Design and Control of a Polycentric Knee Exoskeleton Using an Electro-Hydraulic Actuator.

Area of Science:

• Robotics
• Biomechanics
• Control Systems

Background:

• Exoskeleton robots require high energy efficiency, load capacity, and comfort.
• Current designs often lack anatomical complexity, leading to stiffness and inefficiency.
• Simple 1-DoF structures, common in knee exoskeletons, cause wearer-robot misalignment.

Purpose of the Study:

• To develop a polycentric knee exoskeleton structure minimizing wearer-robot misalignment.
• To improve energy efficiency and load capacity using an electro-hydraulic actuator (EHA).
• To design a robust sliding mode controller for the EHA system.

Main Methods:

• Designed a 1-DoF polycentric knee exoskeleton structure.
• Integrated an electro-hydraulic actuator (EHA) for improved performance.
• Developed and verified a sliding mode controller using Simulink and experimental validation.
• Utilized an optical rotary encoder for primary feedback sensing.

Main Results:

• The polycentric structure effectively reduced misalignment and improved torque transfer.
• The EHA offered better energy efficiency and load capacity compared to conventional actuators.
• The sliding mode controller demonstrated effective control despite system uncertainties.
• The experimental results validated the system's ability to reach target values accurately.

Conclusions:

• The proposed polycentric knee exoskeleton with EHA and sliding mode control offers a promising solution for enhanced performance.
• This integrated system addresses key limitations of conventional exoskeleton designs.
• The approach facilitates more efficient and comfortable human-robot interaction in exoskeleton applications.