New Product: Multiphase stepper controller
Tarih 29 Ocak 2008, 20:38. Yazan alpella.
Etiket:
new product: multiphase stepper controller
Three operation modes are available: Sensor mode, absolute position mode, and relative position mode. The unit is rated at 1.2 A/phase for unipolar stepper motors and 0.6 A/phase for bipolar motors. Input power is 24 Vdc with power consumption of 36 W. This single-axis integrated system provides 20,000 steps/rev microstepping resolution. An onboard potentiometer lets users easily adjust driver running currents. Up to 15 devices can be daisychained using the RS-485 communication protocol. Input/output interface functions include: Photocoupler inputs, point starting code bits, home search start, immediate stop and direction of rotation, current off, and an alarm output sensor interface option.
New Product: Linear rail system
Tarih 29 Ocak 2008, 20:38. Yazan alpella.
Etiket:
new product: linear rail system
The unit consists of a stationary base with a load-bearing carriage that travels along a customextruded wear-resistant aluminum rail. The system uses either a Size 17 hybrid external linear actuator or a Size 17 hybrid double-stack external linear actuator integrated into the slide for a complete single-axis positioning system. The system can come with various leads and shaft-end configurations to accommodate any source of rotary power. The system offers control of slide bearing play with a self-adjusting linear bearing. Full-length slots are accommodated using integrated T-slots. Four or six screws attach loads to the compact moving carriage. For applications requiring extreme control, the unit can be used with high-precision antibacklash nuts.
New Product: Motion-control chips
Tarih 29 Ocak 2008, 20:37. Yazan alpella.
Etiket:
new product: motion-control chips
The processors can be used in one, two, three, and four-axis configurations to control any combination of motors. The chips feature programmable PID filters with velocity and acceleration feedforward, 32-bit position error, 50-μsec loop time, and four selectable profile modes, including S-curve, trapezoidal, velocity contouring, and electronic gearing.
The chips are driven by a host microprocessor using a CANbus 2.0B, 8, or 16-bit parallel bus, or an asynchronous serial port. Analog inputs include eight 10-bit inputs for parameters such as position, velocity, and acceleration to generate corresponding trajectories. The chips accept feedback from incremental encoders at 10 megacounts/ sec or from an absolute encoder or resolver at 160 megacounts/ sec.
New Product: Brushless ac servomotors
Tarih 29 Ocak 2008, 20:36. Yazan alpella.
Etiket:
new product: brushless ac servomotors
These highperformance, low-maintenance alternatives to stepper motors and dc servomotors come in either 40 or 60 mm square frame sizes, with options of one or two winding stacks, to provide continuous stall torque ratings of 1.4 to 11.24 lb-in. (0.16 to 1.27 Nm), and 4.25 to 33.63 lb-in (0.48 to 3.8 Nm) peak torques. The smallest one-stack motor measures 1.6 2.32 in. long, and weighs just 0.88 lb. The motor's power and feedback connections are via long flying leads. Motors can be specified with a resolver or 2000 PPR encoder fitted for positional feedback.
New Product: Embedded PLC
Tarih 29 Ocak 2008, 20:36. Yazan alpella.
Etiket:
new product: embedded plc
The unit is easy to install with integrated controller for mounting directly onto the machine. Features include IP65/67 protection; 10 to 100-mbps data-transfer rate in unlimited distances; e-mail, OPC, and Web-server capability; 512 in/512 out modular design with analog and digital I/O; 250 kbytes of program memory at 10 bytes/instruction; 1 to 2 msec per 1k instructions; and a graphical programming tool in statement list and ladder. The controller can be used in conjunction with a fieldbus node as a preprocessor to increase reaction time of the controlled system.
FE Update: How to clean up dirty CAD models
Tarih 29 Ocak 2008, 20:35. Yazan alpella.
Etiket:
fe update: how to clean up dirty cad models
Stephen Ferguson
Senior Consultant
Engineer
CD-adapco
Melville, N.Y.
Edited by Leslie Gordon
Although better translators and CADembedded CAE has smoothed out the route from model to solution, there is still a significant group of problems in which geometries are difficult to mesh. Estimates from the automotive industry suggest that as much as 80% of a typical CAE simulation goes to generating the computational model, with most of that time spent in surface preparation and repair.
A good example of dirty CAD is a collection of parts, such as automotive underhood components, that must be combined into a single surface before building a computational mesh suitable for analysis. Individual components might not fit together perfectly, with volumes that overlap or surfaces that interfere with each other. Another example is a fully detailed CAD part that requires defeaturing. Yet another example is a part assembly configured for manufacture. It contains gaps, likely to prevent meshing, where welds, screws, rivets, and the like are to be placed.
Shrink-wrapped CAD
To help solve the problem of
dirty CAD, “shrink-wrapping”
tools — such as our Surface Wrapper
which works inside our analysis software — reduce the time
it takes to get simulation results,
while producing more accurate
results. That’s because shrinkwrapped
models do not need geometric
simplification for meshing,
so that, if required, they can represent
the full complexity of component
geometry. However, when
model complexity is greater than
required for simulation (for example,
rivets on an aircraft wing), the
surface wrapper can also be used to
remove extraneous features.
The wrapper works for FEA, CFD, crash, or any kind of analysis where a high-quality triangulated surface is necessary for a simulation- ready mesh. From a user’s point of view, surface wrapping is automatic. The user first imports a CAD geometry, sets a representative “base-size” that determines the level of feature resolution in the final surface, and presses the “surface-wrap” button. The surface wrapper always generates a closed manifold or watertight surface.
Behind the scenes, the surface wrapper works by shrink wrapping a high-quality triangulated surface mesh onto the geometry, closing holes in it, and joining disconnected and overlapping surfaces. The wrapper quickly calculates the wetted surface of the geometry (the total of all the object’s surfaces that interact with the surrounding material, for example, air), discarding surfaces outside the calculation-domain to eliminate unnecessary detail.
Users can specify the level of resolution surface-by-surface, or use volume regions to specify larger areas of refinement. All size specifications are relative to the base size so wrapped surface can be fine-tuned by just altering a single parameter. Importantly, the surface wrapper respects the fidelity of the original CAD. Unlike other technologies, it accounts for sharp edges and corners of the original model, as well as for any other “feature curves” the user prescribes.
The time it takes to surface wrap depends on geometry complexity, surface refinement, and computing power available. A structure such as an offshore oil platform or automotive underhood can usually be wrapped in an hour. In most cases, surface wrapping takes just a few minutes using a desktop PC.
Joining a mannequin
to a racing bicycle
The surface wrapper recently
gave Felt Racing, a manufacturer of
high-end racing bicycles in Irvine, Calif., an edge in developing a new
UCI-legal, aerodynamic carbonfiber
bicycle. The company used
CFD simulation to determine the
most aerodynamically efficient
designs, testing only the best in a
wind tunnel. Although the company
had CAD data for the frame
and most of the components, it
used a third-party mannequin to
represent the rider. The rider had
to be joined to the frame before analysis. The company used the
surface wrapper instead of joining
the models manually, a process
that would have entailed many
hours of intensive manual surface
stitching. The company also used
the wrapper on the bicycle’s geartrain
components.
Vantage Point: The ethanol industry wants your sympathy
Tarih 29 Ocak 2008, 20:35. Yazan alpella.
Etiket:
vantage point: the ethanol industry wants your sympathy
Institute for Energy Research
Houston, Tex.
Edited by Kenneth Korane
Their rhetoric begs lawmakers to create an artificial market for ethanol and condemns anyone who speaks about its shortcomings as part of a “coordinated offensive of mistruths.” These statements undermine the effort to have a serious debate about the right way to diversify our energy sources and increase America’s energy security.
Despite accusations of an insidious campaign by the fossil-fuels industry against biofuels, there are a myriad of legitimate concerns about ethanol. These include, but are not limited to, ethanol’s effect on food prices, its huge water demands, and the ability to replace substantial amounts of oil.
The U.S. Energy Information Administration believes the practical limit for domestic ethanol production is about 13.8 billion gallons/year by 2030, or about 3% of America’s current oil consumption on an oil-equivalent basis. That’s hardly enough to provide “energy security.” Then there’s the promise of cellulosic ethanol as the solution to all our problems. For years, ethanol boosters have been claiming they will soon be producing vast quantities of ethanol from sources such as wood chips, corn stover, and switch grass. But commercially viable cellulosic ethanol is akin to the tooth fairy: an entity that many believe in, but no one ever actually sees. Among the doubters: the Dept. of Agriculture, which recently reported that while cellulose-based fuels hold “some longer-term promise,” much research is needed to make the technology commercially economical. In short, there’s no reason to expect it to be a practical reality anytime soon.
What about greenhouse gases? Virtually all studies show that greenhouse gases associated with ethanol and gasoline are about the same once the entire life cycle of the two fuels are compared. Further, as more land is harnessed for corn production, less fertile soils will be brought into production, requiring more energy-intensive farming, primarily through increased use of fertilizers and irrigation. By reopening previously dormant land, we may be unwittingly emitting tons of carbon dioxide with simple land-use changes.
The Institute for Energy Research supports energy diversity, tapping into the most efficient traditional, alternative, and renewable sources capable of sustaining themselves in a free market. Propping up inefficient producers with endless subsidies and mandating production of biofuels will not increase our energy security, and will likely produce a host of negative unintended consequences.
These are legitimate concerns that require serious thought before Congress mandates the use of billions of gallons of renewable fuels. The ethanol industry has been getting supersized subsidies for more than two decades. We should be looking to innovators and entrepreneurs to develop the next great technological breakthroughs in energy — not to lobbyists seeking more handouts in Washington.
Sensor Sense: Detecting reflective targets
Tarih 29 Ocak 2008, 20:34. Yazan alpella.
Etiket:
sensor sense: detecting reflective targets
Edited by Robert Repas
The reflective properties of plastic make it a notorious offender in this regard. The problem even extends to those objects covered in shrink wrap.
Polarizing filters help block false readings from shiny objects. Polarized retroflective sensors transmit light along one polarization axis. The light is then reflected back to the sensor from a corner-cube reflector.
Corner-cube reflectors have two distinct reflective properties. First, light always reflects back to the source regardless of the angle at which it enters the reflector. Second, it rotates polarized light 90° due to multiple reflections inside the reflector. The receiver’s polarizing filter aligns with the polarization of the reflected light.
Light reflected from glossy or highly reflective surfaces keeps the same axis of polarization. Without the 90° rotation of the cornercube reflector, the light is blocked by the receiver’s polarizing filter and the sensor signals that the target has passed.
However, some shrinkwrapped products still create problems because plastic has depolarization properties. While the amount of light reflected is not as efficient as a corner-cube reflector, at short distances a sensor can be tricked into thinking it sees the reflector. The result is a false reading. The likelihood of this problem grows exponentially when the plastic is layered, or if moisture is present in the shrink wrap.
This problem is addressed by using retroreflective sensors with foreground suppression. Optical apertures added to the transmitter and receiver elements tighten the light spot so the receiver detects only light reflected at the proper angle and axis rotation. This creates an area in front of the sensor that mechanically blocks any false readings to ensure error-free detection of highly reflective, depolarizing targets.
Industrial Design: Great application, but the product went nowhere
Tarih 29 Ocak 2008, 20:34. Yazan alpella.
Etiket:
but the product went nowhere, ındustrial design: great application
In this and future columns, I hope to educate and entertain you with war stories about industrial design gone bad and lessons learned. I also hope to provide useful ideas about design methods and approaches, as well as tips on implementing facets of industrial design.
Many companies develop innovative and technically correct product concepts. But, unfortunately, their products often fail from a lack of up-front homework. For example, years ago, a military contractor purchased a major player in the North American appliance-manufacturing industry. The company then developed a product called the Radar Range. It was a great application of advanced microwave technology. However, the product bombed because the company didn’t find and research a target market. Simply launching an excellent product doesn’t mean it will sell.
Doing things right from the start would have made the microwave’s success more likely. Instead, it ended up as just another number in a parts catalog. Lessons learned: find the target market, then identify what the product really does. Discover who makes the purchasing decisions, whether in a corporation, medical facility, or household.
An initial investment in industrial design can also raise the bottom line. That’s because designers ask countless probing questions to find out user needs and desires. A design firm can sometimes even suggest an innovation or another new market.
Though it may seem obvious, make sure marketing, engineering, design, and manufacturing meet together at project start. Each of these parties represent an ideal based on their profession, so it’s helpful for everyone to brainstorm without prejudice and express different ideas. The organic nature of this process often leads to innovation at its best, while helping eliminate expensive mistakes early on.
Next month, we’ll talk more about research and whether qualitative or quantitative research better specifies products.
Leland Teschler's Editorial: Why you can't always believe published research
Tarih 29 Ocak 2008, 20:33. Yazan alpella.
Etiket:
leland teschler's editorial: why you can't always believe published research
That’s the premise put forth by John P.A. Ioannidis, a medical researcher in Greece and adjunct professor at Tufts University School of Medicine. Ioannidis has modeled what can happen when unconscious biases creep into hypothesis testing. The field he had in mind was medical research, but others commenting on his work see parallels in areas ranging from brain mapping to parapsychology.
Some of Ioannidis’ findings sound like common sense about relationships claimed to be statistically significant. For example, studies with small sample sizes are less likely to yield correct results, as are studies of observable effects that are relatively small. And studies confirming consequences for which there is already a lot of solid evidence are probably valid.
But some problems are not as obvious. For example, too much flexibility in defining or analyzing outcomes can potentially transform negative results into positive ones. And it’s a good idea to question graded scales that researchers invent themselves. Of course, fuzzy definitions are less of an issue where the outcome is inarguable (such as death).
There are similar difficulties in new fields where analysis techniques are still being hammered out. Researchers can be tempted to report only their “best” results rather than a sea of data that is inconclusive. Ioannidis says there’s evidence that researchers manipulate outcomes and only report them selectively even in randomized trials.
Two of Ioannidis’ conclusions are interesting because they have implications beyond medicine. He says the greater the financial interests and prejudices in a scientific field, the less likely research findings are true. In the same regard, hot fields chased by numerous scientific teams are less likely to yield correct research findings.
His explanation for these effects is that prestigious investigators can have their own biases that prejudice their actions. For example, they can have financial or other interests that may lead them to shoot down peer reviews of findings that refute their own. And there can be a bandwagon effect when many teams of investigators pursue the same field. The imperative is to publish ahead of the competition, with a priority put on disseminating the most impressive “positive” results. So researchers can be predisposed to confirm the initial idea rather than to find the truth.
Clearly, hot fields are not confined just to medical research. Two other areas that immediately come to mind are global warming and alternative energy. Cheerleaders on both sides of these issues tend to haul out peer-reviewed research findings and wave them at each other as though warding off vampires with a crucifix.
Those tempted to use peer-reviewed research this way would do well to realize the scientific ground on which they are standing may not be as solid as they think. As Ioannidis has said, “It is impossible to know with 100% certainty what the truth is in any research question.”
