Effect of Low-Pass Filtering on Passivity and Rendering Performance of Series Elastic Actuation

Area of Science:

• Robotics
• Control Systems Engineering
• Human-Computer Interaction

Background:

• Series Elastic Actuation (SEA) is crucial for safe and compliant robotic systems.
• Velocity-Sourced Impedance Control (VSIC) is used for rendering virtual environments.
• Ensuring system passivity is vital for stability and safety in control systems.

Purpose of the Study:

• To analyze the impact of low-pass filtering on SEA passivity and performance under VSIC.
• To derive conditions for maintaining passivity with filters in the control loop.
• To compare the performance of filtered versus unfiltered control systems.

Main Methods:

• Analytical derivation of passivity conditions for SEA with VSIC and filters.
• Development of passive physical equivalents for closed-loop systems.
• Experimental verification of theoretical findings.

Main Results:

• Low-pass filtering of velocity feedback amplifies noise, necessitating force controller filtering.
• Filtering improves rendering performance by reducing parasitic damping and allowing higher gains.
• Filtering introduces stricter bounds on passively renderable stiffness.

Conclusions:

• Low-pass filtering offers performance benefits in SEA-based virtual environments but requires careful consideration of stiffness limitations.
• The study provides a framework for understanding and optimizing filtered control in SEA systems.
• Experimental validation confirms the trade-offs between performance enhancement and stiffness rendering bounds.