PMAC Product Guide Note: The EZ-PMAC Setup Software has a dedicated screen for the configuration of the Ix25 I-Variable. The same screen allows monitoring the end-of-travel limits and other related flags. Ix26 Motor x Home Offset : This variable determines an offset in 1/16 of a count that PMAC will move after the home procedure is completed. It is important to let PMAC move away from the home sensor which could be important for a better reliable home search routine. Servo Control I-Variables The servo control variables are setup in the motor tuning process. Usually, this is accomplished using a software tool like the PMAC Executive Software or the EZ-PMAC Setup Software. Note:
The EZ-PMAC Setup Software has a dedicate screen for the configuration of the tuning variables. However, the PMAC Executive program auto-tuning utility is strongly recommended for its simplicity and reliability. Ix30 Motor x Proportional Gain : This is the most important variable for the tuning setup process. It determines how strong the corrections on the servo loop will be made based on a given following error value. The rule of thumb for the setup of this variable is to increase it until the motor starts to buzz and the backup for about 20% of its value. Ix31 Motor x Derivative Gain : This variable acts effectively as an electronic damper.
The higher Ix31 is, the heavier the damping effect is. On a typical system with a current-loop amplifier and PMAC’s default servo update time (~440 msec), an Ix31 value of 2000 to 3000 will provide a critically damped step response. Ix32 Motor x Velocity Feed Forward Gain : Typically, this variable is used to minimize the tracking errors when the motor is moving with a constant velocity. If the motor is driving a current-loop (torque) amplifier, usually Ix32 will be equal to (or slightly greater than) Ix31 to minimize tracking error. Ix33 Motor x Integral Gain : Typically, this variable is used to minimize the steady state following error when the motor is settling on the target position.
Usually, the following error in this case is due to gravity and external forces. Ix35 Motor x Acceleration Feed Forward Gain : This parameter is intended to reduce tracking error due to inertial lag. Ix68 Motor x Friction Feedforward : This parameter is intended primarily to help overcome errors due to mechanical friction. Coordinate System I-Variables Ix87 C.S. x Default Acceleration Time : This parameter determines the default acceleration time of a motion program running on Coordinate System x which is otherwise set by the TA parameter inside the motion program. Ix88 C.S. x Default S-Curve Time :
This parameter determines the default S-curve acceleration time of a motion program running on Coordinate System x which is otherwise set by the TS parameter inside the motion program. Ix89 C.S. x Default Feedrate : This parameter determines the default federate (velocity) of a motion program running on Coordinate System x which is otherwise set by the F parameter inside the motion program. 54 Programming PMAC