Talk:Parallel manipulator

high bandwidth motion capability?

This article contains the phrase high bandwidth motion capability. I am in the process of disambiguating links to the word bandwidth. I found this term a bit odd, because in context it seems to mean motion capable of very agile adjustments, but it is an unusual usage of bandwidth. Is this a term commonly used this way? It does not seem to fit well with any of the existing definitions of that word, most of which fall into one of two categories: a range of frequencies, or a bit rate. If this is a common phrase used by mechanical engineers or robotics experts, perhaps an article like Bandwidth (robotics) needs to be created. Any help from an expert would be appreciated! CosineKitty (talk) 22:03, 30 June 2008 (UTC)

I agree with your argument. I think the term "bandwith" is not appropriately well used here. I work in robotics and I never used the term "bandwith" regarding motion, only in data transmission. I think this sentence is better: "wide range of motion capability". Anonymous 08:45, 22 September 2008 (UTC) —Preceding unsigned comment added by 147.83.48.86 (talk)

A range of frequencies. I suspect this is control theory jargon, inserted by a control engineer. But I agree there is a better way of saying it.

By "high bandwidth", I'm pretty sure the original author is trying to say that the device has a high mechanical "natural frequency". The lower moving mass and higher stiffness of parallel configuration -- compared to a serial arm configuration using the same actuators -- allows us to drive the end effector in a square wave -- from point A to point B (rise time), stop there, and then move it back to point A (fall time) -- at a higher frequency, with less overshoot.

This is useful when we want the robot to move lots of parts, one at a time, from some fixed location A to some other fixed location B.

But the original author, like myself, finds it all too easy to accidentally throw in technical jargon which makes it sound far more complicated than it really is. --68.0.124.33 (talk) 21:14, 14 December 2008 (UTC)

Merge

I vote for the merge into parallel robot. --- BAxelrod (talk) 03:58, 23 November 2008 (UTC)

Done. I merged the other way, from parallel robot into parallel manipulator. Mainly because I think this configuration is closer to the definition of a manipulator than the definition of a robot. Although it's even more like a mechanical linkage. --68.0.124.33 (talk) 21:22, 14 December 2008 (UTC)

Merge

this page should me merged with Delta robot Batsu (talk) 20:21, 20 October 2009 (UTC)

Oppose. Delta robots are a later development and although they are certainly related, they're sufficiently distinct in their own right. Andy Dingley (talk) 10:29, 5 August 2010 (UTC)

Attention needed

* Tidyup after merge - opening sentence in the lead seems in the wrong place * Expand - if possible Chaosdruid (talk) 01:50, 8 August 2010 (UTC)

•  Done Work done, thanks Andy - assessed. There is still a little work needing to be done in regard to headers and sections. Chaosdruid (talk) 10:12, 15 March 2011 (UTC)

Problem in statement 1

"Errors in one chain's positioning are averaged in conjunction with the others, rather than being cumulative."

This assumpiion is wide spread in the scientific community. It seems to be self-evident at a first sight. But..

Ilian Bonev sais:

ARE PARALLEL ROBOTS MORE ACCURATE THAN SERIAL ROBOTS? Sébastien Briot and Ilian A. Bonev Département de génie de la production automatisée, École de technologie supérieure (ÉTS), 1100, rue Notre-Dame Ouest, Montréal, Québec, H3C 1K3, Canada e-mail: ilian.bonev@etsmtl.ca

"ABSTRACT It is widely claimed that parallel robots are intrinsically more accurate than serial robots because their errors are averaged instead of added cumulatively, an assertion which has not been properly addressed in the literature....."

"...So, in this example, one might indeed say that there is an averaging of errors in the parallel robot. However, when its end-effector is close to certain singularities, then the maximal position error could be several times larger than the input error (in the case of prismatic actuators). We therefore believe that this is, in general, too strong a statement and should be avoided. ..." — Preceding unsigned comment added by JoachimLlambiCorrectness (talk • contribs) 18:45, 23 June 2016 (UTC)

Problem in statement 2

"Because of the difficulty of such a non-linear command, the parallel manipulators are not yet used in high precision machining, despite their excellent mechanical properties (speed and precision)."

There is no lack in computer horsepower today that might be a problem here. Therefore, another issue should be stressed, please have a look at ciations below. The main problems are accuracy issues.

FIRST CITATION

ANNALS OF FACULTY  ENGINEERING HUNEDOARA – INTERNATIONAL JOURNAL OF ENGINEERING Tome X (Year 2012) – Fascicule 2(ISSN 1584 -2665) Zoran PANDILOV , Vladimir DUKOVSKI  PARALLEL KINEMATICS MACHINE TOOLS: OVERVIEW‐ FROM HISTORY TO THE FUTURE

"Although more than 15 years passed since the first commercial kinematics machine tools were introduced, they are not widely accepted in the industry. From the beginning of their appearance it became obvious that implementation of their theoretical capabilities in practice introduces many new problems. Accuracy of the parallel kinematics machine tools has become one of their main weaknesses."

SECOND CITATION

Parallel Robots: Open Problems Jean-Pierre MERLET INRIA, BP 93, 06902 Sophia-Antipolis, France E-mail: Jean-Pierre.Merlet@sophia.inria.fr

"4 Calibration Practical use of the inverse and direct kinematics requires a perfect knowledge of certain geometric el- ements of the robot, particularly for accurate robots. Thus, position control of a Gough platform needs the locations of the passive joints (a full model requires 132 parameters [35]). Even if a quite accurate estimates of these parameters are available, a calibration may be necessary. Although this problem has been solved for serial robots, this is not the case for parallel robot." — Preceding unsigned comment added by JoachimLlambiCorrectness (talk • contribs) 18:47, 23 June 2016 (UTC)

Rewrote section, Concomitant motion

Rewrote section, Concomitant motion. This is an important topic. Thanks to the author for introducing the topic into this Wikipedia page and for providing the framework for its contents. This edit attempts to reword the main concepts introduced in this section. Changed title from `Concomitant motion’ to `Lower mobility’. This change emphasizes the causal relationship between ‘lower mobility’ and ‘concomitant motion’, i.e. concomitant motion is a consequence of lower mobility. Reorganized the section. Introduced the concept of `degrees of freedom’, to provide more background for people unfamiliar with the field of study. Motivated the importance of lower mobility manipulators. Talked about their advantages. Talked about their disadvantages, in terms of parasitic motion. Pointed out the importance of designing lower mobility manipulators, while being cognizant of the possible disadvantages of parasitic motion. Repeatedly refered to the successful Delta robot as an example, to elucidate the characteristics and significance of lower mobility manipulators in general. Fixed some obvious typos like, ` the mechanism may contain dependent and dependent motion’. Eliminated mathematical notation such as `∈ℝ^6’. Added more citations. — Preceding unsigned comment added by Pjwiktor (talk • contribs) 20:27, 3 December 2020 (UTC)