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ISP RASISP RAS ATSATS

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]

ISP RASISP RAS ATSATS Slide 2 / 40Slide 2 / 40

mailto:[email protected]





§1. Preamble

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

Some goal of the suspension Some goal of the suspension

are are inconsistentinconsistent.. So the comfort demands a So the comfort demands a

softsoft suspension while suspension while stability and controllability stability and controllability demand a demand a rigidrigid one. one.

An optimal An optimal compromisecompromise between requirements of between requirements of comfort and stability is found comfort and stability is found and and frfrozen in parameters of ozen in parameters of oordinary "passive" rdinary "passive" suspensions. suspensions.

A car suspension must carry out several functions simultaneously:


1.1 Goals of suspensions

1.2 Active suspensions

The The fast and smart changeschanges of current properties of the of current properties of the suspension during one car trip are suspension during one car trip are desirabledesirable, as requirements , as requirements on comfort, stability and controllability are changing during on comfort, stability and controllability are changing during the trip. the trip.

The appropriate mode depends from common conditions (turn radius, speed The appropriate mode depends from common conditions (turn radius, speed value or other conditions of the motion) and from inner conditions - state of value or other conditions of the motion) and from inner conditions - state of the car, number of passengers, value of the car, number of passengers, value of luggage, state of the suspension the suspension units, etc.units, etc.

§1. Preamble


1.3 Approaches to control

In many cars with “active suspension” In many cars with “active suspension” the driver himself plays a part of the “control system”. The driver himself himself chooses "comfortable" or "sport" style of the car motion chooses "comfortable" or "sport" style of the car motion and switches and switches manuallymanually chosen mode of the “active” chosen mode of the “active” suspension. suspension.

Drawbacks: it distracts the driver attention and gives only a few variants of modes.

1. Manually control

§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 networksfuzzy logic systemsexpert systemsetc.

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.

§1. Preamble

ISP RASISP RAS ATSATSSlide 7 / 40Slide 7 / 40

§2. The AdCAS SystemThe 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.

§2. The AdCAS System


The AAC control system

The AAC System structure

SensorsSensors

ActuatorsActuators

EnvironmentEnvironment

AAC Control System solves AAC Control System solves a set of problems in one a set of problems in one process. These problems process. These problems are:are:

• Pattern formation and Pattern formation and recognitionrecognition

• Knowledge obtaining and Knowledge obtaining and accumulationaccumulation

• Emotions simulationEmotions simulation• Decision-making Decision-making

• and some othersand some others

Controlled Controlled objectobject



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.


The Program Simulation of the Controlled Suspension Motion


Virtual Test Bench

All blocks of the System are simulated by the program

Sensors UnitSensors Unit

Controlled Object and Controlled Object and EnvironmentEnvironment

AdCAS Control AdCAS Control SystemSystem

7. The Road

Executors UnitExecutors Unit

6. The actuator 5. Output connector

1. The Car and its suspension

2. The sensors

4. C4. Control, ontrol, criteria criteria andand goal functions goal functions

3. Sensors data preprocessing

ISP RASISP RAS ATSATSSlide 11/ 40Slide 11/ 40

Some features of the simulation program objects:


on basis of the AAC methodAdCAS Control

The version 1 - the high pressure active actuator in

parallel with shock absorber

The version 2 – the shock absorber with variable viscosity

Actuator

accelerometers (~ +/- 15 G, ~ 300 g, ~ 45x90 mm)Sensors

components: the Gaussian, the Poisson (obstacles),

the periodical component, the trendRoad surface

1/4 of the car (it is enough for the control system)Car and its suspension


The prospective actuator for the AdCAS System. Version 1

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)

§2. The AdCAS System. Version 1


Elastic Elastic elementelement

Mass ofMass of suspensionsuspension

Road Road profileprofile

ActuatorActuator and shock and shock absorberabsorber

Mass Mass of car of car bodybody

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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

Slide 14 / 40Slide 14 / 40


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 profileReal the road profile The car body “desirable” motionThe 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.


Slide 15 / 40Slide 15 / 40


The Goal Function 1

Example of AdCAS control process


Weak car vibrations

Control forces

The real

road surface

Heavy car vibrations

No Control forces

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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Quantitative estimation of the quality of the control process


Control quality can be estimated by means of several criteria

1. The quality estimation on the basis of current deviation of real and desirable motions1. The quality estimation on the basis of current deviation of real and desirable motions

2. The quality estimation on the basis of current dispersion of the car body 2. The quality estimation on the basis of current dispersion of the car body fluctuationsfluctuations

Under the AdCAS control

Without the control


Without the control


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3. The quality estimation on the basis of 3. The quality estimation on the basis of power spectrums

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.



Without the control

Power Spectrums

The fluctuations in the band from 1Hz to 2Hz are depressed by

the AdCAS System

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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:

Slide 19 / 40Slide 19 / 40



Table 1.

Permissible variation of the car parameters:

Parameter variation

M - the car body mass (1/4 of the car), kg

m - the suspension mass (1/4 of the car), kg

Ct - the elasticity of the tire

C1(1) - the elasticity of the spring

C1(2) - the elasticity of the spring

a - absorber coefficient

№№ of the curves on the figure

65%

190

38

1092

12350

24700

650

30%

90

18

504

5700

11400

300

1 2

135%

390

80

2269

25650

51300

1350

100%

290

59

1681.2

19000

38000

1000

3 4

350%1000

200

5884

66500

133000

3500

5

Slide 20 / 40Slide 20 / 40



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

Slide 21 / 40Slide 21 / 40


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 turnLet 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 Goal Function 2

Use of the system AdCAS for increase of car stability


The actuator forces the car body to stay at the constant level

Slide 22 / 40Slide 22 / 40


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 holds the car without an inclination

The AdCAS struggles with obstacles in the road simultaneously with the turn


Slide 23 / 40Slide 23 / 40

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.



Slide 24 / 40Slide 24 / 40

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.



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.

Slide 25 / 40Slide 25 / 40

On this picture we can see the AdCAS actuator achieving the desirable motion.



Slide 26 / 40Slide 26 / 40

So, we see that the AdCAS system is multi-So, we see that the AdCAS system is multi-purpose and many - criterion control purpose and many - criterion control systemsystem

It is possible to set to AdCAS some other desirable motions, for example at starting or braking etc.




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.

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.

Environment

Controlled Object

AACSystem

Sensors

ExecutorControlled Object

§2. The AdCAS System.

Slide 28 / 40Slide 28 / 40

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.


Slide 29 / 40Slide 29 / 40


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.

a) 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.


The characteristic empirically found by the system AdCAS.

Slide 30 / 40Slide 30 / 40

b) b) a)

a)

F F

v v

§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

Slide 31 / 40Slide 31 / 40

State and Dynamics of Market of Active Suspensions

The leadingThe leading car industry car industry companies for a long time and intensively companies for a long time and intensively carrycarry out researches out researches and introduce and introduce active suspensionactive suspensionss. For the majority of other automobile firms active suspensions - one For the majority of other automobile firms active suspensions - one of main announced innovations (of main announced innovations (since 1996 on 2000 in USA are registered since 1996 on 2000 in USA are registered 264 patents on active suspensions264 patents on active suspensions).).


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.

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

§3. The Market

Slide 32 / 40Slide 32 / 40

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.


§3. The Market

Slide 33 / 40Slide 33 / 40

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.

1980 1990 2000 2010

Middle class cars

Formula 1 use long since

Off Roads and SUVs

use now

Expensive cars

start use today

plan to use soon

Cost of cars

The users and manufacturers are interested in new development with lower parameter “price / quality"

Mercedes Benz CL500 $135 000


§3. The Market

Slide 34 / 40Slide 34 / 40

Segments of the Market of active suspensions

Off road cars and SUVs

Passenger cars high and middle classes

BusesAmbulance cars (reanimation)

Formula 1Cars 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

§3. The Market

Slide 35 / 40Slide 35 / 40

In microprocessor control systems two classes of algorithms are used:

Algorithms of control on the basis of mathematical models of controlled objects.

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

§3. The Market

Slide 36 / 40Slide 36 / 40

Qualitative comparison of two classes of control algorithms

Algorithms of control on the basis of mathematical models of controlled objects

Algorithms of systems «of artificial intelligence»

Merits

Demerits

Adaptability to the current properties of the object.

Uselessness of mathematical model

Wide experience of use.

Determinancy

Too great complexity of math. models on a limit of possibility of calculations

Smaller adequacy to the current properties of object.

Lacks inherent in search mode of functioning


§3. The Market

Slide 37 / 40Slide 37 / 40

The general tendency of development of control systems of suspensions


A lot of mechanical parts

A lot of mathematics

Empirical Knowledge and Self learning

tendency

MechanicSystems

Use of Mathematical

Models

IntelligentControl

AdCAS

§3. The Market

Slide 38 / 40Slide 38 / 40

ConclusionThe 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.


The End

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