Self-Lubrication of Hot YSZ-Ag-Mo Nanocomposite Coatings

An experimental study has been performed to learn about the physical and chemical mechanisms of self-lubrication of coatings that comprise nanostructured composites of yttria-stabilized zirconia (YSZ), silver, and molybdenum. These and other YSZ-based nanocomposite coatings have received increasing attention in recent years because they offer a combination of hardness, toughness, resistance to wear, and low-friction C properties that make them attractive for reducing wear and friction and increasing the lifetimes of hot, sliding components of mechanical systems. In addition to the excellent mechanical and thermal stability of the basic YSZ ceramic material, the nanocomposite structures of these coatings, consisting of combinations of amorphous and crystalline phases, provide a “chameleon” surface adaptation, in which different phases turn into lubricants in response to different test environments, contact loads, sliding speeds, and temperatures. Moreover, proper sizing of nanocrystalline grains can restrict crack sizes and create large volumes of grain boundaries, thereby increasing the toughness and contact-load-bearing capabilities of these coatings.

Posted in: Briefs, Materials, Lubricants, Coatings Colorants and Finishes, Composite materials, Nanomaterials, Wear

Hybrid Three-Axis Vibration Reducers

Hybrid (passive/active) devices have been developed to reduce the magnitudes of possibly threedimensional vibrations coupled from vibrating equipment on platforms to bases that support the platforms. These hybrid devices are three-axis generalizations of singleaxis hybrid vibration reducers developed and reported previously. Each hybrid device includes rubber passive vibration-isolator pads, piezoelectric actuators, optional piezoelectric force sensors, and accelerometers. Each device operates in conjunction with a computer and control-and-actuation circuitry, which process accelerometer readings using feedforward and/or feedback control laws to excite the piezoelectric actuators with signals having amplitudes and phases chosen to minimize acceleration of the base.

Posted in: Briefs, Mechanical Components, Vibration

Some Advances in Reducing Drag and Suppressing Convection

Theoretical and computational research has yielded some advances in the art of designing active feedforward and feedback controllers to suppress thermal convection and reduce drag (by suppressing turbulence) in boundary-layer flows. The advances include (1) improved means for designing reduced-order (and, hence, computationally more efficient) controllers and (2) discovery of a previously unknown phenomenon that could be exploited for feedforward control to reduce drag.

Posted in: Briefs, Mechanical Components, Electronic control systems, Drag

Autonomous Vehicles Would Learn by Mimicking Human Drivers

A program initiated by the Defense Advanced Research Projects Agency (DARPA) and now also pursued by other agencies called “Learning Applied to Ground Robots” (LAGR), is developing control algorithms that would enable a robotic land vehicle, robotic underwater crawler, or other similar autonomous mobile robot to traverse terrain safely. Among the algorithms needed are navigation algorithms for finding and then following a safe path across terrain from a starting or current position to a destination.

Posted in: Briefs, Information Technology, Vehicle drivers, Robotics, Autonomous vehicles

Advances in Algorithms for CFD and Finite-Element Simulation

A program of research and development has resulted in some advances in algorithms for computational fluid dynamics (CFD), finite-element simulation of solid objects undergoing large deformations, and some related topics. The main advances are summarized as follows:

Posted in: Briefs, Information Technology, Computational fluid dynamics, Finite element analysis

Shape-Based Recognition of 3D Objects in 2D Images

An object-recognition algorithm analyzes data from two-dimensional (2D) images to locate and identify possibly complexly shaped three-dimensional (3D) objects in possibly highly cluttered scenes depicted in the images. More specifically, the algorithm implements a relatively simple, effective, and fast process for recognizing 2D objects that may be partly occluded and that have shapes that can be modeled by use of sets of line segments (see figure). Because the algorithm tolerates a fair amount of perspective distortion, it is also applicable to 3D objects represented by sets of viewpoint- dependent 2D models.

Posted in: Briefs, Information Technology, Mathematical models, Imaging

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 rpellecchia@hybricon.com, or visit http://info.hotims.com/10968-401.

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