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Spin measuring at China Open

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    Posted: 06/02/2019 at 3:23am
I think this is the first tournament that I've seen where we're provided the occasional measurement of the spin of the ball. The highest I've seen so far was somewhere over 6000 RPM. 

Does anyone know what technology or programme is being used for these analyses and how accurate they are? Is it just a super hi definition camera and a super slow motion programme? 

Would be a great gadget to have at a club, maybe have a table set up for serving practice which displays the RPM of each serve on a big sign.

 (Let people buy 5 serves for a pound at a tournament,  person with the spinniest serve at the end of the day gets half of the pot. )
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blahness Quote  Post ReplyReply Direct Link To This Post Posted: 06/02/2019 at 9:16am
Originally posted by Simon_plays Simon_plays wrote:

I think this is the first tournament that I've seen where we're provided the occasional measurement of the spin of the ball. The highest I've seen so far was somewhere over 6000 RPM. 

Does anyone know what technology or programme is being used for these analyses and how accurate they are? Is it just a super hi definition camera and a super slow motion programme? 

Would be a great gadget to have at a club, maybe have a table set up for serving practice which displays the RPM of each serve on a big sign.

 (Let people buy 5 serves for a pound at a tournament,  person with the spinniest serve at the end of the day gets half of the pot. )

I saw a Ma Long powerloop BH get up to 7000rpm. Xu Xin had a FH loop going to 7700rpm. Insane!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote igorponger Quote  Post ReplyReply Direct Link To This Post Posted: 06/02/2019 at 12:33pm
The rotation speed of the service ball delivered by world-class table tennis players
https://ci.nii.ac.jp/naid/130004489716

High Speed Camera 1000 fps was empoyed.


Quote The performance of four rubber sheets was compared according to the catalogue specifications from two companies that made them. In addition, we experimented with changing the ball speed from 20 to 70 km/h and the spin rate from 0 to 4300 rpm by the machine. From the experiment results, it was found that the coefficients of restitution in all rubber sheets decrease as the incidence ball speed is faster. Also, the coefficient of restitution was influenced by the racket angle (incidence angle). The speed and spin rate in the two types of rubber sheets had the same rebound performance values in these catalogue specifications, whereas other types of rubber sheets were different from those in the catalogue.</p>



Edited by igorponger - 06/03/2019 at 9:24am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote benfb Quote  Post ReplyReply Direct Link To This Post Posted: 06/02/2019 at 1:26pm
Originally posted by igorponger igorponger wrote:

Ball Spinning Rate with top players at the serving actions.
https://ci.nii.ac.jp/naid/130004489716

High Speed Camera 1000 fps was empoyed.


Quote The performance of four rubber sheets was compared according to the catalogue specifications from two companies that made them. In addition, we experimented with changing the ball speed from 20 to 70 km/h and the spin rate from 0 to 4300 rpm by the machine. From the experiment results, it was found that the coefficients of restitution in all rubber sheets decrease as the incidence ball speed is faster. Also, the coefficient of restitution was influenced by the racket angle (incidence angle). The speed and spin rate in the two types of rubber sheets had the same rebound performance values in these catalogue specifications, whereas other types of rubber sheets were different from those in the catalogue.</p>

That's a really interesting study, but that article in the link is from 2014 and studied serves only, and from 2009.  All of that is well before the plastic ball, so the numbers will be less now, and it doesn't explain how ITTF was able to measure spins of loops and get accurate numbers in the middle of a match.  I'm assuming the technology has really improved since 2014?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fulanodetal Quote  Post ReplyReply Direct Link To This Post Posted: 06/02/2019 at 4:32pm
" In addition, we experimented with changing the ball speed from 20 to 70 km/h and the spin rate from 0 to 4300 rpm by the machine. From the experiment results, it was found that the coefficients of restitution in all rubber sheets decrease as the incidence ball speed is faster. Also, the coefficient of restitution was influenced by the racket angle (incidence angle). The speed and spin rate in the two types of rubber sheets had the same rebound performance values in these catalogue specifications, whereas other types of rubber sheets were different from those in the catalogue."


Can somebody translate this into plain English? I got lost after 'coeficient '

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Post Options Post Options   Thanks (0) Thanks(0)   Quote aerial Quote  Post ReplyReply Direct Link To This Post Posted: 06/02/2019 at 7:24pm
the spinniest I saw was 7 thousand something rpms from Xu Xin
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ttssbba Quote  Post ReplyReply Direct Link To This Post Posted: 06/02/2019 at 9:44pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Simas Quote  Post ReplyReply Direct Link To This Post Posted: 06/03/2019 at 3:51am
Originally posted by igorponger igorponger wrote:

 
High Speed Camera 1000 fps was empoyed.

Yes, the rpm count was very interesting. Do you have more details about the camera and how it does it?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote zeio Quote  Post ReplyReply Direct Link To This Post Posted: 06/03/2019 at 6:06am
Viscaria FL - 91g
+ Neo H3 2.15 Blk - 44.5g(55.3g uncut bare)
+ Hexer HD 2.1 Red - 49.3g(68.5g 〃 〃)
= 184.8g
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Simon_plays Quote  Post ReplyReply Direct Link To This Post Posted: 06/03/2019 at 8:18am
Interesting, so it does take two hi-tech cameras and a whole lot of post-filming analyses to get that data. 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote igorponger Quote  Post ReplyReply Direct Link To This Post Posted: 06/03/2019 at 10:01am
MORE CLARITY NEEDED ....

Measuring spin on the sphere of 4cm diameter is the very hard problem.
I still can't see how they did it.
It all looks like a bogus data. I need some more clarifications on the spin measurements.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote zeio Quote  Post ReplyReply Direct Link To This Post Posted: 06/03/2019 at 10:53am
More concrete info about the system.


Edited by zeio - 06/03/2019 at 10:53am
Viscaria FL - 91g
+ Neo H3 2.15 Blk - 44.5g(55.3g uncut bare)
+ Hexer HD 2.1 Red - 49.3g(68.5g 〃 〃)
= 184.8g
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Post Options Post Options   Thanks (0) Thanks(0)   Quote qpskfec Quote  Post ReplyReply Direct Link To This Post Posted: 06/03/2019 at 3:26pm
Originally posted by igorponger igorponger wrote:

   MORE CLARITY NEEDED ....

Measuring spin on the sphere of 4cm diameter is the very hard problem.
I still can't see how they did it.
It all looks like a bogus data. I need some more clarifications on the spin measurements.


Similar systems have been used in pro golf and baseball to give ball data for several years. Many golf shops also have equipment to measure these parameters so customers can get the optimum clubs for their swing. Some club makers allow customers to visit their facilities to use even more sophisticated swing analyzers.

The tt ball has 2 big logos, DHS on one side and Seamaster on the other. I suspect that the frame analysis can key in on one or more logos and calculate ball rotation over #s of frames. They are capturing from 2 angles, so they should always be able to see the logos.

Other sports show that high frame capture rates + lots of computing power can yield almost real time results with high degrees of accuracy.



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Post Options Post Options   Thanks (1) Thanks(1)   Quote mykonos96 Quote  Post ReplyReply Direct Link To This Post Posted: 06/03/2019 at 3:33pm
Originally posted by qpskfec qpskfec wrote:

Originally posted by igorponger igorponger wrote:

   MORE CLARITY NEEDED ....

Measuring spin on the sphere of 4cm diameter is the very hard problem.
I still can't see how they did it.
It all looks like a bogus data. I need some more clarifications on the spin measurements.


Similar systems have been used in pro golf and baseball to give ball data for several years. Many golf shops also have equipment to measure these parameters so customers can get the optimum clubs for their swing. Some club makers allow customers to visit their facilities to use even more sophisticated swing analyzers.

The tt ball has 2 big logos, DHS on one side and Seamaster on the other. I suspect that the frame analysis can key in on one or more logos and calculate ball rotation over #s of frames. They are capturing from 2 angles, so they should always be able to see the logos.

Other sports show that high frame capture rates + lots of computing power can yield almost real time results with high degrees of accuracy.




It seems that xx FH loop is about 7500 rpm that tops old mazunov record 6000tpm BH loop ,I thought that pros played with less spin
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FruitLoop Quote  Post ReplyReply Direct Link To This Post Posted: 06/03/2019 at 8:28pm
Originally posted by qpskfec qpskfec wrote:

Originally posted by igorponger igorponger wrote:

   MORE CLARITY NEEDED ....

Measuring spin on the sphere of 4cm diameter is the very hard problem.
I still can't see how they did it.
It all looks like a bogus data. I need some more clarifications on the spin measurements.


Similar systems have been used in pro golf and baseball to give ball data for several years. Many golf shops also have equipment to measure these parameters so customers can get the optimum clubs for their swing. Some club makers allow customers to visit their facilities to use even more sophisticated swing analyzers.

The tt ball has 2 big logos, DHS on one side and Seamaster on the other. I suspect that the frame analysis can key in on one or more logos and calculate ball rotation over #s of frames. They are capturing from 2 angles, so they should always be able to see the logos.

Other sports show that high frame capture rates + lots of computing power can yield almost real time results with high degrees of accuracy.




The technology used in golf launchers is quite sophisticated using radar sensors. Using normal cameras alone is not how they do it but appears to be how ITTF are. This will undoubtedly give less accurate results but how inaccurate I am not sure.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Simas Quote  Post ReplyReply Direct Link To This Post Posted: 06/05/2019 at 8:47am
Originally posted by qpskfec qpskfec wrote:


The tt ball has 2 big logos, DHS on one side and Seamaster on the other. I suspect that the frame analysis can key in on one or more logos and calculate ball rotation over #s of frames. They are capturing from 2 angles, so they should always be able to see the logos.

that sounds reasonable.. maybe two logos are the key...


Edited by Simas - 06/05/2019 at 8:47am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote igorponger Quote  Post ReplyReply Direct Link To This Post Posted: 06/05/2019 at 9:36am
Originally posted by Simas Simas wrote:

Originally posted by qpskfec qpskfec wrote:


The tt ball has 2 big logos, DHS on one side and Seamaster on the other. I suspect that the frame analysis can key in on one or more logos and calculate ball rotation over #s of frames. They are capturing from 2 angles, so they should always be able to see the logos.

that sounds reasonable.. maybe two logos are the key...

<div id="gtx-trans" style=": ; left: 446px; top: -25px;"><div ="gtx-trans-icon">


The China Open sports arena is a vast hall. They claim only two cameras was in use to trace the path of the ball. The camera's standpoint is 40 meters away from the table.
You cant discern a tiny size markings on the ball from a distance of 40 meters. Unfeasable.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Simas Quote  Post ReplyReply Direct Link To This Post Posted: 06/05/2019 at 10:31am
Originally posted by igorponger igorponger wrote:

Originally posted by Simas Simas wrote:

Originally posted by qpskfec qpskfec wrote:


The tt ball has 2 big logos, DHS on one side and Seamaster on the other. I suspect that the frame analysis can key in on one or more logos and calculate ball rotation over #s of frames. They are capturing from 2 angles, so they should always be able to see the logos.

that sounds reasonable.. maybe two logos are the key...

<div id="gtx-trans" style=": ; left: 446px; top: -25px;"><div ="gtx-trans-icon">


The China Open sports arena is a vast hall. They claim only two cameras was in use to trace the path of the ball. The camera's standpoint is 40 meters away from the table.
You cant discern a tiny size markings on the ball from a distance of 40 meters. Unfeasable.

For me it seems rather unfeasible to see a 40mm ball from 40 meters traveling at 80km/h but here we are. So if they can see a 40mm ball, so it shouldn't be hard to see a 20mm dark blob on that white ball. It's not that you have to read...


Edited by Simas - 06/05/2019 at 10:36am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote qpskfec Quote  Post ReplyReply Direct Link To This Post Posted: 06/05/2019 at 1:08pm
Originally posted by Simas Simas wrote:

Originally posted by igorponger igorponger wrote:

Originally posted by Simas Simas wrote:

Originally posted by qpskfec qpskfec wrote:


The tt ball has 2 big logos, DHS on one side and Seamaster on the other. I suspect that the frame analysis can key in on one or more logos and calculate ball rotation over #s of frames. They are capturing from 2 angles, so they should always be able to see the logos.

that sounds reasonable.. maybe two logos are the key...

<div id="gtx-trans" style=": ; left: 446px; top: -25px;"><div ="gtx-trans-icon">


The China Open sports arena is a vast hall. They claim only two cameras was in use to trace the path of the ball. The camera's standpoint is 40 meters away from the table.
You cant discern a tiny size markings on the ball from a distance of 40 meters. Unfeasable.


For me it seems rather unfeasible to see a 40mm ball from 40 meters traveling at 80km/h but here we are. So if they can see a 40mm ball, so it shouldn't be hard to see a 20mm dark blob on that white ball. It's not that you have to read...


<div id="gtx-trans" style=": ; left: 580px; top: 243px;"><div ="gtx-trans-icon">


You are using human qualities to describe what can and cannot be done with high resolution cameras with zoom lenses hooked up to computers.

For many years CBS has set up a super slomo camera to analyze golf swings during pro golf tournaments. It is a two camera system that captures at 6000 fps. You can see the logo/dimples on the golf ball rotating.

It is reasonable that if you take a similar system and moved it back and used a zoom lens, you would still be able to resolve the ball logo. If the resolution isn't high enough, get a higher resolution camera. Going to 4k or higher is not a problem for pros.

For tt, they do not need to capture a "vast hall", only the part that is interesting. The table area plus a little. 2 cameras allow them to triangulate the ball position.

There are other things that can be done to enhance the contrast to help track the ball spin. I don't think they need to bother with these, but these can be easily done.

1) Capture in infra red. The white part of the ball will be different temp than the logos, so the logos will have much higher contrast, making them easier to see.

2) Post process the image to increase contrast, getting the same results as above. Anybody can try this by opening a random picture in a photo editor playing with the contrast/picture settings.



Using existing technology, their data seems reasonable.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote zeio Quote  Post ReplyReply Direct Link To This Post Posted: 06/05/2019 at 2:15pm
From what I've seen, the program processes the images in gray-scale. The cameras are synced and capture at 4K. The images are then fed through an algorithm to determine the flight and whatnot.
Viscaria FL - 91g
+ Neo H3 2.15 Blk - 44.5g(55.3g uncut bare)
+ Hexer HD 2.1 Red - 49.3g(68.5g 〃 〃)
= 184.8g
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Post Options Post Options   Thanks (0) Thanks(0)   Quote stiltt Quote  Post ReplyReply Direct Link To This Post Posted: 06/05/2019 at 2:37pm
All this vocabulary tells me we are getting closer and closer to a real robot player (using a commercial paddle and acting like a real player). Once we can calculate a few hundred times per second the ball position, its rotational speed and axis of rotation, a lot is achieved and it seems that's around the corner. The robot itself is the last mile.
Let's note that all the technology is there to do it all, there is nothing left to invent to build such a robot. The incentive is missing. No money to be made, only prestige.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Simas Quote  Post ReplyReply Direct Link To This Post Posted: 06/06/2019 at 4:09pm
Originally posted by stiltt stiltt wrote:

All this vocabulary tells me we are getting closer and closer to a real robot player (using a commercial paddle and acting like a real player). Once we can calculate a few hundred times per second the ball position, its rotational speed and axis of rotation, a lot is achieved and it seems that's around the corner. The robot itself is the last mile.
Let's note that all the technology is there to do it all, there is nothing left to invent to build such a robot. The incentive is missing. No money to be made, only prestige.

oh, it's coming for sure Smile


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