13
votes
Accepted
Hand Eye Calibration
After solving the problem, I created a keynote presentation explaining many details about hand eye calibration for those that are interested. Practical code and instructions to calibrate your robot ...
- 486
8
votes
Accepted
Why do 3-axis accelerometers seemingly have a left-handed coordinate system?
The answer is that 3-axis accelerometers don't have a left handed coordinate system just for the gravity. In static condition (i.e. if the accelerometer is not accelerating with respect to any ...
- 151
7
votes
Accepted
Why do we generally prefer DH parameters over other kinematic representations of robot arms?
I have been doing a lot of reading up on kinematic calibration and here is what I found:
From [1]:
A kinematic model should meet three basic requirements for
kinematic-parameter identification:
...
4
votes
Accepted
Inverse kinematics after calibration
The analytic inverse kinematics solutions you found do depend on those $0$ terms in your transformation matrices. Those values are, as you've implied, based on the $0$ and $90$ degree values for the ...
- 4,366
4
votes
Why are two cameras mounted in paralle in stereo application?
Each camera needs to be defined by 6 variables (3 position, 3 orientation). This would mean that during the calibration process, a solver needs to find 12 variables. As this is done usually with an ...
4
votes
Why do we generally prefer DH parameters over other kinematic representations of robot arms?
The link, What are the advantages of using the Denavit-Hartenberg representation?, in Paul's comment provides a correct synopsis.
Additional, practical benefits are:
DH provides a guaranteed minimal ...
- 275
4
votes
Accepted
Practicality of using magnetometer inside AUV
Mags are used in almost all UAVs. It will be useful and it will be a unique source of information.
Adding a some shielding between the mag and your computers and power lines will greatly reduced the ...
- 1,833
4
votes
Accepted
Why do we need to know the translation between Camera and IMU?
You answered yourself.
Your underlying model of point moving through space usually assumes the center of gravity to match the camera frame.
If your inertial sensor have a translational offset from ...
- 211
3
votes
Accelerometer calibration - how to get cross-axis sensitivities
I realize this question is 2 years old, but I have direct recent experience with this. The way I did this is with 6 rotated cube positions with 1000 points at each position, so a total of 6000 ...
- 141
3
votes
Accepted
Question about Lens distortion
You can only say that the distorted image coordinates are in the range (0-240, 0-180), since that's the image you are starting with. Typically you assume the dimensions of the undistorted image as ...
- 1,652
2
votes
Why do 3-axis accelerometers seemingly have a left-handed coordinate system?
This is not using a left-handed coordinate system! Check out my crude edits to the diagram.
Note each coordinate system (RGB for XYZ, black for gravity) has the gravity vector aligned in the negative ...
- 1,377
2
votes
FreeIMU External Magnetometer
OK so I managed to solve this by doing a couple of things.
Connect external magnetometer to the same I2C bus as the FreeIMU.
The FreeIMU is 5V and the external magnetometer is 3.3V so I had to use a ...
- 227
2
votes
Gauss Newton Method for Accelerometer calibration
$J^T \times J$ is an approximation to the Hessian which comes from the Levenberg Marquardt Algorithm. It is a least-squares approach, and seems to be used frequently in a variety of optimization ...
- 4,366
2
votes
Wheel Odometry Covariance Matrix for Custom Robot
The covariance matrix of the control inputs is measured and known.
That is, following the EKF equations on this page, the covariance of the control, $Q$ is (often) a diagonal matrix, where the ...
- 5,272
2
votes
How is gyroscope bias exposed and tracked?
I think you're confused. The method you're talking about would only really work if you know the magnitude and orientation of the accelerations you're trying to measure. If that's the case, then why ...
- 15.7k
2
votes
Accepted
OpenCV get topdown view of planar pattern by using intrinsic and extrinsic from cameraCalibrate
Added
OK, guys, simple mistake. I previously used warpPerspective to warp images instead of restoring. Since it works that way, I didn't read the doc thoroughly. It turns out that if it is for ...
- 51
2
votes
Accepted
Calibrating Logitic C920 HD 1080p using ros kinetic
Based on rostopic list I realized the correct name of camera:
/usb_cam instead of /camera
so the command changed to
...
- 151
1
vote
Zero-Point/Home Position/Origin of Absolute Encoder: What is the Proper Name?
How are you getting zero angle if it's not reading zero angle? Is this some arbitrary thing you do on startup? Was this a one-time reading you took and it works every time the thing starts up, ...
- 15.7k
1
vote
Hand eye calibration wrong result
If the rotation looks right but translation look deviated, noise might be an issue. Usually rotations are more robust to noise than translations when using the calibration equations.
Synthetic data ...
- 111
1
vote
Accepted
Hand eye calibration wrong result
In my case the reason for the wrong result was high amount of noise in extrinsic calibration of the visual sensor. Improving the extrinsic results by increasing image resolution and using better ...
- 186
1
vote
Accepted
Can someone explain what is going on in this calibration video?
Let b, the bias error of a sensor.
If you take two measurements of a known value (gravitational acceleration in this case), in opposite directions, say m1 and m2, without any bias towards any ...
- 411
1
vote
normalized point coordinates in undistortPoints function
http://docs.opencv.org/2.4/modules/calib3d/doc/camera_calibration_and_3d_reconstruction.html, this link maybe helpful. Here is my answer based on that.
1.What does normalized point coordinates means?
...
- 111
1
vote
Calibrating a laser scanner to a line camera
I converted my comments to an actual answer:
If I understand your setup correctly, you're saying you have a line scan camera mounted to the top of the rotating head of a laser scanner, and all you're ...
- 15.7k
1
vote
Correct Fish eye camera radial distortion and blurry stretch at the image edges
How I can I include more FOV in the corrected image at the edges, where the information is lost?
-> Just try to modify fx and fy of your intrinsic matrix. Maybe, multiplying a scalar to K(0,0) and K(...
- 1,487
1
vote
Correct calibration parameters of stereo system due to vibrations
You could use g2o library for this. With it you can make a graph whose nodes are estimates of some states (point positions in 3d, point positions on images, extrinsic calibration parameters) and edges ...
- 850
1
vote
setup requirement of stereo camera
If you glue two cameras to a wooden board, and then write your code with the assumption that your translation matrix is perfectly or really close to [1, 0, 0], once the cameras are slightly displaced, ...
- 1,101
1
vote
Effect of camera misalignment errors in dual cameras
Because each have diferent reasons (and so can be helped/worsened in different ways).
And the calibration will help only in specific setup and needs be done differently for different setups.
The ...
- 453
1
vote
Wheel Odometry Covariance Matrix for Custom Robot
Josh, thank you for your help!
From my understanding it seems that a basic process for determining the velocity covariance matrices of a 3D (X,Y, Theta) robot with N wheels would then be (please ...
1
vote
Why are two cameras mounted in paralle in stereo application?
Making them parallel is beneficial for reducing distortion after a rectification. We usually rectify two images for a fast matching. If speed is not your concern you can skip the rectification stage.
- 1,487
1
vote
Accepted
Discontinuity in device orientation
Something's not right, either with your test, your conversion, or with the device itself. If you look at your graph of heading, pitch, and roll, you can see that heading rotates through 360 degrees, ...
- 15.7k
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