A new class of simple, reliable, lightweight, low packaging volume and cost, self-deployable structures has been developed for use in space and commercial applications. This technology called "cold hibernated elastic memory" (CHEM) utilizes shape memory polymers (SMP) in open cellular (foam) structure or sandwich structures made of shape memory polymer foam cores and polymeric composite skins. Some of many potential CHEM space applications require a high precision deployment and surface accuracy during operation. However, a CHEM structure could be slightly distorted by the thermo-mechanical processing as well as by thermal space environment. Therefore, the sensor system is desirable to monitor and correct the potential surface imperfection.
During these studies, the surface control of CHEM smart structures was demonstrated using a Macro-Fiber Composite (MFC) actuator developed by the NASA LaRC and US Army ARL. The test results indicate that the MFC actuator performed well before and after processing cycles. It reduced some residue compressive strain that in turn corrected very small shape distortion after each processing cycle. The integrated precision strain gages were detecting only a small flat shape imperfection indicating a good recoverability of original shape of the CHEM test structure.
For certain classes of MEMS, implementation of closed loop feedback control and system model-based fault detection offer significant performance advantages. Such systems include those in safety critical applications and systems in which dynamic loads are anticipated. Detailed continuous knowledge of the positional state of the microstructure is needed in order for accurate system models to be developed and experimentally verified, control techniques to be effectively applied, and model based fault detection evaluated. Moreover, this positional state information must be fully decoupled from the microstructure voltage drive signal. This paper reviews the group's current efforts exploring the use of integrated optics to provide this MEMS state feedback information and the merits and challenges of its application for microstructure control and fault detection. Modeling and experimental results using a 1.3 micron wavelength coherent optical probe for optical state monitoring will be presented including work integrating the probe optics within a folded diffractive optical element coplanar with MEMS die. Use of this signal in system model parameter estimation and real-time position control of a lateral comb resonator stage will be demonstrated and the potential for application to MEMS model-based fault detection discussed.
During the last decade, research and development of microelectromechanical systems (MEMS) has shown a significant promise for a variety of commercial applications including automobile and medical purposes. For example, accelerometers are widely used for air bag in automobile and pressure sensors for various industrial applications. Some of the MEMS devices have potential to become the commercial- off-the-shelf (COTS) components. While high reliability applications including aerospace require much more sophisticated technology development, they would achieve significant cost savings if they could utilize COTS components in their systems. This paper reviews the current status of MEMS packaging technology from COTS to specific application provides lessons learned, and finally, identifies a need for a systematic approach for this purpose.
Conference Committee Involvement (1)
Reliability, Testing, and Characterization of MEMS/MOEMS II