Modeling and Simulation of Hydraulic Winch Systems for Offshore Cranes

Abstract

This thesis deals with the mathematical modeling and simulation of hydraulic controlled winch systems. Winch systems are commonly used in the hoisting and luffing systems of offshore cranes. When considering the hydraulic controlled winch there are mainly two concepts that are used, namely valve control and pump control. The choice of control concept is related to the intended operational conditions of the system and to the preferences of the system developer. The winch systems can be modeled in Simulink. If the systems are modelled in an object oriented fashion, it is possible to easily include these as submodules in a larger and more complex system. Imposing real-time properties on the simulator, gives the possibilities of using the simulator for what is known as textit{Hardware In the Loop} or HIL testing, testing e.g. system controllers without the need of the physical crane. This may reduce the total project cost, reduce the risk of accidents at the case of regulator deficiencies, and reduce the development time.Methods for modeling winch systems in Simulink will be presented throughout this thesis. These models may be used as submodules in a complete crane simulator. Both the valve controlled and pump controlled systems are simulated by a using module based object oriented programming scheme, creating individual Simulink blocks of the physical component of the system. The Simulink model of the latter control concept is simplified to increase calculation speed, imposing certain real-time qualities, i.e. a predictable calculation time faster than real-time. The increased predictability is achieved by using a fixed step solver.