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This experimental 4WD robot project was developed during May'20 with its scope progressively extended, e.g., by eventually adding a USB camera - which also involved adding a multi-USB adaptor since the PiZero only has the one USB port. 

The primary aims of the project were twofold:

• first, to establish the main build methods for a 4 wheel-drive (4WD) robot and to explore what advantages there may be in independently powering/controlling each of the 4 wheels; and also
• to establish the software methods for a build that combines:
  • a Raspberry Pi, with its wider and more flexible range of capabilities, e.g. use of a wireless controller through a USB interface; with
  • an Arduino UNO that controls a motor shield with 4 separate/independent motor connections

 

 

To design the physical build, extensive 3D modelling (using FreeCAD) was carried out so that the positioning and detailed alignment of all the key components could be explored (as shown in the images above left and on the right), so that the main 3D printed chassis 'plate' (as shown in the image top right and with a first 'trial print' shown on the left) could be designed in detail with fewer 'trial prints' - which is important since the (admittedly now quite elaborate!!) chassis plate takes more than 7.5 hours to print.

For the software build the overall system approach is for the Raspberry Pi to be the primary controller with the Arduino UNO acting as a 'slave' carrying out various control functions (specifically: drive motor control;  slide switch setting detection; and servo control) from high level 'commands' sent from the Pi to the UNO. This 'command' method uses an I²C interface between the Raspberry Pi and the Arduino UNO and a detailed 'protocol' was being developed for the 'command' syntax/structure, how the commands are sent from the Pi, correctly interpreted and acted upon by the UNO, and then any associated response sent back to the Pi.

 

The key attributes of the build were:

• Raspberry PiZero powered by a 5V rechargeable 'power bank'
• Arduino UNO with a 'motor shield' - both powered by 6x AA rechargeable batteries
• 4 motors each independently controlled by the UNO
• I²C link from the Pi to the UNO
• small 64x128 OLED, I²C controlled by the Pi, to provide rolling visual 'robot state' information
• 3V version of the common HC-SR04 ultrasonic sensor - with its powering/signalling controlled by the Pi
• USB camera, controlled by the Pi, to allow images to be streamed to a browser from the moving robot
• 3-port USB + ethernet adaptor for the Pi
• mini servo motor, controlled by the UNO, to allow both the ultrasonic sensor and the USB camera to swivel
• 4 slide switches used to 'set' different operational modes that are 'sensed' by the UNO
• USB wireless dongle connected to the Pi that enables 'wireless controller' use

 

The images below show the finalised build:

 

  

 

 

 

 

 

 

 

 

 

 

 

 

Robotics projects:

 

 

All the currently available maker project information: