Hot answers tagged

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 ...
user avatar
  • 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 ...
user avatar
  • 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 ...
user avatar
  • 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 ...
user avatar
  • 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 ...
user avatar
  • 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 ...
user avatar
  • 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 ...
user avatar
  • 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 ...
user avatar
  • 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{\...
user avatar
  • 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, ...
user avatar
  • 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 ...
user avatar
  • 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 ...
user avatar
  • 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 ...
user avatar
  • 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 ...
user avatar
  • 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.
user avatar
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 ...
user avatar
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 ...
user avatar
  • 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 ...
user avatar
  • 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}...
user avatar
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 ...
user avatar
  • 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 ...
user avatar
  • 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 ...
user avatar
  • 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. ...
user avatar
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 ...
user avatar
  • 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 \...
user avatar
  • 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 ...
user avatar
  • 420

Only top scored, non community-wiki answers of a minimum length are eligible