Author: jeya

MRI-powered biomedical devices

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Abstract:

Magnetic resonance imaging (MRI) is beneficial for imaging-guided procedures because it provides higher resolution images and better soft tissue contrast than computed tomography (CT), ultrasound, and X-ray. MRI can be used to streamline diagnostics and treatment because it does not require patients to be repositioned between scans of different areas of the body. It is even possible to use MRI to visualize, power, and control medical devices inside the human body to access remote locations and perform minimally invasive procedures. Therefore, MR conditional medical devices have the potential to improve a wide variety of medical procedures; this potential is explored in terms of practical considerations pertaining to clinical applications and the MRI environment. Recent advancements in this field are introduced with a review of clinically relevant research in the areas of interventional tools, endovascular microbots, and closed-loop controlled MRI robots. Challenges related to technology and clinical feasibility are discussed, including MRI based propulsion and control, navigation of medical devices through the human body, clinical adoptability, and regulatory issues. The development of MRI-powered medical devices is an emerging field, but the potential clinical impact of these devices is promising.

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A hybrid FBG displacement and force sensor with a suspended and bent optical fiber configuration

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This paper has proposed a novel fiber Bragg grating (FBG)-based hybrid displacement and force sensor with a compact structure and excellent resolution by using the transverse property of a tightly suspended and slightly bent optical fiber. The optical fiber, embedded with an FBG element, has been suspended with its ends fixed on the sensor frame and implemented with a pre-tension force by the displacement loading along its vertical direction to form a bent shape. A conversion mechanism has been designed to convert the displacement and force inputs into the transverse movement of different points along the suspended fiber. Experimental results show that the displacement sensitivity and force sensitivity are −219.69 pm/mm within the range of 0–2.5 mm and −345.2 pm/N with a high calculated resolution of 2.9 mN, respectively. Results from both the displacement and force experiments have illustrated a close agreement with values from commercial sensors.

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Modular design and actuation system comparison for underactuated tendon-driven soft anthropomorphic robotic finger

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The objective of this project is to propose an alternative design for hyper-redundant, tendon-driven, discrete-joint manipulators which allows for independent removal of intermediate modules, as well as to conduct a comparative study between two alternative forms of tendon-driven actuation
systems, twisted string actuation and spooling actuation. Hyper-redundant discrete-joint manipulators have individual modules connected in series and when paired with a tendon-driven actuation system, intermediate modules cannot be isolated. This lack of modularity limits the ability to quickly replace intermediate modules without the need to disassemble the entire system. Efficacy of modularity is measured by the fastest time required to remove and add intermediate modules to a series of modules.
Comparison between maximum force generated by twisted string actuation and spooling actuation is done. The effects of different materials and diameter on the maximum force generated for twisted string actuation are also tested. Subjects are able to add and remove intermediate modules from the proposed design faster than a benchmark design. Twisted string actuation tests suggest that it is able to generate a larger force as compared to spooling actuation. Different string material and diameter are
also shown to affect the maximum force generated. If needed,further research should be done to better quantify factors which contribute to failure of the string in twisted string actuation.

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A Cable-Driven Flexible Robotic Grasper With Lego-Like Modular and Reconfigurable Joints

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This paper proposes a Modular and Reconfigurable Cable-driven robotic grasper (MoReCa Grasper) for grasping diverse unknown objects in unstructured environments, which integrates the characteristics of full actuation and under-actuation. The mechanical design of this robotic grasper is introduced with a focus on its Lego-like modular design feature and reconfigurable flexible joints. With these features, the length of this robotic grasper can be arbitrarily changed through the addition or removal of the Lego-like finger modules connected by magnets without rerouting or breaking the cables. The shape and degree of freedom (DOF) of the robotic grasper can be adjusted by changing the states of the joints using embedded clutches. When the joints are locked, the grasper can maintain its shape without additional power from actuators leading to better energy efficiency. The kinematics, workspace, and contact force are analyzed. On this basis, an automatically reshaping method (ARM) based on the motor’s current during the operation is proposed. Lastly, an example prototype of the robotic grasper with two fingers (four modules each), is built and tested. In the first experiment, the maximum grasping force is obtained. The second experiment demonstrates the ability of grasping diverse objects via changing the number of the modules and presetting the shape of the robotic grasper. The effectiveness of the ARM is verified in the third experiment.

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Open-Source Development of a Low-Cost Stereo-Endoscopy System for Natural Orifice Transluminal Endoscopic Surgery

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Abstract
As a minimally invasive procedure, Natural Orifice Transluminal Endoscopic Surgery (NOTES) offers many significant benefits over traditional open surgery, including reduced risks of post-operative complication and a faster recovery rate. However, one major challenge commonly faced when performing such procedures is the lack of depth perception provided by standard monocular endoscopes, which can in turn pose a limitation on the effectiveness of such endoscopic surgery. To overcome this undesirable lack of depth perception during endoscopic imaging, stereoscopic vision can be introduced into current endoscopy technology to assist surgeons in performing safer and faster operations with better depth judgement. While there is already a vast range of highly advanced stereo-endoscopy systems commercially available in the market, practical implementation of these systems still remains to be largely minimal as a result of their high costs. This paper presents our approach for integrating affordability with functionality, through the development of a simple, low-cost stereo-endoscopy system. Constructed using commonly off-the-shelf materials, the system runs in real time to present stereoscopic images acquired from the stereo-endoscope cameras into the surgeon’s eyes simultaneously, thereby equipping the surgeon with binocular vision for depth perception during endoscopic surgery.
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A bidirectional soft pneumatic fabric-based actuator for grasping applications

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THIS paper presents the development of a bidirectional fabric-based soft pneumatic actuator requiring low fluid pressurization for actuation, which is incorporated into a soft robotic gripper to demonstrate its utility. The bidirectional soft fabric-based actuator is able to provide both flexion and extension. Fabrication of the fabric actuators is simple as compared to the steps involved in traditional silicone-based approach. In addition, the fabric actuators are able to generate comparably larger vertical grip resistive force at lower operating pressure than elastomeric actuators and 3D-printed actuators, being able to generate resistive grip force up to 20N at 120 kPa. Five of the bidirectional soft fabric-based actuators are deployed within a five-fingered soft robotic gripper, complete with five casings and a base. It is capable of grasping a variety of objects with maximum width or diameter closer to its bending curvature. A cutting task involved bimanual manipulation was demonstrated successfully with the gripper. To incorporate intelligent control for such a task, a soft force made completely of compliant material was attached to the gripper, which allows determination of whether the cutting task is completed. To the authors’ knowledge, this work is the first study which incorporates two soft robotic grippers for bimanual manipulation with one of the grippers sensorized to provide closed loop control

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TTRE: A new type of error to evaluate the accuracy of a paired-point rigid registration

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Target registration error (TRE) is widely adopted to evaluate the accuracy of a paired-point rigid registration (PPRR). However, TRE is defined in such a way that target localization error (TLE) is not considered. In this paper, we first propose a new type of error that is referred to as total target registration error (TTRE). The statistical model of TTRE is derived that we take the TLE in two spaces to be registered into consideration. Results in the first simulation show that
the developed model can accurately estimate the simulated TTRE root-mean-square (RMS) (kRMS percent differencesk< 1.5% ±2%) in all test cases. When all elements of diagonal FLE and TLE covariance matrices are independently generated from a uniform distribution that spans from 0 to 1mm and the number of fiducials N≥6, the mean and covariance matrix of TTRE are well modelled. We have also theoretically proved and validated through the second simulation that TTRE and fiducial registration error (FRE) are uncorrelated (correlation coefficient (CC) <0.1). Finally, TTRE and TRE were found to exhibit a low correlation (0.37

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A High-Sensitivity Fiber Bragg Grating Displacement Sensor Based on Transverse Property of a Tensioned Optical Fiber Configuration and Its Dynamic Performance Improvement

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This paper presents a high-sensitivity fiber Bragg grating (FBG) displacement sensor with a novel configuration for structural health monitoring. The transverse movement of an optical fiber that has been configured as a tight suspension status with its two ends fixed has been utilized to measure displacement. The theoretical models for both static and dynamic displacements have been derived. The corresponding simulations have been conducted to determine the relationship between the model parameters and the sensor performance. This approach supports the sensor design improvement and structural optimization. Two small working ranges have been selected to determine the simplified linear model according to Taylor series. The sensitivity of this sensor can reach up to 490.1 pm/mm with a high resolution of 2.04 μ m in a range of 1.4~2.0 mm. The introduction of the supporting spring unit has significantly enhanced the sensor’s resonant frequency without sacrificing the sensitivity. The application of the stiffer spring unit has enlarged the working bandwidth from 0~8 Hz to exceed 50 Hz. Enhancing the damping ratio unit can effectively improve the flatness of the dynamic response within the working bandwidth, while it does not affect other dynamic properties of the sensor. These improvements and design guidelines have been validated by both dynamic experiments and theoretical modelling.

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Development of flexible fabric based tactile sensor for closed loop control of soft robotic actuator

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The ability to sense and measure object properties based on touch is known as tactile sensing. The flexibility and dexterity of soft robots can be fully explored, only with efficient tactile feedback from the environment or the objects the robot interact with. This paper discusses about the development of a soft fabric based piezoresistive tactile sensor, the related calibration experiments and procedures. Fabric based sensors are flexible, stretchable and can confer to both hard and soft
surfaces easily. The ability of the tactile sensor to enhance the efficiency of robotic activities is demonstrated in a simple cutting task. The robotic end effector used is a pneumatically controlled soft gripper. Experimental results show that the feedback from the tactile sensor developed is successfully used to detect the completion of the cutting tas

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Viscoelastic Model Based Bilateral Teleoperation for Robotic-assisted Tele-palpation

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The purpose of this paper is to design a model-based bilateral teleoperation method to improve the feedback force and velocity/position tracking for robotic-assisted tasks (such as palpation, etc.) under constant and/or varying time delay with environment dynamic property. Time delay existing in bilateral teleoperation easily destabilizes the system. Proper control strategies are able to make the system stable, but at the cost of compromised performance. Model-based bilateral teleoperation is designed to achieve enhanced performance of this time-delayed system, but an accurate model is required. Design/methodology/approach Viscoelastic model has been used to describe the robot tool-soft tissue interaction behavior. Kevin-Boltzmann (K-B) model is selected to model the soft tissue behavior due to its good accuracy, transient and linearity properties among several viscoelastic models. In this work, the K-B model is designed at the master side to generate a virtual environment of remote robotic tool-soft tissue interaction. In order to obtain improved performance, a self perturbing recursive least square (SPRLS) algorithm is developed to on-line update the necessary parameters of the environment with varying dynamics. Findings With fast and optimal on-line estimation of primary parameters of the K-B model, the reflected force of the model-based bilateral teleoperation at the master side is improved as well as the position/velocity tracking performance. This model-based design in the bilateral teleoperation avoids the stability issue caused by time delay in the communication channel since the exchanged information become position/velocity and estimated parameters of the used model. Even facing with big and varying time delay, the system keeps stably and enhanced tracking performance. Besides, the fast convergence of the SPRLS algorithm helps to track the time-varying dynamic of the environment, which satisfies the surgical applications as the soft tissue properties usually are not static. Originality/value The originality of this work lies in that an enhanced perception of bilateral teleoperation structure under constant/varying time delay that benefits robotic assisted tele-palpation (time varying environment dynamic) tasks is developed. With SPRLS algorithm to on-line estimate the main parameters of environment, the feedback perception of system can be enhanced with stable velocity/position tracking. The superior velocity/position and force tracking performance of the developed method makes it possible for future robotic-assisted tasks with long-distance communication.

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