Yolda giden taşıta etkileyen kuvvetlerin devrilme esnasında incelenmesi
Başlık çevirisi mevcut değil.
- Tez No: 55550
- Danışmanlar: PROF.DR. A. IŞIK ERZİ
- Tez Türü: Yüksek Lisans
- Konular: Makine Mühendisliği, Mechanical Engineering
- Anahtar Kelimeler: Motorlu taşıtlar, Vektörler, Yanal yükler, Motor vehicles, Vectors, Lateral loads
- Yıl: 1996
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: Belirtilmemiş.
Özet
ÖZET Motorlu araçlarda aktif emniyet tedbirleri çerçevesinde aracm stabilitesi ve yörünge takibi önemli bir yer tutar. Bunlara ilişkili olarak viraj esnasında etkiyen yanal kuvvetlerin, taşıt ekseninin açısal hızına ve hız vektörünün dönme hızına göre değişimi yana yatma dikkate alınarak yalpa ekseni konumu, yörünge takibi ve stabilite arasında matematiksel modeller oluşturulmuş ve bilgisayar kullanarak hesaplamalar yapılmıştır. IX
Özet (Çeviri)
SUMMARY AN ANALYTICAL MODEL FOR THE ROLLOVER LINEAR AND NONLINEAR It is taken an important situation in order to provide the stability of vehicle and the issuance of rotoue. In addition to the lateral forces on the cornering In addition to the activated safety preventions in the engined vehicles, in addition to the angular velocity change of vehicle and the velocity vector change to the rotational speed. It is taken place the mathematical models. The heading axis between the rotoue issuance and the stability and it is calculated with this computer. It is used linear and nonlinear kinematic constrains in this model. A control law for integrating 4WS and 4WS systems is presented. It is based on a non-linear vehicle model in which the lateral force acting on the tyres changes according to the sleep angle, slip ratio and the load. These maneuvers include cornering with breaking or acceleration as well as vehicle skidding, spinning and rollingover. The generalized velocities used in this model are lateral velocity, V and yaw rate v|/ in this model. It is assumed that the sprung mass center and total vehicle mass center are in the same transverse section of the vehicle. In this study, it is taken a vehicle model as example A vehicle model (h * 0). When the vehicle passes on the contact velocity. The simulation uses a nonlinear eight degree of freedom model which utilizes simple linear subsystems to model the tyres. The vehicle model consists of two masses; a spring mass represent the vehicle chassis and a single unsprung mass which represents the combined front and rear systems. The rollover model simulates the motion of a vehicle which skids laterally onto a pavement and comes into with a road side curb with some small heading angle. The model simulates the skidding motion of the vehicle after impact vehicle rollover is assumed to take place when the roll angle of the unsprung mass exceeds approximately 85°. The simulation uses a nonlinear model which utilizes simple linear subsystems to model and the impact force on the vehicle tyres. The vehicle model consists of two masses; a sprung masses have seperate degree of freedom for roll, lateral translation Xand vertical translation, vehicle yaw and pitch being analyzed using a single lumped mass. Design of vehicle linear simulation model. The tyre normal reactions (FzJ, F^, F^, Fz4) are based on a linear tyre deformation model and are proportional to tyre deflections caused by vehicle heave, pitch and roll. The tyre deflections are determined by finding the difference between the undeflected tyre and the distance between the axle and the road surface under each wheel. The tyre lateral sliding forces (Si, S2, S3, S4) are functions of the tyre normal forces, the tyre - surface factional properties and the sliding velocity. The equations of motion for a, e, \\/' and \\i lateral position ( for each mass) were obtained mass and the Newton's second law of motion to the sprung mass and the unsprung mass include gravity and the two forces of the suspension springs and dampers. The sprung mass roll moment equation is; (mhl2 +Ix)i|/ = h'mV(a-+\|/-)+mgh'i|/ -[Ci|/0+C\j/A)i|/-(k\|/0+k\|/A)\|/- (1) The equations of sprung mass lateral and vertical motions are, S,+S2+S3+S4-kNV2a=m[v(a + \(;)-h'v|/] (2).ö Sö - Mrö - <LA Sa + Mra ) - kM v2 a = lz s" (3) Modification to model. In order to perform a sensivity analysis on the rollover model, it was necessary to translate the Basic program into a nonlinear program. During this process, an inaccuracy was discovered in an assumption made by the model. Several small angle assumptions made by the model were affecting the impact velocity. For instance, the distance that the vehicle skids before impact. It is always measured perpendicular to the curb, which is a shorter distance in cases with a yaw angle. Although the model was reasonably at accurate small heading angles, it was deemed necessary to add a nonlinear system to add a nonlinear system to the model. For the purposes of sensivity analysis, the nonlinear model simulation was rearranged so that the absolute position of the vehicle relative to the curb was measured from the front right tyre. This was done to ensure that the time of impact would be independent of the track width of the vehicle. If the absolute position of the XIvehicle was measured from the position of the centre of gravity of the vehicle (as it was the original simulation) then the distance travelled by one with a wide track width would affect the accuracy of the model. Consequently, the two vehicles would hit the curb at slightly different times, skewing the sensivity results. The model was extensively verified by comparing the vehicle's response and energy exchange using several sets of initial conditions. The model was validated using reference system, which includes the inaccucaries mentioned above. However, the change in the reference system should not affect the response of the system when the heading angle was zero. Significant improvements in the active safety of light vehicles have been achieved in the recent past. These include advancements in the design, analysis and testing of the suspension systems and 4WS control options. This technology has been the subject of intense research, and today, many vehicles are available with active four wheel steering (A-4WS). Many sorts of equipment such as ASTM skid trailers (for breaking friction) or SCRIM (for sideway friction) have been widely accepted as standarts for measuring skid on a road surface where as the breaking ability of a vehicle (such as its cornering speed). From previous information it is known that below the optimum value of SFC, S (or a), is controlled primarily by the elastic tyre properties. The effects of road friction begin to appear at and above the optimum value of Sx (or a), it is assumed that the elastic tyre properties can be represented by the tyre stiffness (longitudinal, lateral), whereas the road friction can be represented by any value of the coefficients of breaking (or cornering), from optimum to maximum value of Sx ( or a). The choice of locked - wheel maximum SFC as input parameters on this model is primarily based on two reasons. Maximum SFC from surface texture measurements already exist. The ultimate goal to develop a theoratical tecnique data, can be maintaned. Secondly, maximum SFC is commonly available; hence the data from such equipment can be processed directly to obtain the friction at all ranges of Sx and a. Figure 1. shows the simplified diagrm for calculation or prediction of the frictional forces. The ability to calculate the tyre - road friction under all conditions ( braking, cornering and combinations of slips) from tyre stiffness and one of the friction coefficients is a feature of this model. This model requires one friction parameter less than that required by the semi-emprical model. More importantly, since XIIthe locked-wheel maximum SFC can be predicted from surface texture measurement, this model then can be used to predict the tyre - road friction under all conditions, from tyre stiffness and surface texture data, the wheel pressure, over the contact patch produces the normal force, and its avaarge value over the contact patch width is approximated by a trapezium, contact length of 21, and slope length of a and b. This model provides users with one additional option of an unsymetric trapezoidal distribution. Figure I: Simplified Diagram For Calculation Of Frictional Forces. A Basic computer program (see Appendix A) has been written for routine calculation of frictional forces. The computing time for obtaining acr has been minimized without losing accuracy of the result. This can be done by providing two loops for achieving the convergence. The first loop with large increments is intended to quickly bring the position into the region of convergence The second loop then allows smooth increments to be executed within this region, as a result, about 20 seconds is required to run the program£5] CONCLUSIONS AND REMARKS: In this study, vehicle dynamics simulation, presented is a result of the latest research in the vehicle dynamics and stability, and tire - roadway interaction. Through a proper combined maneuver, cornering with braking or acceleration, as well as vehicle skidding, spinning or rolling over can be simulated. The rigid vehicle model suggests that the lateral acceleration necessary to reach the rollover of passenger cars and light trucks exceeds the cornering capabities. A rising from the friction limits of the tyres. That is being the case, it is possible for the car to spinout on a flat surface without rolling over. XIIIThe model is a fully interactive and menu driven simulation, which along with a wide diversity of applications, allows the users to invastigate the influences of vehicle or subsystem design characteristic on performance, handling, stability and rollover behaviour. This model utilizes a three dimensional, nonlinear vehicle model of intermediate detail which requires a modest amount of vehicle data and specifies the type of suspensions and enters additional data such as inertia, geometry, stiffness, damping, drive type, brake distribution, type of steering control system, aerodynamics and tyre-roadway characteristics. This data file is automatically stored for subsequent simulation runs. This aim in this study, the axle construction and in relation to this, the yaw axis's effective is shown on the vehicle driven specifications, the simulation is particularly suited for those professionals involved designing, researching and teaching vehicle dynamic systems, vehicle active safety and tyre mechanics. The following are some applications of the simulation. * Investigation of performance, handling and stability of light vehicles * Investigation of effects of roll center and roll axis positions. * Analysis of tyre forces generated in severe'- vehicle maneuvers. * Investigation of dynamic response and stability of 4 WS vehicles (proportional, rear advance and front advance 4 WS) * Investigation of vehicle maneuvers that produce skidding, spinout and rollover. XIV
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