Transcript Brief Report on R&D specific attachment on prototype (AAC.1)

ISP RAS
ATS
AdCAS is the multicriterion automatic adaptive control
system for active car suspension
AdCAS is the program for on-board computer
The AdCAS program is created on basis of new
Autonomous Adaptive Control (AAC) method, which is
elaborated in Institute for System Programming of Russian
Academy of Sciences
B. Сommunisticheskaya, 25,
Moscow, 109004, Russia.
[email protected]
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§1. Preamble
1.1 Goals of suspensions
A car suspension must carry out several functions simultaneously:
The suspension must increase
the comfort of car passengers
by means of compensation of
the road roughness
The suspension must increase
the car stability at maneuvers:
on turns, at braking and
starting
The suspension must increase
the car controllability
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Some goal of the suspension
are inconsistent.
So the comfort demands a
soft suspension while
stability and controllability
demand a rigid one.
An optimal compromise
between requirements of
comfort and stability is found
and frozen in parameters of
ordinary "passive"
suspensions.
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§1. Preamble
1.2 Active suspensions
The fast and smart changes of current properties of the
suspension during one car trip are desirable, as requirements
on comfort, stability and controllability are changing during
the trip.
The appropriate mode depends from common conditions (turn radius, speed
value or other conditions of the motion) and from inner conditions - state of
the car, number of passengers, value of luggage, state of the suspension
units, etc.
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§1. Preamble
1.3 Approaches to control
1. Manually control
In many cars with “active suspension” the driver himself
plays a part of the “control system”. The driver himself
chooses "comfortable" or "sport" style of the car motion
and switches manually chosen mode of the “active”
suspension.
Drawbacks: it distracts the driver attention and gives only
a few variants of modes.
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§1. Preamble
2. Automatic control on basis of the mathematical
models of the car suspension
Most of controllers for car suspensions are based on the
mathematical models of the car suspension properties
Drawbacks: nobody can create the precise mathematical
model of car suspension because it is very complex
controlled object, which changes during process of
control
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§1. Preamble
3. Automatic control on basis of the systems
working with empirical knowledge
New control methods based on knowledge are used in lots
of applications during last years.
These are such systems as:
artificial neural networks
fuzzy logic systems
expert systems
etc.
Advantages: these methods allow to avoid development of
mathematical model of controlled object.
Drawbacks: These control systems usually use only
knowledge was found earlier. The knowledge is bad
updated in real time of control.
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§2. The AdCAS System
§2. The AdCAS System
The idea is to use the new Autonomous
Adaptive Control (AAC) method for control of
active suspension
Advantages:
The real current properties of car and its suspension are used.
This AAC control system automatically finds, accumulates and
uses empirical knowledge in one process.
The AAC control system is multicriterion automatic adaptive
control system
The control system works similarly to the child who for the
first time sits on a bicycle and he is gradually trained without
any use of the mathematical model describing bicycle
motion.
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§2. The AdCAS System
The AAC control system
Controlled
object
AAC Control System solves
a set of problems in one
process. These problems
are:
Sensors
Environment
Actuators
• Pattern formation and
recognition
• Knowledge obtaining and
accumulation
• Emotions simulation
• Decision-making
• and some others
The AAC System
structure
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§2. The AdCAS System
The principle of working of
the AAC control system
 The AAC Control System (CS) finds out the functional properties
of given controlled object by means of trial-and-error method.
 The AAC CS operates by such information units as patterns.
 Analyzing the prehistory the CS finds out non-random patterns
of the controlled object properties (knowledge) and accumulates
the knowledge in the “Knowledge Base”.
 The “Emotions Subsystem” allows to appraise the quality of the
knowledge elements.
 The “Decision Making” subsystem uses the accumulated
knowledge and qualitative appraisals to choose best action in
current state of the controlled object.
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§2. The AdCAS System
The Program Simulation of the
Controlled Suspension Motion
Virtual Test Bench
Sensors Unit
3. Sensors data
preprocessing
2. The sensors
Controlled Object and
Environment
7. The
Road
AdCAS Control
System
1. The Car and its
suspension
4. Control, criteria
and goal functions
6. The actuator
5. Output connector
Executors Unit
All blocks of the System are simulated by the program
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§2. The AdCAS System
Some features of the simulation
program objects:
Car and its suspension
1/4 of the car (it is enough for the control system)
Road surface
components: the Gaussian, the Poisson (obstacles),
the periodical component, the trend
Sensors
accelerometers (~ +/- 15 G, ~ 300 g, ~ 45x90 mm)
AdCAS Control
on basis of the AAC method
Actuator
The version 1 - the high pressure active actuator in
parallel with shock absorber
The version 2 – the shock absorber with variable
viscosity
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§2. The AdCAS System.
Version 1
The prospective actuator for the
AdCAS System.
Version 1
Elastic
element
Road
profile
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Mass
of car
body
Actuator
and shock
absorber
Mass of
suspension
The Actuator must create force
pulses T(t) along the
vertical axis. This type
actuator exists on the
market (for example similar
one is used in ABC active
suspension of Mercedes CL
500)
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§2. The AdCAS System.
Version 1
Goal Functions
The AdCAS System allows to have a few goal functions
simultaneously. We considerate such goal functions as:
1) increase of passenger comfort
2) increase of car stability
3) increase of car controllability
It is possible to set other goal functions and criteria if they can be
formulated algorithmically
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§2. The AdCAS System.
Version 1
The Goal Function 1
Smoothing of vertical fluctuations
of the car body
The time curve of car body motion contains fluctuations with frequency and amplitude, which
are harmful for men. The AdCAS Control System calculates “desirable" curve of car body
motion and takes it as the goal function. The “desirable" curve has no harmful fluctuations.
Real the road profile
The car body “desirable” motion
The AdCAS System gives the means "to adhere" car body to the given “desirable” curve.
The Control System makes decisions and the actuator pushes the car body position to this
“desirable” curve.
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§2. The AdCAS System.
Version 1
The Goal Function 1
Example of AdCAS control process
Weak car vibrations
Heavy car vibrations
Control forces
No Control forces
The real
road surface
The real road surface
Under the AdCAS control
Without the control
One can see that the AdCAS System depress the fluctuations of
car body
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§2. The AdCAS System.
Version 1
Quantitative estimation of the quality of the
control process
Control quality can be estimated by means of several criteria
Without the
control
Under the
AdCAS
control
1. The quality estimation on the basis of current deviation of real and desirable motions
Under the
AdCAS
control
Without the
control
2. The quality estimation on the basis of current dispersion of the car body fluctuations
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§2. The AdCAS System.
Version 1
Power Spectrums
Under the
AdCAS
control
Without the
control
3. The quality estimation on the basis of power spectrums
The
fluctuations in
the band from
1Hz to 2Hz are
depressed by
the AdCAS
System
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The ratio of these spectrums
demonstrates in how many times
the AdCAS system suppresses
fluctuations
on
different
frequencies.
The abscissa axis corresponds to the
frequencies from 0.2Hz to 8Hz.
Y-axis corresponds to the ratio of
spectrums.
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§2. The AdCAS System.
Version 1
Adaptability of the AdCAS
System
The AdCAS system is adaptive. It can automatically adapts to many parameters of
the suspension and the car. The adaptation can occur directly while the AdCAS
System operates.
The necessity of adaptation is caused by the fact that many car
parameters can vary even during one trip. For example next
parameters can be changed:
The mass of the car
The mass distribution in the car body
The elasticity of springs and shock-absorbers
etc.
Following table and picture show permissible variation of the
parameters:
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§2. The AdCAS System.
Version 1
Table 1.
Permissible variation of the car parameters:
30%
Parameter variation
65%
100%
135%
350
%
M - the car body mass (1/4 of the car), kg
90
190
290
390
1000
m - the suspension mass (1/4 of the car), kg
18
38
59
80
200
504
1092
1681.2
2269
5884
C1(1) - the elasticity of the spring
5700
12350
19000
25650
66500
C1(2) - the elasticity of the spring
11400
24700
38000
51300
13300
0
300
650
1000
1350
3500
3
4
Ct - the elasticity of the tire
a - absorber coefficient
№№ of the curves on the figure
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1
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5
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§2. The AdCAS System.
Version 1
The example: permissible variation of the car mass M:
•For demonstration of adaptive properties of the AdCAS system we show
for example the series of diagrams reflecting the acceptable change of car
body mass M (see Table 1 above).
We can see that
the AdCAS
system adapts to
changes of mass
M of the car.
The AdCAS
System has same
possibilities for
adaptation to
other parameters
of the car
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§2. The AdCAS System.
Version 1
The Goal Function 2
Use of the system AdCAS for increase of
car stability
As the AdCAS system «understands» the car properties and is able to handle it, we can set
any desirable trajectory of vertical motion of car body and AdCAS will backtrace it.
The turn
Let us desire that the car should not be inclined on turns.
Under the turn sensor
command the AdCAS
control system sets the
«goal» - to hold the
«desirable» motion
curve of the car body on
the constant level.
The actuator forces the car body to stay at the constant level
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§2. The AdCAS System.
Version 1
Here we see how the car with the AdCAS System passes a turn.
The actuator actively prevents the lowering of the car body.
The AdCAS
struggles with
obstacles in the
road
simultaneously
with the turn
The AdCAS holds the car without an inclination
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§2. The AdCAS System.
Version 1
Here we see how the car without the AdCAS System passes a turn.
The car body sags down.
The centrifugal force on the turn presses the one side of the car body downwards.
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§2. The AdCAS System.
Version 1
The Goal Function 3
Increase of the car stability in the situation
of the inroad on an obstacle
When one wheel runs into an
obstacle (a stone) the
automobile experiences an
overturning moment of force.
Let us require to heft opposite side of car body at
the situation. In this case the AdCAS sets, for
example, such a “desirable” curve of the car body
motion. Then the AdCAS actuator achieves this
motion.
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§2. The AdCAS System.
Version 1
On this picture we can see the AdCAS actuator achieving the desirable
motion.
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§2. The AdCAS System.
Version 1
It is possible to set to AdCAS some other desirable motions,
for example at starting or braking etc.
So, we see that the AdCAS system is multipurpose and many - criterion control
system
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§2. The AdCAS System.
Use of the AdCAS system for
work with other actuators
The AAC system,
on the basis of
which the AdCAS
system is
constructed, works
with a controlled
object and
environment as
with a black box
without the
mathematical
model of controlled
object.
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Environment
Controlled
Executor
Object
AAC
System
Controlled
Object
Sensors
The working
principle of the AAC
control system does
not depend from
kind of its Actuator,
Sensors, Controlled
Object and
Environment.
The control system
controls everything
that lays outside.
Give the control
system a controlled
object and it will
control it.
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§2. The AdCAS System.
Version 2
Shock-absorber with variable
viscosity as the Actuator of the
AdCAS system
Shock-absorbers with variable viscosity are used in active suspensions as
“actuator” too. Such shock-absorbers are filled by a magneto-rheological liquid
MRF (suspended a fine metal powder in the oil). Under action of a magnetic
field such liquid changes its viscosity. It is possible to change viscosity up to
1000 times per one second.
For example such kind of shock-absorbers are used in suspensions MagneRide.
Installing such a shock-absorber on a car, one faces a question - how to control by
it? All traditional ways of control we have specified above. An analytical
calculation of the “control law” is possible but it will not be exact for the
concrete car.
With the help of the AdCAS system it is possible to find the optimum characteristic
of such shock-absorber for the given car. Such characteristic automatically will
change while car properties change.
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§2. The AdCAS System.
Version 2
The second version of the AdCAS system uses this type actuator. The Knowledge
Base of this version of the AdCAS System can be interpreted as optimal empirically
found characteristic of the shock-absorber.
The usual characteristic of the
shock-absorber.
The characteristic empirically found
by the system AdCAS.
F
F
v
a)
a)
a
)
v
b)
b)
The opportunities of such “actuator” appreciably less than the opportunities of the
actuator considered above. Therefore it is difficult to achieve such strong effect as in the
first case. Nevertheless the car motion smoothness also grows.
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§3. The analysis of the
Market of Active
Suspensions
The active suspensions are the important
direction of development of car industry today
Many leading firms in the current time actively
develop active suspensions
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§3. The Market
State and Dynamics of Market of
Active Suspensions
The leading car industry companies for a long time and intensively
carry out researches and introduce active suspensions.
For the majority of other automobile firms active suspensions - one
of main announced innovations (since 1996 on 2000 in USA are registered
264 patents on active suspensions).
Lotus Cars Ltd. Formula 1 - 1981
Lotus –99T Formula 1 - 1987
McLaren Formula 1
Williams FU-11 Formula 1 - 1987
Mercedes Benz S600
Mercedes Benz CL + Lotus (“ABC”) - 2001
General Motors
Cadillac Evog - 1999
Cadillac Seville
Cadillac STS + General Motors ( “Magnaride”)
Cadillac Escalade 2002 ( “StabiliTrak”) - 2002
Cadillac rodster
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Ferrari
Ford
Lincoln
Opel Omega
Audi Allroad Quattro
Renault Safrane
Renault Koleos – Off Road
Citroen (“Hydractive”)
Volvo + Lotus
Mitsubishi Sigma - 1992
Toyota Land Cruiser 100 – Off Road
Nissan
etc.
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§3. The Market
The most advanced models for
today
1. Active suspension “Active Body Control” (ABC) for
Mercedes Benz CL500
Accelerometers, active hydraulic actuator and microprocessor (control
algorithm is unknown) are used in the suspension.
Introducing in serial cars CL500 and CL600 from 2001 is announced.
The suspension was developed during 12 years.
2. Active suspensions “Magnaride” and “StabiliTrak” are elaborated
by Cadillac & General Motors
Shock-absorbers with variable viscosity and a microprocessor (control
algorithm is unknown) are used.
The installation of these suspensions on serial Cadillac STS (de luxe sedan) and
Cadillac Escalade 2002 is planned since January 2001.
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§3. The Market
We can see the tendency - use of active suspensions are
extending from special cars (Formula 1, etc.) and
expensive cars (Mercedes Benz, Cadillac etc.) to middle
class cars (Opel Omega etc.) in 2001 - 2002.
Cost of
cars
use long since
Formula 1
use now
Off Roads and
SUVs
start use today
Expensive cars
Mercedes Benz CL500 $135 000
The users and
manufacturers are
interested in new
development with
lower parameter
“price / quality"
plan to use
soon
Middle
class cars
1980
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1990
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2000
2010
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§3. The Market
Segments of the Market of active
suspensions
Off road cars and SUVs
Passenger cars high and
middle classes
Buses
Ambulance cars
(reanimation)
Formula 1
Cars for transportation of special
cargoes (super fragile, explosive)
Another special cars and vehicles
Electric transport (railroad,
monorail railway)
Prime segment of the
Market for AdCAS
system
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§3. The Market
In microprocessor control systems
two classes of algorithms are used:
1.
Algorithms of control on the basis of mathematical models of
controlled objects.
2.
Algorithms of systems «of artificial intelligence» - control on
the basis of empirical knowledge without mathematical
models of objects (new modern perspective direction).
That is close to the
AdCAS approach
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§3. The Market
Qualitative comparison of two
classes of control algorithms
Algorithms of control
on the basis of
mathematical models of
controlled objects
Merits
Wide experience of use.
Determinancy
Algorithms of systems
«of artificial
intelligence»
Adaptability to the current
properties of the object.
Uselessness of mathematical
model
Demerits
Too great complexity of math.
models on a limit of possibility of
calculations
Lacks inherent in search
mode of functioning
Smaller adequacy to the current
properties of object.
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§3. The Market
The general tendency of development of
control systems of suspensions
A lot of
mechanical
parts
A lot of
mathematics
Mechanic
Systems
Use of
Mathematical
Models
Empirical
Knowledge and
Self learning
Intelligent
Control
tendency
AdCAS
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Conclusion
The automatically controlled active suspensions are the
important direction of development of car industry today
The main difference of the AdCAS System from traditional
control systems is that the mathematical model of the
automobile is not used.
Differences of the AdCAS System from existing “intelligent”
control systems: multi-criteria control, universality, "system
approach" - integrated approach of the decision of several
necessary functions simultaneously. These properties refer to
perspective direction, to which all other approaches aspire.
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The End
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