Design of a Shape Memory Alloy Actuated Compliant Smart Structure: Elastica Approach

Abstract

Large displacement static analysis of a fully compliant spatial mechanism is presented here. This mechanism is made up of a superelastic nitinol pipe as its compliant structural member and actuated by three shape memory alloy (SMA) wires. The coupled effect of the force developed by the SMA actuation and the force required for elastica deflection is simplified by incorporating the geometric parameters of the mechanism using a deflection plane approach. An iterative algorithm with elliptical integration has been developed, which is suitable for a wider range of actual and arbitrary inputs. The solutions are obtained for the effect of one-wire and two-wire actuation methods. Results obtained from the deflection plane approach and simulation have been compared and found that the relative error is less than 1% within the safe operating range of 5% strain value recommended for SMA actuators. Based on the analytical and simulation inputs, the mechanism is miniaturized further with the aim of increasing its workspace and is fabricated for further experimental investigations.

B-spline goal-oriented error estimators for geometrically nonlinear rods

“…Examples of these problems include framed structures [36,37], compliant mechanisms [11,44] and nanoscale structures [45]. The simplest geometrically nonlinear bending theory of planar elastic rods is the Elastica theory, mathematically formulated by L. Euler in 1744 [31].…”

Application of trained NiTi SMA actuators in a spatial compliant mechanism: Experimental investigations

“…The relationship between SMA actuation force and tilt angle of the platform obtained from the earlier analytical approach [7] is compared with the experimental results obtained by fixing the trained and untrained SMA wires in the mechanism and presented in Fig. 14. This result is obtained for the effect of actuating one wire.…”

“…[7]. The theoretical models for the large displacement of the moving platform, based on elastica approach, were obtained for the selective actuation of one wire and two wires at a time.…”

“…Comparison of results obtained from theoretical work[7] and experimental investigation: (a) force vs. tilt angle; (b) relative error (force vs. cL)-after training; and (c) relative error (force vs. cL)-before training.…”

Monolithic Six-DOF Parallel Positioning System for High-precision and Large-range Applications

“…Compliant positioning systems are driven by different kinds of actuation principles and they play an important role in the design and applications of these kinds of systems. Electromagnetic actuator (EMA) [15]- [17], electrostatic actuator (ESA) [18], electrothermal actuator (ETA) [19], [20], shaped memory alloy (SMA) [21], and piezoelectric actuator (PEA) [22], [23] are among famous actuation principles that have been utilized in the compliant positioning systems. Among the abovementioned principles, the PEA has been widely used due to offering many important advantages including extremely fine resolution, large force generation, fast response, high bandwidth frequency, high electrical-mechanical power conversion efficiency, and small size.…”