Design and validation of an alignment free adaptive joint torque measurement system.

Purpose: This study introduces a transferable alignment-free adaptive joint torque measurement (AFAJTM) system designed to resolve inconsistencies in torque measurements caused by misalignment between dynamometer and joint rotational axes, improving accuracy and reliability in joint torque assessment.

Method: This study presents the design and control methodology of an alignment free adaptive joint torque measurement system. An elbow joint torque measurement device (EJTMD) was developed, and its torque consistency and repeatability were evaluated at various misalignment positions using a joint simulation model. Clinical experiments compared torque measurements between the EJTMD and a traditional standard dynamometer during maximum voluntary contraction (MVC) tests at different misalignment positions.

Result: The simulation test results demonstrate that the AFAJTM system can achieve high-precision torque measurements, with measurement errors controlled within ± 0.5 Nm at various misalignment positions. Clinical experiment data show that the EJTMD exhibits high consistency in torque measurements compared to the traditional standard dynamometer across five different misalignment positions, with strong repeatability and reliability.

Conclusion: The AFAJTM system provides a novel solution for joint torque measurement under human-machine axis misalignment conditions, a solution that eliminates the need for axis alignment, effectively overcoming the limitations of traditional measurement devices. This system can be widely applied in various devices that require joint torque measurement, demonstrating excellent adaptability and high-precision measurement capabilities.