Articles

Mechatronic System Integration and Design

While today’s multi-discipline mechatronic systems significantly outperform legacy systems, they are also much more complex by nature, requiring close cooperation between multiple design disciplines in order to have a chance of meeting schedule requirements and first-pass success. Mechatronic system designs must fluently integrate analog and digital hardware — along with the software that controls it — presenting daunting challenges for design teams, and requiring design processes to evolve to accommodate. What is Mechatronic Design? The growing trend toward mechatronic system design is driven by the same things that drive all technological advances: the demand for higher performance and lower costs. The word itself is a portmanteau of “Mechanics” and “Electronics.” As Figure 1 shows, mechatronic design includes a combination of (1) mechanical design elements (e.g., plant, actuators, thermal characteristics, hydraulics/fluids, and magnetics); (2) analog, digital, and mixed-signal electronics; (3) control systems; and (4) embedded software. The intersections in Figure 1 — (a) electromechanical sensors and actuators; (b) control circuits; and (c) digital microcontrollers — reveal the most common areas for interdisciplinary cooperation among mechanical, electrical, and software engineers. Best Mechatronic Design Practices Boston-based technology think tank, Aberdeen Group Inc., provided pivotal insight into the importance of incorporating the right design process and tools for mechatronic system design. In a seminal study, Aberdeen researchers used five key product development performance criteria to distinguish “Best in Class” companies, as related to mechatronic design. The results were fairly revealing (see table), and should be of significant interest within the extended design community. In the study, Best in Class companies proved to be twice as likely as “Laggards ” (worst in class companies) to achieve Revenue targets, twice as likely to hit Product Cost (manufacturing) targets, three times as likely to hit Product Launch Dates, twice as likely to attain Quality objectives, and twice as likely to control their Development Costs (R&D).1 The fact that the Best in Class companies performed better isn’t as noteworthy as the degree to which they performed better. Two to three times better on every variable invites the question, “How were they able to achieve these far superior results?” Aberdeen’s research revealed that Best in Class companies were: 2.8 times more likely than Laggards to carefully communicate design changes across disciplines. 3.2 times more likely than Laggards to allocate design requirements to specific systems, subsystems, and components. 7.2 times more likely than Laggards to digitally validate system behavior with the simulation of integrated mechanical, electrical, and software components. The remainder of this article will explore these “best in class” practices in further detail. Communicating and Allocating Design Requirements A mechanical engineer may be interested in dampening vibration by adding a stiffener. This, of course, would add mass and as a result, may impact how fast the control system ramps up motor speed, thus impacting size requirements on the motor as well as power requirements. The benefits of immediate, formal documentation of this design change enables concurrent, cross-discipline design. Effective partitioning of the multiple technologies present in a mechatronic system is another significant predictor of project success. Subsystem partitioning begins with a common-sense breakdown of the design, using Figure 1 as a highlevel framework. To the degree possible, separate out mechanical subsystems from electrical subsystems, and the same with controls and software. From there, subsystems can further be broken down into subcategories beneath the high-level distinctions, including, for example, digital, analog, and mixed-signal electronics; divisions in mechanical subsystems; and breaking out overlapping areas (e.g., sensors and actuators) as additional subsystems. Next, subsystems can be assigned to specific job functions and design groups, and input/output requirements can begin to be defined at the boundary crossings between subsystems.2 Figure 2 shows the partitioning process, moving from functional design through implementation. With this framework in place, the design and analysis can begin for each subsystem — later to be combined and analyzed as a complete system. Simulation and Virtual Prototyping In contrast to physical prototyping, virtual prototyping and system simulation allows a system to be tested as it is being designed, and provides access to its innermost workings at every phase of the design process (this is difficult or impossible with physical prototypes). Moreover, simulation provides for analysis of the impact of component tolerances on overall system performance, which is out of the question with physical prototypes. When employed early in the design process, simulation provides an environment in which a system can be tuned and optimized, and critical insights can be gained, even before components are available and before hardware can be built. After the basic design is locked down, simulation can again be em - ployed to verify intended system operation, varying parameters statistically in ways that would otherwise be impossible with physical prototypes. Subsystem and Component Modeling In order to create a model for a system, each subsystem and component in the real system needs to have a corresponding model. These models are then stitched together (as would be their physical counterparts) to create the overall system model. Using the Department of Defense-initiated VHDLAMS modeling standard (IEEE 1076.1), system integration can begin before physical hardware is available, including embedded software or any other domain that can be described using algebraic or differential equations. To be specific, VHDL-AMS allows expression of simultaneous, nonlinear differential and algebraic equations in any model; the model creator need only express the equations and let the simulator solve them in time or frequency domain. Domain knowledge from any engineering discipline can be encapsulated in reusable libraries that are accessible by any member of the design team. The art of creating these models, and knowing exactly what to model and why, are keys to successful simulation. Some modeling include: Which system-performance characteristics are critical, and which can be ignored without affecting results? Does a model already exist? Can an existing model be modified? What component data is available? Several software simulators exist for simulating mechatronic designs (such as SystemVision from Mentor Graphics). These simulators support VHDL-AMS, SPICE, and embedded C code in providing an environment in which mechanical, electrical, software, and systems engineers can collaborate using common models and a common modeling environment3. In conjunction with proper mechatronic system-design training, careful interdiscipline communication, and deliberate system partitioning, simulation technology can play a key role in mechatronic project success. This article was written by Bill Hargin, Director of Product Marketing, System-Level Engineering Division, Mentor Graphics Corporation, Wilsonville, OR. For more information, click here. References Aberdeen Group, System Design: New Product Development for Mechatronics, Boston, MA, January 2008. (www.aberdeen.com) Scott Cooper, Mentor Graphics Corp., Design Team Collaboration within a System Modeling and Analysis Environment, 2004. (www.mentor.com/systemvision) Ashenden, G. Peterson, D. Teegarden, The System Designer’s Guide to VHDL-AMS: Analog, Mixed-Signal and Mixed-Technology Modeling. San Francisco: Morgan Kaufman Publishers, September 2002. (www.mkp. com/vhdl-ams)

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Slip Clutches Solve Diverse Design Problems

Slip clutches are commonly used to protect against overloads, but they can solve many other problems as well. Their applications include increasing machine speeds, applying constant tension to webs or wires, indexing a mechanism, holding a hinged object in position, controlling torque on capping or assembly operations, and providing soft starts or cushioned stops.

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Taming Residual Bulk Image in CCDs

Residual bulk image (RBI) is a phenomenon observed in certain types of front side-illuminated charge-coupled devices (CCDs). A CCD is an electronic light sensor used in digital cameras. In simplest terms, the sensor exhibits a memory of prior exposures resulting in ghost images appearing in subsequent images. This deferred charge can cause a number of problems in cooled long-exposure scientific applications. At a minimum, the ghost images can create the illusion of a non-existent object (Figure 1, left). Equally serious, they can lead to significant errors in quantitative measurements required for photometric applications.

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Product Simplification: Rediscover a Whole New Game

By John Gilligan President Boothroyd Dewhurst, Inc. Wakefield, RI Product simplification is the discipline of merging the greatest performance functionality into the fewest number of parts using the most suitable and cost-effective materials and manufacturing processes. It is an engineering board game, in a way, answering questions about a design and seeing a Design for Manufacture and Assembly (DFMA) database respond with quantitative costs and reports. There is truth and mystery in confronting an analysis that says there are too many parts, shows the team where, and then launches everyone into the intimacy of trial-and-error engineering, collaboration, and fresh creation. It’s a game that companies would ideally play regularly, but tend to do most vigorously when innovation and efficiency are both in crisis. Cross-functional product development teams have discovered and rediscovered the phenomenon of product simplification in meeting door- die cost targets for their companies. Along the way, manufacturers learned that it is through the rigorous combination of design and process innovation that market desirability and engineering elegance are achieved in tandem. Yesterday’s innovative design ideas and process choices are today’s competitive standards. Snap fits and living hinge techniques became great tactics for innovation by Dell, HP, and Motorola. Beyond plastics, engineers made other daring moves from the DFMA game board. Medical companies embedded hydraulics and printed circuits into structural supports to avoid individual part costs, potential part failures, and added assembly labor. Dell and HP continued their design assault on unnecessary cables, harnesses, and separate electronic components, building new functionality onto circuit boards. Product simplification was helped, of course, by creative supply chains. Finally seeing an opportunity to advance new technology, suppliers showed their OEM partners how to use process breakthroughs to put answers on a sometimes blank work sheet. A designer’s habit, for example, of creating molded ribs for purely visual symmetry can add 30-40% to the manufacturing cost of a component. The expertise of both parties working in transparent collaboration with a cost analysis tool has unlocked significant savings. There are other catalysts for innovation as well. Motorola University in Asia teaches the integration of lean, Six Sigma, and DFMA to internal design teams, suppliers, and customers. They recognize the impact of product simplification on quality, performance, and profitability in electronic products. Recent benchmarks for cost reduction are impressive. Knowing that their ap - proach is a business, not just a technology strategy, engineers sit in redesign sessions with unit heads — even with presidents — and use a business score card to measure progress and institutionalize best practices. The benefits of product simplification are spread through every “touch phase” of a product’s travel — from the napkin sketch idea, through CAD, production, shipping, administration, service, and end-of-life disposal. Innovation — brought about through analytical costing and simplification of the complete pro duct, from initial design to final disposal — is the future. Wonderfully, the best industry innovators have already embraced a full understanding of the dynamic beauty of simplicity, but everyone can, and should, play this game. For more information on DFMA, click here.

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Transportation Category Winner

Movito Electric Scooter Tai Chiem Melbourne, Australia Movito is a scooter based on an electric inwheel motor, a hubless front wheel, and a modular base system. It is designed for traveling short distances in and around the city. One of the key technologies used to reduce harmful emissions is an in-wheel motor developed by Australia’s CSIRO. The design boasts 98% efficiency, and is lightweight with direct drive that eliminates drive train loss. It has a component weight of 6 kgs. The use of an inwheel motor has allowed for an overhaul of the scooter’s architecture, freeing up space and weight to allow for a more dynamic shape and form factor. Powered by Li-ion batteries stored in the central body, it is charged via a charging mat. Another key technology is the use of a hubless front wheel, offering greater precision when riding. Based on technology developed by Osmos, the orbital wheel’s steering pin is designed around a second large bearing in the hollow section of the circular runner. Movito features an integrated CPU and organic LED touchscreen, allowing the rider to customize the scooter to their personal preference, including connecting wirelessly to the Internet, accessing GPS, and an iPod dock. A modular base system allows multiple “bodies” to be attached to a common base. Alternate bodies can be attached to a single base, or two bases can be placed parallel with a larger body positioned on top, turning the scooter into a two-seat mini-car. The drive-by-wire technology eliminates mechanical linkages between the steering; instead, it’s controlled by a tritium controller. Comprised of lightweight materials, the main body is composed of a carbon fiber reinforced composite. This material is carried down to the base, which is made of carbon fiber reinforced plastic over a steel frame chassis, offering added strength and load-bearing capabilities. For more information, contact the inventor at tchi6@hotmail.com. Honorable Mentions Ellipse Sf-X Bicycle Florin Sacuiu Peoria, IL The Ellipse® Sf-X is an all-terrain bicycle with a front section concept that separates the steering system from the damping system. The suspension system is interconnected with the bicycle frame structure, lowering the center of gravity during braking, and eliminating the ability for the bicycle to roll over. The rear wheel is loaded during the braking process, so overall braking performance is improved and the rider can stop the bicycle in a shorter distance. All of its components, except the frame and front and rear forks, are current production bicycle components. Mountain Goat Aircraft Bill Montagne Montagne Aircraft LLC Palmer, AK The Mountain Goat aircraft features a wing that uses a modified NASA airfoil to enhance attached airflow, stall, and cruise speeds. The roll cage structure exceeds FAA standards for frontal and rollover crash protection. More cockpit room and seat belts for 300 mph reduce the possibility for injury. It also features load capability and an extremely wide center of gravity envelope. There is no center of gravity change from full fuel to empty, and flaps and flaperons are fully interchangeable. Wing assemblies and controls were designed for a six-seat aircraft so that both aircraft have interchangeable parts. Airflow reattaches after stall abruptly with little altitude loss. All wing controls and accessories are accessible during preflight inspection by lowering the flaps.

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Sustainable Technologies Category Winner

Efficient Air Conditioner Lindsay Meek Perth, Australia This design improves the energy efficiency of a residential air conditioner by replacing the traditional reciprocating compressor (bore and stroke) with a higher efficiency permanent magnet motor coupled to a scroll compressor. Recent advances in permanent magnet motors used in modern hybrid car electric drives and wind turbine generation have seen the incorporation of strong NdFeB magnets into the rotor, which greatly improves the motor efficiency. The compressor motor is then driven by a compact IGBT inverter stage with a motor controller, so motor current consumption can be optimized at the different operating speeds. The other improvement that can be made is to replace the traditional refrigerant expansion valve with a similar scroll expander turbine coupled to a second permanent magnet generator. The decompression of the refrigerant gas through the turbine on its way to the condenser allows some of the work used to compress the gas to be recovered and converted back into electrical energy. The generator is connected to a second compact IGBT inverter stage with a motor controller, and can be controlled in conjunction with the compressor motor controller to regulate the pressure and flow rate of the gas through the system. The two inverters are connected together via a common, high-voltage DC bus, so the electrical energy recovered from the decompression state can be reused by the compression stage, improving the overall efficiency of the refrigeration cycle. Finally, an AC-DC rectifier power supply is needed to provide the main work energy for the DC bus to keep the cycle operating. The above improvements should lower the power consumption by at least 30%. For more information, contact the inventor at lindsaymeek@hotmailcom. Honorable Mentions Coupled Water Tower/Wind Turbine Controller Andras Tanczos Helsinki, Finland A coupled water tower/wind turbine controller stores wind energy in the water towers of the drinking water network. At strong winds, the extra electrical energy generated by the wind turbine can be used to pump water into the water tower. When there is no wind, this energy can be released with a hydro-turbine, and the water goes back to the wells. The pump of the water tower and the hydro-turbine are used to control the water level in the reservoir. The electricity from the wind turbine is used for pumping the water or for supplying the electrical grid. The controller can also be installed on existing water towers and water tanks placed on top of buildings. Electromagnetic Rail Motor Tim Cormier Beavercreek, OH The Electromagnetic Rail Motor (ERM) can power anything from aircraft and cars, to artificial human limbs. The ERM is based on the modern rail gun. By taking the two rails and forming a ring, a continuous rotational force is created that is easily managed and controlled. The speed of rotation can be directly controlled by adjusting the voltage, similar to a gas pedal. Once the ERM powers up, the motor rotation will accelerate to its terminal speed. The blades act as both rotational shafts and as propeller blades to help cool the motor during extremely high speeds. The rail housing holds the assembly together and keeps the rails in place to counter the immense separation force.

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Safety & Security Category Winner

Electronic Fog, Frost, and Ice Prevention Technology Don Skomsky Integrity Engineering, Inc. West Chester, PA This electronic device prevents condensation, frost, and ice from forming on any surface. It predicts when fog, frost, and/or ice is about to form on a surface (windows, mirrors, lenses, visors, etc.), and prevents it from ever forming by eliminating the conditions that support it. It works equally well in hot or cold temperatures, in arid to extremely humid conditions, and even in the rain and under water. Applications for the device include windshields; ski, swimming, and safety goggles; HAZMAT, SCUBA, firefighter, and pilot masks; and motorcycle, racing, and astronaut helmet visors. Since it is entirely electronic, the device requires no sprays, wipes, fans, or any other user intervention. Because it is predictive and not reactive, it requires an extremely small amount of energy. There are no moving parts and nothing to wear out. In a sports goggle application (trademarked Zoggles™), the device is built into the goggle itself, resulting in a goggle that is lightweight, sleek, and stylish. When activated by a touch of a switch, the Smart-System electronics maintains Zoggles in “sleep mode,” conserving energy until such time that fog, frost, or ice is about to form. Immediately, Zoggles awakens, performs its prevention task, and resumes sleeping, until needed again at a later time. All energy is supplied by small rechargeable NiMH batteries, which power Zoggles for at least 8 hours of extremely active use in very cold temperatures. The device has been tested in numerous applications, the most rigorous being during the ascent of Mount Everest in 2006, with a summit of 29,029 feet. In specially prepared units, Zoggles protected the mountain climbers’ vision in the -35ºF, 60-MPH weather conditions without fogging, frosting, or icing. For more information, contact the inventor at IntegEngg@erols.com. Honorable Mentions Ten-Second Advance Deceleration Warning Device Fritz Braunberger Vision Works IP Corp. Sequim, WA StrobeWise™ provides an additional 1 to 10 seconds of warning time (over and above brake lights) to following vehicles, warning them of a slowing or stopping event. The system monitors vehicle speed 1,000 times per second and flashes a center-high-mounted amber strobe rearward upon deceleration detection. It continually flashes when the vehicle is stationary, mitigating stationary-vehicle rear-end collisions. The system mounts on the inside rear window or externally on rear-windowless trucks. It retrofits on nearly all vehicles made later than 1993. Emergency Drop in Water Recovery Preparation Unit Anna Epelbaum Management Services Co. Champaign, IL This device functions from solar energy and/or portable fuels such as butane and propane. The unit may be transported to any emergency site where it then begins to process water once set up with any water source within 35 feet. The device loads water from rivers, ponds, lakes, streets, or sewers, and then filters the water. It uses advanced ozone bubbles and ultraviolet radiation, as well as activated carbon, to repatriate the water into drinkable form. The water is then distributed in RFID-coded one-gallon bottles. The empty bottle may be returned to the machine for re-filling and re-sealing an unlimited number of times.

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