10
votes
Accepted
AprilTag vs Aruco markers
Aruco (as implemented in OpenCV)
pros
Easy to set up (with readily available aruco marker generator, opencv & ros implementation, etc.)
fewer false detection (with default parameters)
cons
...
- 426
6
votes
Accepted
State of a Robot
To extends the answer from the_parzival a bit:
There are different kind of robots so that 'robot state' can have different meanings. If you have a drone or Roomba-robot, the most important state is ...
- 1,355
6
votes
What's the difference between Pose Measurement and Position Measurement?
what you are looking for is written in the paper. Position refers only to x,y,z translational measurements while pose means position and orientation.
- 497
6
votes
Which is the best visual fiducial marker (2D barcode)?
AprilTag is the state-of-the-art solution for pose estimation. The library itself already has pre-built functions to compute the marker position, given its size. The pose is estimated by homography ...
- 161
5
votes
Accepted
How do I go about implementing a Kalman Filter for a pose estimation algorithm?
It sounds like you're using the camera frames to get a PnP solution, or something along those lines.
A linear Kalman filter will usually work OK for most purposes if you're using roll/pitch/yaw and ...
- 892
4
votes
Choosing the state vector for an EKF
In general, I try to obey the following two rules when selecting states:
Only use the states necessary for control, and
Choose states to be measurable properties, whenever possible.
For example, on ...
- 16k
4
votes
What's the difference between the term "pose estimation" and "visual odometry"?
It is also often the case that the author lacks knowledge, makes mistakes, or is adding unnecessary statements to their work. Just because it is published does not make it true.
In this case though, ...
- 4,385
4
votes
What's the difference between the term "pose estimation" and "visual odometry"?
Pose estimation means determining position and orientation.
Odometry is using a (any) sensor to determine how much distance has been traversed, so visual odometry is just clarification that the ...
- 16k
4
votes
Accepted
Integrating GPS into Graph SLAM (how orientation fixed?)
You can use a very low information matrix value at the orientation elements of your state, given that the information matrix is the inverse of the covariance matrix.
The covariance matrix ...
- 183
4
votes
Accepted
Calculate transform from different poses
I am just going to explain from the basics. So feel free to skip through the first part and scroll to the bottom if you want the answer.
Basics:
The 3 parameters of your pose are $x,y,\theta$.
These ...
- 1,831
3
votes
Accepted
Position vs Image based visual servoing?
The problem in both cases is to move the robot tool to some pose relative to an object. Let's assume the camera is attached to the end of a robot arm (eye in hand case) so we will consider this a ...
- 1,692
3
votes
smoothing the robot poses inbetween two known poses
To get a smooth trajectory you should not have jumps in acceleration and because you are talking about pose both rotational and translational accelerations should be smooth. You can achieve this with ...
- 311
3
votes
smoothing the robot poses inbetween two known poses
You could try to use a bezier curve (https://en.wikipedia.org/wiki/B%C3%A9zier_curve) to interpolate with a curve and via points between A and B'. Also, is this a mobile robot or a robot arm?
Do you ...
- 497
3
votes
Accepted
Number of diagonal elements in the pose covariance matrix
The quaternion part [q_x, q_y, q_z, q_w] has four numbers but is a representation of 3D orientation, which has 3 degrees of freedom. Another common representation ...
- 340
3
votes
Get a rotation to align a vector, n with another vector, a and be able to rotate around a
Assuming you are working in 3-dimensions, this is exactly what the cross-product does. To find the vector of rotation that rotates $\mathbf{n} \in \mathbb{R}^{3}$ into $\mathbf{a} \in \mathbb{R}^{3}$, ...
- 884
2
votes
Full 3D Pose (Scale, Rotation and Translation) Estimation using Gyro and Acceleromter sensors fusion
The packages you've found don't estimate scale or 3d pose because that's not really feasible using just an imu. The only way to get 3d pose from an imu is to integrate acceleration (adjusting for ...
- 2,794
2
votes
How many AR markers should I use to get the object pose?
Without knowing exactly what type of AR marker you are interested in, I'll talk about two types that I am familiar with: ArUco and April Tags. Both are AR markers that have open source libraries with ...
- 340
2
votes
Accepted
How to properly initialize every new pose in a Visual SLAM algorithm (namely DSO)?
DSO initializes the scene and camera poses with a specific scale factor such that the average inverse depth of the pointHessians is one. After the initialization the first two frameHessians are led ...
- 36
2
votes
How to detect writing on a chalkboard?
Since you are going to have a mechanism that can draw within a square why not put a light sensor on it and use the same mechanism scan for the opponent's move?
At the start of the game, scan all the ...
- 705
2
votes
Resources for object detection with 2D Laser Scanner (planar only)
I think you can divide your problem into two subproblems:
1) Partition your 2D scan into segments/clusters which represent single objects. A basic algorithm could be:
Start at first laser reading ...
- 21
2
votes
How can I calibrate 3 cameras without knowing global pose of the object & camera locations? How can I find the pose of each camera wrt the first one?
The process you need to go through is actually similar to the camera calibration procedure in OpenCV or other software. The chessboard is replaced by your robot, and you can skip the intrinsic ...
- 1,831
2
votes
Manually generate antipodal grasps for grasping
You can use GraspIt! from the moveit ROS metapackage. I would recommend, however, deriving your own vector approach for grasping objects. You have to give your grasping software your gripper ...
- 748
2
votes
Accepted
How to prove expression for relative pose in one frame given relative pose in another frame
Consider the graph below:
Starting from the point $2k+1$, we can count the transformations anticlockwise, ending up again at the same point; hence, the aggregate transformation shall be the identity ...
- 3,995
2
votes
Conversion of roll, pitch and yaw from ENU to NED
ENU = East, North, Up
NED = North, East, Down
So, if you have x_ENU, y_ENU, and z_ENU, then:
...
- 16k
2
votes
How to put ArUco markers in Gazebo Classic
This forum post and this blog post and corresponding example model are pretty helpful.
This is just a simple model defining a link which has a front visual and a back visual. The front visual loads ...
- 1,404
1
vote
State of a Robot
The answer by parzival is only a partial answer. Especially with robots with more than 3 axes, the matrix cannot be solved for a deterministic state, a famous example of this is Dirac's belt trick, ...
- 195
1
vote
State of a Robot
The state of the Robot refers to the properties of the robot that you want to estimate. If you take a 2D robot as an example, then you might be interested in its 2d position which refers to
$$
X(t)...
- 148
1
vote
For pose estimation, what is the typical range of the rotation values that are estimated? Is it from -180 to 180 degrees?
The range between -1 or +1 is a normalized range like you said. The question is the following: Were those values divided by 180 (degrees) or 2*pi (radians)? You should check any existant documentation ...
- 71
1
vote
For pose estimation, what is the typical range of the rotation values that are estimated? Is it from -180 to 180 degrees?
Check whether they are in radians. Most algorithms use radians for pose estimation.
- 354
1
vote
Accepted
smooth robot 3D trajectory using graph optimization
If your problem is small and uncertainty information is not available, you can just set it with identity matrices. Covariance or information matrix will let you set which relative pose to trust more, ...
- 1,527
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