Since the joint actuator of the space robot executes the control instructions frequently in the harsh space environment,it is prone to the partial loss of control effectiveness(PLCE)fault.An adaptive fault-tolerant co...Since the joint actuator of the space robot executes the control instructions frequently in the harsh space environment,it is prone to the partial loss of control effectiveness(PLCE)fault.An adaptive fault-tolerant control algorithm is designed for a space robot system with the uncertain parameters and the PLCE actuator faults.The mathematical model of the system is established based on the Lagrange method,and the PLCE actuator fault is described as an effectiveness factor.The lower bound of the effectiveness factors and the upper bound of the uncertain parameters are estimated by an adaptive strategy,and the estimated value is fed back to the control algorithm.Compared with the traditional fault-tolerant algorithms,the proposed algorithm does not need to predetermine the lower bound of the effectiveness factor,hence it is more in line with the actual engineering application.It is proved that the algorithm can guarantee the stability of the closed-loop system based on the Lyapunov function method.The numerical simulation results show that the proposed algorithm can not only compensate for the uncertain parameters,but also can tolerate the PLCE actuator faults effectively,which verifies the effectiveness and superiority of the control scheme.展开更多
传统Voronoi图对大量点集进行Voronoi划分时会产生Voronoi单元格数过多的现象,导致难以适用于地理信息系统、生物医学等诸多领域。为了解决这个问题,提出一种自适应基于密度的聚类算法(Density-Based Spatial Clustering of Application...传统Voronoi图对大量点集进行Voronoi划分时会产生Voronoi单元格数过多的现象,导致难以适用于地理信息系统、生物医学等诸多领域。为了解决这个问题,提出一种自适应基于密度的聚类算法(Density-Based Spatial Clustering of Applications with Noise,DBSCAN)的Voronoi图。阐述了Voronoi单元合并的现象,证明了其发生的充要条件,提出该Voronoi图的生成算法并进行仿真。通过显微镜下嗜中性粒细胞、我国地表火点数据对算法进行验证,结果表明,该算法能够有效解决点集规模较大时,Voronoi图划分过于细致的问题,突破了传统Voronoi图单点对单点的划分形式。此外,该算法拓宽了Voronoi图在图形图像处理、生物医学、地理信息系统等领域的应用。展开更多
A flow mathematical model with multiple horizontal wells considering interference between wells and fractures was established by taking the variable width conductivity fractures as basic flow units.Then a semi-analyti...A flow mathematical model with multiple horizontal wells considering interference between wells and fractures was established by taking the variable width conductivity fractures as basic flow units.Then a semi-analytical approach was proposed to model the production performance of full-life cycle in well pad and to investigate the effect of fracture length,flow capacity,well spacing and fracture spacing on estimated ultimate recovery(EUR).Finally,an integrated workflow is developed to optimize drilling and completion parameters of the horizontal wells by incorporating the productivity prediction and economic evaluation.It is defined as nested optimization which consists of outer-optimization shell(i.e.,economic profit as outer constraint)and inner-optimization shell(i.e.,fracturing scale as inner constraint).The results show that,when the constraint conditions aren’t considered,the performance of the well pad can be improved by increasing contact area between fracture and formation,reducing interference between fractures/wells,balancing inflow and outflow between fracture and formation,but there is no best compromise between drilling and completion parameters.When only the inner constraint condition is considered,there only exists the optimal fracture conductivity and fracture length.When considering both inner and outer constraints,the optimization decisions including fracture conductivity and fracture length,well spacing,fracture spacing are achieved and correlated.When the fracturing scale is small,small well spacing,wide fracture spacing and short fracture should be adopted.When the fracturing scale is large,big well spacing,small fracture spacing and long fracture should be used.展开更多
基金supported by the National Natural Science Foundation of China(11372073,11072061)
文摘Since the joint actuator of the space robot executes the control instructions frequently in the harsh space environment,it is prone to the partial loss of control effectiveness(PLCE)fault.An adaptive fault-tolerant control algorithm is designed for a space robot system with the uncertain parameters and the PLCE actuator faults.The mathematical model of the system is established based on the Lagrange method,and the PLCE actuator fault is described as an effectiveness factor.The lower bound of the effectiveness factors and the upper bound of the uncertain parameters are estimated by an adaptive strategy,and the estimated value is fed back to the control algorithm.Compared with the traditional fault-tolerant algorithms,the proposed algorithm does not need to predetermine the lower bound of the effectiveness factor,hence it is more in line with the actual engineering application.It is proved that the algorithm can guarantee the stability of the closed-loop system based on the Lyapunov function method.The numerical simulation results show that the proposed algorithm can not only compensate for the uncertain parameters,but also can tolerate the PLCE actuator faults effectively,which verifies the effectiveness and superiority of the control scheme.
文摘传统Voronoi图对大量点集进行Voronoi划分时会产生Voronoi单元格数过多的现象,导致难以适用于地理信息系统、生物医学等诸多领域。为了解决这个问题,提出一种自适应基于密度的聚类算法(Density-Based Spatial Clustering of Applications with Noise,DBSCAN)的Voronoi图。阐述了Voronoi单元合并的现象,证明了其发生的充要条件,提出该Voronoi图的生成算法并进行仿真。通过显微镜下嗜中性粒细胞、我国地表火点数据对算法进行验证,结果表明,该算法能够有效解决点集规模较大时,Voronoi图划分过于细致的问题,突破了传统Voronoi图单点对单点的划分形式。此外,该算法拓宽了Voronoi图在图形图像处理、生物医学、地理信息系统等领域的应用。
基金Supported by the China National Science and Technology Major Project(2016ZX05037,2017ZX05063).
文摘A flow mathematical model with multiple horizontal wells considering interference between wells and fractures was established by taking the variable width conductivity fractures as basic flow units.Then a semi-analytical approach was proposed to model the production performance of full-life cycle in well pad and to investigate the effect of fracture length,flow capacity,well spacing and fracture spacing on estimated ultimate recovery(EUR).Finally,an integrated workflow is developed to optimize drilling and completion parameters of the horizontal wells by incorporating the productivity prediction and economic evaluation.It is defined as nested optimization which consists of outer-optimization shell(i.e.,economic profit as outer constraint)and inner-optimization shell(i.e.,fracturing scale as inner constraint).The results show that,when the constraint conditions aren’t considered,the performance of the well pad can be improved by increasing contact area between fracture and formation,reducing interference between fractures/wells,balancing inflow and outflow between fracture and formation,but there is no best compromise between drilling and completion parameters.When only the inner constraint condition is considered,there only exists the optimal fracture conductivity and fracture length.When considering both inner and outer constraints,the optimization decisions including fracture conductivity and fracture length,well spacing,fracture spacing are achieved and correlated.When the fracturing scale is small,small well spacing,wide fracture spacing and short fracture should be adopted.When the fracturing scale is large,big well spacing,small fracture spacing and long fracture should be used.
