Development And Research On Key Technologies Of The Strength Test Platform For Marine Emergency Towing Arrangements

The emergency towing arrangements(ETA)is a set of towing devices installed at the bow and stern of vessel.Its purpose is to reduce the deterioration of the accident by connecting the vessel to the tug quickly and easily in an accident.The International Maritime Organization(IMO)requires all new/existing tankers with a capacity of 20,000 deadweight tons or more to be fitted with ETA.As the key equipment to ensure the safety of ship navigation,the ETA not only needs the type certification of classification society,but also the whole strength test before delivery to ensure the product is qualified.At present,China does not have the complete test capacity of ETA,which restricts the development of the relevant design and manufacturing industry,so the research of test methods and the development of special testing system are imperative.With the support of State Administration for Market Regulation,the test method of the ETA,the key technology of strength test platform are studied.The main tasks accomplished are as follows:1.Based on the requirements of IMO Guidelines,the stress of the ETA under different towing angles is analyzed,and a type test method for the ETA is proposed.By arranging the inclined table under the cable guide hole and adopting the strong point single loading scheme,not only the most dangerous towing working conditions can be accurately simulated,but also the space multi-angle loading required for the test can be converted into a plane multi-angle loading,which greatly reduces the design difficulty of the testing machine.At present,this method has been included in CCS Product Inspection Guide(2015 edition).2.The overall layout scheme of an innovative T-type horizontal testing machine is designed.This scheme can realize the arbitrary switching of plane 90° loading for the multi-part combination strength test and linear loading for the single part strength test,and has the advantages of good versatility and convenience.Aiming at the problem of high construction cost and poor rigidity of the super large testing machine,a horizontal fuselage structure composed of steel structure-concrete is put forward creatively,and the deformation coordination problem of the two materials is successfully solved.The analysis show that compared with the existing horizontal fuselage structure,the T-type horizontal scheme has the advantages of high reliability and low construction cost.3.Combined with the characteristics of dispersion of controlled objects and large difference of control logic in different tests,a distributed control system is designed,which effectively improve the reliability and flexibility of the control system.Aiming at the characteristics of long test and preparation period and high energy consumption of the testing system,a dual-pump dual-valve parallel hydraulic loading system scheme is proposed innovatively.The simulation and application results show that compared with the existing hydraulic loading system,the scheme has significant advantages in control accuracy,energy consumption and construction cost.4.In view of the large difference in stiffness of each component of the ETA,a mathematical model of valve controlled asymmetric hydraulic cylinder under forward and reverse force loading is established,and the influence of the load stiffness on the dynamic characteristics of the force control system is analyzed.The results show that the characteristic parameters such as natural frequency,load damping and equivalent resistance damping,rising time and maximum overshoot of the force control system will change significantly when the load stiffness changes greatly,resulting in a significant drop in system control performance.5.In order to restrain the change of the load stiffness on the control performance and to improve the control quality of the force control system,the model reference adaptive control system is designed,and the adaptive control law is deduced when the relative order of the transfer function is one.In order to construct a reference model with specific performance more accurately and quickly,two kinds of reference model construction methods such as zero-pole method and frequency response method are put forward,and the concrete structural examples are given and the comparative analysis is made on the structural effect and the suitable condition of the two examples.6.The load stiffness adaptive controller is designed according to the design goal of force control system of ideal electro-hydraulic servo testing machine and the reference model with minimum beat response characteristic is constructed by the frequency response method.Results show that the designed controller can better track the output of reference model under different load stiffness,and the control precision of the system is greatly improved compared with the PID algorithm.7.In order to solve the problems of complicated test process,difficult to program the test scripting and error-prone of the ETA strength test,considering the routing logic relationship between each test activity and the influence of the change of the system test resources on the test flow,a novel model based on resource constraint is proposed creatively and the verification algorithm of test workflow is constructed;the framework of the test system is further constructed,and the prototype test system is developed and successfully applied to the developed strength testing system of ETA.The results show that the developed test system can not only describe and verify various complicated test flow effectively,but also can improve the test efficiency of the ETA and avoid errors in effect.