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The "Revolution" in Quadruped Robot Joint Design: The Secret Weapon of Being as Light as a Feather and as Stable as a Rock

2025-08-19

The following is a full-text analysis of The "Revolution" in Quadruped Robot Joint Design: The Secret Weapon of Being as Light as a Feather and as Stable as a Rock (combining patent technology and application practice):

I. Technical Background: Addressing Fatal Shortcomings of Traditional Joints

Traditional quadruped robot joints generally have three major pain points:

  1. Weak impact resistance: Impact forces in complex terrains easily cause bearing displacement or gear breakage. The joint failure rate of a domestic quadruped robot in rock road tests reached 30%.
  2. Large transmission clearance: The axial clearance of traditional hinge designs gradually increases with use. The clearance of a competing product's joint increased from 0.05mm to 0.3mm after 100 hours of operation, directly affecting gait accuracy.
  3. High maintenance costs: The open structure requires frequent lubrication, and the annual maintenance cost of an industrial inspection robot accounts for 25% of the total machine cost.

II. Core Innovation: Dual-Bearing Preloading and Self-Lubricating System

Hangzhou Unitree Technology has achieved a disruptive breakthrough in joint performance through the combined design of axial preloading + self-lubricating oil storage:

1. Dual-Bearing Collaborative Load-Bearing Structure

  • Radial impact resistance module: Adopts a sliding bearing set (copper-based alloy material), which can absorb more than 80% of radial impact forces, improving impact resistance by 3 times compared with traditional ball bearings.
  • Axial drag reduction module: Equipped with a thrust bearing set (ceramic coating process), reducing the axial friction coefficient from 0.02 to 0.008 and lowering energy consumption by 15%.

2. Dynamic Preloading Adjustment Mechanism

  • Pin-shock block linkage: Eliminates axial clearance dynamically by squeezing the support arm through threaded or snap connections. Test data shows that the joint clearance remains ≤ 0.1mm after 1000 hours of continuous operation, which is better than the industry standard (0.2mm).
  • Elastic deformation compensation: The support arm is made of 6061-T6 aluminum alloy, which can withstand more than 500 reciprocating deformations without failure after special heat treatment, ensuring long-term stability.

3. Self-Lubricating Energy Storage Technology

  • Oil storage space design: Pre-fills nano-lubricating grease (base oil viscosity grade ISO VG 46) in the sliding bearing clearance, which can meet the requirement of continuous operation for 2000 hours without additional lubrication.
  • Oil migration control: Guides the directional flow of lubricant through a micro-groove structure to form a dynamic oil film when the joint rotates at high speed, reducing temperature rise by 8-12°C.

III. Technical Implementation: Integration of Precision Machinery and Material Technology

1. Modular Structure Design

  • U-shaped support arm nesting: Connecting rod 1 is inserted between the U-shaped arms of connecting rod 2, with drag reduction parts installed on both sides and a retaining part set clamped in the middle, connected and locked in series by a pin. This design reduces the number of parts by 30% and lowers manufacturing costs by 25%.
  • Application of lightweight materials: Key components use titanium alloy (Ti-6Al-4V) and carbon fiber reinforced polymer (CFRP), reducing the joint weight by 40% compared with traditional designs while maintaining the same strength.

2. Breakthroughs in Assembly Technology

  • Cold pressing forming technology: The sliding bearing and the support arm adopt an interference fit (interference amount 0.03-0.05mm), and are assembled by cold pressing at -80°C liquid nitrogen, ensuring the fit accuracy reaches IT5 grade.
  • Laser welding sealing: The oil storage chamber uses pulse laser welding (power 200W, frequency 50Hz), and the weld airtightness reaches 1×10