  The increasing need for sharing workspace and interactive physical tasks
between robots and humans has raised concerns regarding safety of such
operations. In this regard, controllable clutches have shown great potential
for addressing important safety concerns at the hardware level by separating
the high-impedance actuator from the end effector by providing the power
transfer from electromagnetic source to the human. However, the existing
clutches suffer from high power consumption and large-weight, which make them
undesirable from the design point of view. In this paper, for the first time,
the design and development of a novel, lightweight, and low-power
torque-adjustable rotary clutch using electroadhesive materials is presented.
The performance of three different pairs of clutch plates is investigated in
the context of the smoothness and quality of output torque. The performance
degradation issue due to the polarization of the insulator is addressed through
the utilization of an alternating current waveform activation signal. Moreover,
the effect of the activation frequency on the output torque and power
consumption of the clutch is investigated. Finally, a time-dependent model for
the output torque of the clutch is presented, and the performance of the clutch
was evaluated through experiments, including physical human-robot interaction.
The proposed clutch offers a torque to power consumption ratio that is six
times better than commercial magnetic particle clutches. The proposed clutch
presents great potential for developing safe, lightweight, and low-power
physical human-robot interaction systems, such as exoskeletons and robotic
walkers.
