Modeling, analysis, and design for magnetic levitation with unlimited roll and pitch rotations and a pen-shaped haptic interface handle

M.S. University of Hawaii at Manoa 2012.Includes bibliographical references.This paper describes two different designs; an unlimited roll and pitch design and a pen-shaped haptic interface design, of a magnetic levitation system developed at the human robot interaction lab in University of Hawaii at Manoa. With a previous coil and magnet setup, a levitated body that contained two permanent magnets was able to be operated at a maximum height of 31 mm (25 mm air gap) and rotated up to 40 degrees both in roll and pitch with unlimited yaw. As a result of modeling forces and torques and evaluating required coil currents and condition numbers of different shapes, sizes, orientations, and configurations of magnets over various coil configurations, a setup that consists of an array of twenty seven coils and a levitated object that contains six permanent magnets was designed. The setup achieved levitation in 6 degrees of freedom and unlimited roll, pitch, and yaw rotation was performed at a fixed height of 42 mm (6 mm air gap). In addition, a high response pen shape haptic interface with two permanent magnets was fabricated for interactive computer simulations and its performance was verified with a levitation trajectory following

A Low-Cost, Point-of-Care Test for Confirmation of Nasogastric Tube Placement via Magnetic Field Tracking

In this work, we aim to achieve low-cost real-time tracking for nasogastric tube (NGT) insertion by using a tracking method based on two magnetic sensors. Currently, some electromagnetic (EM) tracking systems used to detect the misinsertion of the NGT are commercially available. While the EM tracking systems can be advantageous over the other conventional methods to confirm the NGT position, their high costs are a factor hindering such systems from wider acceptance in the clinical community. In our approach, a pair of magnetic sensors are used to estimate the location of a permanent magnet embedded at the tip of the NGT. As the cost of the magnet and magnetic sensors is low, the total cost of the system can be less than one-tenth of that of the EM tracking systems. The experimental results exhibited that tracking can be achieved with a root mean square error (RMSE) of 2–5 mm and indicated a great potential for use as a point-of-care test for NGT insertion, to avoid misplacement into the lung and ensure correct placement in the stomach

Cable Driven Robots: Hysteretic Cable Stretch, Cable-Pulley Network Friction, Fatigue Life, and Kinematics of Two-Arm Multi Staged Flexible Manipulator

Thesis (Ph.D.)--University of Washington, 2017-06Cable driven mechanisms face control challenges associated with hysteretic response of cable and dynamic friction from guide pulleys due to variable cable tension. In this thesis, a new dynamic models of cable driven mechanism, cable-pulley network friction and hysteretic stretch of longitudinally loaded cable, are developed in order to improve control accuracy and robustness. Moreover, fatigue life of cable is investigated and a prediction model is presented which can ensure safe operation of the robot. The specifications used for the experimental setups for the model development are based on the RAVEN II cable driven surgical robot and the model verification was performed using the same system. This thesis also presents the kinematics of the Roboscope, surgical robot for skullbase surgery and neurosurgery. The system has two-arm flexible cable driven manipulator which faces coupling effect. Detailed kinematics the system with the coupling effect is developed and analyzed

A frictional contact-pattern-based model for inserting a flexible shaft into curved channels

Flexible endoscopy and catheterization typically involve inserting a flexible shaft into a curved channel. Understanding the mechanics involved in the insertion process is crucial for the structural design, actuation, sensing, control, and navigation of these flexible medical tools. However, the everchanging contacts and friction between the insertion shaft and the pathway make the mechanics complicated. Existing analytical models simplify the problem by neglecting the friction and assuming specific boundary conditions that are valid only in a few specific instances. In the meantime, FEM models have trade-offs between computation speed, accuracy, and stability. This paper presents an efficient theoretical framework to model the insertion process with friction, promoting fast and accurate computation of the mechanics involved. The inserting shaft is segmented based on the evolving contacts; system equations are formulated with friction-included force equilibrium and boundary conditions. The model is verified through experiments; channels with different shapes/curvatures were considered. The root-mean-square errors between the model and measured insertion forces are less than 0.055N (average percentage error less than 9.62%). This model will enhance the fundamental understanding of the insertion process's mechanics and benefit the engineering (design, actuation, and control) and medical practices of related medical tools (e.g., endoscopic instruments and catheters).National Research Foundation (NRF)Accepted versionThis work was supported by National Research Foundation (NRF) Singapore under Grant NRFI2016-07

Pneumatically actuated deployable tissue distension device for NOTES for colon

When performing some surgical tasks inside colon with NOTES technology, colon tissue could block the task space and occlude the endoscopic vision. In order to solve this problem, we developed a pneumatically driven deployable and undeployable structure which can distend collapsing tissue and can be delivered through a 4.5 mm endoscopic channel. The structure is designed to be flexible enough to pass through colon's tortuous pathway. Also, it is designed to hold its shape without continually applying air pressure after deployment. This allows to make use of an endoscopic channel for the other surgical instruments. Besides, due to the compliant nature of the device, it is safe to deploy inside a smaller space than its maximum deployable size. The functionality of the device was verified with an in-vitro experiment. The structure was successfully deployed inside a pig's colon with an inner diameter of 60 mm by applying 3.5 bars of air pressure and created a sufficient task space for surgical operations.NRF (Natl Research Foundation, S’pore)Accepted versio

A low-cost, point-of-care test for confirmation of nasogastric tube placement via magnetic field tracking

In this work, we aim to achieve low-cost real-time tracking for nasogastric tube (NGT) insertion by using a tracking method based on two magnetic sensors. Currently, some electromagnetic (EM) tracking systems used to detect the misinsertion of the NGT are commercially available. While the EM tracking systems can be advantageous over the other conventional methods to confirm the NGT position, their high costs are a factor hindering such systems from wider acceptance in the clinical community. In our approach, a pair of magnetic sensors are used to estimate the location of a permanent magnet embedded at the tip of the NGT. As the cost of the magnet and magnetic sensors is low, the total cost of the system can be less than one-tenth of that of the EM tracking systems. The experimental results exhibited that tracking can be achieved with a root mean square error (RMSE) of 2-5 mm and indicated a great potential for use as a point-of-care test for NGT insertion, to avoid misplacement into the lung and ensure correct placement in the stomach.Nanyang Technological UniversityPublished versionThis research was funded by Nanyang Technological University start up grant number M4081419

First-in-man feasibility study of a novel ingestible magnetically inflated balloon capsule for treatment of obesity

Intragastric balloons (IGBs) are an established treatment option for obesity. Major barriers to dissemination of IGBs include lack of long-term efficacy outcomes, safety concerns, cost, and tolerability. We developed a novel ingestible magnetically inflated balloon capsule (IMI-BC) in hopes of overcoming these challenges. The IMI-BC is significantly cheaper than IGBs currently available on the market. We performed proof-of-concept animal studies and a first-in-human feasibility study to demonstrate the feasibility of inflating the IMI-BC using an external magnet. Further studies are currently being conducted to evaluate the safety, tolerability, and long-term efficacy of the IMI-BC. When fully developed, we anticipate that this device will benefit obese patients.Published versio

Two magnetic sensor based real-time tracking of magnetically inflated swallowable intragastric balloon

This paper presents a two magnetic sensor based tracking method for a magnetically inflated intragastric balloon capsule (MIBC) which is used for obesity treatment. After the MIBC is swallowed, it is designed to be inflated inside the stomach by approaching a permanent magnet (PM) externally near the abdomen. However, if the balloon inflation is accidentally triggered while the MIBC is still in the esophagus, the esophagus will be damaged. Therefore, to safely inflate the MIBC, we aim to track the MIBC's position along the esophagus and confirm the MIBC passes through. Typically, magnetic sensor based tracking systems tend to be bulky and costly since they involve computationally intensive optimization with many magnetic sensors. To solve those problems, we develop an algorithm that estimates the position of the PM inside the MIBC by using the grid search combined with the dynamically confined search range and search threshold modulation. Our tracking method achieved an average 1D position error of 3.48 mm which is comparable to the up to 4 mm average error for the other magnetic sensor based tracking systems that require more sensors and computational power compared to our system.Nanyang Technological UniversityThis research is supported by Nanyang Technological University (Start up Grant M4081419)

EndoPil: a magnetically actuated swallowable capsule for weight management: development and trials

Intragastric balloons (IGBs), by occupying the stomach space and prolonging satiety, is a promising method to treat obesity and consequently improves its associated comorbidities, e.g. coronary heart disease, diabetes, and cancer. However, existing IGBs are often tethered with tubes for gas or liquid delivery or require endoscopic assistance for device delivery or removal, which are usually uncomfortable, costly, and may cause complications. This paper presents a novel tetherless, magnetically actuated capsule (EndoPil) which can deploy an IGB inside the stomach after being swallowed and being activated by an external magnet. The external magnet attracts a small magnet inside the EndoPil to open a valve, triggering the chemical reaction of citric acid and potassium bicarbonate to produce carbon dioxide gas, which inflates a biocompatible balloon (around 120 mL). A prototype, 13 mm in diameter and 35 mm in length, was developed. Simulations and bench-top tests were conducted to test the force capability of the magnetic actuation mechanism, the required force to activate the valve, and the repeatability of balloon inflation. Experiments on animal and human were successfully conducted to demonstrate the safety and feasibility of inflating a balloon inside the stomach by an external magnet.Nanyang Technological UniversityThe study is funded by the Gastroenterology Research Fund in Singapore (NUS WBS No. R-172-000-004-720) and the Startup Grant from Nanyang Technological University, Singapore (NTU WBS No. M4081419)