| Summary: | 碩士 === 雲林科技大學 === 機械工程系碩士班 === 96 === The purpose of this thesis is to convert an on-off solenoid valve into a proportional valve via self displacement sensing. Accurate position control will be achieved without adding an external displacement sensor.
Exploiting the fact that the coil inductance varies with iron-core position, we apply a sinusoidal signal to the solenoid coil. A capacitor is connected to the coil to form an LC resonant circuit. It is found that if the frequency of the excitation signal is near the resonant frequency of the LC circuit, the core position can be estimated by observing the phase difference between the input and output signals. Two different methods are used for phase detections. The first one employs the Cosine law, and the second utilizes the capture function of a 16-bit microcontroller. The phase angles corresponding to a discrete set of core positions are first established. The iron-core displacement is then detectable by interpolating on these measured data.
Finally, a closed-loop control system is constructed using the 16-bit microcontroller. Real-time testing indicates that a positioning accuracy of 0.03 mm can be achieved over a stroke of 1.5 mm.
Keywords: on-off solenoids, self-sensing, linear actuators, displacement sensors
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