A robotics R&D company specializing in bipedal humanoid platforms approached us with a need for highly compact yet high-torque reduction units for their knee and hip joints. These actuators required extremely low backlash to allow for smooth, lifelike motion control, as well as high load endurance due to the dynamic forces generated during walking, balancing, and stair climbing. The project also demanded that the gearbox fit within an envelope diameter of less than 70mm and weigh under 500 grams, while maintaining sub-arcminute precision.
Key Requirements:
- Installation: Hollow shaft with custom mount interface
- Gear Ratio: 100:1
- Rated Torque: 80 Nm
- Peak Torque: 160 Nm
- Backlash: ≤0.5 arcmin
- Outer Diameter: ≤70 mm
- Weight: ≤500 g
- Durability: 2 million full load cycles
- Protection Level: IP54, optimized for indoor mobile robotics
Our Solution
We engineered a customized high-precision harmonic gearbox with integrated cross-roller bearing support. Key features include:
- Flexspline structure with reinforced alloy steel for high fatigue resistance
- Preloaded bearing arrangement for increased rigidity and control precision
- Multi-stage heat treatment and micro-lapping process for reduced friction and noise
- Precision balancing and rotor alignment for smooth high-speed actuation
- Integrated encoder flange mounting interface, pre-tested for 0.01 mm concentricity
Impact and Outcome
The final drive unit delivered repeatable positioning accuracy within ±3 arcsec, enabling natural gait motion and improved load balancing. The client reported:
- A 23% improvement in energy efficiency during walking cycles
- Zero play in start-stop movement transitions
- Extended mean time between failures (MTBF) by 40% compared to their previous design
This gearbox is now implemented in the full lower-limb series of the humanoid platform.
