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#16
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Re: Gyroscope saturation?
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#17
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Re: Gyroscope saturation?
yeah..sorry... I should have said that I used to get them for $20 cheaper direct from AnalogDevices. I think I paid $70 for the SparkFun board last year. I also looked at a lot of yaw rate controllers from r/c aircraft catalogs. But they are controllers, not just sensors.
Anyone else take a look at what the r/c world has to offer? ...just curious Eric |
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#18
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Re: Gyroscope saturation?
My team has always been a little bit scared of doing this because of the gyroscope values drifting. Would one of these (300 dps) gyroscopes allow you to track your orientation over a 2 minute period without introducing too much error?
- Toby |
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#19
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Re: Gyroscope saturation?
Team 95 has used gyros for years, and aside from the above caveat that you can pick up errors from collisions, the system has worked very well for us.
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#20
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Re: Gyroscope saturation?
Right On Kaszeta.
The first year we used an AnalogDevices 300deg/sec yaw rate sensor was in 2004. We had a holonomic chassis that year. At first, the chassis was not easy to drive. The wheels were small and on irregular surfaces, they would not all be in contact with the floor. This tended to make the 'bot spin and drift while trying to drive straight. The first thing we did was to use the yaw rate signal to add counter spin to our drive train, when the driver was requesting straight motion without rotation. (...just a simple proportional control...a gain times the sensed yaw rate ) Next, we used a trapazoidal integration to get orientation from yaw rate. That was in our drive code that we wrote to allow the chassis to move in the direction the driver moved the stick, regardless of which way the 'bot was oriented. The kicker here, is that we did all this in the 38hz main loop. ...really slow when I now read that Kevin Watson's talking about sampling rates over 1000hz What we found was that our orientation was off about 1.5deg for each full rotation of the 'bot. We had a reset button on the OI that year. If it got too funky for the driver, he set the 'bot facing straight up-field and reset the orientation. Now, we do see the sensor value drift around the neutral point. So we just put a small deadband around 0 yaw rate - say +/-5 counts and forget about the small loss in sensitivity. The yaw rate sensor is your friend. Get a good zero yaw rate reading while in disabled mode, and for the next 2:15, have some fun! Last edited by EricS-Team180 : 11-01-2008 at 23:19. |
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#21
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Re: Gyroscope saturation?
I remember last year there was some talk about upping sample rated on gyros and accelerometers to somewhere near the rate you say Kevin's talking about. However, I can't find a thread or anything pertaining to fast analog sample rates. I'm glad that I'm not the only one that heard of that, lol. Could you by any chance point me to something concerning that sampling?
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#22
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Re: Gyroscope saturation?
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The reset button sounds like a great idea and something we'll probably implement if we find ourselves using a gyro during the user controlled mode (which is not a given seeing as we are not building a holonomic drive train). We'll probably implement a gyro on our robot this year to help with accurate turning, especially during hybrid. |
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#23
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Re: Gyroscope saturation?
Guy,
ADC conversion noise is your friend. Eugene Quote:
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#24
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Re: Gyroscope saturation?
My friend because it makes such measuring rates unuseful, and therefore helps keep the processor under a lower load than if they were? Or for another reason I'm currently missing?
Has it even bee / is there a good way to quantify ADC conversion noise? So that I might be able to know what's the minimum useful sampling rate? |
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#25
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Re: Gyroscope saturation?
Your friend, if the amplitude is large enough, because it helps you with the quantization error, making the higher sampling rate useful by producing an average. If really old white papers are still laying around on CD, I believe that there is a white paper on the topic.
Eugene Quote:
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#26
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Re: Gyroscope saturation?
How exactly would I adjust the program to get a reading while in disabled mode? I don't want to waste too much of the hybrid period calibrating my gyroscope, but I'm not sure when else I could set it...Also, how would I know when to stop sampling?
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#27
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Re: Gyroscope saturation?
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If you're using the new code, just put the code in disabled(). |
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#28
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Re: Gyroscope saturation?
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#29
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Re: Gyroscope saturation?
ubergeek5075
I read it here: post #94 in Kevin's post about the v3.0+ code Actually, we want to experiment with accelerometers this year, where higher sampling rates will certainly pay off. RyanW, kazeta's right on again. We typically put the Get_analog function call in Default_routines. Then we'll call our gyro function(s). We pretty much "roll our own" functions, but check out Kevin's routines. ...good stuff Eric Last edited by EricS-Team180 : 13-01-2008 at 17:28. |
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#30
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Re: Gyroscope saturation?
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