Improvement in rotational performance by periodic tensile change of a torque transmission wire: basic experimental verification using a single straight wire.

A parallel-wire driven system has the drawback of a narrow rotation range. To overcome this problem, this paper focuses on a 'torque wire', which consists of inner and outer wires and can transmit the inner wire rotation; the utilization of torque wires is effective in increasing the rotational range. However, significant degradation of the rotational transmission-accuracy is observed when a constant tension is applied to a torque wire. This degradation is attributed to the load in the tensile direction, which causes an increase in Coulomb friction at the sliding parts and an increase in the elastic torsion of the inner wire. Collectively defining the Coulomb friction and elastic torsion as a 'disturbance', this paper proposes a technique to suppress the disturbance and improve the rotational accuracy. This method applies a periodic change in tension to the torque wire. However, periodic tension induces lateral vibration due to parametric excitation. Thus, the amplitude and frequency of the torque wire are applied in several combinations for periodic tension as a preliminary experiment; the best combinations of amplitude/frequency with small lateral vibration are selected. The lateral vibration results are evaluated after Strutt-diagram-analysis. By using selected combinations, the usefulness of the method is experimentally confirmed. [ABSTRACT FROM AUTHOR]