To improve the mechanical properties of the parts fabricated by Laser Direct Metal Shaping(LDMS),it is of great significance to understand the distribution regularities of transient temperature field during LDMS proce...To improve the mechanical properties of the parts fabricated by Laser Direct Metal Shaping(LDMS),it is of great significance to understand the distribution regularities of transient temperature field during LDMS process.Based on the“el-ement birth and death”technique of finite element method,a three-dimensional multi-track and multi-layer model for the transient temperature field analysis of LDMS is developed by ANSYS Parametric Design Language(APDL)for the first time.In the fab-ricated modal,X-direction parallel reciprocating scanning paths is introduced.Using the same process parameters,the simulation results show good agreement with the microstructure features of samples which fabricated by LDMS.展开更多
To decrease thermal stress during laser metal deposition shaping(LMDS)process,it is of great importance to learn the transient thermal stress distribution regularities.Based on the“element life and death”technique o...To decrease thermal stress during laser metal deposition shaping(LMDS)process,it is of great importance to learn the transient thermal stress distribution regularities.Based on the“element life and death”technique of finite element analy-sis(FEA),a three-dimensional multi-track and multi-layer numerical simulation model for LMDS is developed with ANSYS parametric design language(APDL)for the first time,in which long-edge parallel reciprocating scanning paths is introduced.Through the model,detailed simulations of thermal stress during whole metal cladding process are conducted,the generation and distribution regularities of thermal stress are also discussed in detail.Using the same process parameters,the simulation results show good agreement with the features of samples which fabricated by LMDS.展开更多
Future humanoid robots must be reactive and dexterous when operating in dynamic,human-centered environments.To address the challenges of task-space constrained manipulation and reactive motion planning resulting in lo...Future humanoid robots must be reactive and dexterous when operating in dynamic,human-centered environments.To address the challenges of task-space constrained manipulation and reactive motion planning resulting in locally optimal robot motion in complex unstructured environments,we propose a general framework for humanoid upper-body robots(HUBRs),which enables three distinct reactive motion modes,to fill the research gap about unifying tightly coupled coordinated bimanual manipulation,reactive motion,and overcoming the local minima of reactive motion planning:(1)Tightly coupled coordinated bimanual reactive collision-free motion for any type of obstacles,which is achieved by vector field(VF),cooperative dual task space(CDTS),and our proposed safety filter based on control barrier function(CBF).(2)The robot arms proactively escape from the local minima induced by concave obstacles and reactive motion via the proposed local VF modulation strategy that incorporates the novel force navigation kernel and the kernel parameter optimization based on sampling-based model predictive control(MPPI).This motion mode is automatically activated by evaluating an efficient scalar-valued activation function.(3)Reactive coordinated waist-arm motion based on the dual-arm reachability analysis for dual-arm workspace expansion.This motion mode is triggered when dual-arm manipulability or the tilt angle of the dual-arm end-effectors reach the threshold value.Various planning methods are thoroughly validated in cluttered and dynamic simulation scenarios.The proposed framework outperforms existing solutions in constrained manipulation tasks.We also demonstrate the benefits of the proposed framework in real-world experiments.展开更多
文摘To improve the mechanical properties of the parts fabricated by Laser Direct Metal Shaping(LDMS),it is of great significance to understand the distribution regularities of transient temperature field during LDMS process.Based on the“el-ement birth and death”technique of finite element method,a three-dimensional multi-track and multi-layer model for the transient temperature field analysis of LDMS is developed by ANSYS Parametric Design Language(APDL)for the first time.In the fab-ricated modal,X-direction parallel reciprocating scanning paths is introduced.Using the same process parameters,the simulation results show good agreement with the microstructure features of samples which fabricated by LDMS.
文摘To decrease thermal stress during laser metal deposition shaping(LMDS)process,it is of great importance to learn the transient thermal stress distribution regularities.Based on the“element life and death”technique of finite element analy-sis(FEA),a three-dimensional multi-track and multi-layer numerical simulation model for LMDS is developed with ANSYS parametric design language(APDL)for the first time,in which long-edge parallel reciprocating scanning paths is introduced.Through the model,detailed simulations of thermal stress during whole metal cladding process are conducted,the generation and distribution regularities of thermal stress are also discussed in detail.Using the same process parameters,the simulation results show good agreement with the features of samples which fabricated by LMDS.
基金supported by the National Natural Science Foundation of China(Grant Nos.T2388101,51875114)the Fundamental Research Funds for the Central Universities(Grant No.HIT-XTCX-4)the Self-Planned Task of State Key Laboratory of Robotics and System(HIT)(Grant No.SKLRS202204B)。
文摘Future humanoid robots must be reactive and dexterous when operating in dynamic,human-centered environments.To address the challenges of task-space constrained manipulation and reactive motion planning resulting in locally optimal robot motion in complex unstructured environments,we propose a general framework for humanoid upper-body robots(HUBRs),which enables three distinct reactive motion modes,to fill the research gap about unifying tightly coupled coordinated bimanual manipulation,reactive motion,and overcoming the local minima of reactive motion planning:(1)Tightly coupled coordinated bimanual reactive collision-free motion for any type of obstacles,which is achieved by vector field(VF),cooperative dual task space(CDTS),and our proposed safety filter based on control barrier function(CBF).(2)The robot arms proactively escape from the local minima induced by concave obstacles and reactive motion via the proposed local VF modulation strategy that incorporates the novel force navigation kernel and the kernel parameter optimization based on sampling-based model predictive control(MPPI).This motion mode is automatically activated by evaluating an efficient scalar-valued activation function.(3)Reactive coordinated waist-arm motion based on the dual-arm reachability analysis for dual-arm workspace expansion.This motion mode is triggered when dual-arm manipulability or the tilt angle of the dual-arm end-effectors reach the threshold value.Various planning methods are thoroughly validated in cluttered and dynamic simulation scenarios.The proposed framework outperforms existing solutions in constrained manipulation tasks.We also demonstrate the benefits of the proposed framework in real-world experiments.
