a closed-loop stepper motor drive for use with long cables
TRANSCRIPT
A Closed-Loop Stepper Motor Drive for Use with Long CablesMark BUTCHER
Motivation – A CERN Application
CollimatorElectronics racks
Drive Cable Motors
Up to 800 m
Radiation free area Tunnel – High radiation area
2
Motivation – Current control problem
CollimatorElectronics racks
Drive Cable Motors
Up to 800 m
-10 -5 0 5x 10-5
-20
0
20
40
60
80
100
120
140
Vol
tage
(V)
Time (s)
Fixed duty cycle, 120 Volts, 20 kHz PWM applied on the drive-side,720 meter cable
3
Motivation – Current control problem
CollimatorElectronics racks
Drive Cable Motors
Up to 800 m
-10 -5 0 5x 10-5
-20
0
20
40
60
80
100
120
140
Vol
tage
(V)
Time (s)-10 -5 0 5
x 10-5
-2
-1
0
1
2
3
4
Cur
rent
(A)
Time (s)
Fixed duty cycle, 120 Volts, 20 kHz PWM applied on the drive-side,720 meter cable
4
Motivation – Current control problem
CollimatorElectronics racks
Drive Cable Motors
Up to 800 m
Fixed duty cycle, 120 Volts, 20 kHz PWM applied on the drive-side,720 meter cable
-10 -5 0 5x 10-5
-2
-1
0
1
2
3
4
Cur
rent
(A)
Time (s)-10 -5 0 5
x 10-5
-2
-1
0
1
2
3
4
Cur
rent
(A)
Time (s)
5
Motivation – Current control problem
CollimatorElectronics racks
Drive Cable Motors
Up to 800 m
Standard commercial drive performance
6
-0.02 -0.01 0 0.01 0.02 0.03 0.04-3
-2
-1
0
1
2
3
Cur
rent
(A)
Time (s)
Current Phase ACurrent Phase BCurrent reference Phase ACurrent reference Phase B
Motivation – Open-loop positioning problemOpen-loop position control
0.4 0.45 0.5 0.55
210
212
214
216
218
220θ m
ot [d
eg]
Time [s]
MeasuredReference
0.4 0.45 0.5 0.55-40
-20
0
20
40
ωm
ot [r
ad/s
]
Time [s]
7
Motivation – Closed-loop reliability problemClosed-loop position control with position sensor
0.4 0.45 0.5 0.55
30
32
34
36
38θ m
ot [d
eg]
Time [s]
MeasuredReference
0.4 0.45 0.5 0.55-40
-20
0
20
40
ωm
ot [r
ad/s
]
Time [s]
8
Our solutionA drive that has the:
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Our solutionA drive that has the:
1. Ability to work in all modes with up to 1km of cable
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Current control performance
• PWM @ 50 kHz
• 720 meter cable
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Our solutionA drive that has the:
1. Ability to work in all modes with up to 1km of cable
2. Ability to switch online from closed- to open-loop position control without step loss
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Online closed to open position loop switch
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Developed drive characteristics• Key specification:
• 2-phase Stepper Motor control. • Maximum current per phase 7 Amps RMS.• DC Voltage up to 170 Volts.• Stepping mode from full step to micro stepping.• Works with cables up to 1 km long.• Two operating modes:
• Standard stepping mode (open-loop position control).• Field Oriented Control (closed-loop position control).
• Communications:• Stepper interface (Step, Direction, Enable).• Serial communication RS-485 with Modbus.• Profibus.
• PWM and controller frequency configurable up to 60 kHz.• Controller parameters fully configurable.• Up to 2 kHz current control bandwidth.• Automatic cable length estimation.• Quadrature encoder interface.
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State of the Art
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• To our knowledge no commercial drives exist that can work with such long cables
• Drives exist that can work in open- and closed-loop mode but none that foresee sensor failure
• 2 patents propose switching between closed and open loop to avoid motor hunting in steady state but do not discuss sensor failure
• http://www.google.com/patents/US4591774• http://www.google.com/patents/US20070040529
Possible alternative application areas
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• Anywhere precise, reliable positioning is needed • Anywhere step motors must operate far from their
drives:
• in hostile environments:• Underwater (Underwater vehicles, pumps,…)• Nuclear power plants• High temperatures
• in clean environments:• Food processing plants
• where payload counts:• Aerial vehicles
Acknowledgements
- Alessandro Masi- Ricardo Picatoste- Paul Peronnard- Pablo Serrano Galvez- Michele Martino
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Thank you!
Additional Slides
Comparison – open-loop position control
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Comparison – closed-loop position control
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Online closed to open position loop switch
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