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Published on January 16, 2008

Author: Berta

Source: authorstream.com

Slide2:    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. zhdanov@ispras.ru   §1. Preamble:  §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 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. A car suspension must carry out several functions simultaneously: 1.1 Goals of suspensions 1.2 Active suspensions:  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. §1. Preamble 1.3 Approaches to control :  1.3 Approaches to 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. 1. Manually control §1. Preamble 2. Automatic control on basis of the mathematical models of the car suspension :  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 Q*(wr+2rt345)+986asd= 986asd-578+987-89jh+87+ +2434asdas-ff*1234-S123+gf- +mn2352898n=98gfg89-76g=765+6= 123456ab-cde+f+fgg55-66jg=gfgh5590= cnsjc89322rq876gjhgi69-u86g65764890-=80iy96y §1. Preamble 3. Automatic control on basis of the systems working with empirical knowledge:  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. §1. Preamble §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. §2. The AdCAS System The AAC control system :  The AAC control system       The AAC System structure  Sensors Actuators Environment AAC Control System solves a set of problems in one process. These problems are: Pattern formation and recognition Knowledge obtaining and accumulation Emotions simulation Decision-making and some others Controlled object §2. The AdCAS System The principle of working of the AAC control system :  The principle of working of the AAC control system       §2. The AdCAS 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 :  The Program Simulation of the Controlled Suspension Motion §2. The AdCAS System Virtual Test Bench All blocks of the System are simulated by the program Sensors Unit Controlled Object and Environment AdCAS Control System 7. The Road Executors Unit Slide12:  Some features of the simulation program objects: §2. The AdCAS System Slide 12 / 40 The prospective actuator for the AdCAS System. Version 1:  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 element Mass of suspension Road profile Actuator and shock absorber Mass of car body Slide 13 / 40 Goal Functions :  Goal Functions The AdCAS System allows to have a few goal functions simultaneously. We considerate such goal functions as: §2. The AdCAS System. Version 1 increase of passenger comfort increase of car stability increase of car controllability It is possible to set other goal functions and criteria if they can be formulated algorithmically Slide 14 / 40 Slide15:  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. 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. §2. The AdCAS System. Version 1 Slide 15 / 40 Slide16:  The Goal Function 1 Example of AdCAS control process §2. The AdCAS System. Version 1 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 Slide 16 / 40 Quantitative estimation of the quality of the control process:  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 motions 2. The quality estimation on the basis of current dispersion of the car body fluctuations Under the AdCAS control Without the control Under the AdCAS control Without the control §2. The AdCAS System. Version 1 Slide 17 / 40 Slide18:  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. §2. The AdCAS System. Version 1 Under the AdCAS control Without the control Power Spectrums The fluctuations in the band from 1Hz to 2Hz are depressed by the AdCAS System Slide 18 / 40 Adaptability of the AdCAS System :  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. §2. The AdCAS System. Version 1 Following table and picture show permissible variation of the parameters: Slide 19 / 40 Slide20:  §2. The AdCAS System. Version 1 Table 1. Permissible variation of the car parameters: Slide 20 / 40 Slide21:  §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 Slide 21 / 40 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 Goal Function 2 Use of the system AdCAS for increase of car stability §2. The AdCAS System. Version 1 The actuator forces the car body to stay at the constant level Slide 22 / 40 Slide23:  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 §2. The AdCAS System. Version 1 Slide 23 / 40 Slide24:  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. §2. The AdCAS System. Version 1 Slide 24 / 40 Slide25:  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. §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. Slide 25 / 40 Slide26:  On this picture we can see the AdCAS actuator achieving the desirable motion. §2. The AdCAS System. Version 1 Slide 26 / 40 Slide27:  So, we see that the AdCAS system is multi-purpose and many - criterion control system It is possible to set to AdCAS some other desirable motions, for example at starting or braking etc. §2. The AdCAS System. Version 1 Slide 27 / 40 Slide28:  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. §2. The AdCAS System. Slide 28 / 40 Shock-absorber with variable viscosity as the Actuator of the AdCAS system:  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. §2. The AdCAS System. Version 2 Slide 29 / 40 Slide30:  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. §2. The AdCAS System. Version 2 The characteristic empirically found by the system AdCAS. Slide 30 / 40 b) b) a) a) F F v v Slide31:  §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 / 40 State and Dynamics of Market of Active Suspensions:  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). §3. The Market Slide 32 / 40 The most advanced models for today :  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 / 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. :  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 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 / 40 Segments of the Market of active suspensions:  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 §3. The Market Slide 35 / 40 In microprocessor control systems two classes of algorithms are used: :  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). §3. The Market Slide 36 / 40 Qualitative comparison of two classes of control algorithms :  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 / 40 The general tendency of development of control systems of suspensions :  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 Mechanic Systems Use of Mathematical Models Intelligent Control AdCAS §3. The Market Slide 38 / 40 Conclusion:  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. Slide 39 / 40 The End:  The End Slide 40 / 40

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