A joint industry project on a full scale measurement of Fenjin FPSO,headed by Shanghai Jiao Tong University and sponsored by CNOOC,was initiated in October 2007 and has been going on for more than 25 months.The purpos...A joint industry project on a full scale measurement of Fenjin FPSO,headed by Shanghai Jiao Tong University and sponsored by CNOOC,was initiated in October 2007 and has been going on for more than 25 months.The purpose of the project is to measure and collect the motions in six-degrees of freedom of an FPSO,and to collect the environmental loads at the offshore oil-field.A motion data measuring system is designed and installed on the FPSO.Another environmental data measuring system is installed on a fixed jacket platform nearby.A large quantity of valuable first-hand data is obtained.With the data collected,motion characteristics of the FPSO in a long-term period are concluded.A short-term analysis for the FPSO in one of the typhoons is also completed.The mean periods of wave-frequency motions are calculated by the spectrum analysis.The tension loads of the mooring system,which is of great concern,are calculated by the decoupled technique.展开更多
The objective of this article is to make a contribution relating to the modeling, control, simulation and stabilization of a complex system, with six degrees of freedom of a particular drone which presents many advant...The objective of this article is to make a contribution relating to the modeling, control, simulation and stabilization of a complex system, with six degrees of freedom of a particular drone which presents many advantages and challenges. On the technological, military, political and other levels with an enormous and beneficial social contribution</span><span style="font-family:Verdana;">, </span><span style="font-family:Verdana;">it is a quadrotor which is a nonlinear, strongly coupled and unstable system. Such a structure is difficult to master</span><span style="font-family:Verdana;">, </span><span style="font-family:Verdana;">because the control is multivariable in the sense that six degrees of freedom are to be controlled simultaneously and operating in an environment subject to disturbances. Two commands, in particular Backstepping and </span><span style="font-family:Verdana;"></span><span style="font-family:Verdana;">PID, will be applied to obtain the stabilization of the quadcopter at the desired values, in attitude and in altitude. This article presents the comparative results of the performance of the quadcopter under the two controls. The effect of the parameters of each command on the response time of the system is elucidated under the Matlab/Simulink environment. For a simulation time of up to 10 seconds minimum with a less good response time of almost 2 seconds for the PID control</span><span style="font-family:Verdana;">, </span><span style="font-family:Verdana;">these results prove the robustness of the Backstepping command.展开更多
In most of the emergency circumstances,the aircrew leaves the aircraft under unsatisfied conditions,such as too high relative velocity to the ambient air or low partial oxygen pressure.The aircrew must pass through th...In most of the emergency circumstances,the aircrew leaves the aircraft under unsatisfied conditions,such as too high relative velocity to the ambient air or low partial oxygen pressure.The aircrew must pass through this area as quickly as possible before opening the parachute safely,viz.,free-fall.Numerical simulations are conducted in this paper to explore the major characteris-tics of the aircrew free-fall process by using a commercial computational fluid dynamic（CFD） software,FLUENT.Coupled with the classical pressure-altitude and temperature-altitude relations,Navier-Stokes（N-S） equations for compressible flow are solved by using finite volume method.The body velocity and the attitude are predicted with six-degree of freedom（6DOF） module.The evolution of velocities,including horizontal,vertical components and angular velocity,is obtained.It is also analyzed further according to the particle kinetic theories.It is validated that the theories can predict the process qualitatively well with a modi-fied drag effect,which mainly stems from the velocity pressure.An empirical modification factor is proposed according to the fitting results.展开更多
基金supported by the National Scientific and Technology Major Project (Grant No.2008ZX05026-006)
文摘A joint industry project on a full scale measurement of Fenjin FPSO,headed by Shanghai Jiao Tong University and sponsored by CNOOC,was initiated in October 2007 and has been going on for more than 25 months.The purpose of the project is to measure and collect the motions in six-degrees of freedom of an FPSO,and to collect the environmental loads at the offshore oil-field.A motion data measuring system is designed and installed on the FPSO.Another environmental data measuring system is installed on a fixed jacket platform nearby.A large quantity of valuable first-hand data is obtained.With the data collected,motion characteristics of the FPSO in a long-term period are concluded.A short-term analysis for the FPSO in one of the typhoons is also completed.The mean periods of wave-frequency motions are calculated by the spectrum analysis.The tension loads of the mooring system,which is of great concern,are calculated by the decoupled technique.
文摘The objective of this article is to make a contribution relating to the modeling, control, simulation and stabilization of a complex system, with six degrees of freedom of a particular drone which presents many advantages and challenges. On the technological, military, political and other levels with an enormous and beneficial social contribution</span><span style="font-family:Verdana;">, </span><span style="font-family:Verdana;">it is a quadrotor which is a nonlinear, strongly coupled and unstable system. Such a structure is difficult to master</span><span style="font-family:Verdana;">, </span><span style="font-family:Verdana;">because the control is multivariable in the sense that six degrees of freedom are to be controlled simultaneously and operating in an environment subject to disturbances. Two commands, in particular Backstepping and </span><span style="font-family:Verdana;"></span><span style="font-family:Verdana;">PID, will be applied to obtain the stabilization of the quadcopter at the desired values, in attitude and in altitude. This article presents the comparative results of the performance of the quadcopter under the two controls. The effect of the parameters of each command on the response time of the system is elucidated under the Matlab/Simulink environment. For a simulation time of up to 10 seconds minimum with a less good response time of almost 2 seconds for the PID control</span><span style="font-family:Verdana;">, </span><span style="font-family:Verdana;">these results prove the robustness of the Backstepping command.
基金University Foundation for Fundamental Research of NWPU
文摘In most of the emergency circumstances,the aircrew leaves the aircraft under unsatisfied conditions,such as too high relative velocity to the ambient air or low partial oxygen pressure.The aircrew must pass through this area as quickly as possible before opening the parachute safely,viz.,free-fall.Numerical simulations are conducted in this paper to explore the major characteris-tics of the aircrew free-fall process by using a commercial computational fluid dynamic（CFD） software,FLUENT.Coupled with the classical pressure-altitude and temperature-altitude relations,Navier-Stokes（N-S） equations for compressible flow are solved by using finite volume method.The body velocity and the attitude are predicted with six-degree of freedom（6DOF） module.The evolution of velocities,including horizontal,vertical components and angular velocity,is obtained.It is also analyzed further according to the particle kinetic theories.It is validated that the theories can predict the process qualitatively well with a modi-fied drag effect,which mainly stems from the velocity pressure.An empirical modification factor is proposed according to the fitting results.
