LabVIEW
step up - wait - step down
You are describing something that can be implemented as a simple state machine. Basically, you have a loop that runs at a reasonable rate, reads the force sensor with every iteration and outputs compression as a function of force reading, time, and "state".
The solution is independent of programming language, but since you posted in the LabVIEW forum, we can probably assume that you are looking for a LabVIEW solution.
What have you done so far? Can your program reliably communicate with the hardware? How far did you get and where did you get stuck? Can you show us some code?
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Hi cpalka,
You might also like to take a look at this thread where the OP wants to build a simple on/off controller to aim for a setpoint.
As RavensFan said, you probably need something like a State Machine to control the behaviour of your application, although other designs are possible if for some reason you really didn't want a State Machine...
Depending on the necessary accuracy of the 1 minute, you might measure the starting tick count and then keep checking until you reach a number 60000 greater than your starting value, or you could simply count iterations if you have a defined loop rate (e.g. if your loop runs every 0.5 seconds, you need 120 iterations - a For loop could also work for this). Note that in the latter case, any unexpected delays (e.g. your loop actually takes 0.6 seconds) will mess up the total time, in that situation becoming 72 seconds...
Hi cpalka,
@cpalka wrote:
It is not so easy doing the code in serial, every time that I use a Write block I need to add allays a Read block?
That depends - does the instrument require you to read something? Probably if you don't read, the response will build up in the buffer, which may cause problems, so best to read in that case.
Note that for the parsing, you can use the Scan from String node for more than one at the same time:
@cpalka wrote:
The For Loop can work here? It is possible in first for loop put inside it the speed of 20mm/min and the target Force=30kN, after that change for second loop and inside I put a small condition to maintain the 30kN force and target here 60s.
The third and last inside the decrease speed -22mm/min and target F=0 kN. I never use the for loop.
I think you'll be better using the described plans for a state machine.
Since you have specific bits of code to set the motor in the positive and negative directions, I'd suggest making those into a subVI (or pair of subVIs).
I notice that the string you're sending includes "79" or "-79", so if you can specify the speed, you only need one subVI - have it take the VISA Resource as an input and provide it back as an output, then also a pair of error wires and the speed as a numeric value (probably double).
That could look something like this:
Take care with the formatting of the number! Your manual probably has detailed information about the formatting of the values to provide.
Then you can easily call this VI in your main VI when you want to change the speed, for example in your hypothetically created State Machine whilst aiming for the correct speed.
You could also make a similar VI with a boolean input for the $IDE {0,1} command to open and close the port, if you wanted. The Append True/False String node might be particularly helpful for this.
