Calculo Odometria


Posted on Feb 6, 2014

This article describes how to implement a simple, but robust, optical wheel encoder system on a robot that uses hobby servos for two-wheel differential drive. In my case I am using the TJ-PROTM robot platform from MekatronixTM, and some aspects of this article are specific to that platform. However, it should be easy to adapt the hardware and soft


Calculo Odometria
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ware for virtually any robot with an HC11 controller board. This article details the hardware you will need (and where you can buy it), construction methods, and software techniques for implementing navigation by dead reckoning. The software examples are written in Newton Labs` Interactive C ("IC") version 3. 2. To make use of the code samples, I am assuming you know how to load C and binary modules in IC, and that you know how to use the start_process() function. Rather than being heavy in theory, this is written more as a "how to" article. If you are interested in the theory, I would refer you to the Rossum Project article in the Links section at the end. At the heart of this design is a pair of Hamamatsu P5587 photoreflectors (figure 1), one mounted on each side of the robot behind the wheels. Each wheel has a cardboard disc fixed to it with 48 alternating black and white segments. The tiny 5-legged Hamamatsu photoreflector package contains an infrared ("IR") LED and a matching IR phototransistor, both mounted on the top of the device in such a way that the phototransistor will detect reflected IR light emitted from the LED when a bright surface (such as white card) is positioned within a few millimeters of the device. As the wheel turns, and the photoreflector "sees" the white segments between the black segments, the phototransistor outputs a digital pulse train. By counting the pulses, and knowing the number of...




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