Line follower : Concepts for the realization

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RP6 robotThe robot, based on the RP6, should first be able to follow a line. The line is the target command and also the interaction interface between human (or human instruction) and the robot. The line is a graphical instruction to the robot. The line will have no branches in the first step and therefore do not involve a decision function.

Type of the line
There are many possible implementation options are available. For example, such a single-line rail track set, which can be determined locally with pushbuttons and thus directs the robot itself through this guide rail.

The simplest version of the line however should be a black line which is painted with a standard pencil on a light background.

Hardware for the realization
There are two concepts :
Simple sensor which depends on the single light voltage / current or the electrical resistance change. Three simple sensors : the component represent different tendencies to reaction time and speed in competition and qualified for use on-line detection.

  • Photodiode – A semiconductor which converts light into an electric current
  • Phototransistor – Similar to the photodiode, but more sensitive (in principle, a photodiode with amplifier)
  • Photoresistor – change electrical resistance or conductance sensitivity depends on the intensity of the light. Conductance increases with increasing light intensity.

Compact camera
The camera provides a lot of pixels to give a full picture. Thereby, the complex line (graphic instructions) can be recognized. With the camera, we use digital image processing with embedded systems.

Comparison of these two concept :

Sensors Camera
Costs
rather low
rather high
Amount of information
low to moderate
high
Programming
low
high
Rate of reaction
sensor-dependent
camera-dependent

Implementation of the first concept :
RP6 already have an infrared sensor and also has photoresistors, which is not directed to the ground. There are several approaches, to illuminate the ground with the other LED and directing the reflection from ground with a mirror to the photo resistor. The separate resistances can thus determine brightness differences on the ground.

RP6 IR receiver

RP6 LDRASURO Robot Kit has integrated concept of a photo transistor. At the bottom there are two phototransistors ASURO (SFH 300) and the middle of the red LED is illuminated.

ASURO robot kit sendorThe structure of the ASURO can be easily applied to RFP6, by a small board (or a plug-in connection) with a LED and two phototransistors in front of the bottom Rp6. LED is then connected to the I / O port, phototransistors connected to each port ADC (analog-digital converter) of ATmega32 controller.

Implementation of the proposal for a second concept:
The detection of lines with the help of pixel digital camera is much more complex, but they also offer far greater opportunities for orientation. If there is less accuracy results do not directly blame the camera (of course it also plays a role), but theprogramming software in image recognition.

Robot cameraThe program needs in this project is within the context of image processing, not in the foreground, so that a small camera is sufficient.

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