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• Experimental Aircraft Programme (EAP, 1983-1995)
– Follow on from Jaguar programme.
– Control design process:
• Linear low frequency: PI scheduled as function control
• Nonlinear: trim distribution, nonlinear control power, nonlinear
variations of stability
• Linear high frequency: avoid structural coupling
– Lessons learned: separate regulator and command path designs.
• FBW Jaguar and EAP shaped Eurofighter flight controller
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United Kingdom
Vectored thrust Aircraft Advanced Control (VAAC) program
• Inception in 1984.
• Handling, control and display requirements for future short takeoff/vertical
landing (STOVL) aircraft.
• Experimental FBW VAAC Harrier.
• Development and testing of advanced aircraft flight control algorithms.
– Longitudinal axis, integrated management of thrust vectoring and
aerodynamic forces for decoupled control.
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UK - VAAC Control Strategies
• Classical control, loop-at-a-time
– Frequency shaping, gain-scheduling, significant nonlinearities
linearized with inverse functions, iterative design.
– Anti-windup scheme and control allocation.
• Nonlinear static inverse
– Nonlinear inverse of the aircraft to determine control effectors to trim.
aircraft at a given maneuvering state.
– Constrainted design process used to define unique solution to nonlinear
inverse problem (trim map).
– Nonlinear inverse feed-forward combined with low gain, classical
feedback design for stability.
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UK - VAAC Control Strategies
• Nonlinear Dynamic Inversion (NDI)
– Nonlinear dynamic model of aircraft used to invert nonlinearities and a
classical PI controller designed to track desired pitch rate command.
– Pilot commands filtered prior to input to NDI controller.
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UK - VAAC Control Strategies
• H loop shaping
– Multivariable linear controllers at 4 points: hover-to-forward flight.
– Inner-loop pitch rate feedback used to reduce effect of pitch moment
due to thrust changes.
– Outer-loop 3-input/3-output, H loop shaping to control normal and
forward acceleration and incidence.
– Weight selection similar to classical loop-shaping.
– Four linear point designs gain-scheduled throughout flight envelope.
• Controller implemented in observer form.
• Interpolated controller gains and interpolated controller outputs.
– H loop shaping techniques also used to synthesize an integrated
longitudinal/lateral flight and propulsions control system for VAAC.
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UK - VAAC Control Strategies
• Linear, parameter-varying (LPV) controller
–System dynamics written as LTI models whose state-space coefficients
are a function of scheduling variable(s).
–LPV H loop shaping uses LPV model of nonlinear aircraft dynamics to
directly synthesize a scheduled LPV controller.
–Successfully implemented at tested between 1995 and 1998.
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Israel
• Light, multi-mission fighter “Lavi”
– Initial flight test: 31 Dec 86, program terminated: 30 Aug 87
– Flight control laws
• Classical technique with optimal control methods used in
preliminary design process.
– Lessons learned: Relationship between control design parameters and
flying qualities.
• UAVs
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Russia
SU-27
SU-30MK
SU-35 SuperFlanker
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Russia
MIG-29
SU-37 Terminator
TU-22
SU-27
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Russia
SU-30MK
TU-160
SU-37
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Russia
Extensive history of military/commercial aircraft development.
• English language literature on Russian industry flight control design
techniques is limited.
Sukhoi 37 FBW flight controller
• Quad redundant DFCS
• Design requirements
– Good handling qualities.
– Optimal trimming.
– Reconfigurable under flight control system failures to maximize control
moments and trim configuration.
• Adaptive controller designed to eliminate small amplitude self-induced
oscillations due to actuator nonlinearities.
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Russia - SU-37 Aircraft
• Canards and thrust vectoring (TV loop not shown.).
• Longitudinal controller synthesized with classical control methods.
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United States of America (USA)
Commerical
• Boeing (McDonnell Douglas)
– B-717, B-737, B-747, B-757, B-767, B-777
　
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