Since shape memory alloy has a high power density and is magnetic resonance imaging compatible, it has been chosen as the actuator for the meso-scale minimally invasive neurosurgical intracranial robot (MINIR-II) that is envisioned to be operated under continuous magnetic resonance imaging guidance. We have devised a water cooling strategy to improve its actuation frequency by threading a silicone tube through the spring coils to form a compact cooling module-integrated actuator. To create active bi-directional motion in each robot joint, we configured the shape memory alloy springs in an antagonistic way. We modeled the antagonistic shape memory alloy spring behavior and provided the detailed steps to simulate its motion for a complete cycle. We investigated the heat transfer during the resistive heating and water cooling processes. Characterization experiments were performed to determine the parameters used in both models, which were then verified by comparing the experimental and simulated data. The actuation frequency of the antagonistic shape memory alloys was evaluated for several motion amplitudes and we could achieve a maximum actuation frequency of 0.143 Hz for a sinusoidal trajectory with 2 mm amplitude. Lastly, we developed a robotic system to implement the actuators on the MINIR-II to move its end segment back and forth for approximately ±25°.

中文翻译：

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具有水冷策略的神经外科机器人形状记忆合金弹簧的建模与表征

由于形状记忆合金具有高功率密度和磁共振成像兼容，它已被选为中尺度微创神经外科颅内机器人 (MINIR-II) 的执行器，该机器人设想在连续磁共振成像引导下进行操作. 我们设计了一种水冷策略，通过将硅胶管穿过弹簧线圈形成一个紧凑的冷却模块集成致动器来提高其致动频率。为了在每个机器人关节中创建主动双向运动，我们以对抗方式配置了形状记忆合金弹簧。我们模拟了对抗形状记忆合金弹簧的行为，并提供了详细步骤来模拟其完整循环的运动。我们研究了电阻加热和水冷过程中的热传递。进行表征实验以确定两个模型中使用的参数，然后通过比较实验和模拟数据来验证这些参数。对抗性形状记忆合金的致动频率在几个运动幅度下进行了评估，对于 2 mm 幅度的正弦轨迹，我们可以获得 0.143 Hz 的最大致动频率。最后，我们开发了一个机器人系统来实现 MINIR-II 上的执行器，以使其端部前后移动约 ±25°。143 Hz 用于振幅为 2 mm 的正弦轨迹。最后，我们开发了一个机器人系统来实现 MINIR-II 上的执行器，以使其端部前后移动约 ±25°。143 Hz 用于振幅为 2 mm 的正弦轨迹。最后，我们开发了一个机器人系统来实现 MINIR-II 上的执行器，以使其端部前后移动约 ±25°。