22-11-2012, 01:34 PM
NEURAL NETWORKS
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Introduction
This paper discusses the recent trends in BIOMEDICAL ENGINEERING. The rapid progress of biomedical instrumentation allows the production of systems and components with a low cost- to- performance ratio.
The paper introduces new trends in sensor technology encompassing the principles of Fuzzy Logic Controllers and Laser Displacement Sensors. It discusses the operating principles, detailed setup and measuring various parameters by different methods. In this paper we will give an overview of the recent advances and new development trends in the field of biomedical instrumentation which includes their applications in:
Fuzzy Logic Control of Inspired Oxygen Concentration in Ventilated Newborn Infants
Introduction to Fuzzy Logic
Wide range of opportunities is open in the field of digitally controlled systems by microcomputer development. Digitally measured information is rapidly processed. Complex systems are easily controlled. The diversity of controlling software allows more creativity to experts. New approach in controlling was introduced, using the fuzzy regulators. The expert, familiar with the certain process, easily can implement the solution, by simply writing and changing the program code. Flexibility in control realization and modifications are easy using software, simply changing the code. New methods of control are introduced. In many different conditions, these prove to be very efficient. A specific application: neural networks and fuzzy logic use on system control.
SYSTEM DESCRIPTION
We chose SaO2 as our measurement parameter and FIO2 as our control parameter for the operational model of maintaining patient oxygenation.
SaO2 Measurement principle
The pulse oximeter measures arterial percent oxygen saturation (SaO2 ) and pulse rate using the principles of spectrophotometry and photoplethysmography.
Light from two light-emitting diodes at two different wavelengths [typically 660 nm (red) and 940 nm (infrared)] passes through the tissue and is sensed by a photodiode. As the heart ejects oxygenated blood into the tissue, the instrument ignores all absorption in the steady-state tissue and measures only the absorption in the tissue that is expanded by the pressure pulse. This expanded volume contains arterial oxygenated blood.
There are two transmitter/sensor geometries. In the transmission mode, the light source and sensor are on opposite sides of the tissue being measured (such as a finger or ear lobe); the light passes through the tissue. In the reflective mode, the sensor and light source are on the same body surface (such as the chest), and the light reflects from the tissue. The finger sensor provided operates as a transmission sensor, where the multisite sensor can be used either way.
SUMMARY
Controlling oxygen exposure in newborn infants is a delicate balance. The infants must receive enough oxygen to ensure adequate tissue oxygenation and to prevent ischemia. Conversely, too much oxygen may produce toxic effects.
The FIO2 fuzzy controller shows promise in the preliminary trials to control patient oxygen saturation levels. It was able to maintain a target SaO2 better than routine manual control, and it reduced the overall oxygen exposure. Further clinical trials will test the actual clinical efficacy of this FIO2 controller, and additional patient data will allow more fine tuning of the fuzzy control parameters (e.g. the shape of the membership functions and the choice of fuzzy regions).
The ease of implementing this fuzzy controller illustrates some of the advantages of this approach. No complex mathematical models were required, the simple rule-based nature of the controller is easy to understand and modify, expert knowledge about the problem is utilized, and the controller was easily designed for non-linear system responses.
Conclusion
With each new technology released, the automation systems gain more capability and efficiency. Automation inherently changes with technology because it applies the latest advances in different fields to gain industrial efficiencies in the user’s respective industry. In the new and different business environment of the 21st century, the companies that can adapt, innovate and utilize the latest in automation will generate significant growth and success.