• Different types of robots, such as this cobot arm, rely on different motors for precise motion. • Source: Adobe Stock Industrial six-axis robots often integrate frameless motors at their axes. • Over the past decade, permanent-magnet brushless servomotors have come to dominate. • Increasingly common in six-axis robotic assemblies are frameless and direct-drive variations. • A highmotorpole count (with strain-wave gearing) yields high torque output and low cogging. • Often completing such assemblies are an absolute encoder for closed-loop position control and a safety (normally closed) holding brake for safe power-off load holding.

Article Summaries:

  • Motor design is driving a shift in industrial robot performance. Over the last decade, permanent‑magnet brushless servomotors-often frameless or direct‑drive-have become standard in six‑axis arms, offering high torque density, low cogging, and closed‑loop control with absolute encoders and safety brakes. Lightweight, low‑inertia PM motors are now common in wrist joints, while SCARA robots use high‑torque AC servos on planar axes and linear drives on the Z axis. The convergence of articulated robots and cobots is fueled by frameless motors, machine‑learning‑enabled “physical AI,” and overlapping payload ratings. Gearing trends include strain‑wave, planetary, cycloidal, and emerging magnetic‑gearing technologies.
  • Industrial robots now rely almost exclusively on frameless, permanent‑magnet brushless servomotors. High‑pole, strain‑wave gearboxes give high torque and low cogging, while absolute encoders and safety brakes provide closed‑loop control and secure load holding. Direct‑drive motors are used in inspection, surgical and metrology arms where zero backlash is critical. Shoulder and elbow joints employ field‑oriented control with customized rotor geometry to match payload mass, whereas wrist joints use lightweight, low‑inertia PM AC servomotors-often axial‑flux or pancake designs-to maintain high torque density. SCARA robots similarly use high‑torque AC servos on planar axes and linear or screw drives on the Z axis. The trend toward frameless motors is blurring the line between articulated industrial robots and collaborative cobots, with both adopting AI‑enhanced, high‑payload, low‑speed operation and a growing variety of gearing (planetary, strain‑wave, cycloidal, and emerging magnetic‑gearing) to meet specific performance needs.

Sources: