Electrical discharge machining (EDM) has the capability of machining all conductive materials regardless of hardness, and has the ability to deal with complex shapes. However, the speed and accuracy of conventional EDM are limited by probability and efficiency of the electrical discharges. To improve the machining speed and accuracy, we developed a 3-DOF controlled, high-speed, high-precision, magnetic/piezoelectric hybrid drive actuator. For the actuator, a voice coil motor type of magnetic bearing having a positioning stroke of a few millimeters is used to control the motion of an electrode in the thrust direction in order to speedily maintain a suitable distance from the workpiece. Moreover, two piezoelectric elements having high response speed and high precision are used to achieve the vibration of the electrode in the radial direction in order to immediately remove the debris between the electrode and the workpiece. The positioning performance of the actuator is evaluated through experiments, and the experimental results show that the actuator possesses a positioning resolution of 1μm, a bandwidth of 120Hz and a positioning stroke of 2mm in the thrust direction, and a positioning resolution of 0.05μm, a positioning stroke of 10μm at 1000Hz in the radial directions.
Electrical discharge machining has the capability of machining all conductive materials regardless of hardness, and has the ability to deal with complex shapes. However, the speed and accuracy of conventional EDM are limited by probability and efficiency of the electrical discharges. This paper describes a three degrees of freedom (3-DOF) controlled, wide-bandwidth, high-precision, long-stroke magnetic drive actuator. The actuator can be attached to conventional electrical discharge machines to realize a high-speed and high-accuracy EDM. The actuator primarily consists of thrust and radial magnetic bearings, thrust and radial air bearings and a magnetic coupling mechanism. By using the thrust and radial magnetic bearings, the translational motions of the spindle can be controlled. The magnetic drive actuator possesses a positioning resolution of the order of micrometer, a bandwidth greater than 100Hz and a positioning stroke of 2mm.
In conventional Electrical Discharge Machining (EDM), the speed and accuracy are limited by probability and efficiency of the electrical discharges. To improve the machining speed and accuracy, we developed a high-speed, high-precision, 3-DOF controlled local actuator. For the actuator, a voice coil motor type of magnetic bearing having a positioning stroke of a few millimeters is used to control the motion of an electrode in the thrust direction in order to speedily maintain a suitable distance from the workpiece. Moreover, two piezoelectric devices having high response speed and high precision are used to achieve the vibration of the electrode in the radial directions to immediately remove the debris between the electrode and the workpiece. The positioning performance of the actuator was evaluated through experiments, and the experimental results show that the actuator possesses a positioning resolution of the order of micrometer, a bandwidth greater than 120Hz and a positioning stroke of 2mm.
This paper describes an adaptive control method for a magnetic drive actuator that used for the laser cutting to realize high speed and high accuracy machining. Firstly, a zero bias current method and a nonlinear compensator are examined and used for the actuator. Secondly, an adative control method is presented. Finally, the coefficient of the gap-current-force is estimated and the effectiveness of the presented control method is verified by experiments. The experimental results show that the coefficient of the gap-current-force reduces exponentially depending on the increase in the length of the air gap. By using the adaptive control, the peak-to-peak vibration amplitude of the lens holder is reduced from 1.95um to 1.55um.
This paper describes a precision control method for a magnetic drive actuator used for the laser cutting to realize high speed and high accuracy machining. Firstly, a zero bias current method is applied to drive the electromagnets to achieve a high-precision and long-stroke of the actuator. Secondly, a compensation method of the zero point of the displacement sensors is presented to prevent the generation of the disturbance force produced by the elastic hinges. Finally, the positioning performance of the actuator is evaluated through experiments and the experimental results show that the actuator has a positioning resolution of the order of micrometer, a bandwidth greater than 130Hz, and a positioning stroke of 1mm.
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