Questions tagged [ekf]
the extended Kalman filter, a filter for nonlinear state estimation.
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Differences between strapdown inertial navigation and motion models
In a state estimation scheme with a simple IMU/GNSS setup using EKF, I have always thought the prediction step would be done using a motion model and all sensor measurements would be incorporated via ...
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1answer
47 views
EKF SLAM : SLAM specific Jacobians for new landmarks
I am currently trying to understand the books SLAM for dummies and Simulataneous localization and mapping
with the extended Kalman filter to implement slam. I have understood steps 1 and 2 SLAM for ...
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25 views
Question about EKF SLAM (w/ unknown correspondence) update step
In Probabilistic Robotics, page 322, the EKF SLAM update step is shown below.
My question is, why is for every observed feature, $\bar{\mu}_t,\bar{\Sigma}_t$ are overwritten in lines 23,24 by the ...
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3answers
188 views
Do I need a camera along with LIDAR for SLAM?
Equipment:
Pi 3 B
Mega
2x Encoder Motor 12VDC 299RPM
MPU 6050
12V bat 2000mAh
LIDAR or Kinect ?
I want to implement EKF SLAM. I have referred bot NOX ROS wandering robot, Hussarian CORE and Robotics ...
2
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1answer
85 views
How is the GPS fused with IMU in a kalman filter?
I've been trying to understand how a Kalman filter used in navigation without much success, my questions are:
The gps outputs latitude, longitude and velocity.
While the IMU outputs acceleration and ...
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1answer
36 views
How to perform active search in point feature based monoSLAM?
I am modifying an implementation of SLAM with single camera, MonoSLAM [1]. Instead of image patches, I want to use features points (ORB) to track landmarks. MonoSLAM uses a EKF framework. So for ...
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0answers
70 views
How to calculate observation matrix Jacobians in EFK based mono slam? What are projection Jacobians?
I have been trying to understand an implementation of monoSLAM 1. But my question is generic to EKF based single camera SLAM.
My Jacobian calculation leads to complex and lengthy expressions while ...
2
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1answer
61 views
extended kalman filters, linearization of output
Say, we are dealing with an odometric localization problem.
In the below example, $(x_k, y_k), (x_l, y_l)$ are cartesian coordinates of the sensor and the landmark respectively. Then the output ...
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1answer
62 views
why innovation equation in Extended Kalman filter is called innovation? [closed]
In the extended Kalman filter for SLAM, why the innovation equation is called innovation? Is there any reason behind it?
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1answer
60 views
Doubt with linearization and discretization process - Ekf
In the paper "State Estimation for Legged Robots - Consistent Fusion of Leg Kinematics and IMU", the authors describe the application of an extended kalman filter to estimate states of a quadruped ...
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1answer
33 views
EKF singularity problem when measurement noise R is zero
my Extended kalman filter (EKF) program works well, my estimated state vector is same as real state vector when I give any positive definite number to measurement noise R. But I want to make ...
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1answer
56 views
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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2answers
57 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
120 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 ...
2
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2answers
115 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
44 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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3answers
884 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
79 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
109 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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1answer
76 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
31 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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1answer
502 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
165 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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2answers
110 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
332 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. ...
2
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1answer
142 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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1answer
236 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
140 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
127 views
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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0answers
127 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
2k 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
168 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
108 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
99 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
403 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
280 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
132 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 ...
2
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1answer
892 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
165 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 ...
2
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0answers
114 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 ...
4
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1answer
615 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 ...
3
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2answers
269 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 ...
2
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2answers
366 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 ...
2
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1answer
118 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 ...
3
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2answers
497 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 ...
3
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1answer
189 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 ...
4
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1answer
164 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, ...
3
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1answer
164 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 ...
