With regard to precision/ultra-precision motion systems,it is important to achieve excellent tracking performance for various trajectory tracking tasks even under uncertain external disturbances.In this paper,to overc...With regard to precision/ultra-precision motion systems,it is important to achieve excellent tracking performance for various trajectory tracking tasks even under uncertain external disturbances.In this paper,to overcome the limitation of robustness to trajectory variations and external disturbances in offline feedforward compensation strategies such as iterative learning control(ILC),a novel real-time iterative compensation(RIC)control framework is proposed for precision motion systems without changing the inner closed-loop controller.Specifically,the RIC method can be divided into two parts,i.e.,accurate model prediction and real-time iterative compensation.An accurate prediction model considering lumped disturbances is firstly established to predict tracking errors at future sampling times.In light of predicted errors,a feedforward compensation term is developed to modify the following reference trajectory by real-time iterative calculation.Both the prediction and compen-sation processes are finished in a real-time motion control sampling period.The stability and convergence of the entire control system after real-time iterative compensation is analyzed for different conditions.Various simulation results consistently demonstrate that the proposed RIC framework possesses satisfactory dynamic regulation capability,which contributes to high tracking accuracy comparable to ILC or even better and strong robustness.展开更多
Traditionally, basis weight control valve is driven by a constant frequency pulse signal. Therefore, it is difficult for the valve to match the control precision of basis weight. Dynamic simulation research using Matl...Traditionally, basis weight control valve is driven by a constant frequency pulse signal. Therefore, it is difficult for the valve to match the control precision of basis weight. Dynamic simulation research using Matlab/Simulink indicates that there is much more overshoot and fluctuating during the valve-positioning process. In order to improve the valve-positioning precision, the control method of trapezoidal velocity curve was studied. The simulation result showed that the positioning steady-state error was less than 0.0056%, whereas the peak error was less than 0.016% by using trapezoidal velocity curve at 10 positioning steps. A valve-positioning precision experimental device for the stepper motor of basis weight control valve was developed. The experiment results showed that the error ratio of 1/10000 positioning steps was 4% by using trapezoidal velocity curve. Furthermore, the error ratio of 10/10000 positioning steps was 0.5%. It proved that the valve-positioning precision of trapezoidal velocity curve was much higher than that of the constant frequency pulse signal control strategy. The new control method of trapezoidal velocity curve can satisfy the precision requirement of 10000 steps.展开更多
This article focuses on asymptotic precision motion control for electro-hydraulic axis systems under unknown time-variant parameters,mismatched and matched disturbances.Different from the traditional adaptive results ...This article focuses on asymptotic precision motion control for electro-hydraulic axis systems under unknown time-variant parameters,mismatched and matched disturbances.Different from the traditional adaptive results that are applied to dispose of unknown constant parameters only,the unique feature is that an adaptive-gain nonlinear term is introduced into the control design to handle unknown time-variant parameters.Concurrently both mismatched and matched disturbances existing in electro-hydraulic axis systems can also be addressed in this way.With skillful integration of the backstepping technique and the adaptive control,a synthesized controller framework is successfully developed for electro-hydraulic axis systems,in which the coupled interaction between parameter estimation and disturbance estimation is avoided.Accordingly,this designed controller has the capacity of low-computation costs and simpler parameter tuning when compared to the other ones that integrate the adaptive control and observer/estimator-based technique to dividually handle parameter uncertainties and disturbances.Also,a nonlinear filter is designed to eliminate the“explosion of complexity”issue existing in the classical back-stepping technique.The stability analysis uncovers that all the closed-loop signals are bounded and the asymptotic tracking performance is also assured.Finally,contrastive experiment results validate the superiority of the developed method as well.展开更多
SARS-CoV-2 has been marked as a highly pathogenic coronavirus of COVID-19 disease into the human population,causing over 5.5 million confirmed cases worldwide.As COVID-19 has posed a global threat with significant hum...SARS-CoV-2 has been marked as a highly pathogenic coronavirus of COVID-19 disease into the human population,causing over 5.5 million confirmed cases worldwide.As COVID-19 has posed a global threat with significant human casualties and severe economic losses,there is a pressing demand to further understand the current situation and develop rational strategies to contain the drastic spread of the virus.Although there are no specific antiviral therapies that have proven effective in randomized clinical trials,currently,the rapid detection technology along with several promising therapeutics for COVID-19 have mitigated its drastic transmission.Besides,global institutions and corporations have commenced to parse out effective vaccines for the prevention of COVID-19.Herein,the present review will give exhaustive details of extensive researches concerning the drug discovery and therapeutic options for COVID-19 as well as some insightful discussions of the status of COVID-19.展开更多
Radiator thermal performance test equipment plays a key role in the processing of developing a new type of heat radiator and its application products.The precise of temperature controlling,temperature measuring andflo...Radiator thermal performance test equipment plays a key role in the processing of developing a new type of heat radiator and its application products.The precise of temperature controlling,temperature measuring andflow measuring are the vital factors for a radiator thermal performance test equipment.Based on the above back-ground,this paper improves the measurement and control system of radiator thermal performance test equip-ment,which improves the accuracy of the radiator thermal performance test equipment.This paper also optimizes the software and hardware system simultaneously so as to improve the precision of the auto-test system of test equipment.Theflow rate ranges from 175 kg/h to 178 kg/h under different conditions.The average is 176.5 kg/h and the deviation rates are from 1.62%to 1.97%.The heat produced under various conditions is different.The maximum is 4.3 kW and the minimum is 4.2 kW for condition 1,the maximum is 3.3 kW and the minimum is 3.2 kW for condition 2 and the maximum is 1.95 kW and the minimum is 1.89 kW for condition 3.However,the deviation rate is about 2.9%,which shows that the device has high stability and high precision.This paper studies a new electronic heat cost allocate meter test method by radiator thermal performance test equipment at the same time.This paper tests temperature changes through four measures points and gets a result appeared as a heat backup which should be avoided when using in the test of electronic heat cost allocate meter.Some experiences and references could be gained for further research in the heating system from this test and research.展开更多
Supported atomically dispersed metal catalysts(ADMCs)have received enormous attention due to their high atom utilization efficiency,mass activity and excellent selectivity.Single-atom site catalysts(SACs)with monometa...Supported atomically dispersed metal catalysts(ADMCs)have received enormous attention due to their high atom utilization efficiency,mass activity and excellent selectivity.Single-atom site catalysts(SACs)with monometal-center as the quintessential ADMCs have been extensively studied in the catalysis-related fields.Beyond SACs,novel atomically dispersed metal catalysts(NADMCs)with flexible active sites featuring two or more catalytically centers including dual-atom and triple-atom catalysts have drawn ever-increasing attention recently.Owing to the presence of multiple neighboring active sites,NADMCs could exhibit much higher activity and selectivity compared with SACs,especially in those complicated reactions with multi-step intermediates.This review comprehensively outlines the recent exciting advances on the NADMCs with emphasis on the deeper understanding of the synergistic interactions among multiple metal atoms and underlying structure-performance relationships.It starts with the systematical introduction of principal synthetic approaches for NADMCs highlighting the key issues of each fabrication method including the atomically precise control in the design of metal nuclearity,and then the state-of-the-art characterizations for identifying and monitoring the atomic structure of NADMCs are explored.Thereafter,the recent development of NADMCs in energy-related applications is systematically discussed.Finally,we provide some new insights into the remaining challenges and opportunities for the development of NADMCs.展开更多
The purpose of this paper is to present a novel topology optimization approach to control precisely the output loads under static loads and harmonic excitations.We introduce the Artificial Bar Element(ABE)at the desig...The purpose of this paper is to present a novel topology optimization approach to control precisely the output loads under static loads and harmonic excitations.We introduce the Artificial Bar Element(ABE)at the designated output positions,where the output loads are equivalently measured and constrained with the nodal displacements of ABE.Optimization model is then formulated considering the output load constraints as well as the minimization of strain energy and dynamic displacement responses respectively under the static and dynamic conditions.The influences of the ABEs stiffness,different material usages of the design domain,widths of the output loads constraint intervals and variation ratios of output loads are discussed in detail.The proposed method is verified with several numerical examples with clear and reasonable load transfer paths.展开更多
Introduction The high-energy photon source,which has been built in Huairou,Beijing,has high requirements on magnetic field dithering.Magnetic field dithering is mainly determined by the stability of the output current...Introduction The high-energy photon source,which has been built in Huairou,Beijing,has high requirements on magnetic field dithering.Magnetic field dithering is mainly determined by the stability of the output current of the power supply.In order to ensure the stability of the output current of quadrupole magnet power supply,the power supply sampling control loop needs to be precisely designed.In this paper,a precision ADC sampling system based on internal temperature control is designed to carry out precise control of the sampling ADC.Materials In this design,precise ADC chip is used to complete the precise sampling of the system.The precise sampling system contains a DAC system for high-speed settings.Methods In order to verify the design of the system,high-precision quadrupolemagnet power supply is used for measurement.Conclusion The experimental results show that the temperature variation range of precision temperature control ADC system is±0.1°C.By using the precise temperature controlADCsystem,the output current stability of the high-precision quadrupole magnet power supply is effectively improved.展开更多
Variable seeding by sowing decision can improve the utilization rate of resources.In order to achieve more accurate position control and sowing rate control,precision sowing decision control system was developed,and t...Variable seeding by sowing decision can improve the utilization rate of resources.In order to achieve more accurate position control and sowing rate control,precision sowing decision control system was developed,and the integral separation Proportional Integral Derivative(PID)control algorithm of metering disc speed and grid based dead reckoning method were proposed.In order to test the performance of the system,the experiment of the influence of integral switching on step response and the experiment of seeding response based on simulated sowing decision were carried out.The results showed that average lag distance based on dead reckoning was 72.2 cm less than that of non-dead reckoning;system response distance of integral separation PID control algorithm was 43.1 cm shorter than that of ordinary PID control algorithm.The field experiment showed that the error of the monitoring sowing rate relative to the actual sowing rate was 3.5%,the average transition distance within the speed range of 3-9 km/h was 139.5 cm,and the standard deviation was 12.8 cm.The developed seeding control system improves the accuracy of seeding based on sowing decision,and provides a technical reference for low-cost sowing decision based control system in China.展开更多
Although photothermal therapy(PTT) has emerged as an appealing strategy for cancer treatment, the development of photothermal agents capable of precisely controlling temperature remains a challenge. In this paper, we ...Although photothermal therapy(PTT) has emerged as an appealing strategy for cancer treatment, the development of photothermal agents capable of precisely controlling temperature remains a challenge. In this paper, we present a novel synthetic photosensitizer based on a sulfur-substituted hemicyanine. It was discovered that replacing an oxygen atom in a hemicyanine derivative with a sulfur atom significantly enhances photothermal efficiency and enables lysosome targeting in cancer cells.More importantly, because of the rigid planer structure of the sulfur-substituted hemicyanine, which differs from traditional photothermal agents(PTAs) based on twisted intramolecular charge transfer(TICT) or group rotation mechanisms, the efficiency of photothermal conversion is not affected by intracellular viscosity, allowing precise temperature control during PTT.Further modifying the agent with a glutathione-responsive moiety allows the PTAs to be activated only in cancer cells. The newly proposed PTA achieves efficient PTT in a tumor-bearing mouse model while having negligible toxic side effects on healthy tissues.展开更多
基金This work was supported in part by the National Nature Science Foundation of China(51922059)in part by the Beijing Natural Science Foundation(JQ19010)in part by the China Postdoctoral Science Foundation(2021T140371).
文摘With regard to precision/ultra-precision motion systems,it is important to achieve excellent tracking performance for various trajectory tracking tasks even under uncertain external disturbances.In this paper,to overcome the limitation of robustness to trajectory variations and external disturbances in offline feedforward compensation strategies such as iterative learning control(ILC),a novel real-time iterative compensation(RIC)control framework is proposed for precision motion systems without changing the inner closed-loop controller.Specifically,the RIC method can be divided into two parts,i.e.,accurate model prediction and real-time iterative compensation.An accurate prediction model considering lumped disturbances is firstly established to predict tracking errors at future sampling times.In light of predicted errors,a feedforward compensation term is developed to modify the following reference trajectory by real-time iterative calculation.Both the prediction and compen-sation processes are finished in a real-time motion control sampling period.The stability and convergence of the entire control system after real-time iterative compensation is analyzed for different conditions.Various simulation results consistently demonstrate that the proposed RIC framework possesses satisfactory dynamic regulation capability,which contributes to high tracking accuracy comparable to ILC or even better and strong robustness.
基金supported by the International S&T Cooperation Program of China(GrantNo.2010DFB43660)National Natural Science Foundation of China(Grant No.51375286)Scientific Research Program Funded by Shaanxi Provincial Education Department(Program No.16JF005)
文摘Traditionally, basis weight control valve is driven by a constant frequency pulse signal. Therefore, it is difficult for the valve to match the control precision of basis weight. Dynamic simulation research using Matlab/Simulink indicates that there is much more overshoot and fluctuating during the valve-positioning process. In order to improve the valve-positioning precision, the control method of trapezoidal velocity curve was studied. The simulation result showed that the positioning steady-state error was less than 0.0056%, whereas the peak error was less than 0.016% by using trapezoidal velocity curve at 10 positioning steps. A valve-positioning precision experimental device for the stepper motor of basis weight control valve was developed. The experiment results showed that the error ratio of 1/10000 positioning steps was 4% by using trapezoidal velocity curve. Furthermore, the error ratio of 10/10000 positioning steps was 0.5%. It proved that the valve-positioning precision of trapezoidal velocity curve was much higher than that of the constant frequency pulse signal control strategy. The new control method of trapezoidal velocity curve can satisfy the precision requirement of 10000 steps.
基金supported in part by the National Key R&D Program of China(No.2021YFB2011300)the National Natural Science Foundation of China(No.52075262,51905271,52275062)+1 种基金the Fok Ying-Tong Education Foundation of China(No.171044)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX22_0471)。
文摘This article focuses on asymptotic precision motion control for electro-hydraulic axis systems under unknown time-variant parameters,mismatched and matched disturbances.Different from the traditional adaptive results that are applied to dispose of unknown constant parameters only,the unique feature is that an adaptive-gain nonlinear term is introduced into the control design to handle unknown time-variant parameters.Concurrently both mismatched and matched disturbances existing in electro-hydraulic axis systems can also be addressed in this way.With skillful integration of the backstepping technique and the adaptive control,a synthesized controller framework is successfully developed for electro-hydraulic axis systems,in which the coupled interaction between parameter estimation and disturbance estimation is avoided.Accordingly,this designed controller has the capacity of low-computation costs and simpler parameter tuning when compared to the other ones that integrate the adaptive control and observer/estimator-based technique to dividually handle parameter uncertainties and disturbances.Also,a nonlinear filter is designed to eliminate the“explosion of complexity”issue existing in the classical back-stepping technique.The stability analysis uncovers that all the closed-loop signals are bounded and the asymptotic tracking performance is also assured.Finally,contrastive experiment results validate the superiority of the developed method as well.
文摘SARS-CoV-2 has been marked as a highly pathogenic coronavirus of COVID-19 disease into the human population,causing over 5.5 million confirmed cases worldwide.As COVID-19 has posed a global threat with significant human casualties and severe economic losses,there is a pressing demand to further understand the current situation and develop rational strategies to contain the drastic spread of the virus.Although there are no specific antiviral therapies that have proven effective in randomized clinical trials,currently,the rapid detection technology along with several promising therapeutics for COVID-19 have mitigated its drastic transmission.Besides,global institutions and corporations have commenced to parse out effective vaccines for the prevention of COVID-19.Herein,the present review will give exhaustive details of extensive researches concerning the drug discovery and therapeutic options for COVID-19 as well as some insightful discussions of the status of COVID-19.
基金supported by the Tianjin Science and Technology Project(Project No.19JCTPJC44300)The Science&Technology Development Fund of Tianjin Education Commission for Higher Education(Project No.2018KJ261)Science and Technology Program Project of Jin Nan District Tianjin(Project Nos.201805015&20190111).
文摘Radiator thermal performance test equipment plays a key role in the processing of developing a new type of heat radiator and its application products.The precise of temperature controlling,temperature measuring andflow measuring are the vital factors for a radiator thermal performance test equipment.Based on the above back-ground,this paper improves the measurement and control system of radiator thermal performance test equip-ment,which improves the accuracy of the radiator thermal performance test equipment.This paper also optimizes the software and hardware system simultaneously so as to improve the precision of the auto-test system of test equipment.Theflow rate ranges from 175 kg/h to 178 kg/h under different conditions.The average is 176.5 kg/h and the deviation rates are from 1.62%to 1.97%.The heat produced under various conditions is different.The maximum is 4.3 kW and the minimum is 4.2 kW for condition 1,the maximum is 3.3 kW and the minimum is 3.2 kW for condition 2 and the maximum is 1.95 kW and the minimum is 1.89 kW for condition 3.However,the deviation rate is about 2.9%,which shows that the device has high stability and high precision.This paper studies a new electronic heat cost allocate meter test method by radiator thermal performance test equipment at the same time.This paper tests temperature changes through four measures points and gets a result appeared as a heat backup which should be avoided when using in the test of electronic heat cost allocate meter.Some experiences and references could be gained for further research in the heating system from this test and research.
基金the Beijing Natural Science Foundation(No.2224096)the National Key R&D Program of China(No.2018YFA0702003)+3 种基金the Science and Technology Key Project of Guangdong Province,China(No.2020B010188002)the China Postdoctoral Science Foundation(Nos.2021M690086 and 2021TQ0170)X.B.Z.acknowledges funding support from the Office of China Postdoctoral Council(No.YJ20200277)the“Shuimu Tsinghua Scholar Program"(No.2020SM109)of Tsinghua University,China.
文摘Supported atomically dispersed metal catalysts(ADMCs)have received enormous attention due to their high atom utilization efficiency,mass activity and excellent selectivity.Single-atom site catalysts(SACs)with monometal-center as the quintessential ADMCs have been extensively studied in the catalysis-related fields.Beyond SACs,novel atomically dispersed metal catalysts(NADMCs)with flexible active sites featuring two or more catalytically centers including dual-atom and triple-atom catalysts have drawn ever-increasing attention recently.Owing to the presence of multiple neighboring active sites,NADMCs could exhibit much higher activity and selectivity compared with SACs,especially in those complicated reactions with multi-step intermediates.This review comprehensively outlines the recent exciting advances on the NADMCs with emphasis on the deeper understanding of the synergistic interactions among multiple metal atoms and underlying structure-performance relationships.It starts with the systematical introduction of principal synthetic approaches for NADMCs highlighting the key issues of each fabrication method including the atomically precise control in the design of metal nuclearity,and then the state-of-the-art characterizations for identifying and monitoring the atomic structure of NADMCs are explored.Thereafter,the recent development of NADMCs in energy-related applications is systematically discussed.Finally,we provide some new insights into the remaining challenges and opportunities for the development of NADMCs.
基金supported by National Key Research and Development Program(No.2017YFB1102800)NSFC for Excellent Young Scholars(No.11722219)Key Project of NSFC(Nos.51790171,5171101743)
文摘The purpose of this paper is to present a novel topology optimization approach to control precisely the output loads under static loads and harmonic excitations.We introduce the Artificial Bar Element(ABE)at the designated output positions,where the output loads are equivalently measured and constrained with the nodal displacements of ABE.Optimization model is then formulated considering the output load constraints as well as the minimization of strain energy and dynamic displacement responses respectively under the static and dynamic conditions.The influences of the ABEs stiffness,different material usages of the design domain,widths of the output loads constraint intervals and variation ratios of output loads are discussed in detail.The proposed method is verified with several numerical examples with clear and reasonable load transfer paths.
文摘Introduction The high-energy photon source,which has been built in Huairou,Beijing,has high requirements on magnetic field dithering.Magnetic field dithering is mainly determined by the stability of the output current of the power supply.In order to ensure the stability of the output current of quadrupole magnet power supply,the power supply sampling control loop needs to be precisely designed.In this paper,a precision ADC sampling system based on internal temperature control is designed to carry out precise control of the sampling ADC.Materials In this design,precise ADC chip is used to complete the precise sampling of the system.The precise sampling system contains a DAC system for high-speed settings.Methods In order to verify the design of the system,high-precision quadrupolemagnet power supply is used for measurement.Conclusion The experimental results show that the temperature variation range of precision temperature control ADC system is±0.1°C.By using the precise temperature controlADCsystem,the output current stability of the high-precision quadrupole magnet power supply is effectively improved.
基金This study was financially supported by the National Key Research and Development Program(Grant No.2017YFD0700502).
文摘Variable seeding by sowing decision can improve the utilization rate of resources.In order to achieve more accurate position control and sowing rate control,precision sowing decision control system was developed,and the integral separation Proportional Integral Derivative(PID)control algorithm of metering disc speed and grid based dead reckoning method were proposed.In order to test the performance of the system,the experiment of the influence of integral switching on step response and the experiment of seeding response based on simulated sowing decision were carried out.The results showed that average lag distance based on dead reckoning was 72.2 cm less than that of non-dead reckoning;system response distance of integral separation PID control algorithm was 43.1 cm shorter than that of ordinary PID control algorithm.The field experiment showed that the error of the monitoring sowing rate relative to the actual sowing rate was 3.5%,the average transition distance within the speed range of 3-9 km/h was 139.5 cm,and the standard deviation was 12.8 cm.The developed seeding control system improves the accuracy of seeding based on sowing decision,and provides a technical reference for low-cost sowing decision based control system in China.
基金supported by the National Natural Science Foundation of China(21925802,21878039,22022803,22078046)the NSFC-Liaoning United Fund(U1908202)the National Key Research and Development Plan(2018AAA0100301)。
文摘Although photothermal therapy(PTT) has emerged as an appealing strategy for cancer treatment, the development of photothermal agents capable of precisely controlling temperature remains a challenge. In this paper, we present a novel synthetic photosensitizer based on a sulfur-substituted hemicyanine. It was discovered that replacing an oxygen atom in a hemicyanine derivative with a sulfur atom significantly enhances photothermal efficiency and enables lysosome targeting in cancer cells.More importantly, because of the rigid planer structure of the sulfur-substituted hemicyanine, which differs from traditional photothermal agents(PTAs) based on twisted intramolecular charge transfer(TICT) or group rotation mechanisms, the efficiency of photothermal conversion is not affected by intracellular viscosity, allowing precise temperature control during PTT.Further modifying the agent with a glutathione-responsive moiety allows the PTAs to be activated only in cancer cells. The newly proposed PTA achieves efficient PTT in a tumor-bearing mouse model while having negligible toxic side effects on healthy tissues.
