Passive motion control of pneumatically driven displacers in cryogenic coolers

The split cryogenic cooler with a remote cold finger offers many advantages for use in cooling of infrared systems. A pneumatic drive for the displacer in such coolers was adopted in many cryocooler designs. This concept can be significantly improved by causing the displacer to move sinusoidally rather than in an essentially square wave, as in most of the present models. The way this motion was achieved passively is described and its advantages outlined. Data of minicoolers using this concept are presented

Vibration Control of Linear Split Stirling Cryogenic Cooler for Airborne Infrared Application

Modern infrared imagers often rely on the split Stirling cryogenic coolers the linear compressors of which are the well-known sources of harmonic disturbance. The traditional method of their passive isolation fails to meet the restraints on the static and dynamic deflections which are originated by the combined action of the airborne g-loading and harsh random vibration

Streaming End-to-end Speech Recognition For Mobile Devices

End-to-end (E2E) models, which directly predict output character sequences given input speech, are good candidates for on-device speech recognition. E2E models, however, present numerous challenges: In order to be truly useful, such models must decode speech utterances in a streaming fashion, in real time; they must be robust to the long tail of use cases; they must be able to leverage user-specific context (e.g., contact lists); and above all, they must be extremely accurate. In this work, we describe our efforts at building an E2E speech recognizer using a recurrent neural network transducer. In experimental evaluations, we find that the proposed approach can outperform a conventional CTC-based model in terms of both latency and accuracy in a number of evaluation categories

Vibration Protection of Sensitive Components of Infrared Equipment in Harsh Environments

This article addresses the principles of optimal vibration protection of the internal sensitive components of infrared equipment from harsh environmental vibration. The authors have developed an approach to the design of external vibration isolators with properties to minimise the vibration-induced line-of-sight jitter which is caused by the relative deflection of the infrared sensor and the optic system, subject to strict constraints on the allowable sway space of the entire electro-optic package. In this approach, the package itself is used as the first-level vibration isolation stage relative to the internal highly responsive components

Compact Linear Split Stirling Cryogenic Cooler for High Temperature Infrared Imagers

Presented at the 16th International Cryocooler Conference, held May 17-20, 2008 in Atlanta, Georgia.Novel high-definition night vision imagers are being enabled by new high-temperature infrared detectors that operate at elevated temperatures ranging from 95K to 200K; these have performance indices comparable with those of their 77K predecessors. Recent technological progress towards industrial implementation of such detectors has motivated the development of microminiature split Stirling linear cryocoolers. These coolers have great potential to replace the traditionally used rotary integral Stirling coolers. Their known advantages are superior flexibility in system packaging, constant and high drive frequency, lower wideband vibration export, unsurpassed reliability, and aural stealth. Unfortunately, off-the-shelf available tactical linear coolers relying on flexural-bearing, contactless, dual-piston compressors are thus far oversized, overweight, overpowered, and overpriced as compared to their rotary competitors. The authors report on the successful development of the smallest in the range Ricor model K527 microminiature 1W at 95K split Stirling linear cryogenic cooler. This cooler relies on a single piston externally counterbalanced linear compressor, and was designed to provide cryogenic cooling to a wide range of forthcoming infrared imagers, particularly those where power consumption, compactness, vibration, aural noise, and ownership costs are of concer

Vibration control of linear split Stirling cryogenic cooler for airborne infrared application

Modern infrared imagers often rely on the split Stirling cryogenic coolers the linear compressors of which are the wellknown sources of harmonic disturbance. The traditional method of their passive isolation fails to meet the restraints on the static and dynamic deflections which are originated by the combined action of the airborne g-loading and harsh random vibration. The vibration protection system, which combines a stiff and heavily damped vibration isolator with tuned dynamic absorber, is studied and optimised for use in the design of an airborne infrared device. Such a design is aimed, primarily, at essential dynamic suppression of the harmonic force which is produced by the linear compressor and, secondarily, at minimisation of environmental vibration loads transmitted through the infrared device to the linear compressor. Experimental testing backed up the theoretical results