K. Balachandran et N. Rajagopal, Optimal control of nonlinear delay systems with implicit derivative and quadratic performance, KYBERNETIKA, 35(2), 1999, pp. 225-233
The existence of optimal control for nonlinear delay systems having an impl
icit derivative with quadratic performance criteria is proved. The results
are established by an iterative technique and using the Darbo fixed point t
heorem.