Delta Tau GEO BRICK LV User Manual
Turbo PMAC User Manual
Setting Up the Servo Loop
183
MOTOR COMPENSATION TABLES AND CONSTANTS
Turbo PMAC has the capability to perform sophisticated table-based corrections for both position and
torque on its motors. These permit compensating for imperfections in the system that cannot be measured
with the sensors used in the actual application (although reference sensors that can measure the
imperfections must be used to characterize the errors).
torque on its motors. These permit compensating for imperfections in the system that cannot be measured
with the sensors used in the actual application (although reference sensors that can measure the
imperfections must be used to characterize the errors).
Note:
Deadband compensation, controlled by motor parameters Ixx64 and Ixx65, is part
of the servo feedback algorithm. It is covered in the Setting Up the Servo Loop
section of this manual.
of the servo feedback algorithm. It is covered in the Setting Up the Servo Loop
section of this manual.
Note:
Cutter-radius compensation is a coordinate-system function, not a motor function.
It is covered in the Writing and Executing Motion Programs section of this manual.
It is covered in the Writing and Executing Motion Programs section of this manual.
Position Compensation Tables
Turbo PMAC is capable of performing table-based position correction, commonly called leadscrew
compensation. This technique, which also goes by other names, allows for a table of corrections to be
entered into Turbo PMAC as a function of motor position. Turbo PMAC can store up to 32 of these
compensation tables.
compensation. This technique, which also goes by other names, allows for a table of corrections to be
entered into Turbo PMAC as a function of motor position. Turbo PMAC can store up to 32 of these
compensation tables.
These tables are most often used to compensate for imperfections in the mechanics between the position
sensor (often on the back of the motor) and the load whose position is to be controlled. In many systems,
the leadscrew that moves the load linearly as the motor rotates is the largest source of positioning error, so
traditionally these tables are called leadscrew compensation tables. However, these tables can also be
used to compensate for imperfections in the sensor itself.
sensor (often on the back of the motor) and the load whose position is to be controlled. In many systems,
the leadscrew that moves the load linearly as the motor rotates is the largest source of positioning error, so
traditionally these tables are called leadscrew compensation tables. However, these tables can also be
used to compensate for imperfections in the sensor itself.
Source, Target, and Assigned Motors
Each motor can have one table that belongs to it; that is, the DEFINE COMP command that creates the
table assigns it to the presently addressed motor, and each motor can only have one table assigned to it.
Unless otherwise specified, the table uses position information from this motor (source data) to determine
the location in the table, and also adds its correction to this motor (target data). However, the source
motors or both the source and the target motors may be specified to be motors other than the motor to
which the table belongs. (If both motors are different, the concept of the table belonging to a motor is
useful only for Turbo PMAC’s own bookkeeping purposes.)
table assigns it to the presently addressed motor, and each motor can only have one table assigned to it.
Unless otherwise specified, the table uses position information from this motor (source data) to determine
the location in the table, and also adds its correction to this motor (target data). However, the source
motors or both the source and the target motors may be specified to be motors other than the motor to
which the table belongs. (If both motors are different, the concept of the table belonging to a motor is
useful only for Turbo PMAC’s own bookkeeping purposes.)
Standard Leadscrew Compensation
A position compensation table with a single source motor, and the target motor the same as the source
motor, forms a standard leadscrew compensation table. This is the most commonly used type of table, as
the errors in the direction of travel as function of that travel tend to be the largest errors.
motor, forms a standard leadscrew compensation table. This is the most commonly used type of table, as
the errors in the direction of travel as function of that travel tend to be the largest errors.