general question

DeHulk

Member
Join Date
Mar 2003
Posts
74
Hello,

System

Car-> simovert
Analoge distance measuring = laser
Other : PLC S7 300

There are 6 poistions the car can drive too

Question : what is the best way to make this ?

Connect the analogue measuring to the PLC and PLC-program decides when the position is ok and wich direction the simovert has to make the car go ?

Or


Can a simovert be programmed so that the PLC send a databit (profibus ) to the simovert wich tells the simovert wich way to go ? and the analogue measuring connected to the simovert ?

When both ways are possible ..wich what would you do?
 
DeHulk,

What is this project for? is it just to learn or teach? or are you building yourself an electric car of some description?
This sounds a fun use of a drive and PLC.

Can a simovert be programmed so that the PLC send a databit (profibus ) to the simovert wich tells the simovert wich way to go ? and the analogue measuring connected to the simovert ?

First off I know a bit about Siemens drives, but I am no expert.

What drive are you using? Then maybe I can be a bit more specific as regards to setting up the drive and what the drive is capable of. That is if you require assistance on this.

The answer to the first part is yes, sort of, you won't send it a databit, but a dataword, (that also depends on the drive type) the direction of the drive is determined by the speed reference, if a positive speed reference is given then the drive will run in a forward direction, reverse for a negative reference. I do believe that none of the drives have a facility for position feedback, thus enabling self positioning (unlike a GE DC300 drive), so all the position feedback and speed referencing, acceleration and deceleration will have to be done in the PLC.

Noting the above then the only way to go is with the PLC controlling the drive direction and position. Just one point, you can get laser measuring devices made by Sick that communicate on profibus, (I have a redundant one sitting on my desk that we had on trial, but it did not quite work out), that will save on an analogue card.

Perhaps someone like JRW will see this post and add a comment,

Good luck with this project.

Paul
 
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Laser measure could be in profibus as well as VFD.
There are reference points (mm) from laser and some acceptable 'Window' for every point f.e. +/- 10 mm.

There is some travelling speed f.e. 50Hz and then when car is nere of reference point, PLC calculete new speed for the car until car is in the window. Final speed in the window could be f.e. 6Hz.

Followed example have: PIW578 is laser in ProfiBus, 940 is ref.point for station 'Siirto OJ', 11 is dec.rampping, 130 is max. speed and 6 is min.speed, 'VaconDB.nv920_SP' is ref.speed to VFD via Profibus. Direction control have done elsewhere where location/ref.point tells the direction (if not inside the window).

s7.jpg
 
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