Author: venkatesh

Shape Sensing Techniques for Continuum Robots in Minimally Invasive Surgery: A Survey

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Continuum robots provide inherent structural compliance with high dexterity to access the surgical target sites along tortuous anatomical paths under constrained environments, and enable to perform complex and delicate operations through small incisions in minimally invasive surgery. These advantages enable their broad applications with minimal trauma, and make challenging clinical procedures possible with miniaturized instrumentation and high curvilinear access capabilities. However, their inherent deformable designs make it difficult to realize three-dimensional (3D) intraoperative real-time shape sensing to accurately model their shape. Solutions to this limitation can lead themselves to further develop closely associated techniques of closed-loop control, path planning, human–robot interaction and surgical manipulation safety concerns in minimally invasive surgery. Although extensive model-based research that relies on kinematics and mechanics has been performed, accurate shape sensing of continuum robots remains challenging, particularly in cases of unknown and dynamic payloads. This survey investigates the recent advances in alternative emerging techniques for 3D shape sensing in this field, and focuses on the following categories: fiber optic sensors based, electromagnetic tracking based and intraoperative imaging modalities based shape reconstruction methods. The limitations of existing technologies and prospects of new technologies are also discussed.

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Data-Defect Inspection With Kernel-Neighbor-Density-Change Outlier Factor

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Data-defect would affect the data quality and the analysis results of data mining. This paper presents a data-defect inspection method with kernel-neighbor-density-change outlier factor (KNDCOF). The definition of kernel neighbor density is proposed to represent the density of each object in database, and the ascending distance series (ADS) of each object is calculated based on the kernel distance between the object and its neighbors. Then, the average density fluctuation (ADF) of the object is established according to the weighted sum of the square of density difference between the object and others in ADS. Finally, the KNDCOF of the object is equal to the ratios of the ADF of the object and the average ADF of neighbors of the object. The degree of the object being an outlier is indicated by the KNDCOF value. The experiments are performed on three real data sets to evaluate the effectiveness of the proposed method. The experimental results verify that the proposed method has higher quality of data-defect inspection and does not increase the time complexity.

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Positioning evaluation of tendon-driven flexible manipulators based on interval analysis

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Tendon-driven flexible manipulators have diverse applications. However, kinematic errors are one of main sources of the positioning inaccuracy for the manipulators. An interval-Analysis-based approach is applied to evaluate the positioning performance by imposing bounds on the kinematic parameters and control input. Simulation results confirm that the calculated intervals and refined bounds fully enclose the tip positions.

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Analysis of Principle and Performance of a New 4DOF Hybrid Magnetic Bearing

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To satisfy the requirement of magnetically suspended control moment gyroscope (MSCMG) that magnetic bearing can provide torque, a novel 4DOF hybrid magnetic bearing (HMB) with integrated structure was designed. Mathematical models of forces and torques are established by using equivalent magnetic circuit method. The current stiffness, displacement stiffness, tilting current stiffness and angular stiffness of the 4DOF hybrid magnetic bearing are derived by the mathematical models. Equivalent magnetic circuit method and finite element method (FEM) simulation results indicate that the force has a good linear relationship with both displacement and current, and the torque has a good linear relationship with angular displacement and current. The novel 4DOF HMB is capable of achieving control in both two radial translational degrees of freedom (DOF) and also two radial rotational DOFs. The 4DOF HMB is well adapted to MSCMG system, exhibiting advantages in the controllable DOF, light weight and easy to control.

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Investigation of a Stiffness Varying Mechanism for Flexible Robotic System

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With the advent of automation and robotic systems, robotic manipulators are becoming increasingly popular in various industries. This project aims to investigate stiffness varying technology for a class of flexible manipulators with the aim of online changing manipulator stiffness. We propose and develop a stiffness varying mechanism based on Polycaprolactone (PCL), characterize it and test out together with extensive experiments. This mainly involves design improvement, modeling, characterization and hands-on experiments.

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Reduction of Power Consumption for Fluidic Soft Robots Using Energy Recovery Technique

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Power-efficient fluidic driven system is beneficial to extending the working time of autonomous and wearable soft robots supplied by independent power sources such as batteries. In this paper, an energy recovery scheme is proposed to reutilize the pressurized air released by retracting pneumatic soft actuators instead of venting to atmosphere. The scheme’s novelty lies in an air accumulator employed to store the recovered energy and boost the inlet pressure of air pumps when there is requirement. Then the energy-saving principle is described based on the comparison of energy flow between the systems with and without energy recovery. Residual pressure, recoverable energy and parametric effect are also presented analytically according to the ideal gas law. Finally, simulation models are developed to evaluate the system performance and the results show that about 20% reduction of power consumption and acceptable residual pressure can be achieved simultaneously when the accumulator volume is three times of the actuator volume, which provides reference to further prototype development. Index Terms – Soft robotics, fluidic driven system, energy recovery, parameter design, air accumulator.

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An adjusted dipole model for rectangular electromagnetic coils

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Magnetic actuation is an efficient way for remote wireless control of micro-robots. One key factor for efficient actuation is an accurate mapping of the magnetic field components and the field gradients that generated by the magnetic sources. Usually, magnetic dipole model or interpolation method is used to estimate the magnetic field. These methods are not well suited for the control of micro-robots by electromagnetic coils. In this paper, we present an adjusted magnetic dipole model for the rectangular electromagnetic coil. The proposed adjusted dipole model is based on the magnetic dipole model. This model can provide accurate estimation of the magnetic field and gradient, meanwhile simplifying the calculation. Experimental results show that the proposed model work well and better than the original magnetic dipole model.

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Development of a Multi-Channel Concentric Tube Robotic System With Active Vision for Transnasal Nasopharyngeal Carcinoma Procedures

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Minimally invasive surgery-based nasopharyngeal cancer treatment is promising, but currently, it is not a common treatment choice because of the absence of suitable tools. In this paper, a multi-channel concentric tube robot is proposed for the treatment of nasopharyngeal cancer based on natural orifice translumenal endoscopic surgery. The proposed system has three channels, i.e. two manipulation channels and one vision channel, and all the three channels are confined by a 10 mm active sheath. The robot is controlled by human-in-the-loop bimanual teleoperation under active endoscopic guidance. The reduced sheath diameter and the steerable vision channel improve the functionality of the system and distinguish our design from the prior art. The feasibility of the system has been evaluated through a series of simulations and experiments. Results show that the proposed system is capable to conduct cooperative tasks in a confined space and the miniaturized manipulator is suitable for transnasal procedures. Besides, comparisons with other types of flexible surgical robots are discussed to further demonstrate the superiority of the proposed system in the target clinical applications.

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A Miniature Soft Robotic Manipulator Based on Novel Fabrication Methods

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Flexible robotic manipulators have been widely used in minimally invasive surgery (MIS) and many other applications requiring closer inspection and operation. Although a variety of manipulators enabled by different mechanism have been developed, few of them can preserve softness, thinness, and decent bending capability simultaneously. In this letter, we present a miniature soft robotic manipulator made of hyper-elastic silicone rubber. Along with the manipulator design, two novel fabrication methods are proposed and elaborated. Detailed characterizations are specified to show the bending capability of the manipulator given different air pressure. Specifically, our manipulator, as thin as 6 mm, is able to achieve 360° directional bending, and, when given pressure over 70 kPa, it can reach 180° bending angle and around 5 mm bending radius easily. Due to its innate compliance and small dimension, this type of robotic manipulator can deliver safe and comfortable interactions with the subjects. More significantly, the novel fabrications in this letter diversify the fabrication methods for soft pneumatic robots and actuators (SPRA) and further scale down their sizes.

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A Magnetically actuated guide-wire steering system towards arteriovenous fistula angioplasty procedures

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Working towards remote steering of distal guide-wire in arteriovenous fistula angioplasty procedures, we develop a magnetically actuated robotic guide-wire manipulation system involving electromagnetic coils and a flexible guide-wire with a magneto-responsive attachment. By varying the coil voltages, we show the controlled deflections of the distal guide-wire. Specifically we are investigating the guidewire actuation mechanism under controlled electromagnetic field, the transfer function of the system, and the steering experiments in a custom phantom. The studied phenomenon has importance for guide-wire placement in minimally invasive cardio-vascular surgeries. A video demonstration is available at: http://bioeng.nus.edu.sg/mm/magnetically-actuated-guide-wire-steering.

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