Analysis and Optimization of the Electrohydraulic Forming Process of Sinusoidal Corrugation Tubes

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.

Successful endoscopic treatment of colonic gallstone ileus using electrohydraulic lithotripsy

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.

Model-based trajectory tracking control for an electrohydraulic lifting system with valve compensation strategy

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.

Electrohydraulic lithotripsy and rendezvous nasal endoscopic cholangiography for common bile duct stone: A case report

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.

Low power linear actuator for direct drive electrohydraulic valves

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.

Research on Digital Dynamic Testing Technique for Electrohydraulic Servovalve

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.

PID Parameters Optimization Using Genetic Algorithm Technique for Electrohydraulic Servo Control System

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.

Frequency Response Design Method for PDFSV Control of Electrohydraulic Servo Systems

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.

Quasi-synchronous control of uncertain multiple electrohydraulic systems with prescribed performance constraint and input saturation

This article focuses on the high accuracy quasi-synchronous control issue of multiple electrohydraulic systems(MEHS).In order to overcome the negative effects of parameter uncertainty and external load interference of MEHS,a kind of finite-time disturbance observer(FTDO)via terminal sliding mode method is constructed based on the MEHS model to achieve fast and accuracy estimation and compensation ability.To avoid the differential explosion in backstepping iteration,the dynamic surface control is used in this paper to guarantee the follower electrohydraulic nodes synchronize to the leader motion with a better performance.Furthermore,a timevarying barrier Lyapunov function(tvBLF)is adopted during the controller design process to constraint the output tracking error of MEHS in a prescribed performance with time-varying exponential function.As the initial state condition is relax by tvBLF,the input saturation law is also adopted during the controller design process in this paper to restrain the surges of input signals,which can avoid the circuit and mechanical structure damage caused by the volatile input signal.An MEHS experimental bench is constructed to verify the effectiveness of the theoretical conclusions proposed in this paper and the advantages of the proposed conclusions in this paper are illustrated by a series of contradistinctive experimental results.

Force tracking control for electrohydraulic servo system based on adaptive neuro-fuzzy inference system(ANFIS)controller

Purpose–The purpose of this paper is to apply a intelligent algorithm to conduct the force tracking control for electrohydraulic servo system(EHSS).Specifically,the adaptive neuro-fuzzy inference system(ANFIS)is selected to improve the control performance for EHSS.Design/methodology/approach–Two types of input–output data were chosen to train the ANFIS models.The inputs are the desired and actual forces,and the output is the current.The first type is to set a sinusoidal signal for the current to produce the actual driving force,and the desired force is chosen as same as the actual force.The other type is to give a sinusoidal signal for the desired force.Under the action of the PI controller,the actual force tracks the desired force,and the current is the output of the PI controller.Findings–The models built based on the two types of data are separately named as the ANFIS I controller and the ANFIS II controller.The results reveal that the ANFIS I controller possesses the best performance in terms of overshoot,rise time and mean absolute error and show adaptivity to different tracking conditions,including sinusoidal signal tracking and sudden change signal tracking.Originality/value–This paper is the first time to apply the ANFIS to optimize the force tracking control for EHSS.

An Analysis of the Static and Dynamic Behavior of the Hydraulic Compensation System of a Multichannel Valve

Electro-hydraulic proportional valve is the core control valve in many hydraulic systems used in agricultural and engineering machinery.To address the problem related to the large throttling losses and poor stability typically associated with these valves,here,the beneficial effects of a triangular groove structure on the related hydraulic response are studied.A mathematical model of the pressure compensation system based on the power-bond graph method is introduced,and the AMESim software is used to simulate its response.The results show that the triangular groove structure increases the jet angle and effectively compensates for the hydrodynamic force.The steady-state differential pressure at the valve port of the new pressure compensation structure was 0.65 MPa.Furthermore,experimental results show that the pressure difference at the main valve port is 0.73 MPa,and that the response time is less than 0.2 s.It is concluded that the new compensation structure has good pressure compensation response characteristics.

Self Adjusting Feedforward Compensation Tracking Control for Proportional Valve Controlled Motor

Aim Aiming at the position tracking control for valve controlled motor electrohydraulic proportional servo systems mainly driving the static load torque, the tracking performance was studied in the presence of the variable gain and deadzone. Methods On the basis of conventional composite control with the deadzone compensation method, a comprehensive control approach with the deadzone and self adjusting feedforward compensation was proposed. Results Experimental results showed that the good tracking performance was achieved for the sinusoidal and constant velocity position tracking under a wide variations of load torque. Conclusion The position tracking accuracy for valve controlled motor electrohydraulic proportional servo systems has been solved by using the comprehensive control approach with the deadzone and self adjusting feedforward compensation.

Applicahon of a Simplified Model Reference Adaptive Algorithm

The application of a simplifed model reference adaptive control(SMRAC) on a typical Pump controlled motor electrohydraulic servo system is studied here. The algorithm of first-order scalar SMRAC ac second-order vector SMRAC are derived. Computer simulations of the algorithms are presented. Experimental results prove that the method of control adopted here perform satisfactorily over a wide range of operating conditions.

Precision Point to Point Control of Proportional Valve Controlled Motor with a Time Varying Load

Aim In accordance with the positioning control for valve controlled motor electrohydraulic proportional servo systems driving the static load torque, the positioning performance was studied in the presence of the time? varying deadzone and gain. Methods The large positioning errors caused by the time varying deadzone were significantly reduced by using the dynamic compensation method for the deadzone; and the large overshoot caused by the time varying gain were dramatically reduced by using the three section intelligent control schemes. Results Experimental results demonstrated that the positioning performance of rapid response, high accuracy and smaller or even no overshoot was achieved under a wide variations of load torque. Conclusion The good positioning performance for valve controlled motor servo systems has been achieved in the presence of the time varying deadzone and gain.

Application of Fuzzy Modification Strategy in MRAC

Based on a simplified model reference adaptive control(SMRAC) algorithm a parameter modification algorithm according to fuzzy laws is proposed in this paper. The method makes the adaptive parameters in SMRAC only rely on the status of performance error. Thus it eliminates the influences of gain coefficients in SMRAC and the amplitude of input signal on the dynamic characteristics. Experiments on various step amplitudes and loads show that the performances of SMRAC are improved by incorporating fuzzy modification method.

A Study on the Static Characteristics of Typical Composite High Speed On-Off Valves

Natural properties of high speed on-off valves can be described through their on-off behavior and spool movement (static and oscillating) characteristics. High speed on-off valves can be combined with actuators in systems into four typical types of composite valves whose static characteristics are related not only to the structures of the single valves and the composite ones, but also to the PWM control modes. It is proved that the composite valves have similar features as those of servo valves. The nonlinear specific properties of single valves composited can be completely compensated by the suitable PWM control modes.

Endoscopic extraction of large common bile duct stones:A review article

Since therapeutic endoscopic retrograde cholangiopancreatography replaced surgery as the first approach in cases of choledocolithiasis,a plethora of endoscopic techniques and devices appeared in order to facilitate rapid,safe and effective bile duct stones extraction.Nowadays,endoscopic sphincterotomy combined with balloon catheters and/or baskets is the routine endoscopic technique for stone extraction in the great majority of patients.Large common bile duct stones are treated conventionally with mechanical lithotripsy,while the most serious complication of the procedure is "basket and stone impaction" that is predominately resolved surgically.In cases of difficult,impacted,multiple or intrahepatic stones,more sophisticated procedures have been used.Electrohydraulic lithotripsy and laser lithotripsy are performed using conventional mother-baby scope systems,ultra-thin cholangio-scopes,thin endoscopes and ultimately using the novel single use,single operator SpyGlass Direct Visualization System,in order to deliver intracorporeal shock wave energy to fragment the targeted stone,with very good outcomes.Recently,large balloon dilation after endoscopic sphincterotomy confirmed its effectiveness in the extraction of large stones in a plethora of trials.When compared with mechanical lithotripsy or with balloon dilation alone,it proved to be superior.Moreover,dilation is an ideal alternative in cases of altered anatomy where access to the papilla is problematic.Endoscopic sphincterotomy followed by large balloon dilation represents the onset of a new era in large bile duct stone extraction and the management of "impaction" because it seems that is an effective,inexpensive,less traumatic,safe and easy method that does not require sophisticated apparatus and can be performed widely by skillful endoscopists.When complete extraction of large stones is unsuccessful,the drainage of the common bile duct is mandatory either for bridging to the final therapy or as a curative therapy for very elderly patients with short life expectancy.Placing of more than one plastic endoprostheses is better while the administration of Ursodiol is ineffective.The great majority of patients with large stones can be treated endoscopically.In cases of unsuccessful stone extraction using balloons,baskets,mechanical lithotripsy,electrohydraulic or laser lithotripsy and large balloon dilation,the patient should be referred for extracorporeal shock wave lithotripsy or a percutaneous approach and finally surgery.

Efficacy of pancreatoscopy for pancreatic duct stones:A systematic review and meta-analysis

BACKGROUND Pancreatic duct stones can lead to significant abdominal pain for patients.Per oral pancreatoscopy(POP)-guided intracorporal lithotripsy is being increasingly used for the management of main pancreatic duct calculi(PDC)in chronic pancreatitis.POP uses two techniques:Electrohydraulic lithotripsy(EHL)and laser lithotripsy(LL).Data on the safety and efficacy are limited for this procedure.We performed a systematic review and meta-analysis with a primary aim to calculate the pooled technical and clinical success rates of POP.The secondary aim was to assess pooled rates of technical success,clinical success for the two individual techniques,and adverse event rates.AIM To perform a systematic review and meta-analysis of POP,EHL and LL for management of PDC in chronic pancreatitis.METHODS We conducted a comprehensive search of multiple electronic databases and conference proceedings including PubMed,EMBASE,Cochrane,Google Scholar and Web of Science databases(from 1999 to October 2019)to identify studies with patient age greater than 17 and any gender that reported on outcomes of POP,EHL and LL.The primary outcome assessed involved the pooled technical success and clinical success rate of POP.The secondary outcome included the pooled technical success and clinical success rate for EHL and LL.We also assessed the pooled rate of adverse events for POP,EHL and LL including a subgroup analysis for the rate of adverse event subtypes for POP:Hemorrhage,post-endoscopic retrograde cholangiopancreatography pancreatitis(PEP),perforation,abdominal pain,fever and infections.Technical success was defined as the rate of clearing pancreatic duct stones and clinical success as the improvement in pain.Randomeffects model was used for analysis.Heterogeneity between study-specific estimates was calculated using the Cochran Q statistical test and I2 statistics.Publication bias was ascertained,qualitatively by visual inspection of funnel plot and quantitatively by the Egger test.RESULTS A total of 16 studies including 383 patients met the inclusion criteria.The technical success rate of POP was 76.4%(95%CI:65.9-84.5;I2=64%)and clinical success rate was 76.8%(95%CI:65.2-85.4;I2=66%).The technical success rate of EHL was 70.3%(95%CI:57.8-80.3;I2=36%)and clinical success rate of EHL was 66.5%(95%CI:55.2-76.2;I2=19%).The technical success rate of LL was 89.3%(95%CI:70.5-96.7;I2=70%)and clinical success rate of LL was 88.2%(95%CI:66.4-96.6;I2=77%).The incidence of pooled adverse events for POP was 14.9%(95%CI:9.2-23.2;I2=49%),for EHL was 11.2%(95%CI:5.9-20.3;I2=15%)and for LL was 13.1%(95%CI:6.3-25.4;I2=31%).Subgroup analysis of adverse events showed rates of PEP at 7%(95%CI:3.5-13.6;I2=38%),fever at 3.7%(95%CI:2-6.9;I2=0),abdominal pain at 4.7%(95%CI:2.7-7.8;I2=0),perforation at 4.3%(95%CI:2.1-8.4;I2=0),hemorrhage at 3.4%(95%CI:1.7-6.6;I2=0)and no mortality.There was evidence of publication bias based on funnel plot analysis and Egger’s test.CONCLUSION Our study highlights the high technical and clinical success rates for POP,EHL and LL.POP-guided lithotripsy could be a viable option for management of chronic pancreatitis with PDC.

An Experimental Study on Microcomputer Control of Pump Controlled Motor Systems

Pump controlled motor electrohydraulic servo systems are much used in circumstances where high power drive is needed. This kind of system has the advantage of energy-saving. But, it also has some defects that have to be improved. Microcomputer control of a pump controlled motor electrohydraulic servo system is studied. A PID controller is first adopted on the closed loop control system, and experimental results are obtained. Then, a model reference adaptive controller is designed and realised on the same system applying a single board microcomputer. Experimental results show that the dynamic properties of the adaptive control system is much better than those of the PID system under different inertia load conditions.

HIGH-ACCURACY SYNCHRONIZA-TION CONTROL WITH HYBRID NEURAL NETWORKS

A novel nonlinear control algorithm based on hybrid neural networks ispresented to cope with the high-accuracy synchronization control problem for a dual-actuatorelectrohydraulic drive system which plays an important role for the development of elastomericlaunchers. A new objective function for better synchronization performance is introduced and alearning algorithm to adjust the weights of the neural network, based on the gradient descentalgorithm, is also derived. The hybrid neural network control algorithm guarantees high-accuracysynchronization performance of two motion cylinders and fast dynamic response as well as goodstability of the control system. Prototype test results on the dual-actuator electrohydraulic drivesystem verifys the effectiveness of the proposed approach.