A novel method to assess angle sensor performance for wearable exoskeletal joint kinematics.

Area of Science:

• Biomechanics
• Robotics
• Biomedical Engineering

Background:

• Joint range of motion (ROM) is crucial for motor function and clinical assessment.
• Traditional static goniometers are limited; dynamic measurement is needed for wearable systems.
• Wearable devices like exoskeletons and orthoses require accurate joint angle sensing.

Purpose of the Study:

• To present a novel methodology for assessing angle sensor performance in wearable joint measurement.
• To compare various off-the-shelf and custom sensors for articulated ankle-foot orthoses (AFOs).
• To provide a cost-benefit analysis for sensor selection in exoskeletal systems.

Main Methods:

• Developed a novel methodology to assess angle sensor performance dynamically and statically.
• Evaluated multiple angle sensors, including optical encoders, resistive potentiometers, and anisotropic magnetoresistive (AMR) sensors.
• Conducted static and dynamic error tests and a cost-benefit analysis.

Main Results:

• All tested sensors reported angular errors below 5°.
• Optical encoders demonstrated the highest accuracy (<0.7°) and precision.
• Resistive potentiometers showed the highest dynamic errors (1.5°–4°).
• The AMR sensor offered the best performance-to-cost ratio.

Conclusions:

• Accurate dynamic joint angle measurement is feasible with current sensor technology for wearable applications.
• Sensor selection depends on balancing accuracy, precision, cost, and specific application needs.
• The AMR sensor is a cost-effective option for many wearable joint measurement applications.