MISSILE COMMAND A REAL TIME MISSILE SYSTEM WITH EMBEDDED GUIDANCE CONTROL USING DIJKSTRA’S ALGORITHM R.Arun (Student Member IEEE), M.Sriram(Student Member IEEE) E.C.E Department, Pre Final Year, Velammal Engineering College

Abstract:

This paper deals with the design of a Real Time Missile System embedded with Shortest Path Algorithm concept, which helps for its guidance. The specialty of this paper is that each missile will have their own radar and can be completely automatic i.e. “the power to think on its own”. Every missile launched will hit the target with 100% certainty. In the missile system we use the “Key Concepts”.


INTERRUPT SERVICE ROUTINE




SHORTEST (DIJKSTRA'S)




RDBMS

PATH

ALGORITHM

Main working of this missile system is summarized as follows. 1. Ground based Radar sweeps the sky for threats and if found, it sends the target’s information to the missile which is stored in a small database inside it. 2. Interrupts are generated at frequent intervals of time within the launched missile. Whenever interrupts are generated, radar inside the missile scans for the target’s new position and the Shortest Path Algorithm between the missile’s current position and target is found out. The missile then takes this path. 3. Step 2 is repeated until the target is hit. As soon as missile hits the target the information about the type of the target, the time of explosion etc. are sent to the remote database server by the operator. This system is considered to be the improved version of the PATRIOT ADVANCED CAPABILITY (PAC3) missile, as the missile here are completely automatic. This system comes under the category HARD REAL TIME SYSTEM. The missile is designed to chase the target until all of its energy is exhausted. This picture explains the detailed working of the missile system.

1.

Introduction

Till date only human beings are responsible for finding and identifying the target, appropriately aiming the target and triggering it hoping that their aim would be accurate and hit their target, but this is not certain. There is always the chance that the missile will blast in some other region. But this design of missile system provides a 100% chance of hitting the target. This missile system has a remarkable goal. It is designed to detect, target and then hit an incoming missile. This is because the missiles are transmitted automatically and works with no human intervention. Moreover the missile system proposed here could detect an incoming missile flying at Mach 5 and destroy it. The idea is that the missile to chase towards the incoming target and hit, so that the incoming missile is completely destroyed. This feature makes it move effective against chemical and biological warheads because they are destroyed well away from the target. 1.1 Advantages over PAC missile

The ground-based radar guides the PAC missiles where the missiles fly up to an intercept point and blast. The target's position is updated by the ground based radar. But in this system, the missiles are guided by itself with the help of inbuilt radar. The main advantage

of this scheme is that the ground based radar can be exclusively used for scanning for external targets wherein in PAC; the ground based radar has the burden tracking the target's position also. 2.

Block Diagram

How it is used? Here we use a PIC (Peripheral Interface Controller) micro-controller. One of the timers of the PIC microcontroller can be used to generate interrupts after some stipulated time. This time could be dynamically configured according to the type and speed of incoming target. Here, the ISR contains the code for finding the shortest path between the missile and the target. Initially in the ISR we disable all the interrupts as we do not want any further interrupts to be generated until ISR is completed. Finally before transferring the control to the main function we re-enable them. Since the ISR is invoked at frequent intervals of time, the shortest path algorithm will be executed repeatedly and hence the missile keeps on tracking the target and finally hits it. Thus the trajectory of the missile keeps on changing according to the target. In the main function we have a delay program for the proper execution of the ISR. The time duration for this delay loop is also dynamically changed according to the type and speed of the target. 3.2 Shortest Path Algorithm: What is it? To be precise, this algorithm is used to find the shortest path between any two given points. How it is used?

3.

Philosophies

The following conceptual philosophies are interlinked and embedded into the missile system.


INTERRUPT SERVICE ROUTINE




SHORTEST PATH (DIJIKSTRA’S)




RDBMS

ALGORITHM

3.1 Interrupt Service Routine What are Interrupts? Interrupts allows a programmable computing device which is executing its task to respond other external requests for attention or service on a demand basis. When the interrupt signal is activated the internal control circuit of the programmable device produces a CALL to a predetermined memory location. This memory location where the subroutine starts is referred to as ‘vector location’ and such interrupts are called “vectored interrupts”. Interrupt Service Routine (ISR) is the routine (procedure) which gets executed when its corresponding interrupt is triggered.

When an interrupt is generated, the inbuilt radar of the missile sweeps the sky for the particular target stored inside the missile's database. When it finds the target, it sends the target's position and the missile's current position as a parameter to the shortest path algorithm. This algorithm processes it and finds the shortest path between them. Then the missile moves in that direction. Thus the missile hits the target quickly. Thus the missile will chase the target and hit the enemy missile. Hence the name "Trigger to hit missile”. We use Dijkstra’s shortest path algorithm here. Change of Direction Here we use the component DIGITAL SCENE MATCHING AREA CORELATION (DSMAC).

It consists of a camera and image corelator which helps in finding the target and is especially useful when the target is moving. In addition to controlling the fins, the guidance control system controls the vanes, which are present in the rear of the missile. The vanes divert the hot gases from the missile's motor towards the desired direction. For e.g. when the missile wants to turn right, the vanes divert the gases towards right, the thrust pushes the rear of the missile towards left and front portion moves towards right. The angle to which the missile should be turned is controlled by the PIC micro-controller.

The schema for this purpose can be written according to the design of the missile system. A sample result set data for the Missile schema:

3.3 RDBMS Concepts: What is DBMS? Database Management has evolved from a specialized computer application to a central component of a modern computing environment. This concept includes aspects of database design and database system implementation in the “Trigger to Hit” missile system. The primary goal of a DBMS is to provide a way to store and retrieve database information that is both convenient and efficient. To say it apt, the DBMS in our missile system rather than providing convenience it provides comfort and ecstasy.

How it is implemented? The four missiles loaded into the launcher will each be having identification. The launcher is already connected to a computing system, which has the system software. This software application should be developed such it supports efficient database connectivity. Standards such as ODBC and JDBC were developed for database connectivity. In our missile system, any launcher that uses the ODBC or JDBC standards can connect to any server that provides the interface. The launchers in the Warfield have the JDBC standards and it returns a result set data to the central database server. The schema of the database will be previously designed in consultation with military officials. As soon as the missile is exploded the launcher, which has a standard for database connectivity, performs an insert operation and data about the missile that has been launched is fetched in the central database server. As soon as the database instance is fetched appropriate message with needed information from the database is being sent to the users who have the authentication to access the database. The schema for the parent table of our missile system is given below: Misssile_schema(missile_no,missile_name, time_of_projection, time of Explosion, type_of_missile hit) The insert operation for this schema takes place only after the missile has been launched. But prior to this operation, the database system has to have information about the missiles in hand.

4.

Radar:

The Radar is built inside the missile is MINIATURE ALTIMETER RADAR (MAR). This unit, which was designed primarily for UNMANNED AIR VEHICLE (UAV’s), weighs mere 400 grams and is only 150mm*8mm*54mm in size and has an operating frequency of 4.3GHz. The unit’s size and weight make it an ideal choice for this missile system. It provides the accurate low level positioning (1.5mm – 700mm) so vital for successful surveillance, target location, low-level target drone operation and recovery. The radar’s signal are processed and fed as a parameter to Shortest Path Algorithm. It also helps in determining the trajectory, speed and head of the incoming target. The ground-based radar can have a traditional image of a radar antenna that is the rotating parabolic antenna seen on top of airport control towers and aircraft carrier. 5.

Radar Signal Processing

This is the block diagram for the entire process. This diagram shows how the signals from the radar are processed. In the ground station, the signals from the radar are preprocessed then transformed to frequency domain. The input image stream is the image of the incoming missile i.e. the target. The copies of the spectral image are then multiplied in parallel by the filter correlation matrices for say 3 classes of targets of interest. The result is then inverse frequency domain transformed

to give the correlated surface maps associated with each of the 3 classes. The strongest correlation peaks for each image class are compared with the reference classes to yield class closeness measures. The signals of the inbuilt radar i.e. MAR are also processed similarly. 6.

Working of the Algorithm:

the evader, ye and ze span the normal plane to xe and the natural curvatures ue and ve are the controls for the evader. We model the pursuer and evader as point particles, and use natural frames and curvature controls to describe their motion, because this is a simple model for which we can derive both physical intuition and concrete control laws. Thus the algorithm fixes the frame for a point in the three dimensional space.

6.1 Frame fixing in the three dimensional space:

Lets assume that the purser is our missile which is on its way to hit the target (evader) now their position in a three dimensional space is given by the following figure.

From the figure the trajectories for the pursuer and evader, and their respective natural frames is found. The position of the pursuer is rp, and its natural frame is {xp, yp, zp} , where xp is the unit tangent vector to its trajectory, and { yp, zp } span the corresponding normal plane (and similarly for the evader). The pursuer moves with speed vp, and the evader with speed ve, by

Now after getting the 3 dimensional paths it converts the obtained three dimensional images into corresponding voltages and thereby its assigns the cost for a particular path based on the voltage level and calculates the shortest path hence. Now in the below figure we can see a 3D- path, the corresponding voltage conversions are also indicated in the same graph.

A sample processed signal from the radar is shown in the figure

Where rp is the position of the pursuer, vp is the speed of the pursuer, xp is the unit tangent vector to the trajectory of the pursuer, yp and zp span the normal plane to xp. The up and vp are the controls for the pursuer. Similarly, the dynamics of the evader are

Where re is the position of the evader, ve is the speed of the evader, xe is the unit tangent vector to the trajectory of

The sets of all directed optimal paths from the MAR is obtained for the same realization of quenched randomness in the lattice. The shortest path which is the minimal voltage path among all the paths is shown by a RED LINE. The interesting point to note here is that only the shortest path is calculated and yet the Target is not reached.

6.2 The Dijkstra’s Algorithm:

Given a graph, G, with edges E of the form (v1, v2) and vertices V, and a source vertex, s dist: array of distances from the source to each vertex prev: array of pointers to preceding vertices i : loop index F : list of finished vertices U : list or heap unfinished vertices /* Initialization: set every distance to INFINITY until we discover a path */ for i = 0 to |V| - 1 dist[i] = INFINITY prev[i] = NULL end /* The distance from the source to the source is defined to be zero */ dist[s] = 0 /* This loop corresponds to sending out the explorers walking the paths, where * the step of picking "the vertex, v, with the shortest path to s" corresponds * to an explorer arriving at an unexplored vertex */ while(F is missing a vertex) pick the vertex, v, in U with the shortest path to s add v to F for each edge of v, (v1, v2) /* The next step is sometimes given the confusing name "relaxation" if(dist[v1] + length(v1, v2) < dist[v2]) dist[v2] = dist[v1] + length(v1, v2) prev[v2] = v1 possibly update U, depending on implementation end if end for end while

7.

Principles Used in Other Missiles

1. FIRE AND FORGET 2. INERTIAL NAVIGATION SYSTEM

1.1 FIRE AND FORGET PRINCIPLE

The missile designed with principle has a seeker which is analogous to a CCD in a video camera. It has an array of sensors, which generate electrical energy when exposed to IR light given off hot bodies. Whichever sensor receives the highest energy, the missile will take that path. Hence the missile would home in on the target’s own emitted energy, rather than reflected radio energy, the pilot could fire and forget – that is he could launch the missile and get cleared. The famous Brahmos and Astra missiles are designed using this principle. Disadvantages: In the place of radar equipment, which we use in the “trigger to hit” missile, it would use a relatively small heat sensing photo voltaic cell to ‘see’ the target. A major disadvantage is that due to the advancements in technologies many aircrafts have been designed to prevent the emission of IR. Thus these types of targets will not be detected by the missiles. Also consider the following scenario. Two aircrafts are approaching and consequently two missiles are launched by the host. Suddenly if one aircraft hides behind the other, the missiles will not be able to detect the hidden aircraft as the energy from it would be less. Hence the hidden aircraft would escape and the host will be attacked. How trigger to hit overcomes this fault? In the missile system designed, each missile is designated it own target before launching itself. Thus in all the above cases this missile will destroy all the incoming targets immaterial of their position. 2.1 INERTIAL NAVIGATION SYSTEM

(INS)

It’s a self-contained unit that is located within an aircraft or rocket. In this guiding principle, the missiles are programmed with the initial and final position. Only the path to the destination can be changed. An INS measures only movement; it does not measure airspeed or wind velocity. The movement is translated into speed, direction and distance. Disadvantage: In this system the destination is already fixed, hence the missile will not hit the target, if the target moves from its initial position. Moreover INS decreases over time. The

farther the vehicle with the INS travels, the less accurate it becomes. How trigger to hit overcomes this fault? In this missile system, the missiles will chase the target and destroy them. Hence there is 100% certainty that the triggered missile will hit the target. 8.

Working in brief

The above-described concepts are brought into a nutshell and the overall working our missile system is explained in brief:


Radar sweeps the sky for threats. If an incoming object is found, the radar helps determine if it is a missile, cruise missile, fighter jet or a remotely piloted vehicle.




Detect a potential target. It then sends the target’s information to the missile, which is stored in a small database inside it.




Determine the trajectory, speed and heading of the incoming target and Provide information to identify the target. Ideally the radar provides enough information to determine whether the target is a friend or a foe.




Launcher points and fires a missile, which is shipped ready to launch in a canister. (The launcher can be remotely located from the radar).




As the missile is flying, interrupts are generated, inbuilt radar is scanned for the target and the shortest path between the missile and the target is found and the missile moves in that direction.




It continues to track the incoming missile.




Finally it hits the target. Then the operation with the database server is performed.

9.

Simulation and Result

The simulations are done in TACTICAL ENGAGEMENT SIMULATION SOFTWARE 4.0.Which is mainly used for defense purpose simulations. Test data’s were given, frames are fixed and locking of the radar signal is also observed. The following were the results observed.

10. Flow chart explaining the Target Locking

13.

References

[1] Sandeep Neema, Ted Bapty, Jason Scott,“Development Environment for Dynamically Reconfigurable Embedded ACS Tools Systems”,International Conference on Signal Processing Applications and Technology (ICSPAT99),Orlando, Florida. [2] A. Mahalanobis, B.V.K. Vijaya Kumar, and S.R.F. Sims, “Distance-classifier correlation filters for multi-class target recognition”, APPLIED OPTICS, Vol. 35, No. 17, pp3127-3133, 10 June 1996. [3] Jason Scott, Ted Bapty, Sandeep Neema,” Runtime Environment for Dynamically Reconfigurable Embedded Systems”, International.

11. Disadvantages

Every new technology invented will have its own dark sides. Our trigger to hit missile system is not an exception from this. The trigger to hit missile system proposed may have a chance of hitting a fighter jet of its home country due to misidentification. This is not very prone to occur but steps will be taken in future, such that these casualties do not occur. I.e. it can’t identify between friend and a foe. The advanced development in radar technology can surely prevent this from happening. 12. Conclusion

Advances in technology have given us greater control over the material world and improved our standard of living. The missile system resented here can be used in both, for constructional as well as destructive purposes. It is in our hands to bring it in the way in which we desire. To bring our nation to the height of horizons our missile system can be one of the steps to achieve it.