Introducing the Quadrotor Flying Robot - Meetupfiles.meetup.com/1366773/Quadrotor Meetup... ·...

Introducing the Quadrotor Introducing the Quadrotor Flying RobotFlying Robot

Roy BrewerOrganizer

Philadelphia Robotics Meetup GroupPhiladelphia Robotics Meetup Group

August 13, 2009

13 Aug 09 2R. Brewer - Philly Meetup Quadrotor

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


What is a Quadrotor Used For?● Fun radio controlled “toy”● Aerial Photography / Video● Surveillance● Robotics and/or Control Systems Research


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 Roll/PitchControlling Roll/Pitch

Controlling AltitudeControlling Altitude

Controlling YawControlling Yaw


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!


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/indoorFlying.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!


Skills / KnowledgeMy 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


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


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


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


Math Model / Scicos Simulation


Custom Controller Card * 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.

● http://sites.google.com/site/pushpakquadrotor


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


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

Quadrotor

SensorsComp.Filters

R/C Joystick

OrLaptop

AttitudeCommand

RotorMixing

PID/Other

Feedback

VelocityCommand

PID/Other

Feedback+ -

+-

Software


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.


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


Complementary Filter Design - 1

1/s

1/s

+

+

+

+

-

k*k

2*k

11

22

11

Gyro (deg/s)Gyro (deg/s)

Accel (deg)Accel (deg)

SCICOS Model


37.0 37.5 38.0 38.5 39.0 39.5 40.0 40.5 41.0-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

2nd Order Complementary Filter

T im e (sec)

Atti

tude

(deg

) & R

ate

(deg

/s)

Gyro

Accel

Fi l ter

T rue Angle

Complementary Filter Design - 2


The Bigger Picture


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

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