Modeling and simulation of a compact push–pull rubber actuator energized by an outer coil of shape memory wire

This paper introduces the concept and develops the theory for a push–pull actuator made by winding a thin shape memory wire on a solid rubber cylinder. The incompressibility of the rubber converts the thermomechanical contraction of the heated wire in twice as much axial strain available in the rubber core. The intrinsic elastic backup provided by the core allows push–pull action of the device. Based on the assumption of both material and geometric linearity, a simple theoretical model is developed, which culminates in a simple closed-form equation for the output stroke of the actuator. The theoretical predictions closely agree with refined finite element simulations, anticipating a net stroke of about 5–6% of the overall actuator length, depending on the outer load applied. The working principle of the actuator and the accuracy of the model are validated by tests on a proof-of-concept prototype

Lezioni di progetto di sistemi meccatronici

Questo libro raccoglie le lezioni del corso di Progetto di Sistemi Meccatronici tenuto dagli autori agli allievi ingegneri meccatronici presso la Facoltà di Ingegneria di Reggio Emilia. Il corso ha come oggetto il processo di progettazione del prodotto industriale, con particolare riferimento alle seguenti fasi: - Raccolta e interpretazione dei bisogni del cliente - Definizione di specifiche tecniche oggettive e misurabili - Generazione di soluzioni concettuali ai problemi tecnici - Confronto critico di concetti alternativi - Scelta del concetto migliore - Trasformazione del concetto in un prodotto concreto - Progettazione della sicurezza e dell’affidabilità del prodotto Grazie alla struttura sintetica e all’esposizione sistematica di casi reali applicativi, il testo è indicato anche per i progettisti e per le aziende che vogliono intraprendere la progettazione strutturata di prodotto in ottica cliente

Design and Characterization of a Continuous Rotary Minimotor Based on Shape-Memory Wires and Overrunning Clutches1

An attractive but little explored field of application of the shape-memory technology is the area of rotary actuators, in particular for generating endless motion. This paper presents a miniature rotary motor based on shape-memory alloy (SMA) wires and overrunning clutches, which produces high output torque and unlimited rotation. The concept features an SMA wire tightly wound around a low-friction cylindrical drum to convert wire strains into large rotations within a compact package. The seesaw motion of the drum ensuing from repeated contraction-elongation cycles of the wire is converted into unidirectional motion of the output shaft by an overrunning clutch fitted between drum and shaft. Following a design process developed in a former paper, a six-stage prototype with size envelope of 48 × 22 × 30 mm is built and tested. Diverse supply strategies are implemented to optimize either the output torque or the speed regularity of the motor with the following results: maximum torque = 20 Nmm; specific torque = 6.31 × 10-4 Nmm/mm3; rotation per module = 15 deg/cycle; and free continuous speed = 4.4 rpm