The twisted string actuator is an actuator that
is gaining popularity in various engineering and robotics and
applications. However, the fundamental limitation of actuators
of this type is the uni-directional action, meaning that the
actuator can contract but requires external power to return to
its initial state. This paper proposes 2 novel passive extension
mechanisms based on buckling effect to solve the uni-directional
issue of the twisted string actuator. The proposed mechanisms
are mechanically simple and compact and provide a nearlyconstant
extension force throughout the operation range. The
constant force can fully extend the twisted string actuator
with minimal loss of force during contraction. The designed
mechanisms are evaluated in a series of practical tests, and
their performances are compared and discussed.
~ A combine work between KoreaTech and UCSB