Computer aided system design and validation in the defence environment

A canard-controlled missile airframe configuration with a twist-and-steer (or polar) control system affords economies in design and kinematic performance but at present does not permit a direct analytical solution for the optimum guidance and roll control autopilot laws. The development of a stable roll loop of adequate bandwidth and response is fundamental in a twist-and-steer missile. Whilst the application of modern control theory has been successfully applied to the design of aileron-constrained time-invariant cases, its extension to the nonlinear case requires further development. Roll loop design is commonly carried out using frequency-domain methods coupled with detailed mathematical modelling and digital simulation. The use of commercially available control system design programs facilitates loop design and sensitivity studies across the operating envelope. Describing function techniques may be used to investigate limit cycle stability etc. The paper discusses the aerodynamics and the computer-aided design