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.
Design of an automatic impedance matching circuit based on frequency tracking of ultrasonic transducer
Ultrasound is widely used in ultrasonic detection, ultrasonography, ultrasonic oscillation, ultrasound extraction and so on. During the use of power ultrasonic transducer, the resonance frequency of the transducer tends to shift due to the changes of transducer load, aging, wear, temperature rise, fatigue and other factors. At present, there are a large number of circuit designs for automatic frequency tracking of ultrasonic transducers, but few design schemes for automatic adjustment and control of impedance matching circuit. This paper designs a circuit which can automatically adjust impedance matching based on automatic tracking of ultrasonic frequency.
Submicron polymer structures with X-ray lithography and hot embossing
This article describes the process chain for replication of submicron structures with varying aspect ratios (AR) up to 6 in polymethylmethacrylate (PMMA) by hot embossing to show the capability of the entire LIGA process to fabricate structures with these dimensions. Therefore a 4.7 μm thick layer of MicroChem 950k PMMA A11 resist was spin-coated on a 2.3 μm Ti/TiOx membrane. It was patterned with X-ray lithography at the electron storage ring ANKA (2.5 GeV and λc ≈ 0.4 nm) at a dose of 4 kJ/cm3 using a Si3N4 membrane mask with 2 μm thick gold-absorbers. The samples were developed in GG/BDG and resulted in AR of 6–14. Subsequent nickel plating at 52°C resulted in a 200 μm thick nickel tool of 100 mm diameter, which was used to replicate slit-nozzles and columns in PMMA. Closely packed submicron cavities with AR 6 in the nickel shim were filled to 60% during hot embossing.