Dynamic Performance of High Speed Solenoid Valve with Parallel Coils

The methods of improving the dynamic performance of high speed on/off solenoid valve include increasing the magnetic force of armature and the slew rate of coil current, decreasing the mass and stroke of moving parts. The increase of magnetic force usually leads to the decrease of current slew rate, which could increase the delay time of the dynamic response of solenoid valve. Using a high voltage to drive coil can solve this contradiction, but a high driving voltage can also lead to more cost and a decrease of safety and reliability. In this paper, a new scheme of parallel coils is investigated, in which the single coil of solenoid is replaced by parallel coils with same ampere turns. Based on the mathematic model of high speed solenoid valve, the theoretical formula for the delay time of solenoid valve is deduced. Both the theoretical analysis and the dynamic simulation show that the effect of dividing a single coil into N parallel sub-coils is close to that of driving the single coil with N times of the original driving voltage as far as the delay time of solenoid valve is concerned. A specific test bench is designed to measure the dynamic performance of high speed on/off solenoid valve. The experimental results also prove that both the delay time and switching time of the solenoid valves can be decreased greatly by adopting the parallel coil scheme. This research presents a simple and practical method to improve the dynamic performance of high speed on/off solenoid valve.

High Speed On/Off Valve Control Hydraulic Propeller

The work-class remotely-operated-underwater-vehicles（ROVs） are mainly driven by hydraulic propulsion system,and the effeciency of hydraulic propulsion system is an important performance index of ROVs.However,the efficiency of traditional hydraulic propulsion system controlled by throttle valves is too low.Therefore,in this paper,for small and medium ROVs,a novel propulsion system with higher efficiency based on high speed on/off valve control hydraulic propeller is proposed.To solve the conflict between large flow rate and high frequency response performance,a two-stage high speed on/off valve-motor unit with large flow rate and high response speed simultaneously is developed.Through theoretical analysis,an effective fluctuation control method and a novel pulse-width-pulse-frequency-modulation（PWPFM） are introduced to solve the conflict among inherently fluctuation,valve dynamic performance and system efficiency.A simulation model is established to evaluate the system performance.To prove the advantage of system in energy saving,and test the dynamic control performance of high speed on/off valve control propeller,a test setup is developed and a series of comparative experiments is completed.The smimulation and experiment results show that the two-stage high speed on/off valve has an excellent dynamic response performance,and can be used to realize high accuracy speed control.The experiment results prove that the new propulsion system has much more advantages than the traditional throttle speed regulation system in energy saving.The lowest efficiency is more than 40%.The application results on a ROV indicate that the high speed on/off valve control propeller system has good dynamic and steady-state control performances.Its transient time is only about 1 s-1.5 s,and steady-state error is less than 5%.Meanwhile,the speed fluctuation is small,and the smooth propeller speed control effect is obtained.On the premise of good propeller speed control performance,the proposed high speed on/off valve control propeller can improve the effeciency of ROV propulsion system significantly,and provides another attractive ROV propulsion system choice for engineers.

Development of a Novel Parallel-spool Pilot Operated High-pressure Solenoid Valve with High Flow Rate and High Speed

High-pressure solenoid valve with high flow rate and high speed is a key component in an underwater driving system.However,traditional single spool pilot operated valve cannot meet the demands of both high flow rate and high speed simultaneously.A new structure for a high pressure solenoid valve is needed to meet the demand of the underwater driving system.A novel parallel-spool pilot operated high-pressure solenoid valve is proposed to overcome the drawback of the current single spool design.Mathematical models of the opening process and flow rate of the valve are established.Opening response time of the valve is subdivided into 4 parts to analyze the properties of the opening response.Corresponding formulas to solve 4 parts of the response time are derived.Key factors that influence the opening response time are analyzed.According to the mathematical model of the valve,a simulation of the opening process is carried out by MATLAB.Parameters are chosen based on theoretical analysis to design the test prototype of the new type of valve.Opening response time of the designed valve is tested by verifying response of the current in the coil and displacement of the main valve spool.The experimental results are in agreement with the simulated results,therefore the validity of the theoretical analysis is verified.Experimental opening response time of the valve is 48.3 ms at working pressure of 10 MPa.The flow capacity test shows that the largest effective area is 126 mm2 and the largest air flow rate is 2320 L/s.According to the result of the load driving test,the valve can meet the demands of the driving system.The proposed valve with parallel spools provides a new method for the design of a high-pressure valve with fast response and large flow rate.

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.

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.