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# Questions tagged [estimation]

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### Confusion on optimizing variable time-offset for VIO SLAM

I was reading the following paper on how you can incorporate variable time offset for a camera in VIO: https://openaccess.thecvf.com/content_ECCV_2018/papers/Yonggen_Ling_Modeling_Varying_Camera-...
• 359
9 views

### Is it possible to do uncertainty propagation with TF2? If not what can I use?

I'm interested in applying a sequence of linear transformations to a gaussian probability vector in TF2. As far as I understand this is a pretty operation due to the gaussian nature and I see TF2 has ...
• 359
13 views

### How to transform the detected target pose into the pose in the camera coordinate system in Gazebo

that is my code ...
37 views

### What are some resources to learn Probability, Statistics and Stochastic Processes so I can understand Optimal State Estimation?

I went to grad school for Mechanical Engineering almost 7 years ago, where I avoided any probability/stats coursework like plague and stuck to linear algebra and differential equations for my math ...
22 views

### Does the Factored Quaternion Algorithm Account for Declination?

Looking at the documentation for the Factored Quaternion Algorithm (FQA). In section 2 they define NED as the traditional Earth's fixed coordinate system, thereby referring to 'true' north. However, ...
1 vote
30 views

### Observability of Gravity in SLAM

A number of SLAM systems only optimize over 4 variables(location and yaw) as they argue gravity is observable which constrains roll and pitch. I don't understand this argument since in theory you ...
• 359
273 views

### Estimating gyroscope bias for attitude IMU sensor fusion with an unscented Kalman filter

I'm trying to use a UKF as the attitude estimator for a drone with just a gyroscope and accelerometer as sensors. So far, it's going well and after some tuning appears to perform basically as well as ...
62 views

### Rotation of a point in 3D space

I want to rotate a point (3,4,5) by an angle 45 degrees(0.785398 rad) in 3D space. I have used the standard DCM matrix in the order Rx, Ry and Rz. Where, theta = 0.785398, Rx= ( [ 1, 0, 0] [ 0, cos(...
1 vote
316 views

### Is Luenberger observer applicable in practical systems?

I have tried to find out about this from quite a few sources but it still remains unclear to me. I know that the Luenberger observer is applicable for a deterministic system with known control inputs ...
• 111
1 vote
60 views

### Covariance of fused poses. Should it be normalised by the number of poses?

I came across this paper from T. Barfoot and P. Furgale: "Associating Uncertainty With Three-Dimensional Poses for Use in Estimation Problems" Link: http://ncfrn.mcgill.ca/members/pubs/...
• 13
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### UKF for a serie of observations with covariance

I have some doubts about how to implement a UKF-like algorithm when I only have motion observations and no control inputs. Assume I have a robot with state $s_t = (x_t, y_t, \theta_t)$ and the ...
1 vote
759 views

### Obtaining Heading vector from IMU

First time here. I'm an electronics engineer who has been tasked with this problem: Given the 4D quaternion representing a vehicle orientation, how do you get the heading vector? The vehicle ...
• 111
198 views

### How to compute the Hessian matrix in the robustified Gauss-Newton method for optimization

When robustifying the Gauss-Newton method used to find a local minima of a squared error function expressed by: $$f(\mathbf{x})=\frac{1}{2}\Delta\mathbf{z}(\mathbf{x})^T\Delta\mathbf{z}(\mathbf{x})$$, ...
• 123
304 views

### Unstable principal point estimation in zoom camera calibration

I have a camera with a 1/2.9" image sensor from FLIR and a 12-50mm motorized zoom lens from Theia. Because the lens is a motorized zoom lens, I tried to calibrate the camera for different zoom ...
• 31
84 views

### Is this encoder error expected?

I'm working with the iRobot Create 2. When I read the encoder count and sum it for total, I'm able to do so without apparent error. I've used this to 'successfully' estimate position combining with ...
79 views

### EKF Update Step measurement data doesnt fit state vector

I have an EKF SLAM Algorithm which tries to estimate the robots position (X,Y,Theta) + the X,Y coordinates of several landmarks. Like in the posted algorithm i have a range/bearing sensor. I ...
709 views

### Visual Odometry terminology: Scale, Relative scale, absolute scale

I'm watching a MOOC about Machine Vision for Robotics, but I really do not know the meaning of some vocabulary of this domain. For example, What does the professor mean when he says this: However, we ...
• 189
65 views

### wheeled vehicle forward velocity from RPM brushless data

I'm trying to hack an electric RC car with the goal to make it autonomous, as part of my PhD research. The mounted ESC is able to send back telemetry data, including the spinning velocity (in RPM) of ...
• 103
324 views

### Particle Filter for IMU tilt angle and bias estimation from Kalman Filter models

I understand the functioning of Particle Filters from the book Probabilistic Robotics and the robotics course provided by Cyrill Stachniss. I want to implement, from scratch, a particle filter to ...
168 views

### Why Does an Exponential Make ANYTHING a Probability Distribution

I am posting this here because my background in estimation theory and optimization has been developed entirely through my experience in robotics. TLDR: What makes it so that any time you put something ...
• 120
117 views

### Kalman Filter Design

I'm new to Kalman filter design and I'm struggling to understand how to apply the Kalman filter methodology to my problem. I've read a research paper which seems to describe what I'm trying to do ...
• 69
496 views

### Is the covariance matrix in the extended Kalman filter guaranteed to be positive definite (ignoring numerical errors)?

I understand that due to numerical errors (e.g., round off error and machine precision) that the covariance matrix may not be positive definite, but if computers had infinite precision, is the ...
• 345
58 views

### Synthesis gradient observer

I ask the advice of specialists on control systems. We have the following system. Where $u(t)$ and $y(t)$ time-varying input and output. The characteristic $y(t)=f(u(t))$ is assumed to be non-...
• 183
429 views

### Estimate noise covariance matrix of measurements using a ros-bag

I am facing the following issue, and some hint or orientation would be great. I am working on a project in which I was given a ROS bag, and I have to implement a localization node using SLAM. To do so,...
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332 views

### Applying Rotation & Translation Matrix Obtained from Iterative Closest Point

Suppose I have M lidar contour points from t = k and N lidar contour points from t = k+1. (Some of you might question why I have differing number of contour points, and the reason is that these lidar ...
493 views

### How do you handle angle discontinuities in estimation problems?

When one is implementing a state estimator in a system that involves kinematics, will inevitably face the problem of angle discontinuities, i.e., the fact that the angles have to be wrapped between ...
• 21
62 views

### How do I get competent in using c++ for my projects? [closed]

I am a PhD student, working on Sensor Fusion and estimation problems. I would like as I finish my PhD to have acquired sound knowledge in what seems to be the industry norm for working with real ...
• 21
1 vote
117 views

### Reset coordinate system of robot while maintaining relationship to the previous

I am currently estimating a robot's pose (3d position and rotation matrix) with an IMU and I want to reset the localizer in the middle of the run while keeping the relationship to the pose it had when ...
• 11
231 views

### Advantage of Kalman filter in differential drive planar robot

We need to estimate the position and orientation of differential drive robot by using encoders and imu sensor. For this specific case, is there any advantage of using Kalman filter than taking the ...
• 149
430 views

### Fusing IMU sensor with odometry

Would fusing Odometry estimation with IMU sensor increase the accuracy of estimation for planar differential drive robots?
• 149
62 views

### 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 ...
• 1
1 vote
593 views

### The biases in the state vector of Extended Kalman Filter(EKF)

I am reading one paper on observability Observability Analysis of Aided INS with Heterogeneous Features of Points, Lines and Planes. The state vector contains the current IMU state and the feature ...
• 273
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### Wheeled Mobile Robot State Estimation Model Using Odometry

I have a process model update that follows the form: $$\mathbf{x}_{k|k-1} = \mathbf{x}_{k-1|k-1} + \delta \mathbf{x}_k,$$ where $\mathbf{x}_{k-1|k-1}$ is the posterior estimate from the last ...
• 121
4k views

### Orientation from magnetometer data

I saw lot of topics with the same title but answers are different. I have a magnetometer in my phone which give me the components of magnetic field in direction of X, Y, Z. If my phone lays on a ...
6k 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, ...
434 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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### Methods for state estimation and real-time path planning of a mobile robot

I'm looking to start a project that incorporates some form of state estimation and path planning for a simple simulated robot dynamic model, in an environment that contains obstacles. I'm hoping to ...
2 views

### Accessing previous estimated joint states of a robot

Hi, I am new to ROS and I am trying to implement a Kalman filter for estimating the joints velocity and acceleration of a robotic manipulator. The angular position of each joint is published to the ...
505 views

### How to properly initialize every new pose in a Visual SLAM algorithm (namely DSO)?

My question is a bit specific, because it is linked to a certain algorithm. Therefore I didn't find any other solutions on how to go about this problem. If you could refer me to research papers, ...
361 views

### How can I compute the covariance of a camera-based relative pose measurement?

I am trying to compute the relative pose between two cameras using their captured images through the usual way of feature correspondences. I use these feature matches to compute the essential matrix, ...
• 1,106
6 views

### find position of object in a bag

Hi guys, I need to find(estimate) the 3D position of the 'people in the scene' -- (this is in the bag file) with respect to the camera. My code is : (I didn't write it) ...
1 view

### Zigzag ground track from eight shape flight path

Hi all, I tried to using ukf template recursively with navsat_transform node following http://answers.ros.org/question/200071/how-to-fuse-imu-gps-using-robot_localization/ With my eight flight path it ...
35 views

### amcl restore own position automatically

sometime AMCL can't localize itself in the given map while moving. such as in alike environments. In similar cases I use pose estimation button for real position of robot. But is there a way to detect ...
3 views

### Multiple static target position estimate

An aerial vehicle captures images of the ground, using a down facing camera, in order to detect some static ground targets. Using opencv I created a node that detects those targets and converts their ...
22 views

### amcl estimation quality

I would like to know how much to trust the amcl output pose. One thought is to see how well the laser data correlates with obstacles in the cost map, another is to calculate the variance of the ...
5 views

### AMCL parameters spreading out is good or bad?

hello... I cant understand , How do I decide whether the amcl parameters result is good. so AMCL Pose estimations spreading out is good or bad ? which image is good result ? this my new amcl ...
19 views

### State Estimation and Localization in Robot Navigation

Hello, I would like to ask the difference between a state estimator like robot_localization, or robot_pose_ekf and a ...