Last few blog posts have all been about heavy docker and Kubernetes stuff. I thought it was time for something more light and today I want to blog about my hobby robotics project again. Before I had robots to tinker with actually I used to play around a lot with trying to automate a model train setup. So recently I had the idea why can’t I combine this and let one of the robots have some fun by playing with a model train 🙂

In this blog post I will use MQTT and my Robot Cloud SDK I have developed to hook up our Nao Robot to MQTT together with the model train.

Needed materials

In order to build a automated train layout I needed a model train setup, I have a already existing H0 based Roco/Fleischmann based model train setup. All the trains on this setup are digitised using decoders that are based on DCC. If you do not know what this means, you can read a about digital train systems here: http://www.dccwiki.com/DCC_Tutorial_(Basic_System)

Hooking up the train

The train system I have is controlled using an Ecos controller which has a well defined TCP network protocol I can use for controlling it. I have written a small library that hooks the controller to my IoT/robot cloud that I have described in previous blogposts. The commands for moving the train are sent to MQTT which are then translated to a TCP command the controller can understand.

I will have a MQTT broker available somewhere in the Cloud (AWS/Kubernetes) where also my robots can connect to so this will be the glue connecting the robot and trains.

I don’t really want to bother people to much with the technicals of the train and code behind it, but if you are interested in the code I have put it on Github: https://github.com/renarj/rc-train

Hooking up the robots

Hooking up the robots is actually quite simple, I have done this before and am using the same setup before. The details of this are all available in this blog post: https://renzedevries.wordpress.com/2016/06/10/robot-interaction-with-a-nao-robot-and-a-raspberry-pi-robot/

In this case I will be using our Nao Robot and hook this up to the MQTT bridge. The framework have developed contains a standard message protocol on top of MQTT. This means the messages are always defined the same way and all parties adhering to this can give states and commands to each other. In this case both the train and robot use the same message protocol via MQTT, hence why we can hook them up.

In order to make this a bit more entertaining I want to run a small scenario:

1. Nao walks a bit towards the train and the controller

2. Sits down and says something

3. Starts the train

4. Reacts when the train is running

I always like to put a bit of code in a post, so this code is used to create this scenario:

private static void runScenario(Robot robot) { //Step1: Walk to the train controller (1.2 meters) robot.getMotionEngine().prepareWalk(); robot.getMotionEngine().walk(WalkDirection.FORWARD, 1.2f); //Step2: Let's say something and sit down robot.getCapability(SpeechEngine.class).say("Oh is that a model train, let me sit and play with it", "english"); robot.getMotionEngine().goToPosture("Sit"); //Step3: Let's start the train sleepUninterruptibly(1, TimeUnit.SECONDS); startTrain(robot.getRemoteDriver(), "1005", "forward"); //Step4: Nao is having lots of fun sleepUninterruptibly(5, TimeUnit.SECONDS); robot.getCapability(SpeechEngine.class).say("I am having so much fun playing with the train", "english"); } private static void startTrain(RemoteDriver remoteDriver, String trainId, String direction) { remoteDriver.publish(BasicCommandBuilder.create("ecos") .item("train").label("control") .property("trainId", trainId).build()); remoteDriver.publish(BasicCommandBuilder.create("ecos") .item("train").label("light") .property("trainId", trainId) .property("state", "on").build()); remoteDriver.publish(BasicCommandBuilder.create("ecos") .item("train").label("direction") .property("trainId", trainId) .property("direction", direction).build()); remoteDriver.publish(BasicCommandBuilder.create("ecos") .item("train").label("speed") .property("trainId", trainId) .property("speed", "127").build()); }

What happens here is that in the Robot SDK there is a bit of code that can translate Java objects into MQTT messages. Those MQTT messages are then received by the train controller from the MQTT bridge which translates this again into TCP messages.

For people that are interested in also this piece of code on how I create the scenario’s around the Nao robot it’s also available on github: https://github.com/renarj/robo-pep

End result

So how does this end result look like, well video’s say more than a thousand words (actually ±750 for this post 🙂 )

This is just to show that you can have a bit of fun integrating very different devices. Using protocols like MQTT could really empower robot and other appliances to be tightly integrated very easily. The glue that I am adding is to make sure there is a standard message on top of MQTT for the different appliances and hooking them up to MQTT. Stay tuned for some more posts about my Robotics and hobby projects.