Danfoss VLT Series Programming Manual page 26

Servo Drive Operation
2 2
Fieldbus
Target
reached
Command
Error
Positive software
limit active
PLC
Done
Busy
Error
Illustration 2.8 Servo Drive is Outside the Valid Position Limit
and the Target Position is in the Wrong Direction
Fieldbus
Target
reached
Command
Error
Positive software
limit active
PLC
Done
Busy
Error
Illustration 2.9 Servo Drive is Outside the Valid Position Limit.
The Target Position is Still Not in a Valid Area, but is Nearer to
it than the Previous Position
24
®
VLT
position limit
Positioning
command
Positioning
command
Danfoss A/S © 01/2017 All rights reserved.
®
Integrated Servo Drive ISD 510 System
2.3.5 Brake Handling
When the servo drive enters state Operation enabled, it
automatically lifts the brake. The servo drive reports the
Target
new state after the brake is lifted.
position
Software
When the servo drive leaves state Operation enabled, it
automatically releases the brake so that the axis cannot
Time
sag down. The servo drive reports the new state after the
brake is unreleased.
The brake state can be overwritten using the digital output
object (see chapter 7.21.4 Parameter 16-66: Digital Outputs
(0x60FE)). This is only allowed in unpowered state. The
valid commands and the reactions are shown in
Illustration 2.10.
WARNING
UNINTENDED MOTION
Releasing the brake in an unpowered state may result in
unintended motion leading to death, serious injury,
damage to equipment, or other material damage.
•
Do not release the brake in an unpowered state.
Motor in
unpowered
User command:
state
Brake is open
Illustration 2.10 Valid Brake Commands and Reactions
Target
position
Software
position limit
It is not possible to have an energized motor with a closed
brake. For further information about the current state, see
Time
chapter 7.22.8 Parameter 50-09: STO Voltage and Brake Status
(0x2007).
2.3.6 Control Loops
Servo motor control takes place using 3 cascaded control
loops (position controller, speed controller, and current
controller) with trajectory generators for position and
velocity. The control loops run synchronously with the
fieldbus cycles. The cycle times shown in Table 2.3 are
possible with Ethernet POWERLINK
Fieldbus cycle
[µs]
400
500
800
User command: Energize
Motor in
Close brake motor
unpowered
Unpower
state
Open brake motor
Brake is closed
Energize motor
®
and EtherCAT
Position control Speed control
cycle cycle
[µs] [µs]
200 200
250 250
200 200
Motor is
energized
Brake is open
®
:
Current control
cycle
[µs]
100
125
100
MG36D102