Basic Autonomous Vehicle Controller Development through Modeling and Simulation 2018-01-0041
Autonomous vehicles at various stages will impact the future of transportation by improving reliability, comfort and safety of the passengers. In this paper, for an existing experimental vehicle, fitted with various sensors and actuators typically required by autonomous vehicles, a basic level-1 autonomous controller for braking and throttle actuations is proposed. This controller is primarily developed for stop-and-go scenarios along with the additional functionalities of automatic cruise control (ACC) and automatic emergency braking (AEB). Since the rigorous testing of autonomous vehicle in actual roads can be time consuming, costly and having safety issues, a simulation test-bench based approach is considered to develop and test the controller. The controller, based on practical data is developed in simulation environment to primarily maintain safe distance from surrounding traffic objects while fulfilling requirements such as jerk levels, conditional braking, speed limits, etc. In this work, only a longitudinal controller is developed for low speeds (<30 kmph) and low throttle scenarios for which a four-wheel based vehicle dynamics model is formulated excluding the nonlinear tire model. Experimental data while running the experimental vehicle in actual traffic is acquired from camera, triangulation of ultrasonic sensors, throttle, brake pedal position and velocity of the vehicle and is used for tuning and validation of the derived model, to ensure satisfactory accuracy. Accordingly, a relative distance and relative velocity dependent longitudinal controller comprising of several coordinated PID controllers is designed in stop-and-go scenario and in AEB mode. The captured pre-recorded traffic video along with acquired throttle, braking, speed and relative distance information is synced with the proposed controllers simulation execution for correlations, wherein the acquired relative distance data is used as reference to run the simulations. The proposed practical data based simulation test environment is successful in creating multiple test scenarios and the developed longitudinal controller is able to satisfactorily autonomously control the vehicle in the desired manner.