Y&T S-27 table tennis robot

You go back, Jack,
do it again...
wheels turning
'round and 'round
You go back, Jack,
do it again...

I have a Y&T S-27 programmable table tennis robot.

It is a high-end robot made in China. In 2010／2011, it was considered state of the art. I bought it in Zhongshan (中山), China back in 2010 and had it shipped home.

I only take it out about once a year because I prefer to play with people. Human beings have more natural variation, which can be both a blessing (helps train adaption) and a curse (inconsistency). The other big problem with the robot is that it doesn't have arms: you cannot see it swing at the ball like a human being. A large part of anticipation is seeing how the opponent reacts to and contacts the ball. With the robot, the balls just shoot out almost without warning from a tube.

Last night, for the first time in over a year I used the robot to do a drill. (Usually, I'm fortunate enough to be able to find players to come out and hit with me.)

I programmed a drill asking the robot to send alternately one topspin ball slightly to the right of the centerline (position 7) and one to the forehand corner (position 10). One from each physical robot head. I asked it to send 40 balls and stop. (As the video belows shows it actually sent 41 balls.)

The way these robots work is having a spinning motorized roller shoot balls from a tube. The more sophisticated robots use two rollers. The spin and speed of the ball is determined by two (orange colored) spinning motorized rollers: one that brushes the top of the ball and one that brushes the bottom. You get topspin if the upper roller spins faster than the lower one, and underspin if the lower one is faster.

I set the top motor to speed 6, and the bottom to 1. This means the balls comes to me already loaded with topspin. The higher the speeds, the faster the balls.

The frequency of ball delivery was set at the 2nd slowest setting. This produced balls at the rate of 1 per 1.75 seconds. That gives me plenty of time to recover between balls, and perhaps approach the ball a bit more deliberately instead of frantically trying to keep up and reacting like a headless chicken. And as I get used to the drill and learn to anticipate the ball, cognitively I'll be less overwhelmed, and be able to work on improving my form. At least, that's the theory...

The control panel settings are shown in the picture below (left side for left head, right side for right head):

I'm currently trying to retool my forehand loop stroke. In the following video, I'm practicing my counterloop; that is, I return the incoming topspin ball with topspin. Fight fire with fire, so to speak. I'm only partially there. I'm trying to backswing less these days. This saves precious tenths of a second. And I'm think I'm finally succeeding in this aspect.

(There are other strokes possible. For example one could simply block the incoming topspin. Especially if one has less time. See my earlier post and video with Crystal Huang here.)

Also, having the robot send balls alternately to different positions helps me train my feet to respond properly. I have to move. And keep my balance. Loop. And then not have my loop stroke throw off my balance because I need to respond to the next ball. Multiple small hops are vastly preferable to a single larger step because this allows for fine-grained adjustment. You'll be surprised how many hops are possible in half a second.

Maintaining balance conflicts with how strong you can counterloop. The momentary stop for balance on the right leg, and the waist twist and weight transfer are crucial aspects of this part of the counterloop equation. Although my loop percentage rate is satisfactory, judging by the video clip, I could improve quite a bit on the quality of my loop.

Link: here

Moreover, my followthrough is not where I want it to be at the moment. This affects the amount of power delivered tremendously. It's way too much to the right, crossing the imaginary centerline of my body. Where the stroke finishes also affects recovery time. This is a stroke error. Instead I'd like it to finish with the paddle more out to the front. Technically, I also need to work on holding onto the extended stroke position momentarily at the end of the stroke. I automatically drop the paddle at the end of stroke which prevents proper transitioning. This is another error.

These are all good reasons why you want to resist the temptation of setting the machine to shoot as many balls per second as you can cope with. It makes good sense to debug the stroke fully before increasing the tempo.

In summary, the robot is not just useful when you can't find anyone to play with, it's also a good tool for reprogramming muscle memory. The problem of course is making sure the new program being written is a true fundamental improvement over the old. That's where video analysis is extremely useful.

A lesson with Crystal Huang: two left feet

This is the third entry in my continuing series about learning table tennis technique with Crystal Huang, a professional table tennis coach. These video clips were taken at the LATTA last weekend. (Previous entries can be accessed here: #2 too many degrees of freedom and #1 structural reform.)

Have you ever had the experience of attending an aerobics class at the local gym but came away discouraged, feeling utterly unable to follow the moves? If you understand what I'm referring to, you might empathize with me. If not, I envy your natural talent.

The video here will demonstrate that I am a particularly embarrassing example of two left feet. Since footwork is paramount in table tennis, this is a very big developmental challenge: a potential showstopper. In fact, it will become apparent that I can't even figure out a simple two point five step move even when it is repeatedly demonstrated right in front of me. Thank goodness for computer software, only when I viewed it frame by frame did the proverbial lightbulb go off in my head.

The specific challenge here is to move in correctly when the ball is played short to the forehand. Generally speaking, we have about 1/3 of a second to respond appropriately. Proper footwork is essential to getting in close enough to execute a decent flip, smash or push stroke over the table. Possessing a good stroke is useless without the necessary accompanying footwork. Rather like being all ready to ski without an appropriate vehicle to get you up the slippery snow-covered roads to that mountain that looks so good in the distance. Not sure that's the best analogy but, in table tennis, speedy footwork is needed to deliver us in about 2/10ths of a second close to where the ball bounces while retaining good body balance. And proper balance is needed to support good stroke execution and facilitate recovery.

Because this is all about movement, let's go to the video directly. We begin with the following drill:

Here the instructor stands at the top right corner of the diagram. The ball is blocked randomly to my backhand and forehand. I'm having trouble getting close to the forehand ball, especially when it bounces short near the net.

I have taken the liberty of adding commentary and translation where appropriate so you can follow Crystal Huang's instructional style. (For those who prefer to skip forwards, minutes 8:19-9:26 is where I'm utilizing the footwork in point play.) Also, since the video is a bit long, you might want to click on the "I" icon and set the resolution to 360p for a faster download.

Link: here

As should be clear from the video, my clumsiness resulted from my lack of understanding of how to perform the step, stop, step sequence. That is because I didn't understand what was really happening in real time. For those as translationally challenged as me, let me offer the following frame-by-frame explication. Thank goodness for video editing software.

(A)

(B)

(C)

(D)

(E)

(F)

(G)

(A) is the starting position.

In (B), body weight is shifted to the right.

This unweighs the left foot, which allows it to move towards the right foot, as shown in (C).

You can then stand on the left foot in its new position, and unweigh the right foot. This is shown in (D).

Then it's just a matter of picking up the right foot and placing it in under the table. This is exhibited by the sequence (E) through (G).

Notice the racquet arm does not move until (F) and (G). In other words, you don't backswing first and move later.

At (G), the weight is transferred to the right foot. Next, we need to lean the upper body over for reach when the ball lands short or close to the net. The left foot may go back a bit to counterbalance the torso lean. The free arm is often also used for this purpose.

Finally, one more critical point that may not be immediately apparent to some ping pong students is the fundamental idea to always pause momentarily and re-balance first after moving before hitting the ball. In this case, this would be just after the lean over from (G). That slight pause for balance makes all the difference in the world in making the push or flip stroke crispy (my terminology), i.e. much more effective.

If you need it, here is the video version of the frame sequence:

Link: here

Ping Pong in Hong Kong

I've never played ping pong in Hong Kong before: basically because I don't know anyone there. Instead, I've always gone into Shenzhen next door to play and get coaching as documented elsewhere in this blog.

(I know there are private clubs and municipal gyms for those who can book tables in advance, but I'm not plugged into the Hong Kong table table community.)

Well, all that changed this winter. Through networking, I managed to visit facilities at two universities in Hong Kong. In future, I'll definitely be playing at these locations whenever I get the chance.

City University

As the name suggests, this is in the "city" so to speak. Easily reached by MTR train (East Rail line) or subway (Kwun Tong line, 觀塘綫), Kowloon Tong (九龍塘) station, I played here twice.

My contact and generous host was Prof. Leon Zhao, head of MIS at CityU (pictured here on the left). Incidentally, I have met Leon previously in a professional capacity as we served together on a Ph.D exam committee, though I never knew he was a ping pong player. It's a small, small world, isn't it?

You need a guest pass and someone affiliated with CityU (in my case, Leon) to get into their sports centre. Cost is HK$20. There is a dedicated room for ping pong and nice new-looking tables.

They have a club and CityU team. Plus a semi-professional coach, Eddie Wei, standing to the right of me below:

(From left to right: Ye Liu (Ph.D student), Yikshing Yeung (CityU TT team member), me, Eddie Wei (coach), Haibin Yang (Professor), Wansan Lee (high school student who trains there, seems like 2500 level player) and Enyu Zhuang (Ph.D student).)

I had a lot of fun playing there playing with as many people as possible. Very cool bunch of guys.

Chinese University of Hong Kong

I also had the opportunity to play at the Chinese University of Hong Kong. With a large uncrowded campus up on a hill, this is not in the city by any means. It has a MTR train (not subway) station, simply called University (大學), on the East Rail Line.

So it's not surprising they have a larger gym with very high ceilings and good lighting. 6 tables.

Very spacious by Hong Kong standards, it's a nice facility with room to back up and lob a bit.

I played a bunch of professors but this guy pictured below is the staff champion. He's a PE instructor at the university. I tried hard but he beat me 3-0 convincingly.

You need to be affiliated with the university to play here. My contact and host here was Jimmy Lee, professor of computer science.

Like me, he is a computer science professor. We both play ping pong and train to run marathons. I even own the same exact ping pong shirt he is wearing. Obviously, a great guy with the right set of hobbies! :)

Doha: CMU Qatar

After the social robotics conference in Amsterdam (see here), I spent a week at Carnegie Mellon University (CMU) Qatar.

I last blogged about CMU Qatar back in 2009 when I took a bunch of spherical panorama pictures (see here). This time I also brought my equipment but unfortunately had no time to take more of those special images. In particular, I had hoped to get a 360° shot of the following open seating area inside the building:

Unfortunately, this time half the space was set up with regular chairs instead of those awesome cushions. Maybe next time.

The building itself is quite opulent and certainly impressive, more reminiscent of an investment bank than a university. It has huge atrium-like open spaces that I find too big to be friendly. Designed to awe, I find it lacks human scale.

(I think of grand entrances on Arrakis designed to reduce the human to a mere mote, as described by Frank Herbert in perhaps the book God Emperor of Dune. It has been really many years since that read that series. Who has time these days to read a few thousand pages?)

My favorite room was the faculty lounge, not only because of the espresso machines but also because it has a nice friendly yet contemporary feel with proper wood floors instead of the echo of polished hard marble, artfully concealed indirect lighting and absolutely wonderful proportions. I'd love to have a house with a central living area like this. Dream on.

(Actually, if you look at houses like this one in California, you could make it work.)

Despite the luxury of having uniformed waiter service at my office, I often preferred to make the trek down to the faculty lounge myself.

The infrastructure is important, but in the end it's the personal touch that matters. My hosts made me feel supremely welcome.

For example, one of my sponsors drove me from the hotel to the university each morning until he got sick. After that, I rode in on the QIA Hummer H2:

I even met a ping pong enthusiast from Brazil, Prof. Marcelo Castier, a chemical engineer from Texas A&M University. An extremely busy man, but he managed to find one hour to hit a few balls with me at the brand-new student center the day before I left Doha.

They have three KillerSpin tables there:

Unfortunately, the polished floor is extremely slippery, the pool tables get in the way, and one is blinded by glare from the wall of windows from one end. But hey, these seem to be the only available ping pong tables.

Watermelon and Tenergy

If it's watermelon slices and Tenergy rubber, it must be Open House at my Ping Pong Palace (aka my house), see here. Taken with the Olympus E-P1:

As my friends played at the table, I went outside to enjoy the cool late autumn air, and a great sunset.

Unfortunately, it's a shame I used my iPhone 4 to take the sunset photo instead of having my Olympus E-P1 at the ready. The picture of course is way worse than what is possible with my E-P1. The problem being that one has to capture the moment with whatever tools one has at hand. A few minutes later, when I went inside to grab my Olympus, the sunset had already deepened almost into darkness.

My only saving grace was that I had the presence of mind to activate the iPhone 4's HDR mode. Without a tripod, inevitably blurriness is introduced. It came out okay at web resolution. But it cannot stand enlargement or viewing on larger screens.

However, it's still immeasurably superior tothe non-HDR, i.e. regular iPhone 4 mode. See below:

Blow-out in the highlights, noise and lack of gradation at the lower end irretrievably mar the snapshot.

bad sneakers, do it again

Imagine, if you will, my car smoothly eating up the miles in the desert on I-10. I'm on my way home from Los Angeles.

A mere press of the window lift away, it's over 110F (43C) but inside, it's deliciously cool and quiet. As the sun reddens behind me, I settle into the cooled seat which will be my home for the next six and a half hours. Relax, connect up the iPhone, in seconds I'm down in the world of Steely Dan's sophisticated mix of jazz and melancholy.

As the doubtlessly well-informed reader that you are, you already know I'm listening to them from the title of this blog entry. I reflect on what has been a good visit.

Five names that I can hardly stand to hear
Including yours and mine, and one more chimp who isn't here
...

That's how the song Bad Sneakers begins. For a moment, I think back to New Jersey days. Those Butterfly 808 table tennis shoes pictured above look brand new but are over 12 years old. Having languished in a dark box for all that time, they are essentially new, unused after I ordered them back in the late 1990s.

I figured it's about time these "sneakers" emerged into the light again. Since I've restarted table tennis, I've stuck to my marathon running shoes for cushioning and comfort. I've been re-purposing my Newton Sir Isaac neutral guidance trainer (see picture at the bottom of my prior entry A Half Marathon). You may be surprised to know these Butterflys (538g) are heavier (and offer less protection) than my Newton neutral racers (500g).

(Out of all the sports I dabble in, my bicycle racing shoes are by far the lightest, at around 320g. Yup, one Butterfly shoe is nearly two bicycle shoes.)

But, as the saying goes, it's very much horses for courses. Those Butterfly shoes have a very low heel (to protect the ankle) and (by design) a natural rubber sole that balances the ability to slide and make small adjustments with grip. With respect to cushioning (to protect against fatigue), let's just say they work best with a professional (cushioned) floor that the best clubs have.

As long as we're talking numbers here, have you ever wondered why cars report the outside temperature but never the inside?

As you can see, the automatic climate control is set for 74F (23C) but the actual temperature at head level is 32.3C (90F) with 12% humidity (it's the desert).
(Notice the fan is barely running. In other words, the car thinks it has reached the correct temperature.)

Back to the coolness of Steely Dan (and Do it again):

You go back, Jack
Do it again
Wheels turning round and round
You go back, Jack
Do it again
...

There are no quick fixes in table tennis (or life for that matter). Old habits are ingrained into muscle memory and die hard. Once we recognize our technical problems, it takes considerable work (i.e. time), dedication (i.e. make time) and a certain kind of optimistic stubbornness (it will come, it will work out, give it time). Those who promise quick and easy fixes are mere charlatans.

When you know she's no high climber
Then you find your only friend
...

I'm not completely sure what some of the songs mean, but people have said this breakout tune of theirs is about addiction, second chances and the inevitability of fate. I muse, hmm, this is my 2nd time around at table tennis. You could say it's an addiction. But I'm not sure what fate has to do with it...

Perhaps then my occasional weekend trips to Los Angeles are about a leap of faith.

1. Dedication: I have to drive 13 hours round trip.
   I prefer it to flying because of convenience. Flying basically involves nearly 5 hours each way counting time spent getting to the airport, parking, going through security, waiting around, renting a car etc., only actually saving 3 or 4 hours round trip. So far, unless I have been driving all night, I have been able to arrive alert and relaxed enough to take a lesson after a short break.

2. Work: to maintain quality, a lesson lasts only 90 minutes.
   Why? Well, multiball is physically demanding. I go through three shirts (sweat saturated), two bottles of water, a Gatorade and a towel in just 90 minutes. Willing the body to continuously move, move, move to get to a position and hold balance, stop momentarily and get the shot off. It's not about mindless or brute force strength. The coaching is intense: every improperly played ball (never mind the missed ones) gets reviewed and highlighted. Nothing is missed. Correct form is everything. Struggling with yourself on a conscious level is also mentally taxing (not to mention, frustrating, at times).

3. Optimistic stubbornness: that's a few sessions per weekend maybe once every other month or three. (That's pretty far from the ideal of training 3 or 4 mornings a week.) It's a legitimate question to ask whether anything can be learnt and retained in such short bursts. Without constant feedback and application, one tends to revert back to old habits.

At this point, I can report that I am finally starting to see glimpses of the promised land. As I mentioned earlier, give it time, it will come. My body is beginning to react and move differently. Because how you move and maintain balance is everything, it affects all aspects of the game. Tension has been transferred from the shoulders into the forearm. Suddenly I go from looping two or three balls to twenty or thirty in a row. They're not all perfectly minted, mind you. But now and then I feel my center of gravity doing the right thing. And it's definitely not the shoes :)

Fundamental change is possible, and on my long drive through the desert, that thought makes me happy.

For match practice, I also play in LATTA's Saturday afternoon's advanced league. Typically, I take a lesson in the morning at 10:30am. Then break for lunch at noon.

(There is a cheap chinese eatery nearly directly across the road. They also serve protein shakes not on the menu.)

Back to the club at 2pm, it's a round robin group format. You play 5 or 6 matches. Because it's such a large club with several leagues, the level on Saturday afternoon is good, all are hardened and experienced players. Competition is ferocious. No match is easy. As I can easily see myself losing every match, I'm amazed sometimes I even manage to win any. After the round robin phase comes the single elimination phase. It all finishes around 7pm.

For example, last Saturday I played a total of 32 games (including 10 straight with a guy who wanted to learn my style and me, his). By this point, I've put in close to 7 hours. I'm tired and ready to book myself a long massage. Despite some lingering fatigue, the underlying fitness is there. I know I can recover in time for tomorrow morning's 90 minute three shirter.

On Sunday morning, I'm a bit stiff but after warming up, it's time to see if recalcitrant muscle memory can be bent a bit more until it yields. After the lesson, it's noon time and I've made special arrangements to play my 1600 nemesis, Zhu Min Ming (see earlier LATTA entry). I've never even managed to take a single game off her but she is kind enough to offer her number and say practice with me. Her consistency and control game is way ahead of mine and her long pips backhand isn't easy to handle. However, this time there is a titanic struggle with long rallies. No matter how many loops I bang in, she always has an answer. But somehow this time is different. I finally manage to prevail and come out 3-1 ahead.

I'm carrying my fortune cookie from last Sunday.

It's an epochal moment. I know I have passed some test.

(I have a sneaking suspicion she makes sure she is perennially underrated. She is almost at 1900 now and needs to start discounting again.)

At lunch, she calls me and says someone is waiting to play you.

It's like something out of an Indiana Jones movie or kungfu novel. It seems Zhu Min Ming has passed me onto challenge number 2. His name is Duc Loi, and he is over 60. Plays every day. Can chop away from the table. Can stay at the table and work you over with placement. His speciality is attacking with the long pips. He is rated over 2200. I am warned even 2400 players lose to him first time around. Of course, I lose 0-3. Like Zhu Min Ming before, he offers me his card and says call me to play when you are in town. I know he is a benchmark. 過三關 and all that. It's definitely like something out of a movie.

Appendix

One of the advantages of Los Angeles is that it is a big city with large ethnic populations. Population density makes for convenience. You can find everything within a 3 mile radius. The Monterey Park/San Gabriel "ghetto" is one such enclave. And local competition ensure low prices and high quality. It almost fully mitigates against the traffic, lack of green, open space and poor air quality that characterizes the area.

There are 3 table tennis clubs run by high level professionals within a mile or so of each other. I've never been to the others. The LATTA is the largest.

I have also established a routine here. I know where to go for what. I typically book the same hotel or another one. I trade off convenience against an oasis of green and quiet perched up on a hill. Either way, it's just five or ten minutes more.

Saturday morning, I go for dim sum before my 10:30am lesson.

Always at the same place (海寶潮粵海鮮酒家), they're open early. No queuing up. And more importantly, they always have my lotus seed paste buns (蓮蓉包) correctly configured with egg yolk. (I'm very particular about that.) And it's pretty good but not expensive. (Okay, whaddya expect, it's no match for 稻香.) Still, no reason to go anywhere else.

I always go to the same massage place (快樂按摩) straight from the club. I choose them because they have a shower so I can clean up first. $25/hr plus tip is the going rate around here.

I know where to go for cheap food. I have a favorite noodle place, a decent thai place. Even the $12.95 sushi place is unpretentious and the taste is fine. Back in town, they'd make a big deal about it. Here, it's just another place. (Okay, it's not Sushi Say (寿司清) Tsukiji main branch (築地本店) in Tokyo, but this is frickin' Southern California, whaddya expect?)

And for the observant, yes, that sign shows $9.99 for one hour foot massage. Amazing isn't it?

Mons, Belgium

It has been a while since I've posted anything about travel. Recently I went to Belgium for an academic conference.

What do you associate with Belgium?

For me, it's a close personal association with beer, chocolate and ping pong.

Well at least, the beer and chocolate are uncontroversial. There is plenty of evidence for these.

For example, in transit in Denver International Airport (DEN), I was immediately confronted with the New Belgian Hub visible below. Add in frites (French fries) and moules (mussels)? Pretty much case closed.

How about the ping pong? Well, on arrival at Brussels airport, I was heartened to find that these posters were very much in evidence. "Be a fan of skill," exhorts the poster. Absolument! Amen, brother.

As I mentioned earlier, I was there for a conference (on the topic of Language and Recursion as it happens). It was held at the University of Mons, bang in the middle of what seems to be a small town of around 30,000 inhabitants. (To compare, the University of Arizona has more students than that.) But even in this modest town there are 3 ping pong clubs. I visited CTT Ecurie Mons, which meets in a high school gym.

It is the middle club of three in terms of size in Mons. They field some 8 teams, with the top team in the Belgian national league (3rd division). Plus, more recently, one women's team. I hit for an hour with the guy on the left. His name is Guillaume. (He seems to be around the 2200-2300 USATT level.) Guy on the right is Laurent. He was the guy who responded to my attempts to contact someone over the internet.

No chance to play people like that where I live. So yes, due to its popularity, ping pong in Belgium can be pretty good even in a small place.

How about Mons itself? Well, it was just a 3 day conference, a short visit.

Let me offer the Grand Place (main square) by day (with the typically grey skies of Spring can you even spot it's 6pm?):

and the Grand Place by night:

At the conference reception inside l'Hôtel de Ville (aka the town hall), the big building in the above Grand-Place-by-day picture:

Let's take a closer look at the mural, which depicts a scene that seems familiar to me.

Once a year, there is a re-enactement of the St. George and the Dragon story in the Grand Place in Mons. Note I used the definite article here. Because I grew up in England, I thought this was an original English-only story. Perhaps the indefinite article would have been more appropriate. Apparently, St. George and the Dragon both might not be so English…

As for the conference? Well, it included all the (free) beer and wine you could drink while ruminating and attempting to think serious academic thoughts.

Seriously. I'm not kidding. All we had to do was flash our badges at the hotel bar. Talk about hospitality. Well then, who's a lucky monkey then?

Patting Le Singe de Mons (the monkey of Mons) on the head at the Hôtel de Ville with your left (has to be left) hand is said to bring good luck.

Finally, back at Brussels airport, the counterpart of the New Belgian Hub I began this post with in Denver, the Leffe Plaza Café

(All pictures taken with my Olympus E-P1 with Panasonic 20mm f/1.7 lens.)