Motors And Position Encoders; Sonar; Sonar Sensitivity - Omron AmigoBot User Manual

The audio amplifier and sound decoder are part of the AmigoBot microcontroller, which sends
approximately 1 watt of sound through the small speaker on the top towards the rear of the
robot, across from the control buttons and LED's.
Adjust AmigoBot's speaker volume with the Audio Volume control. Insert a flat-bladed
screwdriver tip through the access hole on the Console and turn the control to the desired
volume.
M o t o r s a n d P o s i t i o n E n c o d e r s
AmigoBot's drive system uses two high-speed, high-torque, reversible-DC motors. Each includes
a high-resolution optical quadrature shaft encoder that provides 9,550 ticks per wheel revolution
(approximately 30 ticks per millimeter) that the AmigoBot controller uses to sense and to control
distance, direction, and speed.
AmigoBot's tires are 4 inches in diameter and made of soft, but firm rubber for good traction
and low compressibility. Keep them clean and oil- and grease-free to maximize traction for
climbing up and down ramps and over sills, and to minimize slippage on smooth surfaces.
(Slippage degrades your robot's ability to know where it is.)

Sonar

The AmigoBot comes standard with a
single array of eight sonar. The sonar
positions are fixed: one on each side, four
facing forward, and two at the rear,
together providing 360 degrees of
sensing.
The sonar firing rate is 25 Hz (40
milliseconds per sonar) and sensitivity
ranges from 10cm (6 inches) to more
than 3 meters (10 feet). Objects that are
10 cm and closer register as 10 cm away.

Sonar Sensitivity

Although calibrated at the factory, sonar
sensitivity and range may be adjusted to
Figure 10: AmigoBot's sonar front and rear
accommodate differing AmigoBot
operating environments. The sonar gain
control is a one-turn screw cap accessible through a small hole on the top and near the front of
AmigoBot. You may have to remove an accessory to uncover the hole.
Using a small flat-bladed screwdriver, turn the adjustment screw counter-clockwise to make
the sonar less sensitive to external noise and false echoes. Low sonar-gain settings reduce the
robot's ability to see small objects; under some circumstances, however, that may be desirable.
For instance, attenuate the sonar if you are operating in a noisy environment or on an uneven
or highly reflective floorheavy shag carpet, for example. If the sonar are too sensitive, they will
mistake the carpet immediately ahead of the robot for an obstacle.
Increase the sensitivity of the sonar array by turning the gain-adjustment screw clockwise,
making the sonar more likely to see small objects or objects at a greater distance. For instance,
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