In a platoon control system, fixed and symmetrical topology is quite rare because of adverse communication environments and continuously moving vehicles. This paper presents a structurally decomposed control method for vehicular platoon systems by combining the LMI (Linear Matrix Inequality) approach to handle uncertain interaction topologies. This approach allows the nodes to interact with either other via different types of eigenvalue-bounded topologies, e.g., either asymmetrical or symmetrical, either fixed or switching. Different from existing matrix factorization technique, it does not require the exact values of each entity in topological matrix, and only needs to know the bounds of its eigenvalues, which can still ensure that the poles of the closed-loop dynamics lie inside the predefined region so as to balance quickness and smoothness. The effectiveness of proposed method is validated by numerical simulations.