“…This is a challenging control problem because the system is highly unstable, nonlinear and underactuated. Different control agorithms are studied by many researchers, from classical PID controllers [2], [13] to advanced controllers such as fuzzy control [3], [14] neural networks [4], [15] and genetic algorithms [5], [16]. Recently, optimal control approach is one of the potential solutions for a given set of performance objectives [17], [21], with detail review in [6].…”