NXT Ultrasonic Sensor

Now, I am working on implanting obstacle avoidance in my algorithm. I decided to use NXT ultrasonic sensor because it’s the best we have. I did some testing on the sensor myself and looked up the features that come with it.

The Ultrasonic Sensor enables the robot to see and detect objects. It can sense and measure distance, and detect movement. The Ultrasonic Sensor measures distance in centimeters and in inches. It is able to measure distances from 0 to 255 centimeters (98 in) with a precision of +/- 3 cm.

The Ultrasonic Sensor uses the same scientific principle as bats: it measures distance by calculating the time it takes for a sound wave to hit an object and return – just like an echo. Note that two or more Ultrasonic Sensors operating in the same room may interrupt each other’s readings. Distances smaller than 3 cm cannot be measured using the ultrasonic sensor.

The ultrasonic sensor should always be placed in horizontal position; other positions decrease as well the field of vision as the sighting distance of the sensor. The sensor seems to be a bit 'blind' on the left eye, which can be explained by the fact that the left eye is actually the receiver of the ultrasonic wave while the right eye is the sender.

Testing showed two weaknesses of the ultrasonic sensor. The first issue is that it showed some areas where the sensor tends to measure 255 cm instead of the actual distance. The second even more important issue is the critical area in between 25 cm and 50 cm where the sensor has a high probability of returning the wrong value of 48 cm, but this one doesn’t happen that often.

Time: 5hrs.