Affordable Flight Control for Aircraft and Missiles

Not so long ago, research in flight control was largely an algorithmic endeavor�-�the objective was to devise higher performance control laws. Such research still continues, but an additional imperative is now prominent. For many new flight control developments, the challenge is not so much to come up with the control algorithm; the existing literature describes how to do that sufficiently well. The new challenges are cost-efficiency and development time reduction.

This chapter revises some of the basic technology for flight control systems and discusses how computational tools are now being used to ensure that new control systems can be affordably developed and deployed. The target vehicles for the flight control technology described are military aircraft and missiles. There are notable differences between the two, such as the use of different sets of actuators (in missiles, for example, reaction jets can directly control roll, pitch, and yaw).

Flight control system design requirements also differ fundamentally for aircraft and missiles,due to the presence of a pilot in the former. As a consequence, control techniques can differ. Dynamic inversion�-�a form of feedback linearization�-�is a popular technique for aircraft flight control, whereas linear quadratic optimal control is commonly used for missiles. In either case, complications arise due to the fact that accelerometers and gyros are not located at the center of gravity of the vehicle. In some cases, performance and stability can be improved by appropriately locating the sensors.

Simulation and analysis software is now essential for flight control design. The chapter discusses tools within the MATRIXx toolset that permit performance and robustness evaluation over a range of operating conditions. Today's tools allow aerospace engineers to graphically design a flight control system, analyze its performance and stability, and generate autocode that can be ported directly to training simulators, hardware in the loop simulators, and the aircraft itself. Similar tools are in use in other industries too-see Ch. 15 for an automotive industry perspective. Further discussion on computer aided control system design can also be found in Ch. 3 which also outlines a flight control application.

What lies ahead for flight control? This chapter concludes by noting the interest in, and the challenges associated with, uninhabited aircraft. This topic is also discussed in Ch 10 where focus is on multi-vehicle aerospace challenges.