Evolutionary Computation(EC)has strengths in terms of computation for gait optimization.However,conventional evolutionary algorithms use typical gait parameters such as step length and swing height,which limit the tra...Evolutionary Computation(EC)has strengths in terms of computation for gait optimization.However,conventional evolutionary algorithms use typical gait parameters such as step length and swing height,which limit the trajectory deformation for optimization of the foot trajectory.Furthermore,the quantitative index of fitness convergence is insufficient.In this paper,we perform gait optimization of a quadruped robot using foot placement perturbation based on EC.The proposed algorithm has an atypical solution search range,which is generated by independent manipulation of each placement that forms the foot trajectory.A convergence index is also introduced to prevent premature cessation of learning.The conventional algorithm and the proposed algorithm are applied to a quadruped robot;walking performances are then compared by gait simulation.Although the two algorithms exhibit similar computation rates,the proposed algorithm shows better fitness and a wider search range.The evolutionary tendency of the walking trajectory is analyzed using the optimized results,and the findings provide insight into reliable leg trajectory design.展开更多
The added resistance of a ship in waves can be related to ship-generated unsteady waves.In the present study,the unsteady wave-pattern analysis is applied to calculate the added resistance in waves for two modified Wi...The added resistance of a ship in waves can be related to ship-generated unsteady waves.In the present study,the unsteady wave-pattern analysis is applied to calculate the added resistance in waves for two modified Wigley models using a Cartesian-grid method.In the present numerical method,a first-order fractional-step method is applied to the velocity-pressure coupling in the fluid domain,and one of volume-of-fluid(VOF)methods is adopted to capture the fluid interface.A ship is embedded in a Cartesian grid,and the volume fraction of the ship inside the grid is calculated by identifying whether each grid is occupied by liquid,gas,and solid body.The sensitivity to the location of measuring position of unsteady waves as well as the number of solution grids is examined.The added resistance computed by direct pressure integration and wave pattern analysis is compared with experimental data.In addition,nonlinear characteristics of the added resistance in waves are investigated by detailed analyses of unsteady flow field and resulting wave pattern.展开更多
基金This work was supported in part by the National Research Foundation of Korea(NRF)Grant funded by the Korean Government(MSIT)(No.NRF-2019R1A2C2084677)the 2021 Research Fund(1.210052.01)of UNIST(Ulsan National Institute of Science and Technology).
文摘Evolutionary Computation(EC)has strengths in terms of computation for gait optimization.However,conventional evolutionary algorithms use typical gait parameters such as step length and swing height,which limit the trajectory deformation for optimization of the foot trajectory.Furthermore,the quantitative index of fitness convergence is insufficient.In this paper,we perform gait optimization of a quadruped robot using foot placement perturbation based on EC.The proposed algorithm has an atypical solution search range,which is generated by independent manipulation of each placement that forms the foot trajectory.A convergence index is also introduced to prevent premature cessation of learning.The conventional algorithm and the proposed algorithm are applied to a quadruped robot;walking performances are then compared by gait simulation.Although the two algorithms exhibit similar computation rates,the proposed algorithm shows better fitness and a wider search range.The evolutionary tendency of the walking trajectory is analyzed using the optimized results,and the findings provide insight into reliable leg trajectory design.
基金the research in the promotion program for international collaboration supported by Osaka Universitysupported by the Ministry of Trade,Industry and Energy(MOTIE),Korea,through the project“Technology Development to Improve Added Resistance and Ship Operational Efficiency for Hull Form Design”(Grant No.10062881)+1 种基金the Lloyd’s Register Foundation(LRF)-Funded Research Center at Seoul National UniversityAdministrative support was also received from RIMSE and ERI at the Seoul National University.
文摘The added resistance of a ship in waves can be related to ship-generated unsteady waves.In the present study,the unsteady wave-pattern analysis is applied to calculate the added resistance in waves for two modified Wigley models using a Cartesian-grid method.In the present numerical method,a first-order fractional-step method is applied to the velocity-pressure coupling in the fluid domain,and one of volume-of-fluid(VOF)methods is adopted to capture the fluid interface.A ship is embedded in a Cartesian grid,and the volume fraction of the ship inside the grid is calculated by identifying whether each grid is occupied by liquid,gas,and solid body.The sensitivity to the location of measuring position of unsteady waves as well as the number of solution grids is examined.The added resistance computed by direct pressure integration and wave pattern analysis is compared with experimental data.In addition,nonlinear characteristics of the added resistance in waves are investigated by detailed analyses of unsteady flow field and resulting wave pattern.
