Robot 3 (Dreirad)

another robot for outdoor operation...

Robot 3

Dreirad_l.jpg Mittlerweile ist die Allrad-Skateboard-Variante wieder verworfen worden, wegen zu hohem mechanischen Aufwand.

Aktuelles Konzept: ein Dreirad-Roboter für Indoor, und auch mal gelegentlich Outdoor.
Ein über eine Ubersetzung (Fahrrad-Zahnräder und Kette) angetriebenes vorderes, lenkbares Rad, mit 2 passiven Hinterrädern, welche die jeweilige gefahrene Strecke messen.
Motor: Scheibenwischermotor. Zur Lenkung: Wird wohl auch mit einem solchen Motor realisiert werden. Als Rechner wird ein Mikrocontroller namens Atmel AT90S8535 zum Einsatz kommen.

Januar 2002

Dreirad_vr.jpg Another variation on the mechanics. Most of the electronics again recycled from previous robots. One large battery and one smaller one in series (25 Ah and 7 Ah); the big one for the main supply, the second to get the needed 24 Volts for some circuits, those i didn't want to modify (important modifications would have been necessary).

Concept: One wheel in front of the robot, this one is orientable (car wiper motor with bicycle chain) to run a curve, only this one is driven by a wheel chair motor (bicycle chain too) running just at the half of its nominal voltage (it's still strong enough!). The two rear wheels are running free and are both equipped with a perforated disk and photocouplers to measure the way the robot is running.


The processor is a new concept: Atmel AVR AT90S8535 with 8255 port expansion. the AVR has 8 analog input ports. A very interesting chip for building robots because of its FLASH-memory, EEPROM and in-circuit-programming. Two infrared pulsed diodes and one IR-receiver on the front side, Ultrasonic on the rear, 2 x 2 bumper microswitches on each corner, two more switches to detect the end of range of the direction motor. LCD-Display and some LEDs to indicate its actual status and for observing some parameters. Programming via a four-wire-printer cable from a pentium laptop using BASCOM AVR. Dreirad_tower_th.jpg
This robots is rolling much faster than previous models, but another problem appears: the wheel chair motor is driving the front wheel via a bicycle chain with not too well-centered wheels; the chain is often jumping off the wheel. After that i decided to use standard motor belts like in automobile motors.

Next step is to set a "tower" with detectors on the top of the robot, a small platform with more analogues sensors on it, the platform makes a scanning movement from left to right and back, it scans about 300 degrees of a circle. The sensors to be mounted are two microphones, two LDRs an infrared receiver and two high brightness white LEDs to light the robot's path and environment.

The platform is driven by a DC motor with a gearbox, a potentiometer and two switches detect the ends of scanning range to inverse the scan direction, and to get the precise position (angle) of the scanning sensors. This should allow the processor to calculate the way to the detected signal source and drive in that direction.





Lochscheiben mit Gabel-Lichtschranken an den beiden passiven Hinterrädern (24 Pulse / Umdr.).

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last update: June 4th 2004

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