IJAM, Volume 28, No. 2 (2015)

Abstract. In this paper, we investigate error analysis of splitting positive definite mixed finite element methods for optimal control problems with an control constraints. The finite element methods are discretized by the Raviart-Thomas mixed space and the control variable is approximated by piecewise polynomials. Finally we derive error analysis for both the control variable and the state variables, when the control is discretized by piecewise linear continuous functions and illustrate with a numerical example to confirm our theoretical results.