Sports tech: Table tennis technology
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It’s just a bat, a ball and a 9ft by 5ft table, but even in a sport like table tennis, technology can still play a part.
The individual Table Tennis World Championships take place in Dusseldorf from 29 May to 5 June, the seventh time Germany has hosted the event. When Germany’s first Championships took place in Berlin in 1930, players used hard bats without rubber cushioning. A bit like those found in cheap table tennis sets we used at home in the dining room.
These bats didn’t generate much speed and spin, meaning that past players preferred defensive strategies and rallies went on and on, like ping pong chess. At the 1936 World Championships in Prague, the first point in a match between players from Poland and Romania lasted two hours.
Subsequent changes in blade and bat surface technology have transformed the sport into the high-speed spectacle it is today. These days, top players hit the ball at up to 70mph and can impart 3,000 revs per minute spin. To do well at major tournaments they must combine agility and fast reflexes with the chess-like acumen of their predecessors.
Aled Howell, national coaching and education manager with Table Tennis England, the sport’s national governing body, thinks although table tennis is behind other sports in its use of performance analysis technology, the nature of the sport makes it ideal for technological innovation.
“Table tennis is such a fast-moving sport, it’s difficult to get quick readings during a game,” he says. “Technology that can work out where points are won and lost to give a performance review would be very useful.”
Thomas Mayer, a former student at Germany’s University of Design Schwäbisch Gmünd, has developed a smart, interactive table-tennis table which uses augmented-reality technology to show players where they need to hit the ball and where they actually hit it.
Mayer set up an ordinary table-tennis table, installed two PlayStation CL-eye cameras to track the ball in real time, and a full-HD Projector to send information captured to the table in the form of data visualisations.
With these, players can track the direction of their shots. The technology also stores player stats, to help them measure progress. “We had to design a functional interface that takes player ergonomics into consideration,” Mayer says. “It’s a more intuitive way of practising the sort of sequence of shots a player would need to use in an actual game.”
Former Commonwealth silver medallist and elite table-tennis coach Craig Bryant thinks this sort of technology can bring a player’s shot accuracy and consistency to their attention. “Without that awareness, a player might not think about the quality of the ball that they’re playing,” he says. Bryant is concerned, though, that too much reliance on data could leave participants with information overload.
Howell adds that technology which gives instant feedback about performance is useful.
Table tennis might be a simple sport compared to some in terms of rules and repetition, but wherever competition and standards drives performance, there’s a role for technology.
In 2013, French researchers designed a motion-sensing system that provides real-time feedback by installing accelerometers and a gyroscope in the bat handle. Last year, German academics tried using piezo-electric sensors to analyse the performance of different table-tennis bats by measuring vibration and impact forces.
Swedish manufacturer Stiga has put sensors into a table-tennis table to enable tracking of the ball bounce and keep score automatically.
Chinese researchers are devising their own intelligent scoring system, which also includes vibration sensors in the net and an LED panel to display the moving ball and calculate scores.
Then, of course, there are training robots, which are mechanical devices that send out balls for players to practice shots and hone reflexes.
The cheapest robots sit on the table and serve balls at varying speeds. Mid- and top-range models come with nets that retrieve the balls so they don’t go all over the floor. Most can deliver balls with topspin, backspin and sidespin. The more expensive models can also tilt up and down to deliver lobs and serves, or float the ball up.
Bryant thinks robots are useful for beginners who need to improve technique and consistency and for elite players to practise a specific shot. What they don’t do, he adds, is provide realistic match practice. “A human opponent can impart different amounts of spin and directions that a robot can’t,” he says.
Some training robots are programmable, so they don’t fire the ball out in the same way and the same spot, over and over again. Trainerbot, for instance, can be programmed via smartphone to send the ball to any area on the table, or a combination of areas. The app enables players to design their own games and drills.
Bryant believes players still need to practise against other people. “The robot doesn’t give any cues, like a person does,” he says. “The person’s body shape or wrist would change for a specific shot, and that’s what a player reacts to – a human opponent returns one shot with a bit of spin, then the next with a lot, or at different speeds. Reacting to these variations is part of the game.”
Howell adds: “Players work out how much spin their opponent puts on the ball by hearing the sound it makes when it’s struck with a bat.”
There is one robot that does hold its own bat. The Omron Forpheus robot (Future Omron Robotics Technology for Exploring Possibility of Harmonised Automation with Sinc Theoretics) looms over the table-tennis table like a giant spider and uses robotic arms to manipulate the bat.
Earlier this year, Forpheus made it into the Guinness World Records as the first ever robot table-tennis coach. It uses vision and motion sensors to gauge a player’s movement. Cameras positioned above the table monitor the position of the ball, and the robot’s AI determines the human player’s skill level by analysing speed, trajectory, rotation and body motion. The robot then uses that information to provide an appropriate return.
Howell believes robots, smart tables and other such technology might be useful to encourage more beginners to take up the sport, but insists that playing against other humans is what makes elite table-tennis players better.
Unfortunately, Omron isn’t planning to commercialise these robots or make them available to table-tennis players throughout the world. The firm just used this particular sport as a way of demonstrating human-robot interaction.
Not that Forpheus would ever catch on as a playing partner for recreational players, unless someone designed one short enough to fit under the living room ceiling.
And that could also retrieve the ball from under the sofa.
Even if someone did produce such a robot and anyone other than George Clooney, a big fan apparently, could afford it, who would actually want a giant metal spider looming across their living room?
Manufacturing the bats
Swedish bat-maker Stiga has just released its seventh and last bat for the year, Arctic Wood. They’re not saying much about it yet, other than it’s made from, you know, arctic wood.
Stiga has six different technical specs for its bats, seven specs for blades, ten different rubbers... and that’s just one company. There are hundreds of ITTF (International Table Tennis Federation)-approved rubbers and hundreds of different blades. Elite players have them designed to meet their own specific style of play.
Table-tennis bats have come a long way from those old rigid wooden things covered in thin, pimpled rubber.
Modern bats have a spongy sub-layer under a high-friction surface, which increases the sideward force between the paddle and the ball. The spongy sub-layer provides increased contact time and contact area.
Manufacturers alter speed, spin and density of their rubber to fit individual styles. Butterfly, for instance, has 44 rubber specs. Some have pimples facing inward, providing a larger contact area and enabling the player to impart more spin. Others have pimples facing out, which means the player is less affected by spin from their opponent – it has a smaller contact area and the ball stays on the bat for less time.
The blade provides the bat with a solid foundation. Some blades are made from wood, others from composite carbon and wood. In general, carbon blades work well for fast, attacking play. Slower, defensive players or beginners might prefer a wooden blade.
“I’m an attacking player and my backhand is more aggressive,” Howell says. “Therefore the rubber on the back is harder and quicker.”
Bryant adds that an elite player needs to know their method and what sort of bat complements it. “Get the wrong bat and a player might have to adapt their style, which could cost points,” he says.
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