安徽工程大学机电学院毕业设计（论文）
参考文献
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附录A 系统原理图
戴诗川：液体点滴速度监控系统设计
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安徽工程大学机电学院毕业设计（论文）
附录B 引用外文文献及其译文
Medical drop speed monitoring system design
Based on an eccentric wheel
Abstract
According to measurement and control requirement of a medical drop speed, a control and monitoring system based on an eccentric wheel is presented for the liquid dropping speed and its application is realized to control drip rate of liquid dropping in this paper. L298N integrated chip is used to control the stepper motor, so that the medical drop speed monitoring system is reliable. For the control system, it contains some advantages, such as small size, simple operation, cost-effective etc.
Keywords: Medical drop speed；Eccentric wheel；Remote control,；Monitoring system
I. INTRODUCTION
The national development and Reform Commission disclosed that China used infusion with 10.4 billion bottles in 2009, which was a comparatively large number drawn the strong concern. At present, the venous infusion apparatus used in the hospital are suspended above the patient’s infusion, using the potential difference between the liquid input into the patient's body, through the hose clamp on the hose caliber of compression and relaxation to control the drop speed, the infusion speed is hard to accurately limit. This approach is very inconvenient to patients and the medical staff .If using the medical drop speed monitor device, will be certainly welcomed by the medical staff and patients. Therefore, researching the medical drop speed monitor is very meaningful.
Over the past decade, many researchers have considered heavily in improving the quality of medical drop speed control systems. Many methods have been obtained. For example, taking the monolithic integrated circuit of 89C51 as a core, such units were designed as the master control unit, keyboard input system, drop speed detection, drop speed control, digital display, acousto-optics alarm circuit and electromotor drive. All circuit module units were connected in monolithic integrated circuit. The gathering data were transferred to monolithic integrated circuit in the form of electrical signals. After the operation, analysis and processing, monolithic integrated circuit transferred the data to demonstration module, electrical machinery and acousto-optics alarm circuit through the outlet.
In this paper, our objective is to develop a portable medical drop speed monitoring equipment which can conveniently control the drop speed in infusion Such that, L298N integrated chip is used to control the stepper motor, so that the medical drop speed monitoring system is reliable. For the control system, it contains some advantages, such as small size, simple operation, cost-effective etc.
II. THE MEDICA DROP SPEED MONITORING SYSTEM
The medical drop speed monitoring system is a way to monitor the liquid dropping speed device. Consists of two parts of the software and hardware constitutes the medical drop speed monitor device. The hardware part is mainly composed of a liquid drop speed test device, water speed control device, man-machine exchange device, a PC system, the 485 network system, the remote control transmitter, a remote control receiver and alarm and other parts,
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戴诗川：液体点滴速度监控系统设计
which is shown in Figure 1. The overall structure of the medical drop speed monitor system based on the eccentric wheel is shown in Figure 2.
The eccentric wheel is also called the eccentric connection matrix, we thought the outer diameter of the wheel is a regular circle, but only relative to operation center bias state to connect the mother called the eccentric wheel. The eccentric wheel has two structural forms, one is fixed axis, and another is active axis, the so-called eccentric, as the name suggests that his heart is not in the middle of the encircle. When the axis rotates, the eccentric wheel is driven to rotate together, which is generally the cam mechanism, the dimensional accuracy and surface roughness requirements are higher.
Using the wire cutting technology to produce a card slot and an eccentric wheel, the eccentric wheel can be put into the card slot. The liquid flow tube clip into between the card slot and the eccentric wheel, the eccentric wheel rotate by the motor control, the motor selects four-beat stepping motor. When the motor rotates, the eccentric wheel is driven to rotate. The distance changes between the card slot and the eccentric wheel, so that control the liquid flow tube cross-sectional area changing. When the cross-sectional area of the liquid flow tube is changed, the change of the flow can be achieved such that the purpose of controlling the drop change can be satisfied. Assuming that each bottle droplet of volume V flows through the hose for the time t, the hose cross-sectional area is S, then we have:
V=S*t (1)
Figure 1 Medical drop speed monitor system
Assuming that each drop volume for V0, the bit number through hose cross-sectional area per minute for n, then Y=n*V0*t. Substitution of (1), then we have:
S=V0*n (2)
Usually, the volume of each drop for V0 is constant, so, the bit number N per minute through the hose cross-sectional area is directly proportional to the hose section area s.
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安徽工程大学机电学院毕业设计（论文）
Figure 2 Structure of medical drop speed monitor system
III. LIQUID DROPPING SPEED CONTROL CIRCUIT
To control of liquid dropping speed, what can use eccentric wheel control the area of infusion hose to control liquid dropping speed. This method is small volume, easy operation, data processing complicated. It can also be used to adjust to control the speed of drop. This method is big volume, but the data processing is simple. Using stepping motor to control the eccentric wheel, which makes use of eccentric wheel control infusion hose area to control dropping speed, this method have fine results. Stepper motor is the electric pulse signal into angular displacement or linear displacement of the open-loop control components. Under the non-overloading condition, motor speed, stop only depends on the pulse signal frequency and pulse number, but is not affected by the change of overload, When stepping drive to receive a pulse, it drives stepper motor rotate in the direction set by a fixed point of view, it is the rotation of the fixed point of the operation step by step. Though the number of pulses controlling to control the amount of angular displacement, which in order to achieve the purposes of accurate position.
More common stepper motor including reactive stepping motor, permanent magnet stepper motors, hybrid stepper motor and so on. Hybrid stepper combines the advantages of the reactive stepping motor and permanent magnet stepper motors. Its step angle is small, high power, fine function, which is the highest performance stepper motor by far. It consists of two-phase and five phase: generally two-phase step angle of 1.8 degrees while the five-phase stepper angle of 0.72degrees.
35H2P2803A4 hybrid stepper motor is selected as the stepper motor for its small size, small step angle, and high power, good performance, shown in Table 1. We choose to use 35H2P2803A4 stepper motor to control hose of sectional area.
Make the stepper motor's output enough torque to drive the load, we must add the
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