In this paper,an efficient skill learning framework is proposed for robotic insertion,based on one-shot demonstration and reinforcement learning.First,the robot action is composed of two parts:expert action and refine...In this paper,an efficient skill learning framework is proposed for robotic insertion,based on one-shot demonstration and reinforcement learning.First,the robot action is composed of two parts:expert action and refinement action.A force Jacobian matrix is calibrated with only one demonstration,based on which stable and safe expert action can be generated.The deep deterministic policy gradients(DDPG)method is employed to learn the refinement action,which aims to improve the assembly efficiency.Second,an episode-step exploration strategy is developed,which uses the expert action as a benchmark and adjusts the exploration intensity dynamically.A safety-efficiency reward function is designed for the compliant insertion.Third,to improve the adaptability with different components,a skill saving and selection mechanism is proposed.Several typical components are used to train the skill models.And the trained models and force Jacobian matrices are saved in a skill pool.Given a new component,the most appropriate model is selected from the skill pool according to the force Jacobian matrix and directly used to accomplish insertion tasks.Fourth,a simulation environment is established under the guidance of the force Jacobian matrix,which avoids tedious training process on real robotic systems.Simulation and experiments are conducted to validate the effectiveness of the proposed methods.展开更多
The high-order harmonic generation(HHG)in solids permits the exploration of the ultrafast electron dynamics in strong-field light–matter interaction.In particular,the laser ellipticity dependence of HHG provides insi...The high-order harmonic generation(HHG)in solids permits the exploration of the ultrafast electron dynamics in strong-field light–matter interaction.In particular,the laser ellipticity dependence of HHG provides insight into the energy band structure and the electron dynamics.Here,we report the harmonics up to the 10th order generated from monolayer MoS2in experiment.The perpendicular components of even harmonics display unreported enhanced yield at a finite ellipticity,which is sensitive to the crystal orientations.The abnormal ellipticity dependence indicates a novel mechanism that the Berry curvature distributed in a two-dimensional structure manipulates the subcycle electron dynamics during harmonics generation.So far,the research of the BC is limited to the theoretical configuration or one-dimensional experimental measurement,lacking a comprehensive characterization of the BC in the whole Brillouin zone.Our experiment provides a potential experimental scheme to characterize the complex BC structure in two-or three-dimensional materials and a new way to control the subcycle electron dynamics based on the Berry curvature field.展开更多
Recent advancements in high-energy terahertz(THz)sources,driven by powerful laser systems,now enable the generation of ultrashort THz pulses with energies up to several millijoules,spanning frequencies from 1 to 30 TH...Recent advancements in high-energy terahertz(THz)sources,driven by powerful laser systems,now enable the generation of ultrashort THz pulses with energies up to several millijoules,spanning frequencies from 1 to 30 THz.A key breakthrough is developing a reliable single-shot detection method,essential for measuring the electric field of these broadband,low-repetition-rate pulses,which is vital for exploring the complex dynamics of THz emission and studying extreme nonlinear material responses in this range.Existing detection methods have been limited to lower frequencies.Here,we introduce the first potentially single-shot-capable THz detection technique for capturing ultra-broadband waveforms.Utilizing a 1-μm-thick SiN detection chip,we exploit THz field-induced second harmonic generation to achieve real-time monitoring of THz waveforms with frequency content up to 30 THz.By adjusting the angle between the THz and optical probe beams,we can fine-tune the detection window for enhanced flexibility.Our novel THz detector is ideally suited for high-energy,low-repetition-rate sources,unlocking new frontiers in THz research.展开更多
基金supported by National Key Research and Development Program of China(No.2018AAA0103005)National Natural Science Foundation of China(No.61873266)。
文摘In this paper,an efficient skill learning framework is proposed for robotic insertion,based on one-shot demonstration and reinforcement learning.First,the robot action is composed of two parts:expert action and refinement action.A force Jacobian matrix is calibrated with only one demonstration,based on which stable and safe expert action can be generated.The deep deterministic policy gradients(DDPG)method is employed to learn the refinement action,which aims to improve the assembly efficiency.Second,an episode-step exploration strategy is developed,which uses the expert action as a benchmark and adjusts the exploration intensity dynamically.A safety-efficiency reward function is designed for the compliant insertion.Third,to improve the adaptability with different components,a skill saving and selection mechanism is proposed.Several typical components are used to train the skill models.And the trained models and force Jacobian matrices are saved in a skill pool.Given a new component,the most appropriate model is selected from the skill pool according to the force Jacobian matrix and directly used to accomplish insertion tasks.Fourth,a simulation environment is established under the guidance of the force Jacobian matrix,which avoids tedious training process on real robotic systems.Simulation and experiments are conducted to validate the effectiveness of the proposed methods.
基金Zhangjiang LaboratoryNational Natural Science Foundation of China(91950203,11874374)。
文摘The high-order harmonic generation(HHG)in solids permits the exploration of the ultrafast electron dynamics in strong-field light–matter interaction.In particular,the laser ellipticity dependence of HHG provides insight into the energy band structure and the electron dynamics.Here,we report the harmonics up to the 10th order generated from monolayer MoS2in experiment.The perpendicular components of even harmonics display unreported enhanced yield at a finite ellipticity,which is sensitive to the crystal orientations.The abnormal ellipticity dependence indicates a novel mechanism that the Berry curvature distributed in a two-dimensional structure manipulates the subcycle electron dynamics during harmonics generation.So far,the research of the BC is limited to the theoretical configuration or one-dimensional experimental measurement,lacking a comprehensive characterization of the BC in the whole Brillouin zone.Our experiment provides a potential experimental scheme to characterize the complex BC structure in two-or three-dimensional materials and a new way to control the subcycle electron dynamics based on the Berry curvature field.
基金supported by the Independent Research Fund Denmark(project THz-GRIP:2035-00365B).
文摘Recent advancements in high-energy terahertz(THz)sources,driven by powerful laser systems,now enable the generation of ultrashort THz pulses with energies up to several millijoules,spanning frequencies from 1 to 30 THz.A key breakthrough is developing a reliable single-shot detection method,essential for measuring the electric field of these broadband,low-repetition-rate pulses,which is vital for exploring the complex dynamics of THz emission and studying extreme nonlinear material responses in this range.Existing detection methods have been limited to lower frequencies.Here,we introduce the first potentially single-shot-capable THz detection technique for capturing ultra-broadband waveforms.Utilizing a 1-μm-thick SiN detection chip,we exploit THz field-induced second harmonic generation to achieve real-time monitoring of THz waveforms with frequency content up to 30 THz.By adjusting the angle between the THz and optical probe beams,we can fine-tune the detection window for enhanced flexibility.Our novel THz detector is ideally suited for high-energy,low-repetition-rate sources,unlocking new frontiers in THz research.
