Don Isarakorn

Application of coefficient diagram method for rotational inverted pendulum control

In this paper, a design of the augmented state feedback controller by using the concept of coefficient diagram method (CDM) for a servo type of the rotational inverted pendulum system is presented. An integrator is augmented to the system due to the responses exhibiting steady-state error. In order to apply the CDM method, the augmented system must be firstly linearized and converted into controllable canonical form by a transform matrix. Then a feedback gain matrix in sense of CDM can be obtained. One can observe that the design procedure of the proposed controller is easy compared to other methods. The experimental results are shown in order to verify the effectiveness of the controller.

Feature extraction from retinal fundus image for early detection of diabetic retinopathy

Automated detection of lesions in retinal fundus image can be aid in the detection of diabetic retinopathy. Exudates are the early sign of diabetic retinopathy so the proper detection of these lesions is an essential task in an automatic retinal screening. On the research work leading to automatic analysis of exudate detection, the knowledge of Optic Disk (OD) location is very useful. An efficient algorithm is presented to detect the OD and exudate which are the most important features for early detection of diabetic retinopathy. From a retinal fundus image, the proposed method first preprocesses and estimates the histogram of retinal background, then filters out the bright pixels in intensity image. They include OD, and non-OD (exudates and noise). Next, an OD boundary is determined and eliminated after applying blob boundary measurement and morphological reconstruction. Finally, exudates are extracted by applying the maximum entropy thresholding to filter out the bright pixels from the green component of retinal image which OD region inside is eliminated. The proposed technique has been tested first on 100 images from hospital. Experimental results show that 93% and 89% of OD and exudate were detected correctly, respectively.

Harvesting Energy From a Rotating Gear Using an AFM-Like MEMS Piezoelectric Frequency Up-Converting Energy Harvester

This paper presents an analytical and experimental study of a compact configuration to harvest energy from a rotating gear using piezoelectric microelectromechanical system harvesters. The reported configuration realizes a contact-type frequency up-conversion mechanism in order to generate useful electrical energy. The up-conversion mechanism was achieved using an atomic force microscope (AFM)-like piezoelectric cantilever plucked by the teeth of the rotating gear that could be eventually driven by an oscillating mass. This paper describes relevant design guidelines for harvesting energy from the low-frequency mechanical movement of a rotating gear through analytical modeling and finite element method (FEM) simulation followed by experimental validation. Different harvester configurations are investigated to identify the optimal configuration in terms of the output energy and energy conversion efficiency. The latter results are reported for the first time because of the implementation of an original concept based on the coupling of the harvester with a rotational flywheel. The experimental results reveal that free vibrations of the harvester after plucking contribute significantly to the output energy and efficiency. By adding a proof mass, the efficiency of the system can be greatly improved. For plucking speeds between 3 and 19 r/s, average output powers in the order of tens of microwatts were obtained for continuous plucking. By combining interaction energy, friction, and energy absorption, between the harvester and inertial mass, the maximum efficiency of the impact piezoelectric harvesters was found to be 1.4%. The efficiency results obtained were compared with the noncontact magnetic plucking approach further demonstrating the potential of our concept. Finally, different tip-gear materials combinations were evaluated showing the importance of their nature on the reliability of the presented configuration.

Automatic exudate extraction for early detection of Diabetic Retinopathy

Diabetic Retinopathy (DR) is the most common cause of blindness in diabetic patients, but early detection and timely treatment can prevent this problem. Exudates have been found to be one of the signs and serious DR anomalies so the proper detection of these lesions and the treatment should be done immediately to prevent loss of vision. The aim of this study is to automatically detect these lesions in fundus images. To achieve this goal, the proposed method first preprocesses to improve the quality of fundus image, and then Optic Disc (OD) is detected and eliminated to prevent the interference to the result of exudate detection by combination of 3 methods; image binarization, Region Of Interest (ROI) based segmentation and Morphological Reconstruction (MR). Next, exudates are detected by applying the maximum entropy thresholding to filter out the bright pixels from the result of OD region eliminated. Since the result contains some noises which appear as bright light at the edge of fundus area in some images, that affect is considered and eliminated to improve the result of false positive. Finally, exudates are extracted by using MR. The proposed technique has been tested on 100 fundus images from hospital. Experimental results show that 91 % of exudate is extracted correctly with the average process of 3.92 second per image.

Epitaxial Piezoelectric Pb(Zr0.2Ti0.8)O3 Thin Films on Silicon for Energy Harvesting Devices

We report on the properties of ferroelectric Pb(Zr0.2Ti0.8)O3 (PZT) thin films grown epitaxially on (001) silicon and on the performance of such heterostructures for microfabricated piezoelectric energy harvesters. In the first part of the paper, we investigate the epitaxial stacks through transmission electron microscopy and piezoelectric force microscopy studies to characterize in detail their crystalline structure. In the second part of the paper, we present the electrical characteristics of piezoelectric cantilevers based on these epitaxial PZT films. The performance of such cantilevers as vibration energy transducers is compared with other piezoelectric harvesters and indicates the potential of the epitaxial approach in the field of energy harvesting devices.

Automatic microaneurysms detection through retinal color image analysis

This paper proposes an automatic system to diagnose the diabetic retinopathy symptom, which can cause a loss of vision by analysis the abnormality in retinal image. Digital image processing system is developed for the retinal image analysis which helps ophthalmologists to identify diabetic patients. The retinal images derived from ophthalmologists are used to analysis by using HSV, area identification and eccentricity techniques to distinguish diabetic retinopathy symptoms from normal diabetic patients. First color bar is evaluated by using HSV method and then using the eccentricity technique with area of pixel to find out the abnormality of Microaneurysms (MAs). The accuracy result of experiment is around 93% when compares to the analysis of ophthalmologists.

Energy Analysis in Zigbee Based Wireless Sensor Node Powered by Piezoelectric Energy Harvester

Recently, an integration of wireless sensor network with energy harvesters is getting more interested because it can extend the life time of battery in a sensor node, which is very important in many applications. This paper presents the concept of energy analysis in Zigbee based wireless sensor network, which is powered by a piezoelectric energy harvester to optimize the algorithms used in wireless sensor network. In this work, difference aspects related to piezoelectric energy harvester, characteristic of power consumption in Zigbee based wireless sensor node and concept of optimizing algorithms to balance input and output power in the integrated system are proposed. Keywords: energy harvesting, piezoelectric transducer, Zigbee based wireless sensor network

Phase-locked loop process control system using LQR approach

This paper presents the phase-locked loop (PLL) process control system designed by using the approach of linear quadratic regulator (LQR). By considering the loop filter (LF) of phase-locked loop is a part of the process to be controlled, an augmented system can be constructed when voltage control oscillators (VCO) is considered as an added integrator. The integral gain of the proposed augmented system obtained by LQR can be used as an optimal value to design the parameter of LF under the known value of natural frequency of the PLL. The experimental results in controlling the second-order lag pressure process using the proposed PLL show that the system response is fast without overshoot and steady-state error, the output disturbance effect can be rejected, the property of tracking can be obtained and the system can be controlled when process parameter is changed.

A comparative study based on classical and newer piezoelectric materials based unimorph actuators for Hard Disk Drive

The piezoelectric actuator technology for moving the read-write head of Hard Disk Drive (HDD) is very important and widely used. Advanced high-performance technologies for the actuator and servo control are required in order to achieve not only accurate positioning control on data tracks but also high-speed access onto another data track. There is strong demand for hard disk drives with high-speed access performance, which generally requires actuators with a wider servo bandwidth. This paper focuses on the comparative piezoelectric materials based unimorph actuators with classical piezo (Poly crystalline PZT) and newer piezo (Single-crystalline PMN-PT) ceramics. The advantages of piezoelectric materials in terms of mechanical and electrical characteristics aiming at a useful compromise performance displacement and resonant frequency are studied and analyzed.

Automatic hemorrhages detection based on fundus images

This paper proposes methods to detect hemorrhages which are known as a kind of lesions in diabetic retinopathy. To detect the symptom, eye fundus structures (blood vessels and fovea) as well as microaneuysms need to be discriminated to filter out only the hemorrhages. Five processing steps are proposed based analysis on fundus images. First, preprocessing step is processed to improve the quality of the image. Then all red features are filtered out. They include blood vessels, fovea, microaneurysms and hemorrhages. After that, morphology operation and compactness measurement are applied to eliminate the fovea, and blood vessels. Finally, hemorrhages can be classified by using area method to remove microaneurysms and some small noise. 579 fundus images from Bhumibol Adulyadej Hospital were tested. The results were analysis by ophthalmologist in order to define system accuracy and preciseness. According to results of comparison, we found that the accuracy is 90 % and the average of processing time is 6.23 seconds per image.