| Summary: | 碩士 === 中原大學 === 機械工程研究所 === 95 === In recent years, the active magnets suspended platforms are often seen in the mechanism that designed for high-speed, high position precision or low friction, such as micro/nano linear stages, especially. This research was aimed at the controller design for a five degree-of-freedom magnetic levitated platform. The magnetic levitated platform system basically is an unstable system, it is not only a highly nonlinear system, also is a dynamic coupled system. Furthermore, there are four actuators and only three controlled factors in the vertical position of the platform. Therefore, a decoupled structure was proposed to resolve the control question. Based on the decoupled model, we designed a global variable structure controller to decrease the influence of the load changes and reduce the system vibration, and promote the positioning precision. Moreover, a saturation function was added to controller to form a sliding layer and to eliminate the chatter phenomenon. The experimental results showed the suspension precision was about less 1 �慆 as the load changed from 10kg to 30kg.
In the power amplifier, this research used the pulse width modulation technique to design a switched current driver design for the electric magnets of magnetic suspension system. Dye to the phenomenon of the MOSFET, the driver can operate in the great voltage and under the bigger electric currents than the traditional push-pull linear driver. Furthermore, the relationship of the force slew rate and the supply voltage are proposed.
The driver is composed of the interior loop control circuit of the proposed driver made by the operational amplifier, the two-quadrant chopper, and the three-level PWM controller. The experimental results show the proposed driver better than the traditional push-pull linear driver in the response rate, the system bandwidth, the transition response as well as the low current distortion. The experimental results also shown the system bandwidth of the proposed driver may reach several kHz under the different loading condition.
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