Motion Is in the Cards at PMD

View Prodigy Motion Cards at a Glance!
In a bid to make distributed motion controlsystems easier to implement and more cost effective, PerformanceMotion Devices (PMD) has come out with a new line of motion controlcards that run their own motion programs without the need for a host computer.

These ProdigyMotion Cards feature an onboard code-execution module that PMD hasdubbed the "C-Motion Engine."The module stores and independently executes downloadable motion controlprograms created in PMD's C-Motion, an integrated development environment basedon C/C++ programming. Aside from the motion control functions, the C-MotionEngine can also manage digital and analog I/O signals.

The cards come in three different versions. Tworetain a bus connection - either PCI or PC/104. A third version is a stand-alonecard. All three support Ethernet, CANbus and serial communications.

And thanks to those communications supports, allthree can still talk to to host computer. Only now, the host computer's role isrelegated to sending high-level commands to the motion cards and runningancillary software. "The idea here is to offload the motion processingfrom the host and put the real-time motion tasks on a real-time platform,"says Chuck Lewin, the company's founder and vice president of engineering.

The cards enable distributed motion controlarchitectures that address some "classic motion control problems,"says Lewin.

One is how to handle the motion on machinesconsisting of multiple stations or cells. With a distributed architecture basedon standalone Prodigy motion cards, each cell can run its own motion program,while a supervisory computer sends the commands that coordinate the actions ofthe cells. "It's a good way to divvy up a big, complex motion probleminto manageable pieces," Lewin says.

Another is how to sync motion systems with theperipherals they move - such as print heads or optical devices. Lewin says systems with locallyexecuted motion code and I/O management can often achieve a faster overallresponse than systems whose motion code runs on host computers that devote someof their processing power to non-real-time tasks.

While the standalone Prodigy card is oneobvious choice for distributed applications, the bus-connected card can fit into distributed architectures too. According to Lewin, the bus connections offer the ability to createmaster-slave configurations consisting of multiple motion cards or to integratecards physically into industrial computers.

PMD's take on distributed motion architectureswill likely have cost implications. The company is selling the cards for $575.And Lewin says the card price doesn't tell the whole coststory. "There are obvious savingswhen you replace computers and I/O cards with a single motion card," hesays.

Like the company's previous cards, Prodigy'smotion processing muscle still comes from PMD's Magellan Motion Processor,which has a servo loop rate of 50 mus/axis. It offers a variety of motion modes,including S-curve, trapezoidal, velocity contouring and electronic gearing,while its servo loop compensation utilizes a full 32-bit position error, PIDwith velocity and acceleration feed forward, integration limit and dual biquadfilters.