Research On Closed Loop Control Of Broadband Ultrasonic Biological Treatment System

The ultrasonic wave is generated by using the ultrasonic vibrator. The frequency and amplitude of the ultrasonic vibrations determine the frequency and power of the ultrasound. Therefore, the control of the ultrasound can be summarized as being the control of the vibrations. Ultrasonic vibrators are usually composed of piezoelectric ceramic, which can convert electrical energy to mechanical energy. Every vibration has its specific resonance frequency. When its external voltage frequency is equal to its resonance frequency, conversion efficiency will be at its highest state. Generally speaking,only single frequency mounted ultrasonic vibrator equipment exists in the market, which is most suitable for industrialized production. It does not apply to the laboratory with broadband on demand. Otherwise, if controlled with a closed loop, the frequency and power of the ultrasonic wave wouldn’t have a large drift.Focusing on the broadband and closed loop control, the main components are as follows: the design of an ultrasonic biological treatment tank with four different resonance frequency ultrasonic vibrators located at the tank bottom; A built-in 15 V switching power supply generator system for the control of the MOSFET and power for the motherboard; An adjustable power supply with output voltage between 0~300V for the ultrasonic vibrator, so as to achieve the power regulation function; With the voltage detection circuit the output voltage of the Buck circuit can be a closed loop control system; Utilizing an adjustable frequency wave and adjustable voltage source the corresponding driving frequency and voltage will have an affect on the vibrator; A 7 inch LCD touch screen is used for system parameter settings and displays; The biological treatment tank has protein detecting sensors, which can provide feedback on the concentration of protein in the tank, real time; A motherboard with an ARM processor is responsible for overall control such as touch screen display and control and PID algorithm calculation; A FPGA chip is responsible for complex multi PWM waveform generation;Through the above research the system design of the hardware, software and prototype tests have been completed. The test results show that the design of broadband and closed loop control ultrasonic system can generate an ultrasonic frequency between 20kHz~40kHz, while the voltage of the Buck circuit is adjustable in the range of 0V~300V.