Robotics Motor Families — Family Index

This note is a robotics-lens catalog of motor families — the specific product lines, form factors, and integration patterns that actually appear in fielded robots. It complements [[Engineering/Tier3/electric-motor-taxonomy]] (which covers the fundamental motor types — SCIM, PMSM, BLDC, SRM, stepper, linear, etc.) by focusing on the packaging conventions (frameless, servo, smart, pancake, hub, voice-coil, piezo) and the named product families a robot designer would actually order from.

1. At a glance — robotics actuators by application

Robotics rarely picks “a motor” in isolation; it picks an actuator bundle — motor + gear + bearing + encoder + brake + driver — sized to a workload class. The dominant classes:

Application	Workload signature	Typical bundle
Cobot / HRC joint	High torque density, low speed, back-drivable, torque-controlled	Frameless torque motor + harmonic drive + dual encoder + brake
Industrial 6-axis arm joint	High peak torque, repeatable, position-controlled	AC servo + RV cycloidal (base) or harmonic (wrist)
AGV / AMR wheel drive	Continuous duty, moderate speed, regenerative braking	BLDC hub or geared BLDC + planetary
Drone propulsion	Very high speed (5–30 kRPM), low torque, light	Outrunner BLDC + ESC, direct prop
Gripper / dexterous finger	Short stroke, high precision, torque-feedback	Coreless DC or slotless BLDC + worm/planetary + load cell
Surgical end-effector	Mid-precision, compact, sterilizable	Maxon EC / Faulhaber + small harmonic
Aerospace control surface	Linear stroke, fail-safe, high force	Servo + ball screw or EMA linear
Semi wafer-handling / lithography	Sub-µm, cleanroom, non-cogging	Direct-drive servo + linear motor + voice-coil + piezo fine-stage
Quadruped leg (quasi-direct-drive)	High bandwidth, impact-tolerant, back-drivable	Low-Kv outrunner + single-stage 6–9:1 planetary
Educational / hobby arm	Low cost, integrated, daisy-chained bus	Smart servo (Dynamixel, Hebi)

Cross-reference: [[Engineering/Tier3/electric-motor-taxonomy]] for the underlying machine theory; [[Engineering/Tier3/gears-taxonomy]] for the gearbox half of every bundle below.

2. Frameless torque motors — the modern cobot joint

A frameless motor is a rotor + stator pair shipped without housing, shaft, or bearings. The integrator supplies the joint housing, cross-roller bearing, hollow-shaft routing, encoder, brake, and (usually) a harmonic flexspline whose wave generator rides directly on the rotor bore. This packaging is the single biggest reason cobot joints became compact and torque-controllable in the 2010s.

Product families:

• Kollmorgen TBM and KBM series — TBM (torque, larger bore, OD 60–290 mm) and KBM (general frameless, OD 22–890 mm). TBM is the de-facto cobot standard; Universal Robots UR5/UR10/UR16e joints use TBM-class motors paired with Harmonic Drive CSF/SHF gearsets.
• Allied Motion Megaflux — high pole-count frameless, OD 75–500 mm, optimized for direct-drive turntables and large-bore joints.
• ETEL TML / TMK / TMB — Swiss precision (Heidenhain group); TMB is hollow-shaft direct-drive, TMK is torque-motor with integrated cooling, used in semiconductor stages and high-end medical robotics.
• Tecnotion QTL / QT / QTR / QTH — Dutch torque motor specialist (acquired by Tecnotion/Heidenhain); hollow-bore designs popular in machine-tool rotary tables and increasingly in cobot wrists.
• TQ Group Robodrive ILM — frameless ILM-25 to ILM-115 lineup. KUKA LBR iiwa and KUKA iisy joint modules use ILM motors. Robodrive ships pre-matched encoder + brake kits.
• Heidenhain ECN / ECI integrated absolute encoders — companion to all of the above; ECN 1123 / ECN 1023 are the joint-encoder standards for cobot torque modules.
• Parker BE / NEMA frameless, Moog Genesis — secondary suppliers in aerospace and defense robotics.

Robots that use frameless torque motor + harmonic joint modules: Universal Robots UR3e/UR5e/UR10e/UR16e/UR20/UR30; Franka Emika Panda (in-house frameless wrapped around Harmonic Drive CSD); KUKA LBR iiwa 7/14 and KUKA iisy; Doosan H-series and M-series; Techman TM5/TM12/TM14; Kassow Robots; Elite Robots CS-series; FairyTale (Han’s Robot) Elfin; AUBO i-series.

3. Servo motors — AC servo (with feedback) for industrial arms

The classic industrial-arm joint motor: a PMSM rotor + slotted stator inside a finned aluminum housing with a single shaft, integral encoder, and (usually) a holding brake. Sized in NEMA-frame steps or metric flange sizes (40/60/80/100/130/180 mm). Driven by a matched servo amplifier with current/velocity/position loops.

• Yaskawa Sigma-7 / Sigma-X — Σ-7 (7th-gen, 24-bit encoder, 0.05 mm·s tuning) and the newer Σ-X (Ethernet/MECHATROLINK-4); the canonical Japanese-arm servo (used in Yaskawa MOTOMAN GP/HC robots).
• Mitsubishi MR-J5 / MR-J4 — SSCNET III/H or CC-Link IE TSN; HG-KR / HG-SR / HG-JR motor pairings.
• Fanuc αi-B / αi series — proprietary, FANUC arm-internal; matched to FANUC drives (no third-party amp).
• Siemens SIMOTICS 1FK7 (synchronous) / 1FT7 (servo) / 1FG6 (geared) — SINAMICS S120 / S210 drive ecosystem.
• ABB MotiFlex e180 + IRB integrated servo — ABB arms use a custom motor pack matched to OmniCore / IRC5 drives.
• Kollmorgen AKM / AKM2G — NEMA-frame industrial servo (AKM1 to AKM8), pairs with AKD / AKD2G drives. Common in machine-builder retrofits.
• Beckhoff AM8000 / AM8800 stainless — EtherCAT-native; AM8800 is washdown / food-grade.
• Bosch Rexroth MS2N / MS2S — sercos III / Multi-Ethernet, paired with IndraDrive.
• B&R 8LSA / 8LSC — POWERLINK / openSAFETY, integrated with mapp Motion stack.
• Omron G5 / 1S — EtherCAT, popular in SCARA and pick-and-place.
• Lenze MD / m850 / i950 — German mid-market.
• SEW-EURODRIVE CMP / DRC-LBE — geared-servo with integrated VFD on the motor (decentralized drive).

Frame-size shorthand: a “100 mm flange” servo is roughly 1 kW continuous; a 130 mm flange is roughly 3 kW; a 180 mm flange is 5–7 kW. Cross-reference: [[Engineering/Tier3/electric-motor-taxonomy]] PMSM section.

4. Stepper motors

Open-loop position control by counting electrical phase advances. Bipolar hybrid (permanent-magnet + variable-reluctance combined) is the dominant flavor in robotics; 1.8° per full step (200 steps/rev) is standard, with microstepping down to 1/256.

Frame sizes (NEMA convention): NEMA 14 (35 mm), NEMA 17 (42 mm), NEMA 23 (57 mm), NEMA 24 (60 mm), NEMA 34 (86 mm), NEMA 42 (110 mm).

Vendors:

• Sanyo Denki SH / SM / PMM series — Japanese precision stepper, often closed-loop variants (SH2287 with encoder).
• Nanotec ST / PD-series — German; PD-series has integrated drive + encoder + CANopen on the motor.
• MOONS’ MS / MD-series — large Chinese-American supplier; sold widely under OEM relabels.
• Lin Engineering Silverpak — integrated stepper + driver.
• Anaheim Automation 23MD / 34MD — combined stepper + driver + controller modules.
• StepperOnline — budget, OEM-sourced, dominant in hobby/3D-printer space.
• Oriental Motor PKP / AZ series — AZ is closed-loop (αSTEP) stepper with absolute encoder, blurring the line with servo.
• Trinamic (now ADI/Maxim) TMC drivers — TMC2208 / TMC2209 / TMC2660 / TMC5160 silent-stepper chips with StealthChop (silent PWM) and StallGuard (sensorless homing) — ubiquitous in 3D printing and increasingly in low-cost robotics.

Steppers are still common in: SCARA Z-axis (low cost), lab automation, 3D-printer kinematics, low-end pick-and-place, and any “good enough” open-loop joint where back-EMF and audible noise are acceptable.

5. Brushless DC outrunner — drones, e-bikes, quadruped legs

An outrunner BLDC has the magnets on the outside (the can rotates around a stationary inner stator). This gives larger air-gap radius per unit volume — higher torque, lower Kv (RPM/volt), better cooling. The form factor that conquered drones, hoverboards, e-bikes, and quasi-direct-drive quadruped legs.

Drone propulsion:

• T-Motor (Tiger Motor) — F-series racing, U-series (U3, U5, U7, U8, U10, U11, U13, U15) for cinema and heavy-lift, MN-series for mapping.
• Hobbywing XRotor — propulsion + ESC matched sets.
• KDE Direct — large UAS, marine-tolerant.
• iFlight / RaceCraft / EMAX / BrotherHobby — FPV racing.
• Sunnysky / Cobra / MAD Components — mid-market.
• DJI in-house — Mavic, Inspire, Matrice motors are proprietary outrunners paired with the DJI ESC.

Quasi-direct-drive (QDD) legged robots:

• T-Motor AK-series (AK60, AK70, AK80, AK10-9) — the canonical low-cost QDD actuator with built-in driver and CAN interface; used in MIT Mini-Cheetah replicas and many research quadrupeds.
• CubeMars (sister brand to T-Motor) — RI series, AK upgrades.
• MJBots Moteus controller paired with custom outrunner — popular in research labs.
• Unitree A1 / Go1 / Go2 / B1 / B2 / H1 — Hangzhou Unitree in-house QDD with single-stage 6–9:1 planetary.
• Boston Dynamics Spot / Atlas Electric (2024+) — proprietary electric joints replacing earlier hydraulics.

E-bike / hub motors:

• Bafang BBS02 / BBSHD / M-series mid-drive, Bafang G-series hub.
• Tongsheng TSDZ2 — torque-sensing mid-drive popular for retrofits.
• Yamaha PWseries / Bosch Performance Line / Brose Drive / Shimano STEPS — OEM mid-drives.
• Hub-style geared (Bafang G310, MAC) and hub-style direct-drive (Crystalyte, Grin All-Axle, Leafmotor).

6. Coreless / slotless DC and BLDC — precision micro-motors

A coreless (or ironless) rotor is a self-supporting copper winding with no iron back-iron — zero cogging, very low inductance, very low electrical time constant, smooth low-speed motion. Slotless BLDC variants achieve the same with a brushless commutation. Typically 1 W to 100 W; diameters 4 mm to 40 mm.

• Maxon EC / RE / DCX / ECX — Swiss precision; EC (brushless slotless), RE (brushed coreless), DCX/ECX configurable. The reference choice for surgical handpieces, prosthetics, micro-CNC, and the da Vinci surgical wrist.
• Faulhaber CR / CRB / BX4 / BHx — German; coreless brushed (CR) and slotless brushless (BX4/BP4/BHx). The other half of the precision micro-motor market.
• Portescap Athlonix / Ultra EC — Swiss/US; coreless DC and slotless BLDC.
• Maxon DC-MAX — cost-reduced coreless line.
• Allied Motion / Pittman / ML-series — US precision DC + brushless.
• Namiki — Japanese miniature (sub-6 mm diameter) coreless, popular in haptic and capsule-endoscope motors.

These are the motors inside: surgical drills, dental handpieces, robotic finger phalanges, smart-glasses focus motors, infusion pumps, capsule endoscopes, and prosthetic hand fingers (Ottobock, Open Bionics Hero Arm, Esper Hand).

7. Disc / pancake motors

Short axial length, large radial diameter — packaged into a flat “pancake” or “disc” form. Two distinct lineages:

• Printed Motor Works (PMW) ServoDisc — the original printed-armature disc DC motor, invented by Henry Baudot in the 1950s and commercialized by PMI Motion (now PMW) in the 1960s. Flat copper armature etched like a PCB, axial-flux design, exceptionally high torque-to-inertia ratio. Still produced for legacy aerospace and high-dynamic test stands.
• Allied Motion PWM / Megaflux pancake, Kollmorgen RBE / KBM pancake-frame, Servotronix CDHD pancake — modern BLDC pancakes; same flat form factor but iron-cored slotted construction.

Robotics use: direct-drive turntables (lidar rotators — Velodyne VLP-16, Ouster OS1 use brushless pancake spinners), gimbal mounts (DJI Ronin, Freefly Movi), camera pan-tilts, and any application where axial length is starved.

8. Direct-drive (no gear) servo

When backlash and friction must be zero: skip the gearbox. The motor’s continuous torque has to match the load directly, which means large pole counts, large diameters, and active liquid or air cooling for sustained service.

• Yokogawa Dynaserv DR / DD — legacy Japanese DD servo, still used in semiconductor wafer-handling.
• ETEL TMB / TMK direct-drive — Swiss, used in lithography theta-stages and semiconductor metrology.
• Sanyo Denki RAB / RA-series — Japanese DD with hollow shaft.
• NSK MEGATORQUE PS / PN-series — bearing + motor integrated unit, used in semiconductor wafer-pre-aligners and PCB-AOI rotary stages.
• Kollmorgen DDR / DDL (direct-drive rotary / linear) — DDR-D series with optical encoder.
• Yaskawa Sigma-7F (DD), Mitsubishi TM-RB-series — DD variants of mainline servo product lines.

Direct-drive shines in: semiconductor wafer-prealign, lithography reticle stage, PCB-inspection rotary indexers, optical scanners, and high-end machine-tool rotary tables. Unsuitable for typical industrial robot arms (insufficient torque density at acceptable joint mass).

9. Linear motors

See [[Engineering/Tier3/electric-motor-taxonomy]] § Linear motors for the underlying ironcore / ironless / U-channel / tubular taxonomy. Robotics-specific deployments:

• Cartesian / gantry XY stages: ETEL LMS / LMA, Akribis AKM-series, Aerotech ALS / ANT-series, Bosch Rexroth MKK / MLS, Yaskawa SGLG/SGLF/SGLT, Parker LXR/MX-series. Used in laser cutting, additive manufacturing, electronics assembly, PCB inspection.
• Wafer handling and lithography: ASML EUV-stage uses custom planar-motor linear stages (Asielec / Tecnotion / ETEL underpinnings).
• Magnetic levitation conveyors: Beckhoff XPlanar, B&R ACOPOS 6D, Festo Multi-Carrier System, Rockwell iTRAK / MagneMover. These are linear-motor stators tiled into a 2D surface or 1D track with magnetically levitated/sliding carriers — used as flexible part-transport in pharma packaging and electronics assembly.

10. Voice-coil / moving-coil actuators

A voice-coil motor (VCM) is the simplest of all linear actuators: a cylindrical coil in a radial permanent-magnet field. Force is proportional to current with sub-microsecond electrical bandwidth. Short stroke (typically 1–50 mm), no commutation, no cogging.

• H2W Technologies — California-based; rotary and linear voice-coil, NCC-series.
• BEI Kimco (now Sensata Kimco) — voice-coil actuators for aerospace, optical, and laser positioning.
• Akribis VCM-series — Singaporean precision voice-coil.
• Geeplus / Moticont — UK / US mid-market voice-coil and solenoid hybrids.
• CTS / Thorlabs voice-coil mirrors — small fast-steering mirror modules.

Voice-coil is the actuator inside: hard-disk-drive head positioners (historically), smartphone-camera autofocus (the OIS / AF actuators are tiny VCMs by Mitsumi, Alps, LG Innotek), lithography focus servos, laser scan-mirror tip-tilt, haptic shakers, and high-bandwidth force-feedback joysticks.

11. Piezo motors and piezo positioners

Piezoelectric ceramics expand or contract under voltage (sub-nm resolution but tens of µm full stroke per element). Stacked or amplified into useful actuators. Non-magnetic, vacuum-compatible, self-locking when unpowered, very high stiffness, no lubrication.

Stick-slip / inertial-drive piezo motors:

• Physik Instrumente (PI) PiezoMike, N-470 NEXACT, N-310 NEXACT, NEXLINE N-216 / N-381 — German; mm-stroke with nm resolution.
• PiezoMotor LEGS / Piezo LEGS LL / LR / LT — Swedish; walking-piezo legs.
• Cedrat Technologies APA / SPA / SA — French; amplified piezo actuators with mechanical lever amplification.
• Newport Picomotor — pure resolution-grade fine-adjust for optics, ~30 nm/step.
• Thorlabs ELL-series Elliptec — resonant piezo rotary and linear, low cost.
• Smaract SLC / GDA / SMARPOD — German; ultra-high-precision piezo stages including 6-DOF parallel kinematics.

Use cases in robotics: semiconductor wafer-stepper fine stages, scanning-electron-microscope sample manipulators, MRI-compatible robotic biopsy needles (non-magnetic requirement), atomic-force-microscope cantilever scanners, fiber-optic alignment, micro-manipulators for IVF / single-cell injection.

12. Ultrasonic motors (USM)

A piezo ring generates a traveling or standing acoustic wave on a stator surface; friction couples the wave to a rotor disc. Compact, hollow-shaft, fast-start, holds position unpowered, no electromagnetic emissions.

• Shinsei USR-series — Japanese pioneer; USR30 / USR60 ring USMs.
• Canon EF-USM (Ring USM) — in every Canon EF-mount autofocus lens since 1987.
• Olympus OM / Zuiko USM, Nikon SWM (Silent Wave Motor) — competing camera-lens implementations.
• PI U-264 / U-521 Ultrasonic stage — piezo-resonant linear ultrasonic.
• HQTronix / Nanomotion HR / EDGE — Israeli; ceramic-finger USM for precision stages.

Robotics use: surgical drills (Stryker / Medtronic ultrasonic bone drills), MRI-safe end-effectors (ferromagnetic-free constraint), micro-positioners in vacuum.

13. Servomotor + harmonic / cycloidal pre-integrated modules

A growing share of the robotics market sells the entire actuator bundle — motor, gearbox, encoder, brake, driver, and bus interface — as one orderable unit. This drastically reduces system-integration effort.

• Maxon EC-i + GP/GS gearbox + ENX encoder + EPOS/IDX controller — Maxon’s “compact drive” stack assembled per-application from their catalog.
• Schunk LWA / SRH / EGI / ERH gripper modules — motor + gear + encoder + controller integrated into a flange-mountable joint or finger.
• Kinova actuator modules (KA-58 / KA-75 / KA-77 / KA-58+) — used in the Gen3 / Gen3 lite arms; brushless + harmonic + dual encoder + EtherCAT in one housing.
• Hebi Robotics X-series — X5-1, X5-4, X5-9, X8-3, X8-9, X8-16; integrated BLDC + harmonic + dual encoder + IMU + Ethernet. Sold as building blocks for research arms.
• TQ-Group / Robodrive RoboDrive ILM-mod — pre-matched ILM frameless + harmonic + encoder kits.
• Harmonic Drive FHA-mini, FHA-C-mini, FLA / FHA-C-U-series — Harmonic Drive LLC’s own integrated actuators (motor + their harmonic + encoder + bearing).
• Nabtesco RV-N actuator — Nabtesco’s RV cycloidal + servo + encoder integrated unit.
• CSD/CSF/CPL frameless kits (Harmonic Drive, Sumitomo, Spinea) — gearset-only kits sized to popular frameless torque motors.

14. Smart actuators / servo modules — daisy-chain bus

The educational, prototyping, and humanoid markets converged on smart servo modules: a single bus cable (RS-485, CAN, EtherCAT-P, or proprietary) chains many actuators, each with built-in driver, encoder, and microcontroller.

• Robotis Dynamixel — the genre-defining line. XL-series (XL320, XL330) for low-cost; XM-series (XM430, XM540) and XH-series (XH430, XH540, XH540-W) for serious work; XW-series (XW540, XW430) for waterproof; PRO and P series (M42-10, M54-40, H42-20, H54-100/H54-200) for high-torque humanoid use. Multi-turn variants extend operation beyond 360°. Used in TurtleBot, OpenManipulator, Robotis-OP3 humanoid, ROBOTIS DARWIN-OP, much of the ICRA / IROS demo scene.
• Hebi Robotics X-series — see § 13.
• Herkulex DRS-0101 / DRS-0201 / DRS-0401 / DRS-0602 — Dongbu Robot Korea; competitor to Dynamixel.
• HiTec D-series digital servos — D-845WP, D-940TW; hobby-grade but with metal gears and high torque.
• Lynxmotion SmartArm / SmartServo — kit-level smart servo.
• Lewansoul / Hiwonder LX-series, LSC-series — Chinese low-cost.
• STEADYWIN GIM / GIM-series — Chinese QDD with integrated CAN driver (popular in research-quad-projects).
• DJI RoboMaster M-series (M2006, M3508, M3510) — sold as drone/robomaster competition motors but increasingly used in research robots with the DJI C620 / C610 ESC.

15. Cobot-grade torque-controlled actuators

Cobots’ defining feature is reliable joint-torque measurement, which enables collision detection, compliance control, and human-safe operation. Torque is measured one of two ways:

• Motor-current estimation — joint torque is inferred from measured motor current via the torque constant (K_t) and the gearbox ratio. Cheap (no extra sensor) but compromised by friction and harmonic-flexspline hysteresis. UR uses this approach.
• Direct torque sensor — a strain-gauged or optical torque sensor on the joint output. Higher fidelity, used by Franka Emika (strain-gauged flexspline), KUKA LBR iiwa (cross-spring torque sensor), and the higher-end Doosan models.
• Series-elastic actuator (SEA) — a deliberate compliant element (torsion spring or rubber element) between motor and output, with position encoders on both sides; torque is computed from spring deflection. Rethink Robotics Sawyer / Baxter use SEAs. Trade-off: easy torque measurement and intrinsic compliance, at the cost of bandwidth.

Named cobot joints:

• Franka Emika Panda — 7 DOF, in-house torque-sensing joint module with strain-gauge flexspline.
• Universal Robots URe — Kollmorgen TBM + Harmonic CSD + dual encoder + current-based torque estimation.
• KUKA LBR iiwa 7 R800 / iiwa 14 R820 — Robodrive ILM + Harmonic CPL + cross-spring torque sensor.
• ABB YuMi IRB 14000 — dual 7-DOF; compact servos + harmonic + padding for inherent safety.
• Rethink Sawyer (legacy) — series-elastic joints throughout.
• Doosan H-series — Harmonic + frameless + current-based torque.

16. Hydraulic / pneumatic actuators (cross-reference, not motors)

Strictly outside the “motor” scope but unavoidable in any robotics actuator survey:

• Hydraulics — Boston Dynamics’ Atlas (original, 2013–2024) and BigDog used custom servo-hydraulic actuators with bent-axis piston pumps. Atlas Electric (2024+) transitioned the platform to electric joints, marking the end of mainstream hydraulic humanoids.
• Pneumatic artificial muscles (McKibben): Festo Fluidic Muscle DMSP / MAS-series; Shadow Robot Hand (early variants); SoftBank Robotics / Vincent Systems experimental hands. High force density, very compliant, hard to control precisely.
• Soft pneumatic actuators: Soft Robotics Inc. (food handling), Harvard Wyss research bots.

17. Servo-electric for surgical robotics

Strict size, EMI, sterilization, and reliability constraints push surgical robotics toward Swiss-precision micro-motors:

• da Vinci (Intuitive Surgical) — Maxon EC brushless + custom harmonic + bespoke encoder + cable-driven wrist articulation (the EndoWrist).
• CMR Surgical Versius — modular arms with Maxon-class brushless joints.
• Medtronic Hugo RAS — Faulhaber-class brushless + custom drive.
• Stryker Mako (orthopedic) — Kollmorgen / Maxon-class joints.
• Smith+Nephew CORI — high-precision brushless + harmonic.
• Auris Monarch (bronchoscopy) — Maxon-class small-frame brushless.

Common denominator: Maxon EC-i or Faulhaber BX4 motor + 1-stage harmonic or cycloidal + magnetic absolute encoder + ISO 13485 supply chain.

18. Robot-arm joint torque + speed quick-reference

Approximate peak joint torques for popular arms (J1 = base, J6/J7 = wrist):

Arm	DOF	Payload	Peak joint torque range (N·m)	Joint motor family
Universal Robots UR5e	6	5 kg	~28–150 (J1 strongest, J5/J6 ~28)	Kollmorgen TBM + Harmonic CSD
Universal Robots UR16e	6	16 kg	~56–330	TBM (larger frame) + Harmonic
Universal Robots UR20	6	20 kg	~80–500	TBM (largest) + Harmonic
Franka Emika Panda	7	3 kg	~12 (J1) down to ~12 (J7)	Custom frameless + Harmonic CSD + torque sensor
KUKA LBR iiwa 7 R800	7	7 kg	~176 (J1) to ~40 (J7)	Robodrive ILM + Harmonic + cross-spring torque sensor
KUKA LBR iiwa 14 R820	7	14 kg	~320 (J1) to ~40 (J7)	Robodrive ILM-larger + Harmonic
ABB IRB 1200	6	5–7 kg	~90–250 (industrial, not torque-controlled)	ABB servo + RV cycloidal (base) + Harmonic (wrist)
FANUC LR Mate 200iD	6	7 kg	~80–280	FANUC αi servo + RV + Harmonic
Yaskawa GP7 / GP12	6	7–12 kg	~150–400	Sigma servo + RV + Harmonic
Doosan H2017	6	20 kg	~250–700	Frameless + Harmonic CPL-larger

Rule of thumb: J1/J2 (base/shoulder) require 5–10× the J6/J7 (wrist) torque; pick gearbox and motor accordingly.

19. Selection heuristics

A working selection tree for “what actuator should I use for X?”:

• Cobot joint (human-safe, back-drivable, torque-controlled): frameless torque motor (Kollmorgen TBM, Robodrive ILM) + harmonic drive (Harmonic Drive CSF/CSD/SHD) + dual encoder (input + output) + brake. Driver does current sensing for torque estimation; add a strain-gauged or cross-spring torque sensor for fidelity.
• Industrial 6-axis arm — base + shoulder: AC servo (Yaskawa Σ, Mitsubishi MR-J5, FANUC αi) + RV cycloidal (Nabtesco RV-N) — high stiffness, high shock tolerance, 100+:1 ratios.
• Industrial 6-axis arm — wrist: AC servo + harmonic drive — compact, lightweight, low backlash.
• SCARA Z-axis: ball screw + AC servo or stepper; rotational θ axis = direct drive or low-ratio belt.
• Delta / parallel-kinematic pick-and-place: AC servo + low-ratio belt or direct drive — speed-dominated.
• Surgical wrist: Maxon EC-i or Faulhaber BX4 coreless/slotless + 1-stage harmonic or cycloidal + magnetic absolute encoder.
• Drone propulsion: outrunner BLDC + matched ESC; pick Kv to match prop pitch and battery voltage.
• Hobby quadruped leg or 3-DOF arm: Dynamixel XM/XH-series, or T-Motor AK-series for higher torque.
• Research quasi-direct-drive quadruped (Mini-Cheetah class): low-Kv outrunner (~100 Kv) + single-stage 6–9:1 planetary; controller = MJBots Moteus or T-Motor AK.
• AGV / AMR drive wheel: BLDC hub motor (200–2000 W) with integrated planetary, or PMSM + planetary gearbox; SCIM + VFD on heavy-duty industrial AGVs.
• Gripper finger / dexterous hand: coreless DC (Maxon RE 13/16/20) or slotless BLDC (Faulhaber BX4) + worm-and-spur or planetary + load cell at the tendon termination for torque feedback.
• Wafer-handling rotary stage: direct-drive servo (Kollmorgen DDR, ETEL TMB, NSK MEGATORQUE).
• Lithography focus servo: voice-coil (H2W, BEI Kimco) for coarse + piezo (PI NEXLINE) for fine.
• Atomic-force-microscope sample stage: piezo stack + flexure (PI P-561, Smaract SLC).
• MRI-safe robotic biopsy needle: piezo (PI NEXACT or PiezoMotor LEGS) or ultrasonic (Shinsei USR) — must be non-magnetic.
• Camera autofocus rotary head (LiDAR mirror, camera lens): Canon EF-USM-class ultrasonic, or pancake brushless for lidar spinning.
• Educational arm / classroom robot: Dynamixel XL330 / XM430 daisy-chained; ROS-supported via dynamixel_workbench.

20. Vendors quick-pick table

Application	Recommended part family / vendor
Cobot joint, 5–10 kg payload	Kollmorgen TBM + Harmonic Drive CSD/SHD
Cobot joint, 14+ kg payload, torque-controlled	Robodrive ILM + Harmonic Drive CPL + cross-spring torque sensor
Industrial-arm base joint, 10–50 kg payload	Yaskawa Σ-7 + Nabtesco RV-N
Industrial-arm wrist joint	Yaskawa Σ-7 + Harmonic Drive CSF
SCARA θ-axis	Mitsubishi MR-J5 + planetary 5:1
AGV drive wheel, 100–500 W	BLDC hub (Hangzhou Greendrive, Maxon EC-i + GP planetary)
Drone, 5” FPV racing	T-Motor F40 / F60 + Hobbywing ESC
Drone, cinema-class	T-Motor U7 / U11 / U13 + Alpha ESC
QDD quadruped leg	T-Motor AK-80 v9.1 / MJBots mj5208
Educational arm	Dynamixel XM430-W350
Research arm with integrated comms	Hebi X8-9
Surgical handpiece	Maxon EC-i 40 + GP gearbox + Maxon ENX encoder
Surgical wrist	Maxon EC-i 30 + 1-stage Harmonic Drive CSF-mini
Prosthetic finger	Maxon RE 13 + worm + load cell
Semi wafer rotary	NSK MEGATORQUE PS-series
Lithography θ-stage	ETEL TMB
Lithography focus servo	H2W NCM-series VCM + PI NEXLINE fine stage
MRI-safe biopsy actuator	PiezoMotor LEGS LR-series
Lidar mirror spinner	Allied Motion Megaflux pancake or Maxon EC-flat
Pan-tilt camera gimbal	DJI RoboMaster GM6020 + iFlight outrunner

21. Cross-references

• [[Robotics/motors-electric]] — Tier 2 overview of robotics motor types.
• [[Robotics/manipulator-design]] — joint layout, kinematics, and integration.
• [[Robotics/end-effectors]] — grippers, hands, and tool changers.
• [[Robotics/Tier3/motor-drive-electronics]] — ESCs, servo amps, gate drivers.
• [[Robotics/Tier3/sensor-families]] — encoders, torque sensors, IMUs.
• [[Engineering/Tier3/electric-motor-taxonomy]] — fundamental motor types (SCIM, PMSM, BLDC, SRM, stepper, linear).
• [[Engineering/Tier3/gears-taxonomy]] — harmonic, cycloidal, planetary, RV.

22. Citations

• Maxon Academy white papers and Maxon Motor Selection Guide (Maxon Group, Sachseln, CH).
• Kollmorgen Frameless Motor Selection Guide (Kollmorgen, Radford VA).
• Harmonic Drive LLC Engineering Handbook (Harmonic Drive Systems, Tokyo / Peabody MA).
• Nabtesco RV Reducer Catalog (Nabtesco Corporation, Tokyo).
• Robotis Dynamixel e-Manual (https://emanual.robotis.com).
• Universal Robots Service Manual (UR5e / UR10e / UR16e / UR20, Universal Robots A/S, Odense DK).
• Hebi Robotics X-Series Actuator Technical Reference (Hebi Robotics, Pittsburgh PA).
• Franka Emika Panda Datasheet and Joint Specifications (Franka Emika GmbH, Munich).
• KUKA LBR iiwa Specifications (KUKA AG, Augsburg).
• Krishnan, R., Electric Motor Drives: Modeling, Analysis, and Control, Prentice Hall, 2001.
• Lyshevski, S. E., Electromechanical Systems and Devices, CRC Press, 2008.
• Slotine, J.-J., and Li, W., Applied Nonlinear Control, Prentice Hall, 1991 (for SEA / torque-control theory).
• NEMA MG 1 Motors and Generators (https://www.nema.org/).