Integration & Collaboration for Ultimate Mechanical Systems

Feb. 6, 2008
While the fogginess around mechatronics may not have dissipated entirely, one thing is increasingly clear: as a conceptual schema for design, mechatronics continues to become more visible—and its importance can only grow over the next few years.
The word “mechatronics” came to life in 1969 at Yaskawa Electric Corp., a Japan-based manufacturer of a broad range of products for motion control, robotics and systems engineering. Yaskawa applied for a registered trademark for the term in 1970, then in 1987 relinquished the trademark, freeing it to become an industry-wide term. Mechatronics is an engineering design concept or domain—some describe it as a culture—that merges all of the engineering involved in “mechanics” (or mechanisms) with the engineering in “electronics.” It is machines + controls. It delves into all the overlaps among machines, computers, controls and electronics.Actually, as it turns out, almost anything could be simpler. The disciplines that go into mechatronics are rife with interactions and complexities. On top of this, new strategies, materials and technologies continue to bring new concepts and products to each domain, adding to the complexity. And the domains subsumed by mechatronics are many. In addition to mechanics, machine design and electronics (and their contributory science and engineering, such as thermodynamics, statics and dynamics, and solid-state circuitry), an integrated mechatronics approach can require contributions from any or all of: Control theory Computer science, including programming Digital signal processing (DSP) and communications Robotics Engineering analysis And, of course, mathematics, specifically mathematical modeling.
Mechatronics can be conceptual, a star to steer by or a body of actions that produce an overlay on an existing roadmap. That is, it can be applied at any point in the design process, from conceptualization to design review stages occurring late in development—even to the point of retrofitting to existing machinery and mechanical systems. True mechatronics practitioners, however, are quick to point out that only by beginning with an integrated approach can all benefits be realized.
Advantages go to machine function—and the bottom line. The potential benefits of using integrated mechatronics design include optimization plus optimized energy consumption and deeper exploitation of component capabilities—in other words, more avenues for milking every possible attribute of materials, motors, machines and controls. In addition, such designs tend to have fewer performance tradeoffs in cost engineering—in other words, the mechatronics approach allows more possibilities for acceptable or even increased functionality, accuracy and/or reliability at lower cost.“Ultimately, the benefits go right to the bottom line,” says mechatronics evangelist Kevin Craig, professor, Mechanical Engineering, at Marquette University, in Milwaukee. “Take Procter & Gamble. Here is one group that has a deep realization of the strengths in mechatronics. Engineers there concentrate on production cost savings that are possible by building highly-tuned, proprietary production equipment. The company is realizing millions of dollars in savings—and is capable of building new, desirable features into products—because its engineering group can design to specific capabilities and efficiencies, and solve problems before machines are actually built.”Favorable trends The trends are in favor of integrated, collaborative mechatronics approaches. First, engineering continues to advance, and almost any engineering advance can be seen as contributing to the growing need to adopt mechatronics. For example, centuries of knowledge and measurements in metals have been joined by decades of knowledge about newer engineered materials and composites. Newer materials usually can be cheaper, if for no other reason than they can be produced at net or near-net shape, eliminating manufacturing operations. But every material offers both strengths and tradeoffs, and a mechatronics approach helps maximize the positives and better accommodate differing stiffness factors or differing elasticity.Progress in motor design—especially servo motors—is now continuous. New products with finer and finer resolution and increased application flexibility enter the market each month. There is a progression of ever-smaller motors with ever-greater power and efficiency. Every element of motion and every element of power transmission have seen advances.Finally, and perhaps most importantly, controls continue to gain in intelligence, with chip logic and programming interfaces capable of directing mechanisms to do nearly anything a designer can imagine. In addition, controls and processors have moved farther and farther away from the central cabinet, to the point where they now can mount directly on the components they control. Operator interfaces similarly show increased sophistication.
Understand the machine
Razvan Panaitescu, manager, Department of Mechatronics, Siemens Energy & Automation Inc., Alpharetta, Ga., says, “The complexity of design today overwhelms any single methodology.” The team of which he is a member applies mechatronics to customers’ applications using his company’s motion equipment, controllers and automation products. The group’s charter is to provide high-level, consultative input into a broad range of machine designs.While no single path provides answers, he says, “We concentrate on value-added improvements. To do that, we have to understand as much as possible about the functionality and objectives of the machine—that is, we make sure we understand the real design specifications. From there, we model, and then we attach the intelligence, meaning help program the drivers and forces that will achieve the needed functionality.“This gives us the skeleton, so to speak,” he explains. “We then apply the muscles and brains, again using off-line simulation and modeling as much as possible. It’s easy to say that a given motor, for example, is correctly sized. But it takes much more to achieve dynamics that a given functionality demands—the speeds, the accuracies. These all rely on controllers to correct oscillations, irregularities, backlashes and other sources of noise. Of course, it helps that we are thoroughly knowledgeable about all the features of our controllers and we know how far we can take each one.”The last step involves virtual machine operation. “We can come very close to an accurate picture of the final machine’s performance without spending money for prototyping,” Panaitescu says. “For example, we can see how much oscillation is involved, or whether a given motion can be done in 500 milliseconds or less. Better than that, we can explain why a given function is possible, or if not, why not—the structure will bend, or forces are positioned wrong, that sort of thing. The result is confidence in a given design, a knowledge that it will meet or exceed requirements.” “It’s critical to understand that the design of mechanical systems is now a multidisciplinary effort,” says Marquette’s Craig. “It cannot be effectively done serially or sequentially.” Craig is one who does not see post-design application of mechatronics as worthwhile. “It must be integrated and collaborative from the start. This kind of approach is always challenging, and it is becoming more so with the trend to outsource. A machine made up of engineered components assembled from multiple vendors means that groups of engineers, each group working in its own culture, must correlate and understand the decisions of all the other groups,” he adds.Open collaboration Craig argues for an open collaboration from the initial moments of design. “I was most impressed at a Procter & Gamble workshop, where there were ten engineers and ten engineering managers,” he says. “That gave me a powerful message—that management buys into mechatronics. It told me that managers, who haven’t done engineering for years, are less concerned about revealing what they might have forgotten or where young engineers might outstrip them, than about the common purpose. This kind of approach is cultural, and it’s an attitude that says that machine performance is the goal.”Craig emphasizes collaboration and integration. “A major role of the mechatronics engineer is that of bridging—closing communication gaps between more specialized colleagues to ensure that objectives are met. And you have to follow the complexity. Complexity has been transferred from the mechanical world to electronics and computer and control software domains,” he explains.As mechanical engineering design began its journey toward software complexity, a great number of engineering tools emerged. Of course, algebra, trigonometry, analytic geometry and calculus have to be on this list, but as the number of calculations increases, along with the complexities of the underlying physics and science, software is increasingly filling the toolbox. What was computer-aided drafting in the mid-20th Century has evolved into computer-aided design (CAD), and CAD has been translated from merely a set of screen representations of paper drawings into a fully computerized toolbox for physical design modeling. Volume, mass, center of gravity and basic kinetics came early; more recent is relatively seamless integration of finite element analysis, collision detection, behavioral modeling, fluid dynamics and much more.hree computer trends have been enablers in this evolution. On the software side, engineering packages have moved from proprietary coding to systems that are, if not open, at least fitted out with an open application programming interface (API), making it easier to latch two programs together. At the same time, vendor-neutral data types have evolved that ease the processes by which users import and export modeling data between applications. Finally, computer hardware has become so powerful that a few thousand dollars now brings you a system capable of billions of calculations in the time the company coffee machine can deliver a latte.Singing at the wedding In the mechatronics world, however, the relatively rich physical modeling capabilities of CAD are not enough. In the modeling phase at Siemens, for example, Panaitescu’s group first studies any available CAD and dynamic models, as well as any analysis done up to the point of turnover to the team. “We try to sing at the wedding without being a musician,” as he puts it—in other words, assimilate as quickly as possible the design strategies already applied to a given project. The group then applies tools designed to bring control and software requirements into sharp relief. These include lumped mass studies, 3D multi-body modeling techniques and highly sophisticated 2D and 3D finite element analysis.The process involves simulations that measure every functional element. “Our goal is to understand the new machine from its very basic components to the complex ways that everything works together,” Panaitescu explains. It involves using the tools correctly—and interpreting them correctly. It’s forensic engineering that delineates what the machine does. Better than that, mechatronics allows us to see and communicate exactly how to improve it.”Craig’s set of tools is different in its specifics, but the underlying approach is similar. SolidWorks provides the CAD environment, while National Instruments’ LabView and MathWorks MATLAB provide the advanced modeling packages. “Mechatronics is part of our curriculum from the start,” he says. “There’s no value in making it an overlay in the senior year. We try to balance real-world needs with technologies that can be mastered in four college years. And we introduce the software in the freshman year and emphasize the need to explore their use with every appropriate engineering problem.”Craig draws a distinction between becoming, say, a CAD operator and using the tool for engineering. “We don’t want to train students to be tool users—we want to allow them to become masters, knowing when to use the tools and for what. We don’t believe in ‘freshman tools.’ We give them extremely powerful packages to use over the next four years.”The componentsThe final part of the mechatronics picture is the trend toward mechatronics-enabled components, or more specifically, machine and automation components with the following characteristics: Integrated or (if separate) matched controllers/drivers, allowing maximum optimization and response times Standards-based electronics and software/firmware, enabling easy (or at least easier) integration with standards-based components from other suppliers Control and/or functional design with appropriate speed and responsiveness—in other words, designs that are flexible enough to provide what is required A mechatronics-savvy supplier.
Of these, perhaps the most important is the last. “Savvy” means supportive, with dedicated mechatronics design resources that can be applied to your needs. The Siemens group, for example, offers R&D at a high project level. Other suppliers, such as Bosch Rexroth, provide specific help. For example, the Bosch Rexroth Linear Motion and Assembly Technologies group, in Hoffman Estates, Ill., helps end-users integrate that company’s components into systems.
“Our charter is to blend our core products into a solution for both distributors and customers,” says Richard Vaughn, robotics product engineer. “We’ll bring together mechanical actuators, servo motors, end-effectors, ball screws—anything that combines to deliver a given need.”
The approach could be seen as a mixed-mode design effort, with components providing the impetus from the bottom up, and customer requirements driving design from the top down. “Our methodology begins with what we call LOSTPED,” Vaughn says. “That is, our beginning point is the customer’s mechanical specifications, specifically load, orientation—for example, whether vertical or horizontal—speed, travel or overall length of motion, positional accuracy and repeatability requirements, environment or working conditions, and duty cycle.”From this basis, Vaughn’s group then works with the customer to flesh out control strategies. “And we work collaboratively with our internal divisions for servo, controls and pneumatics optimization,” he says. “The key is to keep an open mind when looking at solutions,” Vaughn says. “Almost any given problem can be resolved with the right sort of motion combined with the right level of control.”The Domains of Mechatronics
The elements of design that a mechatronics approach can help solve or optimize.
Motion Variables
• Position
• Speed
• Acceleration
• Jerk (acceleration change rates)
• Torque.
Application conditions• Stiffness/rigidity
• Resonance/natural frequencies
• Process forces
• Disturbances/induced excitation
• Cross-coupling.
Optimization • Stability
• Responsiveness
• Oscillation
• Following error
• Chatter, noise, ringing
• Tool/material reliability.
Source: Department of Mechatronics, Siemens Energy & Automation Inc.

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