Investigation into the Independent Metering Control Performance of a Twin Spools Valve with Switching Technology-controlled Pilot Stage

In hydraulic area,independent metering control(IMC)technology is an effective approach to improve system efficiency and control flexibility.In addition,digital hydraulic technology(DHT)has been verified as a reasonable method to optimize system dynamic performance.Integrating these two technologies into one component can combine their advantages together.However,few works focused on it.In this paper,a twin spools valve with switching technologycontrolled pilot stage(TSVSP)is presented,which applied DHT into its pilot stage while appending IMC into its main stage.Based on this prototype valve,a series of numerical and experiment analysis of its IMC performance with both simulated load and excavator boom cylinder are carried out.Results showed fast and robust performance of pressure and flow compound control with acceptable fluctuation phenomenon caused by switching technology.Rising time of flow response in excavator cylinder can be controlled within 200 ms,meanwhile,the recovery time of rod chamber pressure under suddenly changed condition is optimized within 250 ms.IMC system based on TSVSP can improve both dynamic performance and robust characteristics of the target actuator so it is practical in valve-cylinder system and can be applied in mobile machineries.

2D SIMPLIFIED SERVO VALVE

A novel pilot stage valve called simplified 2D valve, which utilizes bothrotary and linear motions of a single spool, is presented. The rotary motion of the spoolincorporating hydraulic resistance bridge, formed by a damper groove and a crescent overlap opening,is utilized as pilot to actuate linear motion of the spool. A criterion for stability is derivedfrom the linear analysis of the valve. Special experiments are designed to acquire the mechanicalstiffness, the pilot leakage and the step response. It is shown that the sectional size of thespiral groove affects the dynamic response and the stiffness contradictorily and is also verysensitive to the pilot leakage. Therefore, it is necessary to establish a balance between the staticand dynamic characteristics in deciding the structural parameters. Nevertheless, it is possible tosustain the dynamic response at a fairly high level, while keeping the leakage of the pilot stage atan acceptable level.

Effectiveness and Safety of Moxibustion Robots on Primary Dysmenorrhea:A Randomized Controlled Pilot Trial

Objective To conduct a pilot trial to explore the effectiveness and safety of moxibustion robots in treating primary dysmenorrhea(PD)and evaluate its feasibility in clinic.Methods A total of 70 participants with PD were allocated to either moxibustion robot(MR)group(35 cases)or manual moxibustion(MM)group(35 cases)using computer-generated randomization.One acupoint Guanyuan(CV 4)was selected to receive moxa heat stimulation.Two groups of participants were given 3 menstrual cycles of MM and MR treatment respectively(once a day,5 days a session)and received another 3 menstrual cycles follow-up.The degree of pain was evaluated by short-form McGill pain questionnaire(SF-MPQ)and the symptoms of dysmenorrhea were evaluated by Cox Menstrual Symptom Scale(CMSS).The safety was measured by the occurrence rate of adverse events(AEs),including burns(blisters,red and swollen),itching,bowel changes,menstrual cycle disorder,menorrhagia and fatigue,etc.Results A total of 62 patients completed the trial,32 in MR group and 30 in MM group.Compared with baseline,scores of SF-MPQ and CMSS significantly decreased in both groups(P<0.05),and no significant difference was observed between the two groups in the 3rd and 6th menstrual cycles(P>0.05).The total occurrence rate of AEs in MR group was 2.1%,which was significantly lower than MM group(7.2%,P<0.05).Conclusions MR has the same effect as MM at SF-MPQ and CMSS in patients with PD.However,MR is safer than MM(Trial registration No.ChiCTR1800018236).

Prediction of pilot workload in helicopter landing after one engine failure

This paper presents a method to predict the pilot workload in helicopter landing after one engine failure.The landing procedure is simulated numerically via applying nonlinear optimal control method in the form of performance index,path constraints and boundary conditions based on an augmented six-degree-of-freedom rigid-body flight dynamics model,solved by collocation and numerical optimization method.UH-60 A helicopter is taken as the sample for the demonstration of landing after one engine failure.The numerical simulation was conducted to find the trajectory of helicopter and the controls from pilot for landing after one engine failure with different performance index considering the factor of pilot workload.The reasonable performance index and corresponding landing trajectory and controls are obtained by making a comparison with those from the flight test data.Furthermore,the pilot workload is evaluated based on wavelet transform analysis of the pilot control activities.The workloads of pilot control activities for collective control,longitudinal and lateral cyclic controls and pedal control during the helicopter landing after one engine failure are examined and compared with those of flight test.The results show that when the performance index considers the factor of pilot workload properly,the characteristics of amplitudes and constituent frequencies of pilot control inputs in the optimal solution are consistent with those of the pilot control inputs in the flight test.Therefore,the proposed method provides a tool of predicting the pilot workload in helicopter landing after one engine failure.