GB2285115A

GB2285115A - Missile guiding system

Info

Publication number: GB2285115A
Application number: GB9326426A
Authority: GB
Inventors: Daphne Juliet Knowles
Original assignee: UK Secretary of State for Defence
Current assignee: UK Secretary of State for Defence
Priority date: 1993-12-24
Filing date: 1993-12-24
Publication date: 1995-06-28
Also published as: GB9326426D0

Abstract

A missile aiming system, particularly for use with low level air defence guided missiles, includes a control system 14 in which a basic control law (30, Fig. 2 not shown) is modified (31, 32) according to a range reading. The latter is preferably the range of a target 21 from the system 14 but if this is not available the range of a missile 11 from the system 14 may be used. The operator moves a joystick to cause a target indicator to follow a target image on a screen and movement of the missile is slaved to movement of the joystick. <IMAGE>

Description

AIMING SYSTEMS The present invention relates to hiving systems for low level air defence guided missiles.

A typical low level air defence system operates by a method whereby an operator tracks a target, maintaining a target indicator on the target (by which. in this specification, is meant either the actual target viewed directly through a screen or an image of the target on a display). A missile under the control of the operator has its controls slaved to controls used by the operator to maintain the target indicator on the target as the target moves. This method requires the operator to track the target until the missile makes contact.

Missile aiming systems are required to cope with targets at a variety of ranges. They are typically set up to enable an operator to track a fast moving close range target. To assist in tracking distant targets, where the fine control needed for close range fast moving targets would make tracking difficult, a shaped control law, typically a cubic law, is used. With a cubic law the ratio between target indicator movement and control input varies as a cubic function. In addition, low level air defence missile aiming systems use a further control law containing an overall sensitivity value with positional, integral and differential terms. The effect is to provide a rate control which means that once a force is applied to the tracking controller and then removed the target indicator continues to move at a constant rate until a further force is applied.The tracking controller might be, for example, a joystick, a button control, or a rotatable sphere but will, for convenience, in this specification be referred to as a joystick. When a constant force is applied the target indicator accelerates. It has been found that this arrangement is helpful when targets are always moving.

However even with these control laws it has been found that as the range at which missiles are designed to operate increases accurate tracking at the longest ranges becomes harder for the operator. It has also been found difficult to engage long range airborne head on targets.

According to the present invention an aiming system includes a screen and means for imaging a target on the screen, a target indicator on the screen and joystick means for moving the target indicator, and an operating programme wherein the relationship between joystick movement and target indicator movement is varied according to a range reading.

The range reading will preferably be the target range. However if the aiming system does not include a target range measurement the missile range (which is always available) can be used.

According to another aspect of the invention a method of aiming a missile includes the steps of positioning a target indicator over a target, controlling the position of the target indicator by means of a joystick to maintain the relative position5 of the target and target indicator, manoeuvring of the missile being slaved to movements of the joystick, the relationship between movements of the joystick and of the target indicator being controlled by a control law which includes a variation depending on a range reading.

Some embodiments of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, of which; Figure 1 is a perspective view of a guided missile carrier and aiming system, and Figure 2 shows a shaped control law as typically used in the aiming system.

A missile guidance system (Figure 1) has a transporter 10 carrying a plurality of missiles 11 each of which has its own guidance and control unit 12 which receives instructions from a tracking and transmitting unit 13 also mounted on the transporter 10.

A remote control unit 14 has a screen 15 and a control panel 16 on which are mounted a target indicator movement controller in the form of a joystick 17, and a fire button 20.

In use, when a target 21 is identified the remote control unit 14 is used to manoeuvre the missiles 11 and the tracking and transmitting unit 13 to aim at the target. An image of the target 21 appears on the screen 15 as shown at 21a. An operator 25 positions a target indicator 26 over the target image 21a, and moves the target indicator by means of the joystick 17 until the target indicator 26 overlies the image 23a.

The missiles 11 and tracking and transmitting unit 13 are slaved to move in synchronism with movements of the target indicator 26 on the screen 15.

When the operator 25 is satisfied that he has the target 21a sufficiently located he operates the fire button 20 and fires one of the missiles 11. The tracking and transmitting unit 13 tracks the target 21 and passes signals to the remote control unit 14 where movements of the target 21 cause movements of the image 21a. The controller moves the joystick 17 to keep the target indicator 26 positioned on the image 21a. Signals corresponding to joystick input demands are sent to the transmitting unit 13 which signals the guidance and control unit 12 of the missile 11 so guiding the missile 11 until it meets the target 21.

The tracking and transmitting unit 13 also monitors the range of the target 21 and passes a range signal to the control unit 14.

The control law conventionally used in this type of targeting is shown at 30 in Figure 2. According to this law movements of the target indicator movement controller 17 results in movement of the target indicator 26 according to a cube law plus a control law containing an overall sensitivity value with positional, integral and differential terms.

According to the invention the basic relationship 30 is modified according to the range of the target 21 so that it is finer (that is, movement of the target indicator is greater for a given joystick input demand), as shown at 31, when the target is at short range and coarser, as shown at 32, when the target is at long range.

Some missile guidance systems do not measure the target range.

For such systems the range of the missile can be used. This is always known (if it is not measured it will be known from the performance of the missile and the time of firing).

In performance tests it has been found that using these range measurements to adjust the basic control law a controller has had much greater success in tracking the target in the critical phase of the engagement, that is just before missile/target impact. Hit rate has been most successful using target range, but has also been significantly improved using the missile range.

It will be realised that the particular missile control system described here is for example only. The aiming system of the invention is equally applicable to other control systems, such as those where the operator views targets directly through a sight. Also the image may be real or thermal.

It will, of course, be realised that a missile guidance system as described above with reference to Figure 1 might be adapted to switch between the operating system as described and other operating systems. For example a missile having both self guidance and controller guidance systems might be fired by one of the self-guidance firing schemes- for example that described in the Applicant's co-pending Application GB 9206829- and then switched to the system described above so that a controller can continue to track the target and be in a position to take over control should the self-guidance system fail.

Claims

What is claimed is: 1. An aiming system including a screen and means for imaging a target on the screen, a target indicator on the screen and joystick means for moving the target indicator, and an operating programme wherein the relationship between joystick movement and target indicator movement is varied according to a range reading.
2. An aiming system as claimed in Claim 1 wherein the range reading is the range from the system of a target.
3, An aiming system as claimed in Claim 1 wherein the range reading is the range from the system of a missile.
4. A method of aiming a missile including the steps of positioning a target indicator over a target and controlling the position of the target indicator by means of a joystick to maintain the relative positions of the target and target indicator, manoeuvring of the missile being slaved to movements of the joystick, the relationship between movements of the joystick and of the target indicator being controlled by a control law which includes a variation depending on a range reading.
5. An aiming system substantially as described herein with reference to Figures 1 and 2 of the accompanying drawings.
6. A method of aiming a missile substantially as described herein with reference to Figures 1 and 2 of the accompanying drawings.