Research On The Multi-point Piezoelectric Vibratory Feeder And The Control System

Piezoelectric drive technology is a new-developing study area. It combines piezoelectric, acoustics, vibration, electrology, mechanics, tribology and material technology. Piezoelectric vibratory feeder is a sort of new-style feeding equipment which is driven by piezoelectric vibrator instead of traditional mechanism, electromagnet or engine etc. Compared to the traditional vibration feeders, this new feeder has a lot of advantages, such as simple structure, small volume, wide range of feeding rates, high reliability and stability, energy saving and so on.Based on the research of piezoelectric drive technology and vibratory feeder technology, and especially for the current status existed in domestic medicine, food, chemistry and feed industries which have to face the problem that grain material may splash heavily during feeding process, we have developed a new multi-point piezoelectric vibratory feeder. It can convey grain and powder materials with suitable fluidity stably, efficiently and air-tightly. And based on the successful trial-producing of the model machine, we have also developed a special drive and control system for timing convey, fixed quantity and shift speed convey.The main contents of this paper are as following:1,Based on the analysis of worldwide current status and tendency of the piezoelectric drive feeder technology, we have designed this multi-point piezoelectric vibratory feeder. It consists of vibration stuff box, driving piezoelectric chips, measuring piezoelectric chips, feeder, obliquity adjusting part and holder. According to the contra-piezoelectric effect, it uses the piezoelectric vibrator as vibration source to generate traveling wave in elastic medium, and works together with the geometric guiding structure to realize the directional convey. This feeder is more simple and economical compared with the traditional vibratory feeders, and it can convey grain and powder material air-tightly.2,The Research of its mechanism. First we use the piezoelectric ceramic chips as the sensor to detect vibration. When the device is on working, we can observe the signal wave shape output from the 2 piezoelectric chips which are fixed on the different positions of the stuff box. We analyzed it and got the conclusion that the resonance of the vibrator spreads as a traveling wave. Then we analyzed the mechanism of the device in theory and considered that the power which moves the stuff is the result of the combination of the particle's elliptic movement in the elastomer surface, the destruction to the grain's natural balance status caused by the vibration and the geometric position-limit guiding structure of the device.3,Experimental research for the performance of the device. We have researched the influence of the 7 following factors to feeder speed and stability: the number of the chips, the chips'position, working frequency , voltage the phasic difference of the input signal, stuff categories, obliquity angle, supporting points through a lot of experiments, and found the influence regularity caused by different parameters. We have also proved the mechanism"the associated action of particle's elliptic movement, the destruction to the grain's natural balance status caused by the vibration and the geometric position-limit guiding structure", optimized the parameters for the structure, and found both the relation between the working voltage and the feeding speed, and the relation between the detector signals and the feeding speed are approximately linear. We build several linear equations which use driving mode and stuff categories as variables to provide a theory for the drive and control system.4,We have designed a special drive and control system for the device, including both hardware and software. First we used the SCM as the core part, used the modulization designing idea as principle to design the hardware. It mainly includes: SCM periphery module, serial communication interface module, driving circuit module, reactive circuit module. Then we developed the software by use of assemble language and VB for the drive and control system, including the PC and SCM programs. The PC programs mainly include: communication module, original parameter setting module, working parameter setting module, calculation control module, current working status display module. The SCM programs mainly include: main program module, serial port interruption sub-program module, frequency and phasic difference adjustment sub-program module, timing interruption sub-program module and other small sub-program modules. The PC software is responsible for sending the command according to the parameters set by the user and vibration feedback signal from the SCM to SCM. And the SCM software is responsible for controlling hardware according to the command from the PC program and sending the vibration feedback signals to PC. The drive and control system has the following main functions:â‘ It has realized to adjust the output signal, phasic detention, voltage manually.â‘¡It can detect the resonance frequency automatically.â‘¢It has realized the function for timing, fixed quantity and fixed speed feeder.â‘£It can realize real-time watching and displaying the current status.5,Test for the performance of the drive and control system. We have tested the performance of the drive control system for the device, including the output voltage, frequency, phasic difference and the performance for the closed loop of this control unit. The result is that the output signal is relatively stable and can realize the closed loop control for feeder speed.The innovation points of this paper:1,We designed a new-type multi-point piezoelectric vibratory feeder. By use of the inverse piezoelectric effect of the piezoelectric material and the traveling wave from the multi-point piezoelectric vibration, the device realizes to convey the grain and powder stuff with a stable and airtight way. This device has such characteristics: simple structure, low cost, low noise, low energy-consuming, high reliability, no damage to the stuff . 2,Through the research in theory and test, we think the mechanism is the result of the combination of the three factors: elliptic movement of the points in the elastomer surface, destruction of the natural balance of the grain stuff, and the geometric guiding unit. It achieved a bit breakthrough compared to traditional opinions.As a summary, this paper has described a new-type multi-point piezoelectric vibratory feeder, and its special drive and control system. It analyzes the mechanism through theoretical and experimental research, and found the regularity of the influence by the different structure and working parameters. This device has the characteristic of simple structure and low cost, and it can convey the grain and powder stuff with suitable fluid by a stable, efficient and airtight way.