19 research outputs found
Design and implementation of DSP-based magnetic control system for capsule endoscope
PhD ThesisEarly detection methods are key to reducing morbidity rates from digestive
tract cancer which is currently one of the fastest growing cancers
in the World. Capsule endoscopes (CEs) are a new technology that can
be used to improve early detection of the gastrointestinal (GI) tract disorder.
The device integrates the technologies such as image processing,
optoelectronic engineering, information communication, and biomedical
engineering. The capsule is the size and shape of a pill and contains an
optoelectronic camera, antenna, transmitter, battery and optoelectronic
illuminating light emitting diodes (LEDs).
The small size of these devices enables them to offer many advantages
over conventional endoscopes such as accessibility to the entire intestine
and minimising the risk of perforation, particularly for patients with difficult
anatomy (e.g. post-operative scar tissue). Currently used devices
are passive and can only follow the natural transit of the intestines, and
hence there is considerable interest in methods of controlled actuation
for these devices.
In this thesis, a novel actuation system based on magnetic levitation
is designed, developed and implemented, utilizing a small permanent
magnet embedded within the capsule and an arrangement of digitally
controlled electromagnets outside the body. The proposed approach is
that the magnet can be moved and oriented by DC magnetic force and
torque produced by coils placed outside of the human body, with a suitable
position feedback sensor enabling closed-loop control. Theoretical
analyses of the proposed actuation system are presented which model
the magnetic field, force and torque exerted by electromagnetic coil on
the embedded magnet. Based on the distribution of the magnetic field,
an optimal geometry for the coils is proposed in order to achieve a levitation
distance which is realistic for the inspection of the GI tract.
Two types of systems are investigated in the thesis, namely single-input
single-output (SISO) and multi-input multi-output (MIMO), and the
dynamics of these systems are modelled in state space form and hence
linear controllers are designed for capsule actuation. The controllers
are simulated using Matlab/ Simulink tools to realize the mathematical
analysis of the system, and then implemented digitally in real-time using
Texas Instruments (TI) TMS320F2812 Digital Signal Processor (DSP)
to validate the proposed actuation system.
In the SISO system, a linear one degree of freedom (1DOF) proportionalintegral-
derivative (PID) controller is designed to move the inserted magnet
in the vertical dimension within an area around the operating point
and to maintain it at a desired position. A realistic simulation model is
designed and implemented to evaluate the proposed controller. Simulation
results have shown that the controller is able to successfully hold the
embedded magnet in the desired position. For practical validation, the
PID controller is implemented in real-time on the DSP system, where
pulse width modulation (PWM) is generated to control the coil current,
and Hall effect sensors are used for position feedback. Experimental results
are obtained under step and square wave input demand.
In the proposed system, high frequency noise on the position sensor is
initially rejected by hardware implementation of resistor capacitor-low
pass filter (RC-LPF) circuit. The accuracy of the position feedback
is increased by calibrating the DSP’s on-chip analogue-digital converter
(ADC) in order to reduce conversion error due to inherent gain and offset
errors. To further reduce the influence of the position feedback noise, an
average of ten repeated samples based on mean filter is implemented by
the DSP in order to reduce the influctuation of the sensor reading. The
tracking performance of the actuation system based on two Hall effect
sensors on the opposite coil’s poles is investigated under step trajectory
input. In an improved actuation system, position feedback is provided by
using an AC magnetic field to obtain the capsule position information,
decoupling this from the DC actuation field. The noise of the position
feedback in the improved system is reduced by replacing the PWM current
drive with a linear power amplifier driven from a digital to analogue
converter (DAC), hence reducing AC interference. Positioning sensor
noise was found to be further reduced by implementing digital filtering
based on a coherent detector using the DSP, without increasing response
time. The performance of the actuation system using these position sensors
is compared based on settling time, overshoot, steady-state error,
and control input parameters in order to validate the proposed improvement
in the position feedback. The experimental results have shown that
the controller based on both sensing strategies satisfactory control of the
magnet’s position. However, the response of the system based on AC
position sensing has the shortest settling time, smallest overshoot value
and steady-state error.
In the MIMO system, several linear controllers such as pole placement
(PP), Entire Eigenstructure Assignment (EEA), and linear Quadratic
regulator (LQR) techniques are designed and their tracking performances
are compared. Simulation results have shown that, based on acceptable
control inputs, the LQR controller has the fastest response with minimal
overshoot value and steady state error. However, the LQR controller
based on 2DOF is unable to maintain stable control of the magnet due
to the insufficient position feedback from the two coil sensors.
Specifically, it is not possible to achieve a stable 2D system since the orientation
angle of the magnet is not resolvable. Therefore, the position
feedback is improved by obtaining the device position and orientation
information from a pair of 3-axis orthogonal coils. A realistic simulation
model for the 3DOF LQR controller is designed and implemented
to evaluate the developed system. Simulation results have shown that
this controller is can achieve the necessary stability.
In conclusion, based on the results from the 1D control system, the thesis
shows that the DC magnetic field, which is used for capsule movement,
can be also used to provide the controller acceptable position feedback.
However, the use of AC magnetic field for positioning purpose provides
more accurate position information. In order to implement 2DOF control
system successfully, two 3-axis orthogonal coil sensors are considered
which are used to provide the actuation algorithm with more accurate
feedback of position and orientation information.Ministry of Higher Education, Iraq
Design of optimised linear quadratic regulator for capsule endoscopes based on artificial bee colony tuning algorithm
Wireless Capsule Endoscope (WCE) is a new medical device that can be used for examining the whole digestive tract if effectively actuated. In this paper, a new three-coil actuator is proposed for the capsule endoscope navigation system. The proposed system, which is based on the currentcontrolled magnetic levitation concept, utilises a small permanent magnet within the capsule body and an arrangement of controlled electromagnet actuator placed on a movable frame. The dynamics of the proposed control system is modelled mathematically and then formulated in state space form. In this research, the Linear Quadratic Regulator (LQR) technique is used for designing a 3DOF controller for the capsule actuation system. Artificial Bee Colony (ABC) tuning algorithm is used for obtaining optimum values for controller gain parameters. The optimised LQR controller is simulated by using the Matlab/Simulink tool, and its performance is then evaluated based on the stability and control effort parameters to validate the proposed system. Finally, the simulation results suggest that the LQR controller based on the ABC optimisation method can be adopted to synthesise an effective capsule actuation system
Active Stabilization of Interventional Tasks Utilizing a Magnetically Manipulated Endoscope
Magnetically actuated robots have become increasingly popular in medical endoscopy over the past decade. Despite the significant improvements in autonomy and control methods, progress within the field of medical magnetic endoscopes has mainly been in the domain of enhanced navigation. Interventional tasks such as biopsy, polyp removal, and clip placement are a major procedural component of endoscopy. Little advancement has been done in this area due to the problem of adequately controlling and stabilizing magnetically actuated endoscopes for interventional tasks. In the present paper we discuss a novel model-based Linear Parameter Varying (LPV) control approach to provide stability during interventional maneuvers. This method linearizes the non-linear dynamic interaction between the external actuation system and the endoscope in a set of equilibria, associated to different distances between the magnetic source and the endoscope, and computes different controllers for each equilibrium. This approach provides the global stability of the overall system and robustness against external disturbances. The performance of the LPV approach is compared to an intelligent teleoperation control method (based on a Proportional Integral Derivative (PID) controller), on the Magnetic Flexible Endoscope (MFE) platform. Four biopsies in different regions of the colon and at two different system equilibria are performed. Both controllers are asked to stabilize the endoscope in the presence of external disturbances (i.e. the introduction of the biopsy forceps through the working channel of the endoscope). The experiments, performed in a benchtop colon simulator, show a maximum reduction of the mean orientation error of the endoscope of 45.8% with the LPV control compared to the PID controller
Balancing a Segway robot using LQR controller based on genetic and bacteria foraging optimization algorithms
A two-wheeled single seat Segway robot is a special kind of wheeled mobile robot, using it as a human transporter system needs applying a robust control system to overcome its inherent unstable problem. The mathematical model of the system dynamics is derived and then state space formulation for the system is presented to enable design state feedback controller scheme. In this research, an optimal control system based on linear quadratic regulator (LQR) technique is proposed to stabilize the mobile robot. The LQR controller is designed to control the position and yaw rotation of the two-wheeled vehicle. The proposed balancing robot system is validated by simulating the LQR using Matlab software. Two tuning methods, genetic algorithm (GA) and bacteria foraging optimization algorithm (BFOA) are used to obtain optimal values for controller parameters. A comparison between the performance of both controllers GA-LQR and BFO-LQR is achieved based on the standard control criteria which includes rise time, maximum overshoot, settling time and control input of the system. Simulation results suggest that the BFOA-LQR controller can be adopted to balance the Segway robot with minimal overshoot and oscillation frequency
3 Dimensional Dense Reconstruction: A Review of Algorithms and Dataset
3D dense reconstruction refers to the process of obtaining the complete shape
and texture features of 3D objects from 2D planar images. 3D reconstruction is
an important and extensively studied problem, but it is far from being solved.
This work systematically introduces classical methods of 3D dense
reconstruction based on geometric and optical models, as well as methods based
on deep learning. It also introduces datasets for deep learning and the
performance and advantages and disadvantages demonstrated by deep learning
methods on these datasets.Comment: 16 page
Bounds on RF cooperative localization for video capsule endoscopy
Wireless video capsule endoscopy has been in use for over a decade and it uses radio frequency (RF) signals to transmit approximately fifty five thousands clear pictures of inside the GI tract to the body-mounted sensor array. However, physician has no clue on the exact location of the capsule inside the GI tract to associate it with the pictures showing abnormalities such as bleeding or tumors. It is desirable to use the same RF signal for localization of the VCE as it passes through the human GI tract. In this thesis, we address the accuracy limits of RF localization techniques for VCE localization applications. We present an assessment of the accuracy of cooperative localization of VCE using radio frequency (RF) signals with particular emphasis on localization inside the small intestine. We derive the Cramer-Rao Lower Bound (CRLB) for cooperative location estimators using the received signal strength(RSS) or the time of arrival (TOA) of the RF signal. Our derivations are based on a three-dimension human body model, an existing model for RSS propagation from implant organs to body surface and a TOA ranging error model for the effects of non-homogenity of the human body on TOA of the RF signals. Using models for RSS and TOA errors, we first calculate the 3D CRLB bounds for cooperative localization of the VCE in three major digestive organs in the path of GI tract: the stomach, the small intestine and the large intestine. Then we analyze the performance of localization techniques on a typical path inside the small intestine. Our analysis includes the effects of number of external sensors, the external sensor array topology, number of VCE in cooperation and the random variations in transmit power from the capsule
Antenna Systems
This book offers an up-to-date and comprehensive review of modern antenna systems and their applications in the fields of contemporary wireless systems. It constitutes a useful resource of new material, including stochastic versus ray tracing wireless channel modeling for 5G and V2X applications and implantable devices. Chapters discuss modern metalens antennas in microwaves, terahertz, and optical domain. Moreover, the book presents new material on antenna arrays for 5G massive MIMO beamforming. Finally, it discusses new methods, devices, and technologies to enhance the performance of antenna systems
Control techniques for mechatronic assisted surgery
The treatment response for traumatic head injured patients can be improved by
using an autonomous robotic system to perform basic, time-critical emergency neurosurgery,
reducing costs and saving lives. In this thesis, a concept for a neurosurgical robotic system is proposed to perform three specific emergency neurosurgical procedures; they are the placement of an intracranial pressure monitor, external
ventricular drainage, and the evacuation of chronic subdural haematoma. The control
methods for this system are investigated following a curiosity led approach. Individual problems are interpreted in the widest sense and solutions posed that are general in nature. Three main contributions result from this approach: 1)
a clinical evidence based review of surgical robotics and a methodology to assist in their evaluation, 2) a new controller for soft-grasping of objects, and 3) new propositions and theorems for chatter suppression sliding mode controllers. These contributions directly assist in the design of the control system of the neurosurgical robot and, more broadly, impact other areas outside the narrow con nes of the target application. A methodology for applied research in surgical robotics is proposed. The methodology sets out a hierarchy of criteria consisting of three tiers, with the most important being the bottom tier and the least being the top tier. It is argued that
a robotic system must adhere to these criteria in order to achieve acceptability. Recent commercial systems are reviewed against these criteria, and are found to conform up to at least the bottom and intermediate tiers. However, the lack of
conformity to the criteria in the top tier, combined with the inability to conclusively
prove increased clinical benefit, particularly symptomatic benefit, is shown to be hampering the potential of surgical robotics in gaining wide establishment. A control scheme for soft-grasping objects is presented. Grasping a soft or fragile object requires the use of minimum contact force to prevent damage or deformation. Without precise knowledge of object parameters, real-time feedback
control must be used to regulate the contact force and prevent slip. Moreover, the controller must be designed to have good performance characteristics to rapidly modulate the fingertip contact force in response to a slip event. A fuzzy sliding mode controller combined with a disturbance observer is proposed for contact force control and slip prevention. The robustness of the controller is evaluated through
both simulation and experiment. The control scheme was found to be effective and robust to parameter uncertainty. When tested on a real system, however, chattering phenomena, well known to sliding mode research, was induced by the
unmodelled suboptimal components of the system (filtering, backlash, and time delays). This reduced the controller performance. The problem of chattering and potential solutions are explored. Real systems using sliding mode controllers, such as the control scheme for soft-grasping, have a tendency to chatter at high frequencies. This is caused by the sliding mode
controller interacting with un-modelled parasitic dynamics at the actuator-input
and sensor-output of the plant. As a result, new chatter-suppression sliding mode controllers have been developed, which introduce new parameters into the system. However, the effect any particular choice of parameters has on system performance
is unclear, and this can make tuning the parameters to meet a set of performance
criteria di cult. In this thesis, common chatter-suppression sliding mode control
strategies are surveyed and simple design and estimation methods are proposed.
The estimation methods predict convergence, chattering amplitude, settling time,
and maximum output bounds (overshoot) using harmonic linearizations and invariant
ellipsoid sets