GB2366604A

GB2366604A - Interface

Info

Publication number: GB2366604A
Application number: GB9218936A
Authority: GB
Inventors: Frederick Alistair Johnson; Malcolm Alexander Swinbanks
Original assignee: GEC Marconi Ltd; Marconi Co Ltd; BAE Systems Electronics Ltd
Current assignee: BAE Systems Electronics Ltd
Priority date: 1992-09-08
Filing date: 1992-09-08
Publication date: 2002-03-13
Anticipated expiration: 2012-09-08
Also published as: GB2366604B; GB9218936D0

Abstract

A marine vessel (1, Fig 1) has, on its surface immersed in a fluid medium, a number of piezo-electric elements 5, 10 thereon. Each element has, associated with it, an integrated circuit 8 which is programmed so as to cause the elements to modify the surface behaviour of the vessel enabling the surface to act as an extension of the fluid medium. This facility enables turbulence to be reduced, acoustic reflections to be cancelled, escape of noise from the vessel to be eliminated, and acoustic signals to be transmitted as and when necessary. Selected elements act as sensors and others as drivers. The elements may be used as submarines or aircraft.

Description

2366604 AN INTERFACE BETWEEN TWO MEDIA This invention relates to an

interface between two media. The invention arose during consideration of the solid-liquid interface on the surface of marine vessels and of ways in which shear forces and vortices could be reduced in order to increase the speed, improve the efficiency and reduce the noise made by the vessel.

The invention does however have other applications. The interface could, for example, be used on the surface of an aircraft. it can be used to suppress unwanted transmissions and reflections of noise and other acoustic signals. It can be used to prevent the escape of noise or other acoustic signals from a particular area. It can also be used as a detector of acoustic noise or signals.

This invention provides an interface element, for use with a plurality of like elements in an array, the array defining an interface between two media, each element being of laminar form having two major faces and including sensing means, capable of sensing a disturbance at one of the faces in one of the medial, and controllable means capable of responding in such a way as to cause the elements of the interface to simulate the motion of a direct extension of said one of the media, and control means for receiving signals from the sensing means and controlling the controllable means accordingly.

By employing the invention, it is possible for the "control means" in each element to behave "intelligently" in accordance with a pre-set programme so as to modify the behaviour of the interface in any required manner and in dependence on the disturbances, if any, in one of the media. In addition to causing suppression of reflections of acoustic or other signals from the interface by simulation of a direct extension of the fluid medium, the programming can be such as to prevent the passage of sound or vibration across the interface, to stabilise or suppress flow instabilities where one of the media is a fluid, to transmit acoustic signals in one of the media, or to create deliberate flow instabilities.

It would be possible to use a central computer as the "control means". However in a preferred arrangement, the layered structure of each element includes one or more of layers comprising a control circuit (preferably an integrated circuit) which forms the control means. By making all the elements, or all the tiles, substantially I - 3 identical, except for the way in which they are programmed to behave at any one time,.the production costs can be minimised.

In the laminar structure, at least one of the layers is preferably piezoelectric. This piezo-electric layer can be used for sensing or for creating or modifying disturbances in one of the media. Possibilities do however exist for non-piezo-electric devices in accordance with the invention. For example each of the controllable elements could be fluid actuated, acting on known principles for example using a heating effect or a hydraulic-mechanical mechanism.

It will normally be necessary to supply some form of power to each of the elements. Where the interface is on the surface of a marine vessel this can conveniently be provided via the hull of the vessel with a return path through the water. However other possibilities exist. For example an electrically conductive lead could be connected to each of the elements.

Where it is desired to modify the behaviour of the elements in some way, for example to select between the different functions explained previously, some line of - 4 communication needs to be provided between the elements and a central control station. This could be done by way of a separate conductor or conductors connected to all the individual elements. Another possibility, which is perhaps preferred, is to modulate the power supply with a digital signal carrying the required information. Each element can be pre- programmed with its own individual address and to respond to control signals identifying that address. Such an arrangement is particularly attractive since it would enable an array of identical elements to be applied e.g. to the surface of the ship or submarine and to be controlled from a central station without modification to the existing hull structure.

It is possible for each of the elements to be manufactured separately and to be applied individually to the interface after manufacture. it is considered preferable however to manufacture the elements in small groups of inter-connected elements sharing a common control layer. The advantage of this possibility is that each group of elements, which will be referred to as a "tile" during this specification, can be applied relatively easily to the appropriate surface.

Another possibility is for all the elements to be connected together during a manufacturing process. The resulting multi-element structure must however be sufficiently flexible to conform with the shape of the surface to which it is to be fitted.

it may be necessary to provide some form of interconnection between adjoining elements or between adjoining "tiles". This interconnection may be necessary in order that each element should be able to communicate with its neighbours. The interconnection can be provided by a physical conductive link created during installation of the array of elements. Preferably however it is provided by some non-contact mechanism such as a capacitative or inductive link.

If the array of elements is required to perform two functions such as stopping noise escaping from a particular area on one side of the interface and modifying flow characteristics for fluid on the other side it may be necessary to provide two layers of piezo-electric or other sensing material associated with the media on respective sides of the interface.

One way in which the invention may be performed will now be described by way of example With reference to the - 6 accompanying drawings in which:Figure 1 is a side elevation of a marine vessel shown partly broken away provided with an interface constructed in accordance with the invention forming the boundary between the hull of the ship and the water; and Figure 2 is a perspective view of an array of elements forming one of a large number of tiles illustrated generally in Figure 1.

Referring firstly to Figure 1 there is illustrated a marine vessel 1 which in this illustrated example is a surface vessel but could in other embodiments be a submarine. The part of the hull of the vessel I in contact with the water is coated with an array of tiles 2. These are controlled by a central control station 3 which communicates with them and supplies power to them through the hull of the ship, which is conductive. A return earth path is provided by way of a suitable connection to the sea (which is of course conductive). The control signals given by the control station 3 are in digital form and are provided by modulating the power supply. The control station is able to address each tile individually and to give it the following instructions.

(a) Whether the tile- is to be used to suppress reflection of acoustic signals incident on the hull from the sea.

(b) Whether the tile is to be used to prevent the escape of noise from within the hull.

(c) Whether the tile is to be used to stabilise and suppress flow instabilities of the water adjacent to the hull.

(d) Whether the tile is to be used for the purpose of detecting sound received from the sea. (In the specification the word "sound" is to be construed as including all forms of mechanical vibration e.g. ultra-sonic signals).

(e) Whether the tile is to be used to create deliberate flow instabilities for the purpose of assisting in steering the vessel.

Referring now to Figure 2 there is shown one of the tiles of Figure 1. This comprises an upper layer 4 comprising an array of individual piezoelectric elements 5 - 8 separated by an insulating mastic 6. The upper surface of each element 5 is exposed to the sea which forms one electrode. The opposite side carries an electrode 7. Each electrode 7 makes contact with the upper surface of an integrated circuit 8. This integrated circuit makes contact with electrodes 9 of lower piezo-electric elements 10. The latter are identical to the elements 5 with the exception that their electrode surfaces 9 are made of a dense material to provide the necessary inertia to enable the elements 10 to act as accelerometers which detect vibration of the hull of the ship and acoustic energy transmitted through it. The lower surfaces of the elements 10 are in contact with an electrode 11 connected to earth via a link 12 to the integrated circuit 8. The electrode 11 is insulated from the hull of the vessel by a dielectric layer 13.

The integrated circuit receives signals from selected piezo-electric elements 5 and 10 (selected for use as sensors) and transmits high voltage signals to other selected elements 5 and 10 which therefore act as actuators. The integrated circuit receives power from the control station 3 via a link 14 connected to the hull of the ship. The power supply is modulated to supply signals indicating the required function of the tiles. Plates 15 enable the integrated circuit of one tile to communicate with adjacent - 9 tiles using capacitive effects between pairs of plates 12 on the adjoining tiles.

When a tile is instructed to suppress reflection of sound energy on it or to stabilise and suppress flow instabilities of the sea water adjacent to the hull selected elements 5 act as detectors. The integrated circuit causes other remaining elements 5 to respond in such a way that the upper surfaces of the elements 5 simulate the motion of a direct extension of the fluid medium. Such a direct extension of the fluid medium causes the interface to be undetectable and a marine vessel 1 having such a hull/water interface would be "transparent" i.e. cause no reflection and create no shadow of or relative to an acoustic source. The mathematics relating to the detailed performance of this function is described in the proceedings of the Institute of Acoustics Volume 8 part 1 1986 in a paper by Dr. M. A. Swinbanks.

similar principles are used to perform the remaining possible functions (b) to (e) explained previously on receipt of the appropriate instructions from the central control station 3. The inertial layer 9 is required to enable the lower elements 10 to detect acceleration enabling the integrated circuit to operate the upper layer so as to - 10 ensure zero net pressure and motion in the external fluid resulting from internal sound-generated by the vessel.

The invention is not confined to the precise details of the foregoing example. For instance, the control circuit may be provided in more than one layer. Non-piezo-electric devices may provide sensing and/or controllable elements instead of or in addition to the piezo-electric devices described.

The subject matter of the present application is closely related to that of our copending patent application Nos. 8816190 and 9214993.

Claims

CIAIMS

1. An interface element, for use with a plurality of like elements in an array, the array defining an interface between two media, each element being of laminar form having two major faces and including sensing means, capable of sensing a dist urbance at one of the faces in one of the media, and controllable means capable of responding in such a way as to cause the elements of the interface to simulate the motion of a direct extension of said one of the media, and control means for receiving signals from the sensing means and controlling the controllable means accordingly.

2. An element according to claim 1 in which the integral control means is also arranged to cause the controllable means to suppress the transmission of the disturbance, sensed by the sensing means at one of the major faces across the interface.

3. An element according to claim 1 or 2 in which the integral control means is arranged to cause the controllable means to stabilise or suppress, at the contiguous major force, flow instabilities sensed by the sensing means in one of the media of that face.

4. An element according to any preceding claim in which one or more layers of the laminate comprises a control circuit.

5. An element according to any preceding claim comprising two layers of sensing and/or controllable means separated by an inertial layer.

6. An element according to any preceding claim in which the sensing means and/or the controllable means are piezo-electric.

7. An interface comprising an array of elements each according to any preceding claim comprising a common power supply to the elements.

8. An interface according to claim 7 comprising means for modulating the power supply to provide instructions to the individual elements of the array, or to groups of them.

9. An interface according to claiin 7 or 8 comprising groups of the elements associated with each other and sharing a common control means.

10. An interface according to claim 9 in which each group of elements has means for communication with a neighbouring group of elements.

11. An interface element as claimed in claim I and substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings.

12. An interface comprising an array of interface elements each as claimed in claim

11.

13. A. marine vessel as claimed in claim 1 and comprising an array of interface elements substantially as described with reference to and as illustrated in Figures I and 2 of the accompanying drawings.

I L Amendments to the claims have been filed as follows 1. An interface element, for use with a plurality of like elements in an array, the array defining an interface between two media, each element being of laminar form having two major faces and including sensing means, capable of sensing a disturbance at one of the faces in one of the media, controllable means, and pre-programmed control means for receiving signals from the sensing means and controlling the controllable means to cause the element to simulate the motion at said one face of a direct extension of said one of the media.

2. An element according to claim 1 in which the control means is also arranged to cause the controllable means to suppress the transmission of a disturbance, sensed by the sensing means at one of the major faces to the other major face.

3. An element according to claim 1 or 2 in which the control means is also arranged, when flow instabilities are sensed by the sensing means in one of the media, to cause the controllable means to stabilise or suppress the sensed flow instability.

1-' 4. An element according to any preceding claim in which one or more layers of the laminate comprises a control circuit.

9. An interface according to claim 7 or 8 comprising groups of the elements associated with each other and sharing a common control means.