Fetal monitoring is to safeguard the perinatal and fetal safety, achieving an important means of eugenics. Smart fetal monitoring is based on the monitoring indicators of fetal health, auto take corresponding measures of care. Introduces the comes with 24-bit A/D converter core devices MSC1210 microprocessor, wavelet analysis algorithms process the data key for the technical and comparative analysis of the monitoring indicators adopted, using alerts, tips, and start shaking the device mode to alert and auto take corresponding measures of intelligent computer fetal monitor system. Clinical trials show that the system has high detection accuracy, better real-time and accurate, and friendly intelligent control. 1. introduction of perinatal and childbirth on the fetus for guardianship, can detect intrauterine hypoxia, distress and other severe symptoms, reduce fetal mortality, to improve the quality of delivery. Traditional fetal monitoring system is complex, high power consumption, human disturbance, and not for family care and self care. Smart fetal monitoring system using TI company with 24-bit A/D converter and a simulation performance and digital processing power of a microprocessor, the microprocessor MSC1210 input channel select, buffering, amplification, gain adjustment, A/D conversion and digital processing integrated into monolithic circuit, with only one piece of integrated circuits for fetal heart rate, uterine contraction pressure and FM frequency of monitoring indicators of data collection and on voice, sound and vibration control. Intelligent control of fetal monitoring is based on the fetal heart rate, how to accurately and timely received fetal heart rate is the intelligent control of fetal monitoring system. For Fetal Doppler signal to noise ratio with low, non-stationary characteristics of randomness, calculation of the fetal heart rate when 1/2, 2/3 and 2 x heart rate, causing the application to control failures, here combined with the double threshold of wavelet analysis algorithm, accurate, real-time received fetal heart rate, ensuring effective intelligent control. 2. intelligent computer fetal monitor system hardware design 2.1 intelligent computer fetal monitor system structure smart computer fetal monitor system block diagram shown in Figure 1. Mainly by Ultrasonic Doppler fetal heart detector, uterine contraction probe, probe, fetal heart FM signal conditioning circuits (low-pass filtering, absolute value calculations and envelope extract, etc.), uterine contraction pressure signal conditioning circuits, voice control, acoustic, MSC1210 microprocessor and computer processing system. To MSC1210 and computer processing system at its core. MSC1210 control monitoring indicators for the collection and communication, the receiving computer commands control the audio devices and sound vibration. Computer system for intelligent control, communication, control, data processing algorithms, guardianship of the display function modules. 2.2 signal conditioning circuitry for fetal heart rate monitoring indicators of the importance and complexity of Fetal Doppler signal, here focuses on the Fetal Doppler signals coherent circuit. Circuit main on Doppler fetal heart sounds for low-pass filtering, absolute value calculations and envelope extract, pretreatment. Low-pass filter with cutoff frequency for 250Hz second-order low-pass filter to filter out high frequency signals and interference. Absolute arithmetic circuit shown in Figure 2. Signal strength enhanced doubled, increasing the detection sensitivity. Envelope extract circuit shown in Figure 3, using the cut-off frequency is 10HZ P-shaped filtering and t-shaped filtering based on the combination of low-pass filter. Parallel of diodes and capacitors on the circuit of a negative signal for restrictions and on a certain band of high frequency vibration signals. 2.3 MSC1210 microprocessor smart fetal monitor acquisition system uses United States Texas instruments company launched features a strong single-chip microcomputer MSC1210 as processor, MSC1210 chip integrated 8051 microcontroller and FLASH memory of precision touch number converter that chip uses Enhanced 8051 microcontroller core, reducing the instruction execution cycle, use a low-power design, internal integrates a 24-bit resolution analog-digital converter (ADC), the conversion rate of up to 1000HZ, 8-channel multiplexer, analog input channel test current source, the input buffer, programmable gain amplifier (PGA), the internal reference voltage source, 8-bit microcontrollers, Flash memory program/data and data SRAM, etc. Digital filters to filter the output of data. Digital filters with fast, sin2 and sin3 three. Enhanced 8051 kernel has two data pointer, the instruction system and standard 8051 instruction system fully compatible, its execution speed is 3 times faster than the 8051, so you can work in low frequency, to reduce power consumption and noise. In order to reduce interference, its simulation power and digital power supply separately. Because the chip integration enables intelligent fetal monitoring system hardware circuit easier, circuit design more compact, chips are very few external components, making the system's reliability has been greatly improved, but also significantly reduces the development cycle, lower development costs. MSC1210 interface circuit shown in Figure 4. Doppler fetal heart signal and uterine contraction pressure signal IN0 and IN2 input, via multi-channel converter after being fed into the buffer variable gain amplifier to zoom in on an input signal. FM signal by MSC1210 interrupt handling. Receive via RS485 bus MSC1210 PC release of control commands, the P2 port control voice chip complete voice alert function, through the vibration of sound P1.7 control complete automatic wake-up feature of fetus. Adopt more as microprocessor MSC1210 can get accurate, real-time, fetal monitoring indicators for the intelligent control. 3 Smart fetal monitor computer control system for computer control system using Visual C + + 6.0 development environment for programs that run in the context of the Win2000. For systems with large amounts of data and real-time performance requirements, system programming, making full use of the multiple threads of thought. The entire system is set up to five threads, which manages the user interface, responding to user actions in the thread as the main thread, the life cycle for the entire program of main memory, the other four threads for intelligent control, communication, control, data processing algorithms, monitor display function, lifecycle is the thread function itself. Multithreaded application, the thought of various functional modules of the system running in parallel, you can significantly increase the CPU utilization, meet the requirements of the systems real-time. Where data processing algorithms and intelligent control is the control system gatewayKey. 3.1 coif5 wavelet based fetal heart sound data processing algorithms on type description, Discrete Wavelet transform is the signal in the wavelet function on the projection, m, n represents a different resolution (scale) and various time-frequency (Pan), wavelet function is precisely through different m and n to adjust different local time-frequency and different resolutions, namely Wavelet Multiresolution analysis features can signal in different scales for multi-resolution decomposition, and the interweaving of all kinds of different frequency components of mixed signal into different frequency bands of signal, the signal is processed according to the band. Application of wavelet analysis for signal noise reduction is a Wavelet analysis of a very important one for the application. A noisy one dimensional signal model can be expressed as:: s (I) as a true signal; e (I) for noise; x (I) the noise signal. In a real project, useful signal is usually manifested by low frequency signal or a stationary signals, noise is characterized by high-frequency signals, noise cancellation process can be handled by the following methods. First of all on the actual signal for Wavelet Decomposition, choose Wavelet Decomposition level is determined as n, then the noise section typically contains at high frequency. And then on Wavelet Decomposition of high frequency coefficient threshold threshold quantify. Finally according to Wavelet Decomposition coefficient of n-tier low frequency and quantified after 1 to n-tier high frequency coefficient for Wavelet reconstruction, the purpose of eliminating noise, noise suppression of signal, the signal of the actual real signal in recovery. Ultrasound Doppler fetal heart sounds after signal conditioning circuits, signal in the frequency range of 0-500Hz containing less than 4 Hz frequency of fetal heartbeat, so the signal waveform analysis and fetal heart rate calculations should signal low frequency information, instead of high-frequency information; CWT's Multiresolution analysis features as the scale by thicker, gradually to a low frequency signal frequency, from details to smoothing the results of a series. You can use wavelets Multiresolution analysis characteristics, through selected appropriate Wavelet Decomposition level, optimization, separation of high frequency Doppler fetal heart signal and low-frequency components, parts and all the high frequency part, get contains all the information of the fetal, low frequency part through low-frequency signal frequency and calculate the fetal period, the fetal heart rate. This system through a number of experimental and theoretical derivation using Wavelet function. Application of wavelet have orthogonality, approximate symmetry, the better the smoothness and the regularity of advantages through 6 layers of Wavelet Decomposition extraction, get 6 8Hz following layer of low-frequency signal. At this time-frequency signal is basically the baby's heartbeat. Because of the random noise interference, you must extract the wavelet algorithm to the fetal heart sounds, this article uses a dual threshold to identify noise. First calculate the amplitude threshold, the calculation formula is: 3.2 computer fetal monitor smart control for previous fetal monitor only doctors through research monitoring curve graphics to inform fetal health, increased workload, is not conducive to home care. Smart fetal monitoring is focused on fetal monitoring intelligent. The theoretical basis of intelligent monitoring are mainly based on the measured fetal heart rate and clinical experience. Main interface color graphics logos, voice prompts and fetal wake-up control. In order to increase the intelligent control of security and stability, the fetal heart rate monitoring is an average over time, while size can be set via the interface itself. Fetal heart rate was also affected by the State for fetal wake-sleep, fetal acoustic stimulation can awake from sleep go, causing fetal movement, fetal heart rate changes, to learn about prenatal security is significant. Therefore this system is based on the fetal heart rate detection automatically starts the fetal acoustic stimulation of the wake-up, resulting in more valuable fetal monitoring graphs. Table 1 gives the smart fetal monitoring system of the fetal heart rate monitoring and intelligent control of the CRT.
Table 1 fetal monitoring intelligent control measures table
Fetal heart rate (bpm)
Clinical classification
Smart control measures
>180
To spend speed
Red logos, voice prompts
160-180
Mild too quickly
Yellow logo
120-160
Normal heart rate
Green identification
100 ~ 120
Mild slow
Yellow logo
<100
Severe slow
Red logos, voice prompts, start, acoustics and vibration
Adjacent heart rate > 25
Umbilical cord compression
Blue logo, voice prompts
More fetal heart rate is the value of clinical experience, care doctor may, in accordance with the actual situation of pregnant women, you can also set the scene for setting or cancel these intelligent control.
4 conclusions
Intelligent computer fetal monitor system using high-speed sampling MSC1210 microprocessor and communication, combined with a dual threshold coif5 Wavelet extraction of the fetal heart sounds, and joined the intelligent control.
According to the above principles and framework design of intelligent fetal monitoring system with high accuracy, high anti-interference ability of real-time performance, and suitable for home care, reduce the workload and improved perinatal clinical value of fetal monitoring.
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