PMAC Product Guide Ix17 - Motor x Maximum Acceleration : This parameter sets the maximum allowed acceleration for a motor performing a linear move issued from a motion program. This maximum value is not observed if variable I13 is greater than zero. Note: Safety parameters Ix16 and Ix17 are not observed if I13 is greater than zero. I13 greater than zero is necessary, for example, if a motion program is performing a circular interpolation move. Ix19 - Motor x Maximum Jog/Home Acceleration : This parameter sets the maximum allowed acceleration rate for a motor performing jog or homing move.
S-Curve and Linear Acceleration Variables The acceleration portion of a programmed move, either programmed by a jog or a motion program command, is controlled by two time parameters in units of millisecond. In the case of jog or homing commands these two parameters are I-Variables Ix20 and Ix21. Ix20 determines the overall acceleration time which is the total time required for any change in velocity. Ix21 determines the portion of the overall acceleration ramp that is performed in S-curve mode: In all cases, if two times the S-curve acceleration parameter is greater than the linear acceleration parameter then the overall acceleration time will be two times the S-curve acceleration time:
If (2 x Ix21) > Ix20 then Ix20 = (2 x Ix21) The acceleration of either linear or circular interpolated moves programmed from a motion program is determined by a set of different parameters. However, these parameters have the same meaning as those described above: Rate vs Time: Programming the Maximum Acceleration Parameters The safety I-Variables Ix17 and Ix19 determine the maximum allowed acceleration for the motor x. These variables are programmed in the resulting rate of encoder counts per millisecond square. However, the acceleration of a programmed move, either from jog commands or motion programs, is set in milliseconds as described above.
The following relationship holds for the conversion between those parameters: Velocity Rate on Accelerati = Time on Accelerati Curve S' ' - Time on Accelerati Linear 52 Programming PMAC Move type S-Curve Acceleration Parameter Linear Acceleration Parameter Jog or Home commands Ix21 Ix20 Linear or circular interpolation TA or Ix87 TS or Ix88