8
votes
Accepted
What is a good approach for outlier rejection during real time data filtering?
It is both acceptable and standard to use camera observations with a Kalman filter if you are talking about landmark positions in pixel or real-world space. Pixel space observations are usually ...
- 872
4
votes
Accepted
Practicality of using magnetometer inside AUV
Mags are used in almost all UAVs. It will be useful and it will be a unique source of information.
Adding a some shielding between the mag and your computers and power lines will greatly reduced the ...
- 1,825
4
votes
Can I write the seperation principle for LQG controllers in this state space form?
Both state space representations are equivalent. For example the eigenvalues of the two closed-loop system matrices should be the same. However when implementing LQG you only have access to the ...
- 931
4
votes
Accepted
Noisy magnetometer data
First, let's look at if your findings seem reasonable given the datasheet specifications for the sensor.
For this, I'll assume that Wikipedia is generally correct and that the strength of Earth's ...
- 14.7k
3
votes
Accepted
Velocity Model Motion in Matlab (Probabilistic Robotics)
There are several traps you might have stepped into, but it is difficult to tell without more information. The first issues that came to my mind:
The equations you wrote down are for sampling from ...
- 629
3
votes
Accepted
Can I write the seperation principle for LQG controllers in this state space form?
This is really a lot to look at, but the most glaring issue I noticed off the bat is your definition of the control signal $u(t)$.
What is the input to your controller? What should be the input to ...
- 14.7k
3
votes
Accepted
What Does the Sensitivity Function Mean?
The text is saying that system perturbations and measurement noise look identical to the controller. That is, a controller will react in the same fashion to both system perturbations and noise in the ...
- 1,825
2
votes
Accepted
Filtering IMU angle discontinuities
Here are my two suggestions for dealing with this problem:
Use a median filter, which replaces each value of your signal with the median of the values in a small window around each one. Here is some ...
- 1,357
2
votes
Accepted
How to choose the state space model for 1 axis gyroscope to implemnt a good kalman filter
Assuming the angular velocity is constant (i.e. $\dot{\theta}_{k+1} = \dot{\theta}_{k}$) It seems to me the state vector should look like this
$$
\underbrace{
\begin{bmatrix}
\theta_{k+1} \\
\dot{\...
- 2,347
2
votes
Accepted
Wheel odometry simulation using ground truth
You can't just take the ground truth states and get wheel encoder positions, or vice-versa, because the robot is nonholonomic. Nonholonomic is a fancy word that means "path dependent," essentially, ...
- 14.7k
2
votes
EKF singularity problem when measurement noise R is zero
I think you need to step back a bit and think beyond the math. An (E)KF is used to estimate the true value of a signal in the presence of noise; it's only because of this noise that we even need the ...
- 2,679
2
votes
Eliminating drift generated from double integration of acceleration signal using Envelope Method
It looks like you are adding a constant for noise, so it makes sense the envelope output is a constant offset from the clean. I would think you need to add gaussian noise to simulate more realistic ...
- 296
1
vote
What is the noise in this PWM signal?
After a bit more reading and thinking, I think I’ll answer my own question. I’d like feedback on my logic if you have it.
My logic is this:
the PWM signal from the MCU is clean (evidenced by the ...
- 319
1
vote
Accepted
What would be a way to estimate IMU noise covariance matrix?
Usually, IMU manufacturers implement some kind of filter to remove the noise these days, therefore the probability is your IMU is not throwing raw values. Nevertheless, you can initiate the sensor ...
- 516
1
vote
Understanding import attributes of electronics speakers, by example
A small speaker like this one should be able to play tunes as you have mentioned. You can use an arduino or a raspberry-pi to stream audio over as shown in this link.
- 445
1
vote
Practicality of using magnetometer inside AUV
As mentioned in the previous answer, many small, low-cost underwater (and aerial) vehicles use a magnetic compass. You need a good procedure for both hard-iron and soft-iron calibration of your ...
- 96
1
vote
Accepted
Should the kalmanfilter have disturbance as input?
I don't like the format you're using, with $\tilde{x}$, because it masks the fact that it is actually $x-\hat{x}$. In generally, you don't actually care about the state error; what you really should ...
- 14.7k
1
vote
Accepted
Why doesn't this kalmanfilter filter anything? Reduce disturbances and noises with LQG controller
I'm not sure if this answers the question but I think there is a mismatch between the block diagram and the state equations.
In the first block of the state transition matrix (top-left $A-BL$) you ...
- 26
1
vote
Accepted
Why does one IMU axis influence another?
The problem is estimating angles in regions of instability.
Let us look at equations used for estimation of pitch and roll angles. For aerospace rotation sequence e.g. $xyz$:
$\tan(roll)=\frac{G_{y}...
- 287
1
vote
Kalman filter: 3D measurement error to individiual components
Take a bunch of measurements of your system while states are static and compute the noise matrix yourself. As long as recording measurements is relatively straightforward this should be a painless ...
- 1,825
1
vote
Odometry motion model for Kalman filter, but is the error zero mean?
The noise term will always be zero mean. If you believe the odometry equations will not accurately capture wheel slip and you believe the filter will not adequately track your state then the solution ...
- 1,825
1
vote
IMU based acceleration parameters for differential drive robot
Plan A: get IMU chip and read the raw register data. Read data is easy. Using data is hard.
Plan B: use FreeIMU library that does 'data fusion' that combine raw data from multiple sensors and present ...
- 419
1
vote
The uncertainty is big while the sensor is rather accurate at measuring a landmark in EKF-SLAM
You may have covariance collapse. You may have such small covariance in your target estimate that the measurements are having almost no effect on the target's estimate. Try artificially inflating it.
...
- 5,162
1
vote
The uncertainty is big while the sensor is rather accurate at measuring a landmark in EKF-SLAM
Something is wrong with your code. Measurements with Gaussian noise should be within one standard deviation of truth 68% of the time. Somehow, your measurements seem to be correlated with the accuracy ...
- 1,825
1
vote
The uncertainty is big while the sensor is rather accurate at measuring a landmark in EKF-SLAM
You don't describe your setup in detail, and some of the units are missing, but my guess is that the $\sigma_\phi$ is mainly responsible for the initial error you are seeing.
$\sin( 0.5 ) \times 30 \...
- 2,954
1
vote
Accepted
Eliminating Electrical Noise from my motor driver
First off, you should probably replace all electrical connections between the motor driver and other circuitry with optocouplers (I hope you aren't using the analog interface). Then, make sure that ...
- 420
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