Mohd Yazed Ahmad

Application of Wireless Power Transmission Systems in Wireless Capsule Endoscopy: An Overview

Wireless capsule endoscopy (WCE) is a promising technology for direct diagnosis of the entire small bowel to detect lethal diseases, including cancer and obscure gastrointestinal bleeding (OGIB). To improve the quality of diagnosis, some vital specifications of WCE such as image resolution, frame rate and working time need to be improved. Additionally, future multi-functioning robotic capsule endoscopy (RCE) units may utilize advanced features such as active system control over capsule motion, drug delivery systems, semi-surgical tools and biopsy. However, the inclusion of the above advanced features demands additional power that make conventional power source methods impractical. In this regards, wireless power transmission (WPT) system has received attention among researchers to overcome this problem. Systematic reviews on techniques of using WPT for WCE are limited, especially when involving the recent technological advancements. This paper aims to fill that gap by providing a systematic review with emphasis on the aspects related to the amount of transmitted power, the power transmission efficiency, the system stability and patient safety. It is noted that, thus far the development of WPT system for this WCE application is still in initial stage and there is room for improvements, especially involving system efficiency, stability, and the patient safety aspects.

RFID reader localization using passive RFID tags

This paper describes an indoor wireless localization method of an RFID reader using passive tags placed at known locations. The reader location is estimated using the received signal strength indication (RSSI) and trilateration. However, in an indoor wireless environment, the RSSI undergoes fading due the presence of unavoidable scatterers. Hence, trilateration under such fading environments would cause errors in localization. In this paper, we examine techniques to reduce the error of the estimated reader positions.

A wireless power transmission system for robotic capsule endoscopy: Design and optimization

This paper presents an inductive coupled wireless power transmission (WPT) system for powering an endoscopic robotic capsule. The proposed WPT system was designed and optimized through manipulation of the core material, the quality factor (Q) and the load impedance matching of the receiving coil (RC). A MnZn ferrite core with high initial permeability was employed. The Q of the 3D RC was optimized by choosing an optimum number of strands and turns. At the optimum design condition the system was able to deliver at least 376 mW of usable power to the load when magnetic field (H-field) of 105 A/m was applied at the frequency of 250 kHz. The uniformity of H-field generated by the power transmitting coil (PTC) was sufficient to achieve 86% stability of received power. The proposed system reduces the required level of H-field by 50% and increases the load power by 22.3% as compared to the existing study.

Stable and High-Efficiency Wireless Power Transfer System for Robotic Capsule Using a Modified Helmholtz Coil

Magnetic resonance-based wireless power transfer system offers a promising solution to overcome power limitations typically encountered by capsule endoscopy. Despite of much attention in this area, aspects such as power stability and power transfer efficiency remain suboptimal and therefore investigation for further improvement is still required. This paper presents a method to improve power stability as well as power transfer efficiency for wireless capsule endoscopy. A new power transmission coil capable of producing uniform magnetic field is proposed to improve power stability through uniform field that at the same time minimizes the unnecessary peak electromagnetic exposure. To improve power transfer efficiency, a mixed resonance scheme is employed. Our experimental results show improvement over existing methods where the proposed system attained power stability of 94.62% and power transfer efficiency of 4.9% under worst position of the receiving coil. Furthermore, the proposed transmitting coil provides additional advantage, where it minimized the unnecessary peak electromagnetic exposure by 26% as compared to the conventional Helmholtz coil-based system. We believe the proposed system will open new direction for future wireless capsule endoscopy and can also be useful in other industrial applications.

Phoneme Classification Using the Auditory Neurogram

In order to mimic the capability of human listeners identifying speech in noisy environments, this paper proposes a phoneme classification technique using simulated neural responses from a physiologically based computational model of the auditory periphery instead of using features directly from the acoustic signal. The 2-D neurograms were constructed from the simulated responses of the auditory-nerve fibers to speech phonemes. The features of the neurograms were extracted using the Radon transform and used to train the classification system using a deep neural network classifier. Classification performance was evaluated in quiet and under noisy conditions for different types of phonemes extracted from the TIMIT database. Based on simulation results, the proposed method outperformed most of the traditional acoustic-property-based phoneme classification methods for both in quiet and under noisy conditions. The proposed method could easily be extended to develop an automatic speech recognition system.

Performance evaluation of power transmission coils for powering endoscopic wireless capsules

This paper presents an analysis of H-field generated by a simple solenoid, pair of solenoids, pair of double-layer solenoids, segmented-solenoid, and Helmholtz power transmission coils (PTCs) to power an endoscopic wireless capsule (WC). The H-fields were computed using finite element analysis based on partial differential equations. Three parameters were considered in the analysis: i) the maximum level of H-field (Hmax) to which the patients body would be exposed, ii) the minimum level of H-field (Hmin) effective for power transmission, and iii) uniformity of H-field. We validated our analysis by comparing the computed data with data measured from a fabricated Helmholtz PTC. This analysis disclosed that at the same excitation power, all the PTCs are able to transfer same amount of minimum usable power since they generated almost equal value of Hmin. The level of electromagnetic exposure and power transfer stability across all the PTCs would vary significantly which is mainly due to the different level of Hmax and H-field uniformity. The segmented solenoid PTC would cause the lowest exposure and this PTC can transfer the maximum amount of power. The Helmholtz PTC would be able to transfer the most stable power with a moderate level of exposure.

Localization of Wireless Capsule Endoscope: A Systematic Review

Wireless capsule endoscope (WCE) is a notable invention introduced in the biomedical industry. It involves swallowing a small disposable video capsule that takes photographic images as it passes through the gastrointestinal (GI) tract. WCE allows physicians to visualize and diagnose disorders covering the full length of the GI tract. Although WCE can provide useful images of the internal GI tract, the identification of the exact location of the detected disease remains unclear. Location information is very crucial for the subsequent treatment of the detected disease either through surgery or through local drug delivery. The huge potential of WCE in future endoscopic practice relies on the successful tracking of the wireless capsule. This paper presents a comprehensive systematic review on the recent developments in WCE localization techniques that have been reported in credible sources, namely, IEEE Xplore, PubMed, Scopus, Science Direct, Springer Link, and Google Scholar. Detailed analysis and systematic comparison are provided to highlight the achievement and future direction of WCE localization. This paper can be a valuable source of reference and guidance for future research in this field.

Fabric-Based Sensor for Applications in Biomechanical Pressure Measurement

Wearable pressure sensor is an important element in human gait and biomechanical investigations. Many studies have been carried out to ensure its reliability and comfort to the user even when the sensor has to be operated under extreme conditions such as uneven surface with high curvature area, high humidity environment, and wide range of dynamic pressure. However, the existing pressure sensors that could endure such extreme conditions usually involve complex fabrication processes and often incur high cost of materials. Therefore, in this paper we present a novel pressure sensor made of low cost fabric materials with simple fabrication process. The sensor is constructed from a conductive fabric using piezoresistive technique. A unit area of our pressure sensor is made of a thin layer of piezoresistive material and it is placed in between two layers of conductive fabrics. To vary sensing sensitivity and to cater wide range of pressure, our proposed sensor uses special mesh layers which are placed in between the piezoresistive layer and the conductive layers. This way, wide range of dynamic pressure can be captured. To test the proposed sensor, five units of pressure sensors have been designed with variety of mesh layering techniques. These sensors are tested using 0- 3 kg load and the data are analyzed graphically. Our experimental results on the resistive versus pressure response show a similar trend as compared with the existing popular pressure sensor such as flexiforce in term of force versus resistance curve. The use of mesh layer allows measurement of higher magnitude of pressure. Since the performance of our sensor can be tailored to exhibits the performance of the exiting commercial sensors therefore the proposed technique can be an alternative affordable solution to that of the existing expensive sensors.

Smart antenna system design for localization of wireless capsule

Smart antenna is recognized as an intelligent antenna system in modern wireless communication for its adaptive beam forming technique and direction of arrival (DoA) estimation features. However, this system is yet to be introduced extensively for biomedical applications. A sectoral sweeper based algorithm is proposed in this article for RF localization of wireless capsule inside the human gastro intestinal (GI) tract. This algorithm basically works using the alteration of task beam power level and direction of smart antenna array. It is proposed that, one transmitting antenna element of antenna array transmits signals towards the GI tract at a time and others will be in receive mode. The received signals are then processed based on space-frequency signal processing concept which is derived in this paper for cylindrical shaped antenna array. Particle swarm optimization model is developed to predict the 2D location of robotic capsule from the received information of smart antenna system with about 99% successful.

Multi-channel Fabric Based Pressure Mapping Data Acquisition System

A smart fabric based multichannel pressure mapping Data Acquisition System (DAS) was specially designed to read and visualize real time pressure data from an array of piezoresistive fabric pressure sensor. This DAS is important to enable rapid monitoring of pressure distribution for biomedical engineering applications. A customized pressure mapping circuit using off-the-shelf components has been designed and fabricated. In addition, a pressure mapping algorithm which runs on Arduino platform and MATLAB was developed to continuously read and visualize pressure profile from the fabric pressure sensor. To ensure low component count and simple hardware, the concept of multiplexing has been employed in the hardware architecture and the firmware was written to support this architecture. This approach allows the system to perform even with single processor and single ADC. The reliability of the system was tested with array of fabric pressure sensor using a special portable load cell (Advance Force Gauge by MECMESIN). Pressure profile for each sensor unit matches the sensor resistive load characteristic, repeatability and accuracy of a commercial data acquisition system. The system is suitable for reading slow changing analog signal. If one desired to measure fast changing signal, the same architecture can still be used but specifications of the components must be higher. In conclusion, a smart multichannel pressure mapping Data Acquisition System (DAS) was designed, fabricated and tested. The unit capable of acquiring and visualizing pressure data from the developed sensor array. The speed of the system can be increased by using higher speed components while maintaining the same architecture.