Automated Coal Terminal

This is my biggest and most complex automation project so far. Three coal trains are parked in a train yard. From there the system makes trains run and load coals in one of the two coal loading silos. After that the trains can be parked again to be unloaded later on. The whole layout is one big loop and because of this, continous loading/unloading is possible. That was also the whole idea: "recycling" of coal needed to be possible. The silos are filled with the coals from the unlading area, by conveyors and an excavator. The image below shows the layout of the system.
automated-coal-terminal-with-tracks-and-train-yardThe red loop is a passenger train loop, which runs three passenger trains. This system is a completely separate system. Also the crossings are automated, also these are stand-alone. The blue loop is the loop that the coal trains follow. The complete system has the following control systems:
- 1x Passenger train controller
- 2x Rail crossing controller
- 2x Load silo controller
- 1x Unload station controller (main controller)
- 1x Air compressor (on/off hysteresis control)
- 1x Excavator controller
- 1x Crane controller (inside red building)

The whole system has just over 100 I/O points (inputs/outputs connected to the control system). Using connectors, I was able to make the system somewhat modular. I needed to build the system upstairs in a small bedroom, while the complete system would be installed in the cleared out living room (5.8x2.8m). Below an image of the central control system, including power distribution and motor controllers. The different connectors bring power en communication signals to the subsystems (unloading area, silos and train yard).

Loading procedure
The trains are stopped with the first wagon under the silo for the loading procedure. This point is determined by a proximity sensor. When the sensor returns the value that the train has arrived, the voltage on the rails is reversed for a short amount of time, to break the train and make it stop directly. By doing so, the stopping point is more accurate. The silo has a hatch at the bottom. This hatch opens three times for just a second. This way the dosing of the amount of coal that falls into the wagon is more accurate: leaving the hatch open for a longer time results in a high flow of coal that would overflow the wagon below the silo. I tried making the hatch smaller, but that resulted in a lot of clogging. Already with the current hatch size, clogging was a problem. To encounter this problem, I installed a pneumatic piston that drivers a Lego Technic axle through the coals just above the hatch, prior to opening the hatch. The axle removes any clogging (see image below).
driving-axle-siloWhen the first wagon is loaded, the silo controller moves the second wagon below the silo. This is based on a time delay. The same loading procedure is executed again and the same is done with the third wagon. When completely loaded, the silo controller signals to the main controller that the train is ready to leave. The central controller decides what to do with the train (park in the train yard or unload it immediately). When there are no other trains on the track, the central controller gives a signal to the silo controller that the train can leave.

Unloading procedure
The most complex part of the system is the unloading terminal. A train loaded with coals is stopped at an accurately chosen point. Here pneumatic pistons push a conductor to the bottom of the coal wagon, where there's also a conductor. This makes a connection between the central control system and the motors inside the coal wagons. The coal wagons contain a Power Functions M-motor which drives small linear actuator which opens/closes a hatch at the bottom of the wagon. Once the connection is made, the central control system enables a voltage on the conductors, which make the motors in the wagons run and which opens the hatch in the bottom of the wagon. The result is that the coals are unloaded through the gaps in the rails on a conveyor below the rails. The coal from the first two wagons unload to a central conveyor, which fills one silo. The coal from the third wagon is unloaded into a container. The coal in this container is scooped out by an excavator and is dumped in the other silo.

The empty train is transferred back to the train yard and the cycle can start again.

Youtube videos

Main video

Extra footage video

How it works: layout and load procedure

How it works: unload procedure

Fails during commissioning