Distributed Control Standard Connects Industry Regardless of Bus

In the early days of modern automation, the use of microprocessor technology addressed the need for fast and efficient configuration of control logics through graphical methods that mimic the hardwired relay logics. Over the past 30 years, the automation community has put the emphasis on simplifying and standardizing the method of programming this new breed of controllers. From these efforts came the adoption of the IEC 61131-3 standard that specifies the programming languages for automation.

Posted in: Articles, Articles, Electronics & Computers, Architecture, Standardization, Automation

Bringing Modularity to MicroTCA

MicroTCA is a new specification that offers very high performance packed in a small form factor. The new specification is expected to be used in a wide variety of applications, including mil/aero, telecom edge, medical, enterprise and data, and scientific applications. However, there are so many possible configurations, it can be overwhelming. How can one develop various systems and offerings without starting from scratch — and the time to market, high costs, and implementation issues this brings? One solution is using modularity in MicroTCA designs. Prototyping and development of a new system enclosure design can be a time-consuming and costly process. Building upon a proven modular platform allows a wide range of design options with significantly reduced effort.

Posted in: Articles, Articles, Electronics & Computers, Design processes, Downsizing, Architecture, Systems engineering

Filtered Conduction Empowers Mil-Spec Desert Systems

As embedded computing systems become more powerful, so are the challenges to protect and cool the payload. In the past few years, we have seen the power of a single board increase in most cases to over 100W per slot. To further challenge the designers, these systems are being deployed in rugged environments with a push to use COTS (commercial off-the-shelf) products. Recently, liquid-cooled systems have been developed to combat these However, there are some challenges with liquid cooling that can make this technology prohibitive. For example, not all boards are available in conduction- cooled format, or there may not be an external chiller/pump available to implement the liquid approach. So how does a designer handle an environment where there is no liquid coolant available, ambient temperatures hover around 55°C, the enclosure has a payload of 500W, and the client wants the system to operate on numerous rugged platforms (ground vehicle, rotary wing, UAV, etc.)? Oh, and the enclosure has to be sealed to protect the COTS boards from the harsh environments and EMI concerns. And with all of this, there is a desire to monitor the temperatures/ health of the system to protect the expensive payloads.

Add Monitoring to ATR

One approach to this design challenge is to integrate an air-to-air heat exchanger into a standard ATR package with a monitoring system. We will look at this approach in a little more detail with the specifications as follows:

Top-load Enclosure COTS air-cooled payload dissipating up to 500W Ambient temperature up to 55°C Harsh environment to meet MILSTD- 810 EMI — Designed to meet MIL-STD 461 (CE101, CE102) Front-panel access to all power and I/O connectors An additional electronics package, dissipating more than 100 W, is mounted inside of the controlled environment of the enclosure. In addition to these requirements, there is a concern that the accumulation of fine dust particles on the boards would prevent proper cooling, and larger particles would cause abrasion of the boards and other electronic components.

Exterior Mechanical Design

The first challenge is providing a rugged outside housing for the payload. In this solution, we chose to go with an ATR-style (see Figure 1) form factor because it is a common platform that has had a proven record for many years. The other advantage to this style of form factor is that it will easily mount into many existing applications, and there are a number of readily available shock-isolated trays on the market that can help meet the rugged vibration environments. It is also important to find that optimal balance between the weight and ruggedness required. A designer could go with a brazing approach, but this typically adds unacceptable cost and lead time to the program. The more economical approach would be to go with a welded/bolted-together construction method. This still provides significant strength, but also reduces the weight, cost, and lead time. It is also very important to include a rugged military finish or paint on the outside surfaces to further protect the enclosure from the harsh environments. The paint for this solution was chosen for its UV reflective properties to reduce the heat load generated by external solar radiation. In addition to the structural integrity and resistance to the environments, serviceability plays a big factor in the final design. The air intake filters on this unit are important to get the air into the chassis, but just as important is the ability to remove these filters and service them in the field, eliminating costly depot maintenance time.

Internal Structure

The second challenge is the requirement that the internal air be isolated from the external environment. The COTS air-cooled cards are not robust against accumulation of airborne sand and dust, and must be protected against this environmental threat. In addition, many board sets can generate substantial EMI, which must not only be contained within the unit, but must also be prevented from interfering with sensitive components in the electronics package (see Figure 2). Directly beneath the card cage is a small volume approximately 1.5" high, which can be used for additional payload. This space is EMI-isolated by aluminum walls and a conductive plane on the backplane. Airflow into this space is provided by ventilation holes in the backplane on the pressurized side of the recirculation fan.

To meet the environmental isolation requirement, an air-to-air heat exchanger was designed to allow the unit to shed heat, while preventing interchange of internal and external air. In order to minimize total system volume, reduce weight, and increase structural stiffness of the chassis, the heat exchangers and exhaust air ductwork are used to form the side walls of the chassis. The third and probably most important challenge was cooling the payload (see Figure 3). Four fans are used to pull external air through the external side of the heat exchangers, while internal air is re-circulated through the inner air passages of the heat exchangers. Additional cooling is provided for the electronics package by applying four smaller fans to pull air across the electronics package heat sink. The heat exchanger is a dual-passage counter-flow design where the internal air flows in the opposite direction of the external air.

This heat exchanger design is built as a brazement of aluminum plates and folded fin stock used to increase the surface area available for heat transfer. The recirculating air fan and the four fans on the electronics package are uncontrolled, and run directly from the 28V DC nominal input power. The four exhaust fans are speed-controlled to reduce audible noise when full cooling capability is not required. When run at highest fan speed, enabling internal payload power dissipation of over 500W, the cooling system is able to maintain internal air temperatures low enough to operate the system up to 55°C ambient. Thermal modeling shows that the recirculating air exiting the heat exchanger is kept within 10°C of the ambient air temperature.

System Monitor

In RF Mil-Spec systems, system monitoring falls into five major categories: temperature monitoring, fan monitoring, voltage monitoring, remote access, and other options. Temperature monitoring is becoming more critical as the value of the payload continues to rise. To address this, strategically located thermistors feed temperature values to a system monitor. The monitor can then evaluate the temperatures and increase/decrease the fan speed as needed. If a specified temperature is reached, a warning can be sent, and more importantly, if a temperature level is reached, the system monitor can inhibit the power to the backplane, shutting down and protecting the boards. It is also important to monitor other functions such as the health of the fans or system voltages. If one of these should fail, the system could be jeopardized.

In addition to the basic monitoring functions, new system requirements are generated every day. As the cost of processing boards rises, users are more interested in alerts that may not require system shutdown, which is moving customers towards boards and systems that can self-monitor the performance of the electronics package in addition to environmental factors.

This article was written by Ryan Pellecchia, Senior Technical Application Engineer, at Hybricon Corp. in Ayer, MA. For more information, contact Mr. Pellecchia at, or visit

Posted in: Articles, Articles, Electronics & Computers, Design processes, Embedded software, Cooling, Military vehicles and equipment

Data-Centric Network Integration Takes Headaches Out of Avionic Upgrades

Avionics systems are becoming more powerful and more dependent upon data exchanged between instruments. These instruments and subsystems reside on a network and must share time-critical data to achieve their mission. For example, targeting systems require real-time input of aircraft speed and attitude, as well as position and velocity data of the target. At the same time, additional bandwidth is required for data from onboard systems, such as GPS, airspeed and directional gyro, flight control systems, and dozens of other instruments and subsystems. As a result, network traffic is high, and potential data interactions can be highly complex. This complexity makes real-time integration of the data from disparate instruments during operational missions a significant challenge. Furthermore, upgrades of avionics and software applications during the useful life of the airframe means that new subsystems must be seamlessly integrated with legacy subsystems. In other words, data paths, interactions, and integration are not fixed forever. Today, aircraft systems typically are constructed to provide point-to-point communications between instruments and control systems that require realtime data. This approach has a significant impact on the complexity of the system and its subsequent maintainability. If an instrument is upgraded or replaced, the interfaces between it and other directly connected devices have the potential to change, requiring significant recoding and retesting.

Posted in: Application Briefs, Application Briefs, Electronics & Computers, Architecture, Avionics

Simulations of Stall and Stall Control in Turbocompressors

Anumerical-simulation study of stall and stall control in radial and axial compressor stages of gas turbine engines has been performed. This and other similar studies are needed because even though the adverse consequences of stall are well known and rudimentary stall-warning and stall-control systems are in use, the scientific basis for predicting and mitigating stall is not yet established.

Posted in: Briefs, Mechanical Components, Simulation and modeling, Compressors, Gas turbines

Application of CFD to a Slender-Bodied, Finned Projectile

In an application of computational fluid dynamics (CFD), flow fields about a slender-bodied finned projectile and the resulting aerodynamic forces and moments on the projectile were computed. The size and shape of the projectile (a blunt-nosed, ogivecylinder body, 316.7 mm long, 23.5 mm in diameter, with four tail fins) are representative of a preliminary design of a future air-defense projectile. The computations are exemplary of those needed for predicting aerodynamic performances in order to optimize designs of advanced projectiles, missiles, and rockets in general.

Posted in: Briefs, Information Technology, Computational fluid dynamics, Missiles

Multi-Scale Model of Failure in a Composite Material

An adaptive concurrent multilevel computational model of failure in a heterogeneous-material structure has been developed. As used here, "concurrent" is a term of art characterizing a class of structural/material models that (1) incorporate submodels representing material substructures at different spatial scales from macroscopic to microscopic, (2) the equations of the various models are solved simultaneously, and (3) the solutions at the various scales are coupled. The present model applies, more specifically, to a unidirectionalfiber/ matrix composite material structure. The model can be used to simulate and analyze the initiation and growth of damage, starting from microstructural damage in the form of debonding at fiber/matrix interfaces.

Posted in: Briefs, Information Technology, Failure analysis, Simulation and modeling, Composite materials

Adaptive Quantum Design of Semiconductor Devices

The term "adaptive quantum design" denotes a methodology for systematically seeking robust, manufacturable designs of semiconductor devices — especially semiconductor optoelectronic devices having nanoscale or even atomic- scale features. This methodology has been developed to complement advances in fabrication capabilities that make it possible to tailor semiconductor devices ever more precisely, such that it likely will soon be possible to routinely control the positions of features as small as atoms and molecules within devices. Because the number of atom configurations that could, potentially, be fabricated is almost unimaginably large and quantum fluctuations and collective quantum phenomena become important at molecular and atomic scales, traditional design methods and traditional models of device physics based on classical physics and semiclassical approximations of quantum phenomena are not adequate for exploration of the vast space of design options.

Posted in: Briefs, Electronics & Computers, Design processes, Semiconductor devices

Real-Time Simulation and Semiautomated Design of Complex ICs

A project called “System on a Chip Real-Time Emulation” (SOCRE) was undertaken to develop and demonstrate a methodology of simulation of operation and semiautomated design of complex mixed-signal (analog/digital) integrated circuits (ICs). The methodology includes the use of a simulation engine (consisting of computer hardware and software) for real-time emulation of a designed IC, in conjunction with an automated design flow that enables automated or semiautomated synthesis of a final design and automated or semiautomated fabrication of the ICs of the designed IC without need for manual reentry of a description of the design.

Posted in: Briefs, Electronics & Computers, CAD / CAM / CAE, Integrated circuits, Test procedures

A Study of Two Ferrocene-Based Molecular Electronic Devices

Acomputational-simulation study of two ferrocene-based molecular electronic devices was performed as part of a continuing effort to develop a capability for ab initio design of metallocene-based electronic devices in general. In addition to the obvious technological advantage for realization of the potential of molecular electronic devices, such a capability would afford an economic advantage by enabling avoidance of the cost of synthesis of many organic molecules that subsequent testing would show to be unpromising for electronic-device applications.

Posted in: Briefs, Electronics & Computers, Simulation and modeling, Electronic equipment