Soft continuum manipulators integrating a shape sensing modality using optoelectronic sensors

在过去的几年里，许多软连续体操纵器已经开发出来并适应了医疗用途，包括微创手术（MIS）、内窥镜检查和结肠镜检查等程序。这些软连续操作器通常小巧灵活，具有较大的工作空间，可以通过小通道和切口进入，并可以安全地通过身体进行操作，最大限度地减少手术中对软组织和器官的过度压力。在医疗程序中使用这些机械手所面临的主要挑战之一是位置控制。对机械手在机体内部的位置和形状有一个感觉是很重要的，这样才能保证使用的准确性和安全性。这是通过闭环位置反馈控制，使用不同的形状感应技术。视觉方法（摄像机/视频）非常简单，然而，在外科手术过程中，器官或物体可能会阻挡机械手，导致摄像机无法确定位置。存在一种成功集成基于光纤光栅（FBG）的形状传感模态的软连续体机械臂；它们的传感性能准确。尽管如此，它的校准方法非常复杂。这种被称为“询问器”的设备可以检测附着在柔软材料上的fbg的应变值，成本约为2万英镑，而且制造形状传感器很复杂。文献中的其他方法包括小型化、漂移误差、更新速度慢以及无法在更大的曲率范围内精确测量等问题。为此，本项目提出如下解决方案。这是一种基于光电传感器的柔性连续体机械臂形状传感新方法。该解决方案解决了前面概述的问题，并且具有潜在的小型化、精确、计算成本低、易于集成以及成本低的优势，使此类设备易于在医疗保健行业中采用。这些传感器将被集成到一系列圆盘中，这些圆盘是刚性连接的，形成柔性机械手的主体。他们根据连续表面上的反射量来测量每个柔性机械结构的距离（或变形）。根据测量的变形值，可以估计出两到三个方向（横摇、俯仰和偏航）。因此，每个连续连接的机械弯曲的所有估计方向都可以通过刚性连杆模型进行简化，并且可以可视化整个机械手的形状。构成本项目一部分的方法首先包括能够容纳多个这些传感器的机械手的结构设计。接下来将涉及开发软件，该软件可以测量传感器的数据，并使用各种建模和计算技术进行一组校准实验，以获得光电传感器的物理方向值数据。下一步将是测试应用，通过将这种形状传感方法集成到具有选定驱动机构（肌腱，液压或气动）的电动执行器的柔性机械手中。这可以在模型上进行测试，并且可以建立一个仿真来可视化机械臂的三维形状。最终的目标是小型化和设计一个如何将串联的内部刚性结构与由软材料组成的外部覆盖相结合的设计。

Over previous years, many soft continuum manipulators have been developed and adapted for medical use, including procedures such as minimally invasive surgery (MIS), endoscopy and colonoscopy. These soft continuum manipulators are often small and flexible, with a large workspace, allowing access through small passages and incisions, as well as to safely manoeuvre through the body, minimising excessive force on soft tissue and organs in surgery. One of the main challenges that face the use of these manipulators for medical procedures is that of position control. It is important to have a sense of the position and shape of the manipulator inside the body, to ensure accuracy and safety in use. This is done through closed loop position feedback control, using different shape sensing techniques.A vision approach (camera/video) is very simple, however, during surgical procedures, organs or objects might block the manipulator, resulting the camera being unable to determine position. There exists a soft continuum manipulator successfully integrating a shape sensing modality based on Fibre Bragg gratings (FBG); their sensing performances are accurate. Despite this, its calibration method is very complicated. The device called "interrogator" which can detect strain values from the FBGs attached on the soft material body costs around £20,000 and manufacturing the shape sensor is complex. Other methods in the literature included issues with miniaturisation, errors due to drift, slow update rate, and inability to accurately measure over a larger range of curvatures.For this reason, the following solution is proposed for this project. This is a novel shape sensing method for soft continuum manipulators, that utilises optoelectronic sensors. This solution addresses the issues outlined previously, and it has the advantage of being potentially miniaturised, accurate, computationally inexpensive, easily integrated, as well as having a low cost, allowing such a device to be easily adopted within the healthcare industry. These sensors are to be integrated into a series of circular disks that are rigidly linked to form the body of the flexible manipulator. They measure the distances (or deformations) in each of the flexible mechanical structures, based in the amount of reflection on consecutive surfaces. From the measured deformation values, two to three orientations can be estimated (roll, pitch and yaw). Therefore, all of the estimated orientations in each of the serially connected mechanical flexures can be simplified by the rigid-link model, and the overall manipulator's shape can be visualised.The methods that form part of this project firstly include the structural design of the manipulator that is able to house a number of these sensors. Next will involve developing software that enables the measuring of data from the sensors and carrying out a set of calibration experiments to obtain the optoelectronic sensor's data to physical orientation values, using a various modelling and computational techniques. The next step will be testing the application, by integrating this shape sensing method in to a flexible manipulator with motorised actuators with a chosen driving mechanism (tendon, hydraulic, or pneumatic). This can be tested on phantoms and a simulation can be built to visualise the manipulator shape in three dimensions. The final aim is to miniaturise and devise a design on how to combine the serially connected internal rigid structure with with an outer cover consisting of soft material.