Automatic Control Systems and Control of Vibrations in Vehicles Car

Automatic Control Systems and Control of Vibrations in Vehicles Car Rafał Burdzik, Łukasz Konieczny, and Błażej Adamczyk Silesian University of Technology, Gliwice, Poland {Rafal.Burdzik,Lukasz.Konieczny,Blazej.Adamczyk}@polsl.pl Abstract. Growing customer requirements for comfort of vehicles more often become refer to vibrations that affect the people in transport. At the same time each car put into service must has the appropriate parameters traction to the road surface responsible for the safety. Due to the nature of the vibration transmitted to the vehicle body vibration requirements are of the often contradictory. Therefore, an intense research on modern control systems, active vibration damping system parameters are require. This paper presents the advantages and disadvantages associated with the suspension systems of vehicles of conventional and active and semiactiv based on the elements of a controlled characteristics of both elastic elements and damping. It was suggested the possibilities of advanced signal processing methods application developed in vibration research. Keywords: automatic control system, active and semiactive suspension system. 1 Introduction Vibration propagate and influence people via the vehicle structure, i.e. the frame or the body. Studying vibration phenomena in automotive vehicles should primarily pertain to their effects on men and the chosen structural elements of a vehicle [1]. In the scope of the impact on structural elements, one should perceive vibrations in terms of destructive factors, which can be affected on in the technical states considered reliability states of a motor vehicle [2]. Mechanical vibrations occurring in a working environment may be classified as general vibrations, i.e. those affecting the human organism via lower extremities, the pelvis and the back. The second category comprises local vibrations affecting the human organism through upper limbs. Vibrations are also a very ample source of information on the technical condition, and hence they are commonly used in diagnostic systems. The human exposure to vibrations is depended on time, energy and dynamics of the transfer vibration. The compromise between comfort and safety of the vehicle driving is very difficult to achieve [3-4]. For the driving safety it is extremely important to provide constant contact of vehicle wheels to the road surface. It determines the high damping coefficient. For the comfort of the passengers it is important to minimize the vibration perception. It can be achieved by the gradual and smooth vibration absorbing. The driver J. Mikulski (Ed.): TST 2014, CCIS 471, pp. 120 129, 2014. Springer-Verlag Berlin Heidelberg 2014

Automatic Control Systems and Control of Vibrations in Vehicles Car 121 and passengers exposure to whole-body vibration of the vehicle can affect from shortterm body discomfort and inefficient performance to longterm physiological damage [5]. The vibrations of the vehicle body are main problem in ride comfort. The vibration exposure of the car depends on road roughness, speed, engine and powertrain parameters. To provide the best vibration isolation for the passengers the damping properties of the suspension have to be changeable to the drive condition. At the present the numerous automotive companies offer adaptive shock absorbers or active suspensions. It contains many of mechatronics systems and elements which are perfect to adjust the damping parameters of the suspension to the drive condition [2]. For the proper analysis of vibration or acoustics signals, as the result of wave propagation, it is important to consider material properties and technologies and to use correct methods of signal processing [5-13]. Humans are exposed to whole-body vibration in many means of transport, such as: passenger cars, buses, trains, trams, ships, even airplanes. The whole-body vibration caused a subject discomfort, fatigue and physical pains and it can affect on driving safety. There are many models of vehicle dynamics but it is much harder to find complex model of human-vehicle system. The reason is the fact that it is difficult to accurately estimate the behaviour of the human body under vibration, because it is a complex active dynamic system. The paper [14] presents the vibration model with prediction of the characteristics of the three reactions (physical, physiological and psychological), of the human exposed to a vertical sinusoidal wave force. It was assumed that the characteristics of the vibration of the human body are explained by the three reactions when the human body is exposed to some vibration environments: physical reaction expressed by the transmissibility of the vibrations of each part of the human body to a standard part, physiological reaction manifested in terms of blood pressure, heart rate, etc., psychological reaction as illustrated by manifestation of the different symptoms induced by vibration. The paper [14] presents basic structure for a synthetic vibration model of human beings. It was assumed that there are some linear relations between the physical, physiological and psychological reactions, so that a multiple regression analysis could be applied to analyse these relations. In the synthetic vibration model, the physical reaction can be simulated by equations of motion formalized by using Lagrange's equation, and the physiological and psychological reactions can be predicted by multiple regression equations defined through the multiple regression analysis (Fig. 1). In the multiple regression equations, the physical reaction directly relates to explanatory variables to predict the physiological and psychological reaction. Based on the synthetic vibration model it can be assumed that a two-dimensional model projected on the central plane, which is a midsagittal plane, of the human body would simulate the realistic vibration behaviour of the human body. The paper [14] presents two-dimensional vibration model consisting of masses, rigid links, springs and dampers with nine degrees of freedom. During the investigation described in [14] the human vibration model was installed on a concentrated frame of two-dimensional automobile vibration model [15] to simulate the vibration behaviour of a human body riding in an automobile (Fig. 2).

122 R. Burdzik, Ł. Konieczny, and B. Adamczyk Fig. 1. A synthetic vibration model for human beings [14] The paper [15] assumed prediction of unknown psychological and physiological reactions of a person riding the two-dimensional automobile vibrating at a given frequency, by using the multiple regression equation representing the relations between the psychological and physical reactions, and between the physiological and physical reactions. Fig. 2. A human vibration model riding in an automobile vibration model (right) [15]

Automatic Control Systems and Control of Vibrations in Vehicles Car 123 2 Research on Vehicle Vibration There are many publications about research on vibration in different kind of vehicles. The large possibilities of usage of vibration signals generate many conceptions and applications of systems based on vibration in cars. It is important to find proper vibration estimators due to destination of the system. It can be defined estimators based on amplitude, frequency or time-frequency representation of the vibration signal (Fig. 3). The previous publications presents applications of signal processing for determination of estimators of vehicle vibration signals [16-17]. Amplitude estimators Frequency estimators TFR estimators Fig. 3. Application of signal processing of vehicle vibration [own study] 3 Isolation of Vibration In order to meet growing requirements, contemporary automotive suspension systems are highly complex mechatronic units. There are semi-active, active and adaptive suspension systems being developed and improved on an ongoing basis. Unlike passive suspension, all the aforementioned types enable adapting the suspension parameters to individual road conditions and driving styles [18-22]. Suspension control systems adjust the characteristics of elastic and damping components to match preset criteria, such as comfort or sport driving, for instance. In the most highly advanced

124 R. Burdzik, Ł. Konieczny, and B. Adamczyk active systems, those equipped with actuators, the said solutions require considerable power input of even up to 20 kw. Fig. 4. Automotive suspension systems [22] Application of different suspension design solutions affects many significant parameters, one of which is the frequency of the sprung mass free vibrations. Fig. 5. Impact of the vehicle load variations on a change of the sprung mass free vibration frequency [23] With regard to a classic example of passive mechanical suspension system, the frequency declines as the load rises. When considering pneumatic suspension (gas springs of constant gas volume), the frequency also decreases as the load increases, but not as much as in the previous case discussed. As for hydropneumatic suspension

Automatic Control Systems and Control of Vibrations in Vehicles Car 125 systems (gas spring of constant gas mass), frequency of the sprung mass free vibrations rises as the vehicle load does so. In order to exemplify the solutions applied in controlled suspension systems installed in automotive vehicles, adaptive pneumatic and hydropneumatic suspension types have been discussed. 4 Pneumatic Suspension Systems On of such solutions is the pneumatic suspension which enables the static ground clearance value and its dynamic changes to be set independently (self-levelling depending on the suspension control algorithm). This solution has been applied in the following cars: Jaguar XJ featuring the Computer Active Technology Suspension (CATS), Volkswagen Phanteon featuring 4CL (4 Corner Luftfederung) and CDC (Continuous Damping Control) systems, Audi Allroad 4-Level. Pneumatic suspension systems include multiple components, the most important of which are actuating units comprising the pneumatic system, i.e. the pressure air tank along with its equipment, the engine and actuators being pneumatic columns. The suspension control system operates via a number of sensors, such as the front and rear axle height sensors, wheel and body acceleration sensors, steering wheel turning sensor etc. An element which monitors the suspension system operation is a high performance control unit. In adaptive pneumatic suspension systems, it is the principles of control that condition the way in which the suspension works (vehicle ground clearance setting). Values of adjustable ground clearance have been provided in the following table: Table 1. Ground clearance values in adaptive pneumatic suspension systems [24] Design solution Clearance Low [mm] Normal [mm] High 1 [mm] High 2 [mm] 4-Level -25 +25 +41 Audi Allroad 4 CL VW 0-15 +25 - Phaeton Jaguar XJ -15 - - The function of ground clearance adjustment while driving is often available in both the manual and the automatic mode. The control algorithm adjusts the ground clearance depending on the vehicle speed, and in each case, after a certain preset speed is exceeded the vehicle is automatically lowered. It causes the vehicle centre of gravity to move lower, thus improving its traction properties on higher speeds and reducing aerodynamic drag, which leads to reduced fuel consumption, at the same time. Fig. 6 illustrates sample principles according to which the pneumatic suspension is controlled in Audi Allroad.

126 R. Burdzik, Ł. Konieczny, and B. Adamczyk Fig. 6. Ground clearance control in Audi Allroad [24] Fig. 7. Ground clearance control in WV Phaeton [24] Fig. 8. Ground clearance control in Jaguar XJ [24]

Automatic Control Systems and Control of Vibrations in Vehicles Car 127 Operation of an adaptive suspension system requires appropriate pressure values to be applied in the pneumatic system. A sample collation of values of this parameter for the suspension systems discussed has been provided in Table 2. Design solution Table 2. Pressure and volume values applied in pneumatic suspension systems [24] 4-Level Audi Allroad 4 CL VW Phaeton Operating pressure [bar] Pneumatic system Residual Maximum pressure pressure [bar] [bar] Pressure vessel system Volume Operating [Litres] pressure [bar] No data 3,5 13,5 6,5 16 No data 3,5 20 5 16 Jaguar XJ 15 3 17,5 4,5 9-15 5 Hydropneumatic Suspension Systems Besides pneumatic suspension systems, there are also hydropneumatic systems where the functions of actuating units are performed by hydraulic cylinders. Unlike pneumatic suspension (based on springs of variable and controlled gas volume), the systems in question feature gas springs of constant gas mass. Table 3. Ground clearance values in adaptive and smart hydropneumatic suspension systems [24] Design solution Clearance Low [mm] Normal [mm] High [mm] Citroen C5 Hydroactive 3 Front -10 Rear -6 0 + 13 Citroen C6 Intelligent suspension: active suspension with electronically controlled springing and damping The suspension control unit has two operating modes: SkyHook and RoadHook. In specified conditions, this system can automatically lower the vehicle by around a dozen millimetres from 110 kph, thus optimising high-speed steering as well as fuel consumption. The solutions discussed are related to the adaptive properties (vehicle ground clearance changing) of an automotive suspension system. Such systems may additionally feature elements of controlled elasticity and damping characteristics, thus providing comprehensive smart suspension solutions (Citroen C6).

128 R. Burdzik, Ł. Konieczny, and B. Adamczyk 6 Conclusion The perception of vibration is extremely important for evaluation of exposure to whole-body vibration in means of transport. Taken into consideration the impact of vibration on driving safety it is very important to prevent driver and occupants from vibration. The constant evolution in vibroacoustics methods and measurements equipments allow to design new damping and isolating system for vehicles. The paper presents innovative solutions unconventional controlled suspension (pneumatic and hydropneumatic), increasing comfort and safety. Such solutions are often used in conjunction with damping control systems and allow you to adjust the suspension characteristics variables vibration excitation of the vehicle. The paper, with group of previous papers of the authors, discusses novel approach to isolation of vibration in motor vehicles. The developed methods of signal processing with innovative systems of vibration damping allow to elaborate new integrated system for vehicle vibration management. References 1. Maciejewski, M., Osmolski, W., Slaski, G.: Importance of Road Model in Simulation of Car Aerodynamics in a Wind-tunnel. In: Proceedings of 12th European Simulation Symposium, pp. 405 409 (2012) 2. Girtler, J., Ślęzak, M.: Four-state Stochastic Model of Changes in the Reliability States of a Motor Vehicle. Eksploatacja i Niezawodnosc Maintenance and Reliability 15(2), 156 160 (2013) 3. Slaski, G.: A Concept of an Integrated Suspension Control Logic Architecture and its Testin. In: Proceedings of 5th International Industrial Simulation Conference, pp. 201 205 (2007) 4. Jurecki, R., Stańczyk, T.: The Test Methods and the Reaction Time of Drivers. Eksploatacja i Niezawodnosc - Maintenance and Reliability (3), 84 91 (2011) 5. Nader, M.: The Influence of Mechanical Vibrations on the Driver s Body. Journal of Biomechanics 27(6), 716 (1994) 6. Dąbrowski, D., Batko, W., Cioch, W.: Model of the Gears Based on Multibody System and its Validation by Application of Non-contact Methods. Acta Physica Polonica A 123(6), 1016 1019 (2013) 7. Cioch, W., Knapik, O., Leskow, J.: Finding a frequency signature for a cyclostationary signal with applications to wheel bearing diagnostics. Mechanical Systems and Signal Processing 38(1), Special Issue: SI 55 64 (2013) 8. Kłaczyński, M., Wszołek, T.: Artificial Intelligence and Learning Systems Methods in Supporting Long-Term Acoustic Climate Monitoring. Acta Physica Polonica A 123(6), 1024 1028 (2013) 9. Kłaczyński, M., Wszołek, T.: Detection and Classification of Selected Noise Sources in Long-Term Acoustic Climate Monitoring. Acta Physica Polonica A 121(1-A), A-179 A- 182 (2012) 10. Dąbrowski, Z., Deuszkiewicz, P.: Nonlinear Dynamic Model of a Carbon-Epoxy Composite Structure. In: 20th International Congress On Sound & Vibration (2013) 11. Blacha, Ł., et al.: Application of the weakest link analysis to the area of fatigue design of steel welded joints. Engineering Failure Analysis 35 Special Issue: SI, 665 677 (2013)

Automatic Control Systems and Control of Vibrations in Vehicles Car 129 12. Lisiecki, A.: Welding of Titanium Alloy by Disk Laser. In: Proc. of SPIE. Laser Technology 2012: Applications of Lasers, vol. 8703, p. 87030T (2013) 13. Węgrzyn, T., et al.: Control Over the Steel Welding Structure Parameters by Micro-Jet Cooling. Archives of Metallurgy And Materials 57(3), 679 684 (2012) 14. Kubo, M., et al.: An investigation into a synthetic vibration model for humans: An investigation into a mechanical vibration human model constructed according to the relations between the physical, psychological and physiological reactions of humans exposed to vibration. International Journal of Industrial Ergonomics 27, 219 232 (2001) 15. Nishiyama, S.: Development of simulation system on vehicle±occupant dynamic interaction. Transactions of the Japan Society of Mechanical Engineers Seriese-C 59 568, 1004 1012 (1993) 16. Burdzik, R.: Implementation of multidimensional identification of signal characteristics in the analysis of vibration properties of an automotive vehicle s floor panel. Eksploatacja i Niezawodnosc Maintenance and Reliability Volume 16(3), 439 445 (2014) 17. Burdzik, R.: Identification of structure and directional distribution of vibration transferred to car-body from road roughness. Journal of Vibroengineering 16(1), 324 333 (2014) 18. Dixon, J.: The Shock Absorber Handbook, 2nd edn. Professional Engineering Publishing Ltd. (2007) 19. Balamurugan, L., Jancirani, J., Eltantawie, M.: Generalized Magnetorheological (MR) Damper Model and its Application in Semi-active Control of Vehicle Suspension System. International Journal of Automotive Technology 15(3), 419 427 (2014) 20. Snamina, J., Kowal, J., Orkisz, P.: Active Suspension Based on Low Dynamic Stiffness. Acta Physica Polonica A 123(6), 1118 1122 (2013) 21. Ho, C., Lang, Z.Q., Sapinski, B.: Vibration isolation using nonlinear damping implemented by a feedback-controlled MR damper. Smart Materials And Structures 22(10) Special Issue: SI, Article Number: 105010 (2013) 22. Seung-Bok, C., Yun-Hae, K., Prasad, Y.: Development of an Novel Adaptive Suspension System Based on Ball-Screw Mechanism. Applied Mechanics and Materials 477-478, 128 (2001) 23. Kowal, J.: Sterowanie drganiami. Gutenberg (1996) 24. Ł ęgiewicz, J.: Zawieszenia półaktywne, Auto Moto Serwis 1/2005, 29 32 (2005) 25. Karoń, G., Mikulski, J.: Transportation Systems Modelling as Planning, Organisation and Management for Solutions Created with ITS. In: Mikulski, J. (ed.) TST 2011. CCIS, vol. 239, pp. 277 290. Springer, Heidelberg (2011) 26. Mikulski, J.: Introduction of telematics for transport. In: Proceedings on 9th International Conference ELEKTRO 2012, Rajecke Teplice, IEEE Catalog Number CFP1248S-ART, May 21-22, pp. 336 340 (2012), http://ieexplore.ieee.org