Seeker by Harm Andries Kingma

The goal of Seeker is to look around for human beings, drive towards the first it sees and then try
to follow that person. Seeker locates humans by using a Passive Infrared (PIR) sensor. This sensor
is capable of detecting the heat signature of a human being. It is mounted inside the white cone on
the sensor unit at the front of the robot. The white cone holds a freshnell lens to focus the
infrared (heat) radiation on the sensor element. The sensor unit also holds tree SHARP GP2D02
infrared distance measurement units. These sensors take over when Seeker gets close to the person it
wants to follow. This cannot be done with the PIR sensor because it is not accurate and directional
enough at close range. The sensors of Seeker are mounted on a pan/tilt unit. This enables Seeker to
look around and point its sensors at any object of interest in its field of view. 

The drive train of Seeker is the same as that of Roamer and Wallie. It consists of two propelled
front wheels and a castor wheel at the back, enabling the bot to navigate the world by using
differential steering. 

The brain of seeker is an ATMEL AVR 90S8535 microcontroller. It is programmed in C using the AVR
port of the linux GCC C-compiler. 

The procedure to locate and follow humans is as follows: At powerup, Seeker starts to turn on the
spot. When it detects a heat signature, it drives towards it. When the heat signature is lost during
the approach of the target, it starts turning in a circle again to relocate the heat signature. When
Seeker gets close enough to the target, the infrared distance measurement sensors take over. In
order to follow the target, the distance measured by the left sensor is compared to that of the
right sensor (the third sensor is not used right now). If the left sensor measures a greater
distance than the right sensor, it concludes the target is located on its right side. If its the
other way around, it assumes the target is on the left. It will then move its sensor head in the
direction of the target. The motor controller of Seeker is programmed to drive in the direction the
sensor head is looking, and therefore the whole robot will start following the target. If seeker
gets close to the target he will stop. If the person being followed starts to move towards Seeker he
will start to drive backwards to avoid being stepped on. If Seeker loses the target he will start
looking for a new heat signature. 

On my website: you can also find a 2 movies of seeker in action,
together with a description of my other three bots.


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