Fixed-Wing UAV Formation Controller Design and Implementation

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Flight Simulation based on Gazebo & ROS:

Introduction & Hypothesis

Introduction

Use the “Leader-Follower” method to accomplish the 2 fixed-wing UAVs formation controlling.

Software Architecture

Hypothesis

• Earth
  • No rotation, inertial coordinate system
  • Flat, no curve
• Air
  • No wind
  • The air shares the same properties within the UAVs flight envelope.
• UAVs
  • Not sliding( sliding angle β=0), Coordinated Turn Model
  • AOA(angle of attack) is small
  • Rigid body

Modeling

Horizontal Plane

• Split this problem into horizontal plane and vertical plane!
• The formation control object:
  • Velocity of the follower is the same as the leader.
  • Position error is zero

Note: no sliding angle, no wind and small AOA, velocity is (almost) along the body-fixed axis X.

Vertical Plane

• In the vertical plane, the most important error is the height error, which is also called the Z position error.

Note: We mainly focus on the horizonal plane motion. So, we won’t take it as a part of error in the vertical plane.

Formation Controller Design

• Make use of the inner-loop controller, design the outer-loop!
• Input: the states of leader and follower.
• Output: the desired attitude setpoint and the throttle values of the follower.

Error Defination

• Why? Find the relationship between the errors and their corresponding controllable variables:
• X direction ==> velocity.
• Y direction ==> yaw rate.
• Z direction ==> height
• We want to eliminate both the position and velocity error at the same time!
• So, We define the linear combination of the position and velocity error as the “mixed error” along the X and Y axis in follower’s body-fixed coordinate system.
• We will use the height error as the error along the Z axis, treating the main motion as in the 2D plane.

Simulation Results

Copyright

Copyright (C) 2020 Aircraft Dynamics and Control Laboratory of BIT. All rights reserved.