Brian A. White

Multi-objective Evolutionary Design of Fuzzy Autopilot Controller

A multi-objective evolutionary algorithm is used to determine the membership function distribution within the outer loop control system of a non-linear missile autopilot using lateral acceleration control. This produces a design that meets objectives related to closed loop performance such as: steady state error, overshoot, settling and rising time. The evolutionary algorithm uses non-dominated sorting for forming a Pareto front of possible solutions. This paper shows that fuzzy controllers can be produced for engineering problems, with the multi-objective algorithm allowing the designer the freedom to choose solutions and investigate the properties of very complex systems.

Modern Missile Flight Control Design: An Overview

Abstract The requirement of high agility in the entire flight envelope will dominate the flight control design for future missile systems. The desin requirements for the next-generation autopilots will include not fast response to the required acceleration demands and extreme maneuvarability while maintaining stability, but also robustness over a wide range of mission profiles at all altitudes. An overview of different control techniques for missile autopilot design is presented in this paper.

Modern Missile Guidance Design: An Overview

Abstract The demands on modern guided weapon systems are becoming more stringent than in the past. There is a requirement to have pin-point accuracy, low cost per round, an easy upgrade path, better performance in a counter measures environment and to be able to acquire and track low observable targets. Many of the recent conflicts around the world have exacerbated this trend and the demands on weapon guidance systems and sensor development have risen considerably. Two of the major components of a guided weapon system are the guidance algorithm and the missile autopilot. The guidance algorithm issues command to the autopilot to enable the missile to be guided onto the target. This requires great precision and very fast response from the missile airframe. In this paper we present the current trends on missile guidance systems design.

An investigation into Kalman filter target tracking algorithms and their real time parallel transputer implementation

For target tracking applications, a Kalman filter is generally used to estimate the kinematic components of a manoeuvring target (position, velocity and acceleration) from noisy measurements. The tracking algorithm is selected according to a trade-off between its performance and real-time computational requirements when choosing the level of complexity of the model. According to the application, either a linear or a nonlinear Kalman filter algorithm can be used to track manoeuvring targets. However, although excellent accuracy estimates can be achieved with any chosen algorithm, it requires a huge amount of calculation thus making real-time processing impossible. This paper investigates the parallel implementation of tracking Kalman filters (EKF, GRF, LDKF and MGEKF) in both 2- and 3-D frames onto a range of transputer topologies to enable practical realisations. The partitioning strategies are highlighted, real-time implementation results are presented, and the relative speedup and efficiency are calculated to evaluate the performance of each parallel implementation.

Towards Veriflable Approach to Mission Planning for Multiple UAVs

Multiple UAV missions ofier beneflts in terms of success rate and area coverage. This research is aimed at developing veriflable mission planning for multiple UAVs cooperatively searching an area. The complexity and safety critical nature of the mission motivated the use of a formal method like model checking to verify the correctness of the system. In this paper, we present model checking approach to verify the bahaviour of a UAV searching an area. The UAV behaviour is captured by means of a flnite state transition model known as Kripke model and the temporal speciflcations are expressed in computational tree logic (CTL). Symbolic Model Verifler (SMV), a popular model checker, has been used to verify whether the model satisfles the speciflcations.

LPV Polynomial Eigenstructure Assignment for Formation Flying Control Around Sun-Earth L 2 Point

A new control law based on polynomial eigenstructure assignment (PEA) is presented for the high accurate formation flying in the vicinity of Sun-Earth L2 point. The dynamics of relative motion is formulated as a nonlinear equation and then linearized into LTI model and LPV model that are used for the latter application. The PEA approach implemented in missile autopilot is developed for the accurate formation flying in the interferometer mission. With this PEA approach, the eigenstructure assignment for the controller can be completed without imposing any particular eigenvalues. Using a polynomial matrix eigenspace of the system and a coprime factorization of the desired closed-loop transfer function, the designer is only left to choose the controller structure and calculate the controller gains by several simple formulas to produce a flexible design approach. In this paper, the LTI model used PEA approach is extended to the application in LPV model to realize the independence between the closed-loop system and the operating point. The approach is similar to dynamic inversion with a self-scheduled controller, but without the considering of zero dynamics. A position keeping control law is designed for the MIMO formation flying system by using a decoupling method during the design process of PEA approach to ensure the closed-loop system to achieve the desired control performance objective. Finally, a simulation is carried out to validate the performance of the new controller for the formation flying system.

Trajectory Control of a Non-Linear Homing Missile

Abstract Input-output approximate linearisation of a non-linear fourth order system has been studied. A method for controlling the non-linear system that is i/o linearisable is examined that retains the order of the system in the linearisation process, hence producing a linearised system with no internal or zero dynamics. Desired tracking performance for lateral acceleration of the missile is achieved by using a non-linear control law that has been derived by selecting the lateral velocity as the linearisation output. Simulation results are shown that exercise the final design and show that the linearisation and controller design are satisfactory.

Implementation of an adaptive EKF to multiple low cost navigation sensors in wheeled mobile robots

The present aim of this research is to design a navigation sensor suite for a newly built mobile robot using low cost multiple sensors. A basic requirement for an autonomous mobile robot is its ability to localize itself accurately. This paper describes an accurate method for generating navigational data for a wheeled mobile robot. An adaptive extended Kalman filter (AEKF) is used to fuse data from multiple low cost sensors. In order to estimate the spatial position of a wheeled robot, a combination of accelerometers, a rate gyroscope and two wheel encoders are used. The system discussed in this paper has more measurement sensors than system states and therefore the sensors give overlapping, low-grade information affected by noise, bias, drift, etc. The dynamics of the robot and sensor system are non-linear. Therefore an AEKF is used to estimate these overlapping low-grade measured sensor data and give the best possible estimate of the mobile robot position. The adaptive mechanism in this case uses the Riccati Equation adaption. The basic idea is to change the Kalman Gain. This is done by changing the Process noise co-variance matrix adaptively. Simulations show an improved performance in the estimates from the AEKF when compared to the EKF.

Mobile Robot Control Design via Nonlinear Dynamic Inversion

Abstract The controller for a mobile robot, consisting of a feedback loop, renders the closedloop systems steady-state input-output to be linear time invariant and causes the output to track a commanded trajectory. With real-time, accurate parameter data the feedback loop effectively cancels the parameter dependent tenns. The plant-feedback loop is appeared as a LT! system. Simulation results are shown that exercise the final design and show that the linearisation and controller design are satisfactory.

Robust Lateral Augmented Acceleration Flight Control Design

Abstract A lateral augmented acceleration autopilot is designed for a model of a tactical missile. The tail-controlled missile in the cruciform fin configuration is modelled as a second-order quasi-linear parameter-varying system. The autopilot design is based on input-output pseudolinearisation, which is a restriction of input-output feedback linearisation to the set of equilibria of the nonlinear model. Robust autopilot design taking account parametric stability margins for uncertainty aerodynamic derivatives is implemented using convex optimisation and linear matrix inequalities - LMI. Simulations for constant lateral acceleration demands including uncertainties show satisfactory robust performance.