Torque value from servo to plc

Bratt

Lifetime Supporting Member
Join Date
Nov 2003
Location
West Sweden
Posts
726
I have an application where a servomotor will rotate a load and during the rotation i want to measure the torque. Is it possible to use the torque value from the servo or should i add an external sensor? I'm guessing that the value from the servo is a calculated value and is kind of flickery. Anyone having any experience of this?
 
Its a siemens servo connected to a siemens S7 plc over profibus. I know how to read the value from the servo thats not the problem. My concern is that i'm under the impression that the torque value in the servo is calculated from the current and will therefore vary alot. But i'am not completly sure that this is true so i was wondering if anyone has done this before and if its better to add a torque sensor to get a better value.
 
You are correct. the torque value from the drive is based on the current. But keep in mind that, assuming a brushless PM motor with a 'typical' commutation scheme with a fixed phase angle between the stator and rotor fields, current is torque. So if the current is 'flickery' (good word, by the way) so is the torque.

However, this is torque at the motor. If you have significant transmission elements between the motor and load, the drive will report torque that isn't making it ti the load.

How accurate you relly need to be is a decision you need to make. However, if I were in your position I would at least try the drive torque value. If it is a little noisy for your taste, filter it.

Keith
 
Ok thanks for the info i'll give the servo a chance a then. I'm just gonna tell the mechanics to keep the sensor i mind so it would be easy to add if the servo option doesent work.
 
Our motion controller has been used in several position/force limit applications. THe drive was set up to output a analog 'ideal or modeled' torque that we could use for the force feedback. I don't remember what drives these were. All these applications were griding or brushing applications where fast response is necessary.
 

Similar Topics

Hello guys! I'm building a setup where I have to control Servo (S-1FL6) with proper torque value. In Stat words I found a word called: MELDW and...
Replies
0
Views
1,242
Hello, Would anyone happen to know what parameter in a PowerFlex 525 to have the drive trip if the torque permissive set point is exceeded...
Replies
3
Views
390
I have always controlled servos in Rockwell motion using position loop. I have an application where one process will push against a servo...
Replies
3
Views
244
Possible dumb question here, but how does running a motor through a gearbox effect a VFDs ability to limit the torque on the driven load? My gut...
Replies
2
Views
486
Hello, I am posting this question (regarding drive control) on this PLC forum because I see that there has been discussion regarding this issue...
Replies
2
Views
579
Back
Top Bottom