Sensors, measurement fusion and missile trajectory optimisation

When considering advances in “smart” weapons it is clear that air-launched systems have adopted an integrated approach to meet rigorous requirements, whereas air-defence systems have not. The demands on sensors, state observation, missile guidance, and simulation for air-defence is the subject of this research. Historical reviews for each topic, justification of favoured techniques and algorithms are provided, using a nomenclature developed to unify these disciplines. Sensors selected for their enduring impact on future systems are described and simulation models provided. Complex internal systems are reduced to simpler models capable of replicating dominant features, particularly those that adversely effect state observers. Of the state observer architectures considered, a distributed system comprising ground based target and own-missile tracking, data up-link, and on-board missile measurement and track fusion is the natural choice for air-defence. An IMM is used to process radar measurements, combining the estimates from filters with different target dynamics. The remote missile state observer combines up-linked target tracks and missile plots with IMU and seeker data to provide optimal guidance information. The performance of traditional PN and CLOS missile guidance is the basis against which on-line trajectory optimisation is judged. Enhanced guidance laws are presented that demand more from the state observers, stressing the importance of time-to-go and transport delays in strap-down systems employing staring array technology. Algorithms for solving the guidance twopoint boundary value problems created from the missile state observer output using gradient projection in function space are presented. A simulation integrating these aspects was developed whose infrastructure, capable of supporting any dynamical model, is described in the air-defence context. MBDA have extended this work creating the Aircraft and Missile Integration Simulation (AMIS) for integrating different launchers and missiles. The maturity of the AMIS makes it a tool for developing pre-launch algorithms for modern air-launched missiles from modern military aircraft.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Missile Modeling and Simulation of Nominal and Abnormal Scenarios Resulting from External Damage

This thesis presents the development of a six-degree-of-freedom flight simulation environment for missiles and the application thereof to investigate the flight performance of missiles when exposed to external damage. The simulation environment was designed to provide a realistic representation of missile flight dynamics including aerodynamic effects, flight control systems, and self-guidance. The simulation environment was designed to be modular, expandable, and include realistic models of external damage to the missile body obtained by adversarial counteraction. The primary objective of this research was to examine missile flight performance when subjected to unspecified external damage, including changes in trajectory, stability, and controllability, and to provide a basis for the future development of fault tolerant control laws to improve target tracking and overall flight performance when experiencing abnormal conditions. To accomplish this, a variety of scenarios were developed to simulate damage to different parts of the missile, such as the fuselage, wings, and control surfaces. Three types of damage are considered: arbitrary failures which affect the major overall missile dynamic force and moment coefficients, structural failures including wings and fin breakage, and stuck fin failures where a given fin is arbitrarily fixed to a specified deflection. The missile behavior in response to these scenarios was analyzed and compared to the baseline behavior of an undamaged missile. The results of this research demonstrate how simulated missiles behave during flight, under both nominal and abnormal scenarios resulting from external damage. The simulation environment is shown to be a useful tool in examining the performance of missiles under real-world scenarios, such as during combat, in the event of an accident, or when exposed to other adversarial counteractions. This is done by producing envelopes for mission success for each tested scenario and analyzing the results. The results of this research can be used to assist in and improve the design and performance of missiles and enhance their survivability in the field. These results can also be used to determine the amount of damage necessary to prevent a given missile from reaching its target

Investigation of new and novel techniques of accurately measuring the response of structures to short-duration loads

Although terrorist and accidental industrial explosions are infrequent, engineers still need to understand how structures respond to the short-duration loads generated by such events. Previous research to measure the response of structures, subject to such loads, has often been limited to before and after measurements. Although there are sensors that can measure the transient response, such as linear voltage displacement transducers, accelerometers and laser displacement gauges, these are often expensive and limited to measuring individual points. This research identifies cheaper methods to accurately measure the transient response caused by short-duration loads. A review of sensors used to measure structural response in short-duration and structural health monitoring (SHM) scenarios, identified inertial measurement units (IMUs) as a potential alternative to traditional sensors. Although the individual IMU gyroscopes and accelerometers may be used in isolation, when combined using data fusion techniques improved accuracy is possible. IMUs have been used for vehicle navigation, and to a limited degree SHM, but minimal evidence of their use to measure the response of structures subject to short-duration loads exists. To validate their use in such environments, an MPU9250 IMU was used to monitor the response of several simple structures to various loads, from static, through dynamic to ballistic loading. In a parallel investigation, two full-bridge strain gauge arrangements were used to measure support rotation. The research proved that using data fusion to combine IMU accelerometer and gyroscope results, produced an accurate representation of the response, quantified using existing error and inequality measure criteria. It also showed that, in certain scenarios, a combination of strain gauges could be used to measure an element’s support rotation with a reasonable degree of accuracy. It was concluded that cheap sensor systems, such as IMUs and strain gauges, had the potential to accurately measure the response of structures to short-duration loads.Open Acces

Air-data estimation for air-breathing hypersonic vehicles

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1996.Includes bibliographical references (p. 194-198).by Bryan Heejin Kang.Ph.D

Voyager spacecraft system. Preliminary design, volume B /book 3 of 3/ - Alternate designs considered - G and C, Pwr, C and S, prop, plans

Alternate designs for guidance and control, power, controller and sequencer systems for Voyager spacecraft - effect of alternate designs on schedule and implementatio

Development of Innovative GNC Algorithms for Aerospace Applications

The main context of the present dissertation is the SAPERE STRONG (Space Advanced Project for Excellence in Research and Enterprise – Sistemi, Tecnologie e Ricerche per l’Operatività Nazionale Globale) project, founded by Italian Ministry of University and Research (MIUR) with the goal to improve Italian access to Space and Space Exploration. For this purpose, extension of the launch capability of the Vega launcher is included in the project, realized with a Space-Tug which is used to deploy in the nominal orbit a payload spacecraft. This thesis has the objective to develop an advanced orbital simulator as a tool which makes the designer able to develop and test the Guidance, Navigation and Control (GNC) software for the Space-Tug spacecraft. The GNC software is developed in collaboration with the leader industrial company of the project, Thales Alenia Space. Thales Alenia Space (TAS) is in charge of developing the Navigation and Control Function and the main structure of flight software, while Politecnico di Torino collaborates with the development of the Guidance function and the orbital simulator. During the whole project has been planned an internship of 1500 hours inside the offices of TAS in Torino. The project includes also a visiting period of international institution. In the specific frame of this Ph. D. thesis, has been spent three months at the University of Sevilla, with the purpose of study and design of a Galileo receiver as an additional input for determination of position in advanced navigation systems, since the Galileo constellation is near to be fully operative in the next future. Details related to all the activities executed during this internship will be presented in Appendix B. The main objective of this dissertation is the development of innovative GNC algorithms, focusing mainly on the Guidance problem, for aerospace application. An extensive literature review of existing guidance law, control techniques, actuators for attitude and trajectory control, sensors and docking mechanism and techniques has been performed. The Guidance topic has been analyzed focusing on the missile-derived Proportional Navigation Guidance (PNG) algorithm, Zero-Effort-Miss/Zero-Effort-Velocity (ZEM/ZEV) algorithm and Lambert guidance. Feasibility, performance, pros and cons have been extensively studied in this work, especially in an experimental fashion, and new solutions and implementation strategies have been proposed. The literature review has been completed for Control and Navigation issues, as well. Control strategies, actuation systems and algorithm have been investigated, starting from the classical proportional/Integrative/Derivative (PID) controllers, to more recent and innovative control law, such as Linear Quadratic Regulator (LQR). As for the Control function, the Navigation topic, intended as navigation filters and algorithms, has been studied in the last period of this work, while the navigation problem form the hardware side (i.e. sensors) has been deeply analyzed in the present work. In addition to the GNC investigation, the simulation topic has been studied as well, since one of the goals of this dissertation is the realization of an orbital simulator. The orbital simulator is a complete 6 degrees-of-freedom simulator, based on the relative equation of motion (Hill’s equations) for the trajectory computation and based on the classical rigid body equation, including the quaternion notation, for the computation of the attitude dynamics. The orbital environment is well defined, including all common disturbances found in Low Earth Orbits (LEO) and affecting the dynamics of an orbiting body. A complete set of sensors is implemented, including an accurate model of common measurement errors affecting the sensors included in the spacecraft configuration (Inertial Measurement Unit, Star Tracker, GPS, Radio Finder, Lidar and Camera). Actuators are carefully modeled, including a reaction wheels system and a reaction control thrusters system. Errors derived for misalignment of the wheels system and non-nominal inertia and shooting and misalignment errors for the thrusters systems are modeled as well

Space programs summary no. 37-51, volume 3 for the period April 1 to May 31, 1968. Supporting research and advanced development

Space Programs Summary - supporting research and advanced developmen

Flight Mechanics/Estimation Theory Symposium, 1992

This conference publication includes 40 papers and abstracts presented at the Flight Mechanics/Estimation Theory Symposium on May 5-7, 1992. Sponsored by the Flight Dynamics Division of Goddard Space Flight Center, this symposium featured technical papers on a wide range of issues related to orbit-attitude prediction, determination, and control; attitude sensor calibration; attitude determination error analysis; attitude dynamics; and orbit decay and maneuver strategy. Government, industry, and the academic community participated in the preparation and presentation of these papers

State of the art survey of technologies applicable to NASA's aeronautics, avionics and controls program

The state of the art survey (SOAS) covers six technology areas including flightpath management, aircraft control system, crew station technology, interface & integration technology, military technology, and fundamental technology. The SOAS included contributions from over 70 individuals in industry, government, and the universities

Gimbal Angle Bias Free State Estimator for Anti- Ballistic Missile using Additional Accelerometers

To neutralize the incoming ballistic missile targets, its information should be accurately known in the interceptor missile body frame. Under the perfect scenario of seeker and navigation sensor mounting on the missile airframe, the estimates of the target states are accurate in the missile body frame. But in reality there exists a misalignment between missile body frame and seeker mechanical axis, this leads to biased gimbal angle measurements from the seeker. Even though the bias in the gimbal angles are small, it causes a biased estimate of relative position and relative velocities. Using these biased state estimates erroneous guidance commands are generated which in turn deteriorates the mission performance. Present paper addresses this issue and proposes a methodology to estimate the bias in the gimbal angles by mounting two accelerometers on back plate of seeker antenna, which makes target state estimator insensitive to axis misalignment errors. Simulation on the Six-DOF platform with a realistic seeker model under extreme bias scenarios shows a tremendous improvement and makes the target state estimates unbiased leading to acceptable mission performance