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Magnetic Fluid Control for Optimizing the Energy Efficiency for MRF-Actuators

(Magnetische Fluidsteuerung zur Optimierung der Energieeffizienz von MRF-Aktoren)

Dirk Güth, Jürgen Maas

Workshop der Nachwuchswissenschaftler im Rahmen der Fachausschusssitzung „Unkonventionelle Aktorik”

(23. Oktober 2014)

Prof. Dr.-Ing. Jürgen Maas

Ostwestfalen-Lippe University of Applied Sciences

Control Engineering and Mechatronic Systems

Liebigstraße 87, Lemgo, Germany

[email protected], www.motion-ctrl.de

(C) Control Engineering and Mechatronic Systems - Prof. Dr.-Ing. Jürgen Maas, Dirk Güth Magnetic Fluid Control for Optimizing the Energy Efficiency for MRF-Actuators

Outline

Introduction and motivation

Introductions and methodology of MR-fluid control

Concept for MRF-Clutch System with fluid control Conclusion

2

1. Introduction and motivation

Magnetorheological fluids are suspensions of micrometer-sized magnetic

particles (e.g. carbonyl iron powder) in a carrier fluid, usually a type of oil.

Carbonyl iron powder particles on a human hair:

3 (C) Control Engineering and Mechatronic Systems - Prof. Dr.-Ing. Jürgen Maas, Dirk Güth Magnetic Fluid Control for Optimizing the Energy Efficiency for MRF-Actuators

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 100 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



axial shear gap:

particle

concentration

due to

centrifugal forces

radial shear gap:

r r

Axial shear gaps offer:

• Advantages considering particle centrifugation at high rotational speeds due to an

inherent mixing effect (Taylor vortex flow) and an

• optimized torque generation due to the outside placed shear gap.

Shear gap design of MRF actuators based on the shear mode

Güth, D.; Wiehe, A.; Maas, J.: Modeling approach for the particle behavior in MR Fluids between moving surfaces. 12th International

Conference on Electrorheological (ER) Fluids and Magnetorheological (MR) Suspensions, World Scientific, 2010.



Brakes and clutches based on MRF offer an enormous potential for

high energy application with high rotational speeds:

Advanced dissipation of energy in MRF brakes and clutches:

• the scalable volume based energy dissipation in MRF brakes and clutches

• the advanced compensation of thermal load peaks due to a braking fluid volume

• the better dissipation of energy due to an advanced heat conductance

Challenge opposing a commercial use:

• high rotational speeds can be solved by an adequate design of shear gaps

• viscous torque at high rotational speeds in idle mode

disadvantageous from an energy point of view of an application e.g. HEV

needless reduction of lifetime of the MRF

6



MRF-Brake with axial shear gap for high rotational speeds up to 6.000 min-1

B

shear gap

electromagnet

shaft

seal

housing

magnetic circuit

bearing

rotor

Dimensions of shear gap:

mean radius r = 41mm, height h = 3mm, length l = 40mm, volume VMRF = 32ml.

7

Güth, D.; Wiebe, A.; Maas, J.: Design of Shear Gaps for High-Speed and High-Load MRF Brakes and Clutches. 13th International Conference

on Electrorheological (ER) Fluids and Magnetorheological (MR) Suspensions, Journal of Physics: Conference Series, 2013, 412, 012046.



MRF-Brake with an 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 for applications

with high rotational speeds

can be realized

• reproducible braking torque

even at high rotational

speeds

• high viscous torque at high

rotational speed n (without

excitation, (I = 0A)

• temperature depending

torque behavior needs to be

considered

Necessary conclusion:

• approach for reducing the viscous idle torque of MRF brakes and clutches

8

Güth, D.; Erbis, V.; Schamoni, M.; Maas, J.: Design and characteristics of MRF-based actuators for torque transmission under influence of high

shear rates up to 34,000 1/s. SPIE Smart Structures/NDE, Volume 9057, 90572P, 2014.

2. Simple concepts of MR-fluid control induced by force fields


• Shear gap volume are not completely filled with MRF for enabling a movement of the fluid.

• Use of different force effects like gravitational (orientation), centrifugal (rotation) and magnetic

forces for moving the MRF to achieve an engaged or disengaged mode.

• US patent application, US 7,306,083, Magnetorheological fluid device, GM Global Technology Operations, 2005)

• Patent application, “Magnetic Fluid Control”, 10 2011 119 919.9, Ostwestfalen-Lippe University of Applied Sciences, Germany, 2011.

use of gravitational force for

disengagement and magnetic

forces for engagement

Dis

en

ga

ge

d

mo

de

s

En

ga

ge

d

mo

de

s

use of centrifugal force for

disengagement and magnetic

forces for engagement

2. Basic design concept of MR-fluid control


• MRF movement between an active and inactive shear gap.

• Energy input and idle losses can be reduced or at best completely avoided.

• Advanced concept for complete disengagement during rotation and standstill.

• Integration of a permanent magnet for achieving states like a current less braking torque.

• Half section of the magnetically induced fluid control approach with a partially filled gap.

ω

permanent

magnet

active

shearing gap

inactive

shearing gap

electromagnet

shaft

flange

seal

magnetic circuit

housing

Güth, D.; Maas, J.: MRF actuators with reduced no-load losses. SPIE Smart Structures/NDE, Vol. 8341, S. 834121, 2012.

2. Basic design concept of MR-fluid control


• Motion of the MRF is induced by a controlled leading of the magnetic flux resulting in

magnetic force acting on the MRF.

• MRF can be switched between an active and inactive volume of the shear gap.

b)

transition between

braking/coupling and

idle mode

idle mode braking/coupling

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.


2. Design methodology for MR-fluid control

12

- current direction is moving into the page

- current direction is moving up out of the page

torque transmission region

inactive region i - inside EM

o - outside EM

polarity of the PM

electromagnet (EM)

χr = 0

χr >> 0

•disengaged •disengaged •disengaged •(Fig. 4)

•(Fig. 2/5)

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.

3. Concept for MRF-clutch system with fluid control


Development of a new clutch systems for energy-efficient use:

• Proof-of-Concept demonstrator as a clutch based on the fluid control for high rotational

speeds using magnetic forces of a permanent- and electro-magnet.

• Integration of the fluid control in a sophisticated clutch design avoiding disadvantageous

slip rings for power supply.

active shearing gap

inactive shearing gap

stator/housing

electromagnet

permanent magnet

driven shaft/inner rotor

drive shaft/outer rotor

• Two permanent magnets are used

for a fail safe torque transmission

No electrical control power for

torque transmission

• The electromagnet is used for the

idle mode

The idle losses can be

completely avoided

Basic Concept: Performance Specification:

1

2

• International patent application, PCT/DE2010/000230, WO2010/099788A1, „Apparatus for transmitting torque“ (Europe/USA/China), 2009.

• Patent application, “Magnetic Fluid Control”, 10 2011 119 919.9, Ostwestfalen-Lippe University of Applied Sciences, Germany, 2011.

permanent magnet

3. Concept for MRF-clutch system with fluid control


Magnification shown in

the simulation results

2

1Basic concept:

B B

Dis

en

ga

ge

d m

od

e

En

ga

ge

d

mo

de

s

En

gag

ed

mo

de

Development of a new clutch systems for energy-efficient use:

• Proof-of-Concept demonstrator as a clutch based on the fluid control for high rotational

speeds using magnetic forces of a permanent- and electro-magnet.

3. Modeling of the magnetic field and the fluid movement


• using an approach adapted from the theoretical model of ferrohydrodynamics

• investigation of magnetic fields and their interaction with a magnetic fluid by magnetic

dipoles (fluid treated as a continuum with magnetic properties)

• dipoles are accelerated in the magnetic field by Kelvin forces fK

• theory for the model based on Maxwells equations for the magnetic field and Navier-

Stokes equations for the fluid flow

• magnetic volume force from a calculated magnetic field coupled with a fluid-flow

problem

• two fluid domains (MRF and air) need to be considered due to the only partly filled

shear gaps

• the interface between MRF and air is modeled by the level set method

MJrgvvvv

H

Tp

t0

2 )(

MJHMf H T

K 00

Navier-Stokes equations Kelvin force


3. Simulation of MRF-clutch system with fluid control

Simulation of fluid flow induced by magnetic fields for a clutch system

• Results showing the transition from coupling to idle mode in standstill

(rotational speed n = 0 min-1).

1.6T

0.4T

0T

0.6T

0.8T

1.0T

1.4T

0.2T

1.2T

100%

50%

0%

volu

me f

raction

of M

RF

M

agnetic

flux d

ensity

t=0ms t=10ms t=95ms

3. Realization of MRF-Clutch System with Fluid Control


Design figures

shear gap radius: 63 mm

main length: 71,5 mm

outer diameter 140 mm

driven shaft

stator/housing

winding

shear gap

drive shaft

permanent magnet

driven shaft

permanent magnet

MRF

drive shaft

3D sectional

model of realized

clutch system

sectional model

magnification

of shear gap

2

1

Concept finalized for realization with two magnetic cascades for increasing the maximum coupling torque.

-50 -40 -30 -20 -10 0 10 20 30 40 50

0

2

4

6

8

torq

ue

T in

Nm

n=500min-1

-50 -40 -30 -20 -10 0 10 20 30 40 50-6

-4

-2

0

2

time t in ms

cu

rre

nt

I in

A

desired current

measured current

-5 -4 -3 -2 -1 00

1

2

3

4

5

6

7

8

current i in A

torq

ue

T in

Nm

n=3000min-1

n=2000min-1

n=1000min-1

n=500min-1

n=250min-1

n=100min-1

3. Measurements of MRF-clutch system with fluid control


• Measurement of the steady state characteristic of torque behavior.

• Measurement of the transient behavior for the transition from engaged in disengaged mode.

Discussion:

• High torque capability and idle mode with complete drag torque free operation.

• Fast response times by switching from the engaged in disengaged mode within 15ms.

transient behavior steady state characteristic

P

E

HIL test rig

electrical

drive

MRF clutch axle / street



Integration in the power train of hybrid electrical cars (HEV):

• A fast response time, an excellent controllability and no idle losses of the presented clutch systems

can provide significant benefits in terms of safety and efficiency for application in HEV.

• Investigations utilizing a HIL test system, shows a good performance for application as switching

elements in power trains of HEV, e.g. as disengagement clutch in axle-split-hybrids.

0 5 10 15 20 25 300

2000

4000

rota

tio

nal sp

eed

in m

in-1

driven shaft

drive shaft

0 5 10 15 20 25 30-10

-5

0

5

cu

rren

t I in

A

0 5 10 15 20 25 30-5

0

5

10

time t in s

tran

sm

itte

d t

orq

ue

T in

Nm

Acceleration

(combustion engine and

electrical drive)

Acceleration

(combustion engine )

Deceleration

(combustion engine and

electrical drive)

Disengagement Engagement



Presenting the demonstrator on an “Island of Excellence” at FISITA 2012 in Bejing:

Starting new research work on MRF-clutches for application in transmissions:

• For application in transmission for HEV, the torque-

to-volume density needs to be increased.

• Initiation of a new research project “PHEVplus”

beginning 2014 (partner GKN Driveline International,

financially funded by BMWi.

• Using the great opportunity of

presenting the work on MRF-

clutches and brakes

Realized

Demonstrator

Güth, D.; Schamoni, M.; Cording, D.; Maas, J.: New technology for a high dynamical MRF-clutch for safe and energy-efficient

use in powertrains. Student Journal of FISITA, FISITA 2012 World Automotive Congress, Peking, 2013.


5. Conclusion

• Necessity of reducing the viscous losses of MRF actuators was shown by

measurements of an actuator with maximum rotational speeds.

• Idea of moving MRF within the shear gap for reducing the viscous drag losses in

the disengaged mode was introduced. • Approach for a novel actuator design was presented.

• The functionality of the basic concepts is proven by measurement with a first

design.

• Development, modeling and simulation of an enhanced clutch design were shown

and a realized proof-of-concept clutch actuator was introduced. • Measurements with the proof-of-concept clutch actuator were performed that show

the feasibility and the high potential of MRF clutches without idle losses e.g. for the

use in drive trains of vehicles. • Improved concepts with higher torque exploitation are introduced.

• Considering the application in hybrid electrical cars (e.g. axle-split-parallel-hybrids), a fast response time, an excellent controllability and no idle losses of the

presented clutch systems provide significant benefits in terms of safety and efficiency.

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

[email protected]

Phone: +49 (0)5261 702-192

Dirk Güth M.Sc

[email protected]

Phone: +49 (0)5261 702-489

Research project PHEVplus, funded by the Federal

Ministry for Economic Affairs and Energy (BMWi) of

Germany under grant number 01MY13004B.