Automobilio svyravimai ekstremalaus stabdymo metu ; Oscillations of the vehicle in emergency braking
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Robertas PE ČELI ŪNAS OSCILLATIONS OF THE VEHICLE IN EMERGENCY BRAKING Summary of Doctoral Dissertation Technological Sciences, Transport Engineering (03T) 1081 Vilnius „Technika“ 2004 VILNIUS GEDIMINAS TECHNICAL UNIVERSITY Robertas PE ČELI ŪNAS OSCILLATIONS OF THE VEHICLE IN EMERGENCY BRAKING Summary of Doctoral Dissertation Technological Sciences, Transport Engineering (03T) Vilnius „Technika“ 2004 Doctoral dissertation was prepared at Vilnius Gediminas Technical University in 2000 – 2004 Scientific Supervisor Prof Dr Habil Ona Lukoševi čien ė (Vilnius Gediminas Technical University, Technological Sciences, Transport Engineering – 03T) The Dissertation is to be defended at the Council of Scientific Field of Transport Engineering at Vilnius Gediminas Technical University: Chairman Prof Dr Habil Leonas Povilas Lingaitis (Vilnius Gediminas Technical University, Technological Sciences, Transport Engineering – 03T) Members: Prof Dr Habil Adolfas Baublys (Vilnius Gediminas Technical University, Technological Sciences, Transport Engineering – 03T) Prof Dr Habil Bronislovas Spruogis (Vilnius Gediminas Technical University, Technological Sciences, Transport Engineering – 03T) Prof Dr Habil Jonas Sapragonas (Kaunas Technological University, Technological Sciences, Transport Engineering – 03T) Prof Dr Habil Algirdas Jurkauskas (Kaunas Technological
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| Publié par | vilnius_gediminas_technical_university |
| Publié le | 01 janvier 2005 |
| Nombre de lectures | 33 |
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Robertas PEČELINAS OSCILLATIONS OF THE VEHICLE IN EMERGENCY BRAKING Summary of Doctoral Dissertation Technological Sciences, Transport Engineering (03T) 1081
Vilnius Technika 2004
VILNIUS GEDIMINAS TECHNICAL UNIVERSITY Robertas PEČELINAS OSCILLATIONS OF THE VEHICLE IN EMERGENCY BRAKING Summary of Doctoral Dissertation Technological Sciences, Transport Engineering (03T) Vilnius Technika 2004
Doctoral dissertation was prepared at Vilnius Gediminas Technical University in 2000 2004 Scientific Supervisor Prof Dr Habil Ona Lukoevičien Gediminas Technical (Vilnius University, Technological Sciences, Transport Engineering 03T) The Dissertation is to be defended at the Council of Scientific Field of Transport Engineering at Vilnius Gediminas Technical University: Chairman Prof Dr Habil Leonas Povilas Lingaitis (Vilnius Gediminas Technical University, Technological Sciences, Transport Engineering 03T)Members: Prof Dr Habil Adolfas Baublys Gediminas Technical (Vilnius University, Technological Sciences, Transport Engineering 03T)Prof Dr Habil Bronislovas Spruogis (Vilnius Gediminas Technical University, Technological Sciences, Transport Engineering 03T) Prof Dr Habil Jonas Sapragonas (Kaunas Technological University, Technological Sciences, Transport Engineering 03T) Prof Dr Habil Algirdas Jurkauskas Technological University, (Kaunas Technological Sciences, Transport Engineering 03T) Opponents: Prof Dr Habil Sergejus Lebedevas(Klaipda University, Technological Sciences, Transport Engineering 03T) Dr Gediminas Vaičinas(Vilnius Gediminas Technical University, Technological Sciences, Transport Engineering 03T) The dissertation will be defended at the public meeting of the Council of Scientific Field of Transport Engineering in the Senate Hall of Vilnius Gediminas Technical University at 2 p. m. on January 27, 2005. Address: Saultekio al. 11, LT-10223 Vilnius-40, Lithuania Tel. +370 5 274 49 52, +370 5 274 49 56, fax +370 5 270 01 12, e-mail doktor@adm.vtu.lt The summary of the doctoral dissertation wasdistributed on December 27, 2004 A copy of the doctoral dissertation is available for review at the Library of Vilnius Gediminas Technical University (Saultekio al. 14, Vilnius, Lithuania) © Robertas Pečelinas, 2004
VILNIAUS GEDIMINO TECHNIKOS UNIVERSITETAS Robertas PEČELINAS AUTOMOBILIO SVYRAVIMAI EKSTREMALAUS STABDYMO METU Daktaro disertacijos santrauka Technologijos mokslai, transporto ininerija (03T) Vilnius Technika 2004
Disertacijarengta20002004metaisVilniausGediminotechnikos universitete. Mokslinvadovprof. habil. dr. Ona Lukoevičien (Vilniaus Gedimino technikos universitetas, technologijos mokslai, transporto ininerija 03T). Disertacija ginama Vilniaus Gedimino technikos universiteto Transporto ininerijos mokslo krypties taryboje: Pirmininkas prof. habil. dr. Leonas Povilas Lingaitis Gedimino technikos (Vilniaus universitetas, technologijos mokslai, transporto ininerija 03T). Nariai: prof. habil. dr. Adolfas Baublys (Vilniaus Gedimino technikos universitetas, technologijos mokslai, transporto ininerija 03T), prof. habil. dr. Bronislovas Spruogis (Vilniaus Gedimino technikos universitetas, technologijos mokslai, transporto ininerija 03T), prof. habil. dr. Jonas Sapragonas (Kauno technologijos universitetas, technologijos mokslai, transporto ininerija 03T), prof. habil. dr. Algirdas Jurkauskas(Kauno technologijos universitetas, technologijos mokslai, transporto ininerija 03T). Oponentai: prof. habil. dr. Sergejus Lebedevas (Klaipdos universitetas, technologijos mokslai, transporto ininerija 03T), dr. Gediminas Vaičinas(Vilniaus Gedimino technikos universitetas, technologijos mokslai, transporto ininerija 03T). Disertacija bus ginama vieame Transporto ininerijos mokslo krypties tarybos posdyje 2005 m. sausio 27 d. 14 val. Vilniaus Gedimino technikos universiteto senato posdisalje Adresas: Saultekio al. 11, LT-10223 Vilnius-40, Lietuva Tel. +370 5 274 49 52, +370 5 274 49 56, faksas +370 5 270 01 12, el. p. doktor@adm.vtu.lt Disertacijos santrauka isiuntinta 2004 m. gruodio 27 d. Disertaciją peri galimarti Vilniaus Gedimino technikos universiteto bibliotekoje (Saultekio al. 14, Vilnius, Lietuva) VGTU leidyklos Technika 1081 mokslo literatros knyga © Robertas Pečelinas, 2004
GENERAL CHARACTERISTIC OF THE DISSERTATION Aim of the work to define the consistent patterns of impacts exercised by oscillation of the vehicle in emergency braking on the vehicle movement mode and on the braking distance; to analyse theoretical and experimental processes of oscillation formation; to elaborate the reliances of these processes related to the alternations in the acceleration of deceleration (delay) of the vehicle. To extend, with the aid of the developed models, the expert opportunities for modelling the vehicle movement, for investigation of accidents circumstances related to vehicle braking. Methodology of research the development of mathematical includes algorithms and theoretical calculus for analysed processes, as well as the presentation of the influence of various factors on vehicle oscillations during the braking. Analytical methods and those in figures have been applied for the research. Experimental investigations were carried out by applying the electronic VZM 100 device, measuring the acceleration of deceleration, adapted for a synchronous operation together with vibration processing system VAS-21. For computer modelling there have been used novel programmes created by the author in the systemMicrosoft Developer Studio Microsoft Fortran Power Station. Scientific novelty • A mathematical model of the vehicle in emergency braking on an ideally smooth and on a real practical road has been structured and calculated, by integrating the equivalent oscillating systems of the theory of uniformmovement and braking dynamics. • A mathematical model of impact exercised by bampers characteristics on the vehicle braking process has been designed, enabling the determination of coefficients of longitudinal relative forces of the vehicles front and rear axles, which depend on the road surface pavement and its condition. • Processes of oscillation of flexible mounted and inflexible mounted masses have been analysed, given the tangential effect of the wheel contact with bearing surface, thus enabling the more precise calculus of vehicle braking parameters. Practical value. The obtained research results extend the vehicle oscillation theory in the transitional movement modes, which are used in the design and improvement of vehicle suspensions, as well as in traffic accidents investigation and perfection of methodology of their expertise calculations.
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Defended propositions • of equivalent oscillating system of the vehicle inThe mathematical model emergency braking. • The mathematical model of dampers efficiency subject to the impact of output on the vehicle braking. vehicle movement mode determination based onThe methodology of the • the evaluation of suspension deformations. The scope of the scientific work. The scientific work consists of the general characteristic of the dissertation, 6 chapters, conclusions, list of literature, list of publications and addenda. The total scope of the dissertation 149 pages, 93 pictures, 13 tables and 3 addenda. Approval of the work 1. International conferenceCA-0ALTI1BSNART, Vilnius, VGTU. 2. Republican conference-2002ARTOPSNSATR, Vilnius, VGTU. 3. International conference0-3CATIALSBANTR, Vilnius, VGTU. 4. The fourth conference of young scientists of LithuaniaLietuva be mokslo Lietuva be ateities ( LithuaniaLithuania without science without future),Vilnius, VGTU. 5. fifth conference of young scientists of LithuaniaThe Lietuva be mokslo Lietuva be ateities(Lithuania without science Lithuania without future),Vilnius, VGTU. 6. The sixth conference of young scientists of LithuaniaLietuva be mokslo Lietuva be ateities(Lithuania without science Lithuania without future),Vilnius, VGTU. 7. International conferenceTransporto priemons-2001 (Transport Means-2001), Kaunas, KTU. 8. International conferenceTransport Means-2003, Kaunas, KTU. 9. Scientific conference of postgraduates, graduates and studentsФизикаконденсированногосостояния (ФКС-XII)(Physics of condensation state), Grodno, 2004. 10. XI International scientific-technical conference on transport engineering and technologiestrans & MOTAUTO04, Plovdiv, 2004. 11. International conferenceReliability and Statistics in Transportation and Communication (RelStat04), Riga, 2004. 12. International scientific conferenceETHCUIN40, Gabrovo, 2004.
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1. METHODS OF MODELLING OF VEHICLE OSCILLATIONS The suspension of the motor vehicle is one of the most important elements of the flexible mounted and inflexible mounted masses of the vehicle bodywork, and most attention is paid to its exploration and improvement. Analysis of models of equivalent oscillation systems of motor vehicles testifies that the evaluation of motor vehicle oscillations and modelling of its motion modes is still very topical and requires further research. Suspension models of motor vehicles offered in publications regard only the influence of road irregularities, and the modernisation of these models is directed towards the improvement of passengers comfort. However not much research has been done on the influence of oscillations of flexible mounted and inflexible mounted masses of the bodyworks of vehicles in the process of braking; also there is not much investigation of the post-accident identification of the vehicles movement mode corresponding to the deformations of the suspension and the longitudinal pitch of the bodywork. Research of oscillations in the conditions of emergency braking is primarily important for the work in two practical directions: • improvement of calculation methods of motor vehicles response to external impact in the conditions of real operation; • further improvement of research methods on the road, and analysis of fait accompli road accidents related to oscillations in the emergency braking. Methodology defining the oscillations occurring in the braking may be applied in the designing and improvement of suspensions and other mechanisms, as well as in the analysis of road accidents for definition of motor vehicles motion mode according to the bodyworks pitch angle. Therefore it is purposeful to analyse the oscillations of the motor vehicle in braking together with the evaluation of the impact of systems involved during the interacting of the vehicle and the road. In summary, the following objectives and tasks may be formulated:• To make a mathematical model of oscillations of the vehicle in emergency braking under the circumstances of even and uneven road. To store in the theory of such model the functional schemes of damping, which are used in the theory of uniform translation and vehicle suspension. • applying of mathematical model, to specify the solution methodsBy visibly demonstrating and comparing the particularities, and identifying the differences of vehicle oscillations in the process of braking and in the mode of uniform translation. While developing the mathematical models solution methods, using the advanced means of calculation techniques, to foresee for the case of braking not only the opportunity of qualitative analysis of diversity of
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oscillation processes in this mode, but also the possibility of calculation of quantitative characteristics of the reaction towards the braking. • create an engineering method for calculation of oscillationsTo occurring during the vehicle braking. By selecting for the engineering calculations the simplifications, to maintain the equivalent vehicles oscillating systems details at the same level as found in the theory and practice of the vehicle translation and suspension calculus, as well as the calculus of the dynamics of braking found in the theory of the vehicle. • Taking into account the complexity of vehicle suspension, to investigate the dependence of basic deformations (pitch, lean) of the vehicle suspension on the motion mode, the speed and the acceleration, as well as on the workload (lateral lean). In the course of this investigation it is necessary to maintain the set practice of evaluation of parameters of suspensions subject to various impacts either in static conditions or in dynamics. • In line with these requirements to construct reasonably and apply new special equipment for experimental vehicle research related to oscillations of the vehicles flexible mounted and inflexible mounted masses under the maximum acceleration of deceleration. In the process of developing the new experimental equipment it is necessary to foresee not only the methods of its application, but also the utmost precision methods for evaluation of the oscillating systems formed in the created constructions. • To perform experimental research of vehicle oscillations, in natural conditions of braking, thus aiming at the comparison of actually observed processes with the results of theoretical investigation of the mathematical model. To evaluate the influence of the vehicle oscillations found in braking on the indices of braking process and its effectiveness. • of the results of theoretical andTo develop practical applications experimental research, regarding the novelty of setting the task, as well as the newness of experimental equipment for testing of vehicle motion. 2. VEHICLE SUSPENSIONS, THEIR INFLUENCE ON THE OSCILLATIONS OF THE FLEXIBLE MOUNTED AND INFLEXIBLE MOUNTED MASSES Most attention in vehicle design is focused on the comfort of persons inside the vehicle. The main function of the suspension is to secure elastic support of the vehicle thus enabling the comfortable drive for passengers, isolating them from unevenness of the road surface. Another no less important requirement for the suspension system is the necessity to stabilise the moving vehicle during the turning, braking or acceleration. In practice, regarding these
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two main requirements for vehicle movement and management, a disagreement between the soft and hard springing of the suspension occurs. Therefore it can be maintained that a successfully designed suspension system is the system in which these requirements are harmonised.
100% resistance to braking pitch
h
L
ξL
100% resistance to braking pitch
Fig. 1Illustration of conditions reacting against the braking pitch To get a 100% reaction against the dip of the front and the rise of the rear part of the vehicle, the fulcrum of the suspensions trailing arm should be in the geometrical position of the points determined by the following relations: For the front gear: eh dff=tgβf= − ξL. (1)
(2)
For the rear gear: e h . drr=tgβr(=−1)−ξL Figure 1 shows such conditions. If the fulcrums are set below the mentioned geometrical position of the points, then a lower than 100 % reaction against the braking pitch will be obtained; if the points are set above such a line, then during the braking the front will rise and the rear will sink. In practice a 100 % reaction against the braking pitch is very rare. The maximum reacting against the braking pitch seldom exceeds 50 %. Some reasons for this are given below: 1. Total reaction against the braking pitch requires that the fulcrum should be set above the point necessary for obtaining complete anti-squat reaction during the acceleration. Thus, in the case of stiff axles, the rise will occur caused by acceleration.
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2. In the case of total reacting against the braking pitch, the changes of front suspension caster angle may significantly increase the driving forces during the braking. 3. The proper geometry of driving system may be very complex. 4. Due to the vibration of wheels the excessive changes of speed may occur in the gears, thus causing noise in the gears. 5. Due to the highly set fulcrum the problems of excess subordination may arise in the rear suspension. 6. In case of too short trailing arm of suspension the oscillations may occur during the braking. Tendency for such oscillations decreases with the increase of this arms length in the suspension structure. Vehicle suspensions of different types have been analysed, as well as their impact on the oscillations of the flexible mounted and inflexible mounted masses of the vehicle. During the analysis of suspensions their characteristics have been specified/corrected, also there have been defined suspensions transverse and longitudinal pitch centres, the position of which determines the pitch of vehicle body under the impact of various forces. Also there was evaluated the influence of the geometrical construction of the suspension on the oscillations of the vehicle by changing the modes of movement (braking, acceleration, turning). 3. THE PROCESS OF VEHICLE BRAKING Deceleration during the braking and acceleration during the speed gathering determine an average speed of the vehicle. It is important that during the braking the stopping/braking distance should be possibly shorter (increased deceleration/slowing down), so that the vehicle should be manageable and should not get off-balance. The braking force within the contact of the wheel and the road: BS=MS. (3)
To avoid the slide of the wheel in braking, the following condition should be observed: ⋅ BSGS. (4)
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