Bio-inspired swing leg control for spring-mass robots running on ground with unexpected height disturbance

Area of Science:

• Robotics
• Biomechanics
• Control Theory

Background:

• Animal running mechanics suggest prioritizing injury avoidance and efficiency over stability.
• Reducing motor size and structure weight is crucial for robot design.

Purpose of the Study:

• To propose and evaluate three swing leg control policies for spring-mass running robots.
• To optimize for structural capacity (damage avoidance) and efficiency in robot locomotion.
• To investigate the impact of different objective functions on running dynamics.

Main Methods:

• Inspired by ground running birds, three control policies were developed.
• Each policy regulates a specific objective function: peak leg force, axial impulse, or actuator work.
• Control policies adjust leg angle during the flight phase.

Main Results:

• All three control policies yielded nearly identical stance phase dynamics.
• Implementing any policy successfully regulated the targeted objective functions.
• A simple leg retraction with constant angular acceleration was sufficient.

Conclusions:

• The proposed control policies effectively balance damage avoidance and efficiency.
• Simple leg angle adjustments can achieve complex running objectives.
• Findings offer insights for designing lighter and more robust running robots.