Design of an Active Cooling System for Thermally Activated Soft Actuators

Brandon P. R. Edmonds, A. L. Trejos
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引用次数: 6

Abstract

A new type of actuator made from twisting a silver-plated nylon thread presents new possibilities for the way wearable mechatronic rehabilitation devices are designed. The twisted coiled actuator (TCA) has been previously shown to provide a power density up to 100 times that of biological muscles, while also encompassing biomimetic characteristics. However, since TCAs require heat to contract, the main drawbacks preventing this type of actuator are its inherent low efficiency and slow reaction times. To combat both of these issues, a simple tube enclosure was designed to provide active cooling using forced air. The two main parameters affecting the efficiency and bandwidth are the cooling air pressure and tube diameter. This study presents a two-way repeated measures test to compare these parameters on the cooling and heating rates of the TCA system, as well as the thermal capacitance with three pressure levels (10, 15, and 20 psi) and three tube diameters (4, 4.5, and 5 mm). The results show that an increase in pressure significantly improves the rate of cooling, while a decrease in tube diameter has negative effects on the efficiency and cooling rate of the system. The mean values of the cooling time $(\tau_{\text {cool}})$ were 2.972, 2.210, and 2.682 seconds for 4, 4.5, and 5 mm diameters, respectively. These results indicate that a decrease in diameter improves the cooling rate up to the point at which the walls of the tube become so close to the TCA strand, that they prevent rapid heat transfer while cooling.
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热激活软执行器的主动冷却系统设计
一种由镀银尼龙线制成的新型致动器为可穿戴机电康复设备的设计提供了新的可能性。扭曲线圈驱动器(TCA)先前已被证明可以提供高达生物肌肉100倍的功率密度,同时还具有仿生特性。然而,由于tca需要热量来收缩,阻碍这种类型的执行器的主要缺点是其固有的低效率和缓慢的反应时间。为了解决这两个问题,设计了一个简单的管壳,使用强制空气提供主动冷却。影响效率和带宽的两个主要参数是冷却空气压力和管径。本研究提出了一种双向重复测量测试,以比较TCA系统的冷却和加热速率,以及三种压力水平(10、15和20 psi)和三种管径(4、4.5和5 mm)下的热电容参数。结果表明,压力的增加显著提高了冷却速率,而管径的减小对系统的效率和冷却速率有负面影响。4、4.5和5 mm直径的冷却时间$(\tau_{\text {cool}})$的平均值分别为2.972、2.210和2.682秒。这些结果表明,直径的减小提高了冷却速度,直到管壁变得如此接近TCA链,从而防止了冷却时的快速传热。
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