A ROTARY ACTUATOR?

Pneumatics and hydraulics have been the mainstays of American industrial control systems from the start of our industrial revolution; but in the last 20 years, there’s a “new kid on the block”, Brushless Direct Current (BLDC) motors and their direct drive capability.

Perhaps, it’s not really all that new. Thomas Edison recognized the controllability of the direct current (D/C) electric motor compared to that of Tesla’s alternating current (A/C) synchronous concept. Unfortunately, the performance of the Brushless DC motor with early permanent magnets often fell short in many of the applications which were attempted. Today’s BLDC motors, with their digital electronics, meld into the Internet of Things (IoT) and Industry 4.0 with remarkable ease. BLDC motors are a driving force behind the move to direct drive, compact systems and efficiency in terms of size, weight and power consumption.

The keyword in this whole discussion is “Brushless”. Edison’s Bipolar D/C motor from the start of the 20th Century had been the basis of design for 50 years. Its sparking wire-wrapped coils, the mechanical and electrical noise they generated, and the perpetual maintenance of worn down brushes and glazed commutators relegated first-cut design D/C motors to intermittent duty service. Meanwhile, Tesla’s A/C approach won the continuous duty market.

Fast forward to today. The modern BLDC device can be much more that a simple motor; it is becoming a rotary actuator. Design iterations on BLDC actuators and enhancements in Permanent Magnets have allowed new capabilities which promote direct electrical coupling to IoT systems, eliminating cumbersome single purpose pneumatic and hydraulic controllers, or even pullies and long drive shafts in continuous duty service.

New BLDC actuators are also capable of being an integral part of smart system management control. Sensors on the actuator can feed data back to a conveniently located digital controller about speed, direction, and position. Needed corrections are then fed back to the controller maintaining the actuator. The inherent flexibility of electronic control has opened new uses for BLDC motor resulting in true integrated solutions.

Modern BLDC actuators offer designers an efficient and powerful digital device, not simply a mechanical one. Therefore, changing a motion parameter doesn’t require a mechanical adjustment, but merely a digital input. The integrated BLDC motor, through its control electronics, can be easily programmed to perform its required motions and even feedback to correct the inputs.

BLDC motor concepts open system design opportunities which can utilize the new direct drive motion capabilities. In contrast to the more dominant Slotted BLDC designs, where the stator is a toothed iron with wire wrappings around each tooth, whereby creating the areas of electronic-induced magnet flux, Slotless BLDC motors have a uniform coil wrapping architecture, whereby eliminating the teeth and related over concentration of wire wrappings. This allows for smooth motion and eliminates the “cogging” associated with Slotted designs. Add in other techniques whereby the airgap between the stator and permanent magnet-rotor is minimized and the placement techniques of the magnets is optimized, all these yield a much more compact, yet efficient and powerful design actuating solution.

ThinGap, Inc. (Camarillo, CA) is a pace setter in the design of system-integrated rotary actuators, frameless motor kits, if you prefer. ThinGap’s slotless architecture provides a high performance motor kit that OEM’s then integrate directly into their system, in contrast to simply bolting on a framed motor. ThinGap’s range of frameless motor solutions all provide high torque and low-inertia, with Zero-Cogging for smooth motion, while being lightweight with high efficiency, all within a low profile with a large through-hole.

Added aspects of ThinGap’s designs include ultra-low torque ripple when paired with a sinusoidal drive, 3-phase brushless, sinusoidal waveforms < 1% THD, high peak torque-to-continuous torque ratio, non-saturating structure allows high peak torque (typically > 4:1), a large clear apertures; the aforementioned frameless kit facilitates deep integration, in many cases space and MIL-STD qualified, optional rotor hubs for deeper integration, and are made in the USA.

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