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Shape memory alloys are a category of smart materials which exhibit large deformations under temperature or magnetic stimuli due to micromechanical changes. These alloys offer a good potential in design of control systems, sensors and actuators due to two main effects called shape memory effect and superelastic effect. Main advantages of these systems are their small scale, low weight, low activation power, long life and high power to weight ratio. On the other hand, the main disadvantage of thermal ones is their low actuation frequency. In this work, inspired by human arm muscles, a new actuator is designed and its actuation time is minimized utilizing the thermoelectric effect. The process requires simultaneous analysis of heat transfer, constitutive equations, phase transformation and also the dynamic equations of the actuator. The dynamic response of the designed actuator is compared with the similar experimental data available in the literature and finally it is shown that, the actuation time of the proposed actuator can be reduced at least 50% thanks to the Peltier effect.

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In order to use and control Shape Memory Alloy (SMA) actuators, it is essential to measure its state variables to be used as the feedback in the control loop. The wire temperature is one of critical state variables need to be fed back. However, measuring this variable is difficult and usually contains some noises and delay. Therefore, it is desirable to estimate this variable instead of measuring it. Thermoelectric model is one of the most common models used to estimate the SMA wire temperature. This model calculates the SMA wire temperature based on its input electric current. In this paper, first three unknown parameters of thermoelectric model are estimated using Extended Kalman filter (EKF) and the wire temperature is calculated based on the identified model. The parameter estimation and temperature calculation are performed on a practical SMA actuator. Then, in order to eliminate the effects of environmental disturbances and the thermoelectric model inaccuracies, the temperature is estimated using EKF. In this method, all measurable data such as the input current, the strain and stress of the SMA wire are used in the temperature estimation. The estimator combines the information obtained from both thermoelectric and Brinson models and the measurement data. This method is used for online temperature estimation of the SMA wire on a practical SMA actuator. The results show that the estimated temperature matches the actual wire temperature with high precision. Furthermore, the temperature estimation using EKF is more accurate than the estimates of the thermoelectric model.

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In a thermoelectric air-handling unit, a number of thermoelectric modules with forced convection heat sinks are used. In this research, it is tried to investigate the effect of module arrangement and air flow pattern on thermal performance of the system. For this purpose, the thermal performance of an air-handling unit including four thermoelectric modules with three different heat sinks layouts; parallel, series with unidirectional flow and series with counter flow were compared. The entropy analysis has been used to study the thermal performance and pressure drop imposed on the system. In addition, the effect of the electric current applied to the modules and the hot and cold air flows on the coefficient of performance of the system has been studied for three different layouts. Results indicated that, heat sinks layout and air flow pattern through the fins have significant effects on the thermal performance of a thermoelectric air-handling unit. The coefficient of performance for cooling and heating in the series arrangement are 1.4 and 1.1 times of those in parallel arrangement, respectively. The results of the entropy analysis showed that although the pressure drop imposed on the system in the layout of the series is greater than the parallel arrangement, this cannot reduce the advantage of using the series layout.

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