Thesis content Starting from the purpose, object, scope and method of the research, in addition to the introduction, the layout of the thesis includes the following chapters: Chapter 1:
Trang 1MINISTRY OF EDUCATION AND TRAINING
UNIVERSITY OF TRANSPORT AND COMMUNICATIONS
DINH QUANG VU
RESEARCH ON THE EFFECTS OF TIRE PRESSURE ON THE HANDLING OF PASSENGER CARS MANUFACTURED
AND ASSEMBLED IN VIET NAM
Major: Mechanical dynamic engineering Code No: 9520116
SUMMARY OF THESIS FOR DOCTOR OF ENGINEERING
HA NOI - 2021
Trang 2This thesis is completed at:
University Of Transport And Communications
Scientific Advisers: Dr Dang Viet Ha
Associate Prof Dr Cao Trong Hien
Trang 3INTRODUCTION
The urgency of the research
Since its inception until now, the auto industry has gone through many stages of development along with the development of science and technology With the growth of the speed and density of the car's movement, it is required that the car ensure a high degree of guidance Therefore, in order to minimize the occurrence of traffic accidents, it is necessary to study more deeply about the guidance of domestically assembled cars in the current period
Objectives of the research
The research on the influence of elastic wheel roll on the guideability of passenger cars manufactured and assembled in Vietnam
Proposing measures to improve the guidance of cars
Subjects, scope of the research
The object of the thesis is a passenger car manufactured and assembled in Vietnam
The research scope of the thesis is the elastic wheel deflection
to the car's guideability
Research Methods
The research method of the thesis is a combination of theoretical research and theory testing evaluation through experiment
Theoretically:
- Build mathematical models and solve for survey
- Use software to calculate and simulate
Experimentally measure the rotational dynamics parameters such as: horizontal acceleration, angular velocity of the vehicle body, rotational trajectory to compare and evaluate the theoretical model Thereby verifying the built dynamics model Experiment with highly reliable instruments and advanced measurement methods, based on current international standards
New results and scientific and practical significance of the thesis
The new results of the thesis:
- Built a spatial model of car rotation to investigate the influence of pressure and wheel rolling, on the acceleration of the
Trang 4vehicle's transverse body speed, body rotation speed, and rotational trajectory car
- Experiment to determine the rotational dynamics parameters such as: horizontal acceleration; body rotation speed; orbital rotation
to compare, evaluate model theory
- Measure the experiment with special bias on the database Experimental jigs can be used to do experiments for different types
- Research Pacejka model for 8 the information have a feature
to pressure
Scientific significance:
The research results of the thesis help to improve the
theoretical and experimental basis in the field of motion dynamics research in general and the rotation in particular of automobiles The influence of tire pressure has been studied on the guideability of passenger cars manufactured and assembled in Vietnam Determine experimentally the rolling deviation characteristics of tires on
specialized equipment
Practical significance:
The research results of the thesis can be used in practical testing of motor vehicles As a basis for proposing solutions to ensure road traffic safety As a reference for teaching, researching and developing specialized legal documents
Thesis content
Starting from the purpose, object, scope and method of the research, in addition to the introduction, the layout of the thesis includes the following chapters:
Chapter 1: Overview of the research issues
Chapter 2: Building a dynamic model to study the handling of passenger cars
Chapter 3: Surveying the navigability of passenger cars Chapter 4: Experimental Research
CHAPTER 1: OVERVIEW OF RESEARCH ISSUES Basic concepts of car handling
Handling [26][27] As one of the important properties of the
car, under the control effect, the car has the function of changing and stabilizing the direction of motion, thus playing a decisive role in the safety of the car's movement It determines the car's ability to safely move at high speeds and especially on roads with heavy traffic
Trang 5Cars participating in traffic all use elastic wheels, the advantage of this elastic wheel is to create good grip on the road, light, and less damaging to the road surface structure [41] However, one of the disadvantages of an elastic wheel is that it produces a misaligned side slip angle [41][42] During the movement, it causes trajectory deviation during the movement of the vehicle, which greatly affects the safety of the vehicle's movement
Concept of rolling and deflection of elastic wheel
The movement of cars on the road depends very much on the relationship of the wheels to the road surface When the car is moving, there is a side slip angle of the wheel [30][25]:
Py: horizontal force; γ: Wheel chamber angle;
δγ: side slip angle deviation caused by wheel chamber angle;
Kγ is called the coefficient of rolling resistance caused by the wheel chamber angle
The concept of car rotation
Calculation of the change of deflection parameters due to lateral deformation of the tire compared with the rigid tire under the effect of horizontal force is called the rotation of the car [26][44] Depending on the value and relationship between δ1 and δ2 which cars can have different rotation: excess rotation δ1 < δ2, low δ1 > δ2, neutral δ1 = δ2 [14] In case the tire is not deformed, the side slip angle of the wheels is zero, in the case of a deformed tire, the side slip angle of the wheels is non-zero Cars with excess rotation are not stable when in motion and the safety is smaller than cars with low rotation and neutral rotation When designing the vehicle, attention should be paid to avoid excess rotation
Handling assessment factors
- Investigate the influence of tire pressure on the difference in side slip angle before and after;
-Investigate the effect of tire pressure on horizontal acceleration;
- Investigate the effect of tire pressure on body rotation speed;
- Investigate the effect of tire pressure on motion trajectory
Trang 6Dynamic model to study the handling of cars
A number of model directions have been developed to investigate the car's navigation, such as Single Mass Plane Model, Single Mass Spatial Model, 3 Mass Spatial Model [23][24] handling research:
Fig 1 1 Diagram of 3 Mass Spatial Model of handling research
In the content of the thesis, attention will be paid to 16 degrees
of freedom: The axial motion in the horizontal, vertical and vertical directions of the suspended mass and the rotation around these axes The front and rear axles have vertical and horizontal movement and rotation around the longitudinal axis (vertical shake)
Research on the handling of cars at home and abroad
Nghiên cứu trong nước
In 2015, the author group Dao Manh Hung studied the influence of the side slip resistance coefficient of the tire on the motion trajectory of the car [10] However, the model the author uses
is a flat 1-mass model Therefore, the accuracy of the research model
is not high
In 2016, author Nguyen Ngoc Tu [17] built an integrated model that combines description of braking, accelerator pedaling and steering wheel rotation to investigate some dynamic instability processes of trailers The author investigates the stability of the trailer by the method of separating the structure of the multi-body system and solving this model to determine the law and limit of instability of the trailer, helping the driver to have a control base Steady and safe driving of trailers In 2017, the author Ta Tuan Hung [11] built a dynamic model of the semi-trailer and investigated the influence of parameters such as height of center of gravity, angle of rotation of the guide wheel and vehicle handling speed when turning
to lateral flip instability the semi-trailer In 2018, the author Nguyen Tien Dung [5] built a dynamic model of the semi-trailer to study the stability of the movement trajectory of the semi-trailer when
Trang 7changing lanes due to the influence of steering angle, vehicle speed From there, the limit of lane deviation when changing lanes is introduced In 2017, author Vo Quoc Dai [50] studied a spatial model with 4 degrees of freedom: vertical, horizontal, rotation around the z-axis and horizontal shaking The author studies the influence of longitudinal shaking and vertical displacement and determines the influence of the angle of placement, tilt angle of the vertical cylinder on the camber angle The author also evaluates the guiding characteristics when changing the tilt angle of the vertical column (caster) However, the above authors have not evaluated the influence of tire pressure, as well as elastic wheel deflection on the vehicle's guidance, which directly affects the trajectory
Research abroad
In 2013, the author group Krzysztof Parczewski et al[33] studied the influence of tire pressure on automobile dynamics, specifically on the braking process of automobiles The author does not analyze the influence of tire pressure on the vehicle's lateral dynamics: wheel deflection angle, lateral acceleration, vehicle trajectory In 2013, the group of authors Shaopu Yang, Yongjie, Shaohua Li [40] did a fairly general study of the guideability research model from the planar model to the spatial model However, the author has not delved into the study of specific models nor evaluated the influence of different input parameters on the guiding factors
Author A.C ЛИТВИНОВ [23] studied the 1-mass spatial model to study the handling of cars
Author Nenad Lazic has studied the influence of the side deflection angle on the motion trajectory using a car model with four guide wheels [24]
Regarding the 3-mass spatial model of handling studies, In
1999, the authors S Hegazy, H Rahneejat and K Hussain [52] proposed a model study with separation into a multi-body system with 34 objects and 94 degrees of freedom In 2008, the group of authors Jaehoon Lee, Jonghyun, Seung Jin [53] studied the 16 degrees of freedom model for rotation and lane change to evaluate this model with experiment as well as with carsim simulation software The error of the model compared to the experiment is at most 15% when turning around, this error is still large
Trang 8After analyzing domestic and foreign studies, it can be seen that the authors have built spatial models for different studies on stability and directionality However, the influence of tire pressure has not been studied on the rolling deviation of the wheel, on the horizontal acceleration of the body, on the body rotation speed, on the rotational trajectory of the car
CHAPTER 2: BUILDING A DYNAMIC MODEL FOR RESEARCH INSTRUCTIONALITY OF PASSENGER CARS 2.1 Structural analysis and modeling assumptions
2.1.1 Choose a vehicle as a research object
The localization rate of passenger cars in Vietnam has reached 45% [21] including pneumatic tire components, a problem for researches to ensure the safety of movement of cars fitted with these components is very important In addition, the number of passenger cars carrying people from 26 to 46 seats accounts for a large proportion of 33% of the total number of passenger cars carrying people over 10 seats [3] Therefore, the topic of choosing a Hyundai COUNTY HM K29SL passenger car assembled by Tracomeco Factory is the object of research
2.1.2 Analyze the object's structure
Passenger cars [2] were selected as the research object with the following structural features: passive front-wheel drive; suspension front, rear tweezers dependent suspension with shock absorbers; rear axle is active with a symmetrical taper differential with active torque distribution on both sides; rear wheel tires are dual tires on each side; The passenger car frame is in the form of two longitudinal beams supporting the engine and the cabin
2.1.3 Assumptions when building models
With the analysis of the object structure studied, the thesis makes some necessary assumptions to build a passenger car dynamics model to study the guideability as follows:
With the analysis of the object structure studied, the thesis makes some necessary assumptions to build a dynamic model of passenger cars to study the guideability as follows:
1 Distribution of mass of passenger cars symmetrically about the longitudinal axis of the vehicle; the mass is concentrated at the longitudinal axis of the vehicle;
2 The center of gravity of the suspended mass, which is not
Trang 9suspended, lies in the plane of longitudinal symmetry of the vehicle;
3 The bridge does not rotate on the horizontal axis;
4 The points where the force from the suspension is applied to the mass to be suspended are referred to the point corresponding to the midpoint of the spring;
5 Dual wheels are referred to as single wheels with double wheel stiffness equal to 2 times of single wheel;
6 Absolutely flat road with zero bumpy height;
7 Neglect the elastic effect of the steering system;
8 Neglect the effect of horizontal aerodynamic drag;
9 Ignore the effect of wheel camber;
10 The angular speed of the guide wheel is constant;
11 Consider the coefficient of traction at the wheels to be constant;
12 Consider the chassis to be absolutely rigid;
13 The vertical angle of inclination of the mass is not suspended h = 0;
14 Vertical angle of inclination of the suspended mass n =
2.2 Building a dynamic model
Building a system of dynamic equations in the road plane, longitudinal plane and transverse plane of passenger cars
The survey model is shown below:
Fig 2 1 3-mass spatial model to study the handling of passenger
cars
Trang 102.3 Set up a system of mathematical equations
2.3.1 Reference system
To establish a mathematical model describing the movement
of a passenger car based on specific assumptions and reference systems as follows:
Fig 2 2 Survey coordinate system
The dynamic model is described by 16 degrees of freedom:
- 6 degrees of freedom of suspended mass: longitudinal translation (x) and rotation (γk) along the axis Ox, horizontal translation (y) and rotation (n) along the axis Oy, move up and down (z) and rotation (ωa) along the axis Oz
- 6 degrees of freedom for the unsuspended mass are the axles: vertical (ξci) along the axis Cizi, translation (yci) along the axis Ciyi và horizontal shake (βci) around the axis Cixi (i=1,2)
- 4 degrees of freedom for each wheel describing the angle of rotation (φci) wheel (1x4 wheel) The equations of dynamics:
(2.44)
Trang 112.3.3 Tire model
The thesis uses the Pacejka tire model [29] which is a complex model but has quite enough input factors of shape, size, speed, pressure, temperature affecting the tire (Fig 2.3)
Fig 2 3 Performance of tires according to the Pacejka model
+ Side slip angle of handling wheels [5]:
x a 1T 1T
Trang 12For the relationship between the side slip angle of the wheel
and side reaction Y, Pacejka's "Magic Formula" empirical formula has the following form: [29][39]
sin arctan arctan
ij ij Xij X Xij ij Xij Xij ij Xij ij
sin arctan arctan
ij ij Yij Y Yij ij Yij Yij ij Yij ij
sin arctan arctan
zij zij z zij ij zij zij ij zij ij
2.3.4 Determination of aerodynamic drag
22
3.1.1 Handling assessment criteria
The car's handling, especially the front and rear axle deflection δ1, δ2 has a great influence on controllability and orbital stability (stable motion direction) To investigate the handling, there are experimental survey options [9] such as:
- Traction stability when changing lanes
- Stabilization of linear motion
- Calculate the rotation of the car
The important indicators of guideability [9][49] such as:
- Velocity vx; The difference in side slip angle of the front axle δ1 and rear axle δ2; Control sensitivity; The angle of rotation, speed and force acting on the steering wheel rim; Displacement, velocity, horizontal acceleration; Angle, rotational speed of the vehicle body; Body tilt angle; Turning radius R; Motion trajectory
In the framework of the thesis, choose the option to calculate the rotation of the car and the survey parameters of the car's navigation as follows:
- Effect of tire pressure on front and rear side slip angle difference;
- Effect of tire pressure on horizontal acceleration;
Trang 13- Effect of tire pressure on vehicle body rotation speed;
- Effect of tire pressure on motion trajectory
3.1.2 Survey options
3.1.2.1 For tire model
Tab 3 1 Tire model survey modes
Parameter
Plan
Tire pressure (kPa)
Weight (kN)
v (km/h)
Evalua Criteria Present
Investigate the effect
3.1.2.2 For the 3-mass spatial model of navigability research
Survey in the case of a car turning around with a constant
angle of rotation of the steering wheel, constant speed
Tab 3 2 Surveying modes 3-mass spatial model 3 study handling
Parameter
Plan
Tire pressure (kPa)
Steering wheel rotation angle (degree)
v ( km/h)
Evalua Criteria
Prese
nt
Plan 1:
Effect of tire pressure
on front and rear side
slip angle difference
1T 0 180
- t2 đến t3
1T 180
20,
30, 40
front and rear side slip angle difference
on
3.3.3
Phương án 3: Effect of
tire pressure on vehicle
body rotation speed
motion trajectory
3.3.4 Phương án 4:
Effect of tire pressure
3.2 Survey conditions
3.2.1 Rules of steering
Trang 14Fig 3 1 Rotation angle of theoretical and experimental steering
wheel 3.2.2 Algorithm to solve system of differential equations by numerical simulation software
3.3 Investigate the influence of some parameters on the car's handling
3.3.1 Tire characteristic survey
Investigate the effect of tire pressure on side slip angle
Fig 3 2, 5, 6 Relationship of roll angle and horizontal force F y at
2, 4, 6 kN
From Figures 3.4, 3.5, 3.6, it shows that when the horizontal force increases, the deflection angle increases, this relationship is considered linear when the side slip angle deviates in the range
0o~3o
As tire pressure decreases, the lateral stiffness of the tire decreases (The angle between the graph line and the horizontal axis increases)
3.3.2 Investigate the effect of tire pressure on the difference
in side slip angle at different speeds
3.3.2.1 The pressure of both front tires is reduced