In order to investigate the problems related to soil and construction machinery, such as a hydraulic excavator, an understanding of the physical interactions between the soil and the machine is essential. The purpose of this study is to experimentally examine actual excavation processes by observing a variety of physical parameters, with the aim of realizing intelligent excavation machinery whose performance is not only to be automated but also optimized in terms of specific task criteria such as, energy consumption, operation time and excavation trajectory. In the previous three reports, we measured and analyzed excavation processes from the viewpoint of force interactions. In this article, we developed an automated excavator based on the knowledge acquired through the previous study and investigated essential factors for intelligent excavation machinery. As the final report of this study, we discussed how intelligent machinery should be realized from a design theoretic point of view.