中英文文獻(xiàn)翻譯-什么是智能傳感器

1、 What is a smart sensorOne of the biggest advances in automation has been the development and spreadof smart sensors. But what exactly is a smart sensor? Experts from six sensormanufacturers define this term.A good working smart sensor definition comes from Tom Griffiths, productmanager, Honeywell I

2、ndustrial Measurement and Control. Smart sensors, he says,are sensors and instrument packages that are microprocessor driven and includefeatures such as communication capability and on-board diagnostics that provideinformation to a monitoring system and/or operator to increase operationalefficiency

3、and reduce maintenance costs.No failure to communicateThe benefit of the smart sensor, says Bill Black, controllers product managerat GE Fanuc Automation, is the wealth of information that can be gathered fromthe process to reduce downtime and improve quality. David Edeal, Temposonicsproduct manager

4、, MTS Sensors, expands on that: The basic premise of distributedintelligence, he says, is that complete knowledge of a system, subsystem, orcomponents state at the right place and time enables the ability to makeoptimal process control decisions.Adds John Keating, product marketing manager for the C

5、hecker machine vision unitat Cognex, For a (machine vision) sensor to really be smart, it should notrequire the user to understand machine vision.A smart sensor must communicate. At the most basic level, an intelligentsensor has the ability to communicate information beyond the basic feedbacksignals

6、 that are derived from its application. says Edeal. This can be a HARTsignal superimposed on a standard 4-20 mA process output, a bus system, or wireless arrangement. A growing factor in this area is IEEE 1451, a family ofsmart transducer interface standards intended to give plug-and-playfunctionali

7、ty to sensors from different makers.Diagnose, programSmart sensors can self-monitor for any aspect of their operation, includingphoto eye dirty, out of tolerance, or failed switch, says GE Fanucs Black.Add to this, says Helge Hornis, intelligent systems manager, Pepperl+Fuchs,coil monitoring functio

8、ns, target out of range, or target too close. It mayalso compensate for changes in operating conditions. A smart sensor, saysDan Armentrout, strategic creative director, Omron Electronics LLC, mustmonitor itself and its surroundings and then make a decision to compensate forthe changes automatically

9、 or alert someone for needed attention.Many smart sensors can be re-ranged in the field, offering settable parametersthat allow users to substitute several standard sensors, says Hornis. Forexample, typically sensors are ordered to be normally open (NO) or normallyclosed (NC). An intelligent sensor

10、can be configured to be either one of thesekinds.Intelligent sensors have numerous advantages. As the cost of embedded computingpower continues to decrease, smart devices will be used in more applications.Internal diagnostics alone can recover the investment quicklyby helping avoidcostly downtime.Se

11、nsors: Getting into Position As the saying goes, No matter where you go, there you are. Still, mostapplications require a bit more precision and repeatability than that, so heresadvice on how to select and locate position sensors.The article contains online extra material.Whats the right position se

12、nsor for a particular application? It depends onrequired precision, repeatability, speed, budget, connectivity, conditions, andlocation, among other factors. You can bet that taking the right measurementis the first step to closing the loop on any successful application.Sensor technologies that can

13、detect position are nearly as diverse asapplications in providing feedback for machine control andother uses. Spatialpossibilities are linear, area, rotational, and three-dimensional. In someapplications, theyre used in combination. Sensing elements are equally diverse.Ken Brey, technical director,

14、DMC Inc., a Chicago-based system integrator,outlined some the following position-sensing options.Think digitallyFor digital position feedback:Incremental encoders are supported by all motion controllers; come inrotary and linear varieties and in many resolutions; are simulated by manyother devices;

15、and require a homing process to reference the machine toa physical marker, and when power is turned off.Absolute encoders are natively supported by fewer motion controllers; canbe used by all controllers that have sufficient available digital inputs;report a complete position within their range (typ

16、ically one revolution);and do not require homing.Resolvers are more immune to high-level noise in welding applications; come standard on some larger motors; simulate incremental encoders whenused with appropriate servo amps; and can simulate absolute encoders withsome servo amps.Dual-encoder feedbac

17、k, generally under-used, is natively supported bymost motion controllers; uses one encoder attached to the motor and anotherattached directly to the load; and is beneficial when the mechanicalconnection between motor and load is flexible or can slip.Vision systems , used widely for inspection, can a

18、lso be used for positionfeedback. Such systems locate objects in multiple dimensions, typicallyX, Y, and rotation; frequently find parts on a conveyor; and are increasingin speed and simplicity.A metal rolling, stamping, and cut-off application provides an example ofdual-encoder feedback use, Brey s

19、ays. It required rapid and accurateindexingof material through a roll mill for a stamping process. The roll mill createsan inconsistent amount of material stretch and roller slip, Brey explains.By using the encoder on the outgoing material as position feedback and the motorresolver as velocity feedb

20、ack in a dual-loop configuration, the system was tunedstable and a single index move provided an accurate index length. It was muchfaster and more accurate than making a primary move, measuring the error, thenhaving to make a second correction move, he says.Creative, economicalSam Hammond, chief eng

21、ineer, Innoventor, a St. Louis, MO-area system integrator,suggests that the applications purpose should guide selection of positionsensors; measurements and feedback dont have to be complex. Creativeimplementations can provide simple, economical solutions, he says. For instance,for sequencing, proxi

22、mity sensors serve well in many instances. Recent sensor applications include the AGV mentioned in lead image and thefollowing.In a machine to apply the top seals to tea containers, proximity andthrough-beam sensors locate incoming packages. National Instrumentsvision system images are processed to

23、find location of a bar code on apre-applied label, and then give appropriate motor commands to achievethe desired position (rotation) setting to apply one of 125 label types.Two types of position sensors were used. One was a simple inductiveproximity sensor, used to monitor machine status to ensure

24、various motioncomponents were in the right position for motion to occur. The camera alsoserved as a position sensor, chosen because of its multi purpose use,feature location, and ability to read bar codes.A progressive-die stamping machine operates in closed loop. A linearoutput proximity sensor pro

25、vides control feedback for optimizing dieoperation; a servo motor adjusts die position in the bend stage. A linearproximity sensor was selected to give a dimensional readout from the metalstamping operation; data are used in a closed-loop control system.Part inspection uses a laser distance measurem

26、ent device to determinesurface flatness. Sensor measures deviation in return beams, indicatingdifferent surface attributes to 10 microns in size. An encoder wouldnthave worked because distance was more than a meter. Laser measurement wasthe technology chosen because it had very high spatial resoluti

27、on, didnot require surface contact, and had a very high distance resolution.An automotive key and lock assembly system uses a proximity sensor for detectinga cap in the ready position. A laser profile sensor applied with a robot measuresthe key profile.What to use, where? Sensor manufacturers agree

28、that matching advantages inherent to certain positionsensing technologies can help various applications.David Edeal, product marketing manager, MTS Sensors Div., says, for harsh factoryautomation environments, the most significant factors even above speed andaccuracy in customers minds are product d

29、urability and reliability. Therefore,products with inherently non-contact sensing technologies (inductive,magnetostrictive, laser, etc.) have a significant advantage over those that relyon physical contact (resistive, cable extension, etc.)Other important factors, Edeal says, are product range of us

30、e and applicationflexibility. In other words, technologies that can accommodate significantvariations in stroke range, environmental conditions, and can provide a widerange of interface options are of great value to customers who would prefer toavoid sourcing a large variety of sensor types. All tec

31、hnologies are inherentlylimited with respect to these requirements, which is why there are so manyoptions.Edeal suggest that higher cost of fitting some technologies to a certainapplication creates a limitation, such as with linear variable differentialtransformers. For example, LVDTs with stroke le

32、ngths longer than 12 inches arerare because of the larger product envelope (about twice the stroke length) andhigher material and manufacturing costs. On the other hand, magnetostrictivesensing technology has always required conditioning electronics. With the adventof microelectronics and the use of

33、 ASICs, we have progressed to a point where,today, a wide range of programmable output types (such as analog, encoder, andfieldbus) are available in the same compact package. Key for sensor manufacturersis to push the envelope to extend the range of use (advantages) while minimizingthe limitations (

34、disadvantages) of their technologies.Listen to your app Different sensor types offer distinct advantages for various uses, agrees TomCorbett, product manager, Pepperl+Fuchs. Sometimes the application itself isthe deciding factor on which mode of sensing is required. For example, a machinesurface or

35、conveyor belt within the sensing area could mean the differencebetween using a standard diffused mode sensor, and using a diffused mode sensorwith background suppression. While standard diffused mode models are not ableto ignore such background objects, background suppression models evaluate lightdi

36、fferently to differentiate between the target surface and backgroundsurfaces.Similarly, Corbett continues, a shiny target in a retro-reflective applicationmay require use of a polarized retro-reflective model sensor. Whereas a standardretro-reflective sensor could falsely trigger when presented with

37、 a shiny target,a polarized retro-reflective modeluses a polarizing filter to distinguish theshiny target from the reflector.MTS Edeal says, Each technology has ideal applications, which tend to magnifyits advantages and minimize its disadvantages. For example, in the wood productsindustry, where hi

38、gh precision; varied stroke ranges; and immunity to high shockand vibration, electromagnetic interference, and temperature fluxuations arecritical, magnetostrictive position sensors are the primary linear feedbackoption. Likewise, rotary optical encoders are an ideal fit for motor feedbackbecause of

39、 their packaging, response speed, accuracy, durability, and noiseimmunity. When applied correctly, linear position sensors can help designersto ensure optimum machine productivity over the long haul.Thinking broadly first, then more narrowly, is often the best way to designsensors into a system. Ede

40、al says, Sensor specifications should be developedby starting from the machine/system-level requirements and working back towardthe subsystem, and finally component level. This is typically done, but what often happens is that some system-level specifications are not properly orcompletely translated

41、 back to component requirements (not that this isa trivialundertaking). For example, how machine operation might create unique oradditional environmental challenges (temperature, vibration, etc.) may not beclear without in-depth analysis or past experience. This can result in anunder-specified senso

42、r in the worst situation or alternatively an over-specifiedproduct where conservative estimates are applied.Open or closedEarly in design, those involved need to decide if the architecture will beopen-loop or closed-loop. Paul Ruland, product manager, AutomationDirect, says,Cost and performance are

43、generally the two main criteria used to decide betweenopen-loop or closed-loop control in electromechanical positioning systems.Open-loop controls, such as stepping systems, can often be extremely reliableand accurate when properly sized for the system. The burden of tuning aclosed-loop system prior

44、 to operation is not required here, which inherentlymakes it easy toapply. Both types can usually be controlled bythe same motioncontroller. A NEMA 23 stepping motor with micro-stepping drive is now availablefor as little as $188, compared to an equivalent servo system at about $700.Edeal suggests,

45、Control systems are created to automate processes and thereare many good examplesof high-performance control systems that require littleif any feedback. However, where structural system (plant) or input (demand ordisturbance) changes occur, feedback is necessary to manage unanticipatedchanges. On th

46、e process side, accuracyboth static and dynamicis importantfor end product quality, and system stability and repeatability (robustness)are important for machine productivity.For example, Edeal says, in a machining or injection molding application,the tool, mold or ram position feedback is critical t

47、o the final dimension of the fabricated part. With rare exceptions, dimensional accuracy of the part willnever surpass that of the position sensor. Similarly, bandwidth (response speed)of the sensor may, along with response limitations of the actuators, limitproduction rates.Finally, a sensor that i

48、s only accurate over a narrow range of operatingconditions will not be sufficient in these types of environments where high shockand vibration and dramatic temperature variations are common.The latestWhat are the latest position sensing technologies to apply to manufacturing andmachining processes a

49、nd why?Ruland says, Some of the latest developments in positioning technologies formanufacturing applications can be found in even the simplest of devices, suchas new lower-cost proximity switches. Many of these prox devices are nowavailable for as little as $20 and in much smaller form factors, dow

50、n to 3 mmdiameter. Some specialty models are also available with increased responsefrequencies up to 20 kHz. Where mounting difficulties and cost of an encoderare sometimes impractical, proximity switches provide an attractive alternative;many position control applications can benefit from increased

51、 performance,smaller package size, and lower purchase price and installation cost.Corbett concurs. Photoelectric sensors are getting smaller, more durable, andflexible, and are packed with more standard features than ever before. Some newphotoelectrics are about half the size of conventional cylindr

52、ical housings andfeature welded housings compared with standard glued housings. Such featuresare very desirable in manufacturing and machining applications where space iscritical and durability is a must. And more flexible connectivity and mounting optionsside mount or snout mount are available from

53、 the same product allowusers to adapt a standard sensor to their machine, rather than vice versa.Another simple innovation, Corbett says, is use of highly visible, 360-degreeLED that clearly display status information from any point of view. Suchenhanced LED indicates overload and marginal excess ga

54、in, in addition to powerand output. Such sensors offer adjustable sensitivity as standard, but areavailable with optional tamperproof housings to prevent unauthorizedadjustments.Photoelectric SensorsPhotoelectric sensors are typically available in at least nine or more sensingmodes, use two light so

55、urces, are encapsulated in three categories of packagesizes, offer five or more sensing ranges, and can be purchased in variouscombinations of mounting styles, outputs, and operating voltages. It createsa bewildering array of sensor possibilities and a catalog full of options.This plethora of choice

56、s can be narrowed in two ways: The first has to do withthe object being sensed. Second involves the sensors environment.Boxed inThe first question to ask is: What is the sensor supposed to detect? Are wedoing bottles? Or are we detecting cardboard boxes? says Greg Knutson, a seniorapplications engin

57、eer with sensor manufacturer Banner Engineering.Optical properties and physical distances will determine which sensing mode andwhat light source work best. In the case of uniformly colored boxes, for example,it might be possible to use an inexpensive diffuse sensor, which reflects lightfrom the box.

58、 The same solution, however, cant be used when the boxes are multicolored andthus differ in reflectivity. In that case, the best solution might be an opposedor retroreflective mode sensor. Here, the system works by blocking a beam. Whena box is in position, the beam is interrupted and the box detect

59、ed. Withouttransparent boxes, the technique should yield reliable results. Several sensorscould gauge boxes of different heights.Distance plays a role in selecting the light source, which caneither be an LEDor a laser. LED is less expensive. However, because LED are a more diffuse lightsource, they

60、are better suited for shorter distances. A laser can be focusedon a spot, yielding a beam that can reach long distances. Tight focus can alsobe important when small features have to be sensed. If a small feature has tobe spotted from several feet, it may be necessary to use a laser.Laser sensors use