Design equations for binary shape memory actuators under dissipative forces

Spinella, Igor; Dragoni, Eugenio

doi:10.1243/09544062jmes1232

Cited by 20 publications

(18 citation statements)

References 10 publications

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“…The minimum value of s F can be determined by fixing the maximum allowable wire diameter, d 1 , of the SMA element. This maximum value can be determined, for example, using cooling time considerations, the bigger the wire, the slower the cooling, [8], [18]. Combining expression (11) with (1) and (3), the following relationship can be used to determine the minimum value of s F .…”

Section: Embodiment Of Sma Actuatormentioning

confidence: 99%

“…Furthermore, the force delivered by shape memory actuators varies linearly with the displacement while the external load is usually constant. The design of a SMA actuator ensures that the minimum actuator force is sufficient to contrast the external load [18], providing an additional cause of stroke reduction.…”

Section: Design Of Compensated Sma Actuatorsmentioning

confidence: 99%

“…Eq. (18) shows that the pre-stretch of the system, p, acts on the stroke, Δx, as a pure gain. Figure 12a s , of parameter s 2 which maximizes the normalized stroke.…”

Section: Performances Of the Uncompensated Sma Actuatorsmentioning

confidence: 99%

“…behaviour as a linear one [18] (Figure 1a). This behaviour is by no means obvious, thus an explanation is needed.…”

Section: Introductionmentioning

confidence: 97%

“…Among the proposed actuator there is lack of simple design instruments to provide basic information to the designer, either due to specific constraints of application or due to the high complexity of the thermomechanical material models used. In order to answer for an analytical design methodology, the author described in several technical publications a set of equations useful for linear [18] and rotary application [19]. The authors developed the design equations both for SMA actuators under a general system of external forces [20] and produced the design formulae to increase the output stroke thanks to negative stiffness compensators [21].…”

mentioning

confidence: 99%

See 4 more Smart Citations

Optimum Mechanical Design of Binary Actuators Based on Shape Memory Alloys

Spaggiari¹,

Mammano²,

Dragoni³

2012

Smart Actuation and Sensing Systems - Recent Advances and Future Challenges

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Many SMAs applications have been studied in recent years. Kuribayashi [5] proposes a rotary joint based on a bending SMA actuator, while, in [6] design and applications of SMA Smart Actuation and Sensing Systems -Recent Advances and Future Challenges 4 actuators are presented. Microrobots can be developed using SMA as shown in [7] where there is a basic method to design the SMA spring based on a thermo-electromechanical approach. Reynaerts et al. [8] present design considerations concerning the choice of the active element to evaluate SMA actuator efficiency. Lu et al. [9] design a high strain shape memory actuator taking into account pseudoplasticity and compared its performance with traditional actuators. Due to SMA high non linearity, design curves relying on experiments are proposed in [10] to assess the SMA actuator geometry. A comprehensive review of applications of SMAs in the field of mechanical actuation has recently been published in [11]. Jansen et al [12] develop a linear actuator used as a drive module in an angular positioning mini-actuator. This architecture allows both large force and long strokes to be obtained. Strittmatter et al. [13] propose a SMA actuator for the activation of a hydraulic valve, biased by a conventional spring. Bellini et al. [14] propose a linear SMA actuator able to vary the air inflow for internal combustion engines, improving gas combustion and leading to higher efficiency. Haga et al. [15] propos a mini-actuator to be used in Braille displays. Elwaleed et al.[16] develop a SMA beam actuator able to amplify the SMA actuator strain using elastically instable beams. Among the proposed actuator there is lack of simple design instruments to provide basic information to the designer, either due to specific constraints of application or due to the high complexity of the thermomechanical material models used. In order to answer for an analytical design methodology, the author described in several technical publications a set of equations useful for linear [18] and rotary application [19]. The authors developed the design equations both for SMA actuators under a general system of external forces [20] and produced the design formulae to increase the output stroke thanks to negative stiffness compensators [21]. Moreover two peculiar systems were designed and developed: a telescopic actuator [22] and a wire on drum system [23]. The present work reviews and improves the design rules developed by the authors and set them in a coherent formal analytical framework. Design examples are provided to illustrate the step-by-step application of the design optimization procedures for realistic case studies. Challenges and issues in SMA actuators designThe three main challenges in SMA actuator design are: obtaining a simple and reliable material model, increasing the stroke of the actuator and finding design equations to guide the engineer in dimensioning the actuator. To design SMA actuators, a material model must describe the mechanical behaviour of the alloy in two temperature ranges: b...

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Section: Embodiment Of Sma Actuatormentioning

confidence: 99%

Section: Design Of Compensated Sma Actuatorsmentioning

confidence: 99%

“…Eq. (18) shows that the pre-stretch of the system, p, acts on the stroke, Δx, as a pure gain. Figure 12a s , of parameter s 2 which maximizes the normalized stroke.…”

Section: Performances Of the Uncompensated Sma Actuatorsmentioning

confidence: 99%

“…behaviour as a linear one [18] (Figure 1a). This behaviour is by no means obvious, thus an explanation is needed.…”

Section: Introductionmentioning

confidence: 97%

mentioning

confidence: 99%

See 3 more Smart Citations

Optimum Mechanical Design of Binary Actuators Based on Shape Memory Alloys

Spaggiari¹,

Mammano²,

Dragoni³

2012

Smart Actuation and Sensing Systems - Recent Advances and Future Challenges

View full text Add to dashboard Cite

show abstract

Conceptual Design and Simulation of a Compact Shape Memory Actuator for Rotary Motion

Spinella

Mammano

Dragoni

2009

J. of Materi Eng and Perform

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This work describes the conceptual design, the modelling, the optimization, the detail design and the virtual testing of a shape memory actuator purposely conceived to maximize torque and angular stroke while limiting overall size and electric consumption. The chosen design, achieved by means of a Quality Function Deployment approach, features a fully modular concept in which an arbitrary number of identical modules are assembled to produce the desired angular stroke and output torque. The basic module contains shape memory springs that actuate the device and also a conventional spring that reduces the torque ripple. Following the concept generation stage, a thermo-electromechanical model is developed and a numerical optimization performed, aimed at minimizing the electrical consumption of the actuator. Finally, the device is designed in detail and the actuator is tested virtually. Thanks to the proposed modular construction and the use of a conventional balancing spring, the device shows better performances than known rotary shape memory actuators in terms of rotation, torque and customization.

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Design of a Telescopic Linear Actuator Based on Hollow Shape Memory Springs

Spaggiari

Spinella

Dragoni

2011

J. of Materi Eng and Perform

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Shape memory alloys (SMAs) are smart materials exploited in many applications to build actuators with high power to mass ratio. Typical SMA drawbacks are: wires show poor stroke and excessive length, helical springs have limited mechanical bandwidth and high power consumption. This study is focused on the design of a large-scale linear SMA actuator conceived to maximize the stroke while limiting the overall size and the electric consumption. This result is achieved by adopting for the actuator a telescopic multi-stage architecture and using SMA helical springs with hollow cross section to power the stages. The hollow geometry leads to reduced axial size and mass of the actuator and to enhanced working frequency while the telescopic design confers to the actuator an indexable motion, with a number of different displacements being achieved through simple on-off control strategies. An analytical thermo-electro-mechanical model is developed to optimize the device. Output stroke and force are maximized while total size and power consumption are simultaneously minimized. Finally, the optimized actuator, showing good performance from all these points of view, is designed in detail.

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Design equations for binary shape memory actuators under dissipative forces

Cited by 20 publications

References 10 publications

Optimum Mechanical Design of Binary Actuators Based on Shape Memory Alloys

Optimum Mechanical Design of Binary Actuators Based on Shape Memory Alloys

Conceptual Design and Simulation of a Compact Shape Memory Actuator for Rotary Motion

Design of a Telescopic Linear Actuator Based on Hollow Shape Memory Springs

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