Research On The New Piezoelectric Feeder

Piezoelectric vibration feeder are developed in this thesis with the support of national science foundation program"The driven theory and research of ultrasonic vibration feeder". This piezoelectric vibration feeder has many merits, such as high energy density, huge driven force, quickly respond, high displacement resolution. So in some place it can drive small parts and replace the traditional electromagnetic vibration feeder and belt transmission. This thesis study on how to drive the multi-bimorph and the enclitic springs be in harmonic oscillation and drive the parts to moving forwards. In the research on the piezoelectric vibration feeder, there are many theoretical derivation, finite element analysis and experiments. The thesis designed a piezoelectric vibration feeder that the bimorphs are placed on horizontal placement. The thesis also studies on structure designing, processing, assembling, theories analyzing and doing experiments. The piezoelectric vibration feeder involves piezoelectrics, mechanics of vibration, tribology, electrical control and experimental technique. There are met many problems and heavy workload.1. The research purpose of piezoelectric vibration feederThe traditional electromagnetic vibration feeder isn't absolutely fit for the factory, because that its noises, slowly respond, complicated structures, precision transportation, wearing more electric power consumption. These years the piezoelectric materials are developed. Piezoelectric materials are applied in many high technology and manufacturing production fields. The development and application of more piezoelectric materials make the research on piezoelectric vibration feeder be probabilized. Piezoelectric vibration feeder is quieter, lower electromagnetic interference, lower electrical power consumption, lower cost, quickly respond, simple structure than the traditional electromagnetic vibration feeder. If we have some new patents on piezoelectric vibration feeder in China, we can sell our own feeds and overseas piezoelectric vibration feeder will reduce the price. So the piezoelectric vibration feeder can be used in many fields.2. The analysis and experimental study of piezoelectric multilayered actuatorThe piezoelectric actuation principle and the correlative basic theory is the theoretical start of analyzing piezoelectric bimorphs. So it is necessary to explain the basic theory of piezoelectric actuation. The basic physical properties and main performance parameters are discussed. They are electromechanical coupling factor, piezoelectric constant and mechanical quality factor etc. The relationship of stress, strain and electric variables are discussed combined with four groups of piezoelectric equations. The basic theory of piezoelectric actuation is clarified and it will indicate the modeling analysis of piezoelectric bimorphs. The performance of the driven actors is critical influencing factors to the transmission, so the piezoelectric bimorphs is necessary to be analyzed deeply. The mathematical model of piezoelectric bimorphs is established using equivalent scheme. The simplified model of piezoelectric bimorphs is obtained based on the equivalent circuit theory; The finite element model is established by finite element Model. The output displacement characteristics, open-circuit stiffness and short-circuit stiffness is analyzed. The natural frequency and modal is analyzed with the modal analysis. The precise displacement measure and control system, stiffness testing system is established and the displacement and stiffness characteristics are tested and analyzed; The impedance analysis of piezoelectric bimorphs is carried by impedance analysis methods and the impedance characteristics is obtained; The frequency response of piezoelectric bimorphs is tested by establishing dynamic testing system and the dynamic characteristics are measured. The results of theoretical analysis and experimental testing show that the deformation of the ends decrease when the base plane is increased which the piezoelectric bimorphs is at static. When the piezoelectric bimorphs is dynamic and driven by sine AC, the steady state response is the corresponding respond at the same frequency. When the drive frequency of the piezoelectric bimorphs is in the field of resonant frequency, the ends of piezoelectric bimorphs can enlarge the deformation. The phase of the steady state response is lagged the frequency of the driving voltage. And the faster is the frequency, the greater is the lagging.3. The structure analysis, design and experiment of the piezoelectric vibration feederEstablished the mechanical model of the piezoelectric vibration feeder and analyze the elastic coefficient of the piezoelectric bimorphs and the main spring. The coefficient can change the performance of the piezoelectric vibration feeder. Designed the main structure and the parts, and select the last structure in the thesis. Analyze the movement of the carried objects. When neglect some secondary factors, the piezoelectric vibration feeder can be simplified mechanics of vibration model of double objects. And get the formula of natural frequency and swing of the system. According to the formula, the natural frequency of the system is increased when the elastic coefficient k1 of piezoelectric bimorphs and the elastic coefficient k 0 of main spring are increased. And the swing is decreased when k 0 is increased. The experiments are that designed, processed and assembled the main parts of the piezoelectric vibration feeder. And every part is manufactured on some different parameters. After assembled, many cross-over experiments have been done. The experiments confirmed the last structure. The resonant frequency is 93 Hz that is tested by precise impedance analysis instrument, and the result is almost the same as the result that is tested in the experiments. The differential equation of the carried objects set the movement of the objects. Analyze the conditions of the slide and jump of the carried objects.4. The study on the design of the power controller of the piezoelectric vibration feederThere are many forms and structures of the piezoelectric ceramics and the ceramics is made to many actuators. The actuators can be slabby strip vibrating in the transverse direction, and they can be disk vibrating in the radial direction. The claviform vibrate in the lognitudinal direction. The piezoelectric actuators can be classified according to the principle of work, such as the frequency mode, the electroacoustical mode, the ultrasonic transducer mode, the inflamed and the detonated mode, the piezoelectric transformer and the drive mode. The many actuators can be used to design many strctures, and the drive powers are different on each of the piezoelectric machines. The piezoelectric vibration feeder of this thesis is drived by microprocessor, DA amplifier, operational amplifier, push-pull amplifier circuit and the transformer. Ths size of the microprocessor is small. The microprocessor is easy to use and the AD/DA functions are on the chip. The performance of the microprocessor is excellent and it is at a low price. So it is very fit to be regarded as the power core of the piezoelectric vibration feeder. The design of the PCB (Printed circuit board) takes notice of the electromagnetic compatibility. The electric power low the interruptions to the other electric device and the reliability and quality of the electric power is excellent. There is watchdog in the the electric power and it can guarantee that the program in the microprocessor runs safely. This is taking out the system halted and errors.5. The research on the control means of the piezoelectric vibration feederThe piezoelectric vibration feeder works at resonance frequency. This thesis uses an acceleration sensor to test the vibration of the holder. The sensor can measure the acceleration of the two vertical directions and change the acceleration to PWM(Pulse-width modulation). The microprocessor can measure the PWM and calculate to output the value of DA register according to the equivalent syntonic circuit model and the optimal algorithm. The program of the power controller combines the algorithm with the real-time operating system. The real-time operating system can reinforce the real-time operation in the response of the external interrupts. The program is easy to modify, extend and maintain with the real-time operating system. The vibration of the feedback system can increase the carring performance. The application of the microprocessor is easy to work at the user's configurations of the piezoelectric vibration feeder.6. The research of the performance of the piezoelectric vibration feederThis thesis estabilished simplified experiment table in order to analyze the carring performance of the piezoelectric vibration feeder. Test the swing on vertical direction of the ends. The carried speed of the every object is tested in a fixed distant. From the testing, the parameters that are drive voltage, swing, carried speed and the drive frequency affect the performance of the piezoelectric vibration feeder. The conclusion is that the piezoelectric vibration feeder is working, the swing on vertical direction of the holder's ends is about 50-60μm. The swing of the holder and the drive voltage are in a linear proportion. The higher is the voltage, the wider is the swing. The carried speed and the drive voltage are also in a linear proportion. The higher is the voltage, the faster is the carried speed. When the frequency of the drive voltage is near to the natural frequency, the swing and speed are obvious enlarge. The characteristic of the carried objects and the arrangement on the path also can affect the natural frequency. The density of the carried objects is bigger and the speed is faster than others.