Microcar handling behavior for both the steady state and transient maneuver: Numerical VS...

Microcar handling behavior for both the steady state and transient maneuver:

Numerical VS Experimental Comparison for Model validation

Date: 2012, Sept. 18

Marco E. Pezzola Elisabetta Leo Niccolò Taroni

Chung C. Cheng

Soluzioni Ingegneria Padana RicambiKYMCO Italia

Luca Paletti

AUTHORS:

18/09/2012 N°2

NUMERICAL

EXPERIMENTAL

Target/Motivations

Sample Microcar

TARGET

To investigate the microcar’s handling behavior in both transient and steady state

manoeuvers

TARGET

To create a complete CarMaker numerical model of the vehicle to simulate sample vehicle dynamic

performances

MATCH

18/09/2012 N°3

Vehicle overview

Lightweigth quad.

Engine power 4 kW

Maximum speed (declared) 45 km/h

2 front wheels drive

Sample Microcar

18/09/2012 N°4

Vehicle overview: dimensions / weight

Vehicle maximum permissible weight [kg]

Maximum permissible weight 640

Vehicle weight without passengers [kg] Declared Measured

total weight 380 417

front axle weight 230 243

rear axle weight 150 174

18/09/2012 N°5

How to reach the target

MEASUREMENT SYSTEM

HANDLING

EXPERIMENTAL

TESTS

Good?

Suspension curve Center of mass position

Manoeuvres D(t), v(t), r(t)…

VEHICLE DESIGN/TUNING

Yes: reliable numerical model

No: Model tuning

NUMERICAL MODEL CarMaker©

TRANSIENT STEADY STATE

18/09/2012 N°6


MEASUREMENT SYSTEM

HANDLING

EXPERIMENTAL

TESTS

Good?




No: Model tuning




18/09/2012 N°7

Measurement system

Front suspension potentiometer (Left & Right)

Trailing arm suspension

Mc Pherson suspension

Rear suspension potentiometer (Left & Right)

18/09/2012 N°8

Measurement system

Rear magnetic speed sensor (only right side)

Front magnetic speed sensor (only right side)

18/09/2012 N°9

Measurement system

Steering potentiometer Steering Wheel

Steering gearbox

Measured Distance

18/09/2012 N°10

Measurement system

Gyroscope

Z gyro

1 gyroscope (z axis)

Yaw speed (for handling

tests)

18/09/2012 N°11

Measurement system

Accelerometers (for handling tests)

Xacc

Zacc

Yacc

3 capacitive accelerometers (x,y,z)

Lateral acceleration Longitudinal acceleration

18/09/2012 N°12

Measurement system

Data recorder (AIM)

AIM

via USB

Measurement data

GPS

GPS Antenna

18/09/2012 N°13


MEASUREMENT SYSTEM

HANDLING

EXPERIMENTAL

TESTS

Good?




No: Model tuning




18/09/2012 N°14

Front suspension curve

ΔL/Δz (average left/right) 0,824

GROUND

ZGROUND

LSPRING


y = -0,8164x + 356,07 R² = 0,999

290

300

310

320

330

340

350

360

0 10 20 30 40 50 60 70 80

Spri

ng

len

gth

ΔL

[mm

]

Wheel travel Δz [mm] - from fully extended condition

Lever ratio (DL / DZ)

18/09/2012 N°15

Front suspension curve

ΔL/Δz 0,8257

Ground reduced suspension stiffness

9,633 N/mm

Spring stiffness 14,2 N/mm

Spring pre-load 552 N

GROUND

FWHEEL


ZGROUND

LSPRING

y = 9,1953x + 465,06 R² = 0,9926

0

200

400

600

800

1000

1200

0 10 20 30 40 50 60 70 80

Me

asu

red

wh

ee

l lo

ad [

N]

Wheel travel Δz [mm] - from fully extended conditiom

Ground reduced suspension stiffness

18/09/2012 N°16

wheel steering angle vs. XSTEER

y = 310,27x - 890,67

-800

-600

-400

-200

0

200

400

600

800

0,000 1,000 2,000 3,000 4,000 5,000 6,000

LEFT

Ste

erin

g A

ngl

e d

[°]

RIG

HT

Measured distance Xsteer [V]

Steering calibration curve -690° / 660°

wheel steering angle vs. ground steering angle

D

d

∆= 0.04 ∙ 𝛿

d

Steering potentiometer calibration

1 2

18/09/2012 N°17

Center of mass identification

Longitudinal / lateral position of the center of mass:

706

1740

644

1320

Measures in mm

281

Vertical position of the center of mass:

18/09/2012 N°18


MEASUREMENT SYSTEM

HANDLING

EXPERIMENTAL

TESTS

Good?




No: Model tuning




18/09/2012 N°19

CarMaker: numerical model design

CarMaker model generator

«Vehicle Data Set - Masses»

Parameters Set values

Front unsprung masses 15 kg

Rear unsprung masses 14 kg

Wheel center - z coordinate 285 mm

Overall dimensions

Only vehicle...

18/09/2012 N°20

CarMaker: main body geometry and mass

Center of gravity coordinates

Only vehicle...

18/09/2012 N°21

CarMaker: suspensionssprings

Front suspension data from experimental…

Rear suspension data from experimental…

…to numerical model…

Only vehicle...

18/09/2012 N°22

CarMaker: suspensionskinematics

Front suspension data from experimental…

Rear suspension data from experimental…

…to numerical model…

Only vehicle...

18/09/2012 N°23

CarMaker: suspensionssteering

Only vehicle...

18/09/2012 N°24


MEASUREMENT SYSTEM

HANDLING

EXPERIMENTAL

TESTS

Good?




No: Model tuning




18/09/2012 N°25

Model VS Experimental: matching…

1° static asset of car with no passengers on board

EXPERIMENTAL

FRONT REAR

F under tire [N] 1190 856

F on spring [N] 1342 790

ΔL of spring [mm]

(including pre load length)

55,6 38

18/09/2012 N°26


1° static asset of car with no passengers board

NUMERICAL Running a stand still manouvre…

Only vehicle...

18/09/2012 N°27


1° static asset of car with no passengers on board

Very good match!

Only vehicle...

Load distribution: vehicle without passengers – Experimental vs. numerical

Position Average measured ground force Numerical ground

force [N] Error [%] [kg] [N]

Rear wheel 87,3 855,9 855,8 -0,0

Front wheel 121,4 1190,4 1189,9 -0,0

Total car weight 417,2 4092,6 4091,4 -0,0

Springs in static conditions: vehicle without passengers – Experimental vs. numerical

Numerical data Experimental data Error [%]

Front Rear Front Rear Front Rear Spring compression

(∆L [mm]) 54,5 36,7 55,6 38,0 -1,9 -3,4

Force acting on the spring (F [N])

1325,7 777,3 1342,0 790,6 -1,2 -1,7

Ground forces:

Springs forces:

18/09/2012 N°28


MEASUREMENT SYSTEM

HANDLING

EXPERIMENTAL

TESTS

Good?




No: Model tuning




18/09/2012 N°29

STEADY STATE Experimental tests: STEERING PAD

Steering pad with FIXED SPEED • Speed is fixed • Steering is increased until the

car reaches the maximum lateral acceleration

• The trajectory is a circle with decreasing radius

-10 -5 0 5 10 15

-22

-20

-18

-16

-14

-12

-10

-8

-6

-4

-2

0Trajectory

[m]

[m]

18/09/2012 N°30

Experimental tests: STEERING PAD

ROLL LATERAL ACCELERATION

0 10 20 30 40 50 60 70-0.5

0

0.5

1

1.5

2

2.5

3

3.5

4

X: 60.46

Y: 3.753

time [s]

roll

[°]

0 10 20 30 40 50 60 70-10

-9

-8

-7

-6

-5

-4

-3

-2

time

Late

ral A

cc.[

m/s

2]

Lateral IN vehicle

Absolute Lateral

Example: steering pad at about 30 km/h on asphalt

STEADY STATE

18/09/2012 N°31

Managing the acquired data it’s possible to observe the vehicle behavior. 2 instruments are available…

Experimental tests: STEERING PAD STEADY STATE

18/09/2012 N°32

0 5 10 15 20 25 300

1

2

3

4

5

6

7

8

9

Ground steering angle [°]

La

tera

l a

cce

lera

tio

n [m

/s2]

Handling diagram #1 ASPHALT

25 km/h data

25 km/h fitting

27 km/h data

27 km/h fitting

30 km/h data

30 km/h fitting

neutral steering

Results: STEERING PAD

Example: steering pad FIXED SPEED: asphalt

At top acceleration level, the steering angle increases while the acceleration remains stable

Interpolant polynomial fitting ^6

8.2 m/s2

+V02

STEADY STATE

Handling diagram #1

ASPHALT

18/09/2012 N°33

0 5 10 15 20 25 300

1

2

3

4

5

6

7

8

9


La

tera

l a

cce

lera

tio

n [m

/s2]

Handling diagram #1 CEMENT

20 km/h data

20 km/h fitting

25 km/h data

25 km/h fitting

30 km/h data

30 km/h fitting

neutral steering


Example: steering pad FIXED SPEED:

Interpolant polynomial fitting ^6

7.5 m/s2

The potential friction on concrete is smaller than on asphalt: the max lateral acceleration is smaller

+V02

STEADY STATE

Handling diagram #1

CONCRETE

18/09/2012 N°34

0 5 10 15 20 25 300

1

2

3

4

5

6

7

8

9


La

tera

l a

cce

lera

tio

n [m

/s2]

Handling diagram #1 CEMENT

20 km/h data

20 km/h fitting

25 km/h data

25 km/h fitting

30 km/h data

30 km/h fitting

neutral steering

0 5 10 15 20 25 300

1

2

3

4

5

6

7

8

9


La

tera

l a

cce

lera

tio

n [m

/s2]

Handling diagram #1 ASPHALT

25 km/h data

25 km/h fitting

27 km/h data

27 km/h fitting

30 km/h data

30 km/h fitting

neutral steering

Results: STEERING PAD STEADY STATE

Handling diagram #1

18/09/2012 N°35

Managing the acquired data it’s possible to observe the vehicle behavior. 2 instruments are available…

Experimental tests: STEERING PAD STEADY STATE

𝜕(𝛿 − 𝛿0)

𝜕𝐿𝑎𝑡. 𝐴𝑐𝑐.> 0

Understeering

𝜕(𝛿 − 𝛿0)

𝜕𝐿𝑎𝑡. 𝐴𝑐𝑐.< 0

Oversteering

18/09/2012 N°36


Example: steering pad at about 30 km/h

The vehicle is understeering on both the surfaces

𝜕(𝛿 − 𝛿0)

𝜕𝐿𝑎𝑡. 𝐴𝑐𝑐.> 0 Understeering

0 0.5 1 1.5 2 2.5 3 3.5 40

1

2

3

4

5

6

7

8

9

Ground steering angle - Ackermann angle [°]

La

tera

l a

cce

lera

tio

n [m

/s2]

Handling diagram #2

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50

2

4

6

8

10

12

Ground steering angle - Ackermann angle [°]

La

tera

l a

cce

lera

tio

n [m

/s2]

Handling diagram #2

cement

asphalt

fitting cement

fitting asphalt

STEADY STATE

Handling diagram #2

CONCRETE

18/09/2012 N°37


MEASUREMENT SYSTEM

HANDLING

EXPERIMENTAL

TESTS

Good?




No: Model tuning




18/09/2012 N°38


NUMERICAL Planning a steady state/transient manouvre…

Dynamic behavior of car with 2 passengers

test model

18/09/2012 N°39


Dynamic behavior of car with 2 passengers – steady state test

Steering pad test #1 – Asphalt (µ=0.9) Experimental INPUTS

Steering pad test #1 – Surface: asphalt NUMERICAL vs. EXPERIMENTAL COMPARISON

ASPHALT

18/09/2012 N°40


Steering pad test #1 – Asphalt (µ=0.9) Experimental INPUTS

Steering pad test #1 – Surface: asphalt NUMERICAL vs. EXPERIMENTAL COMPARISON

HANDLING DIAGRAM #1

Dynamic behavior of car with 2 passengers – steady state test ASPHALT

18/09/2012 N°41


Dynamic behavior of car with 2 passengers – steady state maneuver

Numerical VS experimental matching errors

STEADY STATE TESTS Test type Physical quantity Value Experimental Numerical Error [%]

Asphalt, 25 km/h

Lat. acceleration [m/s

2]

Max value 8,2 8,157 0,52

Mean Square Error 0,20

Yaw speed [°/s] Max value 80,3 81,4 1,37


Roll angle [°] Max value 5,3 5,517 4,09


Asphalt, 30 km/h


2]

Max value 7,7 7,783 1,08






Concrete, 25 km/h


2]

Max value 7,6 7,6 0,00






Very good match (max error 7%)!

18/09/2012 N°42


MEASUREMENT SYSTEM

HANDLING

EXPERIMENTAL

TESTS

Good?




No: Model tuning




18/09/2012 N°43

Experimental tests: STEERING STEP

How it works: • Speed is fixed • Steering is zero, then at time T0

the driver applies a 180° step on the steering wheel and holds it for 4 – 5 seconds

T0

1 2 3 4 5 6 7 8-20

0

20

40

60

80

100

120

140

160

180

Time [s]

Ste

ering a

ngle

[°]

Steering angle history

TRANSIENT

18/09/2012 N°44

Results: STEERING STEP

Example: steering step at about 40 km/h (cement)

This is the point where the driver begins to turn the steering wheel from 0° to 180° (to the left)

-30 -25 -20 -15 -10 -5 00

5

10

15

20

25

30Trajectory

[m]

[m]

D = 0

D = 180

TRANSIENT

18/09/2012 N°45

Results: STEERING STEP

Example: steering step at about 40 km/h (cement)

4 5 6 7 8 9 10 11-0.5

0

0.5

1

1.5

2

2.5

3

3.5

Time [s]

Roll

angle

[°]

Roll angle history

4 5 6 7 8 9 10 11-45

-40

-35

-30

-25

-20

-15

-10

-5

0

5

Time [s]

Yaw

speed [

°/s]

Yaw speed history

steering wheel from 0° to 180° (to the left)

4 5 6 7 8 9 10 11-0.5

0

0.5

1

1.5

2

2.5

3

3.5

Time [s]

Roll

angle

[°]

Roll angle history

𝜌∗ = Steady value

Same for yaw speed and lateral acceleration…

Yaw speed

Roll angle

TRANSIENT

18/09/2012 N°46

Results: STEERING STEP TRANSIENT

Increasing with speed (quadratic trend) Increasing with steering angle (linear trend)

Lateral acceleration: average value

Same for yaw speed and roll angle …

18/09/2012 N°47


MEASUREMENT SYSTEM

HANDLING

EXPERIMENTAL

TESTS

Good?




No: Model tuning




18/09/2012 N°48

Steering step test #1 – Surface: asphalt– Speed: ≈ 30 km/h NUMERICAL vs. EXPERIMENTAL COMPARISON

0 1 2 3 4 5 6 7-5

-4

-3

-2

-1

0

1

Time [s]

Car

alH

ori [

m/s

2]

Experimental data

Numerical data

0 1 2 3 4 5 6 7-0.5

0

0.5

1

1.5

2

2.5

3

3.5

4

Time [s]

Car

Roll

[deg]

Experimental data

Numerical data

0 1 2 3 4 5 6 7-5

0

5

10

15

20

25

30

35

Time [s]

Car

Yaw

Rate

[deg/s

]

Experimental data

Numerical data

Steering step test #1 – Surface: asphalt (µ=0.87) – Speed: ≈ 30 km/h

Experimental INPUTS

0 1 2 3 4 5 6-250

-200

-150

-100

-50

0

50

Time [s]

DM

Ste

er

Ang [

deg]

0 1 2 3 4 5 60

5

10

15

20

25

30

35

Time [s]

Car

v [

km

/h]


Dynamic behavior of car with 2 passengers – transient manoeuver ASPHALT

18/09/2012 N°49


Dynamic behavior of car with 2 passengers – transient maneuver

Numerical VS experimental matching errors

TRANSIENT STATE TESTS Test type Physical quantity Value Experimental Numerical Error [%]

Step steer 180° on asphalt, 30

km/h

Lat. acceleration [m/s2] Average value 4,20 4,16 0,95

Yaw speed [°/s] Average value 29,50 30,87 4,64

Roll angle [°] Average value 3,17 3,14 0,95

Step steer 180° on concrete, 20

km/h




Step steer 180° on concrete, 30

km/h




Very good match (max error 8.7%)!

18/09/2012 N°50

CONCLUSIONS

• A reference microcar has been instrumented. The geometrical/mass distribution/suspension/steering parameters have been achieved in order to implement a numerical model.

• Experimental tests have been performed: steering pad at constant speed (steady state) and step steer at different speeds (transient). Tests have been performed on different surfaces.

• Numerical model has been implemented in CarMaker®.

• Experimental and numerical results have been compared in order to increase model reliability; the matching between experimental and numerical tests is acceptably good (the worst error < 10%).

FUTURE DEVELOPMENT: the microcar numerical model will allow to run sensitivity analysis in order to define a new model vehicle layout

18/09/2012 N°51

Thanks for your attention!

Come to visit us @ the exhibition stand of:

Pezzola & Associati

Microcar handling behavior for both the steady state and transient maneuver: Numerical VS...

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