STEP 9: MEET AND GREET WITH OUR MAIN COMPUTER
Our rover will use two computing elements: The main computer is the Raspberry PI. The Raspberry PI will receive commands from the remote control station via it's WIFI interface. The operator can send waypoint coordinates and instructions to the rover. All commands end up in the Raspberry PI board, the Arduino computer has no direct connection to the operator.
The Raspberry PI Computer will also use information from the camera and the ultrasonic sensors to analyze obstacles in its near environment to decide which way it will use to get to the next waypoint. The main computer will then send the basic drive commands (which we have developed in STEP 7) to the Arduino board to direct the rover to it's target.
Furthermore we will use the Raspberry PI to implement some very basic odometry strategy: To be able to get the rover to its designated target point, we need to know where we are right now relative to the position we want to reach. Since we have no sensor which could tell us where we are right now (like GPS) we will try to guess where we are: each driving command moves the rover a more or less defined distance (forward/backward) or turns it to some roughly defined degree to the left or to the right. With some simple geometric calculations we can than compute our current position (in relation to our starting point or in relation to the target we want to reach).
It will be subject to testing if this odometry strategy delivers accurate enough information or if we need to support the system with more directional information (coming from an IMU and/or magnetic field sensors).
Which parts do I need?
1 x Raspberry PI 3B+ board (or newer) 1 x case for the Raspberry board 1 x USB -C power supply (2,5 A mimimum)
What needs to be done?
Get the Raspberry up and running. There are many online tutorials which cover this topic, important steps are as follows:
- Download the latest version of Raspbian.
- You will be needing an image writer to write the downloaded OS into the micro SD . You can use the "win32 disk imager".
- Insert the SD card into the laptop/pc and run the image writer. Once open, browse and select the downloaded Raspbian image file. Select the correct device, that is the drive representing the SD card. If the drive (or device) selected is different from the SD card then the other selected drive will become corrupted. So be careful!
- Once the write is complete, eject the SD card and insert it into the Raspberry Pi and turn it on. It should start booting up.
Please remember that after booting the Pi, there might be situations when the user credentials like the "username" and "password" will be asked. Raspberry Pi comes with a default user name and password and so always use it whenever it is being asked. The credentials are:
login: pi password: raspberry
How much do I have to pay?
1 x Raspberry PI 3B+ board 36,50 1 x case for the Raspberry 4 7,00 1 x USB - C power supply 6,00 ============================================= Total 49,50 €