In this chapter, review of work carried out is presented in the form of

Transcription

1 LITERATURE REVIEW

2 2.1 Introduction In this chapter, review of work carried out is presented in the form of literature survey. This chapter also covers the comprehensive general and specific literature survey on VHDL, FPGA based designs for measurement of temperature frequency, voltage and sensors. Many studies have been carried out by Researchers and Scientists ip India and Abroad to understand and describe the FPGA based design. By going through the literature, the topic of the present study has been identified. 2.2 Literature Review Deming Chen et al. [1] describe the role of design automation or computer-aided design (CAD) for field programmable gate arrays (FPGAs) in the rapid advancement and adoption of FPGA technology over the past two decades. The purpose of this work is to meet the demand for an up-to-date comprehensive survey/tutorial for FPGA design automation, with an emphasis on the recent developments within the past 5-10 years. The paper focuses on the theory and techniques that have been, or most likely will be, reduced to practice. It covers all major steps in FPGA design flow which includes: routing and placement, circuit clustering, technology mapping and architecture-specific optimization, physical synthesis, RT-level and behaviorlevel synthesis, and power optimization. This paper can be used both as a guide for beginners who are embarking on research in this relatively young yet exciting area, and a useful reference for established researchers in this field. 20

3 Jie Qin et al [2] have presented FPGA-based built in self-test (BIST) approach that is used for adaptive control in mixed-signal systems. It provides the capability to perform accurate analog functional measurements of critical parameters such as the third-order intercept point, frequency amplitude and phase responses, and noise figure. The results of these measurements can then be used to adaptively control the analog circuitry for calibration and compensation. The BIST circuitry consists of a direct digital synthesizer-based test pattern generator and a multiplier/accumulator-based output response analyzer; The BIST approach has been implemented in an FPGA-based mixed-signal system and used for actual analog functional measurements. The BIST measurements agree quite well with the results obtained with the traditional analog test equipment. The proposed BIST circuitry provides a unique means for high-performance adaptive control in mixed-signal systems. Daniel Hadji and Valentin S. MollOv [3] describe that temperature is among the most frequently measured analog parameters. This might be expected since most electrical, chemical, mechanical, and environmental systems are strongly affected by the temperature directly or use its value to control other relevant processes. Intuitively, temperature is a measure of how hot or cold something is, although the most immediate way in which we can measure this, by feeling it, is. unreliable, resulting in the phenomenon of felt air temperature, which can differ at varying degrees from actual temperature. Here they present a prototyped design of an engineering system for precise measurement of temperature based on Xilinx Spartan 3E developing kit. 21

4 Savita Sonali and K. Nagabhushan Raju [4] describe the implementation of software module using VHDL for Xilinx FPGA (XC3S400) based PID controller for DC motor speed control system. The tools used for building and testing the software modules are Xilinx ISE 9.2i and ModelSim XE III 6.3c. Before verifying the design on FPGA the complete design is simulated using Modelsim Simulation tool. A test bench is written where the set speed can be changed for the motor. It is observed that the motor speed gradually changes to the set speed and locks to the set speed. S. Velusamy et al. [5] have presented the design of a system that monitors the temperatures at various locations on the FPGA. This system is composed of a controller interfacing to an array of temperature sensors that are implemented on the FPGA fabric. Such a system can be used to implement dynamic thermal management techniques. They cross validate the sensor readings with values obtained from HotSpot, a pre-rtl architectural level thermal modeling tool. Growth in floating-point applications for FPGAs has made it critical to optimize floating-point units for FPGA technology. The divider is of particular interest because the design space is large and divider usage in applications varies widely. Obtaining the right balance between clock speed, latency, throughput, and area in FPGAs can be challenging. The studies of K.S. Hemmert and K.D. Underwood [6] include range of performance, throughput, and area constraints. On a Xilinx Virtex4-ll FPGA, the range includes 250-MHz IEEE compliant double precision divides that are fully pipelined to 187-MHz iterative cores. Similarly, area requirements range from 4100 slices down to a mere 334 slices. 22

5 Color space conversion is very important in many types of image processing applications including video compression. This operation consumes up to 40% of the entire processing power of a highly optimised decoder. Therefore, techniques which efficiently implement this conversion are desired. F. Bensaali and A. Amira [7] describe four different scalable architectures for efficient implementation of two such color space converters using an FPGA based system. Distributed arithmetic technique and systolic design have been exploited to implement the proposed structures on the Celoxica RC1000-PP FPGA development board. The implementation approaches exhibit better performances when compared with existing implementations. Sharief F. Baiker, Liena Elrayah Abdel-Khair, Samah M. Elbasheer, describes the design and development of a microcontroller based heart rate monitor using fingertip sensor [8]. The device uses the optical technology to detect the flow of blood through the finger and offers the advantage of portability over tape based recording systems. Discrete Fourier Transforms to analyse the ECG signal in order to measure the heart rate. The performance of HRM device was compared with the ECG signal represented on an oscilloscope and manual pulse measurement of heart beat. After going through the literature, it has been decided to design and develop FPGA based Heart Beat Measurement System. 23

6 . 2.3 Introduction to Heart beat measurement Heart rate measurement is one of the very important parameters of the human cardiovascular system. Although there are many subjective clues as to how our body is doing during exercise - such as perceived exertion, breathing rate, and physical sensations - none is as reliable as measuring heart rate. Being an accurate measure for workout intensity, recovery level and long-term progress, heart rate is a window to your own fitness. Each person reacts to physical strain individually, depending on the size of the heart, fitness level, skills, and daily changes of stress level. This can be seen in heart rate variability, which measures the variations in the time between successive heart beats. Unlike common misconception, heart does not beat as regular as clockwork. On the contrary, the healthier the heart, the better it adapts to different situations and changing circumstances. Polar training computers can detect these slight changes in heart rate variability by measuring beat-to-beat intervals in milliseconds. Heart monitors are some of the most popular purchases, especially for those who are athletes. It doesn t matter why we need a heart monitor, to find that there are many great brands to choose from. Each brand offers its own unique devices. Each device has its own features and capabilities A heart rate monitor is a personal monitoring device which allows measuring his or her heart rate in real time or recording his or her heart rate. Early models consisted of a monitoring box with a set of electrodes leads which attached to the chest. As the electronics components are more complex now, new functionality and flexibility on hardware and software are required other than time measurement, 24

7 waveform display update rate and visualization. Although many heartbeat monitors are already available in the market, there are still room for improvement on techniques of acquiring the analogue signal waveform and pre-processing of digitized data in FPGA chip. 2.4 Overview of heart Rate and Measurement methodology What Is heart rate? Heart rate is the number of heart beats per unit of time, typically expressed as beats per minute (bpm).heart rate can vary as the body s need to absorb oxygen and excrete C02 changes, such as during exercise or sleep [9]. The measurement of heart rate is used by medical professionals to assist in the diagnosis and tracking of medical conditions. It is also used by individual, such as athletes, who are interested in monitoring their heart rate to gain maximum efficiency from their training Measurement of heart rate system Heart rate can be measured either by manual or monitor method. Manual method Carotid Pulse (neck): To take the heart rate at the neck, place the first two fingers on either side of the neck. Be careful not to press to hard, and then count the number of beats for a minute [10]. Radial Pulse (wrist): Place the index and middle fingers together on the opposite wrist, about la inches on the inside of the joint, in line with die 25

8 index finger. Once find a pulse, count the number of beats feel for a minute. To estimate the beat per minute by counting over 10 seconds and multiplying this by 6 or count over 15 seconds and multiply by 4, or over 30 seconds and doubling the result. There are obvious potential errors by using this shorthand method. Hence the heart rate monitor gives an accurate reading. Fig2.1 and 2.2 shows measuring the heart rate using manual method. Fig.2.1 Carotid pulse Fig-2.2 Radial pulse Monitor Method A heart rate monitor or ECG/EEG can be used to get a more accurate heart rate measurement (Fig 2.3). This is particularly important during exercise where the motion of exercise often makes it hard to get a clear measurement using the manual method. 26

9 Using a heart rate monitor is also useful to record heart rate changes over short time periods, where the heart rate may be changing. Many heart rate monitors are able to record the heart rate values to be reviewed later or download to a computer. Fig.2.3 Wrist method 2.5 Block diagram of Heart rate measurement system Heart rate monitors usually consist of a transmitter unit strapped to the chest, wrist or other body part and receiver unit. The transmitter records the heart rate and transmits it via radio frequency to the receiver, which features a numerical display to indicate the heart rate [11]. Heart rate monitors work by detecting heart beats using electrodes, electrical signals or infrared waves. When the monitor detects a heartbeat, it sends to the transmitter, which converts it into an electrical signal and sends it to the receiver. The receiver records the heart beats and the intervals between each one to determine 27

10 the person s average heart rate, which it reads out on a liquid crystal display (LCD).Fig2.4 shows the typical block diagram of heart rate measurement. Fig.2.4 Typical block diagram of Heart Beat measurement system Sensor-A LED and photo-sensor used to measure the pulse by measuring the change in blood flow through one of the index fingers. Filter-A noise filter designed to filter out any unwanted noise and interference from ambient light. FPGA-Field Programmable Gate Arrays (FPGAs) are programmable semiconductor devices that are based around a matrix of configurable logic blocks (CLBs) connected via programmable interconnect. LCD: The FPGA controls the LCD by means of the 8-bit data interface. Its main function is to store, the selected character code and display on the LCD screen. 2.6 Types of heart rate measurement devices 1. Infrared Infrared heart monitors use small infrared sensors lodged into the monitor, usually with a small window cut out to allow infrared beam to pass through. Most models are handled, with the sensor usually clipped onto a finger or earlobe. Earlobe monitors are the best used when exercising, because their reading are not 28

11 affected by the user s movement. However, finger monitors are more effective in dim or poorly lit rooms, because infrared detections can fluctuate in irregular light conditions. 2. Hand Hand heart arte monitors work by detecting the natural electrical signal that triggers the heartbeat. They usually detect these signals from the hands or fingers, where the signal is strong and easy to detect. Most models use two metal sensors, which are touched or grasped with the hand or finger. 3. Chest Chest monitors work much the same way as hand monitors, except that the sensor is strapped to the user s chest. A set of electrodes is built-in the belt and positioned just below the bust line, where the signal is stronger. The electrode belt features a built-in or attached transmitter, which sends the data to the readout unit upon detection. This eliminates the delay present in hand monitors. They are most preferred type of monitor because of their reliability and accuracy to others system. They are also more convenient, as they do not depend on physical movements and can be used with all forms of exercise. However they are prone to interference from nearby transmitting devices such as televisions and computers. 29

12 REFERENCES 1. Deming Chen, Jason Cong and Peichen Pan, FPGA Design Automation: A Survey, Foundations and trends in Electronic Design Automation, 1(3), 2006, Jie Qin, Charles E. Stroud and Fa Foster Dai, FPGA-Based Analog functional Measurements for Adaptive Control in Mixed-Signal Systems, IEEE Transactions on Industrial Electronics, 54(4), 2007, Daniel Hadji and Valentin S. Mollov, Precise Temperature Measurement and Data Processing with Xilinx Spartan-3E Starter Kit, International Scientific Conference Computer Science, 2008, Savita SONOLI and K. Nagabhushan Raju, Implementation of FPGA based PID Controller for DC Motor Speed Control System, Sensors & Transducers Journal, 114 (3), 2010, S.Velusamy, Wei Huang, J. Lach, M. Stan and K. Skadron, Monitoring temperature in FPGA based SoCs, IEEE International Conference on Computer Design: VLSI in Computers and Processors, 2005, K. Scott Hemmert and Keith D. Underwood, Floating-point divider designs for FPGAs, IEEE Transactions on Very Large Scale Integration (VLSI) Systems, 15(1), 2007, F. Bensaali and A. Amira, Design and Implementation of Efficient Architectures for Color Space Conversion, ICGST-GVIP Journal, 1(5), 2004, Sharief F. Baiker, Liena Elrayah Abdel-Khair, Samah M. Elbasheer, Microcontroller Based Heart Rate Monitor using Fingertip Sensors, Dept, of 30

13 Electrical and Electronic Engineering, Faculty of Engineering,University of Khartoum, Sudan. UofKEJ Vol. 1 Issue 2 pp.47-51, October Overview of Heart-rate measuring device Overview of pulse measurement. http.7/ hw233473_aa25322,00.html. 11. Overview of heartbeat sensors. 31