"This technique has actually been used to reduce noise. It's called "skewed redundant" or some variation. The redundant sensors are placed on different axis that are skewed from the primary axis and everything is mathematically…"
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kalman filter, is this correct?
Started this discussion. Last reply by Tom Yochum Nov 10, 2009. 5 Replies 0 Likes
I was reading Dan Simon article about kalman filters http://www.embedded.com/story/OEG20010529S0118?pgno=1 and I decided to give it…Continue
How about using 4 gyros to reduce the noise?
Started this discussion. Last reply by Brian Wolfe Jul 13, 2010. 16 Replies 0 Likes
I could averaging the values I measure and that would get rid of most of the noise, no need for a kalman filter! I would still have the thermal noise but I am assuming here it would be rather small.
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bGatti replied to xchip's discussion How about using 4 gyros to reduce the noise?"One source of error is vibration - if you want to average multiple gyros - better to use different makes with different operating frequencies - otherwise, they could all react the same way to a harmonic."
Jason Dorie replied to xchip's discussion How about using 4 gyros to reduce the noise?"The drift that a Kalman (or other kind of complementary filter) eliminates isn't just from noise.
Try sitting in the passenger seat of a car, reading the speedometer once per second, and using that information to work out the number of inches…"
Tom Yochum replied to xchip's discussion kalman filter, is this correct?"Here is the code I am talking about:
% Simulate the linear system.
ProcessNoise = accelnoise * [(dt^2/2)*randn; dt*randn];
x = a * x + b * u + ProcessNoise;
% Simulate the noisy measurement
MeasNoise = measnoise * randn;
y = c * x +…"
xchip replied to xchip's discussion kalman filter, is this correct?"well, I want to simulate an object that stays still, the readings form the accel are stilly noisy, and that is why accelnoise has to be >0 otherwise I have a ideal filter and I wouldn't need kalman :-)"
Tom Yochum replied to xchip's discussion kalman filter, is this correct?"Did you set accelnoise to zero in the example code? If not, then there is noise added to your "true" value. Therefore, the true system is randomly walking and your Kalman is tracking it. I would say your code works great!
Tom"
xchip replied to xchip's discussion kalman filter, is this correct?"Tom,
I am adding noise to the accel sensor, without kalman filter it should be a random walk but with it I would expect the system to stay still since the accel reports zero all the time ( u = 0 )
The "true" value should be the rect…"
Tom Yochum replied to xchip's discussion kalman filter, is this correct?"Are you adding any noise to the process? If so, then you are looking at a random walk.
Also, is there a "true" value in the plot above? It looks like there is a "true" value in green and the red estimate follows it quite nicely.…"
noel hughes replied to xchip's discussion How about using 4 gyros to reduce the noise?"One way of eliminating erroneous accelerometer measurements is to throw out any measurements that deviate from one "g" (9.81 m/s^2, 32.2 ft/s^2) by some margin and requiring that measurements be within that range for a given period of…"
xchip posted a discussionkalman filter, is this correct?
I was reading Dan Simon article about kalman filters http://www.embedded.com/story/OEG20010529S0118?pgno=1 and I decided to give it a go in scilab.I made the following changes in the code:reduced mesnoise from 10 to 0.1 (that makes my measurement sensor more accurate)Set u=0, that is no external accelerationsAnd the results I got are quite dissapointing :-)According to the chart above in 60 seconds my sensor + kalman filter…See More
ModeratorChris Anderson replied to xchip's discussion How about using 4 gyros to reduce the noise?
"Uh, no. Keep studying. You'll get it..."
ModeratorKen replied to xchip's discussion How about using 4 gyros to reduce the noise?
"Except that we aren't using a Kalman filter. We use DCM. Less CPU effort, does everything we need it to do (so far). And quite well, even."
xchip replied to xchip's discussion How about using 4 gyros to reduce the noise?"Ok so, lets say I want to use the IMU in my car, when I accelerate or break suddenly the KF should then filter those short accelerations since it thinks it's just noise... amazing!"
xchip replied to xchip's discussion How about using 4 gyros to reduce the noise?"Chris,
Thanks for the pointers to Wikipedia, I already spent some time there plus I read a few other papers, I thought that could have been inferred from the questions I was asking :-)
As for the KF, as in any filter, I thought it's main…"
ModeratorChris Anderson replied to xchip's discussion How about using 4 gyros to reduce the noise?
"We do! Gyros are wrong in the long term (drift), while accelerometers are the wrong in the short term (inertial forces). They correct each other. See this post for more.
The hardest test for an IMU is not getting confused in a constant turn. The…"
xchip replied to xchip's discussion How about using 4 gyros to reduce the noise?"I see, something I ws expecting to see is to use the the gyro to correct the accel measurements, for example to remove the centrifugal force when the aircraft is turning, any idea why don't we do that?"
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