Quasi-direct-drive (QDD) motor sizing guidance for integrated modules, including 105Nm target configurations and 105nm integrated quasi-direct drive motor module selection.
Adjust target joint requirements below to estimate reflected inertia, gear ratios, and matched actuator models.
The 105nm integrated quasi-direct drive motor module features a lightweight 9:1 planetary reducer nested within the rotor core. This design optimizes coaxial space and heat dissipation.
| Model Class | Peak Torque | Reduction Ratio | Module Weight | Continuous Torque | Target Joint Application |
|---|---|---|---|---|---|
| QDD-24-6 | 24 Nm | 6:1 | 0.9 kg | 8 Nm | Light quadruped knee / Wearable joint |
| QDD-60-8 | 60 Nm | 8:1 | 1.6 kg | 20 Nm | Medium quadruped knee / Humanoid arm |
| QDD-105-9 (Target) | 105 Nm | 9:1 | 2.45 kg | 35 Nm | 105Nm Heavy quadruped hip-knee / Humanoid leg |
| QDD-200-10 | 200 Nm | 10:1 | 4.8 kg | 65 Nm | Heavy humanoid biped leg / Exoskeleton waist |
| QDD-300-10 | 300 Nm | 10:1 | 7.2 kg | 95 Nm | Industrial legged transport robot joints |
Operating voltage directly determines the back-electromotive force (Back-EMF) saturation point of the motor windings. Running the 105Nm QDD module at 24V limits its peak speed severely due to early voltage saturation.
To output the target 105Nm peak torque at high gait speeds (e.g., 180 RPM knee extension), a 48VDC supply is optimal. Under 72VDC overdrive, the module can achieve an envelope extension up to 260 RPM before torque drop-off.
| Bus Voltage | Peak Speed | Back-EMF Constant | Peak Power Draw |
|---|---|---|---|
| 24 VDC | 90 RPM (Voltage Saturation) | 0.081 V/rad/s | 950 W |
| 48 VDC (Std) | 180 RPM (Optimal Winding) | 0.081 V/rad/s | 1,980 W |
| 72 VDC | 260 RPM (Overdrive Dynamic) | 0.081 V/rad/s | 2,850 W |
Reflected inertia ($J_{reflected} = J_{rotor} \times N^2$) dictates the mechanical impedance of the robot joint during impact. With high gear ratios, reflected inertia shoots up quadratically, causing high impact shear stress that can shear gear teeth.
The 9:1 QDD configuration filters high-frequency external shocks by backdriving easily, allowing energy to propagate back to the motor winding. This makes QDD modules highly robust against hard landing collisions.
| Type | Backlash | Backdrivability | Shock Resistance |
|---|---|---|---|
| Planetary (QDD) | 3–6 arcmin | High (<0.8 Nm) | Excellent (Backdrives) |
| Harmonic Drive | <0.5 arcmin | Non-Backdrivable | Fragile (Shearing) |
| SEA (Series Elastic) | N/A (Soft) | Compliance backdrive | High (Elastic absorb) |
To eliminate the backlash error of the planetary gear stage, the module implements a dual-absolute encoder setup. The motor-side encoder (19-bit) tracks rotor position for the FOC current loop, while the load-side encoder (19-bit) measures output joint angles.
Cascade PID loops run at 20 kHz for current, 2 kHz for speed, and 1 kHz for position. Dual-loop feedback compensates for non-linear transmission error, guaranteeing high mechanical accuracy.
| Setup | Backlash Comp. | Bandwidth | Complexity |
|---|---|---|---|
| Single Encoder | No Compensation | High | Low |
| Dual Encoder (Std) | Yes (Software LUT) | Medium-High | Medium |
| Encoder + Torque Sensor | Dynamic Torque Force | Low-Medium | High |
In dynamic legged robotics, force control loop bandwidth is highly restricted by communication bus latency. Delays in position/torque commands propagate into phase delays, causing joint instability or violent oscillations during high-frequency impact events (e.g., foot landing).
The 105Nm QDD module integrates an industrial-grade EtherCAT controller (CoE profile) supporting Distributed Clocks (DC) with jitter <2μs. This enables hard real-time synchronization, pushing torque command bandwidth to 2.0 kHz.
| Protocol | Typical Latency | Clock Jitter | Torque Bandwidth | Fail-Safe Capability |
|---|---|---|---|---|
| EtherCAT (CoE) | 0.1–0.5 ms | ±2 μs (Dist. Clock) | Up to 2.0 kHz | Excellent (Ring Redundancy) |
| CAN-FD | 0.8–1.5 ms | ±25 μs | Up to 1.0 kHz | High (Arbitration/CRC) |
| RS-485 (RTU) | 2.5–5.0 ms | ±150 μs | Up to 200 Hz | Medium (Half-duplex packet loss) |
Planetary transmission efficiency ($\eta$) is not a fixed constant. It varies dynamically based on rotor speed, joint output torque load, and operating temperature. In low-torque, high-speed regimes, grease shearing dominates losses, reducing efficiency to ~86%.
The mathematical relationship for joint backdrivability determines the minimum torque ($T_{backdrive}$) required on the output shaft to spin the motor rotor backward:T_backdrive = (T_friction_motor * N) / η + T_friction_gearUsing a single-stage 9:1 planetary reducer allows $T_{backdrive}$ to stay under 0.8 Nm, yielding outstanding joint transparency.
| Load Case | Efficiency (η) | Lubricant Temp. | Dominant Loss Factor |
|---|---|---|---|
| Nominal Load (35 Nm, 120 RPM) | 91.2% | 55°C (Stabilized) | Optimal lubrication viscosity |
| Low Load / High Speed (10 Nm, 240 RPM) | 86.5% | 40°C | Fluid shear dragging loss |
| Peak Impact Load (105 Nm, 30 RPM) | 83.8% | 85°C (Transient peak) | Elastohydrodynamic film compression |
Continuous operating torque is restricted by copper winding losses ($I^2R$). Winding temperatures above 110°C will trigger active current limits to prevent thermal breakdown of winding insulation.
When winding temperatures cross 100°C, the FOC driver applies a 4%/°C linear derating curve, shutting down completely at 125°C.
| Gait Load Case | RMS Torque | Temp Rise | Max Duration |
|---|---|---|---|
| Static Standby | 12 Nm | <0.05°C/s | Infinite |
| Slow Gait / Walk | 35 Nm | ~0.25°C/s | 240 seconds (to 100°C) |
| Trot / Jump landing | 105 Nm | ~1.40°C/s | 4.5 seconds (Pulse burst) |
Standard modules utilize radial thermal fins machined directly into the Al7075 housing. Mounting the module on an aluminum robot frame piece (acting as a heat sink with surface area >0.05m²) increases passive dissipation by 150%, delaying active current limits indefinitely under walking gait RMS profiles.
Without a load-side torque sensor, joint torque is estimated via motor phase current. However, magnetic flux linkage ($\Psi_m$) and copper winding resistance drift as temperatures rise, causing torque estimation errors up to 8.5% at 110°C.
The internal FOC firmware contains a temperature look-up table (LUT) that compensates for magnet flux degradation. Dynamic temperature compensation keeps torque estimation error below ±1.2%.
| Calibration Test | Tolerance Limit | Methods |
|---|---|---|
| Gear Backlash Drift | < 4.5 arcmin | Reverse locking dyno torque cycle |
| Torque Ripple (Friction) | < 1.5% of peak | Phase current mapping compensation |
| Thermal Estimator drift | ±1.2% accuracy | PT1000 sensor feedback LUT sweep |
Every QDD module goes through factory calibration to map the difference between the motor rotor and load shaft angles across 360° rotation. Non-linearities from planetary gear backlash and structural elasticity are stored in a lookup table (LUT) inside the driver EEPROM to compensate dynamically for joint positioning errors.
How to use the 105Nm QDD motor module target class as an RFQ and sample-test screen before treating it as a validated robot joint.
Premise: Humanoid robot (75kg) executing a 0.4m vertical jump and landing. The knee joint requires peak torque of 100 Nm and quick shock energy absorption.
Process: Use the QDD-105-9 target class at 48V as an RFQ screen, then request supplier landing-pulse dyno logs, bus-clamp sizing, and gearbox inspection criteria before committing the knee architecture.
Result: Decision output: 105 Nm peak torque is plausible for first-pass packaging, but release requires signed impact-cycle data and post-test backlash inspection on the final joint stack.
Premise: Quadruped inspection robot walking on gravel road under 40°C ambient temperatures for 24 hours continuously. Knee joints RMS torque is 28 Nm.
Process: Evaluate the QDD-105-9 target class against mounted-frame thermal assumptions, then request supplier RMS-duty thermal curves instead of relying on open-air peak-torque ratings.
Result: Decision output: proceed only if the supplier provides winding-temperature logs for the intended mounting path, ambient temperature, current limit, and gait duty cycle.
Premise: Rehabilitation active exoskeleton for patients. Active compliance (low mechanical impedance) is required, limiting hand-driven backdrive torque to < 0.8 Nm.
Process: Compare a lighter QDD-60-8 class with the 105 Nm class because patient-worn joints often care more about backdrive torque, mass, and unpowered safety than peak torque.
Result: Decision output: if hand-backdrive torque and mass dominate the requirement, do not overspec a 105 Nm integrated module without a brake, fail-safe, and comfort review.
Premise: Collaborative arm handling 5kg payload. Fast collision detection (<15ms) is needed for human safety compliance under ISO TS 15066.
Process: Screen QDD-105-9 modules for base and shoulder axes only after comparing reducer stiffness, current-estimated torque resolution, and whether an external torque sensor is required.
Result: Decision output: use current-estimated torque for early prototypes, but request safety validation, sensor evidence, and controller logs before collaborative deployment.
How the structural casing materials perform under dynamic loads and heat dissipation needs.
| Material Grade | Tensile Yield | Density | Thermal Cond. |
|---|---|---|---|
| Al7075-T6 (Standard) | 503 MPa | 2.81 g/cm³ | 130 W/m·K (Best cooling) |
| Ti-6Al-4V (Titanium Gr5) | 880 MPa | 4.43 g/cm³ | 6.7 W/m·K (Poor thermal) |
| CFRP (Carbon Fiber) | ~600 MPa (Anisotropic) | 1.55 g/cm³ | < 5.0 W/m·K (Needs sinks) |
Pressure angle increased to 22.5° to withstand peak torque shear forces.
These questions match the page structured data and cover the alias-search intent before a technical RFQ.
It is a highly integrated robotic joint module concept that packs a high-torque brushless PMSM motor, a low-ratio planetary gear such as 8:1 or 9:1, high-resolution absolute encoders, and thermal sensors into a compact housing. A 105 Nm peak-torque class can fit quadruped knees or humanoid hip/knee screening, but the final rating must be confirmed with supplier datasheets, duty-cycle curves, and sample validation.
QDD motors trade off some positional holding stiffness for backdrivability, high impact robustness, and transparency in torque control. Harmonic drives have high ratios, are non-backdrivable, and can easily shear under external impact, whereas QDD gear teeth are robust and the output can easily reverse-drive the motor to dissipate impact energy.
We support customizing motor windings for different bus voltages (e.g., 24V, 48V, 72V), customizing output shaft and flange geometry, absolute encoder options (BiSS-C, SSI, Incremental), integrated brake configurations, and different communication protocols (EtherCAT, CAN-FD, RS485).
Reflected inertia is calculated by multiplying the motor rotor inertia by the square of the gear ratio. In traditional high-ratio harmonic systems, a 100:1 ratio multiplies rotor inertia by 10,000. Under high-speed collisions, this inertia causes high destructive forces before the controller can react. In a 9:1 QDD system, the multiplier is only 81, allowing the output shaft to rotate backward and safely absorb impact.
We utilize gear teeth profile modification with a pressure angle increased to 22.5°. This design increases tooth root thickness, shifting stress concentration away from the pitch circle and doubling bending fatigue strength under jump landing shocks.
By implementing eccentric planetary pin preloading and hard carburizing treatment on gear surfaces. This minimizes tooth wear, ensuring the backlash degradation is under 2 arcmin after 10,000 hours of standard walk gait cycles.
The standard 105Nm module has a 15mm clear inner bore. We can customize the through-hole diameter up to 22mm, but this reduces output bearings housing space. Contact sales to check load ratings.
Planetary needle bearing contact fatigue. Due to low ratio rotation, grease can be squeezed out of bearing channels. We use high-pressure polyurea grease to maintain grease coverage and extend L10 life.
DD has no gear stages, leaving it torque-limited for humanoid knees. QDD uses 6:1 to 10:1 reducers to multiply motor torque while preserving backdrivability, low weight, and high torque transparency.
Include these parameters in your inquiry to accelerate quotation and engineering review:
Evidence reviewed on July 28, 2026. Use this page as an engineering screening model for a 105nm integrated quasi-direct drive motor module, not as a final signed datasheet. Public sources support the QDD architecture and comparison logic; supplier-specific 105 Nm limits still need project-level validation.
Peer-reviewed reference for low-ratio QDD actuation, compact backdrivable knee assistance, torque, temperature, and validation framing.
Research context for QDD actuator design, characterization, Joule heating, continuous torque limits, and legged-robot duty cycles.
Research basis for balancing motor torque, inertia, motor constants, and transmission ratio in quasi-direct-drive systems.
Commercial QDD category reference for comparing public product classes; verify final figures against current supplier datasheets.
Commercial humanoid platform reference for joint-level load context; not a substitute for component-level supplier drawings.
Commercial integrated-joint reference for torque-density benchmarking and RFQ comparison boundaries.
| Evidence Class | Decision Boundary |
|---|---|
| Public evidence supports | Low-ratio QDD architecture, reflected-inertia tradeoffs, backdrivable actuator validation methods, and thermal/duty-cycle concerns. |
| This page models | A 105 Nm target class using transparent assumptions for ratio, efficiency, bus voltage, torque demand, and speed demand. |
| Supplier must confirm | Peak and continuous torque, torque-speed curves, mounting heat path, backlash, impact-cycle data, firmware limits, and safety behavior. |
| Do not infer | That scenario outputs are published field-test guarantees or that one 105Nm module fits every humanoid, quadruped, arm, or exoskeleton joint. |
Contact our applications team to discuss your joint envelope, target ratios, loading cycles, and batch delivery schedules.
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