用于微创外科手术机器人的多维力传感器解耦方法研究

Research on decoupling method of multi-dimensional force sensor used in minimally invasive surgical robot

在微创外科手术机器人系统中,力反馈功能的实现可以提高外科医生在手术中的灵活性,降低患者组织和器官损伤的风险。为实现手术过程中力的检测,设计了一种基于光纤布拉格光栅(FBG)的微创外科手术机器人多维力传感器并研究其解耦方法。该多维力传感器由3条间隔120°的光纤布拉格光栅沿轴向粘贴于手术工具杆末端构成。首先在对传感器应力分析的基础上使用最小二乘法解耦,但由于装配等因素使传感器输入输出之间增加了非线性成分,因此使用前馈神经网络对多维力传感器进行非线性解耦。其次从理论和实验两方面分析了穿刺器的平移对解耦之后的力的影响。实验结果表明,前馈神经网络解耦多维力传感器的效果较好,3个相互垂直方向上的平均误差分别为0.05, 0.07和0.18 N;穿刺器平移后力检测的最大平均误差为0.036 N,可以忽略不计。设计的传感器、解耦方法以及对穿刺器平移影响的分析均具有很强的实用性。

In minimally invasive surgical robot system, the implementation of the force feedback function can increase the flexibility of the surgeon during surgery and reduce the risk of damage to the tissues and organs of the patient. In order to achieve the force detection during surgical process, a multi-dimensional force sensor based on fiber Bragg grating(FBG) is designed for minimally invasive surgical robot and its decoupling methods are studied. The multi-dimensional force sensor is composed of three fiber gratings spaced 120° apart that are attached to the end of the surgical tool rod along the axial direction. Firstly, based on the stress analysis of the sensor, the least squares method is used for decoupling. However, the sensor has a nonlinear relationship between inputs and outputs due to the factors such as assembly and etc., so the feedforward neural network is used to carry out the nonlinear decoupling of the multi-dimensional force sensor. Then, the effects of the trocar translation on the decoupled force are analyzed theoretically and experimentally. The experiment results show that the feedforward neural network has good decoupling effects for the multi-dimensional force sensor, and the average errors in three mutually perpendicular directions are 0.05, 0.07 and 0.18 N, respectively. The maximum average error of the force detection after the trocar translation is 0.036 N, which is negligible. The designed sensor, the decoupling method and the analysis of trocar translation effects are proved to have strong practicality.