Dynamic analysis of off-road vehicles

In order to improve the steering performance of vehicles on low adhesion roads, this paper proposed a drift control method by coordinating the steering angle and the rear wheel slip ratio. Because lateral force of rear wheels is saturated with high longitudinal slip ratio under the drift condition, a vehicle dynamic model considering the coupling of the rear wheels’ longitudinal and lateral force is established. In view of the fact that the lateral tire force is affected by the nonlinearity of sideslip angle and slip ratio, the vehicle dynamic model is complex and makes it difficult for controller design. Due to this, a description method of the nonlinear relationship is presented for simple which introduces a virtual control quantity representing the influence of slip ratio on lateral tire forces based on the function of tire force with sideslip angle and slip ratio. Then, a sliding mode control method is proposed to ensure the stability of the closed-loop system and an off-line two-dimensional map is constructed to convert the virtual control quantity into the actual control quantity. The simulation results in the high-precision vehicle dynamics simulation software show that even if the initial state is far from the equilibrium point of drift, the drift controller also can ensure the stability of the closed-loop system and achieve a good drift performance.

Development and evaluation of an in-situ tire testing facility with variable side slip angles

Measurement of forces acting on 4WD-4WS tractor tires during steady-state circular turning in a rice field

The active safety systems, such as Electronic Stability Program (ESP) and Traction Control System (TCS), have been used widely in the modern production auto-mobile. These safety control systems function well only when the vehicle motion information is known. To achieve this purpose, various sensors are equipped in the production cars in order to detect vehicle motion information like yaw, wheel velocities and accelerations. However some key variables of the vehicle dynamic and road conditions, such as the sideslip angle, the tire road forces and the tire road friction coefficient are difficult to measure directly for technology or economic reasons. A new observer which uses the unscented Kalman filter to estimate simultaneously the sideslip angle, lateral tire road forces and the tire road friction coefficient has been proposed in this paper. The advantage of this observer is that no additional sensors is needed when the ESP has been installed in the auto-mobile. The performance of the proposed observer is demonstrated through the Chicane test.

This paper describes a Variable Structure Model Reference Adaptive Control (VS – MRAC) for active steering assistance of a two wheel steering vehicle. Its main goal is to avoid lane departures. The controller steers an equipped vehicle along a specially marked lane without cross-over lane markings. The stability of the system is checked by lyapunov theory. First, the vehicle dynamics for typical lateral maneuvers are described by Newton's formulation. Next, we are used torsional damper in model reference for comeback of vehicle to reference marked lane when the vehicle departure from reference marked lane. The proposed system can treat the nonlinear relationships between the side slip angles and lateral forces on tire, and the uncertainties on friction of the road surface, whose compensation are very important under critical situations. Finally, simulation results show that controller performance is stable and has robust capability on meandering roads.

Vehicle dynamics estimation has been the subject of study for some years now. If on-board vehicle control systems can be provided with information such as side slip angle, lateral force etc. then stability of the vehicle can be improved. To estimate these dynamic variables different observers have been used e.g., sliding mode, fuzzy logic, neural networks etc. In this article the authors propose an extended Kalman lter to estimate vehicle side slip angle. Roll angle is estimated using vertical loads as input. First, a linear Kalman lter is used to lter out the vertical forces and estimate roll angle. This information is then used to estimate the vehicle side slip angle. To take into account the nonlinearities concerning lateral vehicle dynamics, Pacejka magic formula is used to model lateral forces. Estimated results are then compared with simulations, showing good accuracy.

Extensive research has shown that most of road accidents occur as a result of driver errors. A close examination of accident data reveals that losing the vehicle control is responsible for a huge proportion of car accidents. Preventing such kind of accidents using vehicle control systems, requires certain input data concerning vehicle dynamic parameters and vehicle road interaction. Unfortunately, some parameters like tire-road forces and sideslip angle, which have a major impact on vehicle dynamics, are difficult to measure in a car. Therefore, this data must be estimated. Due to the system nonlinearities and unmodeled dynamics, two observers derived from extended and unscented Kalman filtering techniques are proposed and compared. The estimation process method is based on the dynamic response of a vehicle instrumented with cheap, easily-available standard sensors. Performances are tested and compared to real experimental data acquired using the INRETS-MA Laboratory car. Experimental results demonstrate the ability of this approach to provide accurate estimations, and show its practical potential as a low-cost solution for calculating lateral-tire forces and sideslip angle.

Numerical simulations are performed to investigate the influence of crosswind on the aerodynamic characteristics of rigid dragonfly-like flapping wings through the solution of the three-dimensional unsteady Navier-Stokes equations. The aerodynamic forces, the moments, and the flow structures of four dragonfly wings are examined when the sideslip angleϑbetween the crosswind and the flight direction varied from 0oto 90o. The stability of the dragonfly model in crosswind is analyzed. The results show that the sideslip angleϑhas a little effect on the total time-average lift force but significant influence on the total time-average thrust force, lateral force, and three-direction torques. An increase in the sideslip angle gives rise to a larger total time-average lateral force and yaw moment. These may accelerate the lateral skewing of the dragonfly, and the increased rolling and pitching moments will further aggravate the instability of the dragonfly model. The vorticities and reattached flow on the wings move laterally to one side due to the crosswind, and the pressure on wing surfaces is no longer symmetrical and hence, the balance between the aerodynamic forces of the wings on two sides is broken. The effects of the sideslip angleϑon each dragonfly wing are different, e.g.,ϑhas a greater effect on the aerodynamic forces of the hind wings than those of the fore wings. When sensing a crosswind, it is optimal to control the two hind wings of the bionic dragonfly-like micro aerial vehicles.

Nonlinear modeling and identification of an autonomous tractor–trailer system

The direct yaw moment control system is able to greatly enhance the vehicle stability when driving on challenging road surfaces. This paper introduces a direct control approach for managing the vehicle yaw moment, utilizing terminal sliding mode control and a square root cubature Kalman filter (SRCKF). Initially, the longitudinal and lateral forces acting on the vehicle’s tires are estimated through a sliding mode observer. Subsequently, the SRCKF algorithm and the four-wheel tire force are employed to accurately estimate the yaw rate and sideslip angle. Based on these estimations, additional yaw moments are determined using the terminal sliding mode control algorithm, and a combined control of yaw rate and sideslip angle is achieved through a threshold method. A rule-based braking force distribution strategy is then implemented to ensure vehicle stability control. Simulation results demonstrate that the tire force estimations from the sliding mode observer and the vehicle yaw rate and sideslip angle estimations from the SRCKF algorithm closely align with the output results from Carsim, with an error margin of less than 15%. The braking force distribution strategy, based on the direct yaw moment control using the terminal sliding mode algorithm, effectively tracks the desired yaw rate and sideslip angle.

Cyclic behavior of an energy dissipation system with steel dual-ring dampers (SDRDs)

As a nonlinear dynamic system, the dynamic equation of triboelectric nanogenerator system is not only difficult to accurately establish, but also difficult to solve. The output signals of triboelectric nanogenerator system depends on the initial conditions of the system, which reflects the dynamic behavior of the system. Currently, there is little research on using the output signals to study the dynamic behavior of triboelectric nanogenerator system. Therefore, a dynamic simulation model of a freestanding triboelectric nanogenerator (F-TENG) system was established using COMSOL software. The mathematical model of the F-TENG system was fitted. Using chaos theory and its phase-space reconstruction technology, the phase-space trajectories of the F-TENG system were reconstructed through voltage signals under external factors, and the dynamic behavior of the F-TENG system was discussed and studied. Finally, validation experiments were carried out. The research shows that with the variation of internal factors and operating frequency, the mathematical model of the F-TENG system remains basically unchanged, and the variation law of output characteristics also remains basically unchanged. The F-TENG system is in periodic motion; with the variation of external factors such as resistance and friction layer spacing, the mathematical model of the F-TENG system will evolve in a complex direction, and the output characteristics will gradually distort. The F-TENG system will evolve from periodic motion to chaotic motion. The research results not only reveal the dynamic behavior and enrich the nonlinear dynamic theory of triboelectric nanogenerator system, but also provide theoretical guidance for increasing the working bandwidth and stability of triboelectric nanogenerator system.

and stability derivatives have been developed for basic shapes, including sharp cones, spherical segments, cylindrical segments, and at plates at varying angles of attack and sideslip. Each basic shape has been generically parametrized, requiring the development of only a single set of analytic relations for each basic shape. These basic shapes can be superimposed to form common entry vehicles, such as spherecones and blunted biconics. Using Bezier curves of revolution, more general bodies of revolution are studied in which the location of the control nodes that dene the shape of the curve is also generically parametrized. Analytic relations at unshadowed total angles of attack have been developed for these congurations. Analytic aerodynamic equations are orders of magnitude faster than commonly used panel methods and were validated using the NASA-developed Conguration Based Aerodynamics tool. Consequently, rapid aerodynamic trades and shape optimization can be performed. Additionally, the relations may impact guidance design using onboard trajectory propagation, real-time ablation modeling in simulations, and simultaneous vehicle-trajectory optimization.

This paper develops generalized analytical first and second order transfer functions for the nonlinear second order system. A periodic input is also conducted to characterize the overall system response from the fundamental components. The proposed analytical solution provides more understanding of the influence of each linear and nonlinear component on the overall system behavior.

An interesting problem in plasma physics, when approached from the point of view of Statistical Mechanics is to obtain properties of collisionless plasmas, which are described by the Vlasov equation. Through what we call the Ehrenfest procedure, which uses statistical mechanical relations we obtain expectation value relations for arbitrary observables, which allows us to study the dynamics of the Earth's Outer Radiation Belt. Focusing on the velocity fluctuations, the width of the distribution function and the pitch angle, a computer simulation was performed to describe the system in order to compare and test the Ehrenfest approach. Our results show that the change in the average width of the distribution follows the analytical relation. However, for the velocity fluctuation results are not conclusive yet and require more exploration. It remains as future work to verify the relation for the pitch angle.