Distributed vs Imbedded PC Controls


Thread Starter

Bob Close

Today's automation systems, using multiaxis mixtures of AC, DC and stepper motors, are often driven to PC controllers for faster and faster machine throughput as well as increased reliability and decreased installation costs.

I would like to know the group's feelings about the benefits of distributing the PID loop control out of the PC and into or nearby the amplifier and/or motor vs. using an integral ISA or PCI motion card in the computer itself.

Some of the issues are: reduced wiring lengths, EMI noise, processing loop time, cost of smart amplifiers vs. control boards, networking, Environmental conditions, trajectory planning time, programmability...

Some of the configurations are:
1. PCI/ISA/PC104/VME multiaxis motion cards with a single Processor providing PID and planning
2. PCI/ISA/PC104/VME multiaxis motion cards with a dsp on each axis for PID, and central
processor for planning
3. Stand alone multiaxis controllers
4. Smart Amplifiers, with digital PID filter and tuning, networked
5. Smart Motors with internal amps, networked
6. etc.

Bob Close
Executive V.P.
Precision MicroControl Corp
TELE 760-930-0101
FAX 760-930-0222
[email protected]

Ranjan Acharya

I have used various types of servo controllers such as ones from our hosts Control Technology (customised standalone controller), Delta Tau's PMAC (PC or VME) and Delta's TI505 or PROFIBUS-DP models.

Of the three that I just mentioned, if you want top of the line ultra-cool motion control that no on can comprehend try Delta Tau. If you want
straightforwards motion control, try the other two.

Note that the Delta only does motion, an attached PLC has to do the rest. For the other two, the Control Technology (at the time) had an Intel
micro-controller engine (it may have evolved since then) and the PMAC had a Motorola DSP engine (hence its superior power).


Curt Wuollet

Hi Bob

Both approaches have merit.

With the dsp approach the boards can be controlled with very low overhead and simple programming, but would best be matched to a particular hardware system, unless the user wants to dabble in dsp programming.

With a powerful host and simple boards, the same software could be used with widely varying hardware, for example the NIST EMC project has been used with steppers and servos, with little modification.

I think classic cost and engineering factors still apply, embedded for high volume, host based for custom and where flexibility is needed. This can be mitigated by providing very high level tools for the dsp programming and putting the general, reusable stuff on the host to find a happy medium. It's really different in the
automation world. In the embedded world, engineers sweat bullets to save a dollar. In this market, people gladly buy massive overkill if it's easy to use.