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Foreward I was in elementary school when I built my rst motor, more than 50 years ago. We all built one back then, winding surplus telephone wire around nails to make the magnets for the rotor and stator (eld) of a very crude series-wound motor, or we'd use horseshoe magnets for the stator to build a crude direct current (DC) motor. Then we'd hook it up to a D cell battery or two—and it turned. Later, I had an electric train set and I could change the direction and speed using the "throttle". I didn't know then that motors would play such a large role in my engineering career. The rst practical electric motors, meaning they could do useful work, were demonstrated in the late 1830's. A hundred years later, thanks to the electrication of the world, electric motors were common in many applications including fans, drives for power machinery, power tools, and appliances. These motors were mostly brushed DC, universal (brushed), or induction motors (single- or three- phase) and typically had only two speeds—On or Off. Universal motors could have several speed settings by switching between different eld windings. Varying the applied voltage to DC and universal motors would also vary their speed, so a simple controller using a variable transformer could be used for speed control, as with my model train. The rst electronic speed controls for high volume applications were basically simple Triac-based phase controls for universal motors used in applications like power drills. The introduction of rechargeable NiCad batteries made possible the rst cordless power tools in the early 60's and brought with it pulse-width modulation (PWM) control for DC motors. In the mid 70's, I worked on a PWM control for a 12V trolling motor. We had to bring a horse tank into the lab so we could run the motor under load and keep it cool. Stepper motors, with their inherent position accuracy, were used in applications like printers and machine controls. These were often driven with a very simple bridge driver and series current-limiting resistor that improved the speed performance of the motor but dissipated 10 times (or more) the power than was delivered by the motor. PWM current mode drives for stepper motors were rst introduced in the late 70's. Since the 1980's the sophistication and performance of motor control has accelerated dramatically. The reduction in the cost of the electronics and materials, such as rare earth magnets, coupled with the push for higher performance and efciency has driven a wave of development. Higher efciency motors, like brushless direct current (BLDC) motors, have become commonplace, replacing brushed DC motors in power tools and induction motors in home appliances. Solutions using eld-oriented control (FOC) for BLDC drives and microstepping for stepper motors have become ubiquitous. The common element in these is that the electronics have become much more sophisticated to drive these improvements in efciency and performance. It's an exciting time to be involved in motor control. The advances are coming rapidly and the systems, like the camera gimbal used in drone photography, are demanding ever higher performance. The articles here represent the latest achievements in motor driving. By Tom Hopkins, STMicroelectronics 03 Tom Hopkins received his BSEE degree from Kansas State University in 1976 and an MBA from Arizona State University in 1983. After graduation from KSU, Tom started his career at Motorola Semiconductor where he worked as an IC design engineer and applications engineer. In 1981 Tom joined SGS (now STMicroelectronics) and has worked on automotive, industrial and computer peripheral applications specializing in power electronics. He has managed applications engineering groups focused on power conversion and motor control for more than 25 years. Tom has 25 patents in the areas of electronic circuits and power electronics. He has published more than 50 papers in internationally recognized conferences and magazines on a range of topics from a solar photovoltaic power system to motor control and drive.

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