Talk:Kinematic chain

Revisions to kinematic chain
I see that a number of flags have been placed on this page requesting revisions. I would be pleased to address these concerns. Prof McCarthy (talk) 18:53, 7 January 2012 (UTC)

No contents block
It is interesting that unlike other articles, this particular article does not have an automatically generated contents block. Prof McCarthy (talk) 20:37, 7 January 2012 (UTC)
 * Short articles with few headings don't - they appear automatically. Andy Dingley (talk) 21:07, 7 January 2012 (UTC)

Further revisions
I look forward to expanding the section on analysis of kinematic chains to set a context for forward and inverse kinematics of robots. Then I would like to add a section on synthesis of kinematic chains which will link to Burmester theory. Prof McCarthy (talk) 20:28, 8 January 2012 (UTC)
 * I have removed the clean-up and wikify templates, in hope that this article is now acceptable. I also increased the quality and importance rating of this article. Again I hope this is ok. Prof McCarthy (talk) 21:11, 9 January 2012 (UTC)
 * Not really, for a start the Robotics project only uses C-class for articles that are in need of work, either because they are being considered for B-class, or because they need work to retain B-class.
 * More importantly it is not really ok to assess an article that you have personally done a fair amount of work on - I would not give sutdents their own papers to mark.
 * Is it also correct that Kinematic chain refersonly to the mathematical model?
 * I have posted on your talk page with further info and requests. Chaosdruid (talk) 19:47, 15 January 2012 (UTC)
 * It is my mistake regarding the assessment, I did not realize that these were equivalent to grades. I obtained the assessments by comparing the article to articles on similar topics and their assessments.  I am pleased to accept the opinions of any assessment organization.
 * Here is the comment that Chaosdruid posted to my talk page regarding kinematic chains:
 * "Kinematic chain refers to the mathematical model of a mechanical system", the previous definition being:
 * "A kinematic chain is the assembly of several kinematic pairs connecting rigid body segments."
 * Now, regarding the description of a kinematic chain as a mathematical model. While, I am sensitive to the criticism that I may be adding too much in the way of equations, it seems to me that the description of links as rigid bodies and joints as kinematic pairs should be recognized as a mathematical abstraction that allows geometry to be applied to the study of mechanical devices.  So my first reaction is that describing a kinematic chain as an assembly of kinematic pairs and rigid links is a leap to an abstraction that the average reader would not recognize.  My hope was that describing a kinematic chain first as a mathematical model helps the reader to realize that a mechanical device is abstracted to ideal bodies and joints. Prof McCarthy (talk) 23:33, 15 January 2012 (UTC)


 * IMHO, we need to find a better way of expressing the link between real world bodies and parts and the mathematical representations of them. I am sure the average reader can be considered as having seen and used exploded view diagrams and instructions on assembly. I am also sure that they will be familiar with many abstractions of real life situations.
 * The solution is to find something that bridges the real world need for the abstracted models and the real world systems that use them to calculate and perform tasks in real life situations. In fact you have assumed that they can understand a totally abstracted explanation over one which compares it to the real world embodiment - surely that is asking even more of them?
 * I would suggest we try and work out something that combines the old and new explanations. Chaosdruid (talk) 02:37, 16 January 2012 (UTC)


 * I am happy to work out what ever you think is best, but I am not sure what to do. A kinematic chain is a mathematical model of a physical chain, not an exploded view.  A physical chain has links and joints and a kinematic chain is the geometric version of this physical chain in which the links are rigid and the joints perform pure rotation or translation.  In my opinion, the figures show examples of physical systems that are modeled as kinematic chains.  I am sorry but I do not see the problem, but then I did try to provide my best explanation in the original edits. Prof McCarthy (talk) 04:27, 16 January 2012 (UTC)


 * Why is what I wrote unacceptable: " Kinematic chain refers to the mathematical model of a mechanical system as an assembly of rigid bodies connected by joints." It refers to the rigid bodies and joints.  It simply calls the kinematic chain a mathematical model.  Prof McCarthy (talk) 04:39, 16 January 2012 (UTC)

My point was not that it should be an exploded view, just that people are familiar with abstractions like exploded view diagrams.

I did not say it was unacceptable, I said we need "to find a better way of expressing it" - your explanation says "refers to the mathematical model ... as an assembly of rigid bodies connected by joints". If you cannot see why that is wrong then I am at a loss. Chaosdruid (talk) 17:22, 16 January 2012 (UTC)


 * I thought I was saying that an assembly of rigid bodies connected by joints is a mathematical model for a mechanical system. Is this the source of the problem? Prof McCarthy (talk) 19:30, 16 January 2012 (UTC)
 * Yes - as the average reader would be perfectly correct in assuming rigid bodies and joints are physical rather than mathematical, though they are both. It just needs more explanation to tie the two together, though I can see the latest edit -> that is, which seems to adequately convey that message. Chaosdruid (talk) 02:28, 17 January 2012 (UTC)


 * Thank you for your patience, I believe this is a better way of describing a subtle point. Prof McCarthy (talk) 04:09, 17 January 2012 (UTC)

"zeroth" link?
From the section "Analysis of kinematic chains":


 * A chain of n links connected in series has the kinematic equations,
 * $$[T] = [Z_1][X_1][Z_2][X_2]\ldots[X_{n-1}][Z_n],\!$$
 * where [T] is the transformation locating the end-link---notice that the chain includes a "zeroth" link consisting of the ground frame to which it is attached.

How can somebody notice the zeroth link in the chain looking at the combined transformation in the excerpt where indices range from 1 to n?

85.110.33.18 (talk) 00:21, 23 December 2014 (UTC)

See WP:MOSMATH

 * wrong: M=6(N-1)
 * right: M = 6(N – 1)
 * right: M = 6(N – 1)

One should not indiscriminately italicize everything in non-TeX mathematical notation. Variables are italicized; digits and parenthesis are not, nor are things like sin, det, max, log, sup, lim, etc. The point in stylistic consistency. Note how it's done in TeX:
 * $$ M=6(N-1) \, $$

The 6, the 1, and the parentheses are not italicized. Also, a minus sign is not a stubby little hyphen, and proper spacing should be used.

This is codified in WP:MOSMATH. Michael Hardy (talk) 04:00, 13 January 2018 (UTC)