Flight Control Design using Nonlinear Dynamic Inversion

Dr. Om Prakash PhD. IIT Bombay M.Tech. IIT Kanpur om4aero@gmail.com

Nonlinear Dynamic Inversion

• Nonlinear Aircraft dynamics are inverted based on measured states and inputs

• Cancels the original Aircraft dynamics of the system

• Replaces with desired Aircraft dynamics

• Used as feedback in control design

• Output should perfectly match the input

• Applicable to Highly maneuverable Aircrafts, Missiles, etc.

Nonlinear Aircraft Dynamics

Control Surface deflection

Aircraft States Aircraft Forces and Moments

Aircraft Forces and Moments dependent on

control surface deflection

Aircraft Forces and Moments independent of control surface deflection

Inverting above equation

Nonlinear Aircraft Dynamics Inversion

• Desired Aircraft Dynamics

Control Surface Deflection required to achieve demanded aircraft states

Desired Aircraft

Dynamics

Feedback Aircraft States

Commanded Aircraft States

SISO(Aircraft Pitch Axis) Dynamic Inversion Control

System Dynamics

System Dynamics Inversion

SISO(Aircraft Pitch Axis) NDI Control

• Longitudinal Dynamics

• Desired to control pitch rate q

Simplified 6DOF Aircraft Dynamics

Simplified representation

6-DOF Aircraft Dynamic Inversion

9-DOF PARAFOIL-PAYLOAD SYSTEM

9-DOF PARAFOIL-PAYLOAD EQUATIONS

• 9DOF EQUATIONS

Heading Tracking of Parafoil-Payload System

• Yaw rate inner loop equation

• Yaw Angle outer loop equation

Parafoil-Payload System Inner Loop Dynamic Inversion

• Yaw rate inner loop Inversion

• Inversion is

• Substituting this in above we get

Inner Loop inversion Block Diagram

Parafoil-Payload System Outer Loop Dynamic Inversion

• Yaw angle outer loop Inversion

• Inversion is

• Substituting this in above we get

Outer Loop Dynamic Inversion Block Diagram

Heading Tracking using Inner and Outer Loops

Longitudinal Missile Dynamics

Longitudinal Missile Dynamics Inversion

Longitudinal Missile Dynamics Inversion Result (Sungjin Cho et. al., 2002)

THANKS

End of Presetation