Tom and Jerry

1
Tom and Jerry
EEL-5666 Intelligent Machines Design Lab

• By Nicholas Johnson Joshua Hartman

2
Overview

• Overall Function
• Toms Design
• Jerrys Design
• Special Sensor RF Link
• Conclusions
• Possible Improvements
• Questions

3
Overall Function

• Jerry and Tom simulate a Predator / Prey Model.
• Jerry is the prey and has prey behaviors such as
  wandering and grazing.
• Tom is the predator and searches for Jerry.
• When Tom detects Jerry he will try to capture
  Jerry who tries to run away.

4
Tom
5
Platform

• MAVRIC-IIB Development board
• Wood
• Cardboard part stands
• Black duct tape.
• Black duct tape.
• More black duct tape.

6
Locomotion

• GHM-03 Spur Gearhead Motor
• TPIC0107B-based motor driver
• These motors are fast

7
Obstacle Avoidance

• 3 Devantech SRF05
• Use fuzzy-logic ideas to define obstacles as
  close, far, or in between
• Very rarely hit obstacles

8
Searching for Jerry

• Futaba S148
• Panasonic PNA4611 Infrared Photo IC
• Servo rotates from -45o, -22.5o, 0o, 22.5o,
  45o
• At each location, reads A/D and detects if
  valuelt200. If so, Jerry is detected!

9
Searching for Jerry II

• IR detection not so easy
• Must use ADC to read photo IC output
• Vout goes low upon detection
• Must have receiver highly shielded to give
  directional output

10
Jerry
11
Platform

• Material Wood
• Cut using the T-Tech
• Small, Compact Design
• Had to be smaller than Tom
• Limited Space
• Difficult to fit all the electronics
• Addition of unforeseen pieces problematic

12
Actuation

• 2 Tamiya 70168 Double Gearboxes
• 114.71 Gear Ratio
• 4 wheels total
• Driven by TPIC0108B PWM H-Bridge
• Wheels on either side function independently
• Each side driven by 1 Motor Driver
• Servo Motor to turn Tom Detector

13
Sensors

• Bump Switches
• 2 Front, 2 Back
• Maxbotix Ultrasonic Rangers
• 2 Front, 1 Back
• IR Emitter / Detector (Close Range)
• 56.8 KHz IR Detector
• 315 MHz RF Receiver
• 434 MHz RF Transmitter

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Sonar

• Provides analog interface
• The higher the voltage the further away the
  object.
• Start time of each sonar can be controlled.
• Readings obtained 50ms after start.
• Sequentially check each sonar
• If returned value below threshold then obstacle
  detected.

15
Jerrys Design Close IR

• Analog output
• Brighter areas give lower voltages.
• If returned value above threshold then obstacle
  detected.

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Jerrys Design - Behaviors

• Wandering
• Randomly moves around avoiding obstacles.
• If food (black spot) is detected it will switch
  to grazing behavior.
• Frequently looks for Tom.
• If Tom is detected it will immediately switch to
  running behavior.

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Jerrys Design - Behaviors

• Grazing
• Holds on top of food for a preset time.
• Will slowly move across the food until passes it
  completely.
• Infrequently looks for Tom.
• If Tom is detected it will switch to running
  behavior.

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Jerrys Design - Behaviors

• Running
• Moves away from Tom as fast as possible.
• Turns frequently in order to escape Tom.
• If caught, will stop and wait to be reset.
• If preset time has gone without being caught will
  return to wandering behavior.

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Special Sensor - RF Link

• www.sparkfun.com
• Tom
• 434MHz Receiver
• 315MHz Transmitter
• Jerry
• 315MHz Receiver
• 434MHz Transmitter
• Links used to communicate robot status to
  determine exhibited behaviors.

20
RF Link Difficulties

• Receiver designed to lock on to signal.
  Therefore, sender must transmit alternating bits
  for receiver to lock onto the baud rate.
• Receiver will increase gain until it finds a
  detectable signal. Therefore, it will output
  garbage if the transmitter is not sending.

21
RF Link difficulties

• Receiver must synchronize with transmitter. If
  a transmission looks like 0 0 0 1 0 1 1 0 1 0 1
  0, the USART has no real way to recognize the
  start of a transmission. Over a wired link, the
  line is usually high and is pulled low using the
  start bit. This is not the case in RF.
• Finally, the receiver has a band-pass filter
  centered at its tuned frequency. When the robots
  get far enough away, this is washed out by the
  local transmitter.

22
RF Link Algorithm

• Use interrupts to continually send 0xAA, the
  locking code.
• When want to transmit, send out 0xFF to
  resynchronize the link
• Finally, send out data.

23
Conclusions

• Both robots successfully avoid obstacles.
• Wireless successfully incorporated.
• Tom successfully detects Jerry and will head
  towards him.

24
Possible Improvements

• More reliable detection method.
• IR not always reliable and dependent on
  environment.

25
Questions?

• Acknowledgements
• Dr. A. A. Arroyo
• Dr. E. M. Schwartz
• Julio Suarez
• Adam Barnett
• Thomas McDonley
• Jason Taylor