“…The very same idea is spreading in many automatic control-related papers. An example is the papers by Li et al [7] and Yan et al [8], where an intelligent control system [9] is presented to improve the power supply system of this class of vessels in order to recycle cold energy produced in liquefied natural gas (LNG) carriers [10]. Since the problem of energy recovery has gained a strong interest in recent years [11], it has also been studied in a wide range of different applications, as in hydraulic systems, like excavators [12] or hydraulic cylinders [13], to reuse potential energy, thus reducing pollutants, or for improving active suspensions performances [14].…”