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Vehicle-Road Safety and Stability Envelope Definition and Protection
Author: Denis Efremov
Comparing the history of aerospace and ground vehicles, one can admit the fast growth in the complexity and computerization of aircraft during the past seven decades. This growth is based on the high cost of each aircraft and its pilot and money flow for research purposes during the Cold War. These key factors matured the aerospace industry, increasing aircraft’s agility and complexity and introducing control algorithms to reduce the burden from pilots and their mistakes or failures. On the other hand, ground vehicles have slowly started to mature in the past three decades, when the first safety algorithms, such as anti-locking braking systems, were introduced as necessary equipment for each produced vehicle. Cars are going the same way of improvement, as the aircraft did: from X-by-wire systems, through over-action of platforms (where it has more ways of actuation per degree of freedom, i.e., independent steering, braking, and driving) and definition of safety envelope (where the vehicle dynamics is not compromised and its surrounding does not make any harmful danger) to envelope protection algorithms (which enhance human operations to increase the vehicle safety and stability). This dissertation aims at the last two steps. It defines the vehicle-road envelope and introduces control algorithms to protect its boundaries. The vehicle-road envelope is strategically divided into two main parts: driving and environmental envelopes. The former defines states in vehicle dynamics space, where each wheel will not be locked, overspun, or skidding. The latter defines safe operational positions, where each wheel can be placed to avoid road departure, collisions with other road users, and drivable road irregularities, such as potholes or small objects on the road. The envelope definition is wheel-centric, allowing the utilization of this concept for any car (or any other wheeled platform) configuration. The driving envelope protection algorithm can be used as an integrated controller, which does the functionality of an anti-locking braking system, traction control, electronic stability program, and launch control systems. In the same way, the environmental envelope protection algorithm can be used as an integrated lane-keeping and collision avoidance system. However, it can also be used for semi-automated driving on regular and off-road roads.