1. SAE Aerospace Guidance & Control Committee Meeting
Control Science Center of Excellence Overview
SAE Aerospace Guidance & Control Committee Meeting
17 Oct 2008
Dr. David B. Doman
Control Design and Analysis Branch
Air Vehicles Directorate
Air Force Research Laboratory

2. Changes in AFRL/RBCA
While in the previous charts I presented generic clhallenges in autonomous control, here I am going to concentrate more on the mechanics of flapping flight because the application and research has barely scratched the surface.

3. The AFRL MAV Vision
While in the previous charts I presented generic clhallenges in autonomous control, here I am going to concentrate more on the mechanics of flapping flight because the application and research has barely scratched the surface.

4. Micro Air Vehicle (MAV) Control Research Objectives
Enable stabilized and controlled flight for flapping MAVs designed for warfighter support
Insect-like maneuverability, hover, forward, backward, lateral movement
Deliver flight control and trajectory generation capabilities to enable perching on fixed object in the presence of disturbances
While in the previous charts I presented generic clhallenges in autonomous control, here I am going to concentrate more on the mechanics of flapping flight because the application and research has barely scratched the surface.

5. Insect Scale Flapping Wing Vehicles
RoboFly built by Prof. Robert Wood of Harvard University
First flight of insect scale flapping wing vehicle
3 cm wingspan, 60 mg mass
Passive wing rotation, single piezo-electric actuator
Off-board power, no sensors
Uncontrolled flight up a wire
Elegant design, minimal actively controlled elements
AFRL undertaking analysis of 6 DOF experimental vehicle
Independently actuated wings
C.G. controlled via piezoelectric
Passive 6 DOF sensors via Vicon
Use to develop control strategies
Credit: Robert Wood, Harvard University
Passive vs active actuator
Piezoelc crystal – wing motion
Power on or off board

6. Hardware-in-the Loop Control Experiments
Build MAV with two independently actuated wings with passive wing rotation
Use MAV 6 DOF test stand to measure forces and moments to verify hypotheses
Why do this:
Account for modeling errors due to use of blade element theory
Test feedback control
Examine effects of amplitude modulation and mixed frequency/amplitude modulation of wing motion
Examine effects of waveform shape on forces and moments
Quantify coupling between moments for insight into control allocation
Forces
Moments
FW MAV EOMs
DAQ
DAQ = data acquisition (measure forces and moments from voltages)
FW MAV = flapping wing MAV, EOM = eq of motion
Objective of the experiment: to track an X, Y, Z position (command following)
If we have the right power source (a light weight battery and DC to DC converter to step up the voltage for helping piezo actuator to do its function), a sensor to detect where it is (VICON can help with this), radio frequecny (RF) antenna for talking to a ground computer, then we can demo a free flight indoors.
Wingbeat Parameters
Control Law
Real-Time Data Acq, Sim & Ctrl
DAQ = Data Acquisition
FW = Flapping Wing
EOM = Equations of Motion

7. Experimental Verification of Control Strategies
Run altitude control test for “Bug on a Wire”
RoboFly class MAV, Single Actuator
Passive altitude/altitude rate sensors using Vicon cameras
Off-board processing, off-board power source, wire power transmission
Verify feasibility of FM-based control law
Closed-Loop Wingbeat Frequency Modulation
Reduced Velocity
Increased Velocity
Wing position
Run 6 DOF flight control tests on modified RoboFly class MAV
Independently controlled wings/passive rotation
CG actuator
Split-cycle constant-period frequency modulation
Two expts.
One with Rob’s vehicle: motion along a wire with feedback control using one actuator.
The other: Rob’s vehicle gets modified with two actuators independently controlling the wings plus a 3rd actuator to change CG location (probably by wiggling the end of the tail and this will give pitch control).
Roll: vary freq
Yaw: split cycle freq modulation (move forward and backward at different rates)
Translation: move forward or backwards thru split cycle freq modulation
We can’t get pitch unless you use a 3rd actuator
Either you change downwash in conjunction with the flap, or change CG location (by shifting the mass by flipping a small bob like device, like some insects do) to get pitch control.
Symmetric wing beat
Time (fixed period)
Maneuvering via Split-Cycle Constant-Period FM
Roll
Slow Translate
Yaw

8. Indoor Flight Test Facility
AFRL MAV Laboratory Capabilities:
Vicon Camera system for position/attitude measurement
Rapid flight control prototyping & analysis using LabView Real-Time Deployment Option & Matlab/Simulink with Real-Time Workshop
Helicopter Flight Test Purpose:
Debug hardware and software using COTS MAV prior to flapping wing experiments.
Helicopter Wand Following/AFRL MAV Lab July 2008
Vicon Cameras give position, roll, pitch and yaw information of the vehicle.
LabView is a block diagram programming language to compute control laws in real time.
COTS: Commercial off the shelf helicopter.
We were able to fly using a commercial off the shelf helicopter in less than 24 hrs in our test facility. - +
Single channel of control law
Outer-loop: Position command, Inner-loop: Attitude command

9. Plans for the Near Term
AFRL Current Plan of attack for MAV flight control
Simple first principles modeling to develop control strategies
Experimental testing to correct blade-element aero models for unsteady effects
Incremental flight testing from “Bug on a Wire” to 6 DOF
AFRL indoor flight test facility allows focus on MAV control challenges
Passive inertial sensing using Vicon Motion Capture System gets sensors off of the MAV
Off-board flight control processing eliminates weight and enables rapid flight control prototyping
Off-board power for piezoelectric actuated aircraft
Translation of flight control commands from real-time computer to RF transmitter signals for MAVs
Allows progress on flight control front while battery and sensor technology are advancing
Right combination of tools to make progress toward objective of enabling insect-like maneuverability for MAVs