Smart Sealing for MR-Fluid Actuators - TU Berlin · 2. Design of a smart sealing for MR-Fluid actuators Permanentmagnet MRFElectromagnet µ r >> 1 µ = 1 Design of a smart sealing

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.



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

3

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


MRF exposed to a

magnetic field


4

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.



5

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


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


6

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


MRF Electromagnet µr >> 1 µr = 1 Permanentmagnet


7

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.



Different MR-fluid movement control concepts

8


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


9

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


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


viscous idle torque is eliminated

parasitic torque remains

Sealings and Bearings

1

1

10


Conventional sealing: radial shaft sealing


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

11


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


12


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



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


,A

M r B dA

13


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


14


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


15


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


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

16

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


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


17

Sectional-view of the MR-fluid actuator


Area of

the smart

sealing

Investigation of the tightness


• 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

18

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.


19

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.


Thanks for your attention!

Prof. Dr. Jürgen Maas


Department of Electrical Engineering and Computer Science


[email protected]

Phone: +49 (0)5261 702-5871

Christian Hegger M.Sc.


Department of Electrical Engineering and Computer Science


[email protected]

Phone: +49 (0)5261 702-5054

Documents

Smart Sealing for MR-Fluid Actuators - TU Berlin · 2. Design of a smart sealing for MR-Fluid actuators Permanentmagnet MRFElectromagnet µ r >> 1 µ = 1 Design of a smart sealing