2 research outputs found
A novel dual-spin actuation mechanism for small calibre, spin stabilised, guided projectiles
© Cranfield University 2022. All rights reserved. No part of this publication may be reproduced without the
written permission of the author and copyright holderSmall calibre projectiles are spin-stabilised to increase ballistic stability, often at
high frequencies. Due to hardware limitations, conventional actuators and meth ods are unable to provide satisfactory control at such high frequencies. With the reduced
volume for control hardware and increased financial cost, incorporating traditional guid ance methods into small-calibre projectiles is inherently difficult. This work presents a novel method of projectile control which addresses these issues and conducts a systems
level analysis of the underlying actuation mechanism. The design is shown to be a viable
alternative to traditional control methods, Firstly, a 7 Degree-of-Freedom (DoF) dynamic model is created for dual-spin pro jectiles, including aerodynamic coefficients. The stability of dual-spin projectiles, gov erned by the gyroscopic and dynamic stability factors is given, discussed and unified across
available literature. The model is implemented in a Matlab/Simulink simulation environ ment, which is in turn validated against a range of academic literature and experimental
test data. The novel design and fundamental operating principle are presented. The actuation
mechanism (AM) is then mathematically formulated from both a velocity change (∆V )
and a lateral acceleration (a˜) perspective. A set of axioms are declared and verified using
the 7-DoF model, showing that the inherently discrete system behaviour can be controlled
continuously via these control variables, ∆V or a˜. Control state switching is simplified to
be instantaneous, then expanded to be generically characterised by an arbitrarily complex
mathematical function. A detailed investigation, parametric analysis and sensitivity study
is undertaken to understand the system behaviour.
A Monte Carlo procedure is described, which is used to compare the correction cap abilities of different guidance laws (GLs). A bespoke Zero-Effort-Miss (ZEM) based GLis synthesised from the mathematical formulation of the AM, with innately more know ledge of the system behaviour, which allows superior error correction. This bespoke GL
is discussed in detail, a parametric study is undertaken, and both the GL parameters and
PID controller gains are optimised using a genetic algorithm. Artificial Intelligence (AI)
Reinforcement learning methods are used to emulate a GL, as well as controlling the AM
and operating as a GL, simultaneously.
The novel GLs are compared against a traditional proportional navigation GL in a
nominal system and all GLs were able to control the AMs, reducing the miss distance to a
satisfactory margin. The ZEM-based GL provided superior correction to the AI GL, which
in turn provided superior correction over proportional navigation. Example CAD models
are shown, and the stability analysis is conducted on the geometry. The CAD model is
then used in CFD simulations to determine aerodynamic coefficients for use in the 7-DoF
dynamic model. The novel control method was able to reduce the 95% dispersion diameter
of a traditional ballistic 7.62mm projectile from 70mm to 33mm. Statistical data analysis
showed there was no significant correlation or bias present in either the nominal or 7-DoF
dispersion patterns. This project is co-sponsored by BAE Systems and ESPRC (ref. 1700064). The con tents of this thesis are covered by patent applications GB2011850.1, GB 2106035.5 and
EP 20275128.5. Two papers are currently published (DOI: 10.1016/j.dt.2019.06.003, the
second DOI is pending) and one is undergoing peer review..PH
Technology for large space systems: A bibliography with indexes (supplement 20)
This bibliography lists 694 reports, articles, and other documents introduced into the NASA Scientific and Technical Information System between July, 1988 and December, 1988. Its purpose is to provide helpful information to the researcher or manager engaged in the development of technologies related to large space systems. Subject areas include mission and program definition, design techniques, structural and thermal analysis, structural dynamics and control systems, electronics, advanced materials, assembly concepts, and propulsion