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April 18, 2008 Jude Collins Christopher Madsen. IAB-RC Inverted Autonomous Balancer Remote Controlled. Final Presentation. Technical aspects of the robot Prior art Schedule Finances. Overview. Robot system overview—Chris Capabilities How it works Robot hardware Remote control—Jude
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April 18, 2008 Jude Collins Christopher Madsen IAB-RCInverted Autonomous BalancerRemote Controlled
Final Presentation • Technical aspects of the robot • Prior art • Schedule • Finances
Overview • Robot system overview—Chris • Capabilities • How it works • Robot hardware • Remote control—Jude • Controller hardware • PC • N64 Controller • PDA
Overview • Literature/product search—Chris • “Trajectory Tracking Control for Navigation of Self-contained Mobile Inverse Pendulum” (1994). • Segway (2002). • David P. Anderson's “nBot” (2003). • Schedule and finances—Jude • Questions
Capabilities • Balance • Stand up • Lay down • Slide • Jump curbs • Crash • ?????
How does it work? • Hardware calculates “lean” of the robot • Wheels turn to prevent “lean” • Forcing the robot to lean causes the robot to drive • The robot learns to lean into external forces to keep balanced • Spinning one wheel faster than the other causes the robot to turn • Kicking the robot may make the robot angry
Microcontroller • MSP430F1611 • Running 4 MHz • 12 bit A/D with 8 pin-accessible inputs • Two 16 bit timers • 1.8-3.6v • Programmed in C
Inertial Measurement Unit • IDG-300Gyroscope • ADXL-330Accelerometer
IDG-300 Gyroscope • Dual-Axis rate gyroscope • Operates by oscillating masses and capacitively measuring vibration caused by Coriolis effect. • Sensitivity: 2 mV/deg/s • Max rate: 500 deg/s • Operating voltage: 3.0-3.3v
ADXL-330 Accelerometer • Triple-axis accelerometer • Micro-machined structure suspended over silicon by polysilicon springs. Plates mounted on moving structure and a fixed structure act as a variable capacitor in a filter circuit to measure acceleration. • Sensitivity: ~300mV/g • Max acceleration: ±3.0g • Operating voltage: 2.0-3.6v (sensitivity is ratiometric)
Estimating pendulum orientation • Integrating rate gyros is subject to drift errors. • Accelerometers only work to determine orientation when not accelerating. • Using both estimates together gives better estimate of orientation.
Bluetooth Radio • Basically a breakout board for NXP's BGB203. • Class 1 so has a 100m range • 100 mW max transmitted power • 3.3 volts • 1 Mbps max UART
Computer • Communicates via Bluetooth dongle • Used for early verification of control law • Jitter in transmission limited stability
The Remote Control • Needed Peripherals • Joystick • A few buttons • Modify old N64 controller. • Exceeds requirements • Cheap ($5-$15 on Amazon.com)
The microcontroller • Needed peripherals • UART • High clock frequency • Low Vcc • ATMEGA8515L • UART • 20 MHz • 2.7 – 5.5 V • Low Cost ($3.06-$5.27 Digikey.com)
PDA • Can also be used to remotely control robot. • And ?????
Prior art • First appearance of similar two-wheeled inverted pendulum that can navigate in 2 dimensions on a plane: “Trajectory Tracking Control for Navigation of Self-contained Mobile Inverse Pendulum” by Yunsu Ha and Shin'ichi Yuta of Japan in 1994. • Position encoders on wheels (2000 step) • Sensors to detect obstacles • No remote-control
Prior art • Segway • Most popular inverted-pendulum type product. • Patented just about everything imaginable concerning inverted pendulum human transportation. • Have several Robotic Mobility Platform (RMP) models
Prior art • David P. Anderson's nBot • Received NASA's Cool Robot of the Week award and subsequently became well-known in the minds of robotics enthusiasts (2003). • Launched a revolution of inverted-pendulum robot building. • Homebrew shaft encoders.
How are we different? • Back EMF encoders rather than mechanical encoders. • Bluetooth radios enabling hardware-in-the-loop simulation. • Stands up autonomously. • Lays itself down gently. • And ?????
Finances • Allotted budget: $1000 • Expenditures: ~$500 • Main expenses: • 1 IMU -- $110 • 2 Bluetooth radios -- $120 • 1 MSP430 on breakout board -- $50 • 2 Motors and H-Bridges -- $80