Development of shape memory alloy actuator. (Improvement of output performance by the introduction of a .SIGMA.-mechanism):(Improvement of output performance by the introduction of a σ-mechanism)

概要

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The shape memory effect is based on a peculiar principle named Thermal Elastic Martensitic Transformation, and it shows a kind of elastic behavior. As a results, the conventional type shape memory alloy (SMA) actuator using circular pulley exhibits an undesirable characteristics, namely the dependence of the maximum output torque to the deformation of SMA or the angular displacement. This characteristics limits motion range of the SMA actuator and an amount of torque to be produced.<BR>The paper firstly clarifies above mentioned problem which the SMA intrinsically possesses and then proposes a new joint mechanism for articulated link structure named "σ-mechanism". The σ-mechanism is to decrease the moment arm according as the amount of the traction force of SMA increases by using non circular shaped pulley. The detailed algorithm to design the proposed σ-mechanism is then discussed. The validity of the proposed σ-mechanism is experimentally demon-strated by driving experiments of the SMA actuator model.
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