Showing 10 results for Dynamics
E. Esmailzadeh, A. Goodarzii, M. Behmadi,
Volume 1, Issue 1 (1-2011)
Abstract
Improvement in braking performance and vehicle stability can be achieved through the use of braking systems whose brake force distribution is variable. Electronic braking force distribution has an important and serious role in the vehicle stopping distance and stability. In this paper a new approach will be presented to achieve the braking force distribution strategy for articulated vehicles. For this purpose, the mathematical optimization process has been implemented. This strategy, defined as an innovative braking force distribution strategy, is based on the wheel slips. The simulation results illustrate proposed strategy can significantly improve the vehicle stability in curved braking for different levels of vehicle deceleration
S.m. Shariatmadar, M. Manteghi, M. Tajdari,
Volume 2, Issue 2 (4-2012)
Abstract
Non-linear characteristic of tire forces is the main cause of vehicle lateral dynamics instability,
while direct yaw moment control is an effective method to recover the vehicle stability. In this
paper, an optimal linear quadratic regulator (LQR) controller for roll-yaw dynamics to
articulated heavy vehicles is developed. For this purpose, the equations of motion obtained by
the MATLAB software are coded and then a control law is introduced by minimizing the local
differences between the predicted and the desired responses. The influence of some parameters
such as the anti roll bar, change the parameters of the suspension system and track wide in
articulated heavy vehicles stability has been studied. The simulation results show that the
vehicle stability can be remarkably improved when the optimal linear controller is applied
M. A. Saeedi, R. Kazemi,
Volume 3, Issue 1 (3-2013)
Abstract
In this study, stability control of a three-wheeled vehicle with two wheels on the front axle, a three-wheeled
vehicle with two wheels on the rear axle, and a standard four-wheeled vehicle are compared. For vehicle
dynamics control systems, the direct yaw moment control is considered as a suitable way of controlling the
lateral motion of a vehicle during a severe driving maneuver. In accordance to the present available
technology, the performance of vehicle dynamics control actuation systems is based on the individual
control of each wheel braking force known as the differential braking. Also, in order to design the vehicle
dynamics control system the linear optimal control theory is used. Then, to investigate the effectiveness of
the proposed linear optimal control system, computer simulations are carried out by using nonlinear twelvedegree-
of-freedom models for three-wheeled cars and a fourteen-degree-of-freedom model for a fourwheeled
car. Simulation results of lane change and J-turn maneuvers are shown with and without control
system. It is shown that for lateral stability, the three wheeled vehicle with single front wheel is more stable
than the four wheeled vehicle, which is in turn more stable than the three wheeled vehicle with single rear
wheel. Considering turning radius which is a kinematic property shows that the front single three-wheeled
car is more under steer than the other cars.
A. Jafari, Sh. Azadi, M. Samadian,
Volume 3, Issue 3 (9-2013)
Abstract
The directional response and roll stability characteristics of a partly filled tractor semi-trailer vehicle, with
cylindrical tank, are investigated in various maneuvers. The dynamic interaction of liquid cargo with the
tractor semi-trailer vehicle is also evaluated by integrating a dynamic slosh model of the partly filled tank
with five-degrees-of-freedom of a tractor semi-trailer tank model. The dynamic fluid slosh within the tank
is modeled using three-dimensional Navier-Stokes equations, coupled with volume-of-fluid equations and
analysed using the FLUENT software. The coupled tank-vehicle model is subsequently analysed to
determine the roll stability characteristics for different maneuvers. The results showed the interaction of
fluid slosh with vehicle's dynamic. Another findings of this investigation also revealed that the roll stability
of a tractor semi-trailer tank carrying liquid was highly affected by fluid sloshing and caused degradation of
roll stability in comparison with vehicle carrying rigid cargo.
S. A. Milani, S. Azadi,
Volume 4, Issue 4 (12-2014)
Abstract
Nowadays, the use of small vehicles is spreading among urban areas and one sort of these vehicles are three-wheeled vehicles (TWVs) which can be competitive with four-wheeled urban vehicles (FWVs) in aspects such as smallness, simple manufacturing, and low tire rolling resistance, fuel consumption and so on. The most critical instability associated with TWVs is the roll over. In this paper a tilt control mechanism has been modeled which can reduce the danger of roll over by leaning the vehicle towards the turning center in order to decrease the amount of lateral load transfer (LLT), and by doing so, system combines the dynamical abilities of a passenger car with a motorcycle. A 3 degree of freedom vehicle model is simulated at constant speed in MATLAB-Simulink environment and a fuzzy algorithm is developed to control such a non-linear system with appropriate tilting torque. Results are interpreted in presence and absence of controller with different longitudinal speeds and steering inputs the results are also compared to behavior of a similar FWV and this is concluded that the tilt control system could countervail deficiencies of the TWV compared to the FWV.
M. Siavashi,
Volume 6, Issue 2 (6-2016)
Abstract
In this study, a numerical computational fluid dynamics study is conducted in order to predict the aerodynamic forces on the NP car. The turbulent air flow around the car is modeled using the realizable k-ε model. First, results are validated against those presented for the Ahmed’s body. Next, the fluid flow around the car is simulated for different car speeds ( to mph) and flow directions ( to degree) and the drag and lift forces and coefficients are calculated. Increasing the car speed leads to increase of the drag and lift forces. While, the drag and lift coefficients of the car for all studied speeds are almost constant and are respectively equal to . and . . In addition, for different flow directions the drag coefficient would increase up to . . Also, the effect of mirrors on the drag force is investigated. Results reveal that removing the mirrors leads to approximately reduction in the drag force with no significant reduction in the drag coefficient. Furthermore, the effect of car elevation on the drag and lift forces is analyzed. It has been shown that when the car elevation decreases up to mm, the drag force will decrease more than , and the drag and lift coefficients are still constant. Keywords: road sign detection, text detection, object detection from video, fuzzy logic, MSER
Vahid Tavoosi, Dr Javad Marzban Rad, Dr Ramazan Mirzaei,
Volume 8, Issue 2 (6-2018)
Abstract
Vertical dynamics modeling and simulation of a
six-wheel unmanned military vehicle (MULE) studied in this paper. The Common Mobility Platform (CMP) chassis provided mobility, built around an advanced propulsion and articulated suspension system gave the vehicle ability to negotiate complex terrain, obstacles, and gaps that a dismounted squad would encounter. Aiming at modeling of vehicle vertical dynamics, basic and geometrical parameters defined and degrees-of-freedom specified on a compromise between accuracy and complexity of two models. Equations of motion provided on two linear and nonlinear 5-degree-of-freedom models using two different modeling methods. There is good agreement between time responses of two presented models. The main differences of two models observed in articulated suspension degrees-of-freedom while the vehicle subjected to high frequency maneuvers that cause severe oscillations on wheels and arms in comparison to vehicle body due to lower mass and inertia properties. The linear model can be used to design a controller and the nonlinear to predict vehicle motion more accurately. Sensitivity analysis of the influential parameters is also presented to specify effects of different parameters. Results of this study may be used to design articulated suspension and making next frequency analyses.
Pouria Ahmadi, Hossein Gharaei, Mehdi Ashjaee,
Volume 10, Issue 2 (6-2020)
Abstract
This study uses real driving cycles of a city bus and a standard driving cycle “WLTP” to implement a full comparison for energy demand and fuel consumption for different propulsion systems (i.e., Diesel ICE, Fuel cell and Electric engines). To better understand the comparison, a life cycle assessment is conducted using “GREET” and “GHGenius” software, which represents a clear demonstration of side effects and emissions of each engine on the environment. The results show that for “WLTP” cycle the bus needs 2423kJ energy for traveling each kilometer while the averaged amount of energy for traveling one kilometer of real driving cycle reaches to 1708kJ. By computing total energy use of an electric bus we conclude, electric buses use almost 58% of electric energy for driving and the rest is lost. Then fuel cell and internal combustion engine buses have energy efficiency of 36% and 24% respectively. Concerning LCA analysis, it becomes apparent that unlike efficiency, electric buses are not environmentally benign as fuel cell buses. LCA analysis showed that fuel cell buses that use steam reforming hydrogen production process are a cleaner option than electric buses. Finally, since diesel buses produce the most emission, especially CO2, and consume the most energy in the total life cycle, they have no advantage for public transportation fleet.
Farhad Pashaei, Seyed Mahdi Abtahi,
Volume 11, Issue 4 (12-2021)
Abstract
In this paper, firstly chaotic behavior of the lateral dynamics of vehicle is investigated by the use of numerical tools including Lyapunov exponent and bifurcation diagrams. To this end rout to chaos along with period doubling and quasi-periodic responses are demonstrated in terms of bifurcation diagrams. After chaos analysis, a novel controller commensurate with the chaotic characteristics of the system, in conformity with Poincaré map is represented to suppress the chaotic behavior of lateral movement. The Poincaré map of the system is derived by means of a neuro fuzzy network. A robust Fuzzy system on the basis of nonlinear Ott-Grebogi-Yorke (OGY) method forms the control system. Closed-loop results of the system shows effectiveness of the chaos controller in extreme conditions.
Ali Modarresi, Saman Samiezadeh, Ali Qasemian,
Volume 13, Issue 1 (3-2023)
Abstract
In recent years, the automotive industry has experienced a dramatic mutation in the develop ment of electric vehicles. One of the most important aspects of this type of vehicle is its thermal management. Among the various parts of an electric vehicle that are subjected to thermal management, the battery is of particular importance. Battery cell temperatures may exceed the allowable range due to continuous and high-pressure operation and various weather conditions, and this, in addition to performance, severely affects battery life. Therefore, the appropriate cooling system is essential. In this research, the most common methods of battery cooling are investigated. First, three-dimensional thermal analysis on the battery is performed using the computational fluid dynamics method in transient and steady-state phases. Then, the effect of changing the cooling flow rate on the maximum temperature of the battery cell as well as the temperature difference of the cells in the battery pack is investigated. The effect of changing inlet coolant temperature change on battery cell temperature distribution is also investigated. The results show that by increasing the flow rate from 0.5 to 1.2 liter per minute, the maximum temperature in the battery pack and the temperature difference between the cells decrease to 44.4 and 2.51 ° C, respectively. Also, by changing the temperature of the inlet coolant from 15 to 30 ° C, the maximum temperature in the battery pack increases up to 42.2 ° C and the temperature difference is negligible.
