形状记忆合金驱动的人工逼尿肌系统

Artificial Bladder Detrusor System Driven by Shape Memory Alloy

针对神经源性、肌源性膀胱缺乏有效治疗手段的现状,从工程学角度提出了一种新的解决方案——人工逼尿肌系统。基于形状记忆合金(SMA)弹簧的形状记忆效应,设计了由无线能量传输模块、控制模块、反馈模块和执行模块组成的系统结构,旨在实现符合人体尿动力学规律的辅助排尿。文中首先建立了人体膀胱的有限元模型,仿真分析了人体膀胱的储尿和辅助排尿过程,在仿真结果的基础上结合SMA弹簧的数学模型,对SMA弹簧致动器的结构参数进行了优化设计;其次,结合实验数据推导了SMA弹簧温度-自由高度方程;然后,结合热力学公式和弹簧数学模型推导了系统控制方程,并在此基础上提出了系统开环控制策略;最后,基于系统的反馈模块,设计了比例积分微分(PID)闭环控制策略,并搭建模拟实验平台研究了系统的尿流率特性。结果表明:系统原理可行,辅助排尿过程连续可控,在应对不同尿液容量时两种控制策略均能实现符合人体尿动力学规律的辅助排尿。文中结果可为设计适用于临床的人工逼尿肌系统提供指导,也可为其他以SMA弹簧作为致动器的植入装置的设计提供借鉴和参考。

In view of the lack of effective treatment for neurogenic and myogenic bladder,a new solution,namely an artificial bladder detrusor system,was proposed from an engineering perspective.Based on the shape memory effect of shape memory alloy(SMA)springs,a system structure consisting of a wireless power transfer module,a control module,a feedback module and an executive module was designed to realize the assisted urination in accordance with human urodynamics.A finite element model of human bladder was established,and the storage process as well as the assisted urination process of the human bladder was simulated and analyzed.Based on the simulation results and the mathematical model of SMA springs,the structural parameters of SMA spring actuator were optimized.Then,the temperature-free height equation of SMA springs was derived according to experimental data.Furthermore,by combining with the thermodynamic formula and the spring mathematical model,the system control equation was derived,and an open-loop control strategy of the system was proposed on this basis.Finally,based on the feedback module of the system,a proportional integral differential(PID)closed-loop control strategy was designed,and a simulation experiment platform was constructed to study the urine flow rate characteristics of the system.The results indicate that the principle of the system is feasible,and that the assisted urination process is continuously controllable.Under different urine volumes,the two control strategies can both achieve assisted urination in accordance with human urodynamic principles.This research can provide guidance for the design of clinically applicable artificial bladder detrusor system and also offer a reference for the design of other implantable devices using SMA springs as actuators.