Model Based Control for a Pressure Control Type CVT

Wansik Ryu, Juhyun Nam, Hyunsoo Kim, Sungkyunkwan University

Yongjoon Lee,Hyundai Motor Company

Dynamic System Design & Control Lab.Sungkyunkwan University

2

Introduction

Pressure Control TypeFlow Control Type

Pressure control is easier than the flow control in maintaining the desired CVT speed ratio.

Pressure control system has an advantage of preventing the belt from slippage in active manner.

3

Design a ratio controller for pressure control type CVT

Design a model based controller

Investigate model based controlled CVT shift performance

Purpose of Study

4

Pressure Control Type Ratio Control Valve

Solenoid presusre Feed back pressureSpring force

5

CVT System Dynamics

FrM

PBXXKPAPAP

PS

PSPSPSPSPSsolPS )( 0331

dt

dXAQ

dt

dPXAV ppp

pppP dt

di

di

dX

dt

dX pp

Force equilibrium of the spool motion

State equation of the primary pressure

CVT shift dynamics by Ide (1995)

Pi

PPidt

di

P

ppP

)(

)()( *

where

6

Pressure Characteristics at a Steady State

Pri

mar

y p

ress

ure

, bar

Secondary pressure, bar

0

Psol=6bar

Psol=6.3bar

Psol=2bar

Psol=4bar

40

30

20

10

10 20 30 400 50

7

0 10 20 30 40

Secondary pressure,bar

20

10

0Pri

mar

y p

ress

ure

, bar

40

30 i = 0.5

i = 1.0

i = 2.5

P-line

springScentss

PcentppSP FFPA

FPAFF

*

*

/

SSP

SPP PAA

FFPlineP /

1/

0.6

0.7

0.8 1

1.3

1.6 2

2.4

84 0

0.3

0.6

0.9

0

0.5

1

1.5

2

2.5

Thrust ratio

Speed ratio

Torque ratio

2.5

2

1.5

1

0.5

0

0.90.6

0.300.

6

2.51

Speed ratio

Torqueratio

Thrustratio

SP FF /

8

Prediction of Shift Performance by P-line

10 20 30 400

Pri

mar

y p

ress

ure

, bar

Secondary pressure, bar

0

Psol=6.3bar

Psol=2bar

40

30

20

10

50

Pup

Pup

Pdown

-Pup

Pdown

Pdown

A

B

CShift speed at B is the

fastest among the

three points, A, B

and C

9

Prediction of Shift Performance by P-line

Time, sec

2

1.5

1

0.5

0

Sp

ee

d r

ati

o

2.5

3

1.0 2.0 3.00

A

BC

2

1.5

1

0.5

0

2.5

3

A

BC

Simulation

Experiment

10

Experiments for Ratio Control Performance

CVT Test rig

11

Block Diagram of Ratio Control with PID Control

dutyRCSV

RCV

PID controller

Pp

id

CVTi

Psol

+

-

12

Control Performance

0

0.5

2

1.5

1

2.5

Sp

eed

rat

io

3T=5sec

0

0.5

2

1.5

1

2.5

Sp

eed

rat

io

3

Time, sec

0 5 10 15

T=8sec

idi

id i

There exist small response lag in the CVT ratio response

13

0 Ro

tati

on

al s

pee

d,

rpm

0

0.5

2

1.5

1

2.5

Sp

eed

rat

io

3 1200

1000

800

600

400

200

00 1 32 4 5

10

40

30

20

Time, sec

Pre

ssu

re, b

ar

6 7

50

Pp

Ps

Psd

i

id

s

p p

s

id

i

Psd

Ps

Pp

(a)

(b)0.6sec

Ratio Response for Stepwise Input of Ps

14

Steady State Pressure Characteristics with P-line

10 20 30 400

Pri

mar

y p

ress

ure

, bar

Secondary pressure, bar

0

Psol=6.3bar

Psol=2bar

40

30

20

10

50

Psol=2.5bar

Psol=3.5bar

15

Model Based Control

duty_conRCSV

RCV

PID controllerwith anti-windup

Pp

id

CVTi

Psol

+

-

P-linePs

+

+

Steady state RCV model

Pp*

duty_FF

16

Model Based Control

0 10 20 30 40 Secondary pressure,bar

40

30

20

10

0Pri

mar

y p

ress

ure

, bar

(a)

0 10 20 30 40 Secondary pressure,bar

40

30

20

10

0Pri

mar

y p

ress

ure

, bar

(a)

00 20 6040 80 100

10

40

30

20

50

RCSV duty, %P

rim

ary

pres

sure

, bar

Ps=10bar

Ps=20bar

Ps=40bar

Ps=30bar

(b)

00 20 6040 80 100

10

40

30

20

50

RCSV duty, %P

rim

ary

pres

sure

, bar

Ps=10bar

Ps=20bar

Ps=40bar

Ps=30bar

(b)

17

Model Based Control

0 Ro

tati

on

al s

pe

ed

, rp

m

0

0.5

2

1.5

1

2.5

Sp

ee

d r

ati

o

3 1800

1500

1200

900

600

300

00 1 32 4 5

10

40

30

20

Time, sec

Pre

ss

ure

, b

ar

6 7

50

0

20

80

60

40 Du

ty,

%

100

Pp

Ps

Psd

i

DutyFF

s

p

(b) Model based controller

id

(a)

0 Ro

tati

on

al s

pe

ed

, rp

m

0

0.5

2

1.5

1

2.5

Sp

ee

d r

ati

o

3 1800

1500

1200

900

600

300

00 1 32 4 5

10

40

30

20

Time, sec

Pre

ss

ure

, b

ar

6 7

50

0

20

80

60

40 Du

ty,

%

100

Pp

Ps

Psd

i

DutyFF

s

p

(b) Model based controller

id

(a)

p

ss

i

id

PsdPs

Duty_FF

Pp

0 Ro

tati

on

al

sp

ee

d,

rpm

0

0.5

2

1.5

1

2.5

Sp

ee

d r

ati

o

3 1800

1500

1200

900

600

300

00 1 32 4 5

10

40

30

20

Time, sec

Pre

ss

ure

, b

ar

6 7

50

Pp

Ps

Psd

i

id

s

p

(a) PID controller(b)

0 Ro

tati

on

al

sp

ee

d,

rpm

0

0.5

2

1.5

1

2.5

Sp

ee

d r

ati

o

3 1800

1500

1200

900

600

300

00 1 32 4 5

10

40

30

20

Time, sec

Pre

ss

ure

, b

ar

6 7

50

Pp

Ps

Psd

i

id

s

p

(a) PID controller(b)

p

s

i

id

PsdPs

Pp

18

Conclusion

A P-line is proposed from the steady state relationship

between the primary pressure and secondary pressure

CVT shift performance is predicted using the P-line

Linear control algorithm such as PID type controller can be

used for the pressure control type CVT

A model based control algorithm is proposed

The model based control is able to provide improved tracking

performance and robustness