Software implemented fault tolerance of triple-redundant dynamic positioning (DP) control system

Abstract

ABSTRACTDynamic Positioning (DP) system is an essential requirement for marine vessels and in most offshore operations, especially in deepwater oil and gas production units. A single point of failure in DP system may result in serious financial loss, or injury to people and ecological harm, hence it is important to improve the operational availability and reliability for DP operated vessels by employing advanced fault-tolerant technique making it possible to conduct the specified operation in harsh water. This paper presents a DP control solution of triple-modular redundant hardware and triple-version programming software for the dynamically positioned vessels. To arbitrate and detect any error of the triple-redundant control computers, a novel majority voting algorithm is proposed by introducing the voter threshold and comparison threshold to check the distances between distinct voter inputs. Consider the single point of failure of the voter in general triple-redundant voting system, the software voter is designed attaching to each of the control computers. Finally, DP dynamic simulation with environmental modelling of wind, current and waves are carried out to demonstrate the feasibility of the fault-tolerant software implementation.