8 Units
Position, Velocity and Acceleration are scaled differently for EtherNet/IP than for Workbench. In Workbench,
these values are displayed as floating point numbers and can been configured in many ways. In EtherNet/IP,
these values are integers and are scaled as a ratio of position units to actual position counts.
8.1 Position Units
Position values are scaled according to the EtherNet/IP Position Controller Device standard. One “Position
Units” scaling value is defined, which gives the number of actual position feedback counts (at 32 bits per
revolution) equal to one position unit.
From Workbench, this scaling parameter is visible in the EtherNet/IP screen or as EIP.POSUNIT in the ter-
minal.
From EtherNet/IP, this value can be accessed at attribute 0x04 Position Units of the Position Controller
object.
The default value is 2^16 = 65536, which provides 2^32 / 2^16 = 2^16 counts per revolution. A value of 1
would provide 2^32 / 1 = 2^32 counts per revolution.
l
l When dynamically mapping response or command assembly, position units are scaled from 8 bytes to
4 bytes. This results in a loss of precision for the parameters PL.CMD, PL.ERR, SWLS.LIMIT0, and
SWLS.LIMIT1.
8.2 Velocity and Acceleration Units
Velocity and Acceleration values are scaled according to the EtherNet/IP Position Controller Device stand-
ard. One “Profile Units” scaling value is defined, which affects both velocity and acceleration.
For velocity values, Profile Units gives the number of actual position feedback counts (at 32 bits per revolu-
tion) per second equal to one velocity unit.
For acceleration values, Profile Units gives the number of actual position feedback counts (at 32 bits per
revolution) per second^2 equal to one acceleration unit.
From Workbench, this scaling parameter is visible in the EtherNet/IP screen or as EIP.PROFUNIT in the ter-
minal.
From EtherNet/IP, this value can be accessed at attribute 0x05 Profile Units of the Position Controller object.
The default value is 2^16 = 65536, which provides 2^32 / 2^16 = 2^16 counts per second per revolution. A
value of 1 would provide 2^32 / 1 = 2^32 counts per second per revolution.
8.3 Torque Units
Torque commands and values are scaled in milliamps [mA].
8.4 Other Floating Point Values
Other parameters which are displayed as floating point values in Workbench are provided with three-digit
accuracy over EtherNet/IP. For example, a velocity loop gain VL.KP of 1.200 would be read over EtherNet/IP
as 1200.
Ethernet/IP Communications | 8 Units
Kollmorgen | December 2014 27
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