We tend to focus on connectivity and sensors for the IoT, however there is a third element to what I call the “Edge Device Triad” that is just as important: actuators. Making things move with microcontrollers (MCUs) is a science in and of itself. For small size and low weight combined with decent mechanical power, designers are opting for brushless DC (BLDC) motors in many applications.
BLDC motor control is complex. There are numerous variables and approaches to deliver precise motion with efficiency. Fortunately, an ultra-low-power ARM processor core such as a Cortex-M0+ provides enough computational power to run advanced algorithms, and there are many Cortex-M0+ MCUs out there. The question for how good an MCU is at BLDC motor control comes down to how capable its integrated peripherals are, and how well performance can be visualized and optimized.
Low power motor control isn’t just a nice thing to have – in some areas, regulation is moving in. I was recently at the IEEE Electronic Design Process Symposium in Monterey, and one of the examples cited was Japan’s Top Runner program. There are Top Runner energy consumption reports on every type of major home appliance and many smaller appliances. We were discussing printers, and that report calls for an efficiency improvement for devices shipped in FY2017 of 41.6% compared to the FY2007 baseline.
Printers are just one application for BLDC motors. Many other common devices are turning to BLDC motor implementations, such as handheld power tools, personal appliances including shavers and toothbrushes, robotic vacuums, drones and remote control toys, low-voltage pumps, and more. Often these devices are battery powered, with recharging or battery replacement requirements a key metric in usability and overall customer satisfaction.
Not all of us are motion control experts. Finding the right combination of pieces to quickly execute a BLDC motor control design can be challenging. Atmel, a wholly owned subsidiary of Microchip Technology Inc., has been at work kitting the pieces needed, starting with their SAMD21 MCU. We first covered this part about two years ago (in my blog “What’s not quite MCU, and not quite SoC?”), noting the high speed bus matrix and the deep roster of peripherals. The timer blocks support dead-time insertion and complimentary outputs needed for motor drive. The analog subsystem integrates accurate internal references for precision. A unique feature, the Atmel Event System, focuses on real-time reaction to events without imposing CPU interrupts.
The SAMD21 is at the center of the new ATSAMD21BLDC24V-STK platform, pictured above. The kit hardware includes the MCU board, a 24V motor driver board, an AC/DC adapter for power, and a small BLDC motor.
Software support for the ATSAMD21BDLC24V-STK is what takes the complexity away for designers. Atmel Studio comprehends the hardware for development and debug. Within the Atmel START and Atmel Software Framework are example projects dedicated to BLDC motor control. Full source code is provided for sensorless field-oriented control (FOC) and sensored block commutation, so developers can pull the kit out of the box and start talking to a motor. The Atmel Data Visualizer lets users control motor speed and direction while monitoring speed and power consumption via a GUI.
Atmel is extending this motor control kit concept to other family members soon, including the SAMC21 and SAMD21L. They are also working on additional motor control algorithms, and a new high-voltage motor control interface with up to 400V drive capability. Atmel currently supports safety requirements with a certified IEC 60730 Class B library.
We’ve been discussing the trend away from “just chips” (although those are really important) and toward more system-centric design enablement. We expect this to become table stakes, where MCU and SoC vendors will have to assemble and optimize hardware/software combinations for specific vertical applications to secure design-ins. It’s good to see Atmel supporting this part of my Edge Device Triad helping make actuators more efficient. Power savings add up quickly when scaled across millions of devices, and designers are well-served to be proactive in lowering power consumption.
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