Centralized motion control

A recent trend

More and more often large OEMs and integrators choose a unified automation approach for their machine design. This means that they attempt to have only one “intelligent” device in the machine (a controller), and everything else (motion control included) will be simple slaves of this device. 

The result is a simpler architecture, with better integrated motion equipment. Two major, fairly recent technological advances have permitted such an approach:

  • faster CPUs embedded in the line/cell control PLCs makes them capable of performing the kinematic calculations necessary to control coordinated motion axis, while still keeping their original function of controlling the line/machine.
  • real time, Ethernet-based fieldbuses offer the technical features and performances necessary to the transmission of motion control related messages between the PLC/controller, and the drives.

However, in order to get the best performances out of a robot arm, kinematics are not enough, more complex calculations need to be performed:

  • dynamic compensations of physical phenomena such as gravity, mechanical gear frictions, etc…
  • high end servo tuning for each robot joint.

The question is, how can we improve even more ?