Thrust Vector Controland Visualisation for Stovl Aircraft

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Thrust Vector Controland Visualisation for Stovl Aircraft

P. M. Lodge / C. Fielding

There are many areas where the design of control laws for short take- off and vertical landing (STOVL) aircraft are radically different from those of a conventional design. One the most challenging areas is related to control of the thrust vector and in particular how to design control laws that can deal with conflicting demands control saturation and integrator wind-up. Unlike a conventional aircraft. where full primary control surface deflections are rarely used the STOVL aircraft nozzle vector angle and engine thrust are often operated on their limits for significant periods of time. For example, to achieve maximum deceleration from wing-borne flight the nozzles are vectored to their forward authority limit and remain there for several seconds. The first part of this paper provides background on the UK's Integrated Flight and Propulsion System (IFPCS) programme. the BAF SYSTEMS P112C-6 aircraft configuration and the Rolls- Royce R1357l engine concept. A command strategy to control the aircraft during wing-borne flight and through the transition to the hover is introduced which leads to the description of a suitable control law architecture to satisfy this command strategy. With the approach chosen, 'thrust vector equations' are required to transform the pilot's commands into nozzle vector angle and engine thrust demands. The equations are derived for the Harrier and subsequently for the more complex P112C-6 configuration. These equations are then extended to cover the cases of saturated control conditions. Emphasis is placed on the visualisation and verification of the complex function that result.