基于SMA的关节驱动器的力学分析及控制

分析了一种用于水下微小型仿生机器人的形状记忆合金(SMA)关节驱动器的力学特性,并通过模糊控制的方法对其进行了实验研究。结果表明:对于物理特性呈非线性、温度滞后、时变和受温度影响很大的SMA驱动器来说,采用模糊控制的方法,能够使驱动器稳定、平滑的工作,尽管产生了轻微的超调现象,但收到了令人较为满意的效果。因此,将模糊控制方法应用于SMA驱动器的控制有一定的理论意义和应用价值。     

一种基于SMA的摆动式驱动器驱动原理及实验

在分析了形状记忆合金(SMA)弹簧电热驱动原理的基础上,对一种差动式关节型SMA驱动器进行了实验研究。实验结果表明:驱动电流和冷却条件对驱动器的摆动周期有很大的影响,增大电流会显著提高SMA驱动器的动作频率,但电流过大,易使SMA失去形状记忆功能,所以,电流应控制在一定的范围之内。驱动器的动作频率还受到冷却速度的制约,加快冷却速度也会提高驱动器的动作频率。     

Linear spectral mixture analysis of Landsat TM data for monitoring invasive exotic plants in estuarine wetlands

This study assessed the feasibility of spectral mixture analysis (SMA) of Landsat thematic mapper (TM) data for monitoring estuarine vegetation at species level. SMA modelling was evaluated, using χ² test, by comparing SMA fraction images with a precisely classified QuickBird image that has a higher spatial resolution. To clearly understand the strengths and weaknesses of SMA, eight SMA models with different endmember combinations were assessed. When the TM data dimension for SMA and the endmember number required were balanced, a model with three endmembers representing water and two vegetation types was most accurate, whereas a model with five endmembers approximated the actual surface situation and generated a relatively accurate result. Our results indicate that an SMA model with appropriate endmembers had relatively satisfactory accuracy in monitoring vegetation. However, errors might occur in SMA fraction images, especially in models with an inappropriate endmember combination, and the errors were mainly distributed in areas filled with water or near water. Therefore, short vegetation usually submerged during high tide tended to be poorly predicted by SMA models. These results strongly suggest that tide water has a great influence on SMA modelling, especially for short vegetation.     

基于电阻反馈的 SMA 控制系统设计

形状记忆合金（SMA）驱动器在生物医疗中得到了广泛应用。目前,SMA 驱动器的控制器多采用外部传感反馈方式,体积大,应用受到限制。提出一种基于 SMA 内部电阻反馈的嵌入式控制电路。使用 ATMEGA16单片机搭建了 SMA 驱动器加热控制电路及恒流源电桥方法的电阻测量采集电路。实验表明：该控制系统可以产生可控 PWM,恒流源电桥方法测 SMA 电阻可以得到足够的测量精度,系统可用于 SMA 驱动器的控制。     

一种微小型蠕动机器人的步态分析

介绍了一种形状记忆合金(SMA)驱动的微型蠕动机器人的结构和工作原理,并对蠕动机器人的直线运动原理和转弯运动原理分别进行了详细的分析和论述。此外,还通过详细的实验对蠕动机器人步距与SMA驱动器电流的关系、蠕动机器人转弯角度与SMA驱动器电流的关系,以及蠕动机器人响应速度与SMA驱动器电流的关系进行了分析,并确定了SMA驱动器的加热电流。     

A new method for actuating parallel manipulators

This paper presents a new technique of actuating a parallel platform manipulator using shape memory alloy (SMA). This is a type of smart materials that can attain a high strength-to-weight ratio, which makes them ideal for miniature application. The work is mainly to develop a new SMA actuator and then incorporating the actuator in building the parallel manipulator prototype. The SMA used in this study is a commercial NiTi wire. The SMA wire provides an actuating force that produces a large bending and end displacement. A 3-UPU (universal–prismatic–universal) parallel manipulator using linear SMA actuators was developed. The manipulator consists of a fixed platform, a moving platform and three SMA actuators. The manipulator workspace was specified based on the restrictions due to actuator strokes and joint angle limits. System identification techniques were used to model both heating and cooling processes. An ON/OFF control was performed and the results showed closeness in simulation and experimental results. This study showed that shape memory alloy actuated beam can successfully be used to provide linear displacement. The built prototype indicates the feasibility of using SMA actuators in parallel manipulators.     

Modeling of shape memory alloy shells for design optimization

A three-dimensional phenomenological constitutive model for the analysis and design optimization of shape memory alloy (SMA) structures is presented. This model specifically targets the pseudoelastic behavior due to the R-phase transformation in NiTi alloys, but also applies to similar SMA materials with low hysteresis. A history-independent formulation is presented, which allows cost-effective sensitivity analysis. The possibility to efficiently compute design sensitivities is essential for enabling the use of gradient-based optimization algorithms, which will allow design optimization of complex SMA structures. The use of the constitutive model in a problem of realistic complexity is illustrated by the analysis of a SMA miniature gripper, modeled using shell elements. The sensitivity analysis of SMA structures using the presented model is addressed in an accompanying paper.     

SMA与PMMA共混物相容性的分子模拟研究

综合应用Ｆｌｏｒｙ－Ｈｕｇｇｉｎｓ理论、二元相互作用模型匠心 ＳＭＡ＝ＰＭＭＡ共混体系的相容机理。通过Ｄｏｃｋｉｎｇ Ｍｅｔｈｏｄｓ,计算出共混物中各对重复单元间的相互作用能。为真实反映马严酷以酐单元在ＳＭＡ中的电荷分布,建立了一个特殊的马来酸酐单元模型,它被用来模拟ＳＭＡ中的ＭＡ单元无间的相互作用模拟结果表明,ＳＭＡ中的ＭＡ单元无间存在较强的相互吸引作用。而不是ＳＭＡ中Ｓｔ单元与ＭＡ单元 相互排     

仿生鱼鳍中形状记忆合金驱动器的水下变形精度分析

简要介绍了仿生鱼鳍的基本机构和工作原理．为了提高形状记忆合金仿生鱼鳍的变形精度,理论计算了作为鱼鳍驱动器的形状记忆合金薄板对端部的水下变形误差．给出了形状记忆合金薄板表面的流体无量纲阻力系数随时间的变化关系,同时给出了某一时刻薄板表面及其周边的压力分布和薄板尾迹中的卡门涡街形态．最后,通过实验验证了理论推导的正确性．     

A hysteresis functional link artificial neural network for identification and model predictive control of SMA actuator

In this paper, a modified Hysteresis Functional Link Artificial Neural Network (HFLANN) is proposed to identify and control a Shape Memory Alloy (SMA) actuator, which has an inherent hysteresis phenomenon. In this structure, a hysteresis operator combined with the Functional Link Artificial Neural Network (FLANN) to employ the hysteresis phenomenon and the dynamic of the SMA actuator. The hysteresis operator is introduced to capture the SMA hysteresis. And the FLANN is employed to approximate the dynamic of the system. In identification problem, the FLANN parameters are trained by Particle Swarm Optimization technique. For control problem, a Model Predictive Controller based HFLANN is derived to control the system. The identification results show that the HFLANN can employ for the SMA dynamic. The simulation and experimental results demonstrated the effectiveness of the proposed algorithm. The SMA hysteresis phenomenon is compensated completely by proposed controller.     

An Operator-based Nonlinear Vibration Control System Using a Flexible Arm with Shape Memory Alloy

In the past, arms used in the fields of industry and robotics have been designed not to vibrate by increasing their mass and stiffness. The weight of arms has tended to be reduced to improve speed of operation, and decrease the cost of their production. Since the weight saving makes the arms lose their stiffness and therefore vibrate more easily, the vibration suppression control is needed for realizing the above purpose. Incidentally, the use of various smart materials in actuators has grown. In particular, a shape memory alloy (SMA) is applied widely and has several advantages: light weight, large displacement by temperature change, and large force to mass ratio. However, the SMA actuators possess hysteresis nonlinearity between their own temperature and displacement obtained by the temperature. The hysteretic behavior of the SMA actuators affects their control performance. In previous research, an operator-based control system including a hysteresis compensator has been proposed. The vibration of a flexible arm is dealt with as the controlled object; one end of the arm is clamped and the other end is free. The effectiveness of the hysteresis compensator has been confirmed by simulations and experiments. Nevertheless, the feedback signal of the previous designed system has increased exponentially. It is difficult to use the system in the long-term because of the phenomenon. Additionally, the SMA actuator generates and radiates heat because electric current passing through the SMA actuator provides heat, and strain on the SMA actuator is generated. With long-time use of the SMA actuator, the environmental temperature around the SMA actuator varies through radiation of the heat. There exists a risk that the ambient temperature change dealt with as disturbance affects the temperature and strain of the SMA actuator. In this research, a design method of the operator-based control system is proposed considering the long-term use of the system. In the method, the hysteresis characteristics of the SMA actuator and the temperature change around the actuator are considered. The effectiveness of the proposed method is verified by simulations and experiments.

     

Control of Shape Memory Alloy Actuators with a Neuro-fuzzy Feedforward Model Element

This paper describes development of a motion controller for Shape Memory Alloy (SMA) actuators using a dynamic model generated by a neuro-fuzzy inference system. Using SMA actuators, it would be possible to design miniature mechanisms for a variety of applications including miniature robots for micro manufacturing. Today SMA is used for valves, latches, and locks, which are automatically activated by heat. However it has not been used as a motion control device due to difficulty in the treatment of its highly nonlinear strain-stress hysteresis characteristic. In this paper, a dynamic model of a SMA actuator is developed using ANFIS, a neuro-fuzzy inference system provided in MATLAB environment. Using neuro-fuzzy logic, the system identification of the dynamic system is performed by observing the change of state variables (displacement and velocity) responding to a known input (input voltage to the current amplifier for the SMA actuator). Then, using the dynamic model, the estimated input voltage required to follow a desired trajectory is calculated in an open-loop manner. The actual input voltage supplied to the current amplifier is the sum of this open-loop input voltage and an input voltage calculated from an ordinary PD control scheme. This neuro-fuzzy logic-based control scheme is a very generalized scheme that can be used for a variety of SMA actuators. Experimental results are provided to demonstrate the potential for this type of controller to control the motion of the SMA actuator.     

Development of a shape memory alloy actuator. Improvement of output performance by the introduction of a σ-mechanism

The driving-force-generating principle of an actuator made of shape memory alloy (SMA) is based on the thermal elastic martensitic transformation, a kind of elastic phenomenon. As a result, conventional SMA actuators which use a circular pulley have tended to exhibit undesirable characteristics such as the maximum generable torque being changed depending on the rotating angle when the robot joint was driven by rotating motion transformed from expansion/contraction of the SMA, so that the servo system to support the torque under a certain load could not have an operable range wide enough for practical application. This paper intends to clarify these problems of SMA actuators and proposes a new joint mechanism using a σ-shaped non-circular pulley, called the σ-mechanism, for joint linkage to overcome the problems. This design enables the maximum generated torque to be kept uniform at all times by reducing the torque-arm-length in inverse proportion when the SMA tension increases corresponding to the rotating angle of the joint. Subsequently, a specifically designing algorithm for the proposed σ-mechanism is discussed. The validity of the new mechanism is demonstrated by an experimental model using an SMA actuator with a σpulley.     

Social Media Analytics

In this contribution, we introduce “social media analytics” (SMA) as an emerging interdisciplinary research field that, in our view, will have a significant impact on social media-related future research from across different academic disciplines. Despite a number of challenges, we argue that SMA can provide other disciplines – including IS – with methodological foundations for research that focuses on social media. Furthermore, we believe that SMA can help IS research to develop decision-making or decision-aiding frameworks by tackling the issue of social media-related performance measurement, which has been challenging until now. Moreover, SMA can provide architectural designs and solution frameworks for new social media-based applications and information systems. Finally, we call for an interdisciplinary SMA research agenda as well as a significantly increased level of interdisciplinary research co-operation, which must aim to generate significant advancements in scientific methods for analyzing social media, as well as to answer research questions from across different disciplines.     

SMA:前瞻性多线程体系结构

提出了一种新的ＩＬＰ处理器体系结构－前瞻性多线程体系的结构,简称ＳＭＡ．它结合了前瞻性执行机制和多线程执行机制,以整个线程为长步进行前瞻性执行,多个线程并行执行并且共享处理器硬件资源,这样,处理器既通过组合每个线程的指令窗口形成一个大的动态指令窗口,开发出程序中更大的ＩＬＰ,又利用多线程执行机制屏蔽各种长延迟操作,达到较高的资源利用率;介绍了ＳＭＡ执行模型,并讨论了ＳＭＡ处理器的实现和其中的关键技     

A three-dimensional shape memory alloy microelectrode with clippingstructure for insect neural recording

A microelectrode, with clipping structure for neural recording from a free-moving insect, was designed and fabricated using a shape memory alloy (SMA) thin film. The SMA thin films (titanium nickel; Ti-48 at.%Ni) are deposited by RF magnetron sputtering and patterned by HF-HNO ₃ wet etching. The transformation temperatures of the SMA thin films were measured at 54°C (A*) and 50°C (M*). The SMA microelectrode consists of a “hook” structure (720 μm×480 μm) and two “C”-shape probes (600 μm×70 μm). The electrode impedance is about 5 kΩ at 1 kHz. The desired three-dimensional (3D) shape is given to the electrode by a bonded wire. The clinging force of the electrode to the nerve is enhanced by the 3-D structures. The SMA microelectrode can clip a nerve cord tightly. The damages of the nerve by thermal actuation of the clip are not observed by physiological analysis. The neural activity from a living insect was successfully recorded with this SMA microelectrode     

基于稀疏矩阵的Arnold数字图像加密算法

针对原有Arnold数字图像加密算法中常见的密钥空间不足的问题,提出了一种基于稀疏矩阵的Arnold数字图像加密算法--SMA;同时为了进一步提高该基于稀疏矩阵的Arnold数字图像加密算法的安全性,利用图像分层及三层加密结构的思想来加以改进,提出了安全性提升算法--3SMA(3 round SMA)。SMA算法的加密流程首先利用Arnold变换将明文图片扩散到一个较大的稀疏矩阵中,再去除稀疏矩阵中的无效元素得到密文;解密时输入密文图片,依照预先计算好的对换表将密文中的像素调整回原来的位置得到明文。3SMA算法使用三个不同的轮密钥,每一轮都处理明文图像中的两个颜色分量以达到加密的目的。实验表明,与已有的Arnold数字图像加密算法进行对比时,SMA与3SMA算法具有更高的安全性。     

Improving urban classification through fuzzy supervised classification and spectral mixture analysis

In this study, a fuzzy‐spectral mixture analysis (fuzzy‐SMA) model was developed to achieve land use/land cover fractions in urban areas with a moderate resolution remote sensing image. Differed from traditional fuzzy classification methods, in our fuzzy‐SMA model, two compulsory statistical measurements (i.e. fuzzy mean and fuzzy covariance) were derived from training samples through spectral mixture analysis (SMA), and then subsequently applied in the fuzzy supervised classification. Classification performances were evaluated between the ‘estimated’ landscape class fractions from our method and the ‘actual’ fractions generated from IKONOS data through manual interpretation with heads‐up digitizing option. Among all the sub‐pixel classification methods, fuzzy‐SMA performed the best with the smallest total_MAE (MAE, mean absolute error) (0.18) and the largest Kappa (77.33%). The classification results indicate that a combination of SMA and fuzzy logic theory is capable of identifying urban landscapes at sub‐pixel level.