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

A survey of small bowel modelling and its applications for capsule endoscopy

This is the final version. Available on open access from Elsevier via the DOI in this recordThe small intestine, an anatomical site previously considered inaccessible to clinicians due to its small diameter and length, is the part of the gastrointestinal tract between the stomach and the colon. Since its introduction into clinical practice two decades ago, capsule endoscopy has become established as the primary modality for examining the surface lining of the small intestine. Today, researchers continue to develop ground-breaking technologies for novel miniature devices aiming for tissue biopsy, drug delivery and therapy. The purpose of this paper is to provide researchers and engineers in this area a comprehensive review of the progress in understanding the anatomy and physiology of the small intestine and how this understanding was translated to virtual and physical test platforms for assessing the performance of these intestinal devices. This review will cover both theoretical and practical studies on intestinal motor activities and the work on mathematical modelling and experimental investigation of capsule endoscope in the small intestine. In the end, the requirements for improving the current work are drawn, and the expectations on future research in this field are provided.Engineering and Physical Sciences Research Council (EPSRC)China Scholarship Counci

A new capsule-intestine model for the capsule robot self-propelling in the lower gastrointestinal tract

This is the author accepted manuscript. The final version is available on open access from Elsevier via the DOI in this recordData availability: Data will be made available on request.Circular and haustral folds in the lower gastrointestinal tract (small and large intestines) are the major obstructions impeding the locomotion of the capsule robots for endoscopic diagnosis. Understanding the interactions between the capsule and these folds is critical for design and control of these robots to reach the areas of clinical interest. This paper proposes a new mathematical model of capsule-intestine interaction based on our previous work (Yan et al. 2022) by introducing capsule’s rotation during fold crossing. The resisting force of the fold predicted by the new model is more consistent with our finite element and experimental results compared to our previous model. It is found that the obstructive effect of the fold is stronger for a higher and thinner fold with a thinner and stiffer intestine. For the capsule robot, which is actuated by a periodically driven inner mass, a stronger excitation force is required to overcome the fold with a larger resisting force. Moreover, our bifurcation analysis reveals that a small excitation force always incurs a simple period-1 motion for the robot, while a large excitation force may result in various complex dynamics before the fold crossing. The findings of this work may help capsule robotics engineers to evaluate their designs in terms of propulsion and understand the locomotion of their robots in the lower gastrointestinal tract.National Natural Science Foundation of ChinaSichuan Science and Technology Progra

Soft Robot-Assisted Minimally Invasive Surgery and Interventions: Advances and Outlook

Since the emergence of soft robotics around two decades ago, research interest in the field has escalated at a pace. It is fuelled by the industry's appreciation of the wide range of soft materials available that can be used to create highly dexterous robots with adaptability characteristics far beyond that which can be achieved with rigid component devices. The ability, inherent in soft robots, to compliantly adapt to the environment, has significantly sparked interest from the surgical robotics community. This article provides an in-depth overview of recent progress and outlines the remaining challenges in the development of soft robotics for minimally invasive surgery

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

MODELLING GASTROINTESTINAL SMOOTH MUSCLE MECHANICS

Ph.DDOCTOR OF PHILOSOPH

Development of a dual flow microfluidic device for the study of barrier systems

Inflammatory Bowel Diseases (IBD) including Crohn’s Disease and Ulcerative Colitis are chronic conditions characterised by inflammation of the wall of the gastrointestinal tract. IBD has also been shown to have systemic impacts including on the central nervous system. Traditional models including the animal systems provide only limited information due to a lack of clinical relevance. Microfluidic technology offers a solution, allowing for the creation of human models which better consider the biophysical properties seen within an organ. This study aimed to develop and optimise a dual flow microfluidic device for the study of the gut and blood-brain-barrier (BBB) systems.Devices were designed in-house and consisted of two channels separated by a semi-permeable membrane. A series of iterations of the device were examined for gut-chip studies, with the device refined and optimised to allow a culture of colonic epithelial cells to be maintained for 7 days. Permeability studies and visualisation of ZO-1 expression showed the maintenance of barrier properties during this time. Following optimisation of the gut-chip, the inflammatory effects of bacterial products on epithelial cells were examined. Treatment with bacterial products induced an inflammatory response in the model, however this was lowered in comparison with a static model.Adaption of the device to culture endothelial cells and astrocyte cells in a BBB model was also carried out. Viability tests showed the device could maintain a variety of cell lines for at least 96 h on chip. The gut and BBB-chip were then connected in series, creating a dual model. This platform could maintain a co-culture of epithelial cells within the gut-chip and endothelial cells within a BBB-chip for at least 48 h, showing the potential of the dual flow device to allow for more systemic studies. Preliminary studies were undertaken using a modification of the gut-chip for the maintenance of full thickness gut tissue biopsies for up to 72 h on chip, however morphology of the tissue was not well-preserved.In summary, this study examined the development and optimisation of a dual flow microfluidic device for the study of barrier systems. The final iterations of the device were both robust and reliable and are suitable for investigating a wide variety of physiological and pathological barriers and potentially provide an alternative to existing animal and cellular models

Imaging fascicular organisation in mammalian vagus nerve for selective VNS

Nerves contain a large number of nerve fibres, or axons, organised into bundles known as fascicles. Despite the somatic nervous system being well understood, the organisation of the fascicles within the nerves of the autonomic nervous system remains almost completely unknown. The new field of bioelectronics medicine, Electroceuticals, involves the electrical stimulation of nerves to treat diseases instead of administering drugs or performing complex surgical procedures. Of particular interest is the vagus nerve, a prime target for intervention due to its afferent and efferent innervation to the heart, lungs and majority of the visceral organs. Vagus nerve stimulation (VNS) is a promising therapy for treatment of various conditions resistant to standard therapeutics. However, due to the unknown anatomy, the whole nerve is stimulated which leads to unwanted off-target effects. Electrical Impedance Tomography (EIT) is a non-invasive medical imaging technique in which the impedance of a part of the body is inferred from electrode measurements and used to form a tomographic image of that part. Micro-computed tomography (microCT) is an ex vivo method that has the potential to allow for imaging and tracing of fascicles within experimental models and facilitate the development of a fascicular map. Additionally, it could validate the in vivo technique of EIT. The aim of this thesis was to develop and optimise the microCT imaging method for imaging the fascicles within the nerve and to determine the fascicular organisation of the vagus nerve, ultimately allowing for selective VNS. Understanding and imaging the fascicular anatomy of nerves will not only allow for selective VNS and the improvement of its therapeutic efficacy but could also be integrated into the study on all peripheral nerves for peripheral nerve repair, microsurgery and improving the implementation of nerve guidance conduits. Chapter 1 provides an introduction to vagus nerve anatomy and the principles of microCT, neuronal tracing and EIT. Chapter 2 describes the optimisation of microCT for imaging the fascicular anatomy of peripheral nerves in the experimental rat sciatic and pig vagus nerve models, including the development of pre-processing methods and scanning parameters. Cross-validation of this optimised microCT method, neuronal tracing and EIT in the rat sciatic nerve was detailed in Chapter 3. Chapter 4 describes the study with microCT with tracing, EIT and selective stimulation in pigs, a model for human nerves. The microCT tracing approach was then extended into the subdiaphragmatic branches of the vagus nerves, detailed in Chapter 5. The ultimate goal of human vagus nerve tracing was preliminarily performed and described in Chapter 6. Chapter 7 concludes the work and describes future work. Lastly, Appendix 1 (Chapter 8) is a mini review on the application of selective vagus nerve stimulation to treat acute respiratory distress syndrome and Appendix 2 is morphological data corresponding to Chapter 4

The Development of a Monolithic Shape Memory Alloy Actuator

Shape memory alloys (SMAs) provide exciting opportunities for miniature actuation systems. As SMA actuators are scaled down in size, cooling increases and bandwidth, improves. However, the inclusion of a bias element with which to cycle the SMA actuator becomes difficult at very small scales. One technique used to avoid the necessity of having to include a separate bias element is the use of local annealing to fabricate a monolithic device out of nickel titanium (NiTi). The actuator geometry is machined out of a single piece of non-annealed NiTi. After locally annealing a portion of the complete device, that section exhibits the shape memory effect while the remainder acts as structural support and provides the bias force required for cycling. This work proposes one such locally-annealed monolithic SMA actuator for future incorporation in a device that navigates the digestive tract. After detailing the derivation of lumped electro-mechanical models for the actuator, a description of the prototyping procedure, including fabrication and local annealing of the actuator, is provided. This thesis presents the experimental prototype actuator behaviour and compares it with simulations generated using the developed models