A Survey on Design and Control Methodologies of High- Torque-Density Joints for Compliant Lower-Limb Exoskeleton

Area of Science:

• Robotics
• Biomechanics
• Mechanical Engineering

Background:

• Lower-limb assistance exoskeletons are vital for human augmentation.
• Exoskeleton joints require high torque and low weight for optimal function.
• Non-elastic quasi-direct actuation offers superior dynamic performance and reduced weight compared to elastic systems.

Purpose of the Study:

• To review and analyze the integrated design of lower-limb assistance exoskeleton joints.
• To identify developmental prospects for optimized exoskeleton joint performance.
• To explore advancements in actuation, motor technology, and control strategies.

Main Methods:

• Literature review and analysis of current exoskeleton joint designs.
• Comparison of elastic versus non-elastic actuation systems.
• Examination of permanent magnet synchronous motor (PMSM) applications in robotics.
• Discussion of compliant control algorithms (impedance, admittance).

Main Results:

• Non-elastic quasi-direct actuation is favored for its dynamic performance and lightweight characteristics.
• Permanent magnet synchronous motors are crucial for high-output torque and compact design.
• Optimizing torque density, ripple torque, efficiency, and thermal management are key for motor performance.
• Compliant control strategies enhance joint flexibility and human-robot interaction.

Conclusions:

• Integrated design approaches considering mechanism structure and control algorithms are essential.
• Future development should focus on optimizing these integrated aspects for superior exoskeleton performance.
• Advancements in actuation, motor technology, and control promise enhanced capabilities for lower-limb assistance exoskeletons.