A fast tool servo (FTS) system is developed for the fabrication of non-rotationally symmetric micro-structured surfaces using single-point diamond turning machines.The constructed FTS employs a piezoelectric tube actu...A fast tool servo (FTS) system is developed for the fabrication of non-rotationally symmetric micro-structured surfaces using single-point diamond turning machines.The constructed FTS employs a piezoelectric tube actuator (PZT) to actuate the diamond tool and a capacitive probe as the feedback sensor.To compensate the inherent nonlinear hysteresis behavior of the piezoelectric actuator,Proportional Integral (PI) feedback control is implemented.Besides,a feed-forward control based on a simple feed-forward predictor has been added to achieve better tracking performance.Experimental results indicate that error motions in the performance of the system caused by hysteresis can be reduced greatly and the micro-structured surface is successfully fabricated by implementing the FTS.展开更多
Diamond turning based on a fast tool servo(FTS)is widely used in freeform optics fabrication due to its high accuracy and machining efficiency.As a new trend,recently developed high-frequency and long-stroke FTS units...Diamond turning based on a fast tool servo(FTS)is widely used in freeform optics fabrication due to its high accuracy and machining efficiency.As a new trend,recently developed high-frequency and long-stroke FTS units are independently driven by a separate control system from the machine tool controller.However,the tool path generation strategy for the independently controlled FTS is far from complete.This study aims to establish methods for optimizing tool path for the independent control FTS to reduce form errors in a single step of machining.Different from the conventional integrated FTS control system,where control points are distributed in a spiral pattern,in this study,the tool path for the independent FTS controller is generated by the ring method and the mesh method,respectively.The machined surface profile is predicted by simulation and the parameters for the control point generation are optimized by minimizing the deviation between the predicted and the designed surfaces.To demonstrate the feasibility of the proposed tool path generation strategies,cutting tests of a two-dimensional sinewave and a micro-lens array were conducted and the results were compared.As a result,after tool path optimization,the peak-to-valley form error of the machined surface was reduced from 429 nm to 56 nm for the two-dimensional sinewave by using the ring method,and from 191 nm to 103 nm for the micro-lens array by using the mesh method,respectively.展开更多
The development of the fast tool servo (FTS) for precision machining was investigated.The micron machining performance of a piezoelectric-assisted FTS on copper alloy was evaluated.The results indicate that the qualit...The development of the fast tool servo (FTS) for precision machining was investigated.The micron machining performance of a piezoelectric-assisted FTS on copper alloy was evaluated.The results indicate that the quality of the microstructure depends mainly on two important factors:the cutting speed (or spindle speed) and the driving frequency of the FTS.The excessive driving frequency increases the formation of burrs.The effect of the clearance angle of the diamond tool on the microstructure machining precision was also investigated.展开更多
An experimental study of micro-tool servo with electrostrictive actuator is presented.The design methods as well as the performance of the entire mechanism is given out.The results of the experiment show that the reso...An experimental study of micro-tool servo with electrostrictive actuator is presented.The design methods as well as the performance of the entire mechanism is given out.The results of the experiment show that the resolution of the micro-tool servo is 0.02μm and the frequency response is up to 200Hz,which satisfies the requirements of the ultra-precision machining.展开更多
Ultra-precision diamond machining with piezoelectric-assisted fast tool servo (FTS) was used to produce various free-form surfaces.A low cost,rapid and large area fabrication of uniform hydrophobic surface at room tem...Ultra-precision diamond machining with piezoelectric-assisted fast tool servo (FTS) was used to produce various free-form surfaces.A low cost,rapid and large area fabrication of uniform hydrophobic surface at room temperature which transfers the FTS fabricated sinusoidal grid surface to the flat film with UV-moulding process was described.A piezoelectric-assisted FTS with high band width of 2 kHz,travel range up to 16 μm and the compact mechanism structure was designed for the sinusoidal grid surface machining and the dynamic performance testing of FTS was described in detail.Machining results indicate that the dimensions of sinusoidal grid change with the variation of the FTS machining condition.Wetting properties of UV-moulded surface were evaluated,the best contact angle was measured to be 120.5° on the sinusoidal grid surface with profile wavelength of 350 μm and peak-to-valley amplitude of about 16 μm.展开更多
A lens array is often used for optical components of sensing devices,requiring high surface quality and form accuracy.Fast tool servo(FTS)-based diamond turning is one of the technologies for manufacturing complicated...A lens array is often used for optical components of sensing devices,requiring high surface quality and form accuracy.Fast tool servo(FTS)-based diamond turning is one of the technologies for manufacturing complicated shapes,such as freeform optics,structured surfaces,and microlens arrays,with high machining efficiency.In this study,lens array machining was performed on copper using an FTS on a diamond turning machine.For evaluating the lens array surface topography,the focus was on surface waviness formation.As a dominating factor of surface waviness,the system dynamics behavior was investigated by capturing and analyzing the position signal.It was found that a specific waviness pattern could be formed on the surface due to the servo response.By considering the dynamics of the FTS system from the captured signals,the FTS system behavior was identified,and optimal machining parameters for the lens array were proposed.A machining test under the optimized cutting conditions reduced the average Sdq used to quantify the waviness amount from 93 to 50μrad and the standard deviation from 33 to 3μrad,which greatly improved the consistency in accuracy for all lens arrays.This study will contribute to the appropriate utilization of FTS systems in the ultraprecision machining of various advanced optics,such as microlens arrays.展开更多
Thin-walled components possess high strength and lightweight characteristics;thus,they are widely used in aerospace,automotive,and other industrial felds.However,their low stifness makes them susceptible to deformatio...Thin-walled components possess high strength and lightweight characteristics;thus,they are widely used in aerospace,automotive,and other industrial felds.However,their low stifness makes them susceptible to deformation induced by cutting forces during machining,which leads to poor form accuracy.To address this issue,this paper proposes an in-process deformation estimation and compensation method.Because direct,accurate measurement of the deformation at the cutting point is challenging,the deformation is estimated based on the deformations measured at points in the uncut area along the same axial line as the cutting point.To establish the deformation relationship along the axial line for estimation,fnite element method simulations are conducted to generate axial deformation profles corresponding to diferent cutting force locations.Additionally,a calibration coefcient obtained through experiments is applied to enhance the accuracy of the deformation estimation.Then,the estimated deformation is fed into the control loop of the fast tool servo system to compensate for machining-induced deformation efectively.To validate the efectiveness of the proposed method,machining experiments on sinusoidal pit arrays and sinusoidal grid microstructures are performed.The experimental results demonstrate that the proposed method substantially improves machining accuracy.展开更多
The quality of the micro-mechanical machining outcome depends significantly on the tracking performance of the miniaturized linear motor drive precision stage. The tracking behavior of a direct drive design is prone t...The quality of the micro-mechanical machining outcome depends significantly on the tracking performance of the miniaturized linear motor drive precision stage. The tracking behavior of a direct drive design is prone to uncertainties such as model parameter variations and disturbances. Robust optimal tracking controller design for this kind of precision stages with mass and damping ratio uncertainties was researched. The mass and damping ratio uncertainties were modeled as the structured parametric uncertainty model. An identification method for obtaining the parametric uncertainties was developed by using unbiased least square technique. The instantaneous frequency bandwidth of the external disturbance signals was analyzed by using short time Fourier transform technique. A two loop tracking control strategy that combines the p-synthesis and the disturbance observer （DOB） techniques was proposed. The p-synthesis technique was used to design robust optimal controllers based on structured uncertainty models. By complementing the/z controller, the DOB was applied to further improving the disturbance rejection performance. To evaluate the positioning performance of the proposed control strategy, the comparative experiments were conducted on a prototype micro milling machine among four control schemes： the proposed two-loop tracking control, the single loop μ control, the PID control and the PID with DOB control. The disturbance rejection performances, the root mean square （RMS） tracking errors and the performance robustness of different control schemes were studied. The results reveal that the proposed control scheme has the best positioning performance. It reduces the maximal errors caused by disturbance forces such as friction force by 60% and the RMS errors by 63.4% compared with the PID control. Compared to PID with DOB control, it reduces the RMS errors by 29.6%.展开更多
基金Funded by the National High-tech R&D Program ("863" Program) of China (No.2006AA04Z314)
文摘A fast tool servo (FTS) system is developed for the fabrication of non-rotationally symmetric micro-structured surfaces using single-point diamond turning machines.The constructed FTS employs a piezoelectric tube actuator (PZT) to actuate the diamond tool and a capacitive probe as the feedback sensor.To compensate the inherent nonlinear hysteresis behavior of the piezoelectric actuator,Proportional Integral (PI) feedback control is implemented.Besides,a feed-forward control based on a simple feed-forward predictor has been added to achieve better tracking performance.Experimental results indicate that error motions in the performance of the system caused by hysteresis can be reduced greatly and the micro-structured surface is successfully fabricated by implementing the FTS.
基金supported by Japan Society for the Promotion of Science,Grant-in-Aid for Scientific Research(B),Project Number 21H01230.
文摘Diamond turning based on a fast tool servo(FTS)is widely used in freeform optics fabrication due to its high accuracy and machining efficiency.As a new trend,recently developed high-frequency and long-stroke FTS units are independently driven by a separate control system from the machine tool controller.However,the tool path generation strategy for the independently controlled FTS is far from complete.This study aims to establish methods for optimizing tool path for the independent control FTS to reduce form errors in a single step of machining.Different from the conventional integrated FTS control system,where control points are distributed in a spiral pattern,in this study,the tool path for the independent FTS controller is generated by the ring method and the mesh method,respectively.The machined surface profile is predicted by simulation and the parameters for the control point generation are optimized by minimizing the deviation between the predicted and the designed surfaces.To demonstrate the feasibility of the proposed tool path generation strategies,cutting tests of a two-dimensional sinewave and a micro-lens array were conducted and the results were compared.As a result,after tool path optimization,the peak-to-valley form error of the machined surface was reduced from 429 nm to 56 nm for the two-dimensional sinewave by using the ring method,and from 191 nm to 103 nm for the micro-lens array by using the mesh method,respectively.
基金Project(2010-0008-277)supported by NCRC(National Core Research Center)Program of the Ministry of Education,Science and Technology,KoreaProject supported by"Development of Micro Feature Machining System on Large Surface and Core Technologies for Measurement & Inspection"of Ministry of Knowledge Economy,Korea
文摘The development of the fast tool servo (FTS) for precision machining was investigated.The micron machining performance of a piezoelectric-assisted FTS on copper alloy was evaluated.The results indicate that the quality of the microstructure depends mainly on two important factors:the cutting speed (or spindle speed) and the driving frequency of the FTS.The excessive driving frequency increases the formation of burrs.The effect of the clearance angle of the diamond tool on the microstructure machining precision was also investigated.
文摘An experimental study of micro-tool servo with electrostrictive actuator is presented.The design methods as well as the performance of the entire mechanism is given out.The results of the experiment show that the resolution of the micro-tool servo is 0.02μm and the frequency response is up to 200Hz,which satisfies the requirements of the ultra-precision machining.
基金supported by NCRC(National Core Research Center)program of the Ministry of Education,Science and Technology(2010-0008-277)"Development of next generation multi-functional machining systems for eco/bio components" project of ministry of knowledge economy
文摘Ultra-precision diamond machining with piezoelectric-assisted fast tool servo (FTS) was used to produce various free-form surfaces.A low cost,rapid and large area fabrication of uniform hydrophobic surface at room temperature which transfers the FTS fabricated sinusoidal grid surface to the flat film with UV-moulding process was described.A piezoelectric-assisted FTS with high band width of 2 kHz,travel range up to 16 μm and the compact mechanism structure was designed for the sinusoidal grid surface machining and the dynamic performance testing of FTS was described in detail.Machining results indicate that the dimensions of sinusoidal grid change with the variation of the FTS machining condition.Wetting properties of UV-moulded surface were evaluated,the best contact angle was measured to be 120.5° on the sinusoidal grid surface with profile wavelength of 350 μm and peak-to-valley amplitude of about 16 μm.
文摘A lens array is often used for optical components of sensing devices,requiring high surface quality and form accuracy.Fast tool servo(FTS)-based diamond turning is one of the technologies for manufacturing complicated shapes,such as freeform optics,structured surfaces,and microlens arrays,with high machining efficiency.In this study,lens array machining was performed on copper using an FTS on a diamond turning machine.For evaluating the lens array surface topography,the focus was on surface waviness formation.As a dominating factor of surface waviness,the system dynamics behavior was investigated by capturing and analyzing the position signal.It was found that a specific waviness pattern could be formed on the surface due to the servo response.By considering the dynamics of the FTS system from the captured signals,the FTS system behavior was identified,and optimal machining parameters for the lens array were proposed.A machining test under the optimized cutting conditions reduced the average Sdq used to quantify the waviness amount from 93 to 50μrad and the standard deviation from 33 to 3μrad,which greatly improved the consistency in accuracy for all lens arrays.This study will contribute to the appropriate utilization of FTS systems in the ultraprecision machining of various advanced optics,such as microlens arrays.
基金supported in part by National Natural Science Foundation of China under Grant 52425505 and U22A20207in part by National Key R&D Program of China under Grant 2022YFB3403302in part by Zhejiang Provincial Key R&D Program of China under Grant 2023C01056.
文摘Thin-walled components possess high strength and lightweight characteristics;thus,they are widely used in aerospace,automotive,and other industrial felds.However,their low stifness makes them susceptible to deformation induced by cutting forces during machining,which leads to poor form accuracy.To address this issue,this paper proposes an in-process deformation estimation and compensation method.Because direct,accurate measurement of the deformation at the cutting point is challenging,the deformation is estimated based on the deformations measured at points in the uncut area along the same axial line as the cutting point.To establish the deformation relationship along the axial line for estimation,fnite element method simulations are conducted to generate axial deformation profles corresponding to diferent cutting force locations.Additionally,a calibration coefcient obtained through experiments is applied to enhance the accuracy of the deformation estimation.Then,the estimated deformation is fed into the control loop of the fast tool servo system to compensate for machining-induced deformation efectively.To validate the efectiveness of the proposed method,machining experiments on sinusoidal pit arrays and sinusoidal grid microstructures are performed.The experimental results demonstrate that the proposed method substantially improves machining accuracy.
基金Project(50875257) supported by the National Natural Science Foundation of China
文摘The quality of the micro-mechanical machining outcome depends significantly on the tracking performance of the miniaturized linear motor drive precision stage. The tracking behavior of a direct drive design is prone to uncertainties such as model parameter variations and disturbances. Robust optimal tracking controller design for this kind of precision stages with mass and damping ratio uncertainties was researched. The mass and damping ratio uncertainties were modeled as the structured parametric uncertainty model. An identification method for obtaining the parametric uncertainties was developed by using unbiased least square technique. The instantaneous frequency bandwidth of the external disturbance signals was analyzed by using short time Fourier transform technique. A two loop tracking control strategy that combines the p-synthesis and the disturbance observer （DOB） techniques was proposed. The p-synthesis technique was used to design robust optimal controllers based on structured uncertainty models. By complementing the/z controller, the DOB was applied to further improving the disturbance rejection performance. To evaluate the positioning performance of the proposed control strategy, the comparative experiments were conducted on a prototype micro milling machine among four control schemes： the proposed two-loop tracking control, the single loop μ control, the PID control and the PID with DOB control. The disturbance rejection performances, the root mean square （RMS） tracking errors and the performance robustness of different control schemes were studied. The results reveal that the proposed control scheme has the best positioning performance. It reduces the maximal errors caused by disturbance forces such as friction force by 60% and the RMS errors by 63.4% compared with the PID control. Compared to PID with DOB control, it reduces the RMS errors by 29.6%.
