A parallel link mechanism with six degrees of freedom using 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 large driving force. In this research, the basic characteristics are revealed by experiment and theory. In the former report, the characteristics of the hydraulic servo system were considered and a detailed mathematical model was made. The transfer function was obtained by linear approximation, and the frequency response was presented. In this report, a nonlinear simulation is executed based on the detailed mathematical model. The frequency response obtained by the simulation is more accurate than the frequency response obtained by the linear approximation of the former report. It is shown that the amplitude change of the desired value has a big influence on the frequency response. Also, the appearance of the change of each part, and the influence of the nonlinear characteristics are presented. In addition, the experimental result and simulation result to a rectangular wave input coincide in detail.

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A parallel link mechanism with six degrees of freedom using 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 or needs a large driving force. In this research, basic characteristics are revealed by experiment and theory. In the 1st report, the characteristics of the hydraulic servo system was considered, and a detailed mathematical model was made. A transfer function was obtained by linear approximation, and the frequency response was presented. In the 2nd report, nonlinear simulation was executed based on the detailed mathematical model. The frequency response obtained from the simulation agreed well with the experimental result. The appearance of fluctuation in each part was presented, and the influence of nonlinear characteristics was clarified. From this research, the dynamic characteristics between the input and output of one link that comprises a parallel link mechanism were clarified. However, the parallel link mechanism comprises a so-called interaction system where the displacement of one link influences those of other links through the end effector. In this report, the interaction that each link receives from one link is examined by experiment and nonlinear simulation. The appearance of interaction is presented when the input is a rectangular wave or sinusoidal wave. The frequency response of the interaction that each link receives is presented. It is clarified that the amplitude of the reference value for a link and the load mass has a large influence on the frequency response of interaction. It is also presented that Coulomb friction has a big influence on the result.

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This paper deals with the proposal of an electric-pneumatic hybrid drive system composed of an AC servomotor and a pneumatic cylinder type actuator, and its control methods. The rotational movement of the AC servomotor is transformed into the linear movement through a ball screw that is placed in the piston, and this hybrid drive system can be operated in the direction of gravitational force. Three control methods such as a pressure compensated control, a torque control and a hybrid control that combines both control methods are proposed from the view point of the reduction of the driving torque of the AC servomotor. The basic characteristics of the hybrid drive system are investigated by the experiment relating to the three control methods when the inertial mass moves vertically upwards and downwards during one cycle. Each control method is effective in reducing the driving torque of the AC servomotor and the views on the reduction of the driving torque of the AC servomotor in each control method are described.

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