Series elastic actuators (SEAs) incorporate a spring between the motor and output. Because of the physical compliance introduced by this spring, series elastic actuators are well suited for any sudden impacts during human-robot interaction. Unfortunately, this improvement in safety also introduces some control issues. In particular, the spring element limits the range of virtual environments which the robot can passively (i.e., safely) render.

My research on SEAs is centered on determining exactly what range of virtual environments the robot can passively display, and then increasing that range through applications of time domain control theory.

We hope that this research makes robots both safer and more capable when interacting with humans!

Publications on Series Elastic Actuators

  • D. P. Losey, A. Erwin, C. G. McDonald, F. Sergi, and M. K. O’Malley, “A time domain approach to control of series elastic actuators: Adaptive torque and passivity-based impedance control,” IEEE/ASME Transactions on Mechatronics, vol. 21, no. 4, pp. 2085-2096, 2016. PDF2016 IEEE/ASME Transactions on Mechatronics Best Paper Award.
  • D. P. Losey and M. K. O’Malley, “Effects of discretization on the K-width of series elastic actuators,” Proc. IEEE Int. Conf. on Robotics and Automation (ICRA), pp 421-426, 2017. PDF.

My peers within the MAHI Lab have recently developed new SEA hardware for rehabilitation and biomechanics applications. In the near future, we hope to combine the control and passivity research I have described here with their innovative designs!