“…As an alternative to gradient-based algorithms, Rojas et al [16,23] employ a genetic algorithm (GA) [24] to perform the task of searching for the optimal parameters. The nonlinear part of the Hammerstein system is represented by a polynomial composed exclusively of monomials of odd power, and, in view of the fact that the theoretical separability condition [5] requires that gðf ðÁÞÞ be a monotonic function, all of its coefficients are constrained to be positive.…”