Reference Manual

Turbo PMAC/PMAC2 Software Reference
Turbo PMAC Global I-Variables 148
Some amplifiers will transmit status and fault information on the end of the serial data stream for the
ADC, and it is important to mask out these values from the current loop equations.
Examples:
For a 10-bit ADC: Ixx84=$FFC000
For a 12-bit ADC: Ixx84=$FFF000
For a 16-bit ADC: Ixx84=$FFFF00
Further Motor I-Variables
Ixx85 Motor xx Backlash Take-up Rate
Range: 0 - 8,388,607
Units: 1/16 count / background cycle
Default: 0
Ixx85 determines how fast backlash is taken up on direction reversal. The size of the backlash is
determined by Ixx86, and possibly by the backlash compensation table for the motor. Turbo PMAC will
take up the backlash at the Ixx85 rate whenever the commanded or Master Handwheel position for the
motor reverses by more than the amount set by Ixx87 the backlash hysteresis parameter. If Ixx85 is zero,
backlash is effectively disabled. Usually, Ixx85 is set interactively and experimentally to as high a value
as possible without creating dynamic problems.
Ixx86 Motor xx Backlash Size
Range: 0 - 8,388,607
Units: 1/16 count
Default: 0
Ixx86 allows PMAC to compensate for backlash in the motor's coupling by adding or subtracting
(depending on the new direction) the amount specified in the parameter to the commanded position on
direction reversals (this offset will not appear when position is queried or displayed). A value of zero
means no backlash. The rate at which this backlash is added or subtracted (taken up) is determined by
Ixx85.
Variable Ixx87, Backlash Hysteresis, determines the amount of reversal in desired position that is
required before backlash will start to be introduced or removed.
If backlash tables are used, Ixx86 represents the backlash at motor zero position; values in the table
should represent the difference between the backlash at a given position and Ixx86.
Note:
The units of this parameter are 1/16 of a count so the value should be 16 times the
number of counts of backlash compensation desired.
Example:
If there is a backlash on reversal of motor direction of 7.5 encoder counts, set Ixx86 to 7.5 * 16 = 120.
Ixx87 Motor xx Backlash Hysteresis
Range: 0 - 8,388,607
Units: 1/16 count
Default: 64 (= 4 counts)
Ixx87 controls the size of the direction reversal in motor commanded position that must occur on Motor
xx before Turbo PMAC starts to add the programmed backlash (Ixx86) in the direction of motion. The
purpose of this variable is to allow the customer to ensure that a very small direction reversal (e.g. from
the dithering of a master encoder) does not cause the backlash to kick in. Ixx87 thus provides a hysteresis
in the backlash function.