Talk:Damping

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So an underdamped door-closer will "bounce" on the way to being closed?  Should mention this to complete the analogy. jyavner 21:31, 26 November 2005 (UTC)

I think the door-closer analogy is a bit confusing. A door-closer's motion is only described by a second-order differential equation if there is a spring involved, as well as the mass and damper. If it's just a mass and damper, then it can be described by a first-order differential equation and it cannot be described as over-, critically-, or under-damped. Perhaps a spring should be mentioned in these analogies? Dkraemer1 19:43, 11 January 2007 (UTC)

Contents

[edit] Image change

I've replaced Image:Springdampermass.png with Image:Mass-Spring-Damper.png, which I originally drew for Nondimensionalization. I also changed the symbol used for the damping constant in the article from R to B to match the image. Of course, it would be easy to create a variant of the image with a different symbol and without the external force arrow, but I feel it looks good enough as it is. If you disagree, please say so (or just revert me, it's no big deal). —Ilmari Karonen (talk) 23:03, 24 January 2006 (UTC)

Move from my talk--Light current 21:22, 27 May 2006 (UTC)

I think that the figure looks great, but it is a little bit confusing on one point: x should be defined as positive in one direction. Showing x going both ways makes it difficult to figure out the direction of the spring and damping forces. Dkraemer1 19:46, 11 January 2007 (UTC)

[edit] Notation changes at Damping

I notice you (and 72.132.7.159, which I assume is your IP address) have been editing Damping to change the notation used in the article, in particular changing the sigmas used to denote the damping factor to zetas (or, in earlier edits, to alphas). While I appreciate your attempts to improve the article, plase note the following:

  • The article currently has consistent notation. Please keep it that way. If you change, for example, some of the sigmas to zetas without changing them all, the article becomes very confusing and potentially misleading. When making notation changes like this, please either a) use the preview button to check your edits, and only save after you've checked that you've changed all the symbols consistently, or b) copy and paste (the relevant sections of) the article to the talk page or to a user subpage for drafting, make the changes there, and then copy the result back.
  • The symbol zeta (ζ), in particular, is already used in the article to denote the damping ratio (σ/ω0). If you wish to use it for the damping factor, you need to choose some other symbol for the ratio.

In general, it's better to discuss changes like this on the talk page first before making them. That way, we can choose a consistent notation that all editors find appropriate and avoid needless back-and-forth edit warring. It also makes it less likely for someone to mistake your edits for sneaky vandalism. —Ilmari Karonen (talk) 20:38, 27 May 2006 (UTC)

72.132.7.159 is not my address. I always log in. The symbol for damping factor is zeta. Someone else has been changing the symbols. I intend to revert the page and change the so called 'damping ratio' symbol to sigma as it should be.--Light current 21:17, 27 May 2006 (UTC)
Actually, it seems you introduced the use of σ (it used to be α) for the damping factor yourself. The note about ζ being used for the damping ratio was added earlier by 212.225.34.56. (Note: Both of these diffs combine multiple consecutive edits by the same user.) —Ilmari Karonen (talk) 23:33, 27 May 2006 (UTC)
Yes it does appear that I changed them from alphas to sigmas whilst meaning to change them to zetas. I obviously got confused between the two greek symbols 8-(.
However, zeta is the most commonly used symbol for damping factor and I think thats what it should be 8- ) Sorry for the confusion!
I dont remember introducing the note about zeta being used as damping ratio. I think that may be where some confusion arose as I may have misunderstood that edit to mean damping factor. So its not actually an edit war going on its just basically my mistake(s)! Sorry! I hope this clears up the confusion.
I suggest the symbol for damping ratio should be sigma. (I dont know what the convention is on that) 8-|--Light current 01:09, 28 May 2006 (UTC)

72.132.7.159 appears to be in agreement with me and has been changing the sigmas to zetas. But he didnt change them all. I changed the ones he missed. You reverted all his recent changes to the page. So Im not quite sure where we are now. I think we need to revert to a much earlier version around 18 May and go from there. What do you think?--Light current 01:50, 28 May 2006 (UTC)

I've been reverting any changes that left the notation in an inconsistent state — I don't personally care whether the symbol for the damping factor is σ or ζ, as long as it's consistently one or the other. The article is right now essentially same as it was on 18 May; the changes since then are mostly cosmetic (ω0 to ω0 etc.). In any case, if no-one objects to the notation change, I'd be happy to do it for you; in fact, I've already done it on my user subpage (took me all of two minutes with a bit of javascript). What do you think? —Ilmari Karonen (talk) 12:05, 28 May 2006 (UTC)

Yes thanks for taking the time to do that 8-). Ive copied it from your sub page now and it is correct IMO and consistent. One thing that is bothering me tho' is the introduction of the 'damping ratio' early on and its inclusion in the system description. THis tends to confuse the issue. The equation is usually quoted using the damping factor only. I intend to change this soon. THanks for your help. 8-)--Light current 14:01, 28 May 2006 (UTC)

I see the conflict. There seem to be conflicting definitions of "damping ratio", not just different symbols. For the most part, this article seems to differentiate the two properly by calling one the damping "factor" and the other the damping "ratio". Modern control theory states that the damping ratio is used to determine whether the system is over, under, or critically damped. Using the equation m \ddot{x} + B \dot{x} + k x = 0, there are two ways to define the damping. I will denote the damping ratio as it is currently defined in the article, though I personally use them the opposite way.
Definition 1: \zeta = { B \over 2m }
This definition really doesn't give much meaning to the term, requiring it be compared to the natural frequency.
Definition 2: \sigma = { B \over 2m \times \omega_0}
Rather than comparing it to your natural frequency, your system is always critically damped when σ = 1. This seems to be much more convenient by definition, so the roots of your system will be found using the quadratic s^2 + 2\sigma\omega_0s + \omega_0^2 = 0--Mysteryegg 16:37, 20 July 2006 (UTC)

I think that using zeta, as in \zeta = { B \over 2m \omega_0}, is the way to go. That is what appears in the article currently, written as \zeta = { B \over 2 \sqrt{k m} }. However, the name for this parameter is given as the "damping factor". This is not the standard in engineering literature, from what I've seen. It should be called the "damping ratio". A quick look at the Wikipedia entries for damping ratio and damping factor confirms this conclusion. Dkraemer1 20:34, 11 January 2007 (UTC)

I want to propose a constant change for the damping coefficient from capital B to a lower case c. This change would put the article in line with the standard notation taken in most engineering programs. Also, pertaining to the zeta conversation, zeta is the appropriate symbol as far as I've ever seen in all of my engineering courses and textbooks. --Barkman 17:34, 15 February 2007 (UTC)

[edit] Pictures

I dont think these pics are particularly helpful (sorry) . There are some better ones you could use over at tuned circuit I think! 8-)--Light current 00:22, 5 June 2006 (UTC)

--Mysteryegg 20:16, 23 July 2006 (UTC)== Dampening is not Damping ==

Hey what's the deal? I added an explaination about the differences between dampening and damping since it is a very common mistake and someone wantonly obliterated it. dq 23:21, 12 June 2006 (UTC)

The two words are obviously different 8-|--Light current 23:23, 12 June 2006 (UTC)

Do you watch any of the Star Treks? They get it wrong all the time. Most engineers get it wrong too if they are not vibration experts. dq 02:49, 13 June 2006 (UTC)

Im not a vibration expert. I dont get it wrong 8-)--Light current 03:05, 13 June 2006 (UTC)

Unfortuneately, not everyone is like you. Maybe we need a third party is this discussion? dq 16:23, 15 June 2006 (UTC)

I dont think so! But please ask anyone else for thier opinion 8-)--Light current 16:29, 15 June 2006 (UTC)

Agree that this should be in the article. I wish people would stop removing stuff like this.

Dampening is "To deaden, restrain, or depress" while damping is "The capacity built into a mechanical or electrical device to prevent excessive correction and the resulting instability or oscillatory conditions." See also dampening, dampening effect. — Omegatron 21:57, 27 June 2006 (UTC)

I think this may be largely a matter of opinion but IMO, damping is the correct scientific term. Dampening means to make something damper (ie wetter)--Light current 22:10, 27 June 2006 (UTC)
I got mine from a dictionary. It has multiple meanings. — Omegatron 00:53, 28 June 2006 (UTC)
So did I. In over 30 years in electronics, I have never heard the term dampening used, nor have I seen it in any of the hundreds of books I must have read over that time. If you can find a reliable respected reference source using the term 'dampening' to describe what we are tring to, then I will accept it for inclusion 8-)--Light current 07:11, 28 June 2006 (UTC)

Both terms are gerunds. Their roots, Dampen and Damp, have several transitive and intransitive definitions. Among the "control/limit" definitions, dampen and damp can seem very similar by denotation. The gerunds, however, are not usually used in the same connotation. Only damping can relate to control theory or oscillations. In other words, if you damp a second order system to keep it within stable parameters, you are dealing with its damping, which is now a term describing a field of study. Dampening is not used in its gerund form as often and more often relates to suppressing abstract concepts, like dampening a political movement. Webster uses "The heat dampened our spirits" as an example.

You might look at the words' origins to confirm this, but you might suggest that all physical properties are damped and abstract properties are dampened. However, I'm more inclined to believe that damping requires indirectly affecting oscillations, etc. by controlling some damping factor that it depends on. Therefore dampen is used for taking direct actions to "silence" the direct object where there is no differential equation to describe the situation. This could justify musicians' use of dampening when they just use their hands to dampen the sound. Supporting the physical/abstract theory, for example, you might damp a fire, or use "inertial dampers" in Star Trek, but dampen a mood. The latter theory might be supported by the same examples saying that you are limiting the oxygen factor that fire needs or increasing the stiffness parameter in a spring, while there is no differential equation and thus no damping ratio to describe direct intervention.

My conclusion is: damping is a mathematical concept describing a means of affecting some natural response with a constant damping factor, and dampening is a direct intervension of the scope of some concept with no defined consistant damping factor.--Mysteryegg 20:11, 23 July 2006 (UTC)

Oh it's also interesting to note that a "damper" can relate to either term.

[edit] The importance of gamma

Can anyone say why this parameter has been introduced? It just seems to complicate the picture! I mean what does it represent anyway? 8-(--Light current 21:12, 27 June 2006 (UTC)

It's the exponent you solve for. In any case, it's useful to let the reader know that the whole system can be characterized by a single complex parameter, at least to anyone who is familiar with exponentials in the complex plane. Knowing that the solution is of the form eγt immediately tells me that, depending on the parameter, the solution will look like exponential decay possibly combined with oscillation.
By the way, have you been leaving the notation in an inconsistent state again? You really should work on a userspace copy rather than keep making these incremental changes to the "live" version of the article. (Actually, I took a closer look at the history and it looks as if there's been something funny going on with the equations for quite a while. I'll need to dig up some older versions and see if I can straighten it out.) —Ilmari Karonen (talk) 08:42, 28 June 2006 (UTC)

THe page history shows that it is not I who has been tinkering with the equations (lately).

THe introduction of gamma is confusing and uneccesary to the explanation (especially when it doesnt represent anything tangible). I have never seen gamma quoted in these sorts of equations before and I suggest removal to simplify page. 8-|--Light current 09:01, 28 June 2006 (UTC)

[edit] Units

Please add appropriate units for variables and constants - discussion of physics/mechanics topics is greatly improved by including a consistent set of units.

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