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disturbance rejection and loop bandwidth
• Key: Selection of variables to regulate and controls to perform
regulation
• “Integral” regulators augmented, zero steady-state errors to
constant inputs
Boeing
Integral LQR/LQG design procedure:
• Select controls and regulated outputs: # controls = # regulated variables.
– Check singular values and transmission zeros.
• Attach integrators and set target zeros.
• Select Q and R matrices for LQR problem.
–Q and R selected based on command loop crossover frequencies.
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•Q ( R ) diagonal, qi (ri) adjusts bandwidth of command loop for yi (ui).
– Check loop at input to integrator and actuator.
– Note that the control loop crossover frequency is limited by the actuator
capabilities and structural mode coupling.
– Verify that the phase margins at higher frequencies are sufficient.
• Feed-forward gains adjusted for flying qualities.
Boeing
Applied to B-767, JSF (Boeing), UCAV, JDAM MMT and ACTIVE F-15.
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Boeing – X-36
X-36 Prototype fighter aircraft
•Stealth and agility prior to UCAV
•28% scale, remotely piloted
•Reconfigurable flight control laws
Reconfigurable flight control laws
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B-747
• Dynamic inversion (DI)
• Explicit model following framework
• On-line neural network (NN) to adaptively regulate inversion error:
• Uncertainties
• Failures
• Damage
• Desired dynamics and control mixer same for DI and adaptive NN
Boeing – X-36
Reconfigurable flight control laws
• NN able to stabilize vehicle following failures and damage.
• On-line NN adaptively canceled inversion error.
• NN/DI controller provide improved HQ when failures occurred.
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B-747
Honeywell
Honeywell Research Center (Honeywell Labs)
•Significant contribution to areas of robust control and dynamic inversion.
•Approach to NDI is MACH (Multi-Application Control).
•MACH is a modular, nonlinear multivariable design approach.
– Blends classical control design with inversion.
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•Outer-loop controllers: Proportional or PI.
•Inner-loop controllers: Dynamic Inversion .
Honeywell MACH
•Outer loops: multivariable signal shaping provides position command
and rate tracking.
•Inner loops: NDI to normalize vehicle dynamics to be integrators.
•NDI requires on-board model (OBAC).
•Estimate derivatives of aircraft states and control variables (CV).
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B-747
Honeywell MACH
Five components of MACH:
1. Select controlled variables (CV) for performance/robustness.
2. Outer-loops convert pilot/guidance commands into CV commands.
•Nonlinear elements such as limiters.
3. Desired dynamics define dynamic behavior the CVs should follow
while tracking their commands.
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B-747
4. NDI attempts to solve the equations of motion for actuator commands
to satisfy CV desired rate of change.
•Control allocation logic may be necessary.
5. OBAC computes nonlinear vehicle dynamics for inversion.
•Least-squares used to approximate aerodynamic data.
Honeywell MACH
•Initial controller for Lockheed Martin JSF vehicle (1995-97).
•Successfully flight tested on X-38 V132.
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B-747
Lockheed Martin
• JSF F-35
F/A-22 Raptor
Leading producer of military aircraft
F/A-22 Raptor
• Air superiority.
• Stealth and agility.
• Sustained supersonic cruise.
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• YF-22 (initial demonstrator) flight control designed using eigenstructure
assignment.
• Series of pitch oscillations 13m above ground lead to aircraft impacted on
runway (1992).
• PIO due to control surface rate/position saturation, time delays.
Lockheed Martin - F/A-22
•F/AJS-F2 F2- 3f5light control law redesign
• Excellent flying qualities and lessons learned.
• Classical control combined with eigenstructure assignment.
• Removal of pitch integrator key to redesign.
• Addition of first order pitch stick command pre-filter needed to recover
flying qualities requirements.
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• Classical tradeoff between pitch attitude and flight path angle bandwidth.
• Redesigned flight control law successfully achieved Level I handling
qualities for all closed-loop tracking tasks.
Lockheed Martin - JSF
• JSF F-35 F-35 Joint Strike Fighter (JSF).
•Conventional takeoff/landing (CTOL/AF).
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