I'm using Matlab 7 and have a problem in creating a monoflop which shall raise for a specific time to "1" and after that time fall to "0". How can I do this with Matlab/Simulink 7?
I don't have any other version, so I can't use the "Monostable" Block from newer versions.
Any ideas?
greets, poeschlorn
There are a couple of ways to do this, depending on whether or not you want the pulse (i.e. "monoflop") to occur at a predetermined time or in response to another signal (like a rising edge)...
Creating a pulse at a predetermined time:
If you want to create a single pulse that steps from 0 to 1 at time tOnset, then steps back to 0 after a time tDur has elapsed, you can do this using a Step block, a Transport Delay block, and a Sum block. Here is what the layout would look like:
You would set the Step time of the Step block to tOnset, the Time delay of the Transport Delay block to tDur, and then subtract the delayed signal from the original signal.
Creating a pulse in response to a rising edge:
This is will be a bit more complicated. It will require two Detect Increase blocks, a Relay block, a Transport Delay block, a Gain block, and a Sum block. Here's what the layout would look like:
Assuming your input signal is either a 1 or a 0, the first Detect Increase block will output a 1 when the input steps from 0 to 1. By setting the Switch on point to 0.5 and the Switch off point to -0.5 for the Relay block, this will create hysteresis in the Relay such that the output will persist in the "on" state (i.e. an output of 1) after the brief pulse that occurs when the rising edge is detected.
To get the Relay block to switch back into the "off" state (i.e. an output of 0) after a specified time tDur, you would set the Time delay of the Transport Delay block to tDur. The Detect Increase block in the feedback loop will output a 1 when the delayed signal steps from 0 to 1, and this output will then be scaled by setting the Gain of the Gain block to 2.
When subtracted from the input signal, this gain will ensure that the output from the Sum block can be pulled below -0.5 no matter what the positive input is (0 or 1), thus ensuring that the Switch off point of the Relay block is reached and its output is turned off when the delayed signal has a rising edge (i.e. after tDur has elapsed). One result of this is that any additional rising edges occurring in the model input after the first rising edge and during the time tDur will be ignored. Once the output from the model returns to 0, the next rising edge on the model input will trigger another pulse.
Related
How to detect the 2nd falling crossing when it reaches the 2nd point. The signal will rise again after the 2nd crossing and then repeats.
Each time the signal falls at 20(2nd time) i want to capture it via relational block like the output signal in the image
Input Signal:
Model:
Output
There are multiple ways this could be done. One approach is to create a triggered counter, using a Triggered Subsystem, with the counter resetting itself if the count tries to go above 2.
An example of this is shown below. The trigger is generated by comparing your input to a constant (in this case 20) and incrementing the counter based on a rising edge of that trigger. Initialize the counter to 1, then either
increment the counter if the count value is currently less than 1.
reset the counter to 1 if the counter is already at 2.
In this example the counter resets every second crossing of the threshold.
If data typing is important this could also be done using logical/boolean values (i.e. True and False), rather than the 1 and 2 used in the example.
Using the answer above by Phil, i was able to create my version without using triggered subsystem
Sample answer
I need a subsystem that needs to output 1 at interval or 30 seconds or slightly over 30 seconds.
Written in matlab code it should work like that
function y = fcn(time,uplinkTimeInterval)
%#codegen
persistent lastTriggerTime
if isempty(lastTriggerTime)
lastTriggerTime = 0;
end
if time>=lastTriggerTime || time == 0
y = 1;
lastTriggerTime = time + uplinkTimeInterval;
else
y = 0;
end
end
where ulplinkTimeInterval is 30 seconds. Of course I tried to use the matlab function block with this code but for some reason it does not work (in debug mode I can see that y takes value 1 as it should but it simply does not ouput the value outside the block), therefore I wanted to use blocks but I do not know how to do it.
Thanks very much for your help
You can make this logic relatively easily with code or blocks. As you requested a solution using blocks, here it is!
Use the clock block to keep track of time, and some constant block to determine the interval (in seconds) at which to give 1 instead of 0.
Use the memory block to delay the clock signal by 1 timestep, so we can compare consecutive steps' values.
Divide the times by the interval, and round down, to give how many intervals have passed.
Finally, compare consecutive "number of intervals passed" using a relational operator. If more intervals have passed on the upper line, then you have just stepped over the interval threshold.
Note: this will return a 0 for every timestep where you have not crossed a new interval, and a 1 at each individual timestep where you have. The accuracy of the output will depend on the step size of your model.
Edit: It may be clearer / easier to just add the memory block after the floor block, so you are only doing the division / rounding once. It would still allow you to do a comparison to the previous time step. That would look like:
Easiest way to do this is with a just a single Pulse Generator block, set to have a "high" of 1 every 30 seconds. That is shown as part of the image below. The signal will be high for whatever the percentage of the period is specified in the block dialog.
If for some reason you really need to use a subsystem then use a Triggered and Enabled Subsystem (See top right of image). Feed the same pulse signal into both the trigger and the enable port, and set the outport inside the subsystem to have Output when disabled to reset, and to have an Initial Output of 0 (See the lower right of the image).
The model below shows how to do this. In this instance the pulse has been set to have a period of 30s with the rising edge happening every 1% of that period (See the top left of the image).
The output signal will be high for one time step every time the input rises (assuming the trigger is set to rising edge.)
In Simulink how can I delay the transport block to the exact time of when a certain threshold has been reached?
Basically I have an S-function which switches to an alternate input source, a sine wave, after a certain value has been reached. As soon as the switch occurs I want to start the sine wave. For that I need to delay the wave generation until the switch occurs.
How can I send that time to the Variable transport delay block?
Maybe you can try this way:
you need Variable Integer Delay for example. It changes delay to what you need. Calculate needed value of delay you can in User Defined Function, route to it your threshold value and current time and all other values you need.
Hope i understood your question correctly!
I have an incoming data and I would like to store it and then Output this data but after a certain delay, after some milliseconds i Output this data.
I used the Queue block inside an enabled Subsystem and the Trigger Signal is the clock divided by 10, So i have evrery time .. every 0.1 second i Output the values from the block,.. but the data is accumulated, not delayed. any idea why?
Here is the Picture of this Operation
and
EDIT: You now show how are you storing the signal. And The queue block is used wrongly.
If you want just to delay a signal, and output it delayed, then use my answer below. I am unsure what you mean by store it by N time and then output it. Simulink is "continuous" thus you can not output it "in one go" after N time, that makes no sense. The closest thing to that is to delay the singal, and for that, you dont need that enabled subsystem, you just need the Transport delay block.
ORIGINAL
What about the Transport Delay block?
It looks like this:
and It allows you to set the delay time in seconds, isntead of in ticks (as z^-1 does).
I am new to Simulink and I am trying to model an oscillator to control an automation controller.
The question is:
I created a pulse generator that results in a square wave. To design the oscilator I need that 2 others chanels (one is the same signal, while other is the reverse) remain in zero when the input (the square wave) is oscillating. The problem is that I can't make the other 2 signals remain in zero. I tried using the blocks for discrete elements in the library, such as: "Delay", "Unit Delay", and even "Zero Order Hold". Every block just shifted the entire curve, while what I need is to delay the signal when it assumes the "1" value.
Follows some prints:
I have no reputation for all the images so: the subsystem consists of 3 pulse generators, and theres a scope linked to the subsystem
Please Help!!!!
It sounds like you're asking for a signal that rises at some pre-specified delay after the pulse generator rises, but falls at the same time as the pulse. This is shown in the picture below,
If that's correct, then it can be created using an enabled subsystem, where the subsystem contains only a unit delay, as shown in this picture,
Within the subsystem you must also
Set the Enable block to reset its states.
Set the Outport block to reset its value when disabled AND set an initial value of 0.
Specify an appropriate sample rate in the Unit Delay block (this acts as the amount by which the rising signal is delayed)