Humanoid Robot Actuators & Hands

01What is an actuator

An actuator is whatever converts a control signal into physical motion — the rough equivalent of a muscle. The dominant design in humanoid robots is an electric actuator: a motor paired with a reduction gearbox that trades the motor's naturally high rotational speed for the high torque needed to swing an arm or bear body weight, plus position and torque sensors that feed data back to the controller. Two gearing families dominate humanoid joints. Strain-wave gearing (sold under the trademark Harmonic Drive by its inventor, Harmonic Drive Systems) flexes a splined cup elliptically inside a rigid ring gear to get a high reduction ratio, near-zero backlash, and a compact, lightweight package in a single stage — which is why it shows up in so many rotary arm and leg joints across the industry. Planetary gearing, and its linear cousin the planetary roller screw, arrange rollers or gears around a central sun gear or screw instead; they give up some of strain-wave gearing's compactness for higher load capacity and durability, which is why they tend to show up in load-bearing joints and linear actuators. (Harmonic Drive Systems — strain-wave gearing technology)

Hydraulic actuation — a piston driven by pressurized fluid instead of an electric motor — was the default in early legged robots, because a small cylinder can deliver enormous force. But it comes with leak risk, ongoing maintenance, and a pump and reservoir that don't fit inside a forearm the size of a human one — a large part of why nearly every new humanoid hand and arm design unveiled in 2025–2026 is electrically actuated rather than hydraulic.

02Why one arm needs so many actuators

Placing a hand at any position and orientation in 3D space takes six independently driven joints at minimum — the same six-degrees-of-freedom logic that governs a conventional industrial robotarm. A humanoid hand then stacks a second, harder problem on top: fitting enough independently actuated joints into a package the size of a human hand to grip, pinch, and manipulate the way a hand actually does, rather than just open and close around one shape. The current generation of humanoid hands — compared in detail further below — all converge on the same trick to make that fit: moving most of the actuators out of the palm and into the forearm, then driving each finger with tendons routed through the wrist, the same way human finger motion is actually driven by muscles in the forearm rather than muscles inside the hand itself. That frees up space and mass in the hand itself, which is what has to move fastest and lightest.

03Force/torque sensing

A force/torque sensor measures the forces and torques acting at a single point — typically all six components at once (three forces along X/Y/Z, plus three torques around them) — most often mounted at a robot's wrist. ATI Industrial Automation, a Novanta-owned maker of wrist-mounted force/torque sensors and robotic end-of-arm tooling, is one of the standard suppliers of this hardware to robot builders. What it enables is compliant control: instead of blindly following a pre-programmed position, a controller reading force/torque feedback can hold a target contact force (pressing a part flush without crushing it) or yield the moment it meets unexpected resistance (a human arm in the way). That's the difference between a robot that can only move to fixed points and one that can safely share a workspace with people or handle objects of unknown stiffness.

04Tactile sensing

Tactile sensors go a layer further, embedded directly in the fingertip rather than the wrist. Instead of one combined six-axis reading for the whole limb, they sense localized contact: where on the fingertip an object is touching, how hard, and whether it's starting to slip — the kind of feedback human skin provides that a camera, mounted outside the hand, structurally cannot, because once fingers close around an object the camera loses its view of the contact itself.

Figure AI built its own fingertip tactile sensors for its Figure 03 humanoid after concluding that off-the-shelf sensors couldn't survive real-world use; they can detect forces as small as three grams — about the weight of a paperclip — which the company says lets its Helix AI system distinguish a secure grip from an object about to slip before it actually does. (Figure AI — Introducing Figure 03)

Analog Devices has demonstrated a further-out prototype: a multimodal tactile sensor it says can resolve contact detail up to five times finer than a human fingertip. At Nvidia's GTC 2026, ADI showed the sensor driving a humanoid hand that traced a network cable to its socket by touch alone — no camera in the loop — using a control policy trained in Nvidia's Isaac Sim simulator. (Analog Devices — the future of tactile sensing; ADI at Nvidia GTC 2026)

onsemi, separately, showed an inductive position sensor built into a robotic hand at Embedded World 2026 — aimed at a related but different problem: tracking a joint's own position and velocity precisely, rather than sensing outside contact. (onsemi — Embedded World 2026)

05Dexterous hands: current examples

"Dexterous hand" is the industry's term for a multi-fingered hand built to manipulate objects the way a human hand does, rather than just clamp shut around one shape like a factory gripper. Three hand designs made public within the past year show how differently teams are solving the same actuator-density problem:

None of this is single-company work. A wave of upstream component suppliers is racing to serve exactly this actuator-and-sensor stack — gearing specialists like Harmonic Drive Systems and Japan's Nabtesco, and chipmakers such as Analog Devices and onsemi building reference tactile- and position-sensing hardware aimed specifically at humanoid hands. See the Investment Trackerfor the public-market angle on this supply chain, and Industrial Robotfor how the same reduction-gearing playbook powered factory-floor robot arms for decades before humanoids adopted it.

06FAQ