Galil DMC-2X00 Stepper Position Maintenance Mode SPM, Operand Summary Stepper Motor Operation

MT

RP

TD

TP

Motor Type (2,-2,2.5 or -2.5 for stepper motors) Report Commanded Position

Report number of step pulses generated by controller Tell Position of Encoder

Operand Summary - Stepper Motor Operation

operand

_DEa

_DPa

_ITa

_KSa

_MTa

_RPa

_TDa

_TPa

Description

Contains the value of the step count register for the ‘a’ axis Contains the value of the main encoder for the ‘a’ axis

Contains the value of the Independent Time constant for the 'a' axis Contains the value of the Stepper Motor Smoothing Constant for the 'a' axis Contains the motor type value for the 'a' axis

Contains the commanded position generated by the profiler for the ‘a’ axis Contains the value of the step count register for the ‘a’ axis

Contains the value of the main encoder for the ‘a’ axis

Stepper Position Maintenance Mode (SPM)

The Galil controller can be set into the Stepper Position Maintenance (SPM) mode to handle the event of stepper motor position error. The mode looks at position feedback from the main encoder and compares it to the commanded step pulses. The position information is used to determine if there is any significant difference between the commanded and the actual motor positions. If such error is detected, it is updated into a command value for operator use. In addition, the SPM mode can be used as a method to correct for friction at the end of a microstepping move. This capability provides closed- loop control at the application program level. SPM mode can be used with Galil and non-Galil step drives.

SPM mode is configured, executed, and managed with seven commands. This mode also utilizes the #POSERR automatic subroutine allowing for automatic user-defined handling of an error event.

Internal Controller Commands (user can query):

QS Error Magnitude (pulses)

User Configurable Commands (user can query & change):

OE	Profiler Off-On Error
YA	Step Drive Resolution (pulses / full motor step)
YB	Step Motor Resolution (full motor steps / revolution)
YC	Encoder Resolution (counts / revolution)
YR	Error Correction (pulses)
YS	Stepper Position Maintenance enable, status

A pulse is defined by the resolution of the step drive being used. Therefore, one pulse could be a full step, a half step or a microstep.

DMC-2X00 Chapter 6 Programming Motion y 63