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

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.

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.

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.

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

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

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

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

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