Coarticulation during speech production takes place at both the physiological level concerned with articulators' properties and the planning stage for elaborating motor commands. This study focuses on the investigation and modeling of planning aspects of coarticulation with the ultimate objective to implement human mechanism in controlling a physiological speech production model. A "carrier model" was derived from articulatory data to describe mechanisms of the coarticulation, in which the vocalic movement is considered to be the primary component as a "carrier wave" and the consonantal movement as a "modulation wave". Interactions between the carrier and modulation waves were evaluated using phoneme sequences of V bCV cCV b (V c: the central vowel; V b: the bilateral vowel; C: consonants) out of articulatory data that was obtained from the electromagnetic articulographic system. The analysis of the articulatory data showed that the articulatory position of the central vowel tended to be assimilated towards that of the bilateral vowels.