Regenerative Braking Algorithm For a HEV with CVT

Ratio Control During Deceleration

Hoon Yeo, Donghyun Kim, Sungho Hwang, Hyunsoo

Kim Sungkyunkwan University

Dynamic System Design & Control Lab.Sungkyunkwan University

2

Motor

Battery

+ -

Transmission

IC Engine

Regenerative Braking

Generator

Introduction

3

EPA75

Urban

Austr.Urban

ECE-15Japan1015

NewYorkCity

Traction energyKJ

Total4000 6480 3478 1675 998

Perkm.

377 606 437 402 519

Braking energyKJ

Total 1934 4195 953 888 878

Perkm.

182 392 120 213 461

Percentage of braking energy to total traction energy (%)

48.3 64.7 27.5 53.0 88.8

Traction and Braking Energy Consumption

4

the regenerative braking force is not large enough to

cover the required braking force the regenerative braking can not be used for many

reasons such as high state of charge or high

temperature of the battery to increase the battery life

REGENBRAKING

FRICTIONBRAKING+

5

Develop a regenerative braking control algorithm

Develop a prototype electro-hydraulic controlled

regenerative braking module

Propose a CVT ratio control algorithm to obtain maximum

regenerative energy during deceleration

Objectives

6

Hybrid Electric Vehicle

+ -Battery

Engine

Motor &Generator

InverterREGEN

Hydraulic Module

REGENHydraulic Module

Pedal

BCUBCU

MCUMCU

HEV-ECUHEV-ECU

7

Master cylinder

BCU

PP

Motor

Pump

Accumulator

Proportional

reducing valve

PP

HEV - ECU

sON_OFF switch

Relief valve

PHPL

Stroke simulator

Vacuum

booster

Front wheel cylinder Rear wheel cylinder

Powerpack

Regenerative Braking Hydraulic Module

8

Regenerative Braking Algorithm

REG

R

TNiT

•

•

1W 2W

Regenerative torque applied to the front wheel

1W

2W

1W (SOC)

2W (Velocity)

9

SOC, %

0

0.5

1

0 20 40 60 80 100

Wei

ght

fact

or, W

1W

eigh

t fa

ctor

, W2

VelocityV1 V2

1

Weight Factor for Regenerative Braking

10

Regenerative Braking Algorithm

Ff HYD = Fbf – FREGEN

b

fHYDtf ra

FRP

2

Regenerative braking force

Hydraulic braking force required at the front wheel

Front wheel cylinder pressure equivalent to FfHYD

RTREGENF

tR

11

Braking Forces on the Front and Rear Wheel

Rea

r br

ake

forc

e

Front brake force

P

brF

bfFRICTIONFREGENF

bfF

12

Pedal input

Rear pressure

Ideal distribution of braking force

Battery SOC,Velocity,

CVT ratio

Rear braking force

Front braking force, Fbf

Regenerative torque,TREGEN

Regenerative force FREGEN

21RT WWiNTREGEN

Fbf > FREGENNoYes

PF = 0

Regenerative braking+

Friction braking

Hydraulic module

Regenerative braking

Fbf = FREGEN

Friction braking

FbfFRICTION=Fbf-FREGEN

b

bfFRICTIONtf

rA

FRp 2

bfFRICTIONF

Flow Chart for Regenerative Braking

13

CVT Ratio Control

0 6000500040003000200010000

- 40

- 80

Motor speed, rpm

Mo

tor

torq

ue,

Nm

88%

86%

84%82%

80%

78%70%60%

OOL

Motor efficiency

14

CVT Ratio Control

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

500 1500 2500 3500 4500 5500

Demand braking torque

Wheel power

A

B

0

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

500 1500 2500 3500 4500 5500

Demand braking torque

Wheel power

A

B

60000 30000

- 80

Mo

tor

torq

ue

, N

m OOL

Motor speed, rpm

- 50

Optimal operating line in regenerative braking

15

CVT Ratio ControlFlow chart of CVT ratio control

Brake=on?NoYes

Motor optimal operation

Desired CVT ratio

Engine optimal operation

Calculate wheel power

Calculate desired speedω gen_desired from OOL

Pedal input

f

tdmd NV

Ri

)

16

HEV Powertrain Model

17

Engine Stroke volume

Maximum torque

1600cc

140Nm

Motor 10kW Motor torque at base rpm 50Nm

Vehicle

CVT gear ratio range

Final reduction gear ratio

Vehicle mass

Front project area

Drag coefficient

Tire radius

0.455 ~ 2.47

5.763

1380 kg

1.964 m2

0.346

0.279 m

Vehicle Data

18

Simulation Results

A

Pre

ssu

re,

bar

0

30

CVT REGEN(rear)

REGEN(rear)

REGEN(front)

CVT REGEN(front)

(d)

(e)

19

Simulation Results

Motor speed, rpm

Mo

tor

torq

ue,

Nm

-100

-50

0

50

100

0 1000 2000 3000 4000 5000

CVT REGEN

REGEN

(f)

OOL

20

Motor Operation Trajectories for FUDS

Motor speed, rpm

Mo

tor

torq

ue

, Nm

-100

-50

0

50

100

0 1000 2000 3000 4000 5000 6000

OOL

-100

-50

0

50

100

0 1000 2000 3000 4000 5000 6000

Mo

tor

torq

ue,

Nm

CVT REGEN

REGEN

Simulation Results

21

Simulation Results

95

100

105

%

Battery SOCFuel Economy

CVT REGEN

REGEN

Comparison of fuel economy and final battery SOC for FUDS

22

Regenerative braking algorithm is proposed.

Prototype electro-hydraulic regenerative braking

module is developed.

CVT ratio control algorithm during deceleration is

suggested.

Fuel economy is improved by 4 percent for FUDS

Conclusion