Control systems are purposeful systems involving goal-oriented information processing (cyber) and technical (physical) structures. Requirements modeling formalizes fundamental concepts and relations of a system architecture at a high-level design stage and can be used to identify potential design issues early. For requirements formulation of control structures, cyber and physical aspects need to be jointly represented to express interdependencies, check for consistency and discover potentially conflicting requirements. Early identification of potential conflicts may prevent larger problems at later design stages. However, languages employed for requirements modeling today do not offer the expressiveness necessary to represent control purposes in relation to domain level interactions and therefore miss several types of interdependencies. This paper introduces the idea of control structure modeling for early requirements checking using a suitable modeling language, and illustrates how this approach enables the identification of several classes of controller conflict.