Toward Extending Concentric Tube Robot Kinematics for Large Clearance and Impulse Curvature

Concentric Tube Robots (CTRs) have been proposed to operate within the unstructured environment for minimally invasive surgeries. In this letter, we consider the operation scenario where the tubes travel inside the channels with a large clearance or large curvature, such as aortas or industrial pipes. Accurate kinematic modeling of CTRs is required for the development of advanced control and sensing algorithms. To this end, we extended the conventional CTR kinematics model to a more general case with large tube-to-tube clearance and large centerline curvature. Numerical simulations and experimental validations are conducted to compare our model with respect to the conventional CTR kinematic model. In the physical experiments, our proposed model achieved a tip position error of 1.53 mm in the 2D planer case and 4.36 mm in 3D case, outperforming the state-of-the-art model by 71% and 66%, respectively.Comment: 8 pages, 6 figure

Modeling, Analysis, Force Sensing and Control of Continuum Robots for Minimally Invasive Surgery

This dissertation describes design, modeling and application of continuum robotics for surgical applications, specifically parallel continuum robots (PCRs) and concentric tube manipulators (CTMs). The introduction of robotics into surgical applications has allowed for a greater degree of precision, less invasive access to more remote surgical sites, and user-intuitive interfaces with enhanced vision systems. The most recent developments have been in the space of continuum robots, whose exible structure create an inherent safety factor when in contact with fragile tissues. The design challenges that exist involve balancing size and strength of the manipulators, controlling the manipulators over long transmission pathways, and incorporating force sensing and feedback from the manipulators to the user. Contributions presented in this work include: (1) prototyping, design, force sensing, and force control investigations of PCRs, and (2) prototyping of a concentric tube manipulator for use in a standard colonoscope. A general kinetostatic model is presented for PCRs along with identification of multiple physical constraints encountered in design and construction. Design considerations and manipulator capabilities are examined in the form of matrix metrics and ellipsoid representations. Finally, force sensing and control are explored and experimental results are provided showing the accuracy of force estimates based on actuation force measurements and control capabilities. An overview of the design requirements, manipulator construction, analysis and experimental results are provided for a CTM used as a tool manipulator in a traditional colonoscope. Currently, tools used in colonoscopic procedures are straight and exit the front of the scope with 1 DOF of operation (jaws of a grasper, tightening of a loop, etc.). This research shows that with a CTM deployed, the dexterity of these tools can be increased dramatically, increasing accuracy of tool operation, ease of use and safety of the overall procedure. The prototype investigated in this work allows for multiple tools to be used during a single procedure. Experimental results show the feasibility and advantages of the newly-designed manipulators

DEVELOPMENT OF A KINETIC MODEL FOR STEERABLE CATHETERS FOR MINIMALLY INVASIVE SURGERY

The steerable catheters have demonstrated many advantages to overcome the limitations of the conventional catheters in the minimally invasive surgery. The motion and force transmission from the proximal end to distal tip of the catheter have significant effects to the efficiency and safety of surgery. While the force information between the catheter and the body (e.g., vessel) can be obtained by mounting sensors on the distal tip of the catheter, this would be more intrusive and less reliable than the one without the sensors, which is described in this disseration. In addition, the small diameters of the catheters may also restrict the idea of mounting sensors on the distal tip. The other approach to obtain the force information is to infer it from the information outside the body. This will demand an accurate mathematical model that describes the force and motion relation called kinetic model, and unfortunately, such a kinetic model is not available in the literature. In this dissertation, a kinetic model for steerable catheters is presented wich captures the following characteristics of the steerable catheter, namely (1) the geometrical non-linear behavior of the catheter in motion, (2) the deformable pathway, (3) the friction between the catheter and the pathyway, and (4) the contact between the catheter and pathway. A non-linear finite element system (SPACAR) was employed to capture these characteristics. A test-bed was built and an experiment was carried out to verify the developed kinetic model. The following conclusions can be drawn from this dissertation: (1) the developed kinetic model is accurte in comparison with those in literature; (2) the Dahl friction model, the LuGre friction model and the simplified LuGre friction model are able to capture the friction behavior between the catheter and the pathway but the Coulomb friction model fails (as it cannot capture the hysteresis property which has a significant influence on the behavior of the catheter); (3) the developed kinetic model has the potential of being used to optimize the design and operation of steerable catheters with several salient findings that (3a) the maximal contact force between the catheter and the pathway occurs on the tip of the distal part or the connecting part between the distal part and catheter body of the catheter and (3b) the rigidity and length of the distal part are crucial structural parameters that affect the motion and force transmission significantly. There are several contributions made by this dissertation. In the field of the steerable catheter, biomechanics and bio-instrumentation, the contributions are summarized in the following: (1) the approach to develop the kinetic model of the steerable catheter in a complex work environment is useful to model other similar compliant medical devices, such as endoscope; (2) the kinetic model of the steerable catheter can provide the force information to improve the efficiency and safety of MIS (minimally invastive surgery) and to realize the “doctor-assisted” catheter-based MIS procedure; (3) the kinetic model can provide accurate data for developing other simplified models for the steerable catheters in their corresponding work environments for realizing the robotic-based fully automated MIS procedure. (4) The kinetic model of the steerable catheter and the test-bed with the corresponding instruments and methods for the kinetic and kinematic measurements are a useful design validation in the steerable catheter technology as well as for the training of physicians to perform the catheter-based interventional procedure by adding more complex anatomic phantoms. In the field of continuum manipulator and continuum robots, the approach to develop the kinetic model is useful to model other manipulators and robots, such as snake-like robots

Design, Modeling and Control of Micro-scale and Meso-scale Tendon-Driven Surgical Robots

Manual manipulation of passive surgical tools is time consuming with uncertain results in cases of navigating tortuous anatomy, avoiding critical anatomical landmarks, and reaching targets not located in the linear range of these tools. For example, in many cardiovascular procedures, manual navigation of a micro-scale passive guidewire results in increased procedure times and radiation exposure. This thesis introduces the design of two steerable guidewires: 1) A two degree-of-freedom (2-DoF) robotic guidewire with orthogonally oriented joints to access points in a three dimensional workspace, and 2) a micro-scale coaxially aligned steerable (COAST) guidewire robot that demonstrates variable and independently controlled bending length and curvature of the distal end. The 2-DoF guidewire features two micromachined joints from a tube of superelastic nitinol of outer diameter 0.78 mm. Each joint is actuated with two nitinol tendons. The joints that are used in this robot are called bidirectional asymmetric notch (BAN) joints, and the advantages of these joints are explored and analyzed. The design of the COAST robotic guidewire involves three coaxially aligned tubes with a single tendon running centrally through the length of the robot. The outer tubes are made from micromachined nitinol allowing for tendon-driven bending of the robot at variable bending curvatures, while an inner stainless steel tube controls the bending length of the robot. By varying the lengths of the tubes as well as the tendon, and by insertion and retraction of the entire assembly, various joint lengths and curvatures may be achieved. Kinematic and static models, a compact actuation system, and a controller for this robot are presented. The capability of the robot to accurately navigate through phantom anatomical bifurcations and tortuous angles is also demonstrated in three dimensional phantom vasculature. At the meso-scale, manual navigation of passive pediatric neuroendoscopes for endoscopic third ventriculostomy may not reach target locations in the patient's ventricle. This work introduces the design, analysis and control of a meso-scale two degree-of-freedom robotic bipolar electrocautery tool that increases the workspace of the neurosurgeon. A static model is proposed for the robot joints that avoids problems arising from pure kinematic control. Using this model, a control system is developed that comprises of a disturbance observer to provide precise force control and compensate for joint hysteresis. A handheld controller is developed and demonstrated in this thesis. To allow the clinician to estimate the shape of the steerable tools within the anatomy for both micro-scale and meso-scale tools, a miniature tendon force sensor and a high deflection shape sensor are proposed and demonstrated. The force sensor features a compact design consisting of a single LED, dual-phototransistor, and a dual-screen arrangement to increase the linear range of sensor output and compensate for external disturbances, thereby allowing force measurement of up to 21 N with 99.58 % accuracy. The shape sensor uses fiber Bragg grating based optical cable mounted on a micromachined tube and is capable of measuring curvatures as high as 145 /m. These sensors were incorporated and tested in the guidewire and the neuroendoscope tool robots and can provide robust feedback for closed-loop control of these devices in the future.Ph.D

Wire-driven mechanism and highly efficient propulsion in water.

自然生物的杰出表现往往令人们叹为观止。正因为如此，在机器人研究中对自然界动植物的模仿从未间断。本文受动物肌肉骨骼系统（尤其是蛇的脊柱以及章鱼手臂的肌肉分布）的启发，设计了一种新型的仿生拉线机构。该机构由柔性骨架以及成对拉线组成。柔性骨架提供支撑，拉线模拟肌肉将驱动器的运动和力传递给骨架，并控制骨架运动。从骨架结构分，拉线机构可分为蛇形拉线机构以及连续型拉线机构；从骨架分段来看，拉线机构可分为单段式拉线机构以及多段式拉线机构，其中每段由一或两对拉线控制。拉线机构的主要性能特征包括：大柔性，高度欠驱动，杠杆效应，以及远程传力。机构的柔性使得它可以产生很大的弯曲变形；欠驱动设计极大地减少了驱动器的数目，简化了系统结构；在杠杆效应下，骨架末端速度、加速度与拉线的速度、加速度相比得到数十倍放大；通过拉线将驱动器的运动和力远程传递给执行机构，使得拉线机构结构简单紧凑。基于以上特征，拉线机构不仅适合工作于狭窄空间，同时也适合于摆动推进，尤其是水下推进。论文系统地介绍了拉线机构的设计，运动学，工作空间，静力学以及动力学模型。在常曲率假设下分别建立了蛇形拉线机构以及连续型拉线机构的运动学模型，在此基础上建立了一个通用运动学模型，以及工作空间模型。与传统避障相反，本文提出了一种利用现有障碍或主动布置约束来拓展工作空间的新方法。通过牛顿-欧拉法以及拉格朗日方程建立了蛇形拉线机构的静力学模型以及动力学模型。在非线性欧拉-伯努利梁理论下结合汉密尔顿原理建立了连续型拉线机构的静力学模型以及动力学模型。论文中利用拉线机构设计了一系列新型水下推进器。与传统机器鱼推进器设计方法（单关节，多关节以及基于智能材料的连续型设计）相比，基于拉线机构的水下推进器的优点在于：所需驱动器少，能更好地模拟鱼的游动，易于控制，推进效率高，以及容易衍生新型推进器。设计制作了四条拉线驱动机器鱼，以此为平台验证了拉线推进器的性能以及优点。实验结果表明，基于蛇形拉线机构的推进器可以提供较大推力；基于连续型拉线机构设计的推进器受摩擦影响较小；基于单段式拉线机构的推进器可以模仿鱼类摆动式推进，具有很好的转弯性能；基于多段式拉线机构的推进器可以同时模仿摆动式推进和波动式推进，具有更好的稳定性以及游速。此外，基于拉线机构制造了一种新型矢量推进器。该推进器可以提供任意方向的推力，从而提高机器鱼的机动性能。实验中，在两个额定功率为1瓦的电机驱动下，机器鱼的最大游速为0.67 体长/秒；最小转弯半径为0.24倍体长；转弯速度为51.4 度/秒；最高推进效率为92.85%。最后，采用拉线推进器制作了一个室内空中移动机器人，取名为Flying Octopus。它由一个氦气球提供浮力悬停在空中，通过四个独立控制的拉线扑翼驱动可在三维空间自由运动。Attracted by the outstanding performance of natural creatures, researchers have been mimicking animals and plants to develop their robots. Inspired by animals’ musculoskeletal system, especially the skeletal structure of snakes and octopus arm muscle arrangement, in this thesis, a novel wire-driven mechanism (WDM) is designed. It is composed of a flexible backbone and a number of controlling wire groups. The flexible backbone provides support, while the wire groups transmit motion and force from the actuators, mimicking the muscles. According to its backbone structure, the WDM is categorized as serpentine WDM and continuum WDM. Depending on the backbone segmentation, WDM is divided into single segment WDM and multi-segment WDM. Each segment is controlled by one or two wire groups. Features of WDM include: flexible, highly under-actuated, leverage effect, and long range force and motion transmission. The flexibility enables the WDM making large deformation, while the under-actuation greatly reduces th number of actuators, simplifying the system. With the leverage effect, WDM distal end velocity and acceleration is greatly amplified from that of wire. Also, in the WDM, the actuators and the backbone are serperated. Actuator’s motion is transmitted by the wires. This makes the WDM very compact. With these features, the WDM is not only well suited to confined space, but also flapping propulsion, especially in water.In the thesis, the design, kinematics, workspace, static and dynamic models of the WDM are explored systematically. Under the constant curvature assumption, the kinematic model of serpentine WDM and continuum WDM are established. A generalized model is also developed. Workspace model is built from the forward kinematic model. Rather than avoiding obstacles, a novel idea of employing obstacles or actively deploying constraints to expand workspace is also discussed for WDM-based flexible manipulators. The static model and dynamic model of serpentine WDM is developed using the Newton-Euler method and the Lagrange Equation, while that of continuum WDM is built under the non-linear Euler-Bernoulli Beam theory and the extended Hamilton’s principle.In the thesis, a number of novel WDM based underwater propulsors are developed. Compared with existing fish-like propulsor designs, including single joint design, multi-joint design, and smart material based continuum design, the proposed WDM-based propulsors have advantages in several aspects, such as employing less actuators, better resembling the fish swimming body curve, ease of control, and more importantly, being highly efficient. Also, brand new propulsors can be easily developed using the WDM. To demonstrate the features as well as the advantages of WDM propulsors, four robot fish prototypes are developed. Experiments show that the serpentine WDM-based propulsor could provide large flapping force while the continuum WDM-based propulsor is less affected by joint friction. On the other hand, single segment WDM propulsor can make oscillatory swim while multi- segment WDM propulsor can make both oscillatory and undulatory swims. The undulatory swimming outperforms the oscillatory swimming in stability and speed, but is inferior in turning around. In addition, a novel robot fish with vector propulsion capability is also developed. It can provide thrust in arbitrary directions, hence, improving the maneuverability of the robot fish. In the experiments, with the power limit of two watts, the maximum forward speed of the WDM robot fishes can reach 0.67 BL (Body Length)/s. The minimum turning radius is 0.24 BL, and the turning speed is 51.4°/s. The maximum Froude efficiency of the WDM robot fishes is 92.85%. Finally, the WDM-based propulsor is used to build an indoor Lighter-than-Air- Vehicle (LTAV), named Flying Octopus. It is suspended in the air by a helium balloon and actuated by four independently controlled wire-driven flapping wings. With the wing propulsion, it can move in 3D space effectively.Detailed summary in vernacular field only.Detailed summary in vernacular field only.Detailed summary in vernacular field only.Li, Zheng.Thesis (Ph.D.)--Chinese University of Hong Kong, 2013.Includes bibliographical references (leaves 205-214).Abstracts also in Chinese.Abstracth --- p.i摘要 --- p.iiiAcknowledgement --- p.vList of Figures --- p.xiList of Tables --- p.xviiChapter Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Background --- p.1Chapter 1.2 --- Related Research --- p.2Chapter 1.2.1 --- Flexible Manipulator --- p.2Chapter 1.2.2 --- Robot Fish --- p.10Chapter 1.3 --- Motivation of the Dissertation --- p.13Chapter 1.4 --- Organization of the Dissertation --- p.14Chapter Chapter 2 --- Biomimetic Wire-Driven Mechanism --- p.16Chapter 2.1 --- Inspiration from Nature --- p.16Chapter 2.1.1 --- Snake Skeleton --- p.18Chapter 2.1.2 --- Octopus Arm --- p.19Chapter 2.2 --- Wire-Driven Mechanism Design --- p.20Chapter 2.2.1 --- Flexible Backbone --- p.20Chapter 2.2.2 --- Backbone Segmentation --- p.26Chapter 2.2.3 --- Wire Configuration --- p.28Chapter 2.3 --- Wire-Driven Mechanism Categorization --- p.31Chapter 2.4 --- Summary --- p.32Chapter Chapter 3 --- Kinematics and Workspace of the Wire-Driven Mechanism --- p.33Chapter 3.1 --- Kinematic Model of Single Segment WDM --- p.33Chapter 3.1.1 --- Kinematic Model of the Serpentine WDM --- p.34Chapter 3.1.2 --- Kinematic Model of the Continuum WDM --- p.39Chapter 3.1.3 --- A Generalized Kinematic Model --- p.43Chapter 3.2 --- Kinematic Model of Multi-Segment WDM --- p.47Chapter 3.2.1 --- Forward Kinematics --- p.47Chapter 3.2.2 --- Inverse Kinematics --- p.51Chapter 3.3 --- Workspace --- p.52Chapter 3.3.1 --- Workspace of Single Segment WDM --- p.52Chapter 3.3.2 --- Workspace of Multi-Segment WDM --- p.53Chapter 3.4 --- Employing Obstacles to Expand WDM Workspace --- p.55Chapter 3.4.1 --- Constrained Kinematics Model of WDM --- p.55Chapter 3.4.2 --- WDM Workspace with Constraints --- p.61Chapter 3.5 --- Model Validation via Experiment --- p.64Chapter 3.5.1 --- Single Segment WDM Kinematic Model Validation --- p.64Chapter 3.5.2 --- Multi-Segment WDM Kinematic Model Validation --- p.66Chapter 3.5.3 --- Constrained Kinematic Model Validation --- p.70Chapter 3.6 --- Summary --- p.73Chapter Chapter 4 --- Statics and Dynamics of the Wire-Driven Mechanism --- p.75Chapter 4.1 --- Static Model of the Wire-Driven Mechanism --- p.75Chapter 4.1.1 --- Static Model of SPSP WDM --- p.75Chapter 4.1.2 --- Static Model of SPCP WDM --- p.81Chapter 4.2 --- Dynamic Model of the Wire-Driven Mechanism --- p.88Chapter 4.2.1 --- Dynamic Model of SPSP WDM --- p.88Chapter 4.2.2 --- Dynamic Model of SPCP WDM --- p.92Chapter 4.3 --- Summary --- p.94Chapter Chapter 5 --- Application I - Wire-Driven Robot Fish --- p.95Chapter 5.1 --- Fish Swimming Introduction --- p.95Chapter 5.1.1 --- Fish Swimming Categories --- p.95Chapter 5.1.2 --- Body Curve Function --- p.96Chapter 5.1.3 --- Fish Swimming Hydrodynamics --- p.101Chapter 5.1.4 --- Fish Swimming Data --- p.103Chapter 5.2 --- Oscillatory Wire-Driven Robot Fish --- p.104Chapter 5.2.1 --- Serpentine Oscillatory Wire-Driven Robot Fish Design --- p.105Chapter 5.2.2 --- Continuum Oscillatory Wire-Driven Robot Fish Design --- p.110Chapter 5.2.3 --- Oscillatory Robot Fish Propulsion Model --- p.114Chapter 5.2.4 --- Robot Fish Swimming Control --- p.116Chapter 5.2.5 --- Swimming Experiments --- p.118Chapter 5.3 --- Undulatory Wire-Driven Robot Fish --- p.125Chapter 5.3.1 --- Undulatory Wire-Driven Robot Fish Design --- p.125Chapter 5.3.2 --- Undulatory Wire-Driven Robot Fish Propulsion Model --- p.130Chapter 5.3.3 --- Swimming Experiments --- p.131Chapter 5.4 --- Vector Propelled Wire-Driven Robot Fish --- p.136Chapter 5.4.1 --- Vector Propelled Wire-Driven Robot Fish Design --- p.136Chapter 5.4.2 --- Tail Motion Analysis --- p.140Chapter 5.4.3 --- Swimming Experiments --- p.142Chapter 5.5 --- Wire-Driven Robot Fish Performance and Discussion --- p.144Chapter 5.5.1 --- Performance --- p.144Chapter 5.5.2 --- Discussion --- p.147Chapter 5.6 --- Summary --- p.149Chapter Chapter 6 --- Aplication II - Wire-Driven LTAV - Flying Octopus --- p.151Chapter 6.1 --- Introduction --- p.151Chapter 6.2 --- Flying Octopus Design --- p.152Chapter 6.2.1 --- Flying Octopus Body Design --- p.152Chapter 6.2.2 --- Wire-Driven Flapping Wing Design --- p.153Chapter 6.3 --- Flying Octopus Motion Control --- p.156Chapter 6.3.1 --- Propulsion Model --- p.156Chapter 6.3.2 --- Motion Control Strategy --- p.157Chapter 6.3.3 --- Motion Simulation --- p.159Chapter 6.4 --- Prototype and Indoor Experiments --- p.161Chapter 6.4.1 --- Flying Octopus Prototype --- p.161Chapter 6.4.2 --- Indoor Experiments --- p.163Chapter 6.4.3 --- Discussion --- p.165Chapter 6.5 --- Summary --- p.166Chapter Chapter 7 --- Conclusions and Future Work --- p.167Chapter Appendix A - --- Publication Record --- p.170Chapter Appendix B - --- Derivation --- p.172Chapter Appendix C --- Matlab Programs --- p.176References --- p.20

Robotic neuro-emdoscope with concentric tube augmentation

Surgical robots are gaining favor in part due to their capacity to reach remote locations within the body. Continuum robots are especially well suited for accessing deep spaces such as cerebral ventricles within the brain. Due to the entry point constraints and complicated structure, current techniques do not allow surgeons to access the full volume of the ventricles. The ability to access the ventricles with a dexterous robot would have significant clinical implications. This paper presents a concentric tube manipulator mated to a robotically controlled flexible endoscope. The device adds three degrees of freedom to the standard neuroendoscope and roboticizes the entire package allowing the operator to conveniently manipulate the device. To demonstrate the improved functionality, we use an in-silica virtual model as well as an ex-vivo anatomic model of a patient with a treatable form of hydrocephalus. In these experiments we demonstrate that the augmented and roboticized endoscope can efficiently reach critical regions that a manual scope cannot