Based on the dynamical theory of multi-body systems with nonholonomic constraints and an algorithm for complementarity problems, a numerical method for the multi-body systems with two-dimensional Coulomb dry friction ...Based on the dynamical theory of multi-body systems with nonholonomic constraints and an algorithm for complementarity problems, a numerical method for the multi-body systems with two-dimensional Coulomb dry friction and nonholonomic constraints is presented. In particular, a wheeled multi-body system is considered. Here, the state transition of stick-slip between wheel and ground is transformed into a nonlinear complementarity problem （NCP）. An iterative algorithm for solving the NCP is then presented using an event-driven method. Dynamical equations of the multi-body system with holonomic and nonholonomic constraints are given using Routh equations and a con- straint stabilization method. Finally, an example is used to test the proposed numerical method. The results show some dynamical behaviors of the wheeled multi-body system and its constraint stabilization effects.展开更多
In surveying adjustment models,there is usually some uncertain additional information or prior information on parameters,which can constrain the parameters,and guarantee the uniqueness and stability of parameter solut...In surveying adjustment models,there is usually some uncertain additional information or prior information on parameters,which can constrain the parameters,and guarantee the uniqueness and stability of parameter solution.In this paper,we firstly use ellipsoidal sets to describe uncertainty,and establish a new adjustment model with ellipsoidal uncertainty.Furthermore,we give a new adjustment criterion based on minimization trace of an outer ellipsoid with two ellipsoid intersections,and analyze the propagation law of uncertainty.Correspondingly,we give a new algorithm for the adjustment model with ellipsoid uncertainty.Finally,we give three examples to test and verify the effectiveness of our algorithm,and illustrate the relation between our result and the weighted mixed estimation.展开更多
In density-based topological design, one expects that the final result consists of elements either black （solid material） or white （void）, without any grey areas. Moreover, one also expects that the optimal topolo...In density-based topological design, one expects that the final result consists of elements either black （solid material） or white （void）, without any grey areas. Moreover, one also expects that the optimal topology can be obtained by starting from any initial topology configuration. An improved structural topological optimization method for multidisplacement constraints is proposed in this paper. In the proposed method, the whole optimization process is divided into two optimization adjustment phases and a phase transferring step. Firstly, an optimization model is built to deal with the varied displacement limits, design space adjustments, and reasonable relations between the element stiffness matrix and mass and its element topology variable. Secondly, a procedure is proposed to solve the optimization problem formulated in the first optimization adjustment phase, by starting with a small design space and advancing to a larger deign space. The design space adjustments are automatic when the design domain needs expansions, in which the convergence of the proposed method will not be affected. The final topology obtained by the proposed procedure in the first optimization phase, can approach to the vicinity of the optimum topology. Then, a heuristic algorithm is given to improve the efficiency and make the designed structural topology black/white in both the phase transferring step and the second optimization adjustment phase. And the optimum topology can finally be obtained by the second phase optimization adjustments. Two examples are presented to show that the topologies obtained by the proposed method are of very good 0/1 design distribution property, and the computational efficiency is enhanced by reducing the element number of the design structural finite model during two optimization adjustment phases. And the examples also show that this method is robust and practicable.展开更多
Background Currently,laser tracker is the primary instrument used to carry out three-dimensional position measurement in accelerator alignment.Theoretically,three-dimensional measuring data processed by three-dimensio...Background Currently,laser tracker is the primary instrument used to carry out three-dimensional position measurement in accelerator alignment.Theoretically,three-dimensional measuring data processed by three-dimensional adjustment are more rigorous,however,error accumulation is found in practice.Purpose In order to control error accumulation and further improve the measurement accuracy of accelerator alignment,this research introduces the laser alignment system into the activity of measurement and data processing.Methods A measurement scheme combining laser tracker and laser alignment system is proposed.To construct the constraint condition,the offset values from the measuring points to the laser straight-line datum were used.To carry out the three-dimensional adjustment with offset constraint,the laser tracker observations were used.Results A three-dimensional adjustment function model of laser tracker observations is given.The construction method of the constraint equation is researched,and the calculation formulas of the three-dimensional adjustment with offset constraint are derived.A 200 m linac tunnel control network is designed,using simulation measurement method,the measuring data of laser tracker and the offset values from the measuring points to the laser straight-line datum were generated.The simulated data are calculated by the method given in this paper and the result is analyzed.Conclusion Simulation result shows introducing the laser alignment system into laser tracker measurement and applying the three-dimensional adjustment with offset constraint can effectively suppress the error accumulation caused by long distance move station measurement.展开更多
基金Project supported by the National Natural Science Foundation of China(Nos.11372018 and 11572018)
文摘Based on the dynamical theory of multi-body systems with nonholonomic constraints and an algorithm for complementarity problems, a numerical method for the multi-body systems with two-dimensional Coulomb dry friction and nonholonomic constraints is presented. In particular, a wheeled multi-body system is considered. Here, the state transition of stick-slip between wheel and ground is transformed into a nonlinear complementarity problem （NCP）. An iterative algorithm for solving the NCP is then presented using an event-driven method. Dynamical equations of the multi-body system with holonomic and nonholonomic constraints are given using Routh equations and a con- straint stabilization method. Finally, an example is used to test the proposed numerical method. The results show some dynamical behaviors of the wheeled multi-body system and its constraint stabilization effects.
基金National Natural Science Foundation of China(Nos.41674009,41574006,41674012)。
文摘In surveying adjustment models,there is usually some uncertain additional information or prior information on parameters,which can constrain the parameters,and guarantee the uniqueness and stability of parameter solution.In this paper,we firstly use ellipsoidal sets to describe uncertainty,and establish a new adjustment model with ellipsoidal uncertainty.Furthermore,we give a new adjustment criterion based on minimization trace of an outer ellipsoid with two ellipsoid intersections,and analyze the propagation law of uncertainty.Correspondingly,we give a new algorithm for the adjustment model with ellipsoid uncertainty.Finally,we give three examples to test and verify the effectiveness of our algorithm,and illustrate the relation between our result and the weighted mixed estimation.
基金supported by the National Natural Science Foundation of China (10872036)the High Technological Research and Development Program of China (2008AA04Z118)the Airspace Natural Science Foundation (2007ZA23007)
文摘In density-based topological design, one expects that the final result consists of elements either black （solid material） or white （void）, without any grey areas. Moreover, one also expects that the optimal topology can be obtained by starting from any initial topology configuration. An improved structural topological optimization method for multidisplacement constraints is proposed in this paper. In the proposed method, the whole optimization process is divided into two optimization adjustment phases and a phase transferring step. Firstly, an optimization model is built to deal with the varied displacement limits, design space adjustments, and reasonable relations between the element stiffness matrix and mass and its element topology variable. Secondly, a procedure is proposed to solve the optimization problem formulated in the first optimization adjustment phase, by starting with a small design space and advancing to a larger deign space. The design space adjustments are automatic when the design domain needs expansions, in which the convergence of the proposed method will not be affected. The final topology obtained by the proposed procedure in the first optimization phase, can approach to the vicinity of the optimum topology. Then, a heuristic algorithm is given to improve the efficiency and make the designed structural topology black/white in both the phase transferring step and the second optimization adjustment phase. And the optimum topology can finally be obtained by the second phase optimization adjustments. Two examples are presented to show that the topologies obtained by the proposed method are of very good 0/1 design distribution property, and the computational efficiency is enhanced by reducing the element number of the design structural finite model during two optimization adjustment phases. And the examples also show that this method is robust and practicable.
基金Funding was provided by Young Scientists Fund(Grant no.12075264).
文摘Background Currently,laser tracker is the primary instrument used to carry out three-dimensional position measurement in accelerator alignment.Theoretically,three-dimensional measuring data processed by three-dimensional adjustment are more rigorous,however,error accumulation is found in practice.Purpose In order to control error accumulation and further improve the measurement accuracy of accelerator alignment,this research introduces the laser alignment system into the activity of measurement and data processing.Methods A measurement scheme combining laser tracker and laser alignment system is proposed.To construct the constraint condition,the offset values from the measuring points to the laser straight-line datum were used.To carry out the three-dimensional adjustment with offset constraint,the laser tracker observations were used.Results A three-dimensional adjustment function model of laser tracker observations is given.The construction method of the constraint equation is researched,and the calculation formulas of the three-dimensional adjustment with offset constraint are derived.A 200 m linac tunnel control network is designed,using simulation measurement method,the measuring data of laser tracker and the offset values from the measuring points to the laser straight-line datum were generated.The simulated data are calculated by the method given in this paper and the result is analyzed.Conclusion Simulation result shows introducing the laser alignment system into laser tracker measurement and applying the three-dimensional adjustment with offset constraint can effectively suppress the error accumulation caused by long distance move station measurement.
