Robot Actuators: Which Robot Uses What Actuator?

Last updated 2025-07-01. Written by Firgelli Robots Editorial Team. Reviewed by Robbie Dickson.

What Is a Robot Actuator?

A robot actuator is the component that converts electrical, hydraulic, pneumatic or other energy into physical movement. In humanoid robots, actuators drive joints such as shoulders, elbows, wrists, fingers, hips, knees, ankles, necks and sometimes torso joints. Learn more about what actuators are and how they work in the FIRGELLI actuator guide.

Actuators are one of the most important parts of any humanoid robot because they determine strength, speed, precision, balance, dexterity, safety, cost, noise, efficiency, reliability, repairability and battery runtime.

Why Actuators Matter in Humanoid Robots

A humanoid robot can only walk, lift, grasp and recover from disturbances if its actuators can deliver the right torque at the right speed without overheating or becoming unsafe around people. The same robot body can feel completely different depending on actuator choices: a stiff high-ratio joint may be precise but less forgiving; a quasi-direct-drive joint may be more backdrivable but harder to package; a tendon-driven hand may be light and expressive but more complex to maintain.

• Walking and balance depend on hip, knee and ankle torque, control bandwidth and impact tolerance.
• Manipulation depends on shoulder, elbow, wrist, finger and grip actuator precision.
• Payload depends on continuous torque, thermal limits and the geometry of the arm.
• Speed depends on motor power, gear ratio, controller bandwidth and safe stopping behavior.
• Safety depends on force sensing, torque limits, compliance, brakes, software limits and mechanical design.
• Cost depends heavily on motors, precision gearboxes, encoders, bearings, sensors and custom electronics.

Main Types of Robot Actuators

Robot Actuator Comparison Table

Robot	Manufacturer	Robot type	Actuator type	Supplier / maker	Actuator count	DOF	Joint locations	Torque	Confidence	Notes
Tesla Optimus	Tesla	Humanoid	Custom electric joint actuators are reported from public demos; current production details not fully published	Tesla / in-house reported	Not publicly disclosed	28 reported by secondary listing; Tesla has not published a stable current DOF table	Major body joints and hands	Not publicly disclosed	Reported / not fully public	Tesla's current AI page describes the bipedal robot program but does not publish a stable actuator table.
Figure 02	Figure AI	Humanoid	Electric humanoid actuators; detailed supplier and torque data not public	Not publicly disclosed	Unknown	35 reported in KB	Legs, arms, hands, torso/head	Unknown	Unknown	Treat supplier claims as unconfirmed unless Figure publishes them.
Unitree G1	Unitree Robotics	Humanoid	Electric rotary joint motors with PMSM core joint motors	Unitree	23 to 43 joint motors	23 to 43	Legs, waist, arms, optional hands/wrists	90 N.m knee, 120 N.m G1 EDU knee	Verified official	Unitree publishes motor, torque, encoder, cooling and power details.
Unitree H1	Unitree Robotics	Humanoid	Electric M107 joint motor architecture	Unitree	Not separately stated	H1-2: 27	Legs, arms, waist	Up to 360 N.m leg joint torque	Verified official	Unitree publishes maximum joint torque, motor type and torque-density claims.
Unitree H2	Unitree Robotics	Humanoid	Electric humanoid joint system; detailed actuator table limited	Unitree	Unknown	31 in KB	Humanoid joints	Unknown	Reported / developing	Use official H2 page for current configuration; supplier is Unitree in-house unless otherwise disclosed.
Unitree R1	Unitree Robotics	Humanoid	Electric humanoid joint system; detailed actuator table limited	Unitree	Unknown	26 in KB	Humanoid joints	Unknown	Reported / developing	Detailed motor specs are not yet as public as G1/H1.
Apptronik Apollo	Apptronik	Humanoid	Electric humanoid joint system; modular robot architecture	Not publicly disclosed	Unknown	30 in KB	Legs/arms depending configuration	Unknown	Official robot specs, actuator details undisclosed	Apollo public page emphasizes modularity, payload, runtime and safety more than actuator internals.
NEO	1X Technologies	Humanoid	1X Tendon Drive / tendon-driven electric actuation	1X	Unknown	75 in KB	Body and hands	Unknown	Strongly supported	1X publicly brands NEO around its tendon-drive approach, but granular motor specs remain limited.
EVE	1X Technologies	Wheeled humanoid	Electric actuation, supplier not publicly disclosed	Not publicly disclosed	Unknown	Unknown	Arms, torso/head, wheeled base	Unknown	Unknown	Included because it is important to 1X's actuator progression, but public actuator details are sparse.
Phoenix	Sanctuary AI	Humanoid	Electric humanoid actuation publicly implied; detailed supplier not public	Not publicly disclosed	Unknown	20 in KB	Upper body and mobile base/system joints	Unknown	Unknown	Sanctuary publishes robot positioning more than actuator specifications.
Digit	Agility Robotics	Humanoid	Electric bipedal robot actuation	Not publicly disclosed	Unknown	4	Legs, arms, end effectors	Unknown	Official product, actuator details undisclosed	Agility publishes deployment capability and payload/runtime data, not a joint-module bill of materials.
Atlas	Boston Dynamics	Humanoid	New Atlas is all-electric; earlier Atlas generations used hydraulic actuation	Boston Dynamics / in-house	Unknown	56	Full humanoid body	Unknown	Verified official for electric Atlas	Boston Dynamics states the commercial Atlas path begins with an all-electric Atlas.
Walker S	UBTECH Robotics	Humanoid	Electric humanoid joint actuation; supplier not public	Not publicly disclosed	Unknown	41	Humanoid body	Unknown	Reported / official robot specs	Force/torque sensing is listed in the KB, but actuator supplier is not disclosed.
Walker X	UBTECH Robotics	Humanoid	Electric humanoid joint actuation; supplier not public	Not publicly disclosed	Unknown	41 reported	Humanoid body	Unknown	Reported	Treat detailed actuator data as not public.
GR-1	Fourier Intelligence	Humanoid	Electric humanoid actuators; details limited in public spec summaries	Fourier / not publicly disclosed	Unknown	Unknown	Humanoid body	Unknown	Reported	Included as a Fourier humanoid platform; verify specific joint module details before procurement use.
GR-2	Fourier Intelligence	Humanoid	Electric humanoid actuators; details limited publicly	Fourier / not publicly disclosed	Unknown	53	Humanoid body and hands	Unknown	Reported / official product page	Public specs prioritize payload, DOF and application rather than supplier-level actuator details.
Agibot A2	Agibot	Humanoid	Electric humanoid actuators; public supplier data limited	Not publicly disclosed	Unknown	49+	Humanoid body	Unknown	Reported	Treat supplier claims as unverified.
Astribot S1	Astribot	Upper-body humanoid	High-speed electric manipulation actuators; detailed specs not public	Not publicly disclosed	Unknown	14 in KB	Arms, hands, torso/head	Unknown	Reported / demo-based	Known mainly from public demos rather than a full public actuator table.
PUDU D9	Pudu Robotics	Humanoid	Electric bipedal humanoid actuation plus PUDU DH11 dexterous hands	Pudu	Unknown	42	Legs, arms, DH11 hands	352 N.m maximum joint torque	Verified official	Pudu publishes DOF, max joint torque and hand motor/DOF details.
Pudu D7	Pudu Robotics	Semi-humanoid / service robot	Electric mobile/service robot actuation; detailed actuator specs limited	Pudu / not publicly disclosed	Unknown	30 in KB	Arms/body/mobile base	Unknown	Reported	Included as part of Pudu's robot lineup, not a full biped humanoid actuator reference.
CyberOne	Xiaomi	Humanoid prototype	Electric humanoid actuation; detailed supplier not public	Not publicly disclosed	Unknown	21	Humanoid joints	Unknown	Official robot announcement, limited actuator detail	Xiaomi disclosed humanoid concept/spec data but not supplier-level joint-module details.
PX5	XPeng	Humanoid	Electric humanoid actuation; details limited	Not publicly disclosed	Unknown	22 in KB	Humanoid joints	Unknown	Reported	Supplier claims should be treated as unconfirmed.
PM01	EngineAI	Humanoid	Electric humanoid actuation; details limited	Not publicly disclosed	Unknown	Unknown	Humanoid joints	Unknown	Reported	Public information is mostly product positioning and demos.
Kepler Forerunner	Kepler Robotics	Humanoid	Electric humanoid actuation; details limited	Not publicly disclosed	Unknown	40	Humanoid joints	Unknown	Reported	Detailed supplier and torque tables are not publicly established.
Menteebot	Mentee Robotics	Humanoid	Electric humanoid actuation; details limited	Not publicly disclosed	Unknown	40	Humanoid joints	Unknown	Reported	Public actuator bill of materials not found.
Ameca	Engineered Arts	Humanoid bust / social robot	Electric animatronic servo actuation	Engineered Arts / not publicly disclosed	Unknown	Unknown	Face, head, neck, arms/hands depending version	Unknown	Reported	Not a walking humanoid; included for expressive actuator design.
Pepper	SoftBank Robotics	Wheeled humanoid	Electric servo/motor actuation	SoftBank/Aldebaran, supplier not public	20 moving parts/motors reported	20 moving parts / motors	Head, arms, hands, mobile base	Unknown	Reported	Pepper is a social robot, not a high-torque biped.
NAO	Aldebaran	Small humanoid	Electric servo/motor actuation	Aldebaran/SoftBank, supplier not public	Unknown	25	Whole body small humanoid joints	Unknown	Reported	Good example of low-payload educational humanoid actuation.
ASIMO	Honda	Humanoid research robot	Electric servo actuation	Honda / in-house	Unknown	57	Whole body	Unknown	Historical / official robot	Honda's public ASIMO pages are historical and do not expose modern supplier tables.
Valkyrie	NASA	Humanoid research robot	Electric rotary elastic actuators reported in research context	NASA / partners	Unknown	44	Whole body	Unknown	Reported / research	Use NASA and research papers for detailed configuration; not a commercial product spec.
TALOS	PAL Robotics	Humanoid research robot	Electric torque-controlled joints with joint torque sensors	PAL Robotics / not publicly disclosed	Unknown	Unknown	Whole body except some head/wrist/gripper exceptions	Unknown	Verified official for torque sensing	PAL states torque sensor feedback in all joints except head, wrists and grippers.
REEM-C	PAL Robotics	Humanoid research robot	Electric biped humanoid actuation with ankle/wrist torque sensors	PAL Robotics / not publicly disclosed	Unknown	68	Whole body, ankles/wrists torque sensing	Unknown	Verified official	PAL publishes 68 DoF and torque sensors in ankles and wrists.
HRP-4	Kawada Robotics	Humanoid research robot	Electric humanoid research actuators; detailed current supplier info limited	Kawada/AIST ecosystem	Unknown	34	Whole body	Unknown	Historical / reported	Older research platform; verify via papers for engineering reuse.
HRP-5P	Kawada Robotics / AIST	Humanoid research robot	Electric humanoid research actuators; supplier details not public in site data	Kawada/AIST ecosystem	Unknown	37	Whole body	Unknown	Official research announcement / reported	Included as a construction-research humanoid reference.
T-HR3	Toyota	Humanoid research robot	Electric torque-servo humanoid control architecture	Toyota / in-house	Unknown	Unknown	Whole body with master maneuvering system	Unknown	Official product history, limited actuator table	Actuator supplier-level details are not public.
iCub	IIT	Humanoid research robot	Electric motors with tendon/cable-driven hands and compact joints	IIT / mixed research supply chain	Unknown	53	Whole body, hands	Unknown	Reported / research	Use official iCub docs and papers before treating supplier data as fixed.
ARMAR-6	KIT	Humanoid research robot	Electric research humanoid actuation; details vary by subsystem	KIT / research supply chain	Unknown	Unknown	Whole body	Unknown	Reported / research	Public project data is more about system capability than supplier identity.
ROBOTIS OP3	ROBOTIS	Small humanoid	ROBOTIS DYNAMIXEL XM430-W350-R smart servos	ROBOTIS	20 actuators / DOF	20	All small humanoid joints	4.1 N.m stall torque listed for XM430-W350	Verified official	ROBOTIS publishes actuator model, gear ratio, torque, current and DOF.
Poppy Humanoid	Poppy Project	Small open-source humanoid	ROBOTIS / DYNAMIXEL smart servo actuators	ROBOTIS	25 actuators listed in KB	25 actuators	Whole body	Varies by selected Dynamixel model	Verified from KB/source-backed project data	Good educational reference for modular servo-actuator humanoids.
YuMi	ABB	Dual-arm collaborative robot	Industrial electric servo joints	ABB / in-house industrial robotics	14 axes total	14	Two 7-axis arms	Unknown	Official product family, supplier not public	Not humanoid; included because it is a key collaborative arm actuation reference.
LBR iiwa	KUKA	Collaborative robot arm	Industrial electric servo joints with joint torque sensors	KUKA	7 axes	7	Seven robot axes	Axis-specific torque accuracy +/-2% of max torque	Verified official	KUKA publishes torque-sensor and 7-axis collaborative-robot data.
Franka Research 3	Franka Robotics	Research robot arm	Seven integrated electric joints with torque sensors	Franka Robotics	7 actuators minimum	7	7-axis arm	Torque sensors in each joint; exact actuator torque table not in public page	Verified official	Franka publishes 7 DoF, 7 integrated torque sensors and 1 kHz control access.
Spot	Boston Dynamics	Quadruped	Electric quadruped actuators	Boston Dynamics / in-house	Unknown	Unknown	Four legs plus optional arm	Unknown	Official product, actuator details not public	Included as a non-humanoid benchmark for compact legged actuation.
ANYmal	ANYbotics	Quadruped	Electric legged-robot actuation; detailed actuator module not fully public	ANYbotics / not publicly disclosed	Unknown	Unknown	Four legs, inspection payload pan-tilt	Unknown	Official product, actuator details limited	Included because industrial quadrupeds are relevant to legged actuator design.

Which Actuators Does Each Robot Use?

The sections below separate true humanoids from robot arms and quadrupeds. Non-humanoid robots are included because they are important examples of robotic actuation, but they should not be treated as humanoid robot specifications.

Tesla Optimus Actuators

Tesla - Tesla's official AI page describes Optimus as a bipedal autonomous humanoid for unsafe, repetitive or boring tasks. Tesla has shown custom joint work publicly, but a current production actuator specification table is not published.

Sources: Tesla AI

Figure 02 Actuators

Figure AI - Figure's current public site now focuses on Figure 03 and Helix, while the Firgelli Robots KB still tracks Figure 01 and Figure 02 pages. Figure has not published a full actuator supplier table for Figure 02.

Sources: Figure

Unitree G1 Actuators

Unitree Robotics - Unitree G1 is one of the clearest public actuator references because the official page lists joint motor type, DOF, torque, encoders, cooling and power information.

Sources: Unitree G1

Unitree H1 Actuators

Unitree Robotics - Unitree H1/H1-2 extends the company's in-house electric joint motor approach into a full-size humanoid platform.

Sources: Unitree H1

Apptronik Apollo Actuators

Apptronik - Apollo's public page positions the robot for warehouses and manufacturing, with modular design, hot-swappable batteries, payload and safety details. It does not publish supplier-level actuator internals.

Sources: Apptronik Apollo

NEO Actuators

1X Technologies - NEO is important because 1X emphasizes tendon-driven humanlike actuation rather than simply placing heavy motors at every distal joint.

Sources: 1X NEO

Digit Actuators

Agility Robotics - Digit is a warehouse and manufacturing humanoid designed to operate in existing facilities. Public information focuses on deployments, payload, runtime and workflow rather than actuator supplier details.

Sources: Agility Robotics Digit

Atlas Actuators

Boston Dynamics - Atlas is the easiest example of the industry shift from hydraulic humanoids to electric commercial humanoids. Boston Dynamics states the new commercial Atlas path starts with an all-electric Atlas.

Sources: Boston Dynamics Atlas

PUDU D9 Actuators

Pudu Robotics - PUDU D9 publishes more actuator-adjacent data than many new humanoids, including DOF, maximum joint torque and dexterous hand details.

Sources: PUDU D9

Franka Research 3 Actuators

Franka Robotics - Franka Research 3 is not a humanoid, but it is a benchmark for force-sensitive arm actuation and torque-controlled research.

Sources: Franka Research 3

ROBOTIS OP3 Actuators

ROBOTIS - ROBOTIS OP3 is one of the cleanest examples of an off-the-shelf smart servo humanoid.

Sources: ROBOTIS OP3 e-manual

TALOS Actuators

PAL Robotics - TALOS is a torque-controlled humanoid research platform, useful for understanding why torque sensing and force control matter.

Sources: PAL Robotics TALOS

REEM-C Actuators

PAL Robotics - REEM-C shows a research humanoid where mobility, ROS and broad DOF matter more publicly than supplier-level actuator disclosure.

Sources: PAL Robotics REEM-C

LBR iiwa Actuators

KUKA - KUKA LBR iiwa is not humanoid, but it is a major reference for electric torque-sensing collaborative actuation.

Sources: KUKA LBR iiwa

ANYmal Actuators

ANYbotics - ANYmal is included as a non-humanoid legged robot benchmark because quadrupeds solve many of the same actuator problems as humanoid legs: torque density, shock tolerance, sealing and field reliability.

Sources: ANYbotics ANYmal

Additional Robots Tracked In The Database

The following robots are relevant to actuator research and comparison, but public supplier-level actuator data is limited. They are included so readers can keep exploring the site without mistaking missing data for hidden confirmation.

• Unitree H2: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• Unitree R1: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• EVE: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• Phoenix: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• Walker S: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• Walker X: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• GR-1: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• GR-2: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• Agibot A2: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• Astribot S1: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• Pudu D7: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• CyberOne: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• PX5: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• Iron: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• PM01: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• Kepler Forerunner: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• Menteebot: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• Ameca: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• Pepper: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• NAO: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• ASIMO: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• Valkyrie: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• HRP-4: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• HRP-5P: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• T-HR3: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• iCub: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• ARMAR-6: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• Poppy Humanoid: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• YuMi: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.
• Spot: tracked in the Firgelli Robots database; actuator supplier or torque details should be treated as not publicly disclosed unless the manufacturer page or a technical paper states otherwise.

Actuator Manufacturers and Suppliers

The robotics actuator supply chain includes both public component vendors and in-house custom designs. A supplier should only be attached to a specific robot when a direct source supports it.

Verified vs Reported vs Unknown Actuator Data

Actuator data is often hard to find because companies keep joint designs proprietary, demo robots change between generations, actuator specs vary by joint, patents may describe possible designs rather than production hardware and suppliers are not always publicly disclosed. This article uses these confidence labels:

Internal Links For Robot Research

Continue comparing the actuator tradeoffs on these Firgelli Robots pages: Tesla Optimus, Figure 02, Unitree G1, Apptronik Apollo, 1X NEO, Sanctuary AI Phoenix, Agility Digit, Boston Dynamics Atlas, Humanoid Robots category, Robot Compare and Robot Finder.

FAQs

What actuators do humanoid robots use?

Most modern humanoids use electric rotary joint actuators. A high-performance joint usually combines a brushless motor or PMSM, gear reduction, bearings, encoders, torque or force sensing, brakes where needed and motor-control electronics.

What actuators does Tesla Optimus use?

Tesla has shown and discussed custom humanoid actuator development in public demos, but Tesla's current public AI page does not publish a stable production actuator table with supplier, torque, voltage or gear-ratio data. Treat detailed claims as reported unless tied to a direct Tesla source.

What actuators does Figure 02 use?

Figure 02 appears to use electric humanoid joint modules, but Figure has not publicly released a supplier-level actuator specification table. The safe answer is electric humanoid actuation with detailed supplier, torque and gear data not publicly disclosed.

What actuators does Unitree G1 use?

Unitree publishes that G1 uses low-inertia high-speed internal-rotor PMSM joint motors, crossed-roller bearings, dual encoders, local air cooling and 23 to 43 joint motors depending configuration. Unitree lists knee torque as 90 N.m on G1 and 120 N.m on G1 EDU.

What actuators does 1X NEO use?

1X describes NEO around its tendon-drive approach. In plain English, motors pull routed tendons so force can be transmitted through lighter distal structures, especially useful for human-like arms and hands.

What actuators does Apptronik Apollo use?

Apollo is an electric humanoid robot, but the public product page focuses on modular design, payload, runtime, safety and deployment rather than supplier-level actuator specifications.

Are humanoid robot actuators electric or hydraulic?

The current commercial trend is electric. Earlier high-performance humanoids such as older Atlas generations are associated with hydraulic power, but newer commercial designs favor electric actuation for battery operation, indoor safety and maintenance.

Why do humanoid robots use harmonic drives?

Harmonic drives can provide high gear reduction in a compact joint package. They are useful when a robot needs precision and torque in a small space, though cost, efficiency and compliance tradeoffs matter.

What is a quasi-direct-drive actuator?

A quasi-direct-drive actuator uses a relatively low gear ratio compared with traditional servo gearboxes. It keeps more backdrivability and impact tolerance while still multiplying motor torque enough for legged motion.

How many actuators does a humanoid robot have?

It depends on the robot. Small humanoids may have around 20 actuators; modern full-size humanoids often have 30 to 50-plus controlled joints, and highly dexterous hands can add many more.

What is the difference between DOF and actuator count?

Degrees of freedom describe independent motion axes. Actuator count describes the powered devices. They often match, but tendon systems, passive joints, coupled fingers and differential mechanisms can make the numbers different.

Which actuator type is best for humanoid robots?

There is no universal best. Legs prioritize torque density, shock tolerance and efficiency; hands prioritize compactness and dexterity; arms prioritize payload, precision and force safety.

Do robot fingers use the same actuators as legs?

Usually no. Legs need high-torque structural joints, while fingers often use tiny servos, tendons, cables or compact custom modules.

Why are humanoid robot actuators expensive?

They combine motors, precision gearboxes, bearings, sensors, brakes, control electronics, thermal design, sealing, safety validation and custom mechanical packaging. The actuator is often one of the most expensive parts of the robot.

Sources and Methodology

Research for this article used the Firgelli Robots knowledge brain, approved website image library, official manufacturer pages, official product pages and technical documentation where available. When a manufacturer did not publish actuator suppliers, torque, speed, voltage, gear ratio or motor model, this article marks the field as unknown or not publicly disclosed rather than filling the gap with guesswork.

• FIRGELLI actuator guide
• Tesla AI and Robotics
• Unitree G1 official specifications
• Unitree H1 / H1-2 official specifications
• Boston Dynamics Atlas
• Apptronik Apollo
• Agility Robotics Digit
• PUDU D9 official specifications
• Franka Research 3
• ROBOTIS OP3 e-manual
• PAL Robotics TALOS
• PAL Robotics REEM-C
• KUKA LBR iiwa
• ANYbotics ANYmal