Mechanisms and Robotics

Lecture Notes


I am pleased to provide these notes that I have used in my Theory of Machines (Mechanisms and Robotics) classes over the past years.

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Wikipedia and Mechanisms and Robotics: J. Michael McCarthy, May 3, 2012
Type “mechanism” or “robotics” into and the first items to appear are Wikipedia articles. In fact, chances are that any technical term in mechanisms and robotics, such as “machine,” “gear,” or “inverse kinematics,” will yield Wikipedia articles on the first page.

Internet marketers work hard to achieve first page rankings in Google’s search algorithm using techniques known as search engine optimization (SEO). In response Google regularly revises its algorithm to reduce the presence of web-sites that have poor content but high rankings, a sign of effective SEO. (1) A revision introduced in early 2011 seems to like Wikipedia.

When teaching, I check to see what my students find on-line with search terms like “four-bar linkage” and “mechanical advantage,” even “screw theory” and “quaternions.” Last year I became so frustrated with the poor quality of the articles appearing at the top of my searches, that on May 27, 2011 I created a user account and entered Wikipedia as a novice editor.
I am approaching one year and 3,800 edits on over 60 articles on Wikipedia. While I could not repair everything that I felt was wrong or misleading, I am claiming success, because the culture of Wikipedia imposes limits on what can be done.

This experience has sharpened my appreciation for the challenge of managing information on the Internet. Before I get to this, let me share some advice regarding the world that is Wikipedia.


Wikipedia and Moment of Inertia: J. Michael McCarthy, April 15, 2013
Moment of inertia is not a moment when you feel inert, it is a technical parameter that defines the resistance you feel when you spin a tire on its axle. With two years of experience as a Wikipedia editor, and over 6500 edits on something like 70 different articles, I have to say I am having increasing moments of inertia in the non-technical sense.

Articles in Wikipedia have a charm that comes from a variety of editors adding what they feel helps a reader’s understanding. This can yield surprising connections with other sources, as well as a confusing mess. Errors can be frustrating, but then they are usually easily corrected. Furthermore, this community kindly corrects typographical errors and is attentive to removing the electronic version of graffiti.

However, just as I find out that Apple’s iBooks Author automatically includes Wikipedia as a source for its glossary, I am increasingly weary of what is probably the natural order of things.


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