Smart Sealing for MR-Fluid Actuators
Christian Hegger and Jürgen Maas
ERMR 2016, Incheon, Korea
Juli 7th 2016
Prof. Dr. Jürgen Maas
Ostwestfalen-Lippe University of Applied Sciences
Control Engineering and Mechatronic Systems
Christian Hegger M.Sc.
Ostwestfalen-Lippe University of Applied Sciences
Control Engineering and Mechatronic Systems
2
Outline
1. Introduction and motivation
2. Design of a smart sealing for MR-Fluid actuators
3. Test setup and experimental investigation
4. Conclusion and Outlook
(C) Control Engineering and Mechatronic Systems (Prof. Dr.-Ing. Jürgen Maas) – Christian Hegger Smart Sealing for MR-Fluid Actuators
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Carbonyl iron powder particles are suspended in a carrier oil by using additives for
reducing e.g. the sedimentation processes.
By applying a magnetic field, these particles form chains in the direction of the
magnetic flux, which change the yield stress up to 80 kPa of the MRF within
milliseconds depending on the magnetic flux density.
Operating mode for
brakes and clutches
rotational actuators
shear mode
B
F
MRF
B=0
B≠0
1. Introduction and motivation
MRF exposed to a
magnetic field
(C) Control Engineering and Mechatronic Systems (Prof. Dr.-Ing. Jürgen Maas) – Christian Hegger Smart Sealing for MR-Fluid Actuators
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MRF-Device with axial shear gap for high rotational speeds
0 1 2 3 4 50
5
10
15
20
25
30
current I in A
torq
ue T
in
Nm
n=500 min-1
n=2000 min-1
n=3000 min-1
n=5000 min-1
n=6000 min-1
Measurements showing control characteristic lines for different
rotational speeds at 𝜗𝑀𝑅𝐹 = 50°𝐶
Discussion:
• MRF brakes and clutches
for applications with high
rotational speeds can be
realized
• Reproducible transmitting
torque even at high
rotational speeds
• High viscous torque at
high rotational differential
speed n (without
excitation, (I = 0A)
Resulting necessity:
Approach for reducing the viscous idle torque of MRF brakes and clutches by a
magnetically controlled movement of the MR fluid.
1. Introduction and motivation
(C) Control Engineering and Mechatronic Systems (Prof. Dr.-Ing. Jürgen Maas) – Christian Hegger Smart Sealing for MR-Fluid Actuators
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Multi-Mode gearboxes with several gears are
used to increase the efficiency and electrical
range of plug-in-HEV (PHEV)
Variety of coupling devices (hydraulic/wet-
running clutches)
High torque drag losses in the clutch
Losses in the hydraulic and pump
Integration of MRF-based coupling devices
with integrated MR-Fluid control to reduce
drag losses for increasing powertrain’s
efficiency PHEVplus
battery
ICE
gear box
E-Motor E-Motor
differential clutch
brake
1. Introduction and motivation
Multi-Mode gearbox
Nett, H.-P. et al.: Hybrid drive unit and method for
the operation thereof, Patent PCT WO 2010/063735
A2 (2010).
Integration
possibility for
MRF-based
coupling device
(C) Control Engineering and Mechatronic Systems (Prof. Dr.-Ing. Jürgen Maas) – Christian Hegger Smart Sealing for MR-Fluid Actuators
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Movement of the MRF is induced by a controlled leading of the magnetic flux resulting
in magnetic volume force acting on the MRF.
b)
transition state braking/coupling mode
Güth, D.; Schamoni, M.; Maas, J.: Magnetic fluid control for viscous loss reduction of high-speed MRF brakes and clutches with well-
defined fail-safe behavior. Smart Materials and Structures, Vol. 22, 094010, 2013.
idle mode
2
0
Tpt
H
vv v v g r J M
Navier-Stokes equations Kelvin force
Calculation of the movement by considering the fluid dynamics and magnetic induced
volume forces (Kelvin forces) applying the Navier Stokes equation:
Accel. force
1. Introduction and motivation
MRF Electromagnet µr >> 1 µr = 1 Permanentmagnet
(C) Control Engineering and Mechatronic Systems (Prof. Dr.-Ing. Jürgen Maas) – Christian Hegger Smart Sealing for MR-Fluid Actuators
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torque transmission region
inactive region polarity of the PM
electromagnet (EM)
χr = 0
χr >> 0
Conditional stable
The fluid movement is based on magnetic volume and
acceleration forces.
Bistable (fail-safe behavior)
The fluid movement is based on the magnetic volume forces.
The permanentmagnet can hold the current state, in case of a
system failure.
Monostable (fail-safe behavior)
The fluid movement is based on the magnetic volume forces.
Depending on the polarity of the permanentmagnets a fail-safe
behavior is defined.
1. Introduction and motivation
(C) Control Engineering and Mechatronic Systems (Prof. Dr.-Ing. Jürgen Maas) – Christian Hegger Smart Sealing for MR-Fluid Actuators
Different MR-fluid movement control concepts
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1. Introduction and motivation
Mechanical design for the experimental investigation of the MR-fluid movement control.
b)
MRF
Bearing
Sealing
Coil
Inner rotor
Outer rotor
1n
2nDrive shaft
Driven shaft
PM
100%
50%
0%
MR
-flu
id v
olu
me
Magnetic excitation
system without the
requirement of slip rings
Minimizing of
accelerated masses
Increasing of the
maximum coupling
torque by in series
connected magnetic
excitations
MRF Electromagnet µr >> 1 µr = 1
z
r
Previous investigation of the conditional stable MR-fluid movement control
(C) Control Engineering and Mechatronic Systems (Prof. Dr.-Ing. Jürgen Maas) – Christian Hegger Smart Sealing for MR-Fluid Actuators
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0
5
10
torq
ue T
in
Nm
transmitted torque
parasitic torque
0
1000
2000
rota
tio
nal
sp
eed
n i
n m
in-1
drive shaft
driven shaft
0 0.5 1 1.5 2 2.5 3 3.5 4 4.50
2
4
6
cu
rren
t I
in A
time t in s
1. Introduction and motivation
MRF-clutch Motor Torque sensor Torque sensor
Generator
3 3.2 3.4 3.60
0.5
1
1.5
2
torq
ue T
in
Nm
Experimental investigation of the proposed MRF-based clutch on a test bench
(C) Control Engineering and Mechatronic Systems (Prof. Dr.-Ing. Jürgen Maas) – Christian Hegger Smart Sealing for MR-Fluid Actuators
viscous idle torque is eliminated
parasitic torque remains
Sealings and Bearings
1
1
10
1. Introduction and motivation
Conventional sealing: radial shaft sealing
(C) Control Engineering and Mechatronic Systems (Prof. Dr.-Ing. Jürgen Maas) – Christian Hegger Smart Sealing for MR-Fluid Actuators
Cross section of a radial shaft sealing
0 50 100 150 2000
5
10
15
20
25
30
35
40
slid
ing
sp
ee
d v
in
m/s
shaft diameter d in mm
flour-elastomer FPM/FKM
polyacryl-elastomer ACR
nitiril-rubber NBR
radial shaft sealing: range of application
20 40 60 80 100 120 1400
100
200
300
400
500
600
dis
sip
ati
on
P in
W
shaft diameter d in mm
n=5000
n=4000
n=3000
n=2000
n=1000
n= 500
radial shaft sealing: dissipation
sealing lip dust lip
stiffening for
assembly
The most popular and validated sealing
is the radial shaft sealing.
But this classically sealing also has
some restrictions
Energy-efficiency
Limited range of application
VDI: DIN 3760, 1996-02
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2. Design of a smart sealing for MR-Fluid actuators
MRF Electromagnet µr >> 1 µr = 1 Permanentmagnet
Design of a smart sealing for MR-fluid actuators based on permanentmagnets.
In combination with the conditional stable MR-fluid movement control the MRF in
the sealing gap can be moved to the outer rotor by rotational accelerations.
In a radial sealing gap the MRF of the shear gap is sealed by the magnetically
increased shear stress due to the permanentmagnet.
0 0 0 z
r
Schematically Design
(C) Control Engineering and Mechatronic Systems (Prof. Dr.-Ing. Jürgen Maas) – Christian Hegger Smart Sealing for MR-Fluid Actuators
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2. Design of a smart sealing for MR-Fluid actuators
N
S0 200 400 600 800
0
0.3
1.5
To
rqu
e T
in
Nm
Time t in ms
Torque of sealing at n = 750 min-1
Torque of sealing at n = 1000 min-1
Torque of sealing at n = 2000 min-1
0.6
0.9
1.2
Simulation of the transient torque due to the
impact of the smart MR-fluid sealing
(1 sealing gap).
150
300
0
ma
gn
etic flu
x d
en
sity
B in
mT
100%
50%
0%
MR
-flu
id v
olu
me
Transient simulation of the smart sealing under the
influence of the rotational speed of n = 2000 min-1 :
Magnetic flux density
Distribution of the MR-fluid
µr >> 1 µr = 1 Permanentmagnet
z
r
z
r
Transient simulation of the smart sealing based on MRF
(C) Control Engineering and Mechatronic Systems (Prof. Dr.-Ing. Jürgen Maas) – Christian Hegger Smart Sealing for MR-Fluid Actuators
,A
M r B dA
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2. Design of a smart sealing for MR-Fluid actuators
Sealing based on
Permanetmagnet The proposed test actuator is
design as a MRF-brake.
For a fast realization and a
variable investigation the
permanentmagnets are
replaced by electromagnets.
The design of the sealing gap is
maintained. The coils for the
sealing are placed in the stator.
A main coil for the
transmission of torque in the
shear gap is neglected.
Sealing based on
Electromagnet
hs =
0,5
mm
L = 1,5 mm
r = 130 mm
z
r
Design of the actuator for the experimental investigation
(C) Control Engineering and Mechatronic Systems (Prof. Dr.-Ing. Jürgen Maas) – Christian Hegger Smart Sealing for MR-Fluid Actuators
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3. Test setup and experimental investigation
Torque sensor MR-fluid test
actuator (brake)
Motor
The MR-fluid actuator for the investigation of the smart MR-fluid sealing was realized and
implemented on a test bench.
The data logging includes:
• Rotational Speed
• Torque of the MR-brake
• Current of the MR-brake
• Temperature of the sealing gap
Test bench and data logging
(C) Control Engineering and Mechatronic Systems (Prof. Dr.-Ing. Jürgen Maas) – Christian Hegger Smart Sealing for MR-Fluid Actuators
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3. Test setup and experimental investigation
The torque of the MRF brake was
measured at increasing rotational
speeds n for different currents I resp.
magnetic flux densities B in the sealing
gap.
Measured torque of the MR brake
With increasing rotational speeds n the
measured torque drops down to the
values of the measured parasitic torque
of the actuator caused by the bearings.
Thus, the viscous losses of the MRF
and the losses of the sealing can be
completely eliminated.
Investigation of the drag torque
(C) Control Engineering and Mechatronic Systems (Prof. Dr.-Ing. Jürgen Maas) – Christian Hegger Smart Sealing for MR-Fluid Actuators
0 500 1000 1500 2000 2500 3000 3500 40000
0.5
1
1.5
2
2.5
3
3.5
4
rotational speed n in min-1
torq
ue
T in
Nm
current I=1500 mA (B
MRF = 159 mT)
current I=1000 mA (BMRF
= 104 mT)
current I = 750 mA (BMRF
= 77 mT)
parasitic (bearings) torque
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0 500 1000 1500 2000 2500 30000
0.2
0.4
0.6
0.8
1
1.2
1.4
dy
na
mic
pre
ss
ure
p
in
ba
r
current I in mA
calculated pressure
mesured pressure
3. Test setup and experimental investigation
B
s
c Lp p
h
[1] Coulter, Weiss, Carlson: Engineering Applications of Electrorheological Materials. Journal of Intelligent Material Systems and Structures, Vol. 4 – April 1993
The dynamic pressure in the shear gap
was increased and measured for certain
currents I.
Measured dynamic pressure of the sealing
The calculation of the dynamic pressure
was executed by [1]:
The value of the necessary dynamic
pressure for the sealing is supposed to
0.06 bar.
The pressure was measured by a
pressure gauge.
Investigation of the dynamic pressure
(C) Control Engineering and Mechatronic Systems (Prof. Dr.-Ing. Jürgen Maas) – Christian Hegger Smart Sealing for MR-Fluid Actuators
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Sectional-view of the MR-fluid actuator
3. Test setup and experimental investigation
Area of
the smart
sealing
Investigation of the tightness
(C) Control Engineering and Mechatronic Systems (Prof. Dr.-Ing. Jürgen Maas) – Christian Hegger Smart Sealing for MR-Fluid Actuators
• Short time leakage tests initially confirming
the tightness of the promising approach.
• Long time leakage tests are currently part of
investigation.
Assumed distribution of the
MR-fluid in down times
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4. Conclusion and Outlook
A magnetically induced MR-fluid control ensures a reduction of viscous losses.
A smart sealing based on permanentmagnets was introduced to eliminate friction
losses of a conventional sealing.
The experimental investigation showed an further improved energy-efficiency and a
sufficient high dynamic pressure for the intended sealing purpose.
In upcoming investigations the tightness of the smart sealing will be tested for
longer down times.
(C) Control Engineering and Mechatronic Systems (Prof. Dr.-Ing. Jürgen Maas) – Christian Hegger Smart Sealing for MR-Fluid Actuators
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Acknowledgement
This contribution is accomplished within the project “PHEVplus -
Effizienzgesteigerte Plug-in-Hybridsysteme durch innovative MRF-
Kupplungstechnologie“ (Efficiency increase of PHEV by MRF-based clutch
technology), funded by the Federal Ministry of Economy and Energy (BMWi) of
Germany under grant number FKZ: 01MY13004B, see www.phevplus.de.
(C) Control Engineering and Mechatronic Systems (Prof. Dr.-Ing. Jürgen Maas) – Christian Hegger Smart Sealing for MR-Fluid Actuators
Thanks for your attention!
Prof. Dr. Jürgen Maas
Ostwestfalen-Lippe University of Applied Sciences
Department of Electrical Engineering and Computer Science
Control Engineering and Mechatronic Systems
Phone: +49 (0)5261 702-5871
Christian Hegger M.Sc.
Ostwestfalen-Lippe University of Applied Sciences
Department of Electrical Engineering and Computer Science
Control Engineering and Mechatronic Systems
Phone: +49 (0)5261 702-5054