High-torque-density 105Nm quasi-direct-drive (QDD) actuator module with low reflected inertia, high impact resistance, and active force control for humanoid robot joints and legged platforms.
Simulate humanoids and quadruped leg kinematics to calculate peak load matches.
1. Input Robot Configurations
Robot Geometry Layout
Target Joint Location
65 kg
15 kg150 kg
0.4 m
0.15 m0.80 m
locomotion gait dynamics
Dynamic factors scale the gravity load vector to account for inertia during acceleration.
Driver DC Bus Voltage
2. Calculation & Safety Match
Peak Joint Torque Required0 Nm
Optimal Match
Safety Factor Matrix0x (105Nm limit)
Reflected Inertia (J_ref)0 kg·m²
Backdrive Impedance< 0 Nm
Thermal Headroom0% remaining
Actuator Sizing Verdict:
Ideal matching zone. The 105Nm peak torque handles dynamic acceleration transients perfectly, while continuous walk loads sit in the stable thermal heat-conduction zone.
Metallurgical Impact: High case depth (0.6–0.9 mm) combined with root grinding minimizes dynamic fatigue and root shear under peak torque spikes (105 Nm).
Tribology & Precision Joint Lubricants
Lubricant Brand
Base Oil & Thickener
Operating Temp
NLGI Class & Advantage
Kyodo Yushi Molywhite RE No. 00
Synthetic Hydrocarbon (PAO) + Lithium soap
-40°C to +130°C
Semi-fluid (NLGI 00) - Extremely high load, anti-fretting under micro-oscillations
NLGI 2 (Standard Grease) - Superior water-washout resistance, good for outdoor field quadrupeds
Tribology Note: Semi-fluid NLGI 00 grease prevents channeling effects in compact planetary systems, ensuring 100% wet lubrication on sun-and-planet gear tooth meshes at startup.
Field Verification
Humanoid & Legged Robotics Integration Case Studies
Review how robotics R&D teams deploy the 105Nm actuator in dynamic field environments.
01
70kg Dual-Leg Humanoid Vertical Jump & Land (Knee Joint)
Premise: A 70kg bipedal humanoid robot executing a 0.45m vertical jump. The knee pitch joints require instant peak torque output during push-off and quick energy absorption on landing.
Process: The knee joints were fitted with 105Nm QDD Actuator modules operating at 48V DC. During landing, ground impact reached 3.1G (2,130 N). The low reflected inertia (0.052 kg·m²) allowed the joints to backdrive within 14ms, routing mechanical impact energy into the bus capacitors to protect gear tooth profiles.
Field Result: Joint recovery settled in 62ms with zero permanent tooth deflection or micro-cracks detected after 5,000 jump landing cycles. Dynamic backlash remained under 4.8 arcmin.
Premise: A 50kg quadruped robot executing inspection gaits on gravel terrain in 38°C ambient desert temperature. Nominal hip/knee joint continuous torque is 28 Nm.
Process: Utilized 105Nm QDD Actuator modules with integrated thermal sink plates bolted to the aluminum frame. Software FOC active thermal calibration adjusted phase current limiters in real-time to avoid stator winding overheat.
Field Result: Winding temperature stabilized at 79°C after 12 hours of continuous trotting. Active calibration kept joint angle calculation errors under ±1.2%, preventing leg sagging.
03
Wearable Rehabilitation Lower-Limb Exoskeleton
Premise: Rehabilitation active exoskeleton for patients requiring zero-impedance safety. Patient hand-driven backdrive torque must be kept under 1.2 Nm for comfortable gait assistance.
Process: Fitted with 105Nm modules configured with standard 8:1 planetary gear. Used FOC motor-side shunt resistor current readings to execute friction model compensation, without external load cell sensors.
Field Result: Passive backdrive torque measured at 0.58 Nm. With active software current compensation, perceived patient resistance torque dropped below 0.12 Nm, ensuring smooth movement.
04
Collaborative Robot Arm Joint Torque-Estimation & Collision Detect
Premise: 6-DOF collaborative arm handling 6kg payload. Collision detection response must trigger within 15ms under ISO TS 15066 safety limits.
Process: Base and shoulder joints fitted with 105Nm QDD Actuator modules. Phase current waveforms were analyzed via 20kHz FOC loop to estimate output joint torque and filter out motor cogging noise.
Field Result: The arm detected external forces down to 2.8 N, triggering dynamic compliance safety stop in 11.2ms without external torque sensors, saving significant cost and cabling.
FAQ & Support
Buyer Technical Q&A & Support Reference
Technical answers regarding mechanical backdrivability, electrical bus protocols, and thermal sizing tolerances.
Why is low reflected inertia critical for legged/humanoid robots?
Reflected inertia is proportional to the square of the gear reduction ratio. In high-ratio harmonic systems (e.g., 100:1), motor inertia is multiplied by 10,000, creating a highly rigid joint that transfers external impact shocks directly to the gears, causing tooth breakage. In our 105Nm QDD actuator (8:1 planetary ratio), motor inertia is only multiplied by 64, allowing the joint to rotate backward (backdrive) and absorb shock forces mechanically.
What gear steel grade is used in the planetary reducer of the 105Nm module?
We use high-purity aerospace alloy steel (18CrNiMo7-6) with precise carburizing and tooth profiling modification. The tooth root thickness is increased with a 22.5° pressure angle, doubling bending fatigue strength under impact loading compared to standard industrial gears.
How does the 105Nm QDD handle backlash degradation over time?
By implementing eccentric planetary pin preloading and hard carbon-nitriding surface treatments. This ensures that the initial backlash of 3-5 arcmin degrades by less than 1.8 arcmin even after 8,000 hours of continuous quadruped walk profiles.
Is the 15mm hollow shaft bore customizable?
Yes, the standard version has a 15mm clear through-bore. We can customize this up to 20mm for route-heavy joints, but this reduces internal bearing dimensions. Contact engineering to review radial and axial load capacity changes.
Can this QDD actuator operate reliably in force control without an external torque sensor?
Yes. Because our 8:1 planetary gear has high efficiency (>91%) and very low friction, the motor current is highly linear to output joint torque. By using FOC current readings and compensating for friction/cogging in software, we achieve joint-torque estimation accuracy within 1.5% of peak torque.
What is the purpose of the dual-absolute encoder setup?
The motor-side encoder (19-bit magnetic) operates high-speed FOC current commutation. The output load-side encoder (19-bit absolute) measures actual joint angles. This allows the driver to correct for planetary backlash, tooth deflection under load, and mechanical joint compliance in real-time.
What communication protocols does the integrated driver support?
The integrated driver supports EtherCAT (CoE, up to 2.0 kHz loop rate) and CAN-FD (up to 1.0 kHz loop rate) out-of-the-box. RS-485 is available for simple non-dynamic auxiliary axes.
How do you handle torque ripple (cogging torque) at low speeds?
By using fractional-slot concentrated windings and stator skewing combined with active harmonic current injection (5th and 7th order slot harmonics compensation) in the driver firmware. This keeps torque ripple under 1.4% of peak ratings.
How does high winding temperature affect joint performance?
High winding temperatures increase stator copper resistance. From 20°C to 110°C, the motor torque constant (Kt) drops by roughly 11%. The driver firmware continuously estimates winding temperature and compensates current gains to maintain torque output stability.
What is the thermal shutdown limit and safety threshold?
Winding temperature safety warning triggers at 95°C. At 110°C, the driver initiates automatic linear current derating (4% torque reduction per °C). At 125°C, bridge MOSFETs enter over-temperature shutdown to protect coil insulation from degradation.
How do I calculate the thermal headroom for my gait duty cycles?
Calculate the Root Mean Square (RMS) torque of your movement loop. As long as the RMS torque is within the continuous thermal limit of 35 Nm (mounted to a standard aluminum heatsink frame at 25°C ambient), the joint temperature will stabilize below 80°C.
Does the actuator support liquid cooling paths?
We offer an optional liquid cooling jacket housing customization (OEM) for heavy payload humanoids. Under liquid cooling, the continuous torque threshold increases from 35 Nm to 52 Nm due to accelerated heat dissipation.
How does winding temperature rise affect the motor torque constant (Kt) and how is it compensated?
As stator coil temperature rises from 20°C to 110°C, the torque constant (Kt) drops by ~11.5% due to the increased resistance of the copper wire and the temperature-dependent reduction in magnetic flux density of the NdFeB magnets. To mitigate this torque fade, the integrated FOC driver executes real-time compensation via a software-based thermal model. By calculating winding resistance using phase current integration and correcting the FOC q-axis current gain dynamically, torque linearity is maintained within ±1.5%.
Which FOC controller chip architecture drives the integrated inverter, and what is the current control bandwidth?
The driver runs on an STMicroelectronics STM32G474RET6 microcontroller featuring an ARM Cortex-M4 core running at 170MHz, equipped with mathematical hardware accelerators (CORDIC for fast sine/cosine computations used in Clarke/Park transforms). The current loop runs at 20kHz, while the velocity/position loops run at 10kHz. This high bandwidth allows the actuator to respond to external torque disruptions within 0.5 milliseconds, matching the dynamic demands of balance recovery in legged platforms.
What is the backlash drift expectation under continuous humanoid walking cycles?
The 105Nm QDD planetary gearbox uses a dual-point preloaded eccentric sun gear system. Initial factory-cleared backlash is 3–5 arcminutes. Under normal operating conditions (nominal walking torque ≤35 Nm at 1.5 m/s), gear tooth wear is minimized by the PAO-based Kyodo Yushi Molywhite RE No. 00 lubricant. Backlash drift is kept below 1.5 arcminutes after 5,000,000 gait cycles (roughly 6,000 hours of continuous operations), guaranteeing that humanoid foot placement accuracy remains within ±2.5 mm.
Engineering Sizing Disclaimer & Safety Warning:The output joint calculations and torque estimates generated by this simulator are for initial design evaluation and baseline scoping only. Actual dynamic joint behavior will vary depending on payload fluctuations, walking gait trajectory profiles, mechanical linkage deformation, and ambient thermal conditions. Robotics R&D teams must perform dynamic multibody physical simulations and physical prototype testing under thermal load before finalized volume design sign-off.
RFQ Procurement Checklist & Lead Time Sizing
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Required Procurement Details
Dynamic Load Cycle: Target acceleration profiles, continuous payload mass, and leg layout geometry STEP reference.
Send QDD actuator specs, STEP files, or actuator references for engineering review.
Data Sources & Empirical References
This technical specification sheet and sizing database are compiled based on high-fidelity empirical tests, commercial robotics manuals, and academic literature. Last verified and updated on June 20, 2026.
