In a traditional 1-level pressure valve-controlled hydraulic servo system, the response is good, but the efficiency is deteriorated. In a load-sensing pump-controlled hydraulic servo system, the efficiency is good, but it is desired that the response be improved. Therefore, an N-level pressure hybrid power supply has been proposed to realize high efficiency and high response simultaneously in the 1st report, and its high efficiency has been verified by experiments of a 2-level pressure valve-controlled hydraulic servo system. In this paper, a separated type N-level pressure hybrid power supply is described in detail. A 2-level pressure valve-controlled hydraulic servo system using separated type power supply is used to conduct the experiments. Power consumption of the system is also measured. It is verified that the efficiency of the system using a separated type power supply is not only higher than the traditional system, but also the response of the system is as good as the traditional system under the frequency of 20Hz.

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It is well known that the amplitude of pressure pulsation becomes extremely high when the frequency of the pump rotational speed coincides with the resonant frequency of the pressure pulsation standing waves. In the previous report, the authors investigated the relationship between the resonant modes of the standing wave arising in the connecting pipe and the termination characteristics of the hydraulic circuit. Although the influence of the two terminations, a restrictor and volume, on the resonant modes was clarified, the termination impedance contains only a real number or a purely imaginary number in terms of the complex characteristic. In this report, a further investigation of the influence of the complex parameters of termination impedance characteristics is undertaken. In particular, the non-dimensional pressure pulsation in the connecting pipe is examined by the numerical calculation to understand the resonant phenomena of a standing wave for the complex parameters of termination impedance. Consequently, the transition of the resonant mode between the “both ends closed” mode and the “pump end closed and termination end opened” mode is confirmed. The characteristics of the transition resonant mode are clarified, and it is found that pressure pulsation also becomes extremely high under the transition resonant mode conditions.

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