• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1864-1869
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• 2003

A novel piezoelectric micropump using active check valves in place of conventional passive check valves in inlet and outlet has been proposed and investigated. It actively controls open/close motion of check valves using piezoelectric actuator for expansion/contraction of pump chamber. In this paper, bi-directional flow characteristics and load characteristics are experimentally investigated using an adequate timing control for valve closing motion with a prototype micropump fabricated with the effective size of $17{\times}8{\times}11mm^{3}$. From the experimental results, it is ascertained that optimal values of phase shift against voltage to drive pump chamber for realization of a miniaturized but powerful micropump, are $15^{\circ}$ in inlet check valve and $195^{\circ}$ in outlet. Based on the obtained results, a sheet-type active shuttle valve that has a unified valve-body for inlet and outlet check valves is proposed. A micropump with the effective size of $10{\times}10{\times}10mm^{3}$ is fabricated and basic characteristics are experimentally investigated.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.3
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• pp.100-107
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• 2001

The main goals of the automotive suspension systems are to isolate roadway unevenness from the tire and to improve vehicle stability. To overcome the performance limitation of the passive systems the active systems which completely replace the passive spring and damper elements with a force generating actuator has been studied. However, application of the system has been limited because it has required a significant amount of power. Recently, alternative systems which retain passive elements but include active elements have been developed to reduce the power required. Those systems are mostly focused on the control system which compresses the spring-damper directly. In this study, a new type of power efficient control system which makes the spring-damper unit slide in side way is studied. After constructing the control system including dynamic modeling and motion control, two types of alternative control systems are compared in view of power consumption and dynamic attitudes such as roll responses as well as heave responses. Also, a half car bond graph model is developed to show clearly the significant differences in performances between two control systems.