Introducing the Quadrotor Introducing the Quadrotor Flying Robot - PowerPoint PPT Presentation

Introducing the Quadrotor Introducing the Quadrotor Flying Robot Flying Robot Roy Brewer Organizer Phila ilade delph lphia ia Robo Robotic ics s Meet etup up Group up Phila ilade delph lphia ia Robo Robotic ics s Meet etup up Group up August 13, 2009

What is a Quadrotor? ● A vehicle having 4 rotors (propellers) at each end of a square cross ● Typically remote controlled; can be autonomous or semi- autonomous ● Home built, research, and professional versions exist ● Typically built using r/c components, electric motors, microprocessors, servos, sensors, batteries 13 Aug 09 R. Brewer - Philly Meetup Quadrotor 2

What is a Quadrotor Used For? ● Fun radio controlled “toy” ● Aerial Photography / Video ● Surveillance ● Robotics and/or Control Systems Research 13 Aug 09 R. Brewer - Philly Meetup Quadrotor 3

How Does a Quadrotor Fly? • Rotor thrust and torque proportional to rotor speed squared • 2 sets of counter rotating blades. • Torque inherently balanced • 4 inputs allow independent actuation of pitch, roll, yaw and thrust Controlling Altitude Controlling Altitude Controlling Yaw Controlling Yaw Controlling Roll/Pitch Controlling Roll/Pitch 13 Aug 09 R. Brewer - Philly Meetup Quadrotor 4

How to Obtain a Quadrotor? ● Buy – http://www.asctec.de – http://www.microdrones.com – http://www.draganfly.com ● Build (existing kits & plans) – http://aeroquad.info/bin/view/Main/WebHome – http://mikrokopter.de – http://uavp.ch/moin (Why are there so many German quads? :-) ● Comprehesive list: – http://multicopter.org/wiki/Multicopter_Table ● Design Our Own! 13 Aug 09 R. Brewer - Philly Meetup Quadrotor 5

University Research ● STARMAC – Stanford – http://hybrid.eecs.berkeley.edu/index.php?section=37 ● MIT – http://vertol.mit.edu/index.html ● EPFL – http://asl.epfl.ch/research/projects/VtolIndoorFlying/indoorFly ing.php ● Brigham Young – http://www.ece.byu.edu/roboticvision/HelicopterPlatform/Heli copterPlatform.html ● Many more... ● Many technical research papers available on-line ● Task is equivalent to B.S Eng Project up to PhD Thesis! 13 Aug 09 R. Brewer - Philly Meetup Quadrotor 6

Skills / Knowledge My contribution: Control Theory & Algorithms (PID etc.) ● I Have Some Knowledge of: Sensors (MEMs, GPS, Compass) ● Microcontrollers, Embedded Systems, & Software ● DSP / Filtering ● What I need to learn: Radio Control Equipment ● (Brushless) Motors & Servos ● Vision processing ● Airframe Design & Construction ● PC / ground station programming ● 13 Aug 09 R. Brewer - Philly Meetup Quadrotor 7

Personal Goals: ● Professional Development – UAV – Advanced Controls – Sensor Processing / Sensor Fusion ● Kalman, Complementary Filters, etc ● Personal – Microcontrollers – Embedded S/W – Electronics – Radio Control – Website / Blog / Magazine Articles 13 Aug 09 R. Brewer - Philly Meetup Quadrotor 8

Project Goals: ● Manual (Radio Control) Operation – Acrobatic mode: angular rate & thrust command – Stable Mode: Translational rate command / position and altitude hold ● Semi Autonomous Operation – Telemetry to Laptop-based ground station – Voice operation ● Fully Acrobatic ● Automatic P.I.D. Gain tuning ● Other – Provide Write-ups of Quad Dynamics, Control Loops (and theory), & S/W Design – Use Open Souce / Free S/W tools where possible 13 Aug 09 R. Brewer - Philly Meetup Quadrotor 9

Project Status ● Software – Math / Simulation Model ● Needs some work – drag models, etc. ● Good enough to begin code prototyping – Code ● About to prototype control ideas ● Hardware – Controller ● My friend Brijesh has designed, built and is testing a custom AVR ATMega644p based board: – Airframe, motors, ESCs, R/C gear, propellers, etc. ● Some ideas, but nothing yet purchased 13 Aug 09 R. Brewer - Philly Meetup Quadrotor 10

Math Model / Scicos Simulation 13 Aug 09 R. Brewer - Philly Meetup Quadrotor 11

Custom Controller Card ● http://sites.google.com/site/pushpakquadrotor * ATMEGA644p processor ( Same as Sanguino). * 20 MHz clock rate. * Serial port 1 : USB or Xbee link. o Arduino bootloader supported on both USB and Xbee links. * Serial port 2 : Venus GPS module from Sparkfun. * 4 Channel RC receiver input. Interrupt based de- coding. * 4 Channel Hardware PWM/Servo pulse. * Terminals to distribute power to 4 ESC's from battery. * 4 pole Butterworth Anti-aliasing filters on all sensors inputs. * Gyros o IDG500 Break out board connector (X and Y axis) + IDG500 output selectable between 100 Deg/sec or 500 Deg/sec via a jumper. o LISY300AL break out board connector (Z axis) * Accelerometer: Two options available o MMA7260 breakout board connector. (Ana- log outputs). o LIS302DL breakout board connector, (I2C in- terface). * Battery voltage monitoring. * 3inx3in Dimensions with 4 mountings holes. 13 Aug 09 R. Brewer - Philly Meetup Quadrotor 12

Technical Challenges - Control ● Airframe Dynamics Are: – Non-linear: ● 3-D Attitude (orientation): Trig functions, Singularities, Quaternions – Coupled: ● Translation requires attitude changes ● Attitude change requires thrust change to avoid altitude (height) change ● Many control schemes are employed – “Simple” Proportional Integral Derivative (PID) – More advanced non-linear concepts – Distributed control – split on-board and laptop 13 Aug 09 R. Brewer - Philly Meetup Quadrotor 13

Control Concept ● Acrobatic mode: Rate command/attitude hold; direct thrust command ● Precision mode: Velocity command/position hold;rate of climb command / altitude hold ● Autonomous commands (possibly via laptop over telemetry) ● Automatic or manual switching between modes R/C Joystick Or Laptop Software PID/ PID/ Velocity Attitude Rotor + - Quadrotor Other + - Other Command Command Mixing Feedback Feedback Comp. Sensors Filters 13 Aug 09 R. Brewer - Philly Meetup Quadrotor 14

Technical Challenges - Sensors ● Must sense position & orientation to control them ● Gyroscopes – Sense angular rates – Suffer from bias – Must be integrated to determine attitude – Usable only in a medium frequency range ● Accelerometers – Sense linear acceleration – Very noisy – Gravity must be handled carefully – Useable only in a low frequency range ● Other sensors: – GPS, Sonar, Magnetometer/Compass, Vision, etc. 13 Aug 09 R. Brewer - Philly Meetup Quadrotor 15

Sensor Fusion ● Complementary Filter – Concept: utilize each sensor over the frequency range where they provide good attitude data – Integrate and High Pass filter gyro data – Low Pass Filter accelerometer ATAN data – Tune filter based on data – Inverse of stereo woofer/tweeter network ● Kalman Filter – Contains model/observer/predictor – And corrector feedback loop with varying gain – Uses statistical parameters – Much more complicated to understand and implement 13 Aug 09 R. Brewer - Philly Meetup Quadrotor 16

Complementary Filter Design - 1 1 Gyro (deg/s) Gyro (deg/s) + + 1 2*k + 1/s + 2 k *k - Accel (deg) Accel (deg) 1/s SCICOS Model 13 Aug 09 R. Brewer - Philly Meetup Quadrotor 17

Complementary Filter Design - 2 2.5 Gyro 2.0 Accel Filter 1.5 T rue Angle Attitude (deg) & Rate (deg/s) 1.0 0.5 0.0 -0.5 -1.0 -1.5 37.0 37.5 38.0 38.5 39.0 39.5 40.0 40.5 41.0 T im e (sec) 13 Aug 09 R. Brewer - Philly Meetup Quadrotor 18

The Bigger Picture 13 Aug 09 R. Brewer - Philly Meetup Quadrotor 19

Other Links from the Meetup DIY Drones – UAVs - http://diydrones.com ● Sparkfun – Electronic Parts & tutorials - http://www.sparkfun.com ● Arduino – Microprocessors simplified - http://www.arduino.cc/ ● AVR Freaks – lots of info for AVR microprocessors ● http://www.avrfreaks.net Scilab/Scicos – Free Matlab clone - http://www.scilab.org; ● http://scicos.org; http://scicoslab.com Open Office – MS Office “clone” - http://www.openoffice.org ● Magazines ● – Nuts and Volts – general electronics - http://www.nutsvolts.com – Servo – robotics - http://www.servomagazine.com – Circuit Cellar – pro electronics - http://www.circellar.com – Elektor – UK electronics -http://www.elektor.com/magazines.46742.lynkx – Robot – robotics - http://www.botmag.com 13 Aug 09 R. Brewer - Philly Meetup Quadrotor 20