All my machines built between 2003 and 2007 are fitted with a PIC microcontroller, which is a sort of computer contained in a small integrated circuit. The microcontroller replaces the BBC microcomputer used on the older machines.
Microcontrollers are programmed from an external computer,
then disconnected from it. Next time the power is applied to the microcontroller it will run the program. This allows autonomous designs.
The program generally deals with reading inputs from sensors (distance, obstacles...), and generating outputs to actuators (motors, lights,...), according to routines of varying complexity.
Microcontrollers, being programmable for a large variety of electronic functions, greatly simplify and facilitate electronic design.