Dynamic inversion is one of the most widely applied designs for multivariable controls in the aircraft industry. it is a type of model-following controller. This nonlinear control law structure was used to develop the flight control system for the F-35 because the same flight control system would be flying on each of the different variants. It isolates the qualities of the different variants and uses the control systems to return them to standard response characteristics. Undesired dynamics are canceled and replaced with a specific feedback function. The advantage of this control law is that it decouples the aircraft dynamics from the flying qualities. This allows different regulator commands to be implemented for the different airframes. This controller optimally allocated the acceleration commands to the control surfaces for each variant of the fighter. Dynamic Inversion requires an on-board model of the aircraft dynamics. This is used to estimate the acceleration commands for dynamic inversion and uses a control effectiveness matrix. Then the desired linear first-order aircraft responses are used to create the control deflections. DI is the embodiment of the aspects of noninteracting control laws and the transformation of nonlinear systems into equivalent linear systems. Dynamic inversion is good at adapting to configuration changes in the plant dynamics. It does not provide any theoretical guarantee of robustness.
The feedforward elements of the DI control law, and the feedback elements would ideally combine to produce a transfer function of 1.[8]
Equations for Dynamic Inversion Control
[[REAL Program]] – used dynamic inversion for the inner loop
[[X-36 Reconfigurable Flight Control Laws]] – used dynamic inversion in line with a neural network.
[[Honeywell Multi-Application Control (MACH)]] – First known use of DI for a flight control system
Disadvantages of Dynamic Inversion Controllers
[[F-18 HARV]]- used Dynamic Inversion Controls
[[X-38 Flight Control System Design]] used dynamic inversion controls.
[[Dynamic Inversion Pitch Control Example]]
[[Dynamic Inversion Lateral Directional Example]]
[[Nonlinear Static Inverse]]
[[Intelligent Flight Control System Steps]] – used dynamic inversion control law
[[VFW 614]] – used dynamic inversion for the in-flight simulators
[[BO-105]] – also used dynamic inversion for the in-flight simulators
[[Incremental Nonlinear Dynamic Inversion]] – variant of DI
[[Dynamic Inversion Control for a Spring Mass damper System]] – DI controller for a basic 2nd-order system
[[JDAM Dynamic Inversion CLAW]] – used to eliminate gain scheduling requirements
Advantages of Dynamic Inversion Controllers
[[Nonlinear Dynamic Inversion]] – APL used for missile fcs.
[[Oblique Wing Aircraft]] – can use a DI controller
[[DLR REAL Flight control System]] – inner loops designed with dynamic inversion
F-16 VISTA (X-62)– helped to develop the flight control laws
MFA Control Law – includes diagram for VISTA
[[X-31A Flight Control Laws]] – An early form of dynamic inversion
[[EC-135 Helicopter]] – used to design a model for dynamic-inversion control laws
RASCAL Advanced Control Laws – followed a dynamic inversion control law structure
[[BO-105 Roll Control System Frequency Response]] – used dynamic inversion
[[Dale Enns]]
[[Application of Multivariable Control Theory to Aircraft Control Laws]] – developed DI controllers
[[F-117 Prototype DI Controller]] – simulated prototype controller
[[MCLAWS-2]] – uses a dynamic inversion control law structure
[[Multivariable Plant Inverse Equations]] – contains more information on inverse plant dynamics
Sources
- [1] D. W. Nixon and L.-M. Aeronautics, “Flight Control Law Development for the F-35 Joint Strike Fighter”.
- [2] “Flight Control Law Design: An Industry Perspective – ppt video online download.” Accessed: Feb. 11, 2023. [Online]. Available: https://slideplayer.com/slide/5738737/
- [3] C. Lubas and P. Paglione, “NONLINEAR DYNAMIC INVERSION APPLIED TO A F-16 AIRCRAFT,” 2009.
- [4] RVFCSdesignDynamicInversion
- [5] P. Dr. Hamel, “Advances in Aerodynamic Modeling for Flight Simulation and Control Design,” Jan. 2001.
- [6] P. B. Jackson, “Overview of Missile Flight Control Systems,” JOHNS HOPKINS APL TECHNICAL DIGEST, vol. 29, no. 1, 2010.
- [7] M. C. Cotting et al., “X-62 VISTA Simulation and Autonomy Flight Testing,” in AIAA SCITECH 2023 Forum, in AIAA SciTech Forum. , American Institute of Aeronautics and Astronautics, 2023. doi: 10.2514/6.2023-1928.
- [8] C. Frost, W. Hindson, E. Moralez, G. Tucker, and J. Dryfoos, “Design and Testing of Flight Control Laws on the RASCAL Research Helicopter,” in AIAA Modeling and Simulation Technologies Conference and Exhibit, Monterey, California: American Institute of Aeronautics and Astronautics, Aug. 2002. doi: 10.2514/6.2002-4869.
Backlinks
[[Acceleration Autopilot]]
[[F-35 Flight Control Laws]]
[[Matrix Inverse]]
[[Model-Following Control System]]
[[System Robustness]]