Best current solutions 
 
General architecture is hierarchical, with specific stages optimizing in complementary manner scope, coordination, agility and specialized functions; from PC (supervisory level, for task-oriented strategy and human communication) down to focussed units (servocontrollers, PLC, smart cameras, laser scanners, audio devices, etc.). 
 
Hardware architecture: Star (internal) communication system, with Ethernet hub or switch; and USB hub. 
 
Past solutions 
 
RS-485 
 
Multiplexed parallel (incl bidirectional multiplexers)