A new single-axis gas thermal gyroscope without proof mass is presented in this paper. The device was designed, manufactured and experimentally characterized. The obtained results were compared to numerical simulation. The working principle of the gyroscope is based on the deflection of a laminar gas flow caused by the Coriolis effect. A bidirectional hot air flow is generated by alternating activation of two suspended resistive micro-heaters. The heated gas is encapsulated in a semi-open cavity and the gas expands primarily inside the cavity. The thermal expansion gyroscope has a simple structure. Indeed, the device is composed of a micromachined cavity on which three bridges are suspended. The central bridge is electrically separated into two segments enabling to set up two heaters which may be supplied independently from each other. The two other bridges, placed symmetrically on each side of the central bridge, are equipped with temperature detectors which measure variations in gas temperature. The differential temperature depends on the rotational velocity applied to the system. Various parameters such as the heating duty cycle, the type of the gas and the power injected into the heaters have been studied to define the optimal working conditions required to obtain the highest level of sensitivity over a measurement range of around 1000°/s. The robustness of the device has also been tested and validated for a shock resistance of 10,000 g for a duration of 400 µs.
In the last years at ISL a lot of work has been performed in order to develop and install highly flexible pulse forming networks (PFN), based on capacitors as energy source for electric guns (railgun, ETC-gun).For the 10 MJ-railgun PEGASUS a modular pulse power supply was set up, which consists of 200 pulse forming units. The pulse forming units are completely switched by semiconducting devices (thyristors, diodes).In order to remove some of the disadvantages of this PFN, a novel PFN also based on semiconductor switches is proposed. This novel PFN also consists of several units. The principle for each of them is the application of a high-power rectifier as switching element. Thanks to the rectifier and to the particular behavior of the applied SCR which will be switched off as soon the current is below its holding current, the current yielded by the pulse forming units can be turned off.Besides this, by triggering the single pulse forming units configuring the PFN with different time delays, it becomes possible to shape a current pulse that is really rectangular and thus very well suited for electric launcher applications.Due to the current turn-off capability it is feasible to reduce the shot-out current for the railgun to a small value. Simulations with the P-Spice code have shown that by applying the novel PFN the efficiency of a railgun can be enhanced by about 10%.By arranging the rectifier in a sophisticated manner the SCR can be integrated into the rectifier. Thus the whole switching element of the novel pulse forming unit can be set up with four semiconducting switches only, which can all be assembled in the same clamping device. The result is a rather compact set-up.In this paper the principle of the novel pulse forming unit will be shown and discussed. Besides this, a first prototype will be presented together with its electrical features. A PFN consisting of four units was built and investigated. First experiments with this PFN were performed, while the discharge was made into a dummy load. The high flexibility of this pulse power supply will be shown, concerning the shaping of different current pulses and the turn-off capability.Finally results obtained by P-Spice simulation with a real railgun load will be presented. The results show the feasibility of using the rectifier-based PFN to drive an electric launcher. Due to the current turn-off capability and the highly modular design an efficiency enhancement could be demonstrated.
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