A Robotic Exhibit
By the Smart Devices Laboratory

 

Contact           f.maire@qut.edu.au

Web                http://www.fit.qut.edu.au/~maire

 

A demo user manual can be found at the end of this document.

Objectives of the exhibit

Illustrate behaviour robotics, by showing that a combination of elementary behaviours is all you need to get a robot perform autonomously simple tasks.  Domestic chores like mowing the lawn or vacuuming the house do not require a higher level of intelligence than the intelligence of a cockroach.

 

 

 

 

 

The star of the show is a little robot called “Kheperoo”

 

Side	Front

 

 

What is Kheperoo supposed to do?

Kheperoo is an autonomous robot that has been programmed to dribble the ball alternatively from one goal (barcode landmark) to the other.

How does it do that?

To achieve its mission, Kheperoo tries first to position itself near the centre of the playing field.  Kheperoo does this by comparing the apparent widths of the goals and their relative angles with respect to itself.  As Kheperoo is short-sighted (blurred vision for objects farther than 40cm), it can get lost (and it does get lost!).  to make things worse, Kheperoo’s field of vision is narrow (a cone of 36 degrees).

 

When Kheperoo is confused, it wanders around the field for a few seconds in the hope that it will ends up in a better position.

 

To better appreciate the difficulty of the situation, image yourself having to go to the centre of a rugby playing field covered with a fog thick enough to prevent you from seeing a goal from the other goal (at the other end of the playing field).

 

Once approximately at the centre of the playing field, Kheperoo looks for the ball, goes to the ball, then dribbles the ball towards the farthest goal.  When the robot realises that it is pushing the ball against the target goal, the whole cycle (go to the centre, look for the ball, dribble the ball) starts again.

How does Kheperoo sense its environment?

Kheperoo is equipped with a number of sensors;

• A ring of eight infra red proximity sensors that can detect obstacles (but only at very short range; within 2 or 3cm).  Imagine being able to feel the proximity of objects only by the heat they radiate.
• A linear camera whose image is an array of 64 x 1 grey level pixels.  Imagine looking through a horizontal slit filled with a string of 64 semi-transparent beads.  The linear camera detects only brightness levels (from black to white), but does not differentiate colours (white and yellow look the same through this camera).  In other words, if Kheperoo was human, it would probably be considered legally blind!
• Wheel encoders that monitor the rotation of the motors of the two wheels.

Design issues

It was required that the robot be completely autonomous.  This is achieved by using a combination of elementary reactive behaviours.  Kheperoo switches successively between a number of behaviours (small programs) in a endless loop;

 

Loop for ever

            Go to centre

            Look for the ball

            Go to the ball

            Dribble the ball to the opposite goal

 

The go to centre  behaviour is based on the fact that when near the centre, the goals are diametrically opposite and look about the same width.

 

The look for the ball behaviour uses a get panoramic view behaviour (which explains why the robot is spending a lot of time spinning).  Recall that Kheperoo sees only an horizontal cone of 36 degrees (must make 10 rotations of 36 degrees to get a panoramic view).

 

The dribble the ball behaviour relies mainly on the proximity sensors.  Note the way the robot circles the ball to position itself before pushing the ball.  Note also the way the robot correct the trajectory of the ball.

 

To detect that it is pushing the ball against the wall, Kheperoo compares the actual speed of its wheels to the desired speed.  If the actual speed is less than the desired speed, it means that something is opposing the forward motion of the robot (must be the wall!).

What are the applications of autonomous robot research?

Although autonomous robots are a lot of fun to experiment with, engineers are designing robots whose duties include serious tasks like cleaning, mining and de-mining, garbage sorting, people rescuing, surveillance, planetary exploration, and personal assistance to the disabled or the aged.

 

Like any technology, robotics is neither bad nor good.  It is our collective responsibility (this means yours too) to keep an eye open, and make sure that robots are only used in ethical ways.

User Manual

 

The robot can be operated by Dilbert’s boss;

 

To start the demo, make sure that the coloured cable is connecting Kheperoo to the little grey box, and the little grey box is connected to the main.

 

To stop the demo, pull the plug from the main.

 

Important notes, the linear camera is very sensitive to the lighting conditions (the exhibit might stop to work properly if moved to another place).  There is a little wedge at the back of the linear camera turret.  Its role is to keep the linear camera slightly tilted so that when the electric cable pulls the robot backwards the ball does not disappear under the camera horizon.

 

Questions can be sent to  f.maire@qut.edu.au