Natural frequencies and modal shapes of machine tools have position-dependent characteristics owing to their dynamic behaviors changing with the positions of moving parts. It is time-consuming and difficult to evaluat...
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Natural frequencies and modal shapes of machine tools have position-dependent characteristics owing to their dynamic behaviors changing with the positions of moving parts. It is time-consuming and difficult to evaluate the dynamic behaviors of machine tools and their machining accuracy at different positions. In this paper, a Kriging approximation model coupled with finite element method is proposed to substitute the dynamic equations for obtaining the position-dependent natural frequencies of a machine tool, as well as relative positions between the tool and the workpiece during the machining process. Based on the proposed method, dynamic performance optimization design of the machine tool is conducted under the condition of minimum relative positions. Three case studies are illustrated to demonstrate the implementation of the proposed method.
With the high ratio distributed photovoltaics (PVs) penetration to the distribution network (DN), the bearing capacity, integration capacity, consuming capacity and controlling capacity of DN for PVs are all facing gr...
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With the high ratio distributed photovoltaics (PVs) penetration to the distribution network (DN), the bearing capacity, integration capacity, consuming capacity and controlling capacity of DN for PVs are all facing great challenges. Enhancing the flexible regulation and operation optimization capabilities of DN have become key factors to satisfy these new challenges. For the operation optimization problem of high ratio PVs penetration, a novel quasi-equal curtailment ratio (QCR) constraint of PVs is proposed in the dynamic optimization method for DN operation. Firstly, the uncertainty of high ratio PVs and their active power deviations are discussed. And a dynamicoptimization framework of PVs based on optimal power flow (OPF) has been proposed. Secondly, the optimization model for high ratio PVs is formulated with multi-objective of maximum PVs output, minimum voltage deviation and minimum line loss, under the equality and inequality constraints of power flow, PVs power generation limit, QCR of PVs and so on. Then the multi-objective optimization problem (MOP) is transformed into a single-objective optimization problem (SOP) by weighting coefficients, and solved by sequential quadratic programming (SQP) with trust-region (TR) searching algorithm. Finally, the proposed method is tested, verified and compared with the primal dual interior point (PDIP) and traditional SQP algorithms in IEEE 33-bus, PG&E 69-bus, 292-bus and 1180-bus test cases. The experimental results show the rapidity and robustness of the proposed method.
The rapid increase in the ownership of private vehicles has exacerbated social and environmental problems, such as traffic congestion and exhaust emissions, and carsharing services are regarded as an effective method ...
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The rapid increase in the ownership of private vehicles has exacerbated social and environmental problems, such as traffic congestion and exhaust emissions, and carsharing services are regarded as an effective method for solving these problems. In a one-way carsharing system, customer demand is highly variable, and the volume of demand in different locations changes continuously. As a result, the facility planning for a one-way carsharing system is a difficult issue for the managers. In this study, a dynamic optimization method based on a mixed integer programming model is proposed to solve this issue. In the model, various costs, such as station construction, parking space operation, vehicle maintenance, and vehicle rescheduling, are considered, and the objective of optimization is to maximize the profits of the operators. To solve the proposed model, an adaptive Jaya algorithm is proposed. Finally, the case of Vancouver, Canada, is used to verify the effectiveness of the proposed model, and the experimental results show that compared with those of the traditional single-period static planning method, the dynamic planning method proposed in this study can increase the average revenue of the operators by 10.8% and the average customer service rate by 2.95%.
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