Saturday, June 20, 2015

Introduction & Objectives

Overview

I have always been fascinated by robots and robotics. This blog will document the building of AVA. AVA is intended to be a fully autonomous robot which can react based on a number of layered behavioural patterns. I will go into the philosophy of behavioural based robotics in a subsequent post.

AVA's brains will be built using networked Arduino's. Arduino is an open-source electronics platform based on hardware which comes in a number of configurations based on your requirements and a free Integrated Development Environment (IDE) which allows you to program the microcontroller in C++.

The initial state of my robot prototype is shown in the following (overly dramatic) video.

video


Because I am using a behavioural approach to controlling the robot, Arduino's should give me sufficient computing power, relatively cheaply. Should I need more processing grunt the design will scale through the addition of a Raspberry Pi or PCDuino.

Even though the Arduino's have a pretty miserable clock speed (usually 16 MHz) compared to modern computer gear (e.g. even an iPhone 6 has a clock speed of 1.4 GHz), they are much better at controlling quickly changing inputs and outputs because that is all that they are doing.

Keeping with the spirit of the Arduino community, any software developed will be provided here with the appropriate permissive licences required for you to use within your own project.

Objectives

  1. Autonomous
  2. Has Voice Recognition and Voice Synthesis
  3. Knows - time, date, temperature, humidity, light level and battery charge.
  4. Will be able to perform the following tasks within a behavioural hierarchy (I will explain this):
  • Find Station and Recharge
  • Follow designated target
  • Remote control (telemetry) via WiFi
  • Patrol (challenge and video)

Micro Controllers

Master Controller



The Arduino's communicate using an I2C bus which requires only 2 wires. The master controller will be an Arduino Mega 2560 (Rev 3). Most of the sensors will connect to the Mega as will the motor control lines, quadrature encoders, voice recognition, voice synthesis and battery monitoring. I have actually used the Freetronics version of the Mega 2560 which is called the EtherMega. The EtherMega is a souped up version of the original design which includes ethernet functionality (which I'm not currently using but hey there is never such a thing as too much functionality and no doubt I will come up with some way to use it in the future). I have used Freetronics versions of the Arduino hardware where I can because of the additional functionality of their designs and to support a local Aussie company. I am going to use the Freetronic version names and official Arduino names interchangeably.

Logging, Sound Output and Input Controller



The next controller on the bus is a Freetronics "Eleven". This is a version of the Arduino Uno and controls the 128 x 128 pixel OLED Shield via the Shield Adapter. This shield includes a micro SD card, piezo buzzer and joystick controller which uses most of the digital input/outputs of the Eleven. The I2C bus connects to two of the analogue pins (A4 and A5) and the joystick position is monitored by two other (A2 and A3).

Interestingly (to me at least), the Eleven communicates with the OLED using a Serial Peripheral Interface (SPI) bus. So this Arduino is using two communication protocols at the same time, not to mention the serial interface used to program the chip via my Mac. The SPI is a 4 wire bus.

This controller will log status to the screen and microSD card, provide audio feedback via the piezo (until voice synthesis is added) and allow me to provide input via the joystick and button.



LCD and Temperature Sensor Controller


I have another Eleven connected on the I2C bus which controls a 2 x 16 character LCD via a LCD and Keypad Shield. This has a DS18B20 temperature sensor connected which uses the LCD to display the current temp. I only added this because I already had one built, but the temperature will come in handy when I add the sonar sensors since the speed of sound is effected by temperature (and barometric pressure). More on this in due course.



Real Time Clock (RTC) Module



To allow behaviours based on the time and date, the robot needs to know what the current date and time is. It is also useful for time stamping log entries. To allow this, there is a Freetronics  RTC module connected to the I2C bus.

I will do a separate post about each of the micro controllers and go into the hardware and setup configurations in depth.

Robot Platform

A robot is not much of a robot if it can't move. For AVA, movement will be provided courtesy of the Arlo Robotic Platform System from Parallax. The Arlo platform can carry up to 27kg so that should be sufficient for what I have planned.

Constructing the platform will be documented here.


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