Depth Perception

Starting up:
Participants: Johan & Jakob
Date: 9/9-2010
Duration: 2 Hours
Goal: Attach the UltraSonic sensor to the Failbot 9797, then test the UltraSonic sensor with regard to the exercise problems.


Bodily Enhancement
The sensor rig was assembled with care and without problems much larger than not being able to easily locate the required blocks. The Failbot was provided with the program SonicSensorTest.java and placed at different distances.
We noticed a peculiar behaviour with regards to the measurements reported by the UltraSonic Sensor.
First of all, even though both object and rig remained stationary the measurements did not remain a stable value.
This might be attributed to the fact that the sensor reports the distance in centimeters and the distance might be close to the threshold between the values being reported. 


Snappy Response
For the current exercise the sample rate for the UltraSonic sensor is increased to test whether the fact that a 300 ms minimum delay between samplings has been removed from the current release of LeJos.
We lowered the sample interval gradually, but did not notice any dramatic increase in the performance of the sensor. 


Softcore Issues
The sensor performed very differently depending on which material we tried to bounce the ultrasonic signal off.
Clothes and other materials with sound absorbing properties gave the sensor very hard times.
Also the angle between the sensor and the objects surface ( e.g the surface of a wall ) exerted heavy influence on the results as the echoes did not return to the sensor. The sensors error also seemed very high 5-10 centimeters, which leads to the sensor being very demanding to use.


Tractor Beam ... Eh. Tracker Beam
The Failbot was gifted with the program Tracker.java and tried when running to keep a certain distance to any object in front. When no object was detected it sped full speed forward. This had the unintended effect of having it run into objects being introduced so close in front of it that the sensor reports the maximum distance.




Conclusions
The days conclusions are mostly centered around the unreliability of the ultrasonic sensor.
So far we have seen no pattern in the error of the sensor, and this could be examined further.