“This article mainly describes the design of the intelligent system of the medical microwave therapy instrument. The composition principle and function of the microwave therapeutic apparatus are briefly introduced, and the software and hardware design content of the intelligent automatic control system of the microwave therapeutic apparatus are described in detail. At the same time, some components of the microwave therapeutic apparatus are introduced correspondingly. The intelligent control of the microwave treatment instrument through PID adjustment and segmented fitting makes the operation of the microwave treatment instrument more stable and reliable than the situation without this control scheme. The test results also show that the design is feasible.At the same time, the host computer software has been developed to provide a platform for the statistical analysis of follow-up visits and treatment effects.
This article mainly describes the design of the intelligent system of the medical microwave therapy instrument. The composition principle and function of the microwave therapeutic apparatus are briefly introduced, and the software and hardware design content of the intelligent automatic control system of the microwave therapeutic apparatus are described in detail. At the same time, some components of the microwave therapeutic apparatus are introduced correspondingly. The intelligent control of the microwave treatment instrument through PID adjustment and segmented fitting makes the operation of the microwave treatment instrument more stable and reliable than the situation without this control scheme. The test results also show that the design is feasible. At the same time, the host computer software was developed to provide a platform for follow-up visits and statistical analysis of treatment effects.
Microwave therapy is a new clinical treatment method. Its equipment is simple, the treatment effect is obvious, the use is safe, the complications are few, and the tissue damage is small, so it has been affirmed by the medical profession. The microwave therapeutic apparatus uses the heat generated by the microwave in the human body to radiate the diseased part of the patient, so as to achieve the purpose of treatment. In view of its remarkable therapeutic effect, it is an ideal medical equipment for the development of damage-free treatment today. At present, most hospitals use imported microwave therapy devices, which generally have disadvantages such as large size, high price, and complicated operation. However, the technology of domestically produced microwave therapy devices needs to be updated and the output power stability is not good, resulting in insignificant therapeutic effects. , Lack of some necessary protective measures, which makes the security of the entire system not very good, the degree of intelligence is not ideal, and it is inconvenient to use and operate. Therefore, it is necessary to redesign it, especially in terms of safety and control systems, to use new design methods to achieve the best results.
The intelligent microwave therapy device designed in this article has the following characteristics: (1) The control system uses overload protection on the hardware, and the software uses PID control plus segmented fitting methods, which makes the safety performance and output power of the therapy device better. Fundamental changes; (2) The embedded operating system is adopted in the design of the software, so that the operability, safety and stability of the entire microwave therapy system have reached a new height.
2 Microwave treatment mechanism
Microwaves are ultra-high frequency electromagnetic waves with a frequency of 300 “300000MHz and a wavelength of 1mm” 1m, which are non-ionizing radiation. Microwave technology plays an important role in both medical diagnosis and treatment.
In the process of microwave therapy, according to the different microwave power density used, thermal effect treatment and non-thermal effect treatment are distinguished. At present, the mechanism of thermal effect treatment is relatively clear. The treatment mechanism is: most of the human tissue is composed of polar molecules such as water and protein. Under the action of the microwave electric field torque, the polar molecules move in an orderly arrangement along the direction of the microwave electric field and move with the height. The frequency electric field alternates and rotates back and forth. During the rotation, it produces similar frictional collisions with adjacent molecules to generate heat. Increase the temperature of the body tissue at the irradiated part, expand the blood vessels and capillaries, and achieve the purpose of accelerating the metabolic process, improving local nutrition, and enhancing the ability of tissue repair and regeneration. Different from other hyperthermia methods, the heat source of microwave heating is not conducted from the outside, but generated by the biological tissue itself. This kind of heat has high efficiency and good thermal stability[4-6].
3 System composition and principle block diagram
Using the principle of microwave heating effect treatment, the biological body is placed in the microwave radiation field to complete the treatment process. The instrument is mainly composed of switching high voltage source, magnetron, linear power supply, waveguide, microwave probe, sensor and microcontroller. The pulse-width modulation switching high-voltage power supply generates the high voltage required by the magnetron, and stabilizes the output power of the magnetron through the feedback control of the high-voltage DC current, while the linear power supply provides a stable DC voltage to power the filament. The magnetron uses a special medical magnetron, the waveguide (microwave cable) is used to transmit microwaves, and the microwave probe is inserted into the patient’s affected tissue for treatment. The sensor is used to monitor the output power of the magnetron. The microcontroller is used to control the normal operation of the entire system.
Through a full bridge rectifier and a comparator, the sinusoidal alternating current is converted into a series of rectangular waves. At the falling edge of the rectangular wave-the zero crossing point of the sinusoidal alternating current, the system will receive an interrupt request, indicating that the thyristor and relay can be triggered. The appropriate trigger point is controlled by the system to achieve the required power. The power sensor collects the output of the magnetron and is used to monitor the output power value to form a closed-loop control system. At the same time, the output of the sensor is also connected to the hardware protection circuit. If the control system fails and the output is not controlled, the output power may exceed the range required by the instrument. At this time, the hardware protection circuit will detect the output signal exceeding the standard. , The output is forcibly shut down to enhance the reliability of the system. After the treatment is over, the host computer software will output the relevant information of the treatment and save it to the database for follow-up use and statistical analysis of the treatment effect.
The system principle block diagram of the microwave therapeutic apparatus is shown as in Fig. 1.
4 Control system
The control system is the core of the entire treatment instrument, and all control commands are issued by it, so the stability design of the control system is the key to the entire design.
In order to enhance the reliability and anti-interference of the instrument, a special hardware protection circuit is used. When the hardware fails, the output of the microwave is not controlled. When the power exceeds the set value, the hardware protection circuit will be triggered and automatically shut down. The output improves the safety of the entire microwave therapeutic apparatus. The embedded operating system is adopted in the software design, which greatly improves the stability and anti-interference of the whole system. In order to improve control reliability and fast response performance, PID closed-loop control is used. At the same time, the output power of the microwave tube is affected by the grid voltage, working temperature and working time. Its output has nonlinearity, hysteresis, time-varying, etc. Characteristic, so the input of the sensor is fitted in sections, and different correction coefficients are set in each section to make the output more stable.
4.1 Control system hardware design
The hardware is mainly divided into the following parts. The power supply provides power for the control system; the keyboard and LCD Display circuit complete the man-machine dialogue function; the control circuit of the magnetron achieves the treatment effect of different diseases of the patient according to the requirements of the program instructions; the hardware protection circuit provides reliability for the failure of the control system The power sensor and AD converter monitor the output of the microwave tube; the output drive is completed by the relay and the thyristor at the same time; the communication circuit completes the information exchange between the controller and the host computer; the buzzer drive circuit is combined with the light-emitting diode Carry out alarm work for the end of preheating, the end of treatment and failure.
The block diagram of the hardware composition is shown in Figure 2:
4.1.1 Power supply and human-computer interaction circuit
In order to prevent interference from entering from the power supply, the power supply is composed of a switching power supply and a filter circuit, which has better anti-interference performance. In order to facilitate the operation, set the treatment physiotherapy conversion key, work pause key, power adjustment key, time adjustment key and reset key; the Display adopts LCD screen and LED indicator to display the current power, time and treatment status and other information.
4.1.2 The control and drive circuit of the magnetron
Magnetron is the emission source of microwave. It is composed of anode, resonant cavity, cathode and magnetic field. When 3.3V DC filament voltage is applied to the magnetron filament to heat the cathode, at the same time, a DC high voltage of about 2000V is applied between the anode and the cathode. , The electrons emitted by the cathode fly to the anode under the action of a strong magnetic field. There are multiple small resonant cavities on the anode. When the electrons hit the anode, they oscillate in these resonant cavities. The resonant frequency is about 2450MHz. After the treatment starts, the relay is closed, and the thyristor is triggered after the zero crossing point to control the intensity of the microwave. At the same time, the power sensor starts to work to monitor the microwave intensity. When the thyristor breaks down or other faults occur and the system cannot control the output of the magnetron, the value collected by the power sensor is greater than the upper limit of the safe power. When the thyristor is disconnected, the hardware protection circuit will act and shut down. The relay disconnects the high-voltage power supply and alarms at the same time to remind the operator that the instrument is malfunctioning.
4.1.3 Alarm and communication circuit
The alarm circuit is mainly composed of light-emitting diodes and buzzers. When the treatment is over or there is a failure, the alarm circuit will act and notify the operator of the current state by sound and light. The communication circuit is mainly responsible for the data communication between the instrument and the upper computer. After the treatment is completed, the relevant information of the treatment is uploaded to the upper computer.
4.2 Control system software design
The system software includes two parts: the upper computer and the instrument software. The upper computer software is written by VB, which mainly records treatment information for follow-up diagnosis and statistical analysis of treatment effects. The microcontroller part adopts the MicroC/OS-II embedded operating system, which greatly enhances the stability and anti-interference performance of the entire control system, speeds up the design and the code is easy to maintain.
In the treatment state, the relay is first closed, and then the zero-crossing point of the voltage is detected. After the zero-crossing point, the thyristor is triggered with a delay. The delay time is controlled by the PID closed-loop system composed of the output drive circuit and the power sensor. Since the output of the microwave tube does not change linearly, the input of the sensor is corrected and fitted in sections with different correction coefficients, and then used for PID adjustment. Improve the reliability and rapid response capability of the control system, and make the output more stable.
The program flow chart is shown as in Fig. 3.
The author of this article is innovative: the microwave power control scheme fundamentally solves the problem of microwave output power imbalance. The added protection circuit on the hardware greatly improves the safety performance of the instrument. The control strategy adopts the method of segmented fitting and PID control fusion, which has the characteristics of good linearization, and high precision and stability of PID control. Good advantages, overcome the difficulties caused by nonlinearity, lag, and time-varying in microwave power control.