In this report, we have studied the positional precision of the end effecter regarding robustness with regards to changes in the system parameters of a 6-axis manipulator that has unstable characteristics. In particular, cooperation of the various axes becomes important for improving the positional precision, and the H-Infinity control method is applied and evaluated by an independent servo-system for each joint. With the designed the H-Infinity controller, not only the system would be made to become robust against parameter fluctuations, but also the disturbance effects would be reduced. As a result, it could be verified by an experiment in which robust, stable positional precision could always be achieved against fluctuations in the moment of inertia caused by changes in the attitude of the arm, and against nonlinear disturbances, such as axis interference, that are characteristic of multi-jointed arms.

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In this report, we have studied the positional accuracy of the end of a manipulator regarding robustness with respect to change s in the system parameters of a 6-axis manipulator that has unstable characteristics. In particular, integration of the various axes becomes important in improving the positional accuracy, and a model matching 2-degrees of the freedom control system using a disturbance observer is applied and evaluated by an independent servo-system for each joint. With this 2-degrees of the freedom control method, the system can be made to be match any nominal model. As a result, it could be verified by an experiment in which robust, stable positional accuracy can always be achieved against fluctuations in the moment of inertia caused by changes in the attitude of the arm, and against nonlinear disturbances, such as axis interference, that are characteristic of multi-joint ed arms.

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Recently, pneumatic flow control valves having high responses have been developed and are being wide-ly used. It is very important to know the characteristics of the valves for structuring pneumatic servo systems. The method for measuring the dynamic characteristics of the valves has yet to be established, because of the difficulty of the unsteady flow rate measurements of the compressible fluids.
In this study, simple methods to measure the input-output characteristics and the frequency characteristic of the flow control valves using an isothermal chamber are proposed. The isothermal chamber is a chamber in which steel wool is stuffed into a normal chamber to make the heat transfer area larger, and could almost simulate an isothermal condition. Therefore, the flow rate could be obtained only by measuring the pressure in the chamber. Two types of servo valves and proportional control valves were tested using the proposed method. At the same time, the spool displacement of the valves were measured. The effectiveness of the proposed method was confirmed by comparing the results obtained from the proposed method and the spool displacement of the valves. In addition, it could be clarified that the frequency response could be measured up to a frequency of 140Hz by this method.

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It is difficult, even for an expert to envisage the frequency response characteristics of pneumatic transmission line systems for an arbitrary terminal condition before the actual calculations are performed, because the equations are very complicated. On the other hand, the graphical method, called the Smith chart, is often used for analyzing frequency response of electric transmission lines, whose characteristics are described by a similar wave equation. Referring to this method, the author proposes a graphical method to calculate the frequency response of pneumatic transmission line systems. The method uses reflection coefficients and mapping. Computer display facilitates understanding of the calculation. The new method provides significant insight for analyzing and designing pneumatic transmission line systems. It becomes easy, even for a beginner, to understand the frequency response of pneumatic transmission line systems.

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