[A graphic saying Shadow Liberator]
Document created: 12th December 1999
Last Modified: Wednesday, 21-Aug-2013 17:10:20 BST
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Early on in the development of the Biped Walker there were several people who wanted to work on an intelligent hand eye system but it was clear that it would be some time before the walker would be a suitable platform.
With that in mind I designed Liberator so that work on vision could proceed using a basically human shaped robot: It takes up about the same floor space as a human and with a camera mounted on the top would be about 5ft 2in tall (no eyes of blue though, yet!). A shoulder plate mounted on the top of a thin body provides a mounting point for experimental arms. It was designed to unbolt into sections so I could get it into my car.

Annotated picture of Liberator robot

A Platform For Vision

Our previous vision guided robots had crawled about on the floor attached to a computer by an umbilical which also supplied power and as everybody knows (sooner or later) umbilicals just get tied in knots, wrapped round wheels, get caught in things, you think of it - it happens. So Liberator had to be self contained. The plan was to transmit the video signals to a receiver attached to a computer, get the computer to figure out what to do and send the control signals back to Liberator, however that part never got built and so for higher level processing Liberator still needs to have an umbilical.

Today Liberator consists of a base unit with two drive wheels and two castors in a wheelchair arrangement. The two motors came from Autopolisher units (from Halfords?) and each drive a wheel through a toothed belt reduction drive, power is supplied from a 12 volt 20 Ah sealed lead acid battery positioned between the drive wheels. Also on board is the necessary battery charger and a distribution panel with switches and fuses etc. Around the perimeter of the base are sensor plates through which Liberator can detect if it is touching something. Originally the computer was mounted on top of the base unit but it was moved to above the shoulder plate because I got fed up of crawling on my knees during software development. All the body is made from WOOD. Wood is an insulator, you can glue it, screw it, nail it (not advised), paint it, and saw it and drill holes in it and otherwise shape it without worrying about the dust shorting out the electric's.

The controlling computer is a Triangle Digital Services 2020 16 bit ANSI Forth computer which communicates with the base hardware via an I2C bus, the motors are pwm controlled and each drive wheel is fitted with an encoder disk for feedback.

At the moment Liberator is quite happy wandering aimlessly round the lab but really needs someone who will spend some time on improvements. Please contact The Shadow Robot Company if you would like to know more or get involved.

Vision Robotics

The hardest and single most important aspect of vision robotics is getting a robot to recognise an object. Most research conducted in this area revolves around creating methodologies and systems to allow a robot to properly identify objects, there are of course numerous ways of doing this, but getting them to work optimally is very hard. In fact some of the most testing examples of Artificial Intelligence have been developed for intelligent vision systems. No doubt most cutting edge research into Artificial Intelligence, such as 'Neural Network Computing,' will still remain within the realm of Vision Systems for some time.

However progress has been made and one methodology, 'Segmentation,' although simpler than some advanced Artificial Intelligence Systems, proved to be an effective starting point for engineers at Shadow. Peter Holman, a Shadow Member, has worked extensively on vision systems and set about working on a Segmentation system for Liberator. Segmentation as a method means breaking down the picture of an object into discrete parts. These parts are effectively parameters or segments by which the most significant of these can be used to identify an object. Therefore an object is defined by the Robot in recognising certain parameters. However the Robot must gain knowledge of object parameters in order to compare the object it is seeing with the one stored in its database in order to make a positive identification. The Robot is fed information about numerous parameters - segments - of an object which it then stores in its database. The Robot becomes 'aware' of an object when it is presented it in ideal conditions. One of these 'Significant Segments,' could be an object's hue or surface area.

© David Buckley, Peter Holman & Rufus Wood 1999

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