Dynamic positioning systems(DPS)on marine vessels exhibit actuator redundancy,with more actuators than degrees of freedom.A control allocation unit is employed to address this redundancy.Practical systems often featur...Dynamic positioning systems(DPS)on marine vessels exhibit actuator redundancy,with more actuators than degrees of freedom.A control allocation unit is employed to address this redundancy.Practical systems often feature time-varying elements in the effectiveness matrix due to factors such as changing operating conditions,nonlinearity,and disturbances.Additionally,not all thrusters require engagement at each step to counteract disturbances and maintain position.Control efforts can be generated by selecting some thrusters based on their instant effectiveness,while others can remain on standby.Therefore,introducing a control allocation method that calculates the effectiveness matrix online and selects the most efficient thrusters could be effective.This paper introduces a fault-tolerant control allocation strategy for DPS with a varying effectiveness matrix.Specifically,the investigation focuses on a case study featuring eight azimuth thrusters used on a drilling rig.At each time step,the effective matrix is calculated online,followed by the selection of the four most effective thrusters based on the actuator effectiveness index,with the four serving as backups in case of a fault.The proposed strategy has been validated through simulation results,demonstrating advantages such as robustness against changes in the effectiveness matrix and reduced energy usage by the thrusters.展开更多
The consequences of ship collisions with an oil rig, offshore installation or platform can be far more expensive in relation to safety, environment and costs of damage. The damage due to a single incident of an Oil Ri...The consequences of ship collisions with an oil rig, offshore installation or platform can be far more expensive in relation to safety, environment and costs of damage. The damage due to a single incident of an Oil Rig Collision can be catastrophic due to the number of people on board and the added risk of explosion. However, the existing rules and regulations of collisions prevention are insufficient. The purpose of this article is to critically evaluate the risk of ships collisions with offshore platforms and installations and therefore propose an international regulation for the preventions of this type of collisions.展开更多
Based upon the main properties of the relational analysis in grey system theory, a new method to select optimal drill rigs is proposed in this paper. Under the unified technique economic index, with the practical data...Based upon the main properties of the relational analysis in grey system theory, a new method to select optimal drill rigs is proposed in this paper. Under the unified technique economic index, with the practical data of four kinds of drill rigs in the mining district, east of Sichuan, China, an optimal reference number series was constructed. Through calculating the relational grade between the technique economic indices of various drill rigs and the reference number series and making a relational sequence in accordance with priority, the results achieved are in conformity with that of reference by Fuzzy Set Theory, and grey situation decision making and yet this method is simple, easy and intuitive in analysis etc..展开更多
This paper presents experimental rigs of the Research Centre for the Mechanics of Turbomachinery of the Department of Civil and Industrial Engineering of the University of Pisa. Most of them were designed and construc...This paper presents experimental rigs of the Research Centre for the Mechanics of Turbomachinery of the Department of Civil and Industrial Engineering of the University of Pisa. Most of them were designed and constructed to allow investigations of real machine components and to furnish more realistic results than basic tribological test rigs. Tilting pad journal bearings, as well as gears and complete gearboxes for advanced industrial applications, can be tested using the rigs described in the paper. A novel test rig with a power rating of approximately 1 MW allows investigations of the static and dynamic characteristics of high-performance tilting pad journal bearings for turbomachinery. A twin disc machine and closed loop gear test rig are used to investigate the different kinds of wear mechanisms occurring in gears. Functional and durability tests on planetary gearboxes for new turbo-fan engines could be performed using another novel large test rig. A circulating power configuration was adopted for most of the rigs so that only the power needed to cover the friction losses has to be supplied, while the circulating power can be more than 20 times higher. All the test rigs include very complex load applications and lubrication plants, as well as dedicated control and data acquisition systems. The rigs and related plants were designed and constructed through strong and fruitful collaborations between the university and some large and small–medium companies. Despite some limitations in the publication of the results as a result of the industrial sensitivity of the data, the synergy among these different actors was stimulating and fundamental for the realization of new advanced industrial applications.展开更多
The structural failures of jack-up rigs were mostly found in leg structures,due to cracks in way of connections between tubular members of leg structures.Although,stress calculations of leg structures can be made by u...The structural failures of jack-up rigs were mostly found in leg structures,due to cracks in way of connections between tubular members of leg structures.Although,stress calculations of leg structures can be made by using“finite element techniques”,it takes a lot of time to complete the calculations for the full cases of all working conditions because of many tubular members.Therefore,a simple method for the stress calculations for design purposes is strongly desired.This paper desribes a simple stress calculaiton method of leg structures and shows a satisfactory results as compared with the results obtained by a detailed calculation method.展开更多
2The joint opening degree is a critical index for assessing the stability of jointed rock masses,which directly impacts the rock mass quality.It is also a key factor influencing the design of tunnel support structures...2The joint opening degree is a critical index for assessing the stability of jointed rock masses,which directly impacts the rock mass quality.It is also a key factor influencing the design of tunnel support structures.Hammer and rotary drilling rigs,commonly employed as rock-breaking equipment in tunneling,inevitably encounter joints with varying opening degrees during construction.This research aims to enhance the sampling frequency of hammer and rotary drilling rigs and optimize the joint detection algorithm,thereby equipping these rigs with the capability to detect joint opening degrees.This paper develops high-frequency acquisition equipment for drilling parameters to realize millimeter-level data acquisition.Drilling experiments on jointed rock mass are conducted under conditions corresponding to joint opening degrees of 1 mm,3 mm,and 5 mm.The relationships among joint opening degree,drilling parameters,and width of rock failure region are investigated.A joint opening degree detection algorithm is proposed based on the drilling parameters and moving average filter.The results indicate that the curves of penetration velocity and rotary pressure along the drilling direction exhibit a three-segment distribution,i.e."stable segment-adjustment segment-stable segment".The variation curves of drilling parameters display a“velocity mountain”and a“pressure valley”in the failure region.The relative errors in joint opening degree estimation based on penetration velocity and rotary pressure range from 3.4%to 32%and from 6%to 35%,with average relative errors of 12.95%and 16.24%,respectively.展开更多
文摘Dynamic positioning systems(DPS)on marine vessels exhibit actuator redundancy,with more actuators than degrees of freedom.A control allocation unit is employed to address this redundancy.Practical systems often feature time-varying elements in the effectiveness matrix due to factors such as changing operating conditions,nonlinearity,and disturbances.Additionally,not all thrusters require engagement at each step to counteract disturbances and maintain position.Control efforts can be generated by selecting some thrusters based on their instant effectiveness,while others can remain on standby.Therefore,introducing a control allocation method that calculates the effectiveness matrix online and selects the most efficient thrusters could be effective.This paper introduces a fault-tolerant control allocation strategy for DPS with a varying effectiveness matrix.Specifically,the investigation focuses on a case study featuring eight azimuth thrusters used on a drilling rig.At each time step,the effective matrix is calculated online,followed by the selection of the four most effective thrusters based on the actuator effectiveness index,with the four serving as backups in case of a fault.The proposed strategy has been validated through simulation results,demonstrating advantages such as robustness against changes in the effectiveness matrix and reduced energy usage by the thrusters.
文摘The consequences of ship collisions with an oil rig, offshore installation or platform can be far more expensive in relation to safety, environment and costs of damage. The damage due to a single incident of an Oil Rig Collision can be catastrophic due to the number of people on board and the added risk of explosion. However, the existing rules and regulations of collisions prevention are insufficient. The purpose of this article is to critically evaluate the risk of ships collisions with offshore platforms and installations and therefore propose an international regulation for the preventions of this type of collisions.
文摘Based upon the main properties of the relational analysis in grey system theory, a new method to select optimal drill rigs is proposed in this paper. Under the unified technique economic index, with the practical data of four kinds of drill rigs in the mining district, east of Sichuan, China, an optimal reference number series was constructed. Through calculating the relational grade between the technique economic indices of various drill rigs and the reference number series and making a relational sequence in accordance with priority, the results achieved are in conformity with that of reference by Fuzzy Set Theory, and grey situation decision making and yet this method is simple, easy and intuitive in analysis etc..
基金co-financed by the Region of Tuscany in the framework of the ATENE projectby the European Clean Sky platform
文摘This paper presents experimental rigs of the Research Centre for the Mechanics of Turbomachinery of the Department of Civil and Industrial Engineering of the University of Pisa. Most of them were designed and constructed to allow investigations of real machine components and to furnish more realistic results than basic tribological test rigs. Tilting pad journal bearings, as well as gears and complete gearboxes for advanced industrial applications, can be tested using the rigs described in the paper. A novel test rig with a power rating of approximately 1 MW allows investigations of the static and dynamic characteristics of high-performance tilting pad journal bearings for turbomachinery. A twin disc machine and closed loop gear test rig are used to investigate the different kinds of wear mechanisms occurring in gears. Functional and durability tests on planetary gearboxes for new turbo-fan engines could be performed using another novel large test rig. A circulating power configuration was adopted for most of the rigs so that only the power needed to cover the friction losses has to be supplied, while the circulating power can be more than 20 times higher. All the test rigs include very complex load applications and lubrication plants, as well as dedicated control and data acquisition systems. The rigs and related plants were designed and constructed through strong and fruitful collaborations between the university and some large and small–medium companies. Despite some limitations in the publication of the results as a result of the industrial sensitivity of the data, the synergy among these different actors was stimulating and fundamental for the realization of new advanced industrial applications.
文摘The structural failures of jack-up rigs were mostly found in leg structures,due to cracks in way of connections between tubular members of leg structures.Although,stress calculations of leg structures can be made by using“finite element techniques”,it takes a lot of time to complete the calculations for the full cases of all working conditions because of many tubular members.Therefore,a simple method for the stress calculations for design purposes is strongly desired.This paper desribes a simple stress calculaiton method of leg structures and shows a satisfactory results as compared with the results obtained by a detailed calculation method.
基金the National Natural Science Foundation of China(No.52378411)for the support in this research.
文摘2The joint opening degree is a critical index for assessing the stability of jointed rock masses,which directly impacts the rock mass quality.It is also a key factor influencing the design of tunnel support structures.Hammer and rotary drilling rigs,commonly employed as rock-breaking equipment in tunneling,inevitably encounter joints with varying opening degrees during construction.This research aims to enhance the sampling frequency of hammer and rotary drilling rigs and optimize the joint detection algorithm,thereby equipping these rigs with the capability to detect joint opening degrees.This paper develops high-frequency acquisition equipment for drilling parameters to realize millimeter-level data acquisition.Drilling experiments on jointed rock mass are conducted under conditions corresponding to joint opening degrees of 1 mm,3 mm,and 5 mm.The relationships among joint opening degree,drilling parameters,and width of rock failure region are investigated.A joint opening degree detection algorithm is proposed based on the drilling parameters and moving average filter.The results indicate that the curves of penetration velocity and rotary pressure along the drilling direction exhibit a three-segment distribution,i.e."stable segment-adjustment segment-stable segment".The variation curves of drilling parameters display a“velocity mountain”and a“pressure valley”in the failure region.The relative errors in joint opening degree estimation based on penetration velocity and rotary pressure range from 3.4%to 32%and from 6%to 35%,with average relative errors of 12.95%and 16.24%,respectively.
