The primary focus of this study is to investigate the control strategies of a hybrid system used in hydraulic excavators. First, the structure and evaluation target of hybrid hydraulic excavators are analyzed. Then th...The primary focus of this study is to investigate the control strategies of a hybrid system used in hydraulic excavators. First, the structure and evaluation target of hybrid hydraulic excavators are analyzed. Then the dynamic system model including batteries, motor and engine is built as the simulation environment to obtain control results. A so-called multi-work-point dynamic control strategy, which has both closed-loop speed PI (proportion integral) control and direct torque control, is proposed and studied in the simulation model. Simulation results indicate that the hybrid system with this strategy can meet the power demand and achieve better system stability and higher fuel efficiency.展开更多
In order to find a feasible way to control excavator’s arm and realize autonomous excavation, the dynamic model for the boom of excavator’s arm which was regarded as a planar manipulator with three degrees of freedo...In order to find a feasible way to control excavator’s arm and realize autonomous excavation, the dynamic model for the boom of excavator’s arm which was regarded as a planar manipulator with three degrees of freedom was constructed with Lagrange equation. The excavator was retrofitted with electrohydraulic proportional valves, associated sensors (three inclinometers) and a computer control system (the motion controller of EPEC). The full nonlinear mathematic model of electrohydraulic proportional system was achieved. A discontinuous projection based on an adaptive robust controller to approximate the nonlinear gain coefficient of the valve was presented to deal with the nonlinearity of the whole system, the error was dealt with by robust feedback and an adaptive robust controller was designed. The experiment results of the boom motion control show that, using the controller, good performance for tracking can be achieved, and the peak tracking error of boom angles is less than 4°.展开更多
Fast response and stable torque output are crucial to the performance of electric screw presses. This paper describes the design of a direct torque control （DTC） system for speeding up torque response and reducing t...Fast response and stable torque output are crucial to the performance of electric screw presses. This paper describes the design of a direct torque control （DTC） system for speeding up torque response and reducing the starting current of electric screw presses and its application to the J58K series of numerical control electric screw presses with a dual-motor drive. The DTC drive system encompasses speed control, torque reference control, and switching frequency control. Comparison of the DTC dual-AC induction motor drive with corresponding AC servo motor drive showed that for the J58K-315 electric screw press, the DTC drive system attains a higher maximum speed （786 r/min） within a shorter time （1.13 s） during a 250 nun stroke and undergoes smaller rise in temperature （42.0 ℃） in the motor after running for 2 h at a 12 min-1 strike frequency than the AC servo motor drive does （751 r/min within 1.19 s, and 50.6 ℃ rise）. Moreover, the DTC AC induction motor drive, with no need for a tachometer or position encoder to feed back the speed or position of the motor shaft, enjoys increased reliability in a strong-shock work environment.展开更多
A neural network control scheme with mixed H2/H∞performance was proposed for robot force/position control under parameter uncertainties and external disturbances. The mixed H2/H∞tracking performance ensures both rob...A neural network control scheme with mixed H2/H∞performance was proposed for robot force/position control under parameter uncertainties and external disturbances. The mixed H2/H∞tracking performance ensures both robust stability under a prescribed attenuation level for external disturbance and H2optimal tracking. The neural network was introduced to adaptively estimate nonlinear uncertainties, improving the system’s performance under parameter uncertainties as well as obtaining the H2/H∞tracking performance. The simulation shows that the control method performs better even when the system is under large modeling uncertainties and external disturbances.展开更多
This paper deals with control method related to a wind system operating in stand-alone applications. The stand-alone wind system is composed of three energy transfer subsystems： wind generator subsystem （wind turbin...This paper deals with control method related to a wind system operating in stand-alone applications. The stand-alone wind system is composed of three energy transfer subsystems： wind generator subsystem （wind turbine and electrical generator）, energy storage subsystem, respectively, specific local network subsystem （controlled loads）. This wind power system performs in the same time the maximization of wind energy conversion and the power balance between produced and required power. Three structures of the energy storage subsystem, based on buffer battery operation and/or capacitor voltage control, are discussed. The simulation results show that the proposed stand-alone wind power system ensures a good management of the local energy request. The design of the structures is analyzed in Matlab/Simulink environment, using PowerSim toolbox.展开更多
On the basic of passive damping control, we do modeling and simulating in another approach to improve the vibration alleviating effect, the piezoelectric layer damping （PLD）, which is called active control. The piez...On the basic of passive damping control, we do modeling and simulating in another approach to improve the vibration alleviating effect, the piezoelectric layer damping （PLD）, which is called active control. The piezoelectric damping patches are under control of PID controller （matlab simulating） in voltage defference. Here, we use the software PRO/ENGINEER to design and model a wind turbine blade before using COMSOL to simulate the dynamic motion of the wind turbine blade and its interaction with aerodynamic force of wind in finite element method. Some different models are built-- the original turbine blade and the turbine blade with damping patches on different location and quantity. Then, according to the simulation results, we compare the effects of passive and active damping control, also the effect of patches locations and quantities under different wind speed. This research can provide a direction for future study about ways to decrease vibration of turbine blades.展开更多
This paper proposes the control of a grid side converter under unbalance voltage conditions for wind turbine system. The control technique is designed to operate under unbalance voltage by independent control between ...This paper proposes the control of a grid side converter under unbalance voltage conditions for wind turbine system. The control technique is designed to operate under unbalance voltage by independent control between positive and negative components. The converter will regulate the DC link voltage at the specific value （650 V）. To verify an operation of the proposed control, the simulation is conducted by MATLAB/SIMULINK program. The experiments are conducted on a 5 kW system composed of wind turbine simulator, machine side converter and the propose grid side converter for operation under unbalance voltage. By comparing the simulation experimentation results, it can be shown that the proposed control can be continuously operating through an extremely sag voltage without damage. Moreover the proposed control can deliver power to the grid and regulate DC link voltage under unbalance voltage.展开更多
A flow control system that combined steady Vortex Generator Jets and Deflected Trailing-edge(VGJs-DT) to decrease the low pressure turbine(LPT) blade numbers was presented.The effects of VGJs-DT on energy loss and flo...A flow control system that combined steady Vortex Generator Jets and Deflected Trailing-edge(VGJs-DT) to decrease the low pressure turbine(LPT) blade numbers was presented.The effects of VGJs-DT on energy loss and flow of low solidity low pressure turbine(LSLPT) cascades were studied.VGJs-DT was found to decrease the energy loss of LSLPT cascade and increase the flow turning angle.VGJs-DT decreased the solidity by 12.5%without a significant increase in energy loss.VGJs-DT was more effective than steady VGJs.VGJs-DT decreased the energy loss and increased the flow angle of the LSLPT cascade with steady VGJs.VGJs-DT can use 50%less mass flow than steady VGJs to inhibit the flow separation in the LSLPT cascade.The deflected trailing edge enhanced the ability of steady VGJs to resist flow separation.Overall,VGJs-DT can be used to control flow separation in LPT cascade and reduce the blade numbers of low pressure turbine stage.展开更多
基金Project (No. 2006C11148) supported by the ScienceTechnology Project of Zhejiang Province, China
文摘The primary focus of this study is to investigate the control strategies of a hybrid system used in hydraulic excavators. First, the structure and evaluation target of hybrid hydraulic excavators are analyzed. Then the dynamic system model including batteries, motor and engine is built as the simulation environment to obtain control results. A so-called multi-work-point dynamic control strategy, which has both closed-loop speed PI (proportion integral) control and direct torque control, is proposed and studied in the simulation model. Simulation results indicate that the hybrid system with this strategy can meet the power demand and achieve better system stability and higher fuel efficiency.
基金Project(2003AA430200) supported by the National Hi-Tech Research and Development Program(863) of China
文摘In order to find a feasible way to control excavator’s arm and realize autonomous excavation, the dynamic model for the boom of excavator’s arm which was regarded as a planar manipulator with three degrees of freedom was constructed with Lagrange equation. The excavator was retrofitted with electrohydraulic proportional valves, associated sensors (three inclinometers) and a computer control system (the motion controller of EPEC). The full nonlinear mathematic model of electrohydraulic proportional system was achieved. A discontinuous projection based on an adaptive robust controller to approximate the nonlinear gain coefficient of the valve was presented to deal with the nonlinearity of the whole system, the error was dealt with by robust feedback and an adaptive robust controller was designed. The experiment results of the boom motion control show that, using the controller, good performance for tracking can be achieved, and the peak tracking error of boom angles is less than 4°.
基金Funded by the Natural Science Foundation of Hubei Province (No. 2004AA101E04)
文摘Fast response and stable torque output are crucial to the performance of electric screw presses. This paper describes the design of a direct torque control （DTC） system for speeding up torque response and reducing the starting current of electric screw presses and its application to the J58K series of numerical control electric screw presses with a dual-motor drive. The DTC drive system encompasses speed control, torque reference control, and switching frequency control. Comparison of the DTC dual-AC induction motor drive with corresponding AC servo motor drive showed that for the J58K-315 electric screw press, the DTC drive system attains a higher maximum speed （786 r/min） within a shorter time （1.13 s） during a 250 nun stroke and undergoes smaller rise in temperature （42.0 ℃） in the motor after running for 2 h at a 12 min-1 strike frequency than the AC servo motor drive does （751 r/min within 1.19 s, and 50.6 ℃ rise）. Moreover, the DTC AC induction motor drive, with no need for a tachometer or position encoder to feed back the speed or position of the motor shaft, enjoys increased reliability in a strong-shock work environment.
文摘A neural network control scheme with mixed H2/H∞performance was proposed for robot force/position control under parameter uncertainties and external disturbances. The mixed H2/H∞tracking performance ensures both robust stability under a prescribed attenuation level for external disturbance and H2optimal tracking. The neural network was introduced to adaptively estimate nonlinear uncertainties, improving the system’s performance under parameter uncertainties as well as obtaining the H2/H∞tracking performance. The simulation shows that the control method performs better even when the system is under large modeling uncertainties and external disturbances.
文摘This paper deals with control method related to a wind system operating in stand-alone applications. The stand-alone wind system is composed of three energy transfer subsystems： wind generator subsystem （wind turbine and electrical generator）, energy storage subsystem, respectively, specific local network subsystem （controlled loads）. This wind power system performs in the same time the maximization of wind energy conversion and the power balance between produced and required power. Three structures of the energy storage subsystem, based on buffer battery operation and/or capacitor voltage control, are discussed. The simulation results show that the proposed stand-alone wind power system ensures a good management of the local energy request. The design of the structures is analyzed in Matlab/Simulink environment, using PowerSim toolbox.
文摘On the basic of passive damping control, we do modeling and simulating in another approach to improve the vibration alleviating effect, the piezoelectric layer damping （PLD）, which is called active control. The piezoelectric damping patches are under control of PID controller （matlab simulating） in voltage defference. Here, we use the software PRO/ENGINEER to design and model a wind turbine blade before using COMSOL to simulate the dynamic motion of the wind turbine blade and its interaction with aerodynamic force of wind in finite element method. Some different models are built-- the original turbine blade and the turbine blade with damping patches on different location and quantity. Then, according to the simulation results, we compare the effects of passive and active damping control, also the effect of patches locations and quantities under different wind speed. This research can provide a direction for future study about ways to decrease vibration of turbine blades.
文摘This paper proposes the control of a grid side converter under unbalance voltage conditions for wind turbine system. The control technique is designed to operate under unbalance voltage by independent control between positive and negative components. The converter will regulate the DC link voltage at the specific value （650 V）. To verify an operation of the proposed control, the simulation is conducted by MATLAB/SIMULINK program. The experiments are conducted on a 5 kW system composed of wind turbine simulator, machine side converter and the propose grid side converter for operation under unbalance voltage. By comparing the simulation experimentation results, it can be shown that the proposed control can be continuously operating through an extremely sag voltage without damage. Moreover the proposed control can deliver power to the grid and regulate DC link voltage under unbalance voltage.
基金supported by the National Foundation for Innovative Research Groups of China(Grant No.51421063)
文摘A flow control system that combined steady Vortex Generator Jets and Deflected Trailing-edge(VGJs-DT) to decrease the low pressure turbine(LPT) blade numbers was presented.The effects of VGJs-DT on energy loss and flow of low solidity low pressure turbine(LSLPT) cascades were studied.VGJs-DT was found to decrease the energy loss of LSLPT cascade and increase the flow turning angle.VGJs-DT decreased the solidity by 12.5%without a significant increase in energy loss.VGJs-DT was more effective than steady VGJs.VGJs-DT decreased the energy loss and increased the flow angle of the LSLPT cascade with steady VGJs.VGJs-DT can use 50%less mass flow than steady VGJs to inhibit the flow separation in the LSLPT cascade.The deflected trailing edge enhanced the ability of steady VGJs to resist flow separation.Overall,VGJs-DT can be used to control flow separation in LPT cascade and reduce the blade numbers of low pressure turbine stage.
