A project for exploring a map as grids using e-puck 2. The robots use sound for communication, encoded to different range of frequencies. This project doesn't require any additional devices to work.
First, the robot will enter a connecting phase to register all the available robots. After the connection phase is complete, the robots will explore the map. While exploring, they will use sound to communicate which grid they will explore. Each robot will keep track which grid is already explored.
Features from e-puck2 that we use:
- LEDs
- Motors
- Speakers
- ToF sensor
- Microphones
In the main branch, there are PC side and Robot side implementation of the algorithm. The PC side is in Python and requires a PC with bluetooth to connect the robots. The PC act as a center entity. On the other hand, the Robot side development allows the robot to communicate with each other using sound without any center entity. In the Robot side, we only use the C files since we haven't found a way to assign functions to different threads in C++ using the ChibiOS library.
- Exploration with fixed map (indicated with map) (See Fixed-Map)
- Exploration with non-fixed map (indicated with dmap) (See Non-Fixed-Map)
The connecting phase for both of programs are identical. Here, the robot will produce a sound (~2100Hz) for 1 second and wait 5 seconds for a reply (~2100Hz) from other robots. The 2nd LED (blue) indicates the time for the robot to hear the reply. As soon as the receiver robot hears the sound in this time frame, the receiver robot will register the sender robot as predecessor robot (starting from robot ID = 1). If the receiver robot hears another sound, it will register this new robot with ID = 2, etc. The 1st LED will be used as an indicator for registering the robot. Everytime, the receiver robot hears a sound, it will reset the 5 seconds timer.
After 5 seconds has elapsed, the robot will register itself to the list of the robots with new ID and then the robot will wait again for 5 seconds. In this time frame, when a new robot is turned on, the robot will hear a sound from that new robot. The robot will also produce a sound for this robot as a response to let the new robot know that there is other predecessor robots. The 4th LED will be used as an indicator for this phase.
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For the fixed map
The initial position would be (1, ID). To change the size of the map, please refer to map.h.
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For the non-fixed map
The initial position would be (ID - 1, 0)
Where ID is theID of the robot (starts at 1).
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For the fixed map
First, the robots will check whether the map is already completed. If it's not the case, the robot will check if it's the robot's turn (First free robot in the list). If it is, the robot will find the nearest coordinate and broadcast it. By broadcasting the coordinate, the other robots will remove this robot from the free robots and mark the target coordinate and the path it uses in the map. This is to make sure that there won't be any collision. After broadcasting the coordinate, the robot can now move in the map and other robots can also start working. After moving, the robot will wait for the situation to be quiet, and it will broadcast that it's done working. The other robots will mark the previous path as explored. This process will be repeated until the map is complete.
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For the non-fixed map
The only difference here is the robot will make a 360° rotation before exploring to check for an obstacle in front of the robot and for each 90° rotation. The robot will then broadcast if it is an obstacle or an unexplored grid. After the broadcast, all robots will mark the map according to the information sent.
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For the fixed map
The robot will check whether the map is complete. If it isn't, the robot will try to listen for the sound. The robot will hear 5 beeps as the following:
X XX XX Robot ID Position x Position y Sound frequencies that we use:
- 1200Hz - 1400Hz : 0 (indicated by LED1)
- 1400Hz - 1600Hz : 1 (indicated by LED3)
- 1600Hz - 1800Hz : 2 (indicated by LED5)
- 1800Hz - 2000Hz : 3 (indicated by LED7)
- 2000Hz - 2200Hz : Done working indicator (Indicated by body LED)
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For the non-fixed map
The difference is we use separator here, and we encode the information in binary due to the instability when using more frequency ranges.
X X OX X OX X Robot ID Separator Position x Separator Position y Separator Where O indicates the number sign or when the broadcast is done.
- 00 : Positive sign (+)
- 01 : Negative sign (-)
- 11 : Broadcast done
Sound frequencies that we use:
- 1200Hz - 1500Hz : 0 (indicated by LED1)
- 1500Hz - 1800Hz : 1 (indicated by LED3)
- 1800Hz - 2100Hz : Done working indicator (indicated by LED7)