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[TMJ] Aspects of Input Shaping Control of Flexible Mechanical Systems

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New THE MATHEMATICA JOURNAL article:


Aspects of Input Shaping Control of Flexible Mechanical Systems

by DESMOND ADAIR, MARTIN JAEGER


ABSTRACT: Input shaping is an established technique to generate prefilters so that flexible mechanical systems move with minimal residual vibration. Many examples of such systems are found in engineering—for example, space structures, robots, cranes and so on. The problem of vibration control is serious when precise motion is required in the presence of structural flexibility. In a wind turbine blade, untreated flapwise vibrations may reduce the life of the blade and unexpected vibrations can spread to the supporting structure. This article investigates one of the tools available to control vibrations within flexible mechanical systems using the input shaping technique.

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POSTED BY: Moderation Team
Answer
3 months ago

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POSTED BY: John Hendrickson
Answer
3 months ago

As a modeling abstract and paper this is a great submission!

i'd like to ask if any cranes use this/such a system to control movement, and if they are safe if there is a bug in the software (software that relies on what is being moved, and environment such as temperature for length of cable, stretching of cable, etc)? I would also fear extra controls systems are needed so minor inputs do not override major systems (such as high speed wind warnings, weight limit warnings), or confuse the operator operating the crane with "extra things to monitor". It seems like there are serious problems unless one is speaking of limiting the natural frequency of a structure from self-reinforcing major (the first nodes of the worst of waves) ... unless we're speaking of something far lighter and less damaging like a disk drive.

As far as how (Western Digital) disk drive heads move - i would bet that's patented and a protected secret by an industry leader (including purchased companies - also the industry that started the industry). Am I wrong? While WD likely does use "frequencies" to make their drives more "responsive" i don't think they like to share it.

Again, as a modeling abstract and paper - it's a great submission.

POSTED BY: John Hendrickson
Answer
3 months ago

Wind power.

I'm interested how a fan blade that has no vibration in a wind tunnel (at design time), moved Smoothly toward the wind (who's rate of speed is limited by many factors), can cause vibration. (i assume the start of movement is not abrupt, since most electrical motors cannot do that - and use of those that can are unlikely used because they would cause a sudden force which was not cost effective or intended)

Is there a URL of a site showing actual vibration data of wind generators which shows why a front facing powered pivot (not a rear facing wind controlled one) would be used, and exactly what vibrations are detected during tests that are objectionable?

POSTED BY: John Hendrickson
Answer
3 months ago

John,

I am not an author on this journal paper, however, I originated Input Shaping in my thesis in 1989 and coined the phrase in the early 1990's along with (ZV, ZVD,etc.). (for example the N. C. Singer and W. P. Seering reference in the Journal Article above). In the last (almost) 30 years Input Shaping has been used on millions of machines worldwide (including disk drives for acoustics and for settle time, disk head testers, high precision industrial machines, etc.). It has been used on many cranes including cranes handling nuclear waste, cranes loading nuclear fuel rods into commercial power plant reactors and other less critical crane applications. In crane applications it is used for safety reasons because the load sway is dangerous -- overshoot can cause accidents. It is now taught at many universities.

I enjoyed reading the paper -- I thought it was a great use of Wolfram technology to present this topic. Great job, authors!

I think the history of the topic is a bit inaccurate regarding the references in the 1950's -- in that era they were not really capable of doing Input Shaping (before digital processing). The analog versions of related approaches were really quite different -- Posicast for example, was breaking a step into two analog steps and not really "Input Shaping". However, minor historical points aside I really enjoyed the paper.

Regards,

Neil Singer

POSTED BY: Neil Singer
Answer
3 months ago

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