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Recently, the so-called simple adaptive control (SAC) techniques have been turned attention because of its high practical control performance in spite of its quite simple control structure. The method is fundamentally applicable to plants which satisfy the so-called almost strictly positive real (ASPR) condition.In this paper, it is shown that, even if the plant contains some kinds of disturbances and nonlinearities and does not satisfy ASPR condition, the control performance can be improved quite well by adding a simple robust adaptive controller to the original SAC algorithm. Effects of such a robust controller are examined by a practical DC servo control equipment.

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A pneumatic actuator outputs large power in proportion to weight and can be installed in an inexpensive, light and compact configuration. From the standpoint of controllability, however, it is weak due to nonlinearity by compression and delayed transfer of air, it has a problem of poor accuracy in position control. To solve such problem, we propose a hydraulic/pneumatic hybrid actuator that has a pneumatic cylinder and hydraulic cylinder in parallel and uses the hydraulic cylinder as damper. We demonstrate that it can be used in practice and structurally applying it to a manipulator with 2-DOF. It also demonstrates that high-speed and stable control can be achieved by applying optimal control method.