Vehicle Dynamics - Corrsys-Datron

fearfuljewelerΠολεοδομικά Έργα

16 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

436 εμφανίσεις

Vehicle Dynamics/ Wus/ 10 May 20121
Vehicle Dynamics
Longitudinal
Transversal
Vertical
Vehicle Dynamics/ Wus/ 10 May 20122
Longitudinal Dynamics
￿
Evaluation of acceleration and
braking behavior
￿
Driving resistance: Wheel, air,
rising and acceleration
resistance (energy requirement)
￿
Engine characteristics, gear
balance (engine supply)
￿
Transmission of drive and brake
forces (driving limits)
Planar model of longitudinal
dynamics
Vehicle Dynamics/ Wus/ 10 May 20123
Transversal Dynamics
Linear one-track model
￿
Evaluation of steering behavior,
transversal acceleration a, <0,4 g
￿
Steady-sate circular-course drive
￿
Self-steering behavior
￿
Characteristic and critical speed
￿
Non-steady-state circular-course drive
￿
Transverse behavior
￿
Steering angle / yaw angle
￿
Parameter influences:
￿
Self-steering behavior
￿
Mass m, moment of inertia J
￿
Slip stiffness of the tires C
v, C
h
Vehicle Dynamics/ Wus/ 10 May 20124
What is self-steering behavior?
￿
Self-steering is a set of vehicle steering behaviors that are of
independent driver steering input!
￿
In case of self-steering, the driver does not steer the vehicle,
the steering angle does!
￿
Self-steering behavior is influenced by:
￿
Wheel load distribution
￿
Kinematics
￿
Suspension elasticity
￿
Wheel characteristics
Vehicle Dynamics/ Wus/ 10 May 20125
How is self-steering identified?
￿
Steady-state circular-course test drive
￿
Methodology:
￿
Constant radius
￿
Speed is increased from slow coasting
￿
If the steering angle must be changed to maintain the circular path,
self-steering effects are present
￿
The additional angle that the wheel is turned is called slip
angle
Vehicle Dynamics/ Wus/ 10 May 20126
Oversteer, understeer,
neutral steering
￿
Oversteer

F
< 

R
￿
Understeer 

F
> 

￿
Neutral

F
= 

R
Vehicle Dynamics/ Wus/ 10 May 20127
Steady-state circular course drive
￿
Sensor list for steady-state circular-course test drive
Vehicle Dynamics/ Wus/ 10 May 20128
Evaluation for ISO 4138
￿
Presentation of results, steering wheel angle over
lateral acceleration in right turn and left turn
￿
Sideslip angle over lateral acceleration in right turn and
left turn
￿
Roll angle over lateral acceleration in right turn and left
turn
￿
Steering wheel torque over lateral acceleration in right
turn and left turn
Vehicle Dynamics/ Wus/ 10 May 20129
Vertical dynamics
￿
Evaluation of vibration behavior
based on two primary criteria:
￿
1. Driving safety (wheel load)
￿
2. Driving comfort (body acceleration)
￿
Parameter influences:
￿
body mass mA
￿
tire mass mR
￿
body spring CA
￿
tire spring CR
￿
body damper dA
Two-mass
suspension model
Vehicle Dynamics/ Wus/ 10 May 201210
The tire
￿
The tire is the supporting element between the road and the
car body.
It essentially counters the vertical force F
z
(gravitational
force) of the vehicle.
￿
The elasticity of the tire generates a wheel footprint.
Vehicle Dynamics/ Wus/ 10 May 201211
The tire
￿
FR rolling resistance
￿
FX reaction force
￿
FZ gravitational force
￿
FN normal force
￿
The rolling resistance generates
the reaction force.
Vehicle Dynamics/ Wus/ 10 May 201212
Slip angle
Vehicle Dynamics/ Wus/ 10 May 201213
Tire slip angle & wheel force sensor
Kistler Wheel Force Sensor
Vehicle Dynamics/ Wus/ 10 May 201214
Correvit
®
S-Sensors
￿
Measured variables
:
￿
Vl
= longitudinal velocity
￿
IVI = magnitude velocity
￿
Vt
= transversal velocity
￿
a= angle
Vl


IVI
Vt
Correvit
®
is a registered trademark of Kistler Holding AG
Vehicle Dynamics/ Wus/ 10 May 201215
DCA System for measurement of
Dynamic Camber Angle
Vehicle Dynamics/ Wus/ 10 May 201216
RV-4 Wheel Vector Sensor
With Correvit SFII-P sensor
￿
Position in X,Y, Z axes
￿
Camber
￿
Wheel steer
Vehicle Dynamics/ Wus/ 10 May 201217
All in one
Vehicle Dynamics/ Wus/ 10 May 201218
Sensor list for ESP
Vehicle Dynamics/ Wus/ 10 May 201219
What is the function of ESP
￿
Yaw becomes sideslip angle affected and slip angle
optimized in the desired direction
UndersteerOversteer
Stabilizing
yaw moment
with
ESP
with
ESP
without ESP
without ESP
Vehicle Dynamics/ Wus/ 10 May 201220
Sine steer
Vehicle Dynamics/ Wus/ 10 May 201221
Testing for ESP development
￿
Steady-state circular-course driving
￿
Braking when cornering
￿
Double track-changing
￿
Transient behavior
￿
Steering angle jump
￿
Sinusoidal steering angle input
Vehicle Dynamics/ Wus/ 10 May 201222
Objective testing methods
￿
Performance of tests that can evaluate steering and yaw
behavior simultaneously.
￿
Additional important points of the test are:
￿
Reproducibility
￿
Robustness against environmental and interfering influences
￿
Relevance
Vehicle Dynamics/ Wus/ 10 May 201223
Vehicle Evaluation 1
￿
The following parameters are considered in vehicle
evaluation:
￿
Temperature
￿
Humidity
￿
Ground covering µ-jump
￿
Brand and age of the wheels
Vehicle Dynamics/ Wus/ 10 May 201224
Potential testing methods
￿
Sine Steer: Based on a real world double-lane change
maneuver
￿
Pulse Steer: based on the assumption that an impulse input
signal activates the vehicle via a large frequency range
Vehicle Dynamics/ Wus/ 10 May 201225
ABS anti-lock braking system
￿
The main criteria for the assessment of ABS are:
￿
Steerability
￿
Stability
￿
Optimum braking distance
Vehicle Dynamics/ Wus/ 10 May 201226
Important demands on ABS
￿
The main criteria for the assessment of ABS are:
￿
Steerabilityand driving stability must remain effective when braking
￿
Steering response must minimized
￿
The control function must be OK over the entire
speed range
￿
The system must provide optimum utilization of wheel grip on the track
surface; steerability must have priority over reduction of braking
distance.
Vehicle Dynamics/ Wus/ 10 May 201227
General control principles
￿
Single Wheel control
￿
Each wheel has its own sensor that controls brake pressure exerted on
the wheel to achieve maximum braking efficiency.
￿
Select-low control
￿
The wheel with the least grip determines brake pressure exerted on
both wheels
￿
Select-high control
￿
The wheel with the most grip determines brake pressure exerted on
both wheels.
Vehicle Dynamics/ Wus/ 10 May 201228
Sensor list for ABS
Vehicle Dynamics/ Wus/ 10 May 201229
Wheel slip
￿
Drive slip and brake slip are measured with:
Wheel pulse transducer + Correvit L-350
Vehicle Dynamics/ Wus/ 10 May 201230
Formula for wheel slip
Vehicle Dynamics/ Wus/ 10 May 201231
Rollover/fishhook test
￿
Why is the rollover test required?
Vehicle Dynamics/ Wus/ 10 May 201232
Fishhook test
￿
Is a test developed by NHTSA in the USA
￿
It is used to evaluate vehicle safety in rollover tests
￿
The testing results are used for vehicle evaluation
Vehicle Dynamics/ Wus/ 10 May 201233
Performance
￿
The Fishhook test is applied to measure the speed at which
the wheels lift off the ground (< 4 cm), before the vehicle rolls
over
￿
The path the vehicle follows is shaped like a fishhook, which
gives the test its name
Vehicle Dynamics/ Wus/ 10 May 201234
NHTSA Fishhook test
Vehicle Dynamics/ Wus/ 10 May 201235
Fishhook testing
￿
Arizona based company
testing replication of vehicle
stability under extreme
circumstance
￿
Fishhook Testing at variable
velocities
￿
Equipment Utilized
￿
AB Dynamics Steering Robot
￿
S-400 / SFII
￿
HT-500 (4)
Vehicle Dynamics/ Wus/ 10 May 201236
Fishhook testing
￿
Testing Video 1
￿
Testing Video 2
Vehicle Dynamics/ Wus/ 10 May 201237
NHTSA rollover stability
￿
Steering wheel angle versus time
Steering wheel angle, roll stability triggered
-400-300-200-100
0
100200300400
00.511.522.533.5
Time secs
Stering wheel angle degrees
Vehicle Dynamics/ Wus/ 10 May 201238
NHTSA rollover stability
Roll angle roll stability triggered
-4-3-2-1
0
1
2
3
4
5
00.511.522.533.5
Time secs
Rollangle degrees
Roll rate, Roll stability triggered
-20-15-10
-5
0
5
1015
00.511.522.533.5
Time secs
Roll rate degrees per sec.
￿
Roll angle versus time
￿
Roll rate versus time
Vehicle Dynamics/ Wus/ 10 May 201239
Reproducibility
￿
The Fishhook test requires high reproducibility of the test
drives
￿
This is only possible if a steering robot system is used
￿
We present the steering robot system of Anthony Best
Dynamics Ltd.
￿
This system is applied worldwide
Vehicle Dynamics/ Wus/ 10 May 201240
International standards
￿
Road vehicles Lateral transient response test methods 
open-loop test methods ISO 7401
￿
Passenger cars Braking in a turn-open loop test procedure
ISO 7975
￿
Road vehicles Passenger car/trailer combinations 
Lateral stability test ISO 9815
￿
Road vehicles Measurement of road surface friction ISO
8349
￿
Passenger cars Steady-state circular driving behavior 
open-loop test procedure ISO 4138
Vehicle Dynamics/ Wus/ 10 May 201241
International standards
￿
Road vehicles Transient open-loop response test method
with one period of sinusoidal input ISO 8725
￿
Road vehicles Transient open-loop response test method
with one period of sinusoidal input ISO 8725
￿
Road vehicles Transient open-loop response test method
with pseudo-random steering input ISO 8726
￿
Road vehicles Vehicle dynamics and road-holding ability 
Vocabulary ISO 8855