1. Quadrocopter
Kyle Bartholomew

2. What is a quadrocopter?
• Like a helicopter with 4 blades.
• 2 blades spin clockwise, 2 spin
counterclockwise = zero net torque
• Motion Control Unit
– Keeps the copter stable without human
control.
• Power system
– Based on lithium polymer battery

3. Power System
Motors
+
-
Motor Controllers
LiPo Battery
5V
Regulator
Arduino

4. Outrunner Brushless Motors
AC Power

5. Motion Control Unit
• Miniature computer (Arduino microcontroller)
– Runs at 16Mhz (Your computer runs about 200 times
faster)
– Takes electrical signals in, does math, spits out more
electrical signals.
• IMU – Inertial Measurement Unit – 3-axis gyroscope and
accelerometers.
Motor Controllers
Arduino
RF Receiver
IMU

6. Accelerometers or Gyros?
• What do you use to measure the angle of
the copter relative to the ground?

7. 3.3V
Accelerometers
• 3-axis, measures acceleration
– When incidental acceleration is
small enough, it measures just the
acceleration of gravity.
– Absolute angle relative to earth.
• Highly susceptible to noise:
∆0.11V = ∆30°
10 bit ADC = 1024 steps of
measurement
3.3V/1024 = .00322V/step
1g
1.95V
1g
0g
30deg
0g
1.65V
1.65V
(30°/0.11V)*(.00322V/step) =
0.88°/step
0V

8. Gyroscopes
•
•
•
•
3-axis, measures angular velocity (w)
Integrate w over time to get angle
Good at instant angle measurements
Bad at absolute angle measurements
because it drifts.
• Small error in w leads to big error over
time.

9. Combining measurements
• You want best of both with
– High speed low noise measurements
– Accuracy over long periods of time

10. Complimentary Filter
• Combines accelerometer and gyro to
produce a better angle measurement.
• High pass filter on gyro and low pass filter
on accelerometer.
• Aka only long term for accelerometer and
only short term for gyro.

12. PID Control
• Need to go from angle to motor output.
• Based on idea of error from setpoint.
• The ideal method is PID control –
Proportional Integral Derivative.
• Proportional – Controls the now
• Integral – Controls by looking at the past
• Derivative – Controls by looking forward to
the future.
Error = θdesired-θcurrent

13. Complimentary Filter
Accelerometer
Low Pass Filter
Angle
Gyroscope
PID
P Coefficient
Integration
High Pass Filter
Integration
Derivative
I Coefficient
D Coefficient
Motor Output (200hz)

14. How does it move?
CW
Hint: r X F
CCW
CCW
CW

18. I•ɑ

19. Going further
• Many people add other fancy things to
their quadrocopters:
– GPS
– Altitude Sensor (Barometer)
– Camera
– FPV (First Person View)
– Tracking Systems to do crazy stuff like flips
and multiple copter coordinated dances.