Timer-ramp

magenuss

Member
M
Join Date
Apr 2011
Location
Sørlandet
Posts
4
I'm making a control system for a robotarm, which is beeing controlled by a joystick. When the joystick is no longer used, the movement of the arm needs to ramp down. My guess is that I need to use timers.

I need help from you amazing experts to make this program.

How can I make a accelerating/decelerating ramp?

I've tried this, did not understand it all.
http://support.automation.siemens.com/WW/llisapi.dll?func=cslib.csinfo&lang=en&objid=1853767 - this does not work, it says "the symbol information of the block is invalid"
 
Is your setpoint a (parking) position, angle or speed or ...?


You can make a ramp function by calling an add function in certain time intervals, i.e. ADD_R called from OB35. You will need a limiter function as well (CMP_R + MOVE).

Kalle
 
Tusen takk Kalle!

It's controlling a servo valve, which again gives out a flow, which affects the speed of the robotarm.

So it's not timer i should use?
Could you explain in more details, please? :) I'm new at PLC programming.
 
If the ramp function is unknown to you, I'd expect you'd have/get other programming problems aswell.

Here is a link to an extensive library, also containing a ramp function.
www.oscat.de

Remember to download the BASIC DOC.

And: I presume this is some kind of a school work?
 
From the robotarm? Yes, we calculate the angle from the force (by advanced geometry and dynamics).

I'll rewrite my question:
Is there a simple way of using timers to ramp down a signal? If someone could make a simple diagram, I would be eternal grateful.
 
For Count Up timers:
REF_OUT = REF_VAL * (TIMER_PRESET - TIMER_VALUE) / (TIMER_PRESET)

For Count Down Timer:
REF_OUT = REF_VAL * (TIMER_VALUE) / (TIMER_PRESET)

It's up to you to ensure that you are modifying the reference by that kind of timer based ramp at the appropriate times.
 
magenuss said:
From the robotarm? Yes, we calculate the angle from the force (by advanced geometry and dynamics).

I'll rewrite my question:
Is there a simple way of using timers to ramp down a signal? If someone could make a simple diagram, I would be eternal grateful.
Click to expand...


Why do you want to use timers?

Isn't the task to ramp a signal from level A to B (0?) in a certain time? Or eventually with a certain ramp slope?


Kalle
 
This is a timer based rampdown as rdrast suggested. It is a simple Step7 FBD-code, just to give you an idea of what you was asking for. (If you'll like a perfect version, wait and see if LD pops in.
icon10.gif
)

timerramp.jpg
 

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