Key Engineering Materials Vols. 295-296

Abstract: It has been proved that artificial intelligence leaned on self-checking is an efficient factor for increasing metrological reliability of measuring instruments. The possibility to create intelligent measuring instruments based upon redundancy of measurement information and informational redundancy of a measuring transducer is presented. Practical examples are provided.

Abstract: Efficient development of method for performance evaluation of machine tools has been regarded as the most important issue to enhance accuracy and quality for users and manufacturers. Recently, a method of accuracy evaluation for machine tools has been studied as interests on precision machine tools have rapidly increased. From this point of view, the circular interpolation test of machine tools is recognized as the most useful method to identify the dynamic accuracy of NC machine tools by ISO, ANSI/ASME and others. In this paper, we studied and developed a formal measurement system with a grid encoder to analyze the final accuracy of NC machine tools. We analyzed the servo system error and the geometric error of NC machine tools through measuring the dynamic error signals by using this system. We verified the experimental result and enhanced the reliability by means of comparing the characteristics of the developed system with the kinematical ball-bar system.

Abstract: Evaluation of the dynamic parameters of a modulator based grinding machine system, which is underdamped, is presented. The modulator is one of a displacement-frequency type for dynamic manipulation of the stepping motor of a tool feed system which is part of a composite grinding system for a wide bandwidth control involving both low and high frequency signals. To obtain the parameters of the underdamped system, a method of multiple uses of the transient displacement responses to step commands is proposed to reduce assessment errors. The parameters to be obtained include damping ratio, undamped natural frequency, time constant, and settling time. The evaluation results were obtained based on the minimum of a composite error index using a second order dynamic system model for reference. The parameters will be useful for further development of the composite control for the precision machining process.

Abstract: A high speed painting automizor system with elastic support is presented. Experimental tests of the system including the key part, the rotor-bearing system, were conducted using the experimental modal method under various working conditions. The natural frequency of the system is given and the relationship between the bearing stiffness and the natural frequency and amplitude are studied. Fault of the bearing GCr15 is analyzed. The experiment has three parts including the experimental theory, experimental design, and experimental data processing. The results will lay a solid foundation for further investigation on dynamic design, maintenance, working condition monitoring and fault detection of the painting automizor system.

Abstract: Nonlinear independent component analysis (NICA) is a powerful method for analyzing nonlinear and nongaussian data. Artificial neural network (ANN), especially self-organizing map (SOM) based on unsupervised learning, is an excellent tool for pattern clustering and recognition. A novel multi-NICA network is proposed for feature extraction of different mechanical patterns, followed by a typical ANN that is one of Multi-Layer Perceptron (MLP), or Radial Basis Function Network (RBFN), or self-organizing map (SOM), which implements the final classification. Using NICA and appropriate strategies for further feature extraction, nonlinear and higher than second order features embedded in multi-channel vibration measurements can be captured effectively. Mechanical fault patterns can be recognized correctly. Results from the contrast classification experiments show that the new compound ICA-SOM classifier can be constructed in a simpler way and it can classify various fault patterns with high accuracy, both of which imply a great potential in health condition monitoring of machine systems.

Abstract: Spatial resolution in the conventional optical microscopy depends on diffraction limit. Photon scanning tunneling microscopy is one of the microscopic methods that surpass the diffraction limit. It scans an object with detecting evanescent wave on object surface. Evanescent wave is scattered by the tip of a fiber probe and guided to a detector by the fiber probe. Not all of the scattered ray can be detected. Only the scattered ray from the aperture of a fiber probe can be detected. We propose to improve an image by detecting the state of scattered ray and a new method to maintain the probe sample distance constant by keeping the quantity of scattered ray constant.

Abstract: Research achievements in a high speed attraction type magnetic levitation vehicle experimental system are reported. The high speed attraction type magnetic levitation vehicle constitutes a typical long stator linear synchronous motor. The study on levitation and propulsive electromagnetic fields is of great importance and is studied. Owing to the influence of the stator grooves and the material discontinuousness, the magnetic field distribution is very complex to be analyzed in analytical forms. The magnetic fields in the air gap are determined using the finite element method. The levitation force and thrust produced by the levitation magnetic field and the propulsive magnetic field are calculated. They are found to vary following the change of the air gap and exciting current. A magnetic field strength measurement system based on a hall sensor is designed. Experimental results are compared with the results from the magnetic field analysis.

Abstract: A direct digital synthesis (DDS) waveform generator for electromagnetic non-destructive testing (NDT) is presented in order to improve the measurement quality. The advantage and disadvantage of analogue and digital circuit waveform generators are analyzed. The DDS technique is preferred. The principle of DDS technique is introduced and the hardware and software design of a DDS waveform generator is described. The characteristics of the waveform generator based on a DDS chip AD7008 are that the signal frequency is of high stability, high precision and high resolution. Furthermore, the amplitude, frequency and phase can be continuously adjusted. An experimental electromagnetic NDT system is built and the testing results are analyzed. The system uses digitally generated sine waves as exciting, reference and demodulation signals. Experimental results show that the DDS waveform generator improves the signal-to-noise ratio. This kind of wave generation circuit is used not only in NDT but also in other instruments, such as electrical impedance tomography (EIT), which need signals with high stability, high precision and high resolution.

Abstract: It is important to improve the reliability of the eddy current non-destructive testing. It is generally difficult to reduce the probability of non-detection and the number of false alarms same time. Model Based Measurement (MBM), including estimation of state, failure diagnosis and trend analysis, has excellent results on general estimation. Actual results of MBM vary with the application domain, mathematical model and data processing. The time series model is a description of system in time domain based on equivalent output. The Kalman filter is an efficient method for suppressing the disturbance and improving the state estimation. A new method, called as eddy current testing (ECT) using a model based measurement, is presented. Two time series models are used for the normal status and the abnormal status in ECT. The Kalman filter on these models is applied to give useful information for decision making. Results of the experiment on aluminum plates demonstrate that this method is useful to improve the detection reliability.

Abstract: A new approach for power system frequency estimation is proposed. The approach consists of two stage adaptive notch filters. The first stage eliminates harmonics and enhances the fundamental waveform. After the down-sampled processing, the second stage produces an accurate estimate of the fundamental frequency. The notch filter is based on all-pass filter with an efficient lattice structure and is simple to realize. Simulation is presented to demonstrate the effectiveness of the algorithm.