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A Stability-Guaranteed Time-Delay Range for Feedback Control of Autonomous Vehicles
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on April 14, 2020 by SAE International in United States
The vehicles with level-5 autonomy (L5AVs) have no human driver in the loop are also known as self-driving cars. L5AVs are assumed the next generation of ground transportation, which have growing attention from both industry and academia in most recent years. Most of the work related to feedback strategies of L5AVs are on developing mapping systems through a variety of sensors. These systems can be considered as an analogue to the perception and central nervous system of human drivers. For instance, innovative visualization systems are more powerful when compared to the visual perception system of a person, yet, mapping demands high computation loads. This burden causes delay in the feedback loop and thus, it might have an unfavorable influence on proper and safe control action. This study investigates the effect of time delay occurring in mapping systems on the stability of the controlled vehicle. An algorithm entitled as “Cluster Treatment of Characteristic Roots - CTCR” is used to calculate a safe delay range as a remedy for the time delay caused by mapping systems. The CTCR analysis is applied to a linearized two degree-of-freedom bicycle model for different velocities. The critical time delay values, which determines the boundary between the stability and instability of the controlled vehicle, are calculated based on the vehicle dynamics. Finally, results are drawn for a regular weave test by computer simulations, in which a non-linear vehicle model is used. The proposed approach is validated by exhibiting that a delay value outside the safe range leads the vehicle instability.