Application characteristics and parts of cross roller bearings in humanoid robots

Application characteristics and parts of cross roller bearings in humanoid robots

Cross roller bearings are widely used in precision transmission and high load joints of humanoid robots, which can meet the requirements of multi-directional loads, high rigidity, high precision, and compact small space due to their unique structural characteristics. The following is an analysis of its typical application scenarios and types:

1. Core advantages of cross roller bearings

*Multi directional bearing capacity: The rollers are arranged in a 90 ° cross pattern and can simultaneously withstand radial, axial, and moment loads.

*Ultra high rigidity: The contact area between the roller and the raceway is large, and the deformation resistance is better than that of ordinary bearings.

*Zero clearance design: no clearance after pre tightening, ensuring motion accuracy.

*Compact structure: low height, small volume, suitable for joint space limitations of humanoid robots.

2. Typical application scenarios

(1) Joint axis systems, such as shoulder, elbow, and knee joints.

*Requirements: High torque transmission, multi degree of freedom movement, and impact resistance.

*Solution:

-Cross roller bearing: used at the output end of the reducer to withstand the composite load during joint swing.   

-Split structure: easy to install in narrow spaces, such as at knee joint linkages.

(2) End effectors, such as hands/grippers

*Requirement: High frequency micro motion, high positioning accuracy.

*Solution: Micro cross roller bearings: diameter ≤ 10mm, used for finger joints or tool quick change mechanisms.

(3) Spinal/lumbar rotation platform

*Requirement: Large angle rotation, high stability.

*Solution: Circular cross roller bearing: Inner/outer ring separation design, supporting 360 ° continuous rotation (such as waist torsion mechanism).

3. Bearing type and parameter.

4. Materials and Special Designs

*Bearing steel material: high hardness and wear resistance, uniform chemical composition, corrosion resistance and high temperature adaptability.   

*Stainless steel material: corrosion-resistant, used for humanoid robots in medical or chemical scenarios.   

*Lubrication plan: Sealing grease lubrication: Long term maintenance free (such as robot joints).   

5. Typical manufacturers and cases

Xiaomi adopts customized cross roller bearings, which improve impact resistance by 40%.   

The waist rotation platform of the humanoid robot adopts annular bearings, with a rotation accuracy of ± 0.01 °.   

Micro cross roller bearings are applied to biomimetic finger joints with a repeat positioning accuracy of ± 0.001mm.

6. Design Challenges and Optimization Directions

*Thermal expansion compensation: Joint heating causes bearing jamming, and thermal expansion clearance needs to be reserved.   

*Dynamic balance: During high-speed rotation, the centrifugal force of the rollers causes vibration, and the number and distribution of rollers need to be optimized.   

*Life prediction: Bearing life simulation based on joint motion trajectory.

Summary: Cross roller bearings are mainly used for high-precision and high load joints in humanoid robots, and their selection needs to comprehensively consider factors such as load direction, space constraints, and environmental conditions. The future trend will develop towards modular design and self-lubricating structures to adapt to more complex humanoid robot task requirements.