Project SlyBot Introduction

 Quick Introduction

Project SlyBot is my venture into the world of robotics. I'm interested in the challenges involved in developing software systems to control movement and behaviour; so what better way to put them to the test than to build a robot! (also an excuse to play with Lego again ;) This page will follow my adventures as I work to develop both the hardware and software for various generations of a robot; namely SlyBot. Hopefully by the end of it, SlyBot will be fairly autonomous! The picture to the left shows SlyBot I - Phase I, still pretty early in the development cycle as you can see! Click it to see an enlarged version.

I will post here pictures and videos of the robots, and details of what has been learnt along the way. In due time I will make the control software available to aid others in their own robotics adventures!

 Aims and Scope

The overall aim is:

• To build a six legged robot with the ability to move and react independently of external controls.
• It will be able to move using various techniques and gates, and at varying speeds.
• Obstacles will be overcome or avoided, depending on height.
• The robot will be able to track where it has been, build up an internal map, and perform basic orienteering tasks using that data.
• Its initial primary goal will be to map where it hasn't been before.

Hardware wise, initially the robot will be built from technic Lego, use SuperTek/GWS servos and a 12 channel servo driver. As things develop it will use a Sharp Zaurus (running Linux) to host the control software, and use an I2C servo controller and sensors for input.

 Build Project Progress

The following outlines roughly where I want this project to go. I've split the development into a number of phases, each providing a significant advance in functionality over the previous.

Further phases will follow!

 Developed Robots

SlyBot I - The first generation of SlyBot!

 Control Software (RaSCL)

 RaSCL - Robotics and Sensorial Control Language

One of the main drivers I have for this SlyBot project is to experiment with control software. My background is in software, but whilst I have been developing SlyBot one hurdle I've had is the hardware and electronics side. For other robotics hobbyists and enthusiasts, the barrier may be automation; they have a robot, but no idea how to get it to do something useful!

This is where RaSCL comes in; Robotics and Sensorial Control Language. RaSCL is a high level yet powerful language to aid interaction between a PC/PDA and servos/sensors. It is by no means meant to be embedded; it aims to provide a generic platform to develop algorithms such as walking gait and collision avoidance, and present them in a markup that users can swap and customise.

For SlyBot I will be running this software on a Linux based Zaurus PDA. However, the major advantage this has is that an interpreter will also be available for Windows, so you can prototype your own control software on the desktop. My goal here is so that users with a servo controlled robot can download the interpreter, configure their controller encodings (or use a pre-defined one), plug in the serial cable, and call the in-built routines to get their bot to move! They are then free to customise the routines to their needs.

Learn more from my RaSCL project page!

 RaSCL - Language Outline

• Interpreted Lisp like language
• Object like interactions/abstractions
• Controller encodings defined in RaSCL; no re-compilations
• Servo/resource abstractions - let RaSCL deal with all the details!
• Easy debugging
• Abstracted definitions; users can share common routines like walking gaits etc
• Supports Linux/Windows
• Resource sharing/locking/deadlock avoidance built into the language
• Multiple jobs - threads of control to deal with each individual aspects of your robot
• Job communication - easy inter-job communication
• Scope for inter-bot communications via TCP/IP

 Short RaSCL Code Example

The following gives a flavour for the language: this function sets all configured servos to a given position at a given speed, and waits for all servos to complete their move before returning.

To make sense of the following you may need to know:

• The code defines a function called set_all_servos
• The function is passed a list of two arguments, the target position and the speed
• A pre-defined list called gBotServos contains pointers to all configured servo objects
• The *lServo::setpos command executes an operation on a servo object
• The primitive ::= sets a variable in the local context

Learn more from my RaSCL project page!

(::*complex_function set_all_servos)

    # Split out params - icar extracts an item from a given list index position
    (::= .lPos (icar func_args 0))
    (::= .lSpeed (icar func_args 1))

    # Following defines a variable to be the empty list
    (::= .lTimes {})

    # For each servo
    (::foreach gBotServos)

        # Each servo pointer will be in iItem - split it out
        (::= .lEntry iItem)
        (::= .lServo (dynamic_cast (car lEntry)))

        # This instructs the servo to move. The setpos method on a Servo object returns the
        # time it will take to move that servo, given its last position and the specified speed.
        # The resulting times are appended to the end of the lTimes list.
        (::= .lTimes (carpush (*lServo::setpos (list lPos lSpeed)) lTimes))

    (::endforeach)

    # Sleep until the servo with the longest distance to move has completed.
    (::sleep (max lTimes))

(::endfunc)

 Robotics Resources

General Hardware
• Active Robots: Lots of servo/sensor/robot goodies (very good service too!)
• Pandan Models: Good for servo extras (also very good service!)
• Milford Instruments: Various controllers and sensors
• ServoCity.com
• TotalRobots.com: Various electronics bits and pre-built robots
• Maplins.co.uk: Generic electronics


Tutorials/Guides
• Introduction to RC Servos


Zaurus PDA
• IPKGFind: Find those packages


Lego!
• BrickLink.com: Online Lego trading - no more digging around in boxes!
• CharlieChoppers: Good Lego store (on BrickLink) - recommended