tom and jerry

Tom and Jerry

By: Nicholas Johnson & Joshua Hartman

EEL-5666 – Intelligent Machines Design Lab

EEL-5666: Intelligent Machines Design Lab

Overview

Overall Function Tom’s Design Jerry’s Design Special Sensor – RF Link Conclusions Possible Improvements Questions


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.


Tom


Platform

MAVRIC-IIB Development board

Wood Cardboard part stands Black duct tape. Black duct tape. More black duct tape.


Locomotion

GHM-03 Spur Gearhead Motor

TPIC0107B-based motor driver

These motors are fast


Obstacle Avoidance

3 Devantech SRF05 Use fuzzy-logic ideas to define

obstacles as close, far, or in between

Very rarely hit obstacles


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 value<200. If so, Jerry is detected!


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


Jerry


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


Actuation

2 Tamiya 70168 Double Gearboxes 114.7:1 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”


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


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.


Jerry’s Design – Close IR

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

detected.


Jerry’s 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.



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.



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.


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.


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.


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.


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.


Conclusions

Both robots successfully avoid obstacles.

Wireless successfully incorporated. Tom successfully detects Jerry and will

head towards him.


Possible Improvements

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

environment.


Questions?

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

tom and jerry

Documents

tom detectoreel

motor driverservo motor

jerry iiir detection

standsblack duct tape

rf transmittereel

rf receiver434

predator prey model

prey behaviors