Aluminum alloy thin-walled structures are widely used in the automotive industry due to their advantages related to light weight and crashworthiness.They can be produced at room temperature by the electrohydraulic for...Aluminum alloy thin-walled structures are widely used in the automotive industry due to their advantages related to light weight and crashworthiness.They can be produced at room temperature by the electrohydraulic forming process.In the present study,the influence of the related parameters on the forming quality of a 6063 aluminum alloy sinusoidal corrugation tube has been assessed.In particular,the orthogonal experimental design(OED)and central composite design(CCD)methods have been used.Through the range analysis and variance analysis of the experimental data,the influence degree of wire diameter(WD)and discharge energy(DE)on the forming quality was determined.Multiple regression analysis was performed using the response surface methodology.A prediction model for the attaching-die state coefficient was established accordingly.The following optimal arrangement of parameters was obtained(WD=0.759 mm,DE=2.926 kJ).The attaching-die state coefficient reached the peak value of 0.001.Better optimized wire diameter and discharge energy for a better attaching-die state could be screened by CCD compared with OED.The response surface method in CCD was more suitable for the design and optimization of the considered process parameters.展开更多
The surgical management of gallstone ileus is complex and potentially highly morbid.Initial management requires enterolithotomy and is generally followed by fistula resection at a later date.There have been reports of...The surgical management of gallstone ileus is complex and potentially highly morbid.Initial management requires enterolithotomy and is generally followed by fistula resection at a later date.There have been reports of gallstone extraction using various endoscopic modalities to relieve the obstruction,however,to date,there has never been a published case of endoscopic stone extraction from the colon using electrohydraulic lithotripsy.In this report,we present the technique employed to successfully perform an electrohydraulic lithotripsy for removal of a large gallstone impacted in the sigmoid colon.A cavity was excavated in an obstructing 4.1 cm lamellated stone in the sigmoid colon using electrohydraulic lithotripsy.A screw stent retractor and stent extractor bored a larger lumen which allowed for guidewire advancement and stone fracture via serial pneumatic balloon dilatation.The stone fragments were removed.Electrohydraulic lithotripsy is a safe and effective method to treat colonic obstruction in the setting of gallstone ileus.展开更多
BACKGROUND In patients with large stones in the common bile duct(CBD),advanced treatment modalities are generally needed.Here,we present an interesting case of a huge CBD stone treated with electrohydraulic lithotrips...BACKGROUND In patients with large stones in the common bile duct(CBD),advanced treatment modalities are generally needed.Here,we present an interesting case of a huge CBD stone treated with electrohydraulic lithotripsy(EHL)by the percutaneous approach and rendezvous endoscopic retrograde cholangiography(ERC)using a nasal endoscope.CASE SUMMARY A 91-year-old woman underwent ERC for a symptomatic large CBD stone with a diameter of 50 mm.She was referred to our institution after the failure of lithotomy by ERC,and after undergoing percutaneous transhepatic biliary drainage.We attempted to fragment the stone by transhepatic cholangioscopy using EHL.However,the stones were too large and partly soft clay-like for lithotripsy.Next,we attempted lithotomy with ERC and cholangioscopy by the rendezvous technique using a nasal endoscope and achieved complete lithotomy.No complication was observed at the end of this procedure.CONCLUSION Cholangioscopy by rendezvous technique using a nasal endoscope is a feasible and safe endoscopic method for removing huge CBD stones.展开更多
Electrohydraulic servosystem have been used in industry in a wide number of applications. Its dynamics are highly nonlinear and also have large extent of model uncertainties and external disturbances. In order to incr...Electrohydraulic servosystem have been used in industry in a wide number of applications. Its dynamics are highly nonlinear and also have large extent of model uncertainties and external disturbances. In order to increase the reliability, controllability and utilizing the superior speed of response achievable from electrohydraulic systems, further research is required to develop a control software has the ability of overcoming the problems of system nonlinearities. In This paper, a Proportional Integral Derivative (PID) controller is designed and attached to electrohydraulic servo actuator system to control its angular position. The PID parameters are optimized by the Genetic Algorithm (GA). The controller is verified on the state space model of servovalve attached to a rotary actuator by SIMULINK program. The appropriate specifications of the GA for the rotary position control of an actuator system are presented. It is found that the optimal values of the feedback gains can be obtained within 10 generations, which corresponds to about 200 experiments. A new fitness function was implemented to optimize the feedback gains and its efficiency was verified for control such nonlinear servosystem.展开更多
The digital testing technique based on computers for dynamic characteristics of electrohydraulic servovalves via frequency scan method is researched. The no-load piston which measures the servo's transient output ...The digital testing technique based on computers for dynamic characteristics of electrohydraulic servovalves via frequency scan method is researched. The no-load piston which measures the servo's transient output flow is designed properly. The velocity testing method by which the speed signal can be obtained indirectly by means of a piezoelectral accelerometer is given. High speed sampling has been realized in Windows OS. Wavelet denoising and Fourier transform are adopted in data processing and analyses. The testing technique discussed has been applied to actual testing systems and the experimental results have proved it to be correct.展开更多
The natural frequency of the electrohydraulic system in mobile machinery is always very low,which brings difficulties to the controller design.To improve the tracking performance of the hydraulic system,mathematical m...The natural frequency of the electrohydraulic system in mobile machinery is always very low,which brings difficulties to the controller design.To improve the tracking performance of the hydraulic system,mathematical modeling of the electrohydraulic lifting system and the rubber hose was accomplished according to an electrohydraulic lifting test rig built in the laboratory.Then,valve compensation strategy,including spool opening compensation (SOC) and dead zone compensation (DZC),was designed based on the flow-pressure characteristic of a closed-centered proportional valve.Comparative experiments on point-to-point trajectory tracking between a proportional controller with the proposed compensations and a traditional PI controller were conducted.Experiment results show that the maximal absolute values of the tracking error are reduced from 0.039 m to 0.019 m for the slow point-to-point motion trajectory and from 0.085 m to 0.054 m for the fast point-to-point motion trajectory with the proposed compensations.Moreover,tracking error of the proposed controller was analyzed and corresponding suggestions to reduce the tracking error were put forward.展开更多
This paper presents a bi-directional permanent-magnet linear actuator for directly driving electrohydraulic valves with low power consumption. Its static and dynamic performances were analyzed using the 2D finite elem...This paper presents a bi-directional permanent-magnet linear actuator for directly driving electrohydraulic valves with low power consumption. Its static and dynamic performances were analyzed using the 2D finite element method,taking into account the nonlinear characterization and the eddy current loss of the magnetic material. The experiment and simulation results agree well and show that the prototype actuator can produce a force of ±100 N with the maximum power being 7 W and has linear characteristics with a positive magnetic stiffness within a stroke of ±1 mm. Its non-linearity is less than 1.5% and the hysteresis less than 1.5%. The actuator's frequency response(-3 dB) of the displacement reaches about 15 Hz,and the most significant factor affecting the dynamic performance is identified as the eddy current loss of the magnetic material.展开更多
The frequency response design method for PDFSV (Pseudo Derivative Feedback Subvariable) control of electrohydraulic servo system is introduced. Theoretical analysis and computer simulation show that PDFSV con...The frequency response design method for PDFSV (Pseudo Derivative Feedback Subvariable) control of electrohydraulic servo system is introduced. Theoretical analysis and computer simulation show that PDFSV control is a high robust system, and a very good performance can be obtained when this theory is employed in electrohydraulic servo system.展开更多
基金supported by National Natural Science Foundation of China(Grant Nos.51975202(Junjia Cui received the grant)and 52175315(Guangyao Li received the grant)).
文摘Aluminum alloy thin-walled structures are widely used in the automotive industry due to their advantages related to light weight and crashworthiness.They can be produced at room temperature by the electrohydraulic forming process.In the present study,the influence of the related parameters on the forming quality of a 6063 aluminum alloy sinusoidal corrugation tube has been assessed.In particular,the orthogonal experimental design(OED)and central composite design(CCD)methods have been used.Through the range analysis and variance analysis of the experimental data,the influence degree of wire diameter(WD)and discharge energy(DE)on the forming quality was determined.Multiple regression analysis was performed using the response surface methodology.A prediction model for the attaching-die state coefficient was established accordingly.The following optimal arrangement of parameters was obtained(WD=0.759 mm,DE=2.926 kJ).The attaching-die state coefficient reached the peak value of 0.001.Better optimized wire diameter and discharge energy for a better attaching-die state could be screened by CCD compared with OED.The response surface method in CCD was more suitable for the design and optimization of the considered process parameters.
文摘The surgical management of gallstone ileus is complex and potentially highly morbid.Initial management requires enterolithotomy and is generally followed by fistula resection at a later date.There have been reports of gallstone extraction using various endoscopic modalities to relieve the obstruction,however,to date,there has never been a published case of endoscopic stone extraction from the colon using electrohydraulic lithotripsy.In this report,we present the technique employed to successfully perform an electrohydraulic lithotripsy for removal of a large gallstone impacted in the sigmoid colon.A cavity was excavated in an obstructing 4.1 cm lamellated stone in the sigmoid colon using electrohydraulic lithotripsy.A screw stent retractor and stent extractor bored a larger lumen which allowed for guidewire advancement and stone fracture via serial pneumatic balloon dilatation.The stone fragments were removed.Electrohydraulic lithotripsy is a safe and effective method to treat colonic obstruction in the setting of gallstone ileus.
文摘BACKGROUND In patients with large stones in the common bile duct(CBD),advanced treatment modalities are generally needed.Here,we present an interesting case of a huge CBD stone treated with electrohydraulic lithotripsy(EHL)by the percutaneous approach and rendezvous endoscopic retrograde cholangiography(ERC)using a nasal endoscope.CASE SUMMARY A 91-year-old woman underwent ERC for a symptomatic large CBD stone with a diameter of 50 mm.She was referred to our institution after the failure of lithotomy by ERC,and after undergoing percutaneous transhepatic biliary drainage.We attempted to fragment the stone by transhepatic cholangioscopy using EHL.However,the stones were too large and partly soft clay-like for lithotripsy.Next,we attempted lithotomy with ERC and cholangioscopy by the rendezvous technique using a nasal endoscope and achieved complete lithotomy.No complication was observed at the end of this procedure.CONCLUSION Cholangioscopy by rendezvous technique using a nasal endoscope is a feasible and safe endoscopic method for removing huge CBD stones.
文摘Electrohydraulic servosystem have been used in industry in a wide number of applications. Its dynamics are highly nonlinear and also have large extent of model uncertainties and external disturbances. In order to increase the reliability, controllability and utilizing the superior speed of response achievable from electrohydraulic systems, further research is required to develop a control software has the ability of overcoming the problems of system nonlinearities. In This paper, a Proportional Integral Derivative (PID) controller is designed and attached to electrohydraulic servo actuator system to control its angular position. The PID parameters are optimized by the Genetic Algorithm (GA). The controller is verified on the state space model of servovalve attached to a rotary actuator by SIMULINK program. The appropriate specifications of the GA for the rotary position control of an actuator system are presented. It is found that the optimal values of the feedback gains can be obtained within 10 generations, which corresponds to about 200 experiments. A new fitness function was implemented to optimize the feedback gains and its efficiency was verified for control such nonlinear servosystem.
文摘The digital testing technique based on computers for dynamic characteristics of electrohydraulic servovalves via frequency scan method is researched. The no-load piston which measures the servo's transient output flow is designed properly. The velocity testing method by which the speed signal can be obtained indirectly by means of a piezoelectral accelerometer is given. High speed sampling has been realized in Windows OS. Wavelet denoising and Fourier transform are adopted in data processing and analyses. The testing technique discussed has been applied to actual testing systems and the experimental results have proved it to be correct.
基金Project(2006CB705400)supported by the National Basic Research Program of China
文摘The natural frequency of the electrohydraulic system in mobile machinery is always very low,which brings difficulties to the controller design.To improve the tracking performance of the hydraulic system,mathematical modeling of the electrohydraulic lifting system and the rubber hose was accomplished according to an electrohydraulic lifting test rig built in the laboratory.Then,valve compensation strategy,including spool opening compensation (SOC) and dead zone compensation (DZC),was designed based on the flow-pressure characteristic of a closed-centered proportional valve.Comparative experiments on point-to-point trajectory tracking between a proportional controller with the proposed compensations and a traditional PI controller were conducted.Experiment results show that the maximal absolute values of the tracking error are reduced from 0.039 m to 0.019 m for the slow point-to-point motion trajectory and from 0.085 m to 0.054 m for the fast point-to-point motion trajectory with the proposed compensations.Moreover,tracking error of the proposed controller was analyzed and corresponding suggestions to reduce the tracking error were put forward.
文摘This paper presents a bi-directional permanent-magnet linear actuator for directly driving electrohydraulic valves with low power consumption. Its static and dynamic performances were analyzed using the 2D finite element method,taking into account the nonlinear characterization and the eddy current loss of the magnetic material. The experiment and simulation results agree well and show that the prototype actuator can produce a force of ±100 N with the maximum power being 7 W and has linear characteristics with a positive magnetic stiffness within a stroke of ±1 mm. Its non-linearity is less than 1.5% and the hysteresis less than 1.5%. The actuator's frequency response(-3 dB) of the displacement reaches about 15 Hz,and the most significant factor affecting the dynamic performance is identified as the eddy current loss of the magnetic material.
文摘The frequency response design method for PDFSV (Pseudo Derivative Feedback Subvariable) control of electrohydraulic servo system is introduced. Theoretical analysis and computer simulation show that PDFSV control is a high robust system, and a very good performance can be obtained when this theory is employed in electrohydraulic servo system.
