New IMU offered by Sparkfun here. I think this board has some great potential that could lead to some all singing, all dancing Arduino-native IMU.The fact that this IMU is built around the ATMege 168 makes me think that it could be re-flashed to become some sort of "ArduIMU" board, and even run a ported version of the "Premerlani-Bizard robust direction cosine matrix estimator / MatrixNav firmware" as per this suggestion.Perhaps this board could be partnered with the ArduPilot, the IMU doing its thing, and the ArduPilot providing GPS info and servo driving?Anyone got any opinions for or against this? Or even better, technical reasons why this a) won't work, or b) is an awesome idea! :DSimon
Giles, I was thinking those off axis boards could be lowered considerably (think long skinny boards).
Are dual axis gyros complementary planes to the flat gyro used here?
(Also that board is a standard product, so they had some engineering benefit to simply add pins.)
I saw at a Underwater vehicle conference in Southampton the most well put together IMU I have seen, it was made by XSENS, a Neatherland's (I think) company and one of them had integrated GPS to make sure that If you were turning the accelerometer drift thing didn't recalibrate wrongly (not very well explained). It gave very true 3D data and through a serial port. It was tiny as well. Shame about the price (didn't get that off him clearly but it was in the thousands). 16 bit ADC reading from 3 x gyro, 3 axis accel, 3 axis Mag, 4Hz GPS (w/ galileo compat). Very intergrated package.
Someone needs to sell an IMU with just gyros & nothing else for $50. How many robots does Nate think don't already have a microcontroller capable of sampling an IMU? Who would even buy it if they didn't already have their own programmer for such a microcontroller?
Modern gyros can go without corrections for over 10 minutes. Amazing that no-one has ever published a graph comparing the drift of different gyros.
What if the signal is 0.3 instead of 0.5? In that case you're hosed, the 0.1 amplitude noise will never cause it to exceed 0.5 and be quantized as 1, so you end up with signal = 0.0 no matter how fast you sample. But intentionally increasing the noise's amplitude (dithering) can reduce the sampling error in this case! With >0.2 peak amplitude noise, a small number of the 1 bit ADC's samples will be 1, and the long term average will be closer to 0.3.
I wrote this before seeing Bill's solid explanation (the page index buttons are burried below the reply box). Might as well post it.
Oversampling Example: A signal is at 0.5, mixed with evenly distributed noise of 0 mean and 0.1 peak amplitude. In a single measurement, a 1 bit ADC will report a 0 or 1, producing 0.5 error in both cases. If you sample multiple times while the signal remains (more or less) constant, half the samples will be 1, and half will be 0. Averaging the multiple samples using 2+ bit math shows that the signal is 0.5 (with zero error in the limit of infinite samples). So, a 1 bit ADC can resolve >1 bit by letting noise cancel itself out over time. Many factors degrade it in the real world, but the basic concept works.
Comments
Are dual axis gyros complementary planes to the flat gyro used here?
(Also that board is a standard product, so they had some engineering benefit to simply add pins.)
Modern gyros can go without corrections for over 10 minutes. Amazing that no-one has ever published a graph comparing the drift of different gyros.
Oversampling Example: A signal is at 0.5, mixed with evenly distributed noise of 0 mean and 0.1 peak amplitude. In a single measurement, a 1 bit ADC will report a 0 or 1, producing 0.5 error in both cases. If you sample multiple times while the signal remains (more or less) constant, half the samples will be 1, and half will be 0. Averaging the multiple samples using 2+ bit math shows that the signal is 0.5 (with zero error in the limit of infinite samples). So, a 1 bit ADC can resolve >1 bit by letting noise cancel itself out over time. Many factors degrade it in the real world, but the basic concept works.
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