Gyrobot a Two Wheel Balancing Robot

1. 4/9/2012 1 Gyrobota Two Wheel Balancing Robot Larry Barello Introduce yourself. 5 years making hobby robots: Minisumo, Fire fighting, Line maze now balancing FIRST the source of the Gyro and inspiration to attempt this. Introduce yourself. 5 years making hobby robots: Minisumo, Fire fighting, Line maze now balancing FIRST the source of the Gyro and inspiration to attempt this.

2. 4/9/2012 2 How Balancing Works Easier to balance high GC object. The Devil is in the details. Demonstrate balance stickDemonstrate balance stick

3. 4/9/2012 3 How Balancing Works Restoring Torque = ? * K? ? = Angular rate (deg/sec) K? = some factor based upon robot mass & moment arm. Demonstrate balance stickDemonstrate balance stick

4. 4/9/2012 4 How Balancing Works Balance torque = M * g * sin(angle) M is moment arm (center of mass & distance from pivot). g = acceleration of gravity Angle is deviation from balance point Demonstrate balance stick Point out that simple P term is not enoughDemonstrate balance stick Point out that simple P term is not enough

5. 4/9/2012 5 Controlling Drive Torque As velocity increases, DC motors have less torque (back-EMF) Need to correct this so balance equation can work. Positive velocity feedback Drive = drive + Kv * velocity Kv = factor based upon motor specification.

6. 4/9/2012 6 The robot tilts in the direction of movement. How to move

7. 4/9/2012 7 Tilt Sensor Gyroscope measures Rate Of Turn. Integrate for angle Gyroscopes drift Drift changes withtemperature Describe FIRST, pass around the sensor + Data sheet. Tune balance bot (or attempt)Describe FIRST, pass around the sensor + Data sheet. Tune balance bot (or attempt)

8. 4/9/2012 8 Tilt Sensor Accelerometers measure gravity. Affected by movement. Very accurate. Pass around data sheet. Describe the real problems (too sensitive, linear acceleration) (do we need another foil?)Pass around data sheet. Describe the real problems (too sensitive, linear acceleration) (do we need another foil?)

9. 4/9/2012 9 Fusing Gyro and Tilt sensors Weighted Average Filter. Use fraction of error between tilt and gyro Add to integrated Gyro output. Results are fast & drift free The weighted average IIR filter technique can be used to smooth out any noisy signal. This is where I want to go.This is where I want to go.

10. 4/9/2012 10 Fusing Gyro and Tilt sensors Weighted Average Filter. Tiltgyro = Sum(Gyro � Offset) Tiltaccel = sin-1(x/g) Tiltgyro = Tiltgyro + (Tiltaccel � Tiltgyro) * K This is where I want to go.This is where I want to go.

11. 4/9/2012 11 Alternate to Tilt Sensor Pass around the paper on Complementary filtersPass around the paper on Complementary filters

12. 4/9/2012 12 Motion Sensor Encoders measure position and velocity of wheels. Dead reckoning can be derived from encoders and the robots position determined in X, Y and Theta. Quadrature encoder: Two sensors, direction & count.Quadrature encoder: Two sensors, direction & count.

13. 4/9/2012 13 Current Status Motion control not implemented. Navigation disabled. Remote control (Radio link) not implemented. Using acceleration to correct tilt not tried. In short, it doesn�t do anything interesting yet. Future: Put fan & candle sensors on board and make it a balancing fire-fighting robot.Future: Put fan & candle sensors on board and make it a balancing fire-fighting robot.

14. 4/9/2012 14 Additional reading Robots & controls www.barello.net/Papers/Motion_Control Pendulum Joe http://leiwww.epfl.ch Data sheets http://www.systron.com/prodinfo/AQRS.html http://products.analog.com/products/info.asp?product=ADXL202