Buckled Bistable Beam Actuation with Twisted Strings

Abstract

In this study, the use of the twisted string concept with a pin, serving as a moment arm, is proposed to produce the snap-through of a pre-compressed beam so that the whole system can be used as an effective on/off actuator. The twisted string mechanism is to produce a horizontal pulling force to the pin, which triggers the snap-through of the beam. The actuation moment required to trigger the bistable beam in this study is 24.3 Nmm, corresponding to a horizontal force of 0.81 N. The twisted string actuator is able to produce a pulling force of 1 N, which is further pulled through a distance of 5-mm. Static performance of the integrated system based on the effects of the length of the string on the required input motor voltage, torque, and the overall system response time is experimentally investigated. The snap-through sequence during the static experiment is also captured with a high-speed camera. The input voltage to the motor increases as the length of the string is increased. The length of the string also affects the overall system response, motor speed and torque. The whole snap-through of the beam happens within 100 msec after the trigger signal is sent.