To address issues such as communication delays, resource constraints, aggregate perturbation, and non-ideal communication topologies encountered by intelligent and connected vehicles in a communication-limited environment, an observer-based coordinated formation control strategy is proposed. Firstly, the vehicle platoon system is dynamically modeled based on the four-element model. Then, to solve problems such as unmeasurable partial system states, aggregate perturbation, and measurable noise, an integral observer is designed. Based on this observer, a coordinated formation control strategy is formulated. Subsequently, an error system is constructed and an $H_\infty$ performance metric is introduced. By employing a Lyapunov-Krasovskii functional to handle varying time delays, the observer-based formation control problem is transformed into a stability problem for the error system. Stable sufficient conditions are derived, and simulation results verify the correctness and effectiveness of the proposed method.