A.1.6 Tuning the position loop for a velocity servo drive
The MintDrive can be tuned as a velocity servo drive, passing the profiled demand components through the speed and current loops only. To do this the MintDrive keyword CONFIG should be set to 1 by typing:
CONFIG=1
The gain term KVELFF should be set to the value derived from the following equation:
KVELFF = (32767 / (((MaxMotorSpeed / 60) / Servo Frequency) x (4 x MotorEncoderLines))) / 16
where:
Servo Frequency is the reciprocal of the time period set using the Mint keyword LOOPTIME; MotorEncoderLines is 1024 for a resolver motor;
MaxMotorSpeed is found from the motor specifications.
A.1.7 Tuning the position loop for a servo drive
The MintDrive can be tuned as a servo drive, passing the profiled demand components through the position, speed and current loops. To do this the MintDrive keyword CONFIG should be set to 1 by typing:
CONFIG=1
There are two types of move that can be used to help tune the position loop; step and trapezoid.
A step move performs an instantaneous position demand change. This is useful for tuning the motor to overcome following error and decrease response time.
The trapezoid move type performs a trapezoidal move based on a given acceleration, slew speed and deceleration profile. This is equivalent to a positional move generated by using the keywords MOVEA or
MOVER.
A.1.7.1 Position Loop gain terms
The output from the position loop is effectively a speed command. This command is a
Before starting, it may be necessary to increase the Following Error Fatal limit, the threshold at which the drive will trip with a Following Error. The default value is 1000 counts which may not be sufficient whilst initially tuning the motor.
KVELFF - Velocity Feedforward gain
This is applied to the demand speed. The profiler will generate a demand speed based upon the current move. This term should be used to scale that demand speed to the equivalent speed command for the speed loop - this is related to the specified maximum speed of the motor and of the position (servo) loop frequency:
The gain term KVELFF should be set to the value derived from the following equation:
KVELFF = (32767 / (((MaxMotorSpeed / 60) / Servo Frequency) x (4 x MotorEncoderLines))) / 16
