Unpiloted Time Simulation
Typical manoeuvres were simulated on the non-linear model to check operation of the control law. On the basis of these tests, the only change required to the H∞ feedback controller was a reduction in the bandwidths used for the nozzle and throttle because of the non-linear nature of the throttle-to-thrust characteristic, and backlash in the nozzle servo. However, the time simulations were very much part of the design loop when determining the gains and logic for the prioritized desaturation scheme. Setting these gains too high can be destabilising, whilst setting them too low doesn’t give the desired priorities. The time simulations on the non-linear model do not allow for lateral motion of the aircraft. This is primarily because any lateral motion needs the pilot to be in the loop to stabilise it. Longitudinal performance in the presence of lateral motion was evaluated and checked during piloted simulation.
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