PERT (Program Evaluation and Review Technique) is suitable for evaluating schedule optimization of DBB (Design-Bid-Build) projects based on serial execution of design and construction. However, it is not suitable for ...
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PERT (Program Evaluation and Review Technique) is suitable for evaluating schedule optimization of DBB (Design-Bid-Build) projects based on serial execution of design and construction. However, it is not suitable for evaluating the multi-objective joint optimization of DB (Design-Build) projects based on concurrent execution of design and construction. Therefore, focusing on the unique construction method and construction objective under DB mode, this study adopts the multi-parameter grey GERT (Graphical Evaluation and Review Technique) based on z-tag to construct a multi-objective joint optimization model of concurrent execution of designconstruction tasks. The research methods adopted are as follows: Firstly, based on the modeling idea of PERT, a multi-parameter grey GERT was constructed, which was composed of sub-GERTs representing the execution flow of design-construction tasks. Second, based on discussing the functional relationship between time, cost and quality in normal execution and rework execution, a method of constructing a moment generating function for concurrent execution time, cost and quality to characterize the uncertainty of input and output parameters is proposed. Thirdly, on the basis of analyzing the solving methods of each parameter of the multi-parameter GERT, the solving methods for starting execution time, information transmission duration, and total execution duration of the critical time nodes are given. Finally, according to the requirements of DB projects, the multi-objective joint optimization models based on progress oriented and quality oriented are constructed respectively, and the gamultiobj algorithm is used to solve the models. The proposed approach provides a scientific quantitative analysis method for evaluating the progress, cost and quality objectives of the concurrent execution of designconstruction tasks, and also lays theoretical guidance for further efficiency popularization of DB mode.
To improve the speed of a quadruped robot, a novel electric-drive robot leg based on a double four-bar mechanism is proposed. This scheme avoids the need for constant alternation between the acceleration and decelerat...
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To improve the speed of a quadruped robot, a novel electric-drive robot leg based on a double four-bar mechanism is proposed. This scheme avoids the need for constant alternation between the acceleration and deceleration of the motors and may thus achieve a higher rotation speed. However, the dimensional parameters of the double four-bar mechanism have a significant impact on the dynamic performance of the robot. To determine the optimal dimensions, a kinematic and dynamic analysis of the proposed robot leg is carried out, and the functional relations between the joint motors peak torque, peak angular velocity and total energy consumption in a single gait cycle and the dimensional parameters are determined. In this way, a multi-objective optimization model for the leg design is constructed, and the gamultiobj algorithm is applied to obtain the Pareto optimal solution set of the optimization model. By determining the weight of each objective function based on a combination weighting method, the optimal dimensions of the leg are obtained from the Pareto optimal solution. Finally, a virtual prototype of the robot leg is built via ADAMS to conduct a walking simulation, and the physical prototype is installed on a self-developed test bench of one-legged movement to conduct a no-load walking experiment. The results of the theoretical calculations and simulation are well coincident with those of the tests, which verify the correctness and validity of the proposed algorithm.
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