@Article{ko:ar:2018a,
  author    = {Ko, Tianyi and Kaminaga, Hiroshi and Nakamura, Yoshihiko},
  title     = {Current-pressure-position triple-loop feedback control of electro-hydrostatic actuators for humanoid robots,Current-pressure-position triple-loop feedback control of electro-hydrostatic actuators for humanoid robots},
  journal   = {Advanced Robotics},
  year      = {2018},
  volume    = {32},
  number    = {24},
  pages     = {1269--1284},
  month     = {December},
  doi       = {https://doi.org/10.1080/01691864.2018.1555880},
  url       = {https://www.tandfonline.com/doi/pdf/10.1080/01691864.2018.1555880?needAccess=true},
  keywords  = {Actuator, EHA, hydraulic, force control, backdrivability},
  abstract  = {To overcome the tradeoff between torque density and response of the backdrivable actuators, actuation by electro-hydrostatic actuators (EHA) is effective. While their backdrivability and energy efficiency was shown in the previous studies, their closed-loop dynamic behavior was not discussed in detail. In this paper, we present the analysis and experimental evaluation of the force control performance of the electro-hydrostatic actuator for the humanoid robot ‘Hydra’. We first present a simplified model of EHA and show that EHA can be simplified as a mass-spring-damper model if all values such as pump torque/velocity and fluid pressure/flow-rate are expressed in the equivalent value seen from the actuator. We also show the comparison between the model and experimentally acquired open-loop dynamic behavior. Then, the evaluation on the force measurement and control performance is shown. The static friction on the rod-seal was 0.46\% of the maximum piston force, and with additional strain gauge information, the error can be reduced to 0.28\% of the maximum force. We also show that our developed EHA has a pressure control bandwidth of 100\hspace{0.167em}Hz in the fixed piston configuration, which is higher than other state-of-the-art series elastic actuators. In the last of paper, the joint level position and torque control performance of Hydra is examined.},
  publisher = {TAYLOR \& FRANCIS LTD},
  address   = {2-4 PARK SQUARE, MILTON PARK, ABINGDON OR14 4RN, OXON, ENGLAND}
}