Modeling, design, and optimization of Mindwalker series elastic joint

Area of Science:

• Robotics and Biomechanics
• Mechanical Engineering
• Wearable Technology

Background:

• Weight and power limitations hinder the practical daily use of wearable exoskeletons.
• Achieving lightweight, efficient, and powerful actuation systems presents significant engineering challenges.
• Selecting optimal combinations of existing technologies (battery, gear, motor) is complex.

Purpose of the Study:

• To propose an optimization framework for selecting efficient and lightweight exoskeleton joint drivetrain components.
• To develop and test a novel series elastic actuator for the Mindwalker exoskeleton joint.
• To generalize the optimization framework for similar applications.

Main Methods:

• Developed a power-based quasi-static model for exoskeleton joint drivetrains.
• Designed and implemented a novel series elastic actuator using a ballscrew-driven linear actuator and a double spiral spring.
• Tested the performance of the actuator, including power output, torque, linearity, and bandwidth.

Main Results:

• The proposed framework identifies efficient and lightweight component combinations.
• The novel series elastic actuator achieves 960 W power and 100 Nm peak torque.
• The integrated exoskeleton joint weighs 2.9 kg and demonstrates high torque bandwidth (>6 Hz at 100 Nm) and high-frequency response (>38 Hz at 2 Nm).

Conclusions:

• The optimization framework provides a systematic approach to designing efficient and lightweight exoskeleton actuation systems.
• The developed series elastic actuator significantly improves the power-to-weight ratio and performance of wearable exoskeletons.
• The Mindwalker exoskeleton joint represents a substantial advancement in wearable robotic technology for enhanced daily use.