在压电陶瓷等效电学模型的基础上,结合外加驱动信号波形分析了基于惯性-摩擦驱动的球基微驱动器在工作过程中金属球产生逆转现象的原因,建立了金属球的转速及位移模型,采用快速放电回路和加速压电陶瓷放电的方法减小金属球的逆转位移及...在压电陶瓷等效电学模型的基础上,结合外加驱动信号波形分析了基于惯性-摩擦驱动的球基微驱动器在工作过程中金属球产生逆转现象的原因,建立了金属球的转速及位移模型,采用快速放电回路和加速压电陶瓷放电的方法减小金属球的逆转位移及振动;利用压电陶瓷管作为微驱动元件,设计了基于惯性-摩擦驱动的球基微驱动器,并采用不同频率的三角波信号对所设计微驱动器进行试验测试.结果表明:驱动信号频率越高,微驱动器的振动现象越明显;当驱动信号频率接近、等于或大于微驱动元件(压电陶瓷管)的固有放电周期时,金属球出现无规律运动,导致微驱动器失效;根据1 H z低频信号时的试验结果与计算所得结果基本吻合,证明了所建立的逆转理论模型的合理性.展开更多
Quantitative damage identification of surrounding rock is important to assess the current condition and residual strength of underground tunnels.In this work,an underground tunnel model with marble-like cementitious m...Quantitative damage identification of surrounding rock is important to assess the current condition and residual strength of underground tunnels.In this work,an underground tunnel model with marble-like cementitious materials was first fabricated using the three-dimensional(3D)printing technique and then loaded to simulate its failure mode in the laboratory.Lead zirconate titanate piezoelectric(PZT)transducers were embedded in the surrounding rock around the tunnel in the process of 3D printing.A 3D monitoring network was formed to locate damage areas and evaluate damage extent during loading.Results show that as the load increased,main cracks firstly appeared above the tunnel roof and below the floor,and then they coalesced into the tunnel boundary.Finally,the tunnel model was broken into several parts.The resonant frequency and the peak of the conductance signature firstly shifted rightwards with loading due to the sealing of microcracks,and then shifted backwards after new cracks appeared.An overall increase in the root-mean-square deviation(RMSD)calculated from conductance signatures of all the PZT transducers was observed as the load(damage)increased.Damage-dependent equivalent stiffness parameters(ESPs)were calculated from the real and imaginary signatures of each PZT at different damage states.Satisfactory agreement between equivalent and experimental ESP values was achieved.Also,the relationship between the change of the ESP and the residual strength was obtained.The method paves the way for damage identification and residual strength estimation of other 3D printed structures in civil engineering.展开更多
This paper presents the development of a coarse-fine dual precision positioning stage to achieve long travel range and high accuracy.The fine stage is arranged in series with a coarse stage.The key in the fine stage d...This paper presents the development of a coarse-fine dual precision positioning stage to achieve long travel range and high accuracy.The fine stage is arranged in series with a coarse stage.The key in the fine stage design is the choice of a toggle mechanism for a tight mechanical loop with high stiffness and compactness.We designed the toggle mechanism for reduction of the displacement to suppress signal noises.The performance of the coarse and fine stages was verified with an optical encoder and capacitive sensor,respectively.The measurement results show that the dual mechanism has a travel range of 1 mm and resolution of 30 nm.展开更多
文摘在压电陶瓷等效电学模型的基础上,结合外加驱动信号波形分析了基于惯性-摩擦驱动的球基微驱动器在工作过程中金属球产生逆转现象的原因,建立了金属球的转速及位移模型,采用快速放电回路和加速压电陶瓷放电的方法减小金属球的逆转位移及振动;利用压电陶瓷管作为微驱动元件,设计了基于惯性-摩擦驱动的球基微驱动器,并采用不同频率的三角波信号对所设计微驱动器进行试验测试.结果表明:驱动信号频率越高,微驱动器的振动现象越明显;当驱动信号频率接近、等于或大于微驱动元件(压电陶瓷管)的固有放电周期时,金属球出现无规律运动,导致微驱动器失效;根据1 H z低频信号时的试验结果与计算所得结果基本吻合,证明了所建立的逆转理论模型的合理性.
基金The study is financially supported by the National Major Research Instrument Development Project of the National Natural Science Foundation of China(Grant No.51627812)the National Natural Science Foundation of China(Grant No.52078181)the Natural Science Foundation of Hebei Province,China(Grant No.E2019202484)。
文摘Quantitative damage identification of surrounding rock is important to assess the current condition and residual strength of underground tunnels.In this work,an underground tunnel model with marble-like cementitious materials was first fabricated using the three-dimensional(3D)printing technique and then loaded to simulate its failure mode in the laboratory.Lead zirconate titanate piezoelectric(PZT)transducers were embedded in the surrounding rock around the tunnel in the process of 3D printing.A 3D monitoring network was formed to locate damage areas and evaluate damage extent during loading.Results show that as the load increased,main cracks firstly appeared above the tunnel roof and below the floor,and then they coalesced into the tunnel boundary.Finally,the tunnel model was broken into several parts.The resonant frequency and the peak of the conductance signature firstly shifted rightwards with loading due to the sealing of microcracks,and then shifted backwards after new cracks appeared.An overall increase in the root-mean-square deviation(RMSD)calculated from conductance signatures of all the PZT transducers was observed as the load(damage)increased.Damage-dependent equivalent stiffness parameters(ESPs)were calculated from the real and imaginary signatures of each PZT at different damage states.Satisfactory agreement between equivalent and experimental ESP values was achieved.Also,the relationship between the change of the ESP and the residual strength was obtained.The method paves the way for damage identification and residual strength estimation of other 3D printed structures in civil engineering.
基金supported by the National Science Council (No.NSC-96-2628-E002-199)
文摘This paper presents the development of a coarse-fine dual precision positioning stage to achieve long travel range and high accuracy.The fine stage is arranged in series with a coarse stage.The key in the fine stage design is the choice of a toggle mechanism for a tight mechanical loop with high stiffness and compactness.We designed the toggle mechanism for reduction of the displacement to suppress signal noises.The performance of the coarse and fine stages was verified with an optical encoder and capacitive sensor,respectively.The measurement results show that the dual mechanism has a travel range of 1 mm and resolution of 30 nm.
