GB2362447A

GB2362447A - Interface

Info

Publication number: GB2362447A
Application number: GB8816190A
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: 1988-07-07
Filing date: 1988-07-07
Publication date: 2001-11-21
Anticipated expiration: 2008-07-07
Also published as: GB2362447B; GB8816190D0

Abstract

A marine vessel has on its surface tiles (2, fig.1) comprising a number of piezo-electric elements 5, 10. Each element has associated with it an integrated circuit 8 which is programmed so as to cause the elements to modify the acoustic behaviour of the surface of the vessel. This facility enables turbulence to be reduced, acoustic reflections to be cancelled, escape of noise from the vessel to be eliminated, or acoustic signals to be transmitted as and when necessary. Selected elements act as sensors, others as drivers. Elements or groups may receive instructions in situ from control (3, fig. 1). The interface may be used on submarines or aircraft.

Description

2362447 AnInterface between Two Media This invention relates to an

interface between two media. It 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. It could for example be used on the surface of an aircraft. It can be used to suppress unwanted 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. Furthermore, although the invention was made with acoustic effects in mind it could also be of value in other environments for example radio or microwave environments.

This invention provides a interface between two media comprising an array of elements at least some of the elements being sensing elements capable of sensing a disturbance in one of the media and at least some being controllable elements capable of modifying the dynamic properties of the interface, and control means receiving signals from the sensing elements controlling the controllable elements accordingly.

By employing the invention it is possible for the "control means" in each element to behave "intelligently for and 2 - 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. The programming can be such as (a) to cause suppression of reflections of acoustic or other signals from the interface, or (b) to prevent the passage of sound or vibration across the interface, or (c) to stabilise or suppress flow instabilities where one of the media is a fluid, or (d) to transmit acoustic signals into one of the media, or (e) to create deliberate flow instabilities.

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

Where a layered structure is employed the layers is preferably piezo-electric.

electric layer can be used for sensing or modifying disturbances in one of the media.

do however exist for non-piezoelectric accordance with the invention. For example controllable elements could be fluid actuated at least one of This Diezo- for creating or Possibilities devices in each of the acting on known Principles for example using a heating effect or a hydraulic-mechanical mechanism.

- 3 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 connected to each of the elements Where elements different line of elements done by lead could be it is desired to modify the behaviour of in some way, for example to select between functions (a) to (e) explained previously, communication needs to be provided between and a central control station. This could the the some the be way of a separate conductor or conductors connected to all the individual elements. Another possibility, which is perhaps preferred, 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 is to modulate - 4 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 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 interconnection between adjoining "tiles". This i in order that each element connected to-ether durinn a some form of adjoining elements or between nterconnection may be necessary 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 accompanying drawings in which:- Fig. 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 1 of the ship and the water; and a perspective view of an array of elements forming one of a large number of tiles illustrated generally in fig. 1.

between the hul Fig. 2 is Referring firstly to figure 1 there is illustrated marine vessel 1 which in this illustrated example is surface vessel but could in other embodiments be submarine. The part of the hull of the vessel 1 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 6 suppress 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. ultrasonic 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 f igure 1. This comprises an upper layer 4 comprising an array of individual piezoelectric elements 5 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 flow instabilities of the water adjacent to the 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 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. The mathematics relating to the detailed performance of this function is described in the proceedings of the Institute of Acoustics Volume 18 Part I 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 - 8 enabling the integrated circuit to operate the upper layer so as to ensure zero net pressure and motion in the external fluid resulting from internal sound generated by the vessel.

- 9

Claims

1. An interface between two media comprising an elements, at least some of the elements being elements capable of sensing a disturbance in one media and at least some being controllable capable of modifying interface, and contro the sensing elements elements accordingly.

2. An interface according to claim 1 in which control means is constructed and arranged so as to the controllable elements to suppress reflections.

3. An interface according to claim 1 or 2 in which the control means is constructed and arranged so as to cause the controllable elements to prevent passage of sound or vibration across the interface.

4. An interface according to claim 1, 2 or 3 in which the control means is constructed and arranged to cause the controllable elements to stabilise or suppress flow instabilities in one of the media.

5. An interface according to any preceding claim which each element is a layered structure, one or layer comprising a control circuit.

6. An interface according to any preceding claim in which at least some of the elements are piezo-electric.

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

8. An interface according to claim 7 comprising means the dynamic properties array of sensing of the elements of the means for receiving signals from and controlling the controllable the cause - 10 for modulating the power supply to provide instructions to the individual elements, or groups of them.

9. An interface according to any preceding claim 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 according to claim 5, or any other preceding claim when dependent on claim 5. comprising two layers of elements associated with media on respective sides of the interface.

12. A vehicle for use in or on the water comprising an interface in accordance of any preceding claim between its hull and the water.

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

13. A vehicle according to claim 12 for use under water.

14. A marine vessel comprising an array of elements substantially as described.

U 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 redia, and controllable means capable of modifying the dynamic properties of the other face of the element to].-,.,-vent the passage of the disturbance therezt.rough and into the other of the media, and control means for receiving signals from the sensing means and conrolling the controllable means accordingly.

2. An element according to claim 1 in which the control means is also capable of causing the controllable means to modify the dynamic properties of the element, at one of its faces, to suppress reflections sensed by the sensing means, at the same major face.

3. An element according to claim 1 or 2 in which the control means is also capable of causing the controllable means to stabilise the dynamic properties of the element, at one of its faces, to stabilise or suppress flow instabilities, in one of the media, sensed by the sensing means at that face.

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

5. An element according to any preceding claim i 71, comprising two layers of sensing and/or controllable means separated by an inertial layer.

6. An element according to any preceding claim which the sensing means and/or the controllable means 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 claim 7 or 8 comprising groups of the elements associated with each other and sharing a 10.

common control means.

in are 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 substantially as hereinbefore described with reference to Fig. 2 of the accompanying drawings.

12. An interface comprising an array of elements as claimed in claim 11.