Design and Experimental Characterization of a Niti-Based, High-Frequency, Centripetal Peristaltic Actuator

Development and experimental testing of a peristaltic device actuated by a single shape-memory NiTi wire are described. The actuator is designed to radially shrink a compliant silicone pipe, and must work on a sustained basis at an actuation frequency that is higher than those typical of NiTi actuators. Four rigid, aluminum-made circular sectors are sitting along the pipe circumference and provide the required NiTi wire housing. The aluminum assembly acts as geometrical amplifier of the wire contraction and as heat sink required to dissipate the thermal energy of the wire during the cooling phase. We present and discuss the full experimental investigation of the actuator performance, measured in terms of its ability to reduce the pipe diameter, at a sustained frequency of 1.5 Hz. Moreover, we investigate how the diameter contraction is affected by various design parameters as well as actuation frequencies up to 4 Hz. We manage to make the NiTi wire work at 3% in strain, cyclically providing the designed pipe wall displacement. The actuator performance is found to decay approximately linearly with actuation frequencies up to 4 Hz. Also, the interface between the wire and the aluminum parts is found to be essential in defining the functional performance of the actuator

A general method for the design and fabrication of shape memory alloy active spring actuators

Shape memory alloys have been widely proposed as actuators, in fields such as robotics, biomimetics and microsystems: in particular spring actuators are the most widely used, due to their simplicity of fabrication. The aim of this paper is to provide a general model and the techniques for fabricating SMA spring actuators. All the steps of the design process are described: a mechanical model to optimize the mechanical characteristic for a given requirement of force and available space, and a thermal model for the estimation of the electrical power needed for activation. The parameters of both models are obtained by experimental measurements, which are described in the paper. The models are then validated on springs manufactured manually, showing also the fabrication process. The design method is valid for the dimensioning of SMA springs, independently from the external ambient conditions. The influence on the actuator bandwidth was investigated for different working environments, providing numerical indications for the utilization in underwater applications. The spring characteristics can be calculated by the mechanical model with an accuracy of 5%. The thermal model allows one to calculate the current needed for activation under different ambient conditions, in order to guarantee activation in the specific loading conditions. Moreover, two solutions were found to reduce the power consumption by more than 40% without a dramatic reduction of bandwidth

Nitinol shape memory alloy spring

446-453Manufacturing, over the years, has evolved through three revolutions brought out by the impact of mechanization, electricity and Information Technology. The update in manufacturing has its root of intelligence. Necessity of miniaturization is shifted the use of conventional actuators with smart actuators. Conventional actuators generally produce the power in proportion to their volume, which reduce their application in micro applications. A concise review of the recent developments within nearly ten years on shape memory alloys has been presented. Besides other available shape memory alloys, Nitinol(Ni-Ti) is preferred due to its array of characteristicslike light weight, high power to weight ratio, noiseless operation, ease of actuation and muscle like movement. Shape memory effect and pseudo-elasticity play a crucial role in smart materials. Various actuation modes (Joule heating, hot water, laser assisted) and cooling methods are tabulated for Ni-Ti. The different forms of Nitinolare commercially available, but spring is used specially, due to its coiled structure

Nitinol shape memory alloy spring

Manufacturing, over the years, has evolved through three revolutions brought out by the impact of mechanization, electricity and Information Technology. The update in manufacturing has its root of intelligence. Necessity of miniaturization is shifted the use of conventional actuators with smart actuators. Conventional actuators generally produce the power in proportion to their volume, which reduce their application in micro applications. A concise review of the recent developments within nearly ten years on shape memory alloys has been presented. Besides other available shape memory alloys, Nitinol(Ni-Ti) is preferred due to its array of characteristicslike light weight, high power to weight ratio, noiseless operation, ease of actuation and muscle like movement. Shape memory effect and pseudo-elasticity play a crucial role in smart materials. Various actuation modes (Joule heating, hot water, laser assisted) and cooling methods are tabulated for Ni-Ti. The different forms of Nitinolare commercially available, but spring is used specially, due to its coiled structure

Development of a combined micro-macro mechanics analytical approach to design shape memory alloy spring-based actuators and its experimental validation

In this work, an analytical procedure for the preliminary design of shape memory alloy spring-based actuators is investigated. Two static analytical models are considered and interconnected in the frame of the proposed procedure. The first model, based on the works from An, is able to determine the material properties of the SMA components by means of experimental test data and is able to size the SMA component based on the requirements of the system. The second model, based on a work from Spaggiari, helps to design and size an antagonist spring system that allows one to obtain the geometric characteristics of springs (SMA and bias) and the mechanical characteristics of the entire actuator. The combined use of these models allows one to define and size a complex SMA actuator based on the actuation load requirements. To validate the design procedure, static experimental tests have been performed with the entire SMA actuator

Análise da morfagem de winglets utilizando ligas com memória de forma

The use of shape memory alloys (SMA) as actuators allows to build adaptive structures and to develop the concept of morphing. In the aeronautical industry, the morphing of aircraft is inspired by the flight of birds, as for the flaps and ailerons. Nowadays, the wing tips may have a static device called winglet that has an important aerodynamic function in cruise flight, but generates lift losses during take-off and landing. This work aims to analyze the winglet’s morphing using SMAs actuators. Two alternative models in bias configuration are presented: spring-pulley system and torsion springs system. Both models aim to represent conditions for application of a smallscale wing. This study shows a proof of concept and designs two prototypes for experimental verifications. Several parametric investigations evaluate the influence of air flow speed and the sensitivity of SMA wire diameter and spring index. The results show the conditions to obtain the desired geometric variation of the winglet and the feasibility of the actuation using SMA springs.A utilização das ligas com memória de forma (SMA) como atuadores possibilita a construção de estruturas adaptativas e o desenvolvimento do conceito de morfagem. No contexto aeronáutico, as morfagens em aeronaves são inspiradas no voo de aves, como é o caso dos flapes e ailerons. Atualmente, as pontas de algumas asas apresentam um dispositivo estático chamado de winglet, que possui uma função aerodinâmica importante no voo de cruzeiro, mas que ocasiona perdas na sustentação durante a decolagem e a aterrissagem. Este trabalho busca analisar a morfagem de winglets utilizando atuadores com SMAs. Apresentam-se dois modelos alternativos de atuação em configuração bias: sistema mola-polia e sistema com molas torcionais. Os dois modelos conceituais representam as condições de aplicação da asa em escala reduzida. O estudo apresenta duas provas de conceitos e constrói dois protótipos para verificações experimentais. Diversas investigações paramétricas avaliam a influência do escoamento do ar e da sensibilidade do diâmetro do fio SMA e índice de mola. Os resultados mostram as condições em que é possível obter a variação desejada da geometria do winglet e a capacidade de atuação a partir de molas SMA

An efficient drive, sensing, and actuation system using PZT stack actuator cells

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 81-82).The PZT cellular actuator developed in the MIT d'Arbeloff Laboratory utilizes small-strain, high-force PZT stack actuators in a mechanical flexure system to produce a larger-strain, lower-force actuator useful in robotic systems. Many functionalities for these cellular actuators are developed which can have great impact on robotic systems and actuation itself. After initial exploration into other possible circuitry, a circuit is designed to recovery unused energy for the PZT cells. The circuit design is formed around a proposed method of distributed actuation using PZT cells which imposes that different PZT cells will be activated during different periods such that the charge from some cells can be transferred to others. If the application allows actuation which can conform to this criteria, the developed circuit can be used which, without optimization, can save ~41% of the energy used to drive the actuators with a theoretical upper limit on energy efficiency of 100%. A dynamic system consisting of multiple PZT actuators driving a linear gear is analyzed and simulated which can achieve a no load speed 2.4 m/s with minimal actuators. Then, the two-way transforming properties of PZT stack actuators are utilized to allow dual sensing and actuation. This method uses an inactive PZT cell as a sensor. With no additional sensors, a pendulum system driven by antagonistic groups of PZT cells is shown to find its own resonance with no system model. These functionalities of charge recovery, distributed actuation, and dual sensing and actuation set the PZT cellular actuator as an important contribution to robotic actuation and begin to illuminate the possible impacts of the concept. The design and analysis described reveals many possibilities for future applications and developments using the PZT cellular actuator in the fields of actuation and robotics.by Patrick R. BarragánS.M

Estudio e implementación de actuadores basados en aleaciones SMA

El primer objetivo del proyecto es realizar un estudio de los sistemas de accionamiento actuales en manos robóticas y su evolución con el propósito de conocer sus características y prestaciones. El siguiente objetivo es realizar un estudio del estado del arte en relación al uso de aleaciones con memoria de forma en actuadores. Esto servirá para conocer las limitaciones de los actuales prototipos, identificar las posibles mejoras y obtener conclusiones acerca de la viabilidad del sistema de actuación que se quiere implementar. El siguiente objetivo es diseñar e implementar un prototipo que sirva como banco de pruebas para la investigación en actuadores basados en SMA. El prototipo deberá cumplir con unos requisitos mínimos como: dimensiones reducidas, alta precisión, bajo rozamiento y alta velocidad de adquisición de datos. Este prototipo estará formado por dos subsistemas: · Una estructura mecánica para dar soporte al cable de nitinol, sensor, polea, eje y el resto de elementos del accionamiento. · Un subsistema electrónico que incluye: - Etapa de potencia destinada a regular la corriente entregada al SMA. - Sensor de posición para leer la posición del eje. - Un microprocesador que se encargará de controlar el sistema y lograr que el eje siga las órdenes dadas por un PC. Por último, se utilizará el banco de pruebas desarrollado para la realización de unos estudios preliminares acerca del comportamiento dinámico de este tipo de actuadores. Será necesario comprobar la controlabilidad del sistema, analizar las limitaciones existentes y proponer mejoras futuras para perfeccionar el funcionamiento del actuador. El trabajo se divide en siete capítulos con el objetivo de introducir la tecnología utilizada, estudiar el estado del arte de dicha tecnología, explicar el diseño del prototipo, las pruebas realizadas y extracción de conclusiones. En el capítulo 1 actual, se realiza una introducción a las aleaciones con memoria de forma SMA y se desarrolla una pequeña evolución de las manos robóticas y sus sistemas de accionamiento. En el capítulo 2 se realiza un estudio del arte donde se resume la información y conocimientos adquiridos de los principales estudios e investigaciones realizados sobre el uso del nitinol como actuador. En el capítulo 3 se realiza una descripción general del sistema propuesto; se dedica un apartado para cada uno de los subsistemas. Así se explican las partes electrónica, mecánica y software necesarias para entender el sistema en detalle. En el capítulo 4 se explican las pruebas realizadas con el prototipo fabricado y se muestran las gráficas obtenidas que ayudan a conocer el funcionamiento del actuador. También se propone un regulador PID para control de la posición. En el capítulo 5 se desarrollan las conclusiones de todo el sistema, y se proponen las mejoras y consideraciones para las siguientes versiones del prototipo, así como qué aspectos fundamentales deben ser especialmente estudiados. En el capítulo 6 se muestran las hojas de características de los principales componentes electrónicos y mecánicos utilizados, útiles para una consulta rápida. En el último apartado, capítulo 7, se indican las referencias bibliográficas consultadas durante el desarrollo del proyecto.Ingeniería Industria

Diseño y aplicación de un actuador SMA en el control de manos robóticas

En el presente proyecto se propone un nuevo sistema de actuación para manos robóticas basado en la utilización de una aleación con memoria de forma tipo NiTi (níquel y titanio) llamada nitinol. Los actuadores de nitinol imitan el comportamiento de los músculos humanos, contrayéndose al calentarse, gracias al efecto de memoria de forma, y dilatándose al enfriarse. El calentamiento se consigue aplicando corriente eléctrica a los actuadores. Para demostrar la validez de este sistema de actuación se diseña un prototipo consistente en una estructura de metacrilato que sirve como soporte para los músculos artificiales y que puede sumergirse en una cubeta de refrigeración para mejorar los tiempos de actuación del nitinol. Esta estructura contiene seis músculos que están sujetos a los seis tendones de un dedo de la mano robótica de la compañía Shadow Robot Company. Para controlar el movimiento del dedo se utiliza un sistema electrónico que consiste en una serie de sensores de posición integrados en las articulaciones del dedo, un circuito que regula la corriente aplicada a los actuadores y un microcontrolador conectado a un PC que conjuntamente controlan la activación y desactivación de los músculos. Se presentan los resultados de las pruebas de caracterización y de control del sistema. Este proyecto forma parte de las actividades de desarrollo de uno de los paquetes de trabajo del Proyecto HANDLE.Ingeniería Técnica en Electrónic