Hi,

I`m using Sinamics S110 with CU305PN controlling by S7-1200 over Profinet.

In user program Motion Control object TO_PositioningAxis (name "Axis_TO") used to control the drive and recieve actual values of current position and velocity. Everything works fine, except for one thing.

Then using a motion command move with preset velocity, drive moves, but the actual speed value in DB "Axis_TO" jumps between + - 10 mm/s from a set value. 

eg

then calling this function

drive moves, but in TO data block parameter "Axis_TO".ActualVelocity = 20.0 (-10.0) for a few seconds and then 40.0 (+10.0) for a seconds, then all repeats... The same thing happens if I using the motion command "MC_MoveAbsolute" and set velocity value, I recieve actual velocity value with +-10.0 mm/s deviation.

In the diagnostics window, motion status tab, current velocity field has a proper constant value.  But I need a constant actual speed value in my program to ensure proper operation of other devices.

Please help if anyone has faced such problem.

Thanks in advance!

actual and current values are not the same. Current is the setpoint, while actual is the actual. Your PLC does some calulation to drive the motor at current setpoint.
The problem may be:
- incorrect profile selection, acceleration deceleration, speed; your motor may not be able to follow at such set accleration. Use s-shape profile with correct acc/dec that your system with given inertia can accelerate/decelerate.
- the control loop, aka P-controller has too much gain (Kv). so it is oscillating.

Thanks for your reply!

I already thought about Kv, and I'll try to correct it when I get access to the equipment. Actually I made automatic controller setting adjustment of the drive in STARTER and accept calculated values, and I thought that this is enough. But I forgot about Kv in TIA. Tnak you.

I'm sorry I'm not very strong in drive configuration. Do you mean a mathematical calculation of acc/dcc rates and all dynamic parameters by the term "profile"? Or I can select the profile type in STARTER? If so, how this can be done?