Danfoss MCO 305 Design Manual page 10

MCO 305 Design Guide
User Units
The units for the drive or the slave and the master, respectively, can be defined by the user in any way
desired so that the user can work with meaningful measurements.
User Units [UU]
All path information in motion commands are made in user units and are converted to quad-counts
internally. These also have an effect on all commands for the positioning: e.g. APOS, POS.
The user can also select meaningful units for the CAM control in order to describe the curve for the master
and the slave, for example 1/100 mm, or 1/10 degrees in applications where a revolution is being observed.
In the CAM control, the maximum run distance of the slave or the slave cycle length are indicated in User
Units UU (qc).
You can standardize the unit with a factor. This factor is a fraction which consists of a numerator and
denominator:
1 User Unit UU
par. 32-12 User Unit Numerator POSFACT_Z
par. 32-11 User Unit Denominator POSFACT_N
Scaling determines how many quad-counts make up a user unit. For example, if it is 50375/1000, then one
UU corresponds to exactly 50.375 qc.
NB!:
When user units are transferred into qc, then they get truncated. When qc are transferred into
user units, then they get rounded.
Master Units [MU]
A factor (fraction) is used for the conversion into qc, as with the user unit:
1 Master Unit MU
par. 33-10 Synchronization Factor Master SYNCFACTM
par. 33-11 Synchronization Factor Slave SYNCFACTS
Open Loop vs. Closed Loop
Open loop is control without feedback. Closed loop control compares velocity or position feedback with the
commanded velocity or position and generates a modified command to make the error smaller. The error is
the difference between the required speed and the actual speed.
Open loop can be used on systems where motor velocity is not critical, and where accurate positioning is
not necessary. Applications such as fan and blower control, pump control, and some low-end home
appliances are examples.
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__ How to Read this
par. 32 - 12 User Unit Numerator
par. 32 - 11 User Unit Denomintor
par. 33 10 Synchroniz
par. 33 11 Synchroniz
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Design Guide __
ation Factor Master
ation Factor Slave