Rockwell Automation GMLC Reference Manual - Manual (Page 518)

Publication GMLC-5.2 - November 1999
481
There are 42 separate soft registration position variables, one for each of
the four physical axes, the two virtual axes, and the imaginary axis. For
example, the actual position of Axis 3 is stored in Soft_Reg_Pos_
Axis3_AXIS1, when a registration event occurs on Axis 1. The command
position of the imaginary axis is stored in Soft_Reg_Pos_ Imag_AXIS3
when a registration event occurs on Axis 3, etc.
Since the Soft_Reg_Posx.x variables are sampled at the servo update rate
rather than directly in hardware, soft registration is not as accurate as hard
registration. The position uncertainty of the Soft_Reg_Posx.x variable for
an axis is the product of the time between servo updates and the axis
speed. Use the formula below to calculate the uncertainty in the software
registration position:
In the following example, assume a servo update rate of 500 Hz. If Axis 1
is moving at a speed of 2 meters per second and a registration event
occurs on Axis 3, the uncertainty of the Soft_Reg_Pos_Axis1_AXIS3
variable is:
[ ]
Hz Rate Update Servo
Second
its Positon Un
Speed Axis
y Uncertaint Position on Registrati Soft




=
mm 4 m 004 . 0
500
Second
Meters
2
Uncrtainty Position on Registrati Soft
= = =