Papers by Author: Hong Li Liu

Abstract: Electrochemical micro-machining (ECMM) is a method that utilizes anode dissolution principle to process shaping. In the Electrochemical machining （ECM）of micro-hole, machining precision is an important aspect to measure machining quality of micro-hole. In this paper micro-hole machining is regarded as the research object, effects of many factors such as power supply natures, electrolyte composition, pulse width and pulse frequency on machining accuracy in micro-hole ECM have been evaluated. Research shows that processing accuracy can be improved through using non-linear electrolyte in high frequency, narrow pulse electrochemical machining.

Abstract: Direct torque control (DTC) technology in asynchronous motor is one of new frequency transformation drive technology after the vector control technology. In recent years people begin to apply it to the synchronous motors. This paper introduces the application station of direct torque control in permanent magnet synchronous motor drives, discusses several key problems and analyses its development direction in the future.

Abstract: With the widely use of Permanent Magnet Brushless DC Motor (BLDCM) in many fields, the superiority in the control method of position sensor-less is more and more obvious. In this paper several control methods of position sensor-less for BLDCM are presents, and a novel technique, the method of speed-independent position function, is introduced to detect the rotor position of BLDCM. This method may detect the rotor position from almost zero speed to high speed, and may also give the commutation time.

Abstract: Because the process of blade in electrochemical machining(EMC) can be effected by many factors, such as blade shapes, machining electrical field, electrolyte fluid field and anode electrochemical dissolution, different ECM machining parameters maybe result in great affections on blade machining accuracy. Regard some type of aero-engine blade as research object, five main machining parameters, applied voltage, initial machining gap, cathode feed rate, electrolyte temperature and pressure difference between electrolyte inlet and outlet, have been evaluated and optimized based on BP neural network technique. From 3125 possible machining parameter combinations, 657 optimized parameter combinations are discovered. To verify the validity of the optimized ECM parameter combination, a serial of machining experiments have been conducted on an industrial scale ECM machine, and the experiment results demonstrates that the optimized ECM parameter combination not only can satisfy the manufacturing requirements of blade fully but has excellent ECM process stability.