Over the last few years there have been a number of changes in the cost of technology that are impacting the motion control marketplace.
The first is the cost of microcontroller technology that is dedicated to electric motor applications. Up until recently, the Digital Signal Processor was the “de facto” standard for motor control. Not because it was the the ideal solution for motor control, but because it was the only processor with sufficient bandwidth to handle the analog input and output requirements representing 3 phase motor voltages and currents and math calculations needed to regulate the motor as needed.
Doing motor control is one of the toughest applications for a variety of reasons. The rate of change of motor data is 16 milleseconds at 60 hertz. If the motor has 3 phases that are staggered at 120 degrees from each other, then three channels of 12 bit analog waveform data are being monitored as inputs in order to control a motor and the information must be handled with absolute precision at 5 millesecond timing. That’s a lot of data before any control calculations are begun.
Recent generations of microcontrollers have emerged with the processing bandwidth, 50 megahertz processor speeds, 8 channel a/d and d/a, dedicated pulse width modulation channels for controlling power semiconductors, quadrature encoder inputs and even families with embedded network communications. The communications capability does not impact processing speed of the code dedicated to the motor regulation algorithms. This is because the communications are handled as interrupts and scheduled. Which is also a weakness with a DSP. DSP’s do not like to answer requests for information.
And the really good news is that some of the new processor technology is available at the $3 level at 10k pieces for controllers without communications. Processors with communications are typically in the $5 to $6 level for comparable volumes.
At the same time power semiconductor prices are declining. Power mosfets and IGBTs have dropped to half the price of five years ago. The performance specifications have improved as well. Typical peak currents are 200% of continuous rating. So the overall performance is excellent compared to the power semiconductors in the past.
Thermal management is also getting good attention. Some of the newer mosfets include thermal pads on both the top and bottom of the chip. This can potentially double the thermal performance of the fets in a motor control application.
The other big cost factor in motors and controls is the number of connectors needed. Brushless servos require power, hall effect sensors and feedback devices. This puts a huge cost burden on the system, sometimes as much as 10 to 20% of the total price. Which has lead to a significant number of motor, drive combinations which eliminate the cabling costs. The tradeoff is the overall peak torque, but for many applications, this is fine.
More choices, better prices mean more options for the motion control enthusiast.