Kollmorgen

Decentralized Control Systems to the Rescue

Guest contributor,  Bob White, Kollmorgen

Less Cabling, Smaller controls cabinet, Less heat…wow, that’s all great stuff.  I can achieve this all with a decentralized solution? Absolutely – and even more! 

Decentralized Control Architecture means shifting the motion control drives from the crowded cabinets, and moving them near to the motors – out on the machine where the action is.  Immediately you can see that this can reduce the size of the controls cabinet, moving all of those drives out onto the machine – but how do I see these other advantages?

Decentralized ArchitectureIt’s not JUST about moving the drives out onto the machine, near or integrated with the motors, but also how you design your entire control system.  Think about a conventional Centralized Control Architecture – all of your drives, power supplies and other I/O are jammed into a large cabinet and cables are run to each motor – and since we are talking conventional, this likely means multiple cables (power and feedback for each motor). So in a decentralized solution, the motor, feedback and fieldbus communication needs to be run through a single cable, and the control architecture  allows communications to function over the fieldbus loop.

So thinking about it that way, with an 8 axis machine – Control cabinet 5 meters from the initial motor, and subsequent axes 3 meters apart – this adds up quickly to almost 250 meters of cabling (Power and Feedback) using a centralized approach.

Centralized vs Decentralized ImageImagine now – A decentralized solution, drives located within a meter of the motor they are driving – you cut cabling down to a mere 35 meters!  Do the math – an 86% reduction!  Throw in extended I/O and your savings jumps to almost 90%  SO – Point 1 – Substantially reduced cables cost – not just from the mere reduction in cable length, but in reduced costs associated form cable management trays and even the labor to run the cables.

But there’s more (or do I mean less).  Smaller cabinet, less electronics, means less heat to dissipate – electronics usually don’t like the heat, so they tend to get some cool air, provided by some nice air conditioning system.  Less heat, less need for an expensive air conditioning unit, AND less energy consumption.

One other element not so readily apparent with a good decentralized design – flexibility!  Designing with a decentralized drive architecture in mind from the start opens up new possibilities.  This allows more flexibility in modularization.  We’ll cover this modularization concept in a follow on blog topic next time…

All of these advantages help the OEM build a more efficient machine, with less components, reduction in assembly time, and more flexibility in design – improving the marketability of the machine.  End users enjoy the lower cost of ownership and increase reliability – and potentially space savings on their factory floor.

Decentralized Machine Vision

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CMA/Flodyne/Hydradyne is an authorized  Kollmorgen distributor in Illinois, Wisconsin, Iowa and Northern Indiana.In addition to distribution, we design and fabricate complete engineered systems, including hydraulic power units, electrical control panels, pneumatic panels & aluminum framing. Our advanced components and system solutions are found in a wide variety of industrial applications such as wind energy, solar energy, process control and more.

How to Calculate RMS Torque

Guest contributor: Hurley Gill, Kollmorgen

Question: How do I calculate RMS (Root Mean Square) Torque for a given axis motion profile in my application?

Answer:  Let’s take a look at the Root Mean Square (RMS) Torque and why it is important. Typically an axes’ motion profile is broken up into multiple segments, each segment is found to require a specific torque for a specific amount of time to complete the desired motion.  For example, this can include torque required to accelerate, traverse (against an external force and/or friction),  decelerate, and dwell.  Each of these segments affects the amount of heating the motor experiences and thus the equivalent steady state continuous requirement utilized to select the correct motor.  The RMS Torque calculation  considers not only the amount of torque, but also the duration of that torque (by segment).  Our example below illustrates how to calculate Trms of your motion profile.

The below motion profile would be broken up into eight (8) different segments, each with a required torque Tx and time tx.

Motion Profile with Segmentation

To calculate Trms, use this equation:
 RMS Torque Formula

Where T1 = torque required by and during segment 1, and t1 = time duration (t1-t0) of segment 1, etc..  Note the additional torque required by the motor to over come some external/thrust force (greater than friction alone) during segment 2, and the lack of this required torque  during the dwell segment 4 and 8.

Going back to the example motion profile above and the chart of that motion profile:

Motion Profile Table with Segmentation

Therefore, if you do the math – and we will spare you writing this into a very long equation, the result is:

Trms =  RMS Example   = 2.74 lb-ft or 3.715_Nm (1.35582_Nm/lb-ft.)

Conclusion:  We hope that this tutorial has helped you!  If you have questions about this or other calculations,  or any automation related problem you may be having, please contact the motion control and programming experts at CMA/Flodyne/Hydradyne.

cropped-cmafh-logo-with-tagline-caps.pngCMA/Flodyne/Hydradyne is an authorized  Kollmorgen distributor in Illinois, Wisconsin, Iowa and Northern Indiana.

In addition to distribution, we design and fabricate complete engineered systems, including hydraulic power units, electrical control panels, pneumatic panels & aluminum framing. Our advanced components and system solutions are found in a wide variety of industrial applications such as wind energy, solar energy, process control and more.