1. Introduction

This introductory chapter first defines the key terminology “oscillatory-base manipulator,” which represents a model system associated with mechanical systems installed on the oscillatory base. This category consists of two groups depending on the presence or the absence of external oscillatory disturbance. Typical examples with external oscillatory disturbance can be found in marine mechanical systems, such as offshore cranes, drill ships. The other group, i.e., with no external oscillatory disturbance, mainly contains space robots mounted on the flexible base. This monograph will focus on the former group of marine mechanical systems. We introduce related works and our own research history where the \(\mathcal {H}_\infty \) control framework and the sliding-mode control one have played important roles, and present the organization of the monograph.