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Rotation Reliability
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Author:  billyb29 [ Mon Dec 15, 2014 3:40 pm ]
Post subject:  Rotation Reliability

This question is for anyone who's been working for a fine amount of time with the lego mindstorms. Are they reliable enough to be in a honors project (graduation project). Been playing around with it for the last couple of weeks, but I could really use some advice. Are the sensors (compass and ultra sonic) accurate enough to be included in such projects. Thanks for any help.

Author:  BurningLights [ Mon Dec 15, 2014 4:19 pm ]
Post subject:  Re: Rotation Reliability

It entirely depends on the project and what you're trying to do. Do you know exactly what your project is on? I'm afraid we can't tell you whether an NXT will be reliable enough or not unless we know your specific application of it.

Author:  billyb29 [ Tue Dec 16, 2014 2:06 am ]
Post subject:  Re: Rotation Reliability

It is exploring a closed environment using the compass and ultrasonic sensors. It should detect objects and return information about their coordinates and calculate the area of the environment (from its bounds) I hope this helps because that's what I have in my mind so far.

Author:  MHTS [ Tue Dec 16, 2014 6:08 am ]
Post subject:  Re: Rotation Reliability

All sensors have their quirks and limitations. The accuracy of the sensors depends on how your program interprets the data. For example, accelerometers can be sensitive and picks up a lot of noise if it is mounted on a robot that's in motion. An ultrasonic sensor can receive erroneous data if the sound wave bounces off different type of surfaces at different orientations. At times, you may need to apply low-pass filters to get rid of high frequency noise. Sometimes you may even need to apply heuristics to detect and discard erroneous data points. For example, in our FTC competition, we've seen encoders sometimes return bogus count when a static discharge occurred. This will cause our autonomous to go crazy (e.g. suddenly go in reverse). After numerous hours analyzing the logged data, we found the encoders return bogus data. So we changed our code to use a heuristic such that if a data point is way off its expected value, we will discard the data.
Regarding your question on rotation reliability. If I understand you correctly, compass sensor in general is not very reliable just because it can be interfered easier depending on where you mount the sensor. For example, if it is mounted close to a motor or surrounded by metal beams. The compass can be affected by the surrounding environment (e.g. inside a concrete building, with some big appliances running close by etc.) So you need to use your own judgment whether you can deal with the limitation of that sensor and may need to use other type of sensors.

Author:  billyb29 [ Sat Jan 03, 2015 2:42 pm ]
Post subject:  Re: Rotation Reliability

Well you got me worried because my robot is a 3 wheeled vehicle and both sensors (ultrasonic and compass) will be mounted on the car not far from the motors. You think that's gonna be a problem?

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