EMA Technology Overview
ElectroMagnetic Actuator – EMA4K
• Peak Force = 19kN
• Peak Vel = 4m/sec
• Typical Damper Pk
Performance: 10kN @ 4m/sec
• Freq response up to 300Hz
• 200mm stroke
• All Electric Motion
• Also avail in 1K, 2K, 6K
configurations
Electromagnetic Actuator Fundamentals
•U-Channel Brushless Linear Servo Motor
•Consists of a non-contacting forcer coil and a
U-channel rare earth (Neodymium) magnet track
•Ironless forcer means there are no attractive forces and no
disturbance forces generated between forcer and magnet track
•Ironless forcer has low mass resulting in high acceleration forces
•Three phase coil winding with sinusoidal brushless commutation
•U-Channel design reduces magnetic flux leakage
•Non-contact design supported by standard bearings to handle off-axis loading
Electromagnetic Technology – Where Used
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Assembly
Automotive
Data Storage
Electronic
Manufacturing
• Machine Tool
• Medical
• Military/Aerospace
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Fiber Optics
Photovoltaics
Packaging
Engineered Systems
Test & Inspection
Electromagnetic Actuator (EMA)
Major Components
Actuator motion
generated here
Drylin actuator shaft
bearing with
replaceable inserts
U-Channel Magnet
Assembly bolted to
column supports
both sides
Forcer block
attached to 3-phase
forcer coils on each
side (inside Uchannel magnets)
End of Travel Limit
Switches
U-Channel Rare
Earth Magnets
Lower T-rail bearing
support – 1 each
side
Optical
Encoder Read
head with 1um
resolution
EMA Comparisons – Damper Testing
EMA vs MTS
30
25
Force KN
20
15
10
5
0
0.00
0.15
EMA 4K
0.51
1.14
1.20
MTS 849.15
1.40
1.98
2.00
Velocity
MTS 849.25
2.18
2.30
M/SEC
EMA 2K
2.50
2.57
EMA 6K
2.90
2.95
3.30
Linear (MTS 849.15)
Typical shock absorber performance as obtained from published literature
4.00
EMA Comparisons – General Performance
Actuator Performance Comparison
Displacement mm (Pk-Pk)
1000
100
10
1
0.1
1
10
Hyd HS
Frequency (Hz)
100
EMA4K
Estimates based on the following assumptions:
• 2500kg GVW, 40kg unsprung, 650kg sprung mass, 6N/mm/sec viscous loading, 50N/mm spring load.
• Hyd HS = Typical hydraulic actuator with hydrostatic bearings, dual 50l/min servovalves,
200l/min 210 bar hydraulic supply
1000
EMA Comparisons – General Performance
Displacement (Pk-Pk)
Freq(Hz)
*Peak Acceleration
Hyd HS
EMA4K
1
150
177
2
150
177
3
143.5
177
5
86.22
161
7
61.33
113
10
42.67
76
Hyd HS
EMA4K
20
19.76
26.3
25.56kg
19kg
30
11.16
12.5
50
4.6
4.68
70
--
2.41
150
--
0.53
200
--
0.26
Hyd HS
EMA4K
23.14
24.25
* = peak acceleration based on unsprung mass
of 40kg, wheelpan 20kg, and mass of
actuator
Actuator Mass
Estimates based on the following assumptions:
• 2500GVW, 40kg unsprung, 650kg sprung mass,
6N/mm/sec viscous loading, 50N/mm spring load.
• Hyd HS = Typical hydraulic actuator with hydrostatic
bearings, dual 60l/min servovalves, 200l/min 210 bar
hydraulic supply
EMA2K Performance – Road Data
Plot of Track Data Command and Feedback Profiles – Direct file Playback
(No transfer function compensation required)
EMA2K Performance – Road Data
Zoom In on portion of Command AND Feedback Track Data (there are 2 plots)
EMA2K Performance – Road Data
Plot of Error throughout Entire Track File (Command – Feedback)
RMS Error less than 0.001” (0.025mm)
EMA2K Performance – Road Data
Plot of Actual Forces Achieved during dynamic Track Data Playback on EMA2K
EMA2K Performance – Road Data
Zoom Plot of Dynamic Force - Track Data
EMA Benefits Summary
 Higher performance / frequency response due to:
 No oil column resonance
 Lower actuator mass
 Lower friction (no seals)
 Tighter closed loop control
Direct file playback often 10X better than hydraulic system with
transfer function compensation!
 Independent of operating temperature
No oil viscosity variables to affect control loop
 Independent of waveform content
Can accurately run low velocity/low force and high velocity/high
force without changeover from 2stage to 3stage, etc
 Independent of accumulator charging/discharging cycles
EMA Benefits Summary
 Less Maintenance and Downtime
 No seals, accumulators, servovalves, filtration, oil contamination
 DryLin bearings only contact points – easily replaceable
 No system degradation due to component wear (pumps, valves,
etc)
 Modular design and less components makes troubleshooting
easier
 Lower Operating Costs
 Increased efficiency over servohydraulics means annual
electrical operating costs are 30% of comparable hydraulic
systems
 No filters, accumulators, servovalves, seals, hoses, pumps to
repair/replace
 Service and Support fees a fraction of major hydraulic
competitors!
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