Control of De-spun Flying Munitions Vehicles
Submitted to:
Dr. B.C. Chang
The Senior Design Project Committee
Mechanical Engineering and Mechanics Department
Drexel University
Team Number:
MEM-13
Team Members:
Amanda N. Annesi Mechanical Engineering
Timothy D. O’Hara Mechanical Engineering
Jason F. Gomes Electrical Engineering
Louis M. Bocchicchio Computer Engineering
Submitted in partial fulfillment of the requirements for the Senior Design Project
November 28th, 2005
Abstract
Research is currently being conducted on controlling advanced guided munitions technologies by the Army Research Laboratories and other defense contractors. Projectiles currently lack precision and often miss targets because of a lack of on board control. Last year’s senior design team was able to partially control the de-spin portion of a rotating body in a one degree of freedom system. There are currently no accurate prototypes have been built or modeled to encompass the complexity of the 3-degree system. We propose to build a fully functional partially de-spun projectile that can be controlled in a 3 degree system. To accomplish our mission we will create an accurate design and mathematical model of the projectile. We will be using an already-built gyroscope as our testing apparatus. We will also utilize electrical components that will be used for our controller. The outcome of the project will be measured by conducting several testing requirements that involve the controller’s performance in a three dimensional space setting.
Executive Summary
The objective of this project is to build a fully functional partially de-spun projectile that can be controlled in a 3 degree system. We will fulfill our objective by first creating an accurate design and mathematical model of the projectile. We will be using an already-built gyroscope as our testing apparatus which is provided by the Army Research Laboratory. The gyroscope contains the idea of a gimbal but also includes a motor that provides the spin and allow the projectile to move about 3 separate axes simultaneously. There will also be electrical components that will be used for our controller. These components include a programmable DSP microprocessor, sensors such as GPS receivers, magnetometers and accelerometers, motors, batteries, and a programming model. We will be using Code Composer Studio and the C programming language for the programming of the DSP microprocessor and the integration of the various sensors into the microprocessor. Additional research will need to be performed throughout the design process as we encounter new unexpected difficulties. We will develop our controller based on similar controllers released in the industry along with researching the behavior of a ballistic projectile in three dimensions to develop the appropriate model. We will begin programming in C once the optimal controller has been achieved. We will be using Simulink to design our project and test it before actually building it and Labview to run and simulate the experiment on the computer so that we can obtain results and characteristics that we can implement into the actual projectile. The outcome of the project will be measured by conducting several testing requirements that involve the controller’s performance in a three dimensional space setting.
Table of Contents
Abstract………………………………………………………………………………….... 2
List of Figures and Tables………………………………………………………………… 3
I. Introduction…………………………………………………………………………… 1
A. Problem Background…………………………………………………………. 1
B. Problem Statement…………………………………………………………… 1
C. Project Constraints and Criteria for Solution………………………………… 2
II. Methods for Solution………………………………………………………………… 2
A. Phase 1: Research and Project Conceptualization……………………………. 2
B. Phase 2: Design and Experimentation………………………………………... 4
C. Phase 3: Final Design and Prototype Synthesis……………………………… 6
D. Alternative Solutions………………………………………………………….6
III. Project Management Timetable……………………………………………………… 7
IV. Economic Analysis…………………………………………………………………… 8
V. References and contacts……………………………………………………………… 10
Appendix A: Task Tree (Project management organization chart)
Appendix B: Gantt Chart (Scheduling)
Appendix C: Block Diagram of project
Appendix D: Pictures of sensors
Appendix E: CAD drawing of projectile
Appendix F: ProE drawing of gimbal
List of Figures
Figure 1: Gyroscope………………………………………………………………………3
List of Tables
Table 1: Engineering Design Costs……………………………………………………….8
Table 2: Manufacturing Costs…………………………………………………………….8
Table 3: Labor/Utilities Costs…………………………………………………………….9
Table 4: Estimated Prototype Net Design Total………………………………………….9
Introduction
Problem Background
Research on advanced guided munitions technologies is being conducted by the Army Research Laboratories in addition to many other defense product contractors and military installations. The U.S. Army’s Excalibur1 projectile was designed specifically to be guided in-flight. It contains a GPS chip, a data processor chipset, and an IMU incorporating a Micro Electro-Mechanical System (MEMS). Once in flight, it deploys canards controlled by a drive guidance unit which makes use of the navigation data derived by the GPS/IMU. The canards must oscillate at a rate in the range of 300 Hz. This is a valuable solution for controlling projectiles but lacks the precision, maneuverability and reliability that would be provided by mounting canards on a de-spun segment of the projectile.
The Naval Surface Warfare Center, Dahlgreen Division, and a large military contractor conducted a guided flight of the Extended Range Guided Munitions (ERGM).2 They launched the ERGM from an Mk45 Mod 4 gun system. Guidance of the projectile was achieved through the use of tactical propellant charges detonated as the projectile descends to earth.
Fractional advances towards de-spin of munitions vehicles have been made by one of last years senior design teams. The design included a control system to de-spin a portion of a rotating body in a one degree of freedom system. This, however, has yet to be accomplished in a three degree system. After conducting an in depth search using Drexel Library resources, we concluded that no accurate prototypes have been built or modeled to encompass the complexity of the 3-degree system we are proposing to design and build.
Problem Statement
The military needs more accurately controlled projectiles to reduce the number of rounds required to defeat a given enemy threat. Current projectiles are lacking advanced precision guidance systems and have been known to miss targets due to a lack of on board control. Contributing factors to these inaccuracies include natural elements acting on the projectile once it is fired, manufacturing defects in the munitions themselves and worn gun tubes from which the projectiles are fired. These detrimental forces can be overcome by developing an accurate and reliable closed loop control system.
Project Constraints and Criteria for Solution
The primary constraints of our project are created by the gyro testing apparatus provided by ARL. Our final design must properly interface with this testing fixture. The criteria that will be used to determine if our solution is acceptable are as follows. The final solution will contain a fully functional partially de-spun projectile (Appendix C) that contains internally mounted sensors and a programmed DSP microprocessor that determine the motion and position characteristics of the projectile and respond accordingly. The projectile will undergo a series of tests and modifications to optimize the controller performance. If the projectile can be accurately controlled in a three dimensional space setting then this will deem our solution acceptable.
Methods for Solution
Phase 1: Project Conceptualization
Our project will be a continuation of last year’s accomplishments. However, the controller will be much more complex due to the added degrees of freedom and additional sensors needed to accurately describe position, velocity and accelerations to the projectile. Because of this, we will need an accurate design and mathematical model of the projectile. Our project also requires a unique testing apparatus, the gyroscope as seen below in Figure 1.
Figure 1: Gyroscope
The gyroscope incorporates the idea of a gimbal but also contains a motor that provides the spin. The gimbal aspect is very important as it allows the projectile to move about 3 separates axis simultaneously. A gimbal will allow us to simulate complete freedom of the projectile as it is able to pitch, roll and yaw.
The final components that our project rest on is the electrical components that will be used for our controller. The components will include the DSP microprocessor, sensors, motors, batteries, and a programming model. We will be investigating many different types of sensors such as GPS receivers, magnetometers, accelerometers and integrate them with DSP microprocessors. There already exist a plethora of applications using these electronic components. We plan to use previous research in combination with the unique characteristics of our project to guide us towards the solution.
In the event that the electrical components for our project are not available, we should not have a problem finding suitable replacements because all of the components can be purchased off the shelf of any electronics store.
Additional research will need to be performed throughout the design process as we encounter new unexpected difficulties. Once we build the prototype projectile, we will need to use information available from similar controllers to give us insight into the best way of developing our controller. We need to research behavior of a ballistic projectile in three dimensions to develop the appropriate model. Once we have achieved the optimal controller in simulation we will begin programming. In order to properly program the DSP microprocessor, additional research on control theory, analog to digital conversion and pulse-width modulation will be required. Finally when we successfully de-spin the front segment of the projectile, we will begin to explore possibilities for incorporating and powering a guidance control mechanism in our design.
Phase 2: Design and Experimentation
In order to complete this project successfully our main advisor, Dr. Bor-chin Chang, will be offering us technical expertise and referring us to other experienced engineers to aid in our design. Dr. Harry Kwatny, our co-advisor, will be providing us with additional guidance for developing the systems controllers and Dr. Prawat Nagvajava, another co-advisor, will be offering assistance to the electrical and computer engineers in the programming of the microprocessors. Another asset to our project is Mark Costello from Oregon State University. He will help give us guidance through his research done with similar elements of autonomous controls and controls of projectiles. David Hepner from the Army Research Laboratory will be giving us assistance through guidance and through the use of the Army Research Laboratory facilities. He will also be providing us with prefabricated parts for the projectile including a micro processor, sensors, batteries and a projectile shell.
An important aspect in completing this project is the technical skills that the group holds. The mechanical students have had classes and are familiar with dynamics and control systems. Using their knowledge, they will be able to model equations that represent the movement of the projectile. The electrical and computer engineering students will provide knowledge in theory of controls, dynamic systems and stability, C programming, digital signal processing, and circuit design. They will be able to use the information from the mechanical engineering students to adjust projectile movement.
In order to accomplish these tasks, we will use several computer programs. To formulate transfer function and equations for the projectile motion, we will use MatLab and MatLab’s Simulink. Simulink will allow us to design our project and simulate it before actually building it. We can vary our controller input gains to achieve a desired overshoot, settling time and period of oscillation. Labview will also be used to run and simulate the experiment on the computer so that we can obtain results and characteristics that we can implement into the actual projectile. For the designs of the gimbal and the projectile, we will be able to utilize computer aided design software such as ProEngineer. On the electrical side, Code Composer Studio will be used to program the microprocessor and Orcad will be used for circuit board design
Primarily, Drexel University will provide most of the resources for research and assembly for our project. Much of our research will come from publications held and found through the Hagerty Library. Additionally, we will utilize data from past design projects. Through the university, we will be able to utilize the machine shop for some construction and we have a room to work in the undergraduate lab as provided to us by Dr. Chang.
To test the de-spun segment of the projectile, we will adjust gyroscope motor speeds to see if the front end will be able to adjust accordingly. We plan to allow the projectile to spin freely and activate the controls after a small period of time has elapsed so we can see the difference between a fully spinning projectile and a partially de-spun projectile.
Testing will occur throughout the project in the Mechanical Engineering and Mechanics undergraduate laboratory. Most of the control testing will involve the gyroscope so that the projectile movement can easily be seen and measured. Accelerometers and magnetometers will be used to determine important flight characteristics of the projectile as it incurs rotation about its axis when it is fired. The Army Research Laboratory will provide us with much information and other testing facilities as seen fit to test our design.
Phase 3: Final Design and Prototype Synthesis
Using a controlled DC motor, the front half of the projectile containing the sensor suit needs be stabilized relative to ground (i.e. eliminate it’s angular motion). We will build a controller that uses the inputs from a combination of accelerometers and magnetometers to determine the necessary input voltage to de-spin the front segment. Once we determine the proper design and input gains for the controller, we will use this information to program the microprocessor. When stability is achieved in the front half of the projectile, a number of different navigation control systems will be able to accurately control the heading of the projectile.
Data storage is a major issue for this project. Once we come up with a final design, we have to make sure our prototype will allow us to acquire data so that we may use it to make improvements to the system as well as document our success. The Army Research Laboratory will provide us with a J-tag interface which will allow us to test the projectile and acquire the data after the test is finished. This methods seems to be the best option to us because is isn’t very expensive and will not take up a large amount of space inside the projectile. Other methods of data acquisition will be discussed in the alternative solution section.
The autonomous control of a projectile does not pose any environmental nor social impacts.