Rambler Robot

The RAMBLER Robot

The RAMBLER Robot

To analyze RAMBLER we’ve built an inexpensive robotic platform: The RAMBLER Robot. The main components are the Pololu Zumo chassis, the Arduino UNO low-level controller, and the Raspberry Pi high-level controller.

Bill of Materials

From www.pololu.com:
$29.95 – Arduino Uno R3
$42.95 – Zumo Robot Kit for Arduino (No Motors)
$31.90 – 100:1 Micro Metal Gearmotor HP
$4.95 – Pololu Voltage Regulator S7V7F5
($109.75 subtotal)

From www.adafruit.com:
$39.95 – Raspberry Pi Model B 512MB RAM
$5.95 – Low-profile microSD card adapter for Raspberry Pi
$19.95 – Adafruit Pibow Enclosure
($65.85 subtotal)

From www.sparkfun.com:
$1.95 – Logic Level Converter
$3.95 – Jumper Wires Premium 6″ F/F Pack of 10
($5.90 subtotal)

From www.McMaster-Carr.com:
$23.21 – Optically Clear Cast Acrylic Sheet 1/8″ Thick
$8.50 – Pack of 50 Type 316 SS Pan Head Phillips Machine Screw 2-56 Thread, 1″ Length
$10.57 – Metric Nylon 6/6 Hex Nut Off-White, M3 Size, .5mm Pitch, 5.5mm W, 2.4mm H
($42.28 subtotal)

From www.amazon.com:
$15.49 – SanDisk Ultra 16 GB MicroSDHC Class 10 UHS-1 Memory Card
$19.10 – eneloop NEW 2000mAh Typical, 8 Pack AA Ni-MH Rechargeable Batteries
$9.99 – InstaMorph – Moldable Plastic – 6 oz
$3.70 – Everydaysource 2 Pack of right angle Adapter : Micro USB OTG
$15.95 – Edimax EW-7811Un 150 Mbps Wireless 11n Nano Size USB Adapter
$6.99 – AmazonBasics HDMI to DVI Adapter Cable (9.8 Feet/3.0 Meters)
($71.22 subtotal)

From www.Kogeto.com:
$39.00 – “Naked” Panoramic Dot iCONIC optic

From www.newegg.com:
$19.99 – inland 86200 USB 2.0 WebCam

Total: $353.99
We hope to add some antenna components later.

Maybe it’s not all that cheap, but if you have some of this stuff lying around already you might get the price down to $200. For example, we didn’t have any batteries, so that was $20, and we lost a single nylon hex nut, so that was $10. Keep your screws and nuts in a dish or something!

We have access to some great tools, like a 120W Epilog laser cutter, a Dremel high speed rotary tool, and a Weller soldering iron. Screwdrivers and small wrenches were also necessary for this project. For the thermoplastic molding, a method of heating water to near boiling is essential. To reproduce the cap nut based 360-degree vision system, a miter box or lathe, and some epoxy or another method of joining acrylic is needed.

 

Assembly Instructions

RAMBLER Robot is easy to build.

First, assemble the zumo chassis as per the instructions on pololu’s website. The Users Guide may be helpful.

Next, modify and assemble the pibow case. Details can be found in the appendices of Charles Hart’s 2014 thesis.

The USB camera setup relies on perfboard and a thermoplastic like shapelock or instamorph. It is also possible to use the newly released Pi Camera through the CSI (Camera Serial Interface) port on your Raspberry Pi.

The antennae are built with lasercut acrylic layers, accommodating two potentiometers and steel wire mounted in 3D-printed flanges.

Finally, program the arduino and load the raspberry pi with the code found in the next section. You will need the Zumo libraries found here.

 

RAMBLER Robot code

Our public github repository includes C++ code for the Arduino and the Raspberry Pi, as well as some scripts and configuration files for the Pi.

 

Pin Assignments

Digital pins Zumo Shield function Notes/alternate functions
0 digital I/O RX for programming and serial communication on Uno and older Arduinos
1 digital I/O TX for programming and serial communication on Uno and older Arduinos
2 digital I/O (front expansion) I²C SDA on Leonardo and A-Star 32U4 Prime
3 digital I/O optional jumper to buzzer control line for Uno and older Arduinos
I²C SCL on Leonardo and A-Star 32U4 Prime
4 digital I/O (front expansion) Status LEDs
5 digital I/O (front expansion) Status LEDs
6 digital I/O optional jumper to buzzer control line for Leonardo and A-Star 32U4 Prime
7 right motor direction control line
8 left motor direction control line
9 right motor PWM control line
10 left motor PWM control line
11 digital I/O (front expansion) Status LEDs, Mantis Claw
12 digital I/O user pushbutton (pressing pulls low)
13 digital I/O yellow user LED (high turns LED on)
Analog pins Zumo Shield function Notes/alternate functions
A0 analog input and digital I/O (front expansion)
A1 analog input and digital I/O (front expansion) optional jumper to battery level voltage divider
A2 analog input and digital I/O (front expansion) Whisker Left
A3 analog input and digital I/O (front expansion) Whisker Right
A4 analog input and digital I/O (front expansion) I²C SDA on Uno and older Arduinos
A5 analog input and digital I/O (front expansion) I²C SCL on Uno and older Arduinos

Methods and Discussion

Sensors: Magnetometer, Antennae, Camera.

Controls: RAMBLER algorithm

Actuators: We found the zumo chassis to be an excellent platform. The wheelbase was a little short, and the number of IO pins on the arduino was a little low, but as a whole it all turned out great. The 100:1 gear reduction on the motors seems ideal.

 

Future work

RAMBLER-Robot in Nymph mode

RAMBLER Robot in Nymph configuration

The RAMBLER Robot has been repurposed by students to act more like a cockroach nymph, and a mantis version is in the works, to be finished in the summer of 2015.

 

Videos

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