Danfoss VLT Series Programming Manual page 43

Servo Drive Operation
1 2
New CAM
(Bit 4)
Change CAM
immediately
(Bit 5)
A B
selector
B
A A B
status
CAM ack
(Bit 12)
Illustration 2.37 CAM Profile Handling for 2 CAM Profiles
New CAM profile numbers are buffered in the buffered
CAM profile selector as long as there is a free CAM profile
selector buffer available in the axis. If no CAM is in
progress, the new CAM profile becomes active immediately
(case 1 in Illustration 2.37).
If a CAM profile is in progress, the new CAM profile
number is stored in the CAM profile buffer (cases 2 and 3
in Illustration 2.37). If all profile number buffers are busy
(CAM ack bit is 1), the reaction depends on the Change
CAM immediately bit. If the Change CAM immediately bit is
set to 0, the new CAM profile is rejected (case 4) with a
command error indication (Statusword). If the Change CAM
immediately bit is set to 1, the new CAM profile number is
processed immediately. The currently running CAM profile
is discarded (case 5 in Illustration 2.37).
The Buffered CAM profile selector is not available as an
object for readout. There are cases where it is necessary to
do a compensation movement when switching between
CAMs. This movement is called blending and it is
calculated automatically by the servo drive. The blending
takes place using a polynomial of 5
2.4.5.2 CAM Configuration: Master
Absolute/Relative
If the master and slave positions are configured to be
absolute positions, it is necessary to have a synchroni-
zation movement that aligns the position at the point of
activation with the set-position of the profile. This is called
blending. For blending, a polynomial of 5
It is automatically calculated by the servo drive.
The blending can be influenced using bit Use blend
distance. When set to 0, the blending is done to the 1
data point of a basic CAM, or the start node of an
advanced CAM. This distance can be very short, which
leads to high velocity or acceleration.
When a concrete blend distance is used, set the Use blend
distance bit. Then, the value given in the minimum
blending object 0x380A (see chapter 7.14.11 Parameter:
Minimum Blending Distance (0x380A)) is used to calculate a
MG36D102
Programming Guide
3 4 5
C D E
C C
B B E
th
degree.
th
degree is used.
st
Danfoss A/S © 01/2017 All rights reserved.
synchronization movement within the axis. This distance
should be regarded as a minimum value, as there are
situations where the servo drive automatically enlarges this
distance (for example, if the end of the distance does not
lead to a point of a defined CAM, see Illustration 2.50).
When using non-cyclic CAM profiles, the influence of
Master relative versus Master absolute is only an offset in
guide value direction. This is dependent on the point of
activation of the CAM profile.
2.4.5.3 CAM Header Information
All parameters defined in this header information have
corresponding parameters in the object dictionary. These
objects are updated at the point of activation of the CAM.
If an element is not included in the header (which is
allowed for optional elements), the parameter in the object
dictionary remains unchanged. When leaving a CAM, the
values in the object dictionary persist; so they are not
switched back to their old values before the CAM
activation. The header information is the same for both
CAM types.
Illustration 2.38 CAM Header Information
Each file can only contain 1 CamProfile element.
Mandatory/ Value
Attri optional range/
bute (+default allowed
value) values
Versi O x.x.x.x
on
Table 2.6 Attribute for Element CamProfile
The CamProfile element contains an optional element
masterScaling which defines the length of a guide value
cycle. This parameter is used as scaling factor. If this
element is missing, the values from the object dictionary
are used (see chapter 7.8.4 Parameter: Guide Value Scaling
Factor (0x3808)).
Description
Gives the version of the
CAM profile definition.
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2 2