Fabrication and test of an electric spindle integrated with an electromagnetic balancer
This paper focuses on the development of an electric spindle integrated with an electromagnetic ring balancer. Firstly the electromagnetic ring balancer is designed and then 3D model of self-balancing spindle integrated with this balance er is created. Based on the design, an on-line balancing principle of self-balancing spindle is proposed. The prototype machine fabrication process of the balancer's key parts including coil, counterweight disc and toothed disc are discussed. For an actual spindle, the detailed design and development of this balancer are done, particularly the balancing craft of the combined rotor is done on a balance machine before delivery. By installing the balancer on the front end of spindle using flange, a self-balancing spindle prototype is obtained. In workshop, the vibration test of the developed self-balancing spindle is carried out in the range of 3000r/min to 9000r/min. The result shows the developed self-balancing spindle has a vibration velocity below 0.5mm/s. Finally the two eddy current sensors are applied to evaluate the vibration suppression capability of balancer, the experimental result is that about 15um peak-peak value can be eliminated when the correction value of balancer changes from 0 to 38.55g.cm in 3000r/min.
Development of the active balancing device for high-speed spindle system using influence coefficients
Abstract A high-speed spindle can be very sensitive to rotating mass unbalance which has harmful effect on many types of rotating machinery. Therefore, the balancing procedure is certainly needed to reduce vibration in all high-speed rotating systems. In this study, an active balancing program using influence coefficient method and an active balancing device of an electro-magnetic type with both simple and reliable structures were applied to the developed high-speed spindle system. A gain scheduling control using influence coefficients of the reference model was proved to be effective in balancing the spindle system although its characteristics were changed. The stability of reference influence coefficients was verified by experiments with frequency response functions. The active balancing experiment of the manufactured spindle system using an active balancing program and device was also performed efficiently during the operation. As a result, controlled unbalance responses after balancing work were below the vibration limit at all rotating speed ranges including critical speeds.
Robust solutions of inverse problems in electromagnetic non-destructive evaluation
Non-destructive testing (NDT) is the application of physical measurement technology based on energy interaction with the material and its nonconformities. The material's response is sensed by transducers and sensors which?in most cases?scan the component and document the results in inspection images. However, NDT measures a physically defined quantity or even an intrinsic property. The difference between non-destructive evaluation (NDE) and NDT is in the interpretation of the inspection data. NDE has to discuss the inspection results in terms of quality elements and characteristics which are relevant to describe the fitness of the material for use. In the case of macroscopic defects these are the kind of defect (cracklike, globular) and its size and orientation to the main stress directions; in the case of material property determination the parameters are mainly mechanical properties. Therefore, in NDE one has to solve inverse problems. The solution of inverse problems based on mathematical procedures such as integral equations is a strong developing discipline and most of the articles prepared for this special issue of the journal have the objective of discussing the latest state of the art in that field. However, practical NDE needs robust and quick solutions which are to be applied mainly online. Therefore, we present here inversion procedures based on multiple linear regression algorithms applied to inspection data. We describe the calibration procedure to fit the free parameters of the model functions and give examples of practical applications in industry.