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Old November 20th, 2023, 06:15 PM   #1

aand74 is offline
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Positioning in Beckhoff compared to Siemens

The system of position control is quite different in Beckhoff compared to Siemens.
In a Beckhoff controller with Beckhoff drives on Ethercat, the CSP profile transmits each cycle the position to the drive. The drive interpolates and generates a velocity from that position signal.
In siemens with drives on Profinet, when DSC is used, a velocity signal is sent to the drive as velocity precontrol and a position error is sent to the drive for positon control in the drive.
Does someone knows the pro's and con's of both system?
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Old November 21st, 2023, 12:10 AM   #2
Peter Nachtwey
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I am a motion control expert, but I have NO IDEA what CSP or DCS is. I don't keep up with acronyms that other manufacturers make up. I am a purist. I am not a fan of systems that download just the positions every millisecond. This forces the motion controller or drive to calculate the target velocity and acceleration from just the positions. This requires fine position feedback and data that is time stamped or is acquired at CONSTANT intervals. Mathematically they should be equivalent but then there are implementation details.

Downloading velocities every millisecond means one only needs to differentiate once to get the acceleration.

The target velocity and acceleration are necessary for calculating the velocity and acceleration feedforwards.

If I were designing these systems, I would have the master download the jerk each millisecond. The jerk can then be integrated by the drive to generate target acceleration, velocity, and positions.

I thought that Ethercat could download more information at a time since the packet size is no longer to the CAN Open packet size.
"Living is easy with eyes closed, misunderstanding all you see...." Strawberry Fields Forever, John Lennon
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Old November 21st, 2023, 09:28 AM   #3
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CSP = Cyclic Synchronous Position

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