Table tennis robot

Unfortunately it is a long time ago that I wrote a blog post. I was on the way to build a mowing robot.

On the way I had to invent a lot of things. Some of them are:

• For Pi4J:
• Pull request - Added MCP44xx, MCP45xx and MCP46xx families to pi4j-i2c-devices
• Pull request - New Concurrency in I2CDeviceImpl and I2CBusImpl
• AVR-projects:
• Eclipse-Plugin - Use usbasp programmer to show up UART in Eclipse
• Gadget - A silver screen remote controller

But since I could not tell my wife when the mowing robot will mow the gras in our garden, she did not want to wait any more and I had to buy a ready-to-use product. And yes, it mows the garden.

So what now?

In the last fall my sun started playing table tennis. Due the fact that this is some sort of "farther and son"-thing I also learn table tennis. And after the first lessons I recognized that it would be fantastic the use a table tennis robot for the training. A robot would be able to place every ball to the same spot, with the same speed and the same spin. So you can focus on refining your technique. As always you can buy a cheap model which won't make you happy on the long run or you take a lot of money and buy a good model. Or, you DIY :-) ... which not necessarily means that you will be happy on the long run :-)=)

In the very beginning a saw a lot of Youtube videos showing DIY table tennis robots. But I also looked videos of professional robots to get inspired. And after a couple of days I knew that I want to build a robot which one day might be better than professionals. But step by step: 

1. The first "version" should be similar to those cheap models: They sit in the middle of the table and shoot the balls to the left, to the middle or to the right. The cheap robots only know top-spin oder under-spin. My robot should be able to create every spin (top, under, left, right, combinations). Additionally it should also be able to shoot faster or slower in combination with up- and down-directions. And, of course, a ball recycler: A net which collects all the balls I return during practicing and brings them back to the robot to shoot them again.
2. Once this works I want to build a rail on which the robots moves. This should enable an advanced training mode and generates shoots like a human player would do. Additionally the ball-cannon should be able to move up and down. Especially for this version I can reuse a lot of things I already bought for building the mowing robot.
3. And in the end I want to add a RaspberryPi camera module to track the ball and move the robot not only in predefined ways. It should move along the returning ball to shoot the next ball from the place the returned ball hits the collector net. This should give a feeling as playing with a person.

In the last three months I tried some of this features to see whether I could make it. And yes, it seems to be makable. So I will report about the progress, the problems and the solutions in the upcoming posts.