In this study, the effect of traverse speed on abrasive waterjet machining (AWJM) of Inconel 718 nickel-based superalloy was experimentally investigated. In the experiments, six different traverse speeds of 80, 130, 180, 230, 280, and 330 mm/min were employed. Following the tests, the surface roughness of the machined job, the kerf taper ratio, and kerf wideness were measured. The characteristics of machined surface were also investigated using scanning electron microscope (SEM) and atomic force microscope (AFM). As a consequence, it is observed that the surface roughness and kerf taper ratio tended to increase with traverse speed, while kerf wideness decreased.

This paper presents mechatronic design and hierarchical locomotion control of a biomimetic robotic fish for three-dimensional swimming modes. Inspired by biological features of Lamprey, a closed loop sensory feedback Central Pattern Generator (CPG) model is adapted to hierarchical control mechanism in order to provide robust and effective biomimetic control structure. A sensory feedback mechanism plays an important role to react external stimuli from environment. In addition, a closed loop fuzzy logic control structure is developed as a brain model to decide adaptive swimming modes according to sensory information. In order to provide three-dimensional motion abilities, the Centre of Gravity (CoG) control mechanism is designed and controlled by a back-forth proportional control structure. Experimental results are obtained to prove the CPG-based closed loop sensory feedback control structure with the developed robotic fish prototype.