Questions tagged [ekf]
the extended Kalman filter, a filter for nonlinear state estimation.
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EKF Slam algorithm doubt at observation update
I have some doubt on EKF Slam with known correspondence in the measurement update state. I follow the algorithm from Probabilistic Robotics by Sebastian THRUN. This Algorithm is on Chapter 10 page No:...
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1answer
31 views
provide world map for ekf global localization problem
I am trying to implement the ekf_localization algorithm in page 217 (Table 7.3) of the probabilistic robotics book by Thrun.
From my previous post, I understand that I need to extract observed ...
2
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1answer
53 views
EKF localization data association
I am working with ROS indigo and clearpath huskyA200 and wanted to implement the EKF localization with unknown correspondences with my own hokuyo lidar data for a school project. Giving the algorithm ...
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2answers
63 views
GraphSLAM equation doubt
I have question about GraphSLAM implementation.
To find out the path and map using GraphSLAM we rely on this equation:
$$\mu=\Omega^{-1}\xi$$
where $\Omega$ is our information matrix which ...
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2answers
31 views
How to detect loop in robot movement observing odometer data
I have some odometer data. This data are based upon robot movement. I can transfer those raw data to a motion equation from where I get x,y,and theta co-ordinate of a Robot. If I plot those x,y ...
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2answers
73 views
How exactly does sensor fusion work in Kalman filters?
I've been looking into implementations of Extended Kalman filters over the past few days and I'm struggling with the concept of "sensor fusion".
Take the fusion of a GPS/IMU combination for example, ...
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1answer
32 views
How to avoid matrix singularity in GraphSLAM
I am trying to implement GraphSLAM from Sebastian Thrun's paper, The GraphSLAM Algorithm with Applications to Large-Scale Mapping of Urban Structures.
When I compute the inverse of my information ...
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1answer
68 views
Why adding odometry data as control vectors to EKF-Monoslam algorithm fails?
I am working on EKF-MonoSlam (Davson) method for the mere input as a webcam, (it works "fine" if we calibrate and use reasonable sigmas) , and I am trying to add the odometry of some dataset (as ...
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API/ Library for re-orienting 360 degree camera frame efficiently
I have a camera that produces a 360 degree image output. This camera has an IMU unit integrated with it. I have written a C++ Extended Kalman Filter algorithm to estimate roll, pitch and yaw of the ...
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1answer
65 views
Confusion of EKF equations
I read Probabilistic Robotics by Sebastian THRUN (online version). I also read http://ais.informatik.uni-freiburg.de/teaching/ws12/mapping/pdf/slam04-ekf-slam.pdf
Question1 :
What will be the ...
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0answers
24 views
Kalman filter and ekf main difference in elaborate way
I am studying about various filtering techniques for Robot pose esitimation. I came to know two very well known filter technique Kalman Filter and Extended Kalman Filter. To know about this two ...
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EKF based Slam implementation with landmark identification in Global frame
I am working on mobile Robotics. I want to implement Slam. I have a very specific question about EKF Slam. To implement Slam I read the book "Probabilistic Robotics". I read its online version. There ...
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Sigma calculation for EKF based Slam
I am working on EKF based slam. I go through Probabilistic Robotics.
I attachd a picture here. I have doubt about how to calculate Sigma.
I am happy if someone share their views about Sigma. How to ...
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1answer
167 views
EKF implementation on odometry/IMU
I am applying Extended Kalman Filter for a mobile robot with IMU and odometry data. I am running simulation currently. However, I don't have suitable data for odo/IMU measurements to use. Where can I ...
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1answer
59 views
Tracking vehicle 6 states extended kalman filter required?
I'm trying to track an accelerating vehicle using a camera, an IMU, and a GPS.
I use for the state space equation a constant acceleration model:
The states are the position, the velocity, and the ...
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0answers
16 views
OpenEKFMonoSLAM
I'm trying to make OpenEKFMonoSLAM work with different datasets. As far as I can see, it is failing with images bigger than 240x320 in ransac.m
Here's a screenshot of the error.
Does anybody came ...
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0answers
22 views
Updating the covariance matrix with limited amount of corrections
I am doing small experiment with mobile robot wall following and EKF SLAM with only one short range laser. The robot starts to predict its position directly when its founds the first landmark and its ...
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2answers
69 views
Robot heading uncertainty values
I'm tracking the state of a robot using an EKF defined by:
$$(x,y,\theta)$$
where $x$ and $y$ are the coordinates in the ground-plane and $\theta$ the heading angle.
I initialized the covariance ...
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1answer
78 views
How is gyroscope bias exposed and tracked?
For an accelerometer, the measurement is defined in the following way:
$$a_m = R_w^b(a_{w} - g) + b_a + v_a$$
Where $R$ is a rotation matrix, $g$ is gravity, $v_a$ is noise, and $b_a$ is the bias. ...
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16 views
How should I reduce noise in my EKF?
I am estimating orientation of my quadcopter and my EKF is way noisier than the complementary filter I had before.
I am integrating the gyroscope at about 100Hz and I am also integrating my ...
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41 views
How do you update the quaternion from an accelerometer or magnetometer in an Extended Kalman Filter?
I'm trying to implement an Extended Kalman Filter to estimate the attitude of my quadcopter. I am following these two papers: Trawny, Sola
Currently using only 4 states:
$$x = \begin{bmatrix} q_x &...
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1answer
77 views
GPS/ 1GYRO - 2D + ACCEL+GPSEKF
I am trying to integrate GPS and IMU but as a first step I am trying to use just 1d gyro and 2d accelerometer to work. Below is my model -
State model and propagation
So, my question is .. after ...
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50 views
Meaurement function model in kalman filter
I'm tracking the state of a vehicle using kalman filter. The state is represented by 3 random variables: $X=(x,y,\theta)$ where $x$ and $y$ refer to the position in the plan and $\theta$ to the ...
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1answer
151 views
Unscented Kalman Filter VS Extended Kalman Filter on stability
The Extended Kalman filter is more or less a mathematical "hack" that allows you to apply these techniques to mildly nonlinear systems.
The problem with Extended Kalman Filter is if I initialize the ...
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1answer
71 views
Calculated yaw angle is not poper (EKF)
I used EKF to observe the quaternion and extract the roll, pitch and yaw angles. The used sensors are Gyro sensor and acceleration sensor.
The roll and pitch angle looks like proper but the yaw ...
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0answers
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EKF based SLAM, marginalization and key-frames
I have a couple of tightly related questions regarding EKF-based visual SLAM. It is common in the Kalman based VSLAM litterature to marginalize 3d points and past poses. Condsidering the EKF as a ...
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115 views
Kalman filter localisation equations
I am doing mobile robot localisation as a project. Now I stuck in obtaining the equations of EKF localisation. My robot moves straight for 10 seconds parallel to x-axis and robot equipped with 2 ...
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2answers
1k views
Extended Kalman Filter for IMU
I am trying to use a multilayer perceptron to make a flight controller for a ROV. I have a MPU-9250 IMU and I need to remove the noise from the sensor before I can train my MLP. The IMU has a ...
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1answer
98 views
What is the intuitive explanation of using Jacobian of observation model while calculating Kalman gain in EKF SLAM?
The idea of using Kalman gain in EKF SLAM is to figure out how much we trust our motion model and sensor/observation model. As explained in The Extended Kalman Filter: An Interactive Tutorial for Non-...
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1answer
93 views
Why EKF-SLAM uses EKF instead of linear Kalman Filter?
I am writing a bachelor's diploma on vSLAM. I learned and programmed EKF-SLAM like it's written in MonoSLAM paper, and I was going to write, that I can't use KF and have to use EKF because of non-...
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0answers
69 views
Strange EKF localization covariance behavior during prediction only
I've implemented a simple robot simulation based on the equations from EKF localization with known correspondence found in Probabilistic Robotics by Thrun et. al. Everything seems to be working but I ...
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1answer
178 views
How to transform Accelerometer data from the robots frame to the world frame
I'm current workin on an EKF for an carlike robot and I'm not sure how to transform the IMU accelerometer data to offset the roll, pitch and yaw and get the acceleration with respect to the ground.
I'...
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2answers
157 views
Paradox: I can't use accelerometer measurements to obtain information about my states in a quadcopter?
I'm currently developing an EKF to estimate the position and orientation of a quadcopter. My state vector is comprised of 3D position, 3D velocity, 3 euler angles and the angular velocity vector.
...
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1answer
107 views
EKF state propagation model using variables that are not part of state vector
I am trying to understand the EKF theory. Can the state transition function depend on variables that are not part of the state space? For example, the state propagation below depends on the ...
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1answer
731 views
Landmark extraction algorithm
The landmarks are often used in SLAM. What are the algorithms used to extract them, and how can a robot differentiate the landmarks, if they detect one in point A at Xt and another in Xt+1? How can ...
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1answer
139 views
Should I use or not EKF for Baro-Acc altitude estimation?
I've recently implemented a kalman filter to estimate altitude for a small robot with an IMU+Baro sensor mounted on it.
My objective is to get max precision I can have, using this two sensor, with ...
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0answers
85 views
Need help in implementing EKF based SLAM
I just started learning about slam and I have been trying to simulate a robot moving around a set of landmarks for the past 3 days. The landmarks have known correspondences.
My problem is, if I add ...
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1answer
422 views
Calculate the uncertainty of a 6-dof pose for graph-based SLAM
This question is strongly related to my other question over here.
I am estimating 6-DOF poses $x_{i}$ of a trajectory using a graph-based SLAM approach. The estimation is based on 6-DOF ...
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2answers
259 views
Having a hard time understanding this equation in monocular EKF SLAM
Reading this paper on visual odometry, where they have used a bearing vector to parameterize the features. I am having a hard time understanding what the state propagation equation for the bearing ...
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2answers
302 views
Direct vs semi-direct methods for visual inertial odometry
I was reading these papers on visual inertial odometry from IROS 15:
Semi-Direct EKF-based Monocular Visual-Inertial Odometry
Robust Visual Inertial Odometry Using a Direct EKF-Based Approach
I ...
3
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1answer
98 views
EKF SLAM (prediction of new landmarks)
Prediction of new landmarks are commonly expressed as:
Xm = Xr + r*cos(phi + theta_r),
Ym = Yr + r*sin(phi + theta_r)
However this is only true ...
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3answers
1k views
Plotting location using wheel encoder data
Context: I am working with the SFU Mountain Dataset [http://autonomylab.org/sfu-mountain-dataset/]
The UGV image - via the SFU Mountain Dataset website:
I have used the following state update ...
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2answers
333 views
Multi-Rate Sensor Fusion using EKF
Context: I have an IMU(a/g/m) + Wheel Odometry measurement data that I'm trying to fuse in order to localize a 2D (ackermann drive) robot.
The state vector ...
4
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1answer
127 views
Choosing the state vector for an EKF
Could someone help me understand the logic behind choosing a particular state space vector for an EKF?
Context: Say there is a 4 wheeled robot that operates only in 2D. It is equipped with an ...
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1answer
142 views
EKF-SLAM: Shrink covariance matrix on one direction
I have implemented an EKF on a mobile robot (x,y,theta coordinates), but now I've a problem.
When I detect a landmark, I would like to correct my estimate only on a defined direction. As an example, ...
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1answer
158 views
Multiple EKFs or one big
Let's say I would like to use an EKF to track the position of a moving robot. The EKF would not only estimate the position itself but also variables affecting the position estimate, for example IMU ...
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2answers
575 views
EKF-SLAM initialize new landmark in covariance matrix
I am trying to implement an EKF-SLAM using the algorithm for unknown correspondences proposed in the book "Probalistic Robotics" by Sebastian Thrun in Table 10.2 .
By now I understand actually all ...
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1answer
312 views
Need help regarding EKF in MonoSLAM
I am trying to understand the implementation of Extended Kalman Filter for SLAM using a single, agile RGB camera.
The vector describing the camera pose is
$$
\begin{pmatrix}
r^W \\
q^W \\
V^W \\
\...
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1answer
443 views
Estimating angular speed from position for control purpose
I am new to robotics, however I am designing a PID to control the angular velocity (azimuth, elevation) of a couple of Faulhaber motors.
The input to the PID control is the actual angular velocity, ...
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1answer
84 views
EKF over-correcting?
I've been implementing an extended kalman filter, following Thrun's Probabilistic Robotics implementation. I believe my correct step may be wrong, as the state appears to be corrected far too much.
...
