Effect of Vibration on Twisted String Actuation Through Conduit at High Bending Angles

This paper studies an effect of vibration on twisted string actuation through conduit at high bending angles. In our previous work [1], we have demonstrated that twisted string actuators can be used to transmit power even at significant deflection angles of the conduit. However, several undesirable effects, namely pull-back, hysteresis, and chattering, were present during actuation due to friction between strings and the internal sheath of the conduit. This paper reports the results of experimental study on effects of vibration on twisted string actuation inside deflected conduits. We have demonstrated that applying vibration generated near natural frequency of the system during the later stages of twisting and untwisting cycles helped reduce pull-back and hysteresis and increase string contraction. In case when sheath was deflected by 180° under a constant load of 3 kg, we were able to achieve over 70% decrease in pull-back and 30% decrease in hysteresis, compared with no vibration case.