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. zhdanov@ispras.ru ISP RAS Slide 2 / 40 ATS §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 ISP RAS 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. Slide 3 / 40 ATS §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. ISP RAS Slide 4 / 40 ATS §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. ISP RAS Slide 5 / 40 ATS §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 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 ISP RAS Slide 6 / 40 ATS §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. ISP RAS Slide 7 / 40 ATS §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. ISP RAS Slide 8 / 40 ATS §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 ISP RAS Slide 9 / 40 ATS §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. ISP RAS Slide 10 / 40 ATS §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 ISP RAS Slide 11/ 40 ATS §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 ISP RAS Slide 12 / 40 ATS §2. The AdCAS System. Version 1 The prospective actuator for the AdCAS System. Version 1 Elastic element Road profile ISP RAS 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) Slide 13 / 40 ATS §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 ISP RAS Slide 14 / 40 ATS §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. ISP RAS Slide 15 / 40 ATS §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 ISP RAS Slide 16 / 40 ATS §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 ISP RAS Slide 17 / 40 ATS §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 ISP RAS 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. Slide 18 / 40 ATS §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: ISP RAS Slide 19 / 40 ATS §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 ISP RAS 1 Slide 20 / 40 2 5 ATS §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 ISP RAS Slide 21 / 40 ATS §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 ISP RAS Slide 22 / 40 ATS §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 ISP RAS Slide 23 / 40 ATS §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. ISP RAS Slide 24 / 40 ATS §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. ISP RAS Slide 25 / 40 ATS §2. The AdCAS System. Version 1 On this picture we can see the AdCAS actuator achieving the desirable motion. ISP RAS Slide 26 / 40 ATS §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 ISP RAS Slide 27 / 40 ATS §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. ISP RAS 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. Slide 28 / 40 ATS §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. ISP RAS Slide 29 / 40 ATS §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. ISP RAS Slide 30 / 40 ATS §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 ISP RAS Slide 31 / 40 ATS §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 ISP RAS 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. Slide 32 / 40 ATS §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. ISP RAS Slide 33 / 40 ATS §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 ISP RAS 1990 Slide 34 / 40 2000 2010 ATS §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 ISP RAS Slide 35 / 40 ATS §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 ISP RAS Slide 36 / 40 ATS §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. ISP RAS Slide 37 / 40 ATS §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 ISP RAS Slide 38 / 40 ATS 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. ISP RAS Slide 39 / 40 ATS The End Slide 40 / 40