Questions tagged [ekf]

the extended Kalman filter, a filter for nonlinear state estimation.

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Usage of Falkolib(OpenSLAM)

I am using Falkolib for landmark extraction in a 2D environment. Currently I am using the testKeypointOC executable from the bin directory. I have changed the testKeypointOC.cpp file and the ...
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25 views

Are Indirekt KFs with non-linear changing statematrix EKFs for the error state?

I'm trying to implement an indirect kalman filter to estimate the pose of a differential drive robot using gyroscope and wheel encoder data. I found a fiew papers (1 - 3) describing this approach but ...
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Implementing ESKF

I'm currently struggling with implementing the Multiplicative Kalman Filter or Error State Kalman Filter as described by Landis Markley in Attitude Error Representations for Kalman Filtering. Sadly ...
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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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54 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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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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272 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 ...
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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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37 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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83 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 ...
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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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63 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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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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37 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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69 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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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 ...
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1answer
122 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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124 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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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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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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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
110 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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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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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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512 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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176 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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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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346 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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146 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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244 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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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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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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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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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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175 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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111 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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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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413 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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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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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 ...
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909 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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167 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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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
638 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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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 ...
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374 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 ...
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1answer
119 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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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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505 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 ...