Andrew P. Ritter

Reliability Studies on Electrostrictive Actuators

Multilayer electrostrictive actuators have numerous applications. Frequently these applications involve harsh mechanical and electrical loads. Furthermore, it is typically expected that these loads be incurred for > 108 repetitions (ideally for an infinite number of cycles). This paper describes the electrical and electro-mechanical analyses used at AVX Corporation to assess the performance characteristics of multilayer ceramic actuators, and addresses the effects of electro mechanical cycling on selected device properties. In this study, lead magnesium niobate based multilayer electrostrictive actuators were subjected to a.c. fields at rated device voltage. Capacitance, dissipation factor, displacement vs. voltage, displace ment hysteresis, electro-mechanical quality factor, and resonant frequency were monitored as a function of electro-mechanical cycling. The actuators exhibited highly stable displacements through out the investigation. Changes observed in other properties indicate a possibility of using them as NDE techniques to assess the actuator reliability.

Intelligent Process Monitoring of Multilayer Ceramic Actuators Using High Temperature Optical Fiber Displacement Sensors

The Fiber & Electro-Optics Research Center (FEORC) has developed a sensing technique for the intelligent processing of a multilayer ceramic actuator (MCA) elements manufactured by the AVX Corporation in Conway, South Carolina. Presented are the results of the fiber optic strain sensor used to monitor the burnout of organic binders from a green actuator sam ple. The results establish the operation of the short gage length, low finesse Fabry-Perot interferometric strain sensor as a tool for intelligent processing of such ceramic actuator elements. Also pre sented is the method of sensor operation, and post-processing results using the same sensor for tracking actuator performance and hysteresis.

Voltage-Controlled Capacitor—Feasibility Demonstration in DC–DC Converters

This letter presents a voltage-controlled capacitor that varies from 20% to 100% of the rated capacitance (1 μF) with a control voltage from half of the voltage rating to 0 V. Capacitance, self-resonant frequency, and equivalent series resistance were measured with respect to the control voltage. An equivalent circuit and a nonlinear model derived from relationship between permittivity and electric field were created and implemented in SPICE. A buck converter with input of 12 V, output of 5 V, and switching frequency of 500 kHz was built to demonstrate the change from 85% to 40% of the rated capacitance of the voltage-controlled capacitor. The error between the simulation and experiment was limited within 10%, which verifies the model.

The Effect of Electrical Fast Transients on Multilayer Ceramic Capacitors

This paper investigates the susceptibility of multilayer ceramic (MLC) capacitors to high-voltage electrical fast transients (EFTs). X7R and NP0 MLC capacitors with a 50 V voltage rating and 0603 package size were tested. X7R capacitors often failed during a spike in the voltage, but exhibited no obvious degradation in the measured insulation resistance at low voltages immediately after the failure. NP0 capacitors usually failed by suddenly shorting and maintaining the short after the failure. With the application of additional voltage spikes, some X7R capacitors exhibited a full recovery in terms of the measured resistance, returning to their initial state. The resistance of an X7R capacitor damaged by an EFT event is a function of the applied voltage. The terminal impedance can be modeled as two diodes in parallel.

Intelligent process monitoring of multilayer ceramic actuators using high-temperature optical fiber displacement sensors

A technique that uses embedded or attached high temperature optical fiber sensors is demonstrated for the intelligent processing of multilayer ceramic actuator elements. Presented are the results of the fiber optic strain sensor used to monitor internal displacements associated with the burnout of organic binders from a green actuator sample. Also presented is the method of operation of the low-finesse Fabry-Perot interferometric sensor, and post processing results obtained using the same type of sensor for tracking actuator performance and hysterisis.