

17. The apparatus according to claim 16, wherein the restriction mechanism comprises or includes a bellows unit.