Matching Items (2)
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
The human ankle is a critical joint required for mobility and stability of the body during static and dynamic activity. The absence of necessary torque output by the ankle due to neurological disorder or near-fatal injury can severely restrict locomotion and cause an inability to perform daily tasks. Physical Human-Robot Interaction (pHRI) has explored the potential of controlled actuators to positively impact human joints and partly restoring the required torque and stability at the joint to perform a task. However, a trade-off between agility and stability of the control technique of these devices can reduce the complete utilization of the performance to create a desirable impact on human joints. This research focuses on two control techniques of an Active Ankle Foot Orthosis (AFO) namely, Variable Stiffness (VS) and Variable Damping (VD) controllers to modulate ankle during walking. The VS controller is active during the stance phase and is used to restore the ankle trajectory of healthy participants that has been altered by adding a dead-weight of 2 Kgs. The VD controller is active during the terminal stance and early-swing phase and provides augmentative force during push-off that results in increased propulsion and stabilizes the ankle based on user-intuitions. Both controllers have a positive impact on Medial Gastrocnemius (GAS) muscle and Soleus (SOL) muscle which are powerful plantar - flexors critical to propulsion and kinematic properties during walking. The VS controller has recorded an 8.18% decrease in GAS and an 9.63 % decrease in SOL muscle activity during the stance phase amongst participants while decreasing mean ankle position error by 22.28 % and peak ankle position error by 17.43%. The VD controller demonstrated a 7.59 % decrease in GAS muscle and a 10.15 % decrease in SOL muscle activity during push-off amongst the participants while increasing the range-of-motion (ROM) by 7.84 %. Comprehensively, the study has shown a positive impact on ankle trajectory and the corresponding muscle effort at respective stages of the controller activity.
ContributorsSave, Omik Milind (Author) / Lee, Hyunglae (Thesis advisor) / Marvi, Hamidreza (Committee member) / Yong, Sze (Committee member) / Arizona State University (Publisher)
Created2020