Vehicle Road Departure Detection Using Measurements of Anomalies in Yawrate and Steering Torque

Open Access
Yang, Hang
Area of Honors:
Mechanical Engineering
Bachelor of Science
Document Type:
Thesis Supervisors:
  • Sean Brennan, Thesis Supervisor
  • Zoubeida Ounaies, Honors Advisor
  • Vehicle Dynamics; Road Departure; Tire Modeling; Vehicle Safety;
The research in this thesis investigates the viability of detecting vehicle road departure via the measurement of anomalies in vehicle dynamics, especially when left and right tires experience imbalance of forces (split-µ condition). This approach is based on established low-order vehicle models to facilitate real-time implementation. A physics-based one-dimensional pure-sideslip LuGre nonlinear dynamic tire model is derived to study the effects of independent tire-road friction drop on vehicle dynamics, especially on steering torque and yawrate. Vehicle states are obtained from an on-board INS system to obtain real-time estimates of model agreement with measured data from a steer-and-drive-by-wire vehicle testbed (P1). Experimental maneuvers were conducted on various surface conditions, including four tires on dry asphalt, the two passenger tires on a low-friction patch, and all four tires on a low-friction surface. These vehicle states and steering moments were recorded from INS systems and torque transducers, in an effort to identify normal and abnormal driving modes. Off-line simulations were performed to investigate the effects of tire nonlinearity on vehicle behavior in split- µ conditions and the feasibility of using a combination of steering torque and yawrate signals to reliably detect the imminent road departure. Results at high speeds show a yawrate mismatch between model and experimental measurements that gives a large enough signal-to-noise ratio (SNR) to allow detection using anomalies in dynamics, whereas at lower speeds measurements of steering torque may be additionally needed to improve the signal-to-noise ratio. A combination of steering torque and yawrate measurements is needed to obtain comprehensive information to allow detection and determination of vehicle road departure events.