Explosive Output to Enhance Jumping Ability: A Variable Reduction Ratio Design Paradigm for Humanoid Robot Knee Joint

Area of Science:

• Robotics
• Mechanical Engineering
• Biomechanics

Background:

• Enhancing explosive power in humanoid robot knee joints is crucial for agility and obstacle crossing.
• Current designs face limitations due to mismatched transmission ratios and power losses at high speeds, restricting jump performance.

Purpose of the Study:

• To introduce a novel variable-reduction-ratio knee-joint paradigm to overcome existing limitations.
• To improve the explosive power output and overall jump performance of humanoid robots.

Main Methods:

• Developed a variable-reduction-ratio knee-joint where the ratio decreases with joint angle during extension.
• Utilized a linear-actuator-driven guide-rod mechanism to implement the variable ratio strategy.
• Employed parameter optimization guided by explosive jump control for design selection.

Main Results:

• Experimental validation showed a 0.63 m jump height on a single-joint platform, a 31.9% theoretical improvement over fixed-ratio designs.
• Integration into a humanoid robot resulted in a 1.1 m long jump, 0.5 m high jump, and 0.5 m box jump.
• The variable ratio strategy effectively increased takeoff torque and extended the high-power operating window by limiting motor speed and power losses.

Conclusions:

• The proposed variable-reduction-ratio knee-joint paradigm significantly enhances humanoid robot jump performance.
• This design addresses the limitations of fixed-ratio systems, enabling greater agility and obstacle-crossing capabilities.
• The findings pave the way for more dynamic and capable humanoid robots in various applications.