Switching Frequency Improvement of a High Speed on/off Valve Based on Pre-excitation Control Algorithm

The high-speed on/off valve(HSV)serves as the fundamental component responsible for generating discrete fluids within digital hydraulic systems.As the switching frequency of the HSV increases,the properties of the generated discrete fluid approach those of continuous fluids.Therefore,a higher frequency response characteristic of HSV is the key to ensure the control accuracy of digital hydraulic systems.However,the current research mainly focuses on its dynamic performance,but neglect its FRC.This paper presents a theoretical analysis demonstrating that the FRC of the HSV can be enhanced by minimizing its switching time.The maximum switching frequency(MSF)is mainly determined by opening dynamic performance when HSV operates with low switching duty ratio(SDR),whereas the closing dynamic performance limits the MSF when HSV operates with high SDR.Building upon these findings,the pre-excitation control algorithm(PECA)is proposed to reduce the switching time of the HSV,and consequently enhance its FRC.Experimental results demonstrate that PECA shortens the opening delay time of HSV by 1.12 ms,the closing delay time by 2.54 ms,and the closing moving time by 0.47 ms in comparison to the existing advanced control algorithms.As a result,a larger MSF of 417 Hz and a wider controllable SDR range from 20%to 70%were achieved at a switching frequency of 250 Hz.Thus,the proposed PFCA in this paper has been verified as an effective and promising approach for enhancing the control performance of digital hydraulic systems.

Efficacy Observation of Pre-Excitation Regimen in the Treatment of Refractory Relapsed Acute Non-Lymphocytic Leukemia

Objective:To explore the clinical effect of applying the pre-excitation regimen in the treatment of patients with refractory relapsed acute non-lymphocytic leukemia(ANLL).Methods:This research work was carried out in our hospital(Shaanxi Provincial People’s Hospital)from September 2021 to September 2022.A total of 50 cases were selected for this study,and all were given a pre-excitation treatment plan,mainly low-dose cytarabine,aclarithromycin,etoposide,granulocyte colony-stimulating factor,and more were implemented.The clinical intervention effect was then analyzed.Results:Among the 50 patients in this study,the results showed that the treatment was very effective for 22 cases,accounting for 44.00%;effective for 14 cases,accounting for 28.00%;and ineffective for 14 cases,accounting for 28.00%.The total rate of effectiveness was 72.00%.The hematopoietic system adverse reactions of the patients were mainly bone marrow suppression.All 50 patients had different degrees of blood count decline,among which some patients’neutrophils were less than 0.5×10^(9)/L.The median time was 7 days.Among them,25 patients had infection problems,the incidence rate was 50.00%,the patient’s platelet count PLT<20×109/L,and the median time was 10 days.At the same time,among the 50 patients in this study,34(68.00%)patients had symptoms such as loss of appetite,nausea,vomiting,and fatigue,17(34.00%)patients showed hair loss,mildly elevated transaminases were observed in 8(16.00%)patients,and 11(22.00%)patients had muscle soreness.Conclusion:In the treatment of patients with refractory complex acute non-lymphocytic leukemia,the application of pre-excitation regimen has a significant effect,which can improve the adverse symptoms of patients,reduce the incidence of adverse reactions,and promote the recovery of patients.

Reversible pre-excitation cardiomyopathy:a case report

This paper reported a 25-year-old hospitalized woman complained of recurrent chest tightness and dyspnea for 3 months.The electrocardiogram showed pre-excitation and the echocardiogram showed left ventricular wall contraction reduced diffusely and moved asynchronously.In the systolic period,the regional septum basal segment moved to the right ventricle like an aneurysm.In cardiac magnetic resonance imaging examination,there was no significant myocardial fibrosis.The patient further had an endomyocardial biopsy and pathological examination showed nonspecific changes,only with mild interstitial edema.After an electrophysiological study,the patient was finally diagnosed with pre-excitation cardiomyopathy with a right anteroseptal para-hisian manifest accessory pathway.Radiofrequency catheter ablation was then performed to block the advanced pathway.6 months after ablation,the left ventricular systolic function and synchrony improved significantly,and the symptoms were alleviated.

Dynamic performance and temperature rising characteristic of a high-speed on/off valve based on pre-excitation control algorithm

High speed on/off valve(HSV)is an essential component in aerospace digital hydraulic systems(ADHS).Dynamic performance and temperature rising characteristic are two important features,which determine the performance of HSV,and affect the response speed and reliability of ADHS.Increasing the driving voltage is an effective method for improving the dynamic performance of HSV.However,continuous high voltage excitation will lead to more wasted energy,higher temperature rising and lower reliability.To solve this problem,a pre-excitation control algorithm(PECA)is proposed in this paper based on the theoretical model of the influence of electrical parameters on dynamic performance and temperature rising characteristics.In PECA,an appropriate initial coil current is generated by pre-excitation instead of increasing driving voltage,which significantly shortens the switching delay time.Then,based on real-time current online calculation and feedback mechanism,the adaptive switching of five equivalent voltages is realized.Consequently,the coil current can be rapidly kept at the expected state without consuming more energy and generating more heat.Results indicate that compared with conventional PWM control algorithm,the PECA can improve dynamic performance of HSV,shorten the total switching time by 71.5%,and increase the maximum operation frequency.Therefore,the linear area of flow characteristic is expended by 80.0%,the adjusting time of HSV-controlled system is reduced by 23%,while shortening steady error by 46.7%.Moreover,the temperature rising characteristics of HSV are better,the maximum operation temperature is reduced by 68.6%,and the time to reach the steady state temperature is shortened by 20%.From the results,it can be concluded that the PECA is not only an effective and practical control algorithm for improving the performance of HSVs and HSV-controlled systems while reducing the heat generation and decreasing the temperature rising of HSV,but also can be a potential solution in ADHS.

Pulmonary vein antrum isolation of pre-excited atrial fibrillation

Background Pulmonary vein antrum isolation （PVAI） of pre-excited atrial fibrillation （AF） is controversial. This study aimed to observe the therapeutic effects of PVAI on pre-excited AF. Methods Twenty-nine patients with pre-excited AF were prospectively divided into a PVAI group （group I, 19 cases） and a control group （group II, 10 cases）. To each case in group I, PVAI was performed, and then electroanatomical mapping of accessory pathways （AP） and ablation were constructed on a three-dimensional （3D） map of the valve annulus. Only AP ablation was performed in each case of group II. Results Of the 29 cases, three were found to have dual APs, two had intermittent APs, and the remaining 24 had single APs. All APs were successfully ablated after the procedure. There were no significant statistical differences in the AP procedure duration （（77.4±21.3） minutes vs. （85.3±13.1） minutes）, the AP ablation time （（204±34） seconds vs. （223±62） seconds） and the AP X-ray exposure time （（18.6±4.4） minutes vs. （19.1±4.5） minutes） respectively between groups I and II. As compared with the control group （5 of 10 cases, 50%）, the PVAI group had a significantly lower AF recurrence rate （2 of 19 cases, 11%; P 〈0.05） during follow-up of （20.5±10.0） months. All seven patients who recurred were successfully abolished by a second ablation. Conclusions In patients with pre-excited AF, PVAI is an effective therapeutic approach with a low AF recurrence rate. 3D electroanatomical maps of AP contributed to the high success rate of ablation without significantly prolonging of operational duration and X-ray exposure time.