Control/ PLC questions

Describe how you would perform a 2-point linear calibration of a PLC analog input? The scaling is calculated in PLC ladder.



While tuning a servo, you notice that the servo does not follow the commanded motion profile very well. There is also a large position error after the move has completed. Describe the approach you would take to improve the servo’s performance.





Write a database query to return the ‘mass’ and ‘depth’ all mass and depth values from a database table named ‘production’ where the mass is between 1 and 2 kilograms. The ‘production’ table has ‘mass’ and ‘depth’ and a number of other columns. The mass is stored in kilograms.





A manually operated press is used in the manufacture of a part. The operator places the part in a fixture under the press and then presses the pushbuttons to lower the press to work on the part.

Draw the ladder diagram needed to control the manual press with two push buttons implementing anti tie-down control (both pushbuttons activate within 250 ms, either release will release the press).

Inputs – Pushbutton #1 (PB1), Pushbutton #2 (PB2)

Outputs - Lower Press (LowerPress)

Describe how you would do your homework :nodi:

Please help

These are not difficult. Pay attention you did not.

"I thought this was Q/A? Why is everyone judging my questions?

They aren't judging, just flat out refusing. You haven't shown any work. If you want help ask for it but show what you have tried. If you want answers, pay the smart kid in class.

You think anyone in here wants to work in the real world next to someone who didn't do the work?

ackees,

not trying to slam you, but we get hundreds of requests on this site for help, just an explanation of what they need. It could be homework or on a job, please help. that's it. we are more than willing to help provided you put forth the effort and show what you have done, that is the only condition. you will not learn anything if we do your work for you. if we do the work for you and you have to modify the code or have something similar, how will you do it? zip the program (forum rules), attach it to a post. we will look at your work and offer suggestions, show you the trouble.
regards,
james

posted to wrong section

Just use linear regression formula(e) for the first one. Ladder usually has an execute or compute function block which lets you write it more legibly.

Always blame the mechanical engineer for anything servo related.

What sort of database are we talking here? If it's stored as a bunch of arrays, then

You are definitely going to need a TON in there, some Contacts, and some coils. Maybe an R_TRIG?

AustralIan said:

Code:

j := 0;

FOR i := database_min_index TO database_max_index DO

  IF database_mass[i] >= 1.0 and database_mass[i] <= 2.0 THEN

    query_mass[j] := database_mass[i];

    query_depth[j] := database_depth[i];

    j := j + 1;

  END_IF;

END_FOR;

Click to expand...

That's one interesting SQL query.

Phrog30 said:

That's one interesting SQL query.

Click to expand...

Why do you assume it is in SQL?

AustralIan said:

Why do you assume it is in SQL?

Click to expand...

Just the way it was written, refers to database query, table name, columns and column names as 'xxx'. That's typical of SQL. Honestly, I can't think how you couldn't come to that assumption.

Well, SQL is the most likely. But hey, we are in the 20's now, maybe the OP isn't using an RDBMS for a single table of simple real values.

If they are using a SQL database, I sure wasn't going to write THAT query for their homework.

A manually operated press is used in the manufacture of a part. The operator places the part in a fixture under the press and then presses the pushbuttons to lower the press to work on the part.

Draw the ladder diagram needed to control the manual press with two push buttons implementing anti tie-down control (both pushbuttons activate within 250 ms, either release will release the press).

Click to expand...

Tell the person who wrote your test that two-button, anti tiedown control should not be implemented in PLC logic. It should be handled by a dedicated safety controller.