Motor Technologies Driving Modern Robotics: A Comprehensive Overview

Industrial robotics has seen significant advancements in motor technology, with permanent-magnet brushless servomotors becoming the dominant choice across various robot types. This article summarizes the key motor technologies powering different robotic systems and how they contribute to precision, performance, and versatility.

Key Motor Technologies in Modern Robotics

Permanent-magnet brushless servomotors have emerged as the leading motor technology in robotic applications over the past decade. Frameless and direct-drive variations are increasingly common in six-axis robotic assemblies, offering high torque output and low cogging through high motor pole counts combined with strain-wave gearing. These assemblies typically include absolute encoders for closed-loop position control and safety holding brakes.

For applications requiring zero-backlash operation, such as inspection and surgical robots, torque motors are used without gearing in direct-drive configurations. Field-oriented control with customized rotor geometry and windings allows for tailored behavior at different robot joints, with current to windings across a large magnetic airgap providing stiffness and torque density.

Motor Applications Across Robot Types

Different robot configurations require specific motor adaptations. In six-axis robots, wrist joint motors must be lightweight with low inertia to prevent vibration, often using frameless or pancake-type construction. SCARA robots typically integrate high-torque AC servomotors on rotary axes for quick acceleration, while vertical Z axes may use servomotor-driven screws or linear motors.

Recent years have seen a convergence between industrial and collaborative robots, with both increasingly using frameless motors in joints and implementing machine learning and AI for specialized functions. This convergence has also led to overlap in payload ratings between robot types.

Gearing Systems in Robotics

Robotic joints employ various gearing technologies to optimize performance:

• Strain-wave gearing and planetary gearing dominate most applications
• Cycloidal (also called Rotary Vector or RV) gearing is seeing increased adoption
• Proprietary systems like WITTENSTEIN’s Galaxie drive offer specialized solutions
• Emerging technologies like FluxWorks magnetic gearing use modulated magnetic fields for contactless force transmission

Typical gear ratios range from 50:1 to 200:1, though wrist joints may use lower ratios. These gearing systems significantly boost acceleration torque and power density—critical factors for cantilevered robot designs.

Specialized Applications

The article highlights how different components come together in miniature robotics, such as Chieftek Precision’s S0 arms that integrate custom frameless motors, strain-wave gearing, and dual-feedback systems to achieve high precision in a compact package.

For Cartesian robots, the approach differs significantly. While they may be more expensive for smaller workcells compared to SCARA robots, Cartesians excel in large workcells where customization to exact production requirements justifies the higher upfront costs with long-term efficiencies.

Conclusion

Motor technology continues to evolve as a critical component in robotic system design, with different applications demanding specific configurations of motors and gearing. The convergence of industrial and collaborative robots, coupled with advancements in AI integration, signals an exciting future for robotic motor systems that offer increasing precision, power density, and application-specific performance.