Performance Motion Devices' MC73110 is a compact 64-pin IC that accepts a torque or velocity command from an SPI or serial data stream. It also performs advanced functions such as sinusoidal commutation, digital torque control, and field oriented control.
A relatively new category of chip-based products is a true standout in the motor control device market
Intelligent Motor Controllers (IMC) are low-cost ICs that provide advanced control of multi-phase motors, most commonly brushless DC and three-phase induction motors.
“IMCs are different from ‘dumb’ motor control ICs in that they use advanced algorithms to squeeze the highest possible performance from a motor,” says Chuck Lewin, founder and vice president of engineering with Performance Motion Devices.
IMCs are a growing movement during an industry surge in green products that deliver high efficiency through intelligent algorithms. According to Lewin, motor controls are going green and becoming networked.
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Improving Energy Efficiency
“Optimally driving motors is tricky,” says Lewin. “It can’t always be accomplished using traditional techniques such as six-step commutation.”
As an alternative, Lewin suggests users to consider field oriented control or other techniques. The compute intensive approaches will require high speed microprocessors or digital signal processors (DSPs), but are better suited to deliver the exact magnetic field orientation for a given rotor angle, load and speed to optimize performance.
Buying Power
When it comes to selecting the appropriate motor control for an application, motor drive performance is regulated by factors such as power output, switching speed and availability of advanced control techniques such as field oriented control.
“Some of the lesser-known factors that may be very important in a given application are connectivity and programming,” adds Lewin. “Traditional networks for motion include serial and CANBus, but more recent entrants include USB, Ethernet, Ethercat and for a time, Firewire.”
Motion-specific networks tent to track PC-based network standards, so it’s important to not become consumed with the latest flash in the pan network scheme just because the PC world has adopted it. Lewin’s word of the wise, “Be sure that it will still be around in ten years.”
In regards to programming a motion drive or controller, consider whether it is important to be using standard language such as C/C++. While it is relatively rare in a motion world typically dominated by proprietary, vendor-specific languages, using standard language can offer major advantages in code reusability and vendor independence.
Control Costs
Reliable motor control systems technology have great potential to help control development costs, particularly in wide range applications where the machine is paid for by the use of consumables, or with the delivery of a manufactured part. After all, down time is lost money.
According to Lewin, three factors make for a reliable machine: reduced connections, simple software and an overdesigned system.
- Reduce Connections: “Consider a control card that integrates the motion controller and the amplifier onto a single card,” Lewin suggests.
- Simple Software: “The best approach is to have the architecture of the software match the architecture of the control problem itself,” he says. “Is it fundamentally distributed and flat? Is it fundamentally organized in clusters? Avoid the latest fancy software operating system and stick to the basics. Consider a standard programming language such as C/C++ rather than vendor specific language.”
- Overdesign The System: “Overdesign the system a bit, and be sure your servo parameters and system event timing work for all expected loads — and for machine mechanics both new and old," he explains.
Size & Speed
Lewin predicts that in the next five years, the two trends that will dominate motion control will be controller size and the use of high-speed, low-cost digital networks.
“Twenty years ago controls were typically five times the size of the motors they controlled,” Lewin recalls. “Today, the ratio is often less than one, with many motor controls significantly smaller than the motor itself. In the future the controls will take up a negligible amount of space, whether mounted on a card, in a module or attached to a motor.”
The location of the controls will also continue to matter less and less as low-cost, high-speed networks like Ethercat become increasingly popular. According to Lewin, “encoders and I/O signals will connect directly to the network and feed their signals anywhere withing the machine.”