Experimental validation of forward- and back-drivable characteristics on series clutch actuators using acceleration control

The development of a geared motor plus a clutch system is known as a human-friendly actuator, and many studies on clutch actuation systems have been conducted. Such system has high backdrivability and torque limitation, which are major advantages compared with a unit geared motor. These studies are divided into two groups. An input motor is velocity-controlled as a constant velocity source and it is regulated to generate output torque as a torque source. This study falls under the latter group. A control plant of the latter group has two operational modes, which has caused by the intrinsic clutch characteristics. To avoid switching operational modes and to achieve robustness against disturbances, an observer-based control technique using acceleration control has been proposed. However, forward- and back-drivable characteristics of the system have not been discussed yet. These characteristics are important for control of physical human-robot interaction, and therefore, in this study, transfer functions of the characteristics of the proposed system are derived and experimental evaluation of the system is conducted.