  This paper investigates the longitudinal control problem in a dynamic traffic
environment where driving scenarios change between free-driving scenarios and
car-following scenarios. A comprehensive longitudinal controller is proposed to
ensure reasonable transient response and steady-state response in scenarios
changes, which is independent of planning algorithms. This design takes into
account passenger comfort, safety concerns and disturbance rejections, and
attempts to meet the requirement of lower cost, faster response, increased
comfort, enhanced safety and elevated extendability from the automated vehicle
industry. Design insights and intuitions are provided in detail. Comprehensive
simulations are conducted to demonstrate the efficacy of the proposed
controller in different driving scenarios.
