I would like to get the properties of the signal for detecting if there are overlapping of signals in my model or if a signal line is not straight
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in the Aerospace Blockset in Simulink, the example model:
asbSkyHogg
in this block (asbSkyHogg/Vehicle System Model/Vehicle/3DOF to 6DOF/3DOF to 6DOF/calc alpha_dot) which is used to calcualate the rate of change of of angle of attack
The rate of change of of angle of attack is calculated based on the equation:
So, the acceleration (input #3) in body axes should be transformed to wind axes using the DCM Body-to-Wind as shown in the picture... but why the transpose block is added here???!! In this case, it's actually transformed to body axes again!!
I tried to comment through the transpose block, but I need confirmation if I'm wrong or not, and why it's added.
I have constructed a simulator in Simulink that simulates the position of an object. I want to visualize the X-Y position of this object in a matlab figure.
I exported the X-Y data from Simulink to matlab using the To Workspace block. From this I get an x and y time series data out.x_pos and out.y_pos. I can plot them against time with
plot(out.x_pos)
But the following does not work to get an X-Y plot
plot(out.x_pos, out.y_pos)
What is the best way to produce this X-Y plot?
Since no one helped me, I will present what I came up with after eventually reaching the right pages on the MATLAB documentation.
The To Workspace block exports the data as a timeseries object. This object has the values of the signal as a property called Data. To access the property one writes <object>.Data, so to obtain the desired X-Y plot one writes
plot(out.x_pos.Data, out.y_pos.Data)
I am pretty new to signal and image processing.
I attached a picture of what I am supposed to do from a paper (https://iopscience.iop.org/article/10.1088/1361-6501/ab7f79/meta).
Basically, an interferogram is recorded by a CMOS sensor in B/W, then each vertical and horizontal pixel line is taken singularly and "associated" with a signal representing the intensity of light reaching the sensor. Then, the signals are Fourier-transformed to extract information about frequency and phase (to unwrap using).
I have understood the final passage for the DFT of the signal, but I am stuck when I have to take the pixel line and the signal associated with it.
Ideally, in Matlab the workflow would be:
extract each pixel line
assign a "colormap" to the line (white = 1, black = 0, all the other shades in between?)
build my signal interpolating the values of the pixels
DFT the signal to extract frequency and phase
Is there a compact way to do so?
So far I managed to do this:
I imported the image of the interferogram (248x320 pixels, just a snapshot from the paper) and for the 124th horizontal line I obtained the signal, frequency and phase.
I am leveraging SimMechanics, SimElectronics, and Simulink to model a quadcopter system for an embedded system class project ( files here ). I have generated a 2nd Generation SimMechanics model of an F450 quadcopter frame, including the motors and propellers. We were hoping to develop a model of a quadcopter with only a single rotational degree of freedom around either the x or y axis. I was hoping to model this with a revolute joint connecting the quadcopter frame to the "world frame". However, the "revolute joint" block in SimMechanics only acts around the z-axis. How can I change the axis of rotation for a revolute joint?
It appears that another individual has asked the same question, but no one has yet responded to his question.
See Assembling Multibody Models in the SimMechanics documentation, in particular the section on "orienting joints":
To obtain the motion expected in a model, you must align its various
joint motion axes properly. This means aligning the joints themselves
as observed or anticipated in the real system. Misaligning the joint
axes may lead to unexpected motion but it often leads to something
more serious, such as a failure to assemble and simulate.
You can specify and change joint alignment by rotating the connection
frames local to the adjoining body subsystems. For this purpose, you
specify rotation transforms using Rigid Transform blocks, either by
adding new blocks to the body subsystems or, if appropriate, by
changing the rotation transforms in existing blocks within the
subsystems.
Why change the orientation of joints through body subsystem frames?
The primitives in a Joint block each have a predetermined motion axis,
such as x or z. The axis definition is fixed and cannot be changed.
Realigning the connection frames local to the adjoining body
subsystems provides a natural way to reorient joints while avoiding
confusion over which axis a particular joint uses.
For an example of how to rotate joint connection frames, see Model
Mount.
So the answer is to use a Rigid Transform block to change the orientation of the frames, you cannot change the axis of the revolute joint.
I think you should change it in your CAD file. Change your propeller axis to align with z axis. But you should only change the propeller axis, not the whole body.
I want to apply perspective transform in Computer Vision toolbox in simulink of Matlab. I need to get 4 points from mouse on a given image to compute perspective matrix according these points.
I want to use the first frame of movie to get points on it.
One possible way is to create a level-2 MATLAB S-Function block which takes input from "From Multimedia File" and shows a figure window with the first frame to the user. From the figure window you can use ginput to get mouse clicks and then send that as output Pts connected to "Estimate Geometric Transformation". After the first frame you need to continue to send the same Pts as output. See documentation for creating level-2 MATLAB s-function at
http://www.mathworks.com/help/simulink/slref/level2matlabsfunction.html
It is probably easier if you do this outside simulink, by reading the first frame and find the points using ginput on a figure window. You can then use some Constant blocks as Pts1 and Pts2 inputs for which you can set the values using set_param.