Method and system for meeting end conditions in a motion control system
One embodiment of a system and method for meeting end conditions of a path plan utilizing a path generator that continuously generates commands for a path plan while tracking the total time expired in the path plan. The path generator computes the time remaining in the path plan and substitutes the remaining time for the length of the final sample period in the path plan when the length of the remaining time is less than the length of a full sample period.
1. A method for outputting a move command in a motion control system to meet desired end conditions of a move, the method comprising:
prior to performing a move, generating a path profile in accordance with desired end condition between an initial position and a final position, the path profile having a known sample period, the move having a plurality of sample periods; and
outputting a move command so that the desired end conditions are met,
wherein generating the path profile comprises:
computing, a length of time remaining to complete the move along the path profile;
comparing the length of time remaining to a length of the known sample period;
substituting the length of time remaining for the length of the known sample period during a final sample period when the length of time remaining is shorter than the length of the known sample period.
2. The method of claim 1 , further comprising:
checking values of actual end conditions at the final position of the move against the desired end conditions of the move.
3. The method of claim 1 , wherein jerk is a constant value throughout the duration of the move.
4. A motion control system for controlling motion of a controlled element so that desired end conditions are met, the motion control system comprising:
a path generator for generating a path profile for a controlled element; and
a motion controller for receiving at least one move command from the path generator and outputting them to the controlled element;
wherein the path generator is adapted and configured to:
prior to the controlled element performing a move, generate a path profile in accordance with desired end conditions between an initial position and a final position, the path profile having a known sampling period;
compute a length of time remaining to complete the move along the path profile;
compare the length of time remaining to a length of the known sample period; and
substitute the length of time remaining for the length of the known sample period when the length of time remaining is shorter than the length of the known sample period.
5. The system of claim 4 , wherein the path generator is a firmware subsystem of a microprocessor.
6. The system of claim 5 , wherein the path generator is dedicated to path planning.
7. The system of claim 4 , wherein the path generator is further configured to
check values of actual end conditions at the final position of the move against the desired end conditions of the move.
8. The system of claim 4 , wherein jerk is a constant value throughout the duration of the move.