Backdrivable Actuators

QDD actuator platforms for physical interaction, impact absorption, and torque-control workflows where low mechanical impedance matters.

Target Buyer:Best for teams prioritizing compliance, controllability, and disturbance response over maximum static holding stiffness.

High-torque QDD actuator module for legged robot and exoskeleton joints

Capability Highlights

Low mechanical impedance design direction
Transmission choices that support force-control-friendly joints
Useful for walking, jumping, wearable, and human-interactive robots

Typical Applications

Legged robot joints
Exoskeleton and wearable robotics
Collaborative mobile manipulation

Engineering Focus

Backdrive torque, friction, and reflected inertia targets
Impact load, allowable deflection, and recovery behavior
Torque-control loop, encoder resolution, current limit, and bus latency

Buyer Decision Summary

A buyer should leave this page with a shortlist decision: whether this actuator family deserves a sample review, what must be measured first, and which constraints must be fixed before price comparison.

Best Evidence

Start with backdrive torque and connect it to the real robot duty cycle instead of reviewing catalog values alone.

Primary Risk

Backdrivability target conflicts with holding torque

Next Buyer Action

Prepare backdrivability target or comparison actuator plus validation targets before requesting samples or commercial terms.

How to Evaluate This Actuator Family

Use this page to turn a product family into a shortlist decision. The useful comparison is not one headline torque number; it is how the actuator behaves inside the real robot joint.

Backdrive torque

0.3–1.5 Nm unpowered (6:1 planetary), <0.5 Nm target for exoskeletons

Shows how much external torque is needed to move the joint without a motor command.

Reflected inertia

0.03–0.08 kg·m² (QDD 6:1–10:1) vs 2–8 kg·m² (harmonic 50:1–100:1)

Improves interaction behavior and reduces collision harshness.

Friction and cogging feel

Torque ripple <5% of continuous rating at 1 rad/s

Affects torque transparency, gait tuning, and hand-guided motion.

Sample Validation Plan

Before a batch decision, buyers should define the evidence expected from sample review and internal testing.

Signal to Check	Review Basis	Evidence to Ask For
Backdrive torque	0.3–1.5 Nm unpowered (6:1 planetary), <0.5 Nm target for exoskeletons	Separate dynamic motion requirements from static brake or holding requirements during selection.
Reflected inertia	0.03–0.08 kg·m² (QDD 6:1–10:1) vs 2–8 kg·m² (harmonic 50:1–100:1)	Check motor thermal margin and peak current limit before committing to the ratio.
Friction and cogging feel	Torque ripple <5% of continuous rating at 1 rad/s	Separate dynamic motion requirements from static brake or holding requirements during selection.

Acceptance Thresholds to Define

Define measurable pass/fail thresholds before the sample arrives. This prevents a subjective review where one team checks torque, another checks packaging, and nobody records whether the actuator can move toward pilot build.

Backdrive torque: Shows how much external torque is needed to move the joint without a motor command.
Reflected inertia: Improves interaction behavior and reduces collision harshness.
Friction and cogging feel: Affects torque transparency, gait tuning, and hand-guided motion.

When This Family May Not Fit

A QDD actuator family is valuable only when the application needs its trade-offs. The same module can be a poor fit when the surrounding joint requirements point in a different direction.

Backdrivability target conflicts with holding torque: Separate dynamic motion requirements from static brake or holding requirements during selection.
A low-ratio joint is chosen without enough torque margin: Check motor thermal margin and peak current limit before committing to the ratio.

Buyer Inputs That Improve the First Reply

A complete first inquiry shortens review loops because engineering can separate fixed constraints from adjustable actuator choices.

Fixed Constraints

Backdrivability target or comparison actuator
Expected external force or impact scenario
Torque sensor, encoder, and control bus preference

Review Targets

Static holding requirement and whether a brake is needed
Joint envelope and cable routing constraints

Key Evaluation Matrix

Metric	Typical Range	Why It Matters
Backdrive torque	0.3–1.5 Nm unpowered (6:1 planetary), <0.5 Nm target for exoskeletons	Shows how much external torque is needed to move the joint without a motor command.
Reflected inertia	0.03–0.08 kg·m² (QDD 6:1–10:1) vs 2–8 kg·m² (harmonic 50:1–100:1)	Improves interaction behavior and reduces collision harshness.
Friction and cogging feel	Torque ripple <5% of continuous rating at 1 rad/s	Affects torque transparency, gait tuning, and hand-guided motion.

Engineering Documents by RFQ

Document packages are shared after the actuator family, joint envelope, and program context are clear. Ask for available datasheets, drawings, CAD files, torque-speed notes, compliance records, or test reports during RFQ review.

Document	Status	RFQ Input Needed
Datasheet PDF	Available by actuator class review	Torque, speed, voltage, and quantity target
2D drawing	Available by mechanical envelope review	Shaft, flange, bolt pattern, and connector constraints
3D CAD / STEP / IGES	Shared when applicable after RFQ context	Joint envelope, mounting direction, and confidentiality needs
Torque-speed / thermal envelope	Program-dependent review	Duty cycle, ambient temperature, current limit, and mounting heat path
Compliance or test reports	Requestable per program when available	Destination market and required document list

How to Request CAD / Datasheets Compliance Document Scope

RFQ Checklist

Backdrivability target or comparison actuator
Expected external force or impact scenario
Torque sensor, encoder, and control bus preference
Static holding requirement and whether a brake is needed
Joint envelope and cable routing constraints

Risk Controls

Backdrivability target conflicts with holding torque: Separate dynamic motion requirements from static brake or holding requirements during selection.
A low-ratio joint is chosen without enough torque margin: Check motor thermal margin and peak current limit before committing to the ratio.

Product Gallery

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Compact 14 Nm quasi-direct-drive module for legged robot joint review

Buyer FAQ

Are backdrivable actuators always better?

No. They fit dynamic and interactive robots. High-ratio precision joints may still fit static or ultra-precise axes.

Can backdrive torque be tuned?

It can be influenced through ratio, bearing layout, seal/friction design, motor sizing, and controller strategy, but it should be validated on samples.

Related Resources

Inquiry Email

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Include robot type, joint location, torque/speed/voltage targets, quantity, and destination.

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