S7-1500T CAM Problem

Hi,

I am working on a project with following Hardware:

• S7-1511T CPU
• TM Count 2x24VDC
• V90 PN Servo 1KW, with 2500PPR incremental encoder Motor (Traversing Drive)
  
• Danfoss FC051, 1KW induction motor (Spindle)

The setup is such that there is an incremental encoder (1000PPR) connected on Spindle, which is wired to 1-channel of TM Module configured as HSC in HWconfig, and used with TO External Encoder. The Traversing Drive is configured as TO Synchronous Axis, with a leading value interconnection of Actual value External Encoder.

I am using TO CAM to synchronize the two axis. Once both axis are InSync (MC_CAMIN), I vary the speed of Spindle motor via Operator panel on FC051 drive and notice a visible difference in positioning of Traversing drive wrt Spindle position. At constant speed of spindle motor, the profile is perfectly aligned to what is defined in the CAM Profile graph. But during speed changes, e.g. spindle accelerating/deceleration (acc/dec time =0.5s) the Traversing drive deviates from defined profile, and starts accumulating an ever increasing offset.

I have tried the following but failed to achieve the desired results:

• Tried, increasing the acc/dec time of spindle drive to 3seconds. The error minimizes but is still there and visible, also this acc/dec time is not suitable for the application I am working on
• Tried re-tuning the servo Precontrol and Gain KV, no noticeable difference in error
• Tried adjusting the Following axis dependent extrapolation time in TO External encoder. TO Synchronous axis abruptly stopped on following error.

Can anyone give his/her insights on how to reduce the error generated because of master speed changes in cam profile?

Is there any application note or documentation available other than S7-1500T Motion control manual and help files, that discuss the related parameters in detail?

Best Regards,

Anas

Hi,

All filter values are at default setting "0.0"

TIA Portal V14 SP1

S7-1511T Actual firmware version is 2.5, HWconfig/project version is 2.1 since 2.5 is not available in catalog.

I will do the traces today, and update you.

Thank you for helping

Regards,

Anas

I have attached the requested trace files.

fine5_fast_TD_PV_vs_WE_PV_vs_TD_SV.ttrecx

Logged values: Traversing drive actual position vs Winder encoder actual Position vs Traversing drive command position.

Logged at required speed of spindle motor

fine6_slow_TD_PV_vs_WE_PV_vs_TD_SV.ttrecx

Logged values: Traversing drive actual position vs Winder encoder actual Position vs Traversing drive command position.

Logged at much reduced speed of spindle motor

The configured CAM has three points (including slave offset, these are the coordinates of profile)

1. 0,51
2. 30130.29, 1831.7
3. 60260.57, 51

From both the trace files it clearly shows that Traversing Drive is deviating from the programmed profile. The commanded position doesn’t even reach the programmed values(Error:0.96mm), and consequently actual position has greater error of upto 8.32mm, causing the length of travel to be reduced.  And the error is greater at speed changes.

In configuration of TO synchronous axis, I had allowed following error of upto 50mm, when I try to reduce it 5mm, servo following error continuously occurs. I guess it has something to do with tuning of servo drive. I tried the 1 button auto tuning as well as through TIA commissioning tool, but couldn’t reduce these limits.

Please comment and let me know if you need any further information.

Once again a load of thanks for helping out.