Research On Structure, Driving And Controlling For Piezoelectric Pump Driven By Single Signal Or Dual Signal

The piezoelectric pump has features of small size, low power consumption, no electromagnetic interference, low noise, where the fluid can be controlled precisely by electrical signal, so it has broad prospects in biomedical, chemical analysis, chip cooling, inkjet printing, and it is a hot research topic in the field of micro-fluid. Compared to comprehensive research on structure of piezoelectric pump, research on driving and controlling is insufficient currently. Therefore it is necessary to emphasize on researching on this field. In this paper, supported by the Ministry of Education Scientific Research Innovation of Higher School Major Cultivation Fund project and National Natural Science Fund project, around system of piezoelectric pump driven by single signal or dual signal, research on structure, driving power supply, working performance, flow self-measurement, precise control of liquid delivery is carried out.1. Analysis and testing about piezoelectric vibrator propertiesMechanical property (resonant frequency) and electrical property (relation of driving frequency and impedance modulus) of piezoelectric vibrator is studied employing Butterworth Van Dyke equivalent circuit model. Experiments on circular piezoelectric bimorph vibrator are made, including deformation of each point on surface, relationship between center displacement and driving voltage, driving frequency. The works make ready for structural design, driving power supply on next step.2. Development of piezoelectric pump driven by single signal or dual signalWorking principle of piezoelectric pump driven by single or double signal (including piezoelectric pump with single chamber single piezoelectric vibrator, piezoelectric pump with double chamber in serial, piezoelectric pump with double chamber in parallel, pump combined with active and passive valve, piezoelectric pump with dual active valve) is analyzed. Results show:compared to piezoelectric pump with single chamber and single piezoelectric vibrator, the piezoelectric pump with dual chamber in serial can generate a greater pressure and a larger flow; the piezoelectric pump with dual chamber has better output performance in asynchronous driving mode than in synchronous driving mode; piezoelectric pump with dual active valve has a wider range of working frequency, and can realize two-way transmission of liquid, has a unique output performance. 3. Development of driving power supply for piezoelectric pumpBased on analysis of driving signal, and aiming at piezoelectric pump driven by single signal or dual signal, three types of driving power supply are developed, including analog driving power supply for single-phase piezoelectric pump, programmable-controlled driving power supply for single-phase piezoelectric pump and digital-controlled driving power supply for dual-phase piezoelectric pump. Working mechanism of overall and each schematic is analyzed, and testing experiment on electrical output performance is carried. In driving power supply developed, the voltage output can be adjusted from OV to the maximum, the maximum output voltage is not less than170V, and the frequency can be adjusted from5Hz to500Hz. Among them, analog driving power supply for single-phase piezoelectric pump has features of small size and low cost. Output parameters of programmable-controlled driving power supply for single-phase piezoelectric pump can be adjusted by buttons, the adverse impact caused by the potentiometer is avoid, so the signal output is reliable and stable. Digital-controlled driving power supply for dual-phase piezoelectric pump uses direct digital synthesis technology to generate two sine signals with strict phase difference, the phase difference can be adjusted in range of0°-360°, with minimum resolution of11.25°, the output parameters is digital-controlled and displayed in real time. Output parameter of the power supply can be adjusted independently and continuously, control of piezoelectric pump is easy and flexible.4. Experimental research on output properties of piezoelectric pumpExperimental research on output properties of piezoelectric pump is carried applying the driving power supply developed. Results show that the flow rate and pressure is increasing with driving voltage. For piezoelectric pump with dual chamber connected in serial, it has better frequency adaptation when driven in asynchronous driving mode, with operating frequency range of10Hz-400Hz, maximum flow rate of94.174mL/min, and slight change in pressure. For the piezoelectric pump with dual chamber connected in parallel, it has better output performance when driven in asynchronous driving mode. The piezoelectric pump with dual active valve has a wide range of operating frequency (10Hz-220Hz), where transporting direction and flow rate of the liquid can be controlled by changing the phase difference between signals. Compared with other piezoelectric pump developed in this paper, it has unique output performance.5. Method of flow rate self-measurement for single chamber and single chamber piezoelectric pump based on piezoelectric self-sensing functionMethod of flow rate self-measurement applying piezoelectric self-sensing function is proposed. The factors affecting flow rate and the relation between deformation and sensing signal of piezoelectric vibrator are discussed, results show that there is clear correspondence relationship between flow rate and sensing signal, the information of flow rate is implying in piezoelectric sensing signal. Parameter measurement circuit for piezoelectric sensing signal is developed. BP neural network model for flow prediction is constructed where information of voltage and frequency are input, and predicting result of flow rate is obtained. Testing experiment for flow rate is carried and experimental results show that:correlation coefficient between predicting value and measuring value is more than0.9993, the maximum relative error is less than3.46%. Method of flow rate self-measurement proposed has good accuracy, and can also be applied to piezoelectric pumps with different structure and different mechanism.6. Precise control method for liquid conveying applying electric pulses with given numberBased on analysis of driving characteristics and output performance for piezoelectric pump, research on precise control of liquid delivery applying given number pulses is carried. Controlling circuit for electric pulse with given number is developed, and testing experiment on liquid delivery control is done. Experimental results show that there is a good linear relationship between volume of liquid delivered and pulse number. The maximum relative error is0.424%, the correlation coefficient is0.9999. Method of liquid conveying control based on given number is feasible. Therefore, in occasions of precise fluid delivery, we may calculate the corresponding number of pulses according to target volume, and send pulses with given number to the piezoelectric pump to achieve precise control of fluid delivery.