Compact Series Visco-Elastic Joint (SVEJ) for Smooth Torque Control

Area of Science:

• Robotics
• Mechanical Engineering
• Materials Science

Background:

• Traditional robotic joints often lack inherent damping and compliance, posing safety risks during human interaction.
• Developing cost-effective and compact solutions for safe human-robot collaboration is a key challenge in robotics.

Purpose of the Study:

• To design and control a novel series-viscous-elastic joint (SVEJ) with integrated damping and compliance.
• To evaluate the performance of the SVEJ for applications in exoskeletons, cooperative robots, and haptic devices.

Main Methods:

• The SVEJ was constructed using 3D printed components and nonlinear elastic silicone springs.
• The system was modeled using the Neo-Hookean material model and experimentally characterized.
• A proportional torque controller was implemented and tested for bandwidth, transparency, impedance rendering, and stability.

Main Results:

• The SVEJ exhibits inherent damping from silicone springs, enabling simpler and more stable control.
• The joint can bear approximately 4.5 Nm torque at a 20-degree deformation angle.
• Achieved bandwidth ranged from 6.9 to 9.9 Hz, demonstrating nonlinear behavior.
• Satisfactory results were obtained for bandwidth, transparency, impedance rendering, and stability.

Conclusions:

• The developed SVEJ is a compact, cost-effective solution for introducing controlled compliance and damping in robotic systems.
• The SVEJ functions as a torque sensor, enhancing safety in human-robot interaction by providing a compliant interface.
• The design and control strategy are well-suited for integration into various robotic platforms, including exoskeletons and haptic devices.