IAB-RCInverted Autonomous Balancer

Remote Controlled

April 18, 2008

Jude CollinsChristopher Madsen

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

Robot overview

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

Robot system overview

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)

PID Controller

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

Remote Control

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)

Control Flow

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 ?????

Schedule

Date Goal (Wireless controller) Goal (Robot)

February 8, 2008 Functioning prototype robot

February 15, 2008 N64 Controller prototype Math model complete

February 22, 2008 N64 Controller testing completeDecision on use and design ofencoders

February 29, 2008Make provisions for wireless controllercommunications

March 7, 2008N64 Controller communicationscomplete

N64 Controller communicationscomplete

March 14, 2008 Preliminary Design Presentation Preliminary Design Presentation

March 21, 2008Incorporate other wireless devices(PDAs, etc)

Robot can lay itself down gently

March 28, 2008 Robot can "pop a wheelie"

April 4, 2008 Bigger batteries?

April 11, 2008 Final Testing - Hand it over to mom.

April 18, 2008 Demonstration Demonstration

Finances—RobotItem Type Quantity Individual Price Item Total

Gearhead Motors 12v Globe Motors #415A410 2 ~$25.00 ~$50.00

Wheel Mounts 5mm RC Airplane propellerholder

2 ~$8.00 ~$16.00

Wheels 15500 Golden Age5" (WBR15500)

2 (one pack from RC hobbies) $13.23 $26.46

Frame Aluminum (L shaped and flatpieces from Home Depot)

---- ~$3.00 ~$10.00

Microcontroller MSP430 (on Softbaugh B169breakout board)

1 $49.00 $49.00

Bluetooth Controller Sparkfun WRL-08461breakout board based onNXT's BGB203

1 $59.95$59.95

Inertial Measurement Unit

Sparkfun SEN-00741breakout board based onAnalog Device's IDG300 2axis rate gyro and ADXL330 3axis accelerometer

1 $109.95 $109.95

H-Bridge LMD18200 2 $14.40 $28.80

Voltage Regulator LM317 1 ~$1.00 ~$1.00

Resistors and capacitors ---- ~$1.00 total $1.00

Batteries NiCd 9.6v batteries 2 $8.00 $16.00

Total: $368.16

Finances—Remote Control

Item Type Quantity Individual Price Item Total

Nintendo64 Controller Original Nintendo 1 ~$10.00 ~$10.00

Bluetooth Controller Sparkfun WRL-08461breakout board based onNXT's BGB203

1 $59.95 $59.95

Voltage Regulator LM317 1 ~$1.00 ~$1.00

BJT Transistor 2N3904 1 ~$1.00 ~$1.00

20 MHz Crystal Oscillator ?? Japan Made 1 $2.00 $2.00

Capacitors and Resistors ----- ----- ----- ~$1.00

Microcontroller ATMEGA8515L 1 $5.27 $5.27

Total: $80.22

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

Questions?