Residual-Based External Torque Estimation in Series Elastic Actuators Over a Wide Stiffness Range: Frequency Domain Approach

This letter presents an enhanced external torque estimation algorithm for series elastic actuators (SEAs) expanding the usability of the residual-based technique. Although the residual method demonstrates online torque estimation capability in diverse applications and thus becomes popular, it is practically challenging to achieve accurate estimation performance in a wide stiffness range of SEAs. The performance degradation is mainly induced by inaccurate transmission torque information, which is stemmed from unexpected errors in the spring deflection based torque sensing. To overcome the issue, this letter analyses the limitation of the conventional approach in frequency domain and proposes the enhanced residual to be used over a wide stiffness range of SEAs. The performance of proposed method is comparatively verified with conventional method in the both of simulations and experiments.