Research On The Active Electromagnetic Damping Technology At A Half Stroke & Its Application In Force Standard Devices

Measurement, analysis and research on the force will be necessary in many fields of the national economy, such as industrial machinery and construction industry, or in the process of the scientific research and production testing.The Standard force machine is a kind of apparatus which can generate standard force. As a standard force machine, the dead weight standard force machine is used to measure the load sensor with many weights, which are weighed by standard balance. In the process of the loading and unloading, the weights will swing. Generally, the frequency of the swing is less than 10Hz, so, this kind of swing is named as low-frequency swing. Because of this phenomena of swing, the force accuracy of the dead force standard machine will be minished, the cycle time of the data recording will be extended, and the work efficiency of the machine will be reduced.The traditional techniques and methods can not inhibit the low-frequency swing effectively. In order to solve the above problems, in this dissertation, I make use of the technology named"half stroke active electromagnetic damping"to inhibit the swing of the weights. Then, I have analyse the theory in detail and validate the theory with a lot of experiments. The main content and conclusions include:Ⅰ. Discussed the structure and working element of the the force standard machine in detail, analyse the cause of the low- frequency swing and its harmful effectsThe dead weight standard force machine(DWSFM) is made up of frame, moving beam, suspension system, weights system, loading and unloading device, swing inhibiting device and PC control system. The dissertation analyse the cause of the low-frequency swing, inclues internal and external reason. The mainly external reason is impact load, and the mainly internal reason is manufacture error and assembly error. Through the above analysis, we recognize that swing of the weights is objective and inevitable.Secondly, I analyse the harmful effects which are brought because of the swing. This phenomena makes the stable time longer so that the sensor which is testing creeps seriously, makes the work efficiency lower so that the production costs of the sensor manufacturers. But the most serious is that the weights swing reduce the force accuracy of the DWSFM. The article analyse the accuracy error(δFs) accurately that is brought by weights swing. The conclusion is that the error is in direct proportion to the amplitude.Ⅱ. Established a simplified mathematical and physical model of the weights system.Through the above analysis about the structure and working element of the dead weight standard force machine, I have established a simplified mathematical and physical model of the weights system. I predigested the complex swing system to a simple physical model named"Spring-Mass- damp System". It is proved that this predigestion model is totally correct and logical. Using this method, the swing system in other standard force machine also can be predigested to"Spring-Mass- damp System".Ⅲ. Presented an engineering method to inhibit the swing of the weights though making use of the theory of damping absorber.In this paper, after making use of the theory of damping absorber and lighting of actual conditions of the weights swing in Standard Force Machine, we presented a engineering method named"half stroke active electromagnetic damping". The actuator is composed of one electromagnet only, so the direction of the control force(electromagnetic force) only points to the equilibrium position. When the weights swing from the position of equilibrium, the system imposed movement control, when the weights swing far from the equilibrium position the system does not exert control, it is the concept of the "half stroke".Compared with the traditional active damping technology, this method have many advantages such as simple structure, economical and practical, sensitive response etc. In addition, this method have no contact with the weights and meets the work requirements of the SFD that developed by International Organization of Legal Metrology(OIML).The control system is the the core of this technology. In the paper, we designed a simple PD open loop control system, including the controller and displacement sensor, A / D acquisition card, D / A conversion card, power amplifier and actuator device is electromagnet At the same time, the preparation of the control procedures. All of the above provide the protection for the correct work of the half stroke active electromagnetic damping system.Ⅳ. Analysed the structure of the weights system and designed simulation device for experiments. Accroding to the contrast of the experimental results, summarized the swing law in the effects of the half stroke active electromagnetic force.Through a series of experiments, analysed the impact of different damping ratio, different quality of weights, different weights position and different gap distance,etc. Experiments show that half stroke active electromagnetic damping technology is feasible, it can inhibit the low-frequency swing of the weights effectively. The results also show that if the damping ratio is greater or the gap ftom the electromagnet to the weights is smaller, the effect of damping will be better. Instead, the effect of damping will be worse. The weight in the quality and location of the damping effect of a great impact in light of this technology in the standards of the source device applications to achieve optimal damping effect of the damper two methods, namely, "Set the largest damping ratio" and "automatic adjustment of the damping ratio," a more practical analysis shows that the former Second experiment also showed that, if adopted a series of measures to detect and control accuracy improved, and can fully adopt a more simple "Switch" control algorithm damping device control, not only simplifies the control and reduce costs, and make the technology more practical value.To sum up at last, the half stroke active electromagnetic damping technology which is presented in this paper is correct and feasible. It can inhibit the low-frequency swing of the weights effectively and meets the work requirements of the SFD that developed by International Organization of Legal Metrology (OIML). So, the research on this project have great practical significance and practical value.