INTERACTING MULTIPLE MODEL SEEKER FILTER FOR TRACKING EVASIVE TARGETS

Seeker filter is an important subsystem in modern homing guidance system of advanced intercepting missiles. Seeker filter design for homing guidance requirements are highly demanding and challenging. Very low filter lag, high noise attenuation are some of the challenges that need to be addressed. This paper presents an interacting multiple model augmented extended Kalman filter (IMM-AEKF) design to operate as seeker filter in close loop homing guidance of an interceptor to track evasive targets. The performance of the seeker filter is verified with six degree of freedom interceptor-target engagement simulation with seeker filter in guidance loop of the interceptor. Different filter performance criteria have been used to verify the performance of the seeker filter. The seeker filter efficiently handles the various seeker noise and provides a smooth estimate of target states to generate guidance command for intercepting missile. The miss distance achieved is within the acceptable limits

Guidance and control for defense systems against ballistic threats

A defense system against ballistic threat is a very complex system from the engineering point of view. It involves different kinds of subsystems and, at the same time, it presents very strict requirements. Technology evolution drives the need of constantly upgrading system’s capabilities. The guidance and control fields are two of the areas with the best progress possibilities. This thesis deals with the guidance and control problems involved in a defense system against ballistic threats. This study was undertaken by analyzing the mission of an intercontinental ballistic missile. Trajectory reconstruction from radar and satellite measurements was carried out with an estimation algorithm for nonlinear systems. Knowing the trajectory is a prerequisite for intercepting the ballistic missile. Interception takes place thanks to a dedicated tactical missile. The guidance and control of this missile were also studied in this work. Particular attention was paid on the estimation of engagement’s variables inside the homing loop. Interceptor missiles are usually equipped with a seeker that provides the angle under which the interceptor sees its target. This single measurement does not guarantee the observability of the variables required by advanced guidance laws such as APN, OGL, or differential games-based laws. A new guidance strategy was proposed, that solves the bad observability problems and returns satisfactory engagement performances. The thesis is concluded by a study of the interceptor most suitable aerodynamic configuration in order to implement the proposed strategy, and by the relative autopilot design. The autopilot implements the lateral acceleration commands from the guidance system. The design was carried out with linear control techniques, considering requirements on the rising time, actuators maximum effort, and response to a bang-bang guidance command. The analysis of the proposed solutions was carried on by means of numerical simulations, developed for each single case-study

Analysis of the Optimal Frequency Band for a Ballistic Missile Defense Radar System

In this paper, we consider the anti-attack procedure of a ballistic missile defense system (BMDS) at different operating frequencies at its phased-array radar station. The interception performance is measured in terms of lateral divert (LD), which denotes the minimum acceleration amount available in an interceptor to compensate for prediction error for a successful intercept. Dependence of the frequency on estimation accuracy that leads directly to prediction error is taken into account, in terms of angular measurement noises. The estimation extraction is performed by means of an extended Kalman filter (EKF), considering two typical re-entry trajectories of a non-maneuvering ballistic missile (BM). The simulation results show better performance at higher frequency for both tracking and intercepting aspects

좁은 화각을 갖는 스트랩다운 탐색기를 위한 유도기법

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2013. 8. 최진영.New guidance laws are proposed to solve the problem of when a missile is equipped with a strapdown seeker instead of a gimbaled seeker. The strapdown seeker has advantages of relatively simple implementation compared to a gimbaled seeker, and it can eliminate frictional cross-coupling significantly save on costs. There have been many studies to enable guided missiles to use strapdown seekers, but they have several weaknesses, such as measurement error caused by scale factor error, radome errors, glint noise, narrow field-of-view (FOV), and so on. Among these weak points, focus is centered on the narrow FOV of the strapdown seeker. A hybrid guidance (HG) law is proposed to maintain the lock-on condition in spite of the narrow FOV of the strapdown seeker. The proposed HG law consists of two guidance phases, which assume operation at a switching boundary. In the first phase, the proportional navigation guidance (PNG) law is applied during the time when the look angle is inside the switching boundary. For the second phase, when the look angle is outside the switching boundary, a new guidance law is derived to keep the look angle within the FOV by employing a Lyapunov-like function based on sliding-mode control methodology. The appropriate determination of the switching boundary is an important issue. The idea behind selecting the switching boundary is to use the PNG law as much as possible, and to make the missile stay in the lock-on condition. A lock-on guidance (LOG) is proposed as another approach to solve the problem of narrow FOV, based on the concept of the pursuit guidance (PG) law. In order to derive the LOG law, we use a Lyapunov-like function based on the sliding-mode control methodology. An advantage of the LOG law is that a missile guided by the LOG law can intercept a target with a very narrow FOV of the strapdown seeker. Because such a seeker often has to be implemented for more accurate measurements, this kind of guidance law is needed to prepare for such a situation. The LOG law is simple and has good performance against a target with high speed.Abstract i Contents iii List of Figures vi List of Tables x Chapter 1. Introduction 1 1.1 Background and Motivations 1 1.2 Contents of the Research 6 Chapter 2. Preliminary Survey 10 2.1 Survey on Guidance Laws 10 2.1.1 Classical Guidance Laws 10 2.1.1.1 Pursuit Guidance Law 12 2.1.1.2 Constant Bearing Course Guidance Law 13 2.1.1.3 Line-of-Sight Guidance Law 13 2.1.1.4 Proportional Navigation Guidance Law 16 2.1.2 Modern Guidance Laws 23 2.1.2.1 Optimal-Control-Based Guidance Law 24 2.1.2.2 Predictive Guidance Law 27 2.1.2.3 Game-Theory-Based Guidance Law 30 2.1.2.4 Sliding-Mode-Control-Based Guidance Law 31 2.1.3 Summary 32 2.2 Survey on Missile Seekers 33 2.2.1 Gimbal Seeker 34 2.2.2 Strapdown Seeker 35 2.2.3 Summary 36 2.3 Remarks and Discussions 37 Chapter 3. The Proposed Guidance Laws 40 3.1 Hybrid Guidance Law 40 3.1.1 Problem Statement 41 3.1.2 The Overall Scheme 46 3.1.3 Guidance Law for the First Phase 48 3.1.4 Guidance Law for the Second Phase 48 3.1.5 Switching Boundary Estimation 50 3.2 Lock-on Guidance Law 56 3.2.1 Problem Statement 57 3.2.2 The Overall Scheme 62 3.2.3 Derivation 64 Chapter 4. Simulation Results 70 4.1 Hybrid Guidance Law 70 4.1.1 Non-maneuvering Target 70 4.1.2 Maneuvering Target 76 4.2 Lock-on Guidance Law 85 4.1.1 Non-maneuvering Target 85 4.1.2 Maneuvering Target 96 4.3 Comparison of Hybrid Guidance Law and Lock-on Guidance Law 105 Chapter 5. Conclusions 109 5.1 Concluding Remarks 109 5.2 Further Study 111 Bibliography 112 국문초록 123Docto

Suboptimal guidance with line-of-sight rate only measurements

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76681/1/AIAA-1988-4066-823.pd

Adaptive Robust Guidance Scheme Based on the Sliding Mode Control in an Aircraft Pursuit-Evasion Problem

In this chapter, a robust guidance scheme utilizing a line-of-sight (LOS) observation is presented. Initial relative speed and distance, and error boundaries of them are estimated in accordance with the interceptor-target relative motion kinematics. A robust guidance scheme based on the sliding mode control (SMC) is developed, which requires the boundaries of the target maneuver, and inevitably has jitter phenomenon. For solving above-mentioned problems, an estimation to the target acceleration’s boundary is developed for enhancing robustness of the guidance scheme and the Lyapunov stabilization is analyzed. The proposed robust guidance scheme’s brief characteristic is to reduce the effect of relative speed and distance, to reduce the effect of target maneuverability on the guidance precision, and to strengthen the influence of line-of-sight angular velocity. The proposed scheme’s performances are validated by the simulations of different target maneuvers under two worst-case conditions

A Three-Dimensional Cooperative Guidance Law of Multimissile System

In order to conduct saturation attacks on a static target, the cooperative guidance problem of multimissile system is researched. A three-dimensional guidance model is built using vector calculation and the classic proportional navigation guidance (PNG) law is extended to three dimensions. Based on this guidance law, a distributed cooperative guidance strategy is proposed and a consensus protocol is designed to coordinate the time-to-go commands of all missiles. Then an expert system, which contains two extreme learning machines (ELM), is developed to regulate the local proportional coefficient of each missile according to the command. All missiles can arrive at the target simultaneously under the assumption that the multimissile network is connected. A simulation scenario is given to demonstrate the validity of the proposed method

Optimal proportional-integral guidance with reduced sensitivity to target maneuvers

This paper proposes a new optimal guidance law based on proportional-integral (PI) concept to reduce the sensitivity to unknown target maneuvers. Compared to existing PI guidance laws, the proposed guidance command is derived in the optimal control framework while guaranteeing finite time convergence. The kinematics equation with respect to the zero-effortmiss (ZEM) is utilized and the integral ZEM is augmented as a new system state. The proposed guidance law is derived through the Schwarz's inequality method. The closed-form solution of proposed guidance law is presented to provide better insight of its properties. Additionally, the working principle of the integral command is investigated to show why the proposed guidance law is robust against unknown target accelerations. The analytical results reveal that the proposed optimal guidance law is exactly the same as an instantaneous direct model reference adaptive guidance law with a pre-specified reference model. The potential significance of the obtained results is that it can provide a point of connection between PI guidance laws and adaptive guidance laws. Therefore, it allows us to have better understanding of the physical meaning of both guidance laws and provides the possibility in designing a new guidance law that takes advantages of both approaches. Finally, the performance of the guidance law developed is demonstrated by nonlinear numerical simulations with extensive comparisons

Integrated Guidance and Control of Missiles with Θ-D Method

A new suboptimal control method is proposed in this study to effectively design an integrated guidance and control system for missiles. Optimal formulations allow designers to bring together concerns about guidance law performance and autopilot responses under one unified framework. They lead to a natural integration of these different functions. by modifying the appropriate cost functions, different responses, control saturations (autopilot related), miss distance (guidance related), etc., which are of primary concern to a missile system designer, can be easily studied. A new suboptimal control method, called the θ-D method, is employed to obtain an approximate closed-form solution to this nonlinear guidance problem based on approximations to the Hamilton-Jacobi-Bellman equation. Missile guidance law and autopilot design are formulated into a single unified state space framework. The cost function is chosen to reflect both guidance and control concerns. The ultimate control input is the missile fin deflections. A nonlinear six-degree-of-freedom (6-DOF) missile simulation is used to demonstrate the potential of this new integrated guidance and control approach