A parallel link mechanism with six degrees of freedom using six electrohydraulic servo cylinders has large rigidity and support power. This feature is widely used for a driving device with multi degrees of freedom that has a heavy load and needs a large driving force. However, the research concerning the dynamic characteristics of this mechanism is scarce. This research aims at the systematic experimental and the theoretical analysis of the basic characteristics. A detailed mathematical model was made, and a transfer function was obtained by linear approximation. The desired signal that drives one servo cylinder is a sinusoidal wave, and the signals that drive the other five cylinders are constant value, respectively. The frequency response was measured. The calculation results coincide well with the experimentalresults.

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In the previous papers, it was clarified that the application of the dither signal into a hydraulic servomotor position control system using a Neural Network is effective in reducing the steady error. On the other hand, the results of the transient characteristics were not satisfied, when the step input signal is provided. In this report, methodology, which improves by cooperation between the reference model and a delay element, is proposed. The suitable non-dimensional dead time can be analytically obtained from simulated response waves in a state feedback control system. As a result, it is experimentally verified that the position over-shoots and errors can be minimized if the dead time is appropriately chosen. Furthermore, the effectiveness is certainly confirmed even though the experimental parameters, such as supply pressure, load inertia, and setting angular position input are varied.

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