No description available.

No description available.

This thesis is concerned with the synthesis of linear-optimal heave control of electromagnetic suspension systems. The methods of computer-aided analysis and simulation were employed in this research. The intrinsic properties of electromagnetic suspension system were investigated to facilitate the synthesis and to provide guidelines for the design of electromagnets or linear motors suitable for use in suspension systems. The technique of complementary filtering, which resolves the conflicting requirements of high stiffness to load and high compliance for ride-comfort, was further developed. This led to the ability of directly comparing the merits of systems with different configurations and determining the optimal natural frequency. Together with a novel way of removing steady state gap error during the traversing of transition curves, the filtering technique was applied to the system using fixed-gain and sliding-mode variable-structure control methods. The latter method is well known for its abi1ity in maintaining closed-loop characteristics in the presence of disturbance. However, further development was required before it was applied. The resultant suspension system gave a 20% improvement in ride-quality over the best published result which was carried out under similar test conditions. Even so, theoretical analysis showed that a four-fold improvement may be possible.

The robust loop-shaping control methodology is applied in the flight control system design of the Cranfield A3 Observer unmanned, unstable, catapult launched air vehicle. Detailed linear models for the full operational flight envelope of the air vehicle are developed. The nominal and worst-case models are determined using the v-gap metric. The effect of neglecting subsystems such as actuators and/or computation delays on modelling uncertainty is determined using the v-gap metric and shown to be significant. Detailed designs for the longitudinal, lateral, and the combined full dynamics TDF controllers were carried out. The Hanus command signal conditioning technique is also implemented to overcome actuator saturation and windup. The robust control system is then successfully evaluated in the high fidelity 6DOF non-linear simulation to assess its capability of launch stabilization in extreme cross-wind conditions, control effectiveness in climb, and navigation precision through the prescribed 3D flight path in level cruise. Robust performance and stability of the single-point non-scheduled control law is also demonstrated throughout the full operational flight envelope the air vehicle is capable of and for all flight phases and beyond, to severe launch conditions, such as 33knots crosswind and exaggerated CG shifts. The robust TDF control law is finally compared with the classical PMC law where the actual number of variables to be manipulated manually in the design process are shown to be much less, due to the scheduling process elimination, although the size of the final controller was much higher. The robust control law performance superiority is demonstrated in the non-linear simulation for the full flight envelope and in extreme flight conditions.

No description available.

The robust loop-shaping control methodology is applied in the flight control system design of the Cranfield A3 Observer unmanned, unstable, catapult launched air vehicle. Detailed linear models for the full operational flight envelope of the air vehicle are developed. The nominal and worst-case models are determined using the v-gap metric. The effect of neglecting subsystems such as actuators and/or computation delays on modelling uncertainty is determined using the v-gap metric and shown to be significant. Detailed designs for the longitudinal, lateral, and the combined full dynamics TDF controllers were carried out. The Hanus command signal conditioning technique is also implemented to overcome actuator saturation and windup. The robust control system is then successfully evaluated in the high fidelity 6DOF non-linear simulation to assess its capability of launch stabilization in extreme cross-wind conditions, control effectiveness in climb, and navigation precision through the prescribed 3D flight path in level cruise. Robust performance and stability of the single-point non-scheduled control law is also demonstrated throughout the full operational flight envelope the air vehicle is capable of and for all flight phases and beyond, to severe launch conditions, such as 33knots crosswind and exaggerated CG shifts. The robust TDF control law is finally compared with the classical PMC law where the actual number of variables to be manipulated manually in the design process are shown to be much less, due to the scheduling process elimination, although the size of the final controller was much higher. The robust control law performance superiority is demonstrated in the non-linear simulation for the full flight envelope and in extreme flight conditions.

This thesis presents the development of a computerized design synthesis for canard-delta combat aircraft. This is complementary to, and follows the philosophy of, an existing RAE system for conventional combat aircraft with swept wings (Ref. 1). The background to the work and the Research Programme objectives and limitations are initially examined. The design of a baseline canard-delta combat aircraft is then described together with all the assumptions and decisions which led to its final configuration. The philosophy behind the progressive evolution of the aircraft geometry and packaging modules from the baseline configuration is explained in detail. The development of detailed modules for the estimation of the aircraft aerodynamics and performance is then presented. A full description of the investigations into the effects of canard-delta interference on the aircraft aerodynamics is also included. The mathematical content of the aircraft geometry, packaging, aerodynamics and performance modules is presented separately in the appendices in greater detail. The development and architecture of the design synthesis and graphics programs are finally presented and the program operation is described with the aid of flow-charts. A comprehensive user's manual and a design example are also provided.

Advances in piston engine technology, coupled with high costs of turbine engines have led many general aviation manufacturers to explore the use of piston engines in their smaller vehicles. However, very few engine models are available to analyze piston engine performance. Consequently, designers using vehicle synthesis programs are unable to accurately predict vehicle performance when piston engines are used. This thesis documents the development of a comprehensive, thermodynamics based performance model that meets that need. The first part of this thesis details the basics of piston engine operation, including component geometry and the four stroke engine cycle. Next, the author analyzes the critical components of engine performance, including engine work and power. In developing the engine performance model the Ideal Engine Cycles are discussed. The cold air and fuel-air working fluid models are discussed, along with the types of combustion models, including the Otto Cycle, Diesel Cycle, and the Dual Cycle. Two performance models are generated using the Constant Volume Ideal Engine Cycle: an Ideal Gas Standard Cycle, and a Fuel-Air Cycle. The Ideal Gas Standard Cycle is useful for parametric analysis but lacks the accuracy required for performance calculations. The Fuel-Air Cycle, however, more accurately models the engine cycle and is selected as the basis for the computer program. In developing the computer program the thermodynamic charts used in the Fuel-Air Cycle calculations must be reproduced. To accomplish this, the NASA Chemical Equilibrium Application (CEA) program is integrated into a parent VBA based computer code to provide thermodynamic state point data. Finally, the computer program is correlated to the performance of an existing aviation engine to validate the model.

No description available.

No description available.