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- All Subjects: Vehicle Dynamics
- Creators: Ren, Yi
Description
The tire blowout is potentially one of the most critical accidents that may occur on the road. Following a tire blowout, the mechanical behavior of the tire is extremely affected and the forces generating from the interaction of the tire and the ground are redistributed. This severe change in the mechanism of tire force generation influences the dynamic characteristics of the vehicle significantly. Thus, the vehicle loses its directional stability and has a risk of departing its lane and colliding with other vehicles or the guardrail. This work aims to further broaden our current knowledge of the vehicle dynamic response to a blowout scenario during both rectilinear and curvilinear motions. To that end, a fourteen degrees of freedom full vehicle model combined with the well-grounded Dugoff’s tire models is developed and validated using the high fidelity MSC Adams package. To examine the effect of the tire blowout on the dynamic behavior of the vehicle, a series of tests incorporating a tire blowout is conducted in both rectilinear and curvilinear maneuvers with different tire burst locations. It is observed that the reconstruction of the tire forces resulting from blowout leads to a substantial change in the dynamics of the vehicle as well as a severe directional instability and possibly a rollover accident. Consequently, a corrective safety control system utilizing a braking/traction torque actuation mechanism is designed. The basic idea of the stability controller is to produce a regulated amount of input torque on one or more wheels apart from the blown tire. The proposed novel control-oriented model eliminates the simplifying assumptions used in the design of such controllers. Furthermore, a double integrator was augmented to enhance the steady-state performance of the sliding mode closed-loop system. The chattering problem stemmed by the switching nature of the controller is diminished through tuning the slope of saturation function. Different apparatuses are used in terms of actuation, using an individual front actuator, utilizing multi-actuator, and using two-wheel braking torques successively. It is found that the proposed controllers are perfectly capable of stabilizing the vehicle and robustly track the desired trajectory in straight-line and cornering maneuvers.
ContributorsAl-Quran, Mahdi (Author) / Mayyas, Abdel Ra'Ouf (Thesis advisor) / Shuaib, Abdelrahman (Committee member) / Chen, Yan (Committee member) / Ren, Yi (Committee member) / Yong, Sze (Committee member) / Arizona State University (Publisher)
Created2021
Description
In the development of autonomous ground vehicles (AGVs), how to guarantee vehicle lateral stability is one of the most critical aspects. Based on nonlinear vehicle lateral and tire dynamics, new driving requirements of AGVs demand further studies and analyses of vehicle lateral stability control strategies. To achieve comprehensive analyses and stability-guaranteed vehicle lateral driving control, this dissertation presents three main contributions.First, a new method is proposed to estimate and analyze vehicle lateral driving stability regions, which provide a direct and intuitive demonstration for stability control of AGVs. Based on a four-wheel vehicle model and a nonlinear 2D analytical LuGre tire model, a local linearization method is applied to estimate vehicle lateral driving stability regions by analyzing vehicle local stability at each operation point on a phase plane. The obtained stability regions are conservative because both vehicle and tire stability are simultaneously considered. Such a conservative feature is specifically important for characterizing the stability properties of AGVs.
Second, to analyze vehicle stability, two novel features of the estimated vehicle lateral driving stability regions are studied. First, a shifting vector is formulated to explicitly describe the shifting feature of the lateral stability regions with respect to the vehicle steering angles. Second, dynamic margins of the stability regions are formulated and applied to avoid the penetration of vehicle state trajectory with respect to the region boundaries. With these two features, the shiftable stability regions are feasible for real-time stability analysis.
Third, to keep the vehicle states (lateral velocity and yaw rate) always stay in the shiftable stability regions, different control methods are developed and evaluated. Based on different vehicle control configurations, two dynamic sliding mode controllers (SMC) are designed. To better control vehicle stability without suffering chattering issues in SMC, a non-overshooting model predictive control is proposed and applied. To further save computational burden for real-time implementation, time-varying control-dependent invariant sets and time-varying control-dependent barrier functions are proposed and adopted in a stability-guaranteed vehicle control problem.
Finally, to validate the correctness and effectiveness of the proposed theories, definitions, and control methods, illustrative simulations and experimental results are presented and discussed.
ContributorsHuang, Yiwen (Author) / Chen, Yan (Thesis advisor) / Lee, Hyunglae (Committee member) / Ren, Yi (Committee member) / Yong, Sze Zheng (Committee member) / Zhang, Wenlong (Committee member) / Arizona State University (Publisher)
Created2021