Download Utilization of digitally controlled servo drives in simplification of

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