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Tue, 18 Mar 2008
robotic blimp (YARB 1.0) update - sensors added
The blimp now have some additional sensors - a pair of Maxbotics EZ0 ultrasonic ranging modules and a Honeywell HMC6532 I2C compass. Also, the camera module now points downward about 30-degrees via a simple extender. The camera angle is pretty good now - the wide angle lens has a field-of-view of approx 120-degrees, so the bottom of the frame captures the scenary almost directly below.
At the moment, the sensor data is unfiltered, which allows us to get an idea of how much variation there might be. The ultrasonic data is pretty solid - the forward looking readings bounce around a bit, but the download readings are fairly consistent. However, I think we will change to a narrower beam module - probably the EZ1. Also, it would be nice to have a couple of side-looking modules to enable some degree of mapping capability.
The compass is less consistent, and it turns out that we're getting magnetic field interference from the motors when they are running. At the time I recorded the video clip below, I wasn't paying attention to the readings, but subsequent tests show that the readings are varying by as much as 15-degrees when the motors are powered. Either we will have to move the compass, or add some compensation in software.
Here's a snapshot of the gondola with the additional sensors -
The plan is to make changes in the sensors to clean up the data, and then to write a script using the onboard C interpreter to let the blimp wander around on its own, perhaps following a course based on heading. After that, we will add some logic to use the camera to lock onto an object and follow it around while maintaining altitude and avoiding collision - that will be a bit more challenging.
Here's some video captured from yesterday's test session. The caption overlay shows heading, forward distance and height above ground in inches.
Posted Tue, 18 Mar 2008 14:25 | HTML Link | see additional stories ...