Utilization of digitally controlled servo drives in
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Transcript Utilization of digitally controlled servo drives in
Michal Kašpárek
Technical University in Liberec
Faculty of Mechanical Engineering
Department of Applied Cybernetics
[email protected]
Complex
mechanical structures
distributing driving power
• Frictional resistance
• Moment of inertia
• Energy loss
High
engine performance required
High energy consumption
New structure of machines
• Utilized in design of new structure of the drive of
small-diameter knitting machine
• Possible application in other textile machines
and different industry segments
• Utilization of several smaller electromotors
placed directly in front of control members
Significantly lower wattage and power demands
required
Much more simple mechanical construction
More robust power distibution
Transmissions
and gears replacement:
• High precision electronic cam
• Mutliple drive movement synchronization
Additional
capabilities
• Independent high precision motion control
• Complex driving function tracking
• Virtual cam usability
Drive
system of functional model of new
structure of small-diameter knitting
machine
Emerson
Control Techniques assembly
• Digitax ST servo drives
• CTM4 series servomotor
Digitax ST - Plus
• high performance drive
• optimized for pulse duty servo
•
•
•
•
applications
high peak torque (up to 56.4Nm
peak)
LED keypad and SM-Application
module
Drive control loop runs at 250 µs
Multiple drives networking
capabilities
Control
Techniques CTM4 series
servomotor
• high resolution SinCos multi-turn encoder
• 330 V driving voltage
• 2 A nominal current
• 2,5 Nm Torque
Servos
25% torque of original motor
• Load wheel also reduced to 25%
Active
current measurement:
• Peak under 10% of maximum current limit
• Huge reserve for 4x bigger real load
Presented
measurements utilize virtual
cam principle
• Complex trajectory of rotary motion
Modelled with high order polynomials in order to
ensure smooth progress of higher derivatives (speed,
acceleration)
• One revolution progression sampled into virtual
cam model of desired position and speed
Virtual cam revolution ≈ 2π ≈ 3600 samples
Limited module memory - 0.1º resolution
Real
position of the spindle is
transformed into the angle of virtual cam
revolution
According to this angle the speed and
position demand is returned
The encoder feedback is therefore
recalculated and used for control data
generation
Modern
servo drives were tested
Huge potential of energy conservation
was observed
Possibility of direct motor to action
member attachment was proven
Electronic cam usability was tested and
drives deviation was depicted
Virtual cam containing high order
polynomial motion model was
implemented
Typical
servomotors behaviour was
observed at low speeds tested for the
knitting machine operation modes
• Constant speed fluctuation with stable frequency
• Low speeds used compared to motor maximum of
4000 rpm (peaking over 5% of maximum)
Different
motors would need to be tested or
integrated transmission usage reconsidered
The influence of high-order polynomic
motion function was diminished by
described behaviour, nevertheless further
investigation of presented phenomenon is
necessary