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By considering the rapid growth of microcomputer technology, it is now possible to implement various control algorithms into a microcomputer and to use it as a single-loop digital controller. This paper considers a design of a digital controller which achieves an arbitrarily specified closed-loop response. A linear equation is obtained for unknown parameters of such a controller based on series expansions of relevant pulse transfer functions. Some examples are given to show the characteristic features of the method.

As the need for higher efficiency of engineering components increases, so does the demand for functional surfaces. While various tribosurfaces (e.g., texturing and coatings) have been developed, many researches are aimed at static functionality. On the other hand, due to a wide range of environmental adaptability and active control, active-morphing surfaces can be highly efficient and robust. In this paper, we demonstrate a novel morphing surface and its realization using additive manufacturing (AM). By using a diaphragm structure, morphing performance is achieved even if a hard resin material is used. When air pressure is applied to the backside of the diaphragm, it changes to a convex shape, and vice versa. The concept requires a complex structure for arranging airflow and a solid morphing system. The AM is one great technique to create such complex structure. As a result of actual manufacturing, the created morphing structure realizes a large morphing of 600 µm or more. In addition, the shape changes reversibly depending on the air pressure. The surface also exhibits very interesting tribological characteristics. The surface shows a friction coefficient of 0.5-1.7 with a convexity, and then decreases to about 0.3 with a concavity. A real-contact area measurement reveals that the novel property occurs due to change in the real-contact area depending on surface morphology. In conclusion, the present paper provides a new concept of a novel morphing tribosurface, which selectively performs as a low-friction or break-like surface, created using AM.

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