A new tracking method with FPGA chip for ultrasonic welding system
A new feedback control method of using field-programmable gate array (FPGA) chip for ultrasound welding system is appeared in this article. This feedback control circuits of ultrasound welding system consists of microprocessor control unit, signal generator, power amplifier, the feedback of voltage detector and current detector, etc. The experimental results exhibited this feedback control method can effectively and automatically catch frequency and rack a proper frequency for the ultrasound welding system.
New type of compact control system for frequency and power in megasonic transducer drive at 1 MHz
This paper describes a new type of compact megasonic transducer drive which can control both the frequency and power at a frequency of 1 MHz when the megasonic transducer is used for cleaning the surfaces of silicon wafers or LCD faceplates. A pulse width control is used to control the widths of the drive pulses for the full bridge inverter having a maximum output power of 60 W so that RF output power is set at the specified values. The output voltage of the full bridge inverter is fed to the megasonic transducer through both the output transformer and the low pass filter to eliminate harmonics from the RF voltage since the low pass filter is the key circuit to effectively feed RF power to the megasonic transducer. The megasonic transducer current and voltage are compared with each other by the PLL so that the frequency of the VCO output voltage is set at four times the resonant frequency of the megasonic transducer. The RF output power was satisfactorily controlled from SW to 60 W when the duty cycle of the drive pulse width was changed from 20% to 49%. The frequency of operation was satisfactorily locked at 4/spl times/1.04 MHz when the frequency of free-run oscillation in the VCO was up to 4/spl times/1.15 MHz. The megasonic transducer was satisfactorily operated at an RF power of up to 60 W when put in water.
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.