Model based design of antagonistic shape memory alloy spring devices

Abstract

Shape memory alloy actuated devices employing a network of antagonistic components can reach an equilibrium of the internal forces by multiple sets of individual force magnitudes. In networks of star topologies particularly, the actuators are placed radially with one end connected at a common node. The ability to produce multiple sets of force equilibria suggests then that similar motions of the common node correspond to different thermomechanical paths. Two factors linked to this behavior are examined in this work, namely the initial design of the antagonistic system and the operational profile used during actuation. A shape memory alloy model is initially constructed based on an elementary hysteresis operator to produce a direct representation of the shape memory alloy behavior in the force–deformation plane. This description enables the identification of the operating point for the actuator by the geometric relationship of these models. In the second part, the placement of the antagonists is guided by the model based on specifications on the range of the workspace and the internal forces. The antagonistic operation is finally compared, in terms of time, work produced, and energy consumption, for a bang-bang (minimum time controller for the actuator) and a bang-off-bang (minimum internal forces for the system) actuation scheme.

Stress-dependent generalized Prandtl–Ishlinskii hysteresis model of a NiTi wire with superelastic behavior

“…Few phenomenological hysteresis models with stress dependency exist. In Kolyvas and Tzes (2018), a phenomenological model was used to formulate the stressdependency of a SMA spring device by utilizing the play operator. The model did not include the superelastic behavior of SMAs.…”

Effect of shape memory alloys partial transformation on the response of morphing structures encompassing shape memory alloy wire actuators

“…In the work of Antonello et al (2014), two SMA antagonistic actuator wires are considered as a load positioning system and a model to describe its behavior is postulated based on the correlation of the actuators’ electrical resistance with produced movements. Recently, Kolyvas and Tzes (2018) published a model-based design approach for antagonistic SMA spring devices where the consideration of a generalized elasto-plastic operator permits the formation of distinguished PT cycles inside the major loop.…”

Thermomechanically coupled analysis and experimental investigation of morphing structures with shape memory alloy actuators operating under partial transformation with a focus on active load control

“…In the work of Antonello et al [312], two SMA antagonistic actuator wires were considered as a load positioning system and a model to describe its behaviour was postulated based on the correlation of the actuators' electrical resistance with produced movements. Recently, Kolyvas and Tzes [313] published a model-based design approach for antagonistic SMA spring devices where the consideration of a generalized elasto-plastic operator permited the formation of distinguished PT cycles inside the major loop.…”