混合重合型サーボ弁を用いた油圧サーボシステムの動特性解析

第1報重合量と特性値の関係

抄録

Generally, the electro-hydraulic servovalve for positioning control in hydraulic servo systems is used as a flow control valve. This system often needs to have dual performance (quick traverse and high accuracy of positioning) for positioning control. Therefore it is desirable that the above-mentioned servovalve has a low flow gain near its neutral spool position.
In order to realize a servovalve with this low flow gain, a hybrid-type servovalve has been newly created. This servovalve has an under lap at the oil supply port and an over lap at the oil return port in the spool valve, and it is possible to have a desirable flow gain near its neutral spool position by combining a suitable under lap and over lap.
When this servovalve is installed in the hydraulic servo system, the time constant of this system is affected by the controlled deviation near the set point in the case of feedback control. So it is necessary to clarify the dynamic characteristics of the hydraulic system installed with this servovalve, and the effect of its lap and the amplitude of input current on the time constant.
The purpose of this paper is to clarify the effect of the lap of the hybrid-type servovalve and the amplitude of input current on the time constant of the hydraulic servo system, and to obtain instruction for the design of this servovalve for practical application.
First, we analyze the relationship between output flow characteristics of the hybrid-type servovalve and the spool displacement, and obtain the dead time component of servovalve. Secondly, we theoretically obtain the transfer function of the hydraulic servo system considering the transfer characteristics of each element of the system, and deduce the effect of the lap on the time constant of the system. Moreover, as a result of the analysis, it becomes clear that the value of time constant is inversely proportional to the amplitude of the input current.