Terminology_Definitions - rmu75/linuxcnc-wiki GitHub Wiki

date: '2005-12-11T07:31:48' title: Terminology Definitions

Started with a copy-and-paste from an email from Les Watts to the Developer list:

"Sometimes there is terminology confusion with this stuff, so could we define terms as follows? I know we are all familiar with the functions, but might call them different names."

  • Trajectory planner: Program for calculating a path based on typically G code input or cannonical functions. Normally deterministic, since the source g-code is time invariant.

  • Interpolation: technique used by a trajectory planner to assign positions in between (gcode) waypoints.

  • PID controller: Works by comparing current position, vel, etc vs time to the plan created by the trajectory planner. Must be real time, because perturbations are not known.

  • FF: Terms teaching the contoller the dynamics of a machine. In the limit, if FF were a pefect represntation of a machine's system function, it could run open loop with no errors. If the machine dynamics are time invariant, FF is deterministic and does not have to be RT. I note that typically machine dynamics are not time invariant though in the general case because the load at the end effector has an unknown mechanical impedance.

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