Yukihiro Kusumoto

Energy-optimal gait analysis of quadruped robots

It is important for walking robots such as quadruped robots to have an efficient gait. Since animals and insects are the basic models for most walking robots, their walking patterns are good examples. In this study, the walking energy consumption of a quadruped robot is analyzed and compared with natural animal gaits. Genetic algorithms have been applied to obtain the energy-optimal gait when the quadruped robot is walking with a set velocity. In this method, an individual in a population represents the walking pattern of the quadruped robot. The gait (individual) which consumes the least energy is considered to be the best gait (individual) in this study. The energy-optimal gait is analyzed at several walking velocities, since the amount of walking energy consumption changes if the walking velocity of the robot is changed. The results of this study can be used to decide what type of gait should be generated for a quadruped robot as its walking velocity changes.

High precision polishing robot using a learning-based surface following controller

In this paper, a high precision polishing robot with a learning-based surface following controller is proposed for polishing PET (poly ethylene terephthalate) bottle molds with curve surface. The shape of a mounted abrasive tool, attached to the tip of the robot arm, is a ball-end type. When a PET bottle mold with a large curvature is polished, not only the orientation of the mounted abrasive tool is fixed but also its revolution is locked. The motion of the mounted abrasive tool is feedforwardly controlled based on initial trajectory calculated in advance. The trajectory is generated by cutter location data constituted from a CAM system. The trajectory is modified through the process of actual polishing. The surface is polished by a polishing force acting between the mold and the abrasive tool. The polishing force is assumed to be considered as a composite force of the contact and kinematic friction forces, in which the friction consists of Coulomb and viscous frictions. Velocities in the normal and tangent directions are delicately controlled so that the proposed system is effective for obtaining a polishing surface as achieved by skilled workers.

New finishing system for metallic molds using a hybrid motion/force control

In this paper, a finishing system with a mounted abrasive tool is proposed for polishing of metallic molds. The shape of the mounted abrasive tool is a ball-end type. When a metallic mold with curved surface is polished, not only the orientation of the mounted abrasive tool is fixed but also its revolution is locked. The motion of the mounted abrasive tool is feedforward controlled based on an initial trajectory calculated in advance. The surface is polished by the polishing force which consists of a contact force, motion and viscous friction forces acting between the mold and tool. In this case, the velocities in the normal and tangent directions are delicately regulated so that the polishing force can track the desired value. The effectiveness of the proposed system is proved by experiments using an industrial robot with a PC based controller.

Generation of normalized tool vector from 3-axis CL data and its application to a mold polishing robot

Cutter location (CL) data with normal vectors can be used for not only a desired trajectory of tools translational motions but also a desired force direction for molds. In this paper, such normalized tool vectors from 3-axis CL data are generated for a polishing robot. The resultant CL data allow the polishing robot based on an industrial robot to realize a teaching-less operation of position and force. The present robot can also control the polishing force consisting of the contact and kinetic friction forces. During the polishing of a mold, a position feedback loop has a delicate contribution to the force feedback loop in Cartesian space so as not to make the tool deviate from the desired trajectory. The effectiveness and validity of the proposed robot have been proved by actual polishing experiments using an aluminum mold with curved surface.

An open-architecture-based hybrid control method with a weak coupling between position feedback-loop and force feedback-loop (application to a mold polishing robot)

Cutter location (CL) data with normal vectors can be used for not only a desired trajectory of tools translational motion but also desired force directions for a mold polishing robot. In this paper, such normalized tool vectors are systematically generated from 3-axis CL data. The resultant CL data allow the polishing robot with an abrasive tool to realize a teaching-less operation of position and force. The present robot can also control the polishing force consisting of the contact and kinetic friction forces. During the polishing of a mold, a position feedback loop has a delicate contribution to the force feedback loop in Cartesian space so that a stable force control and an accurate pick feed control can be simultaneously achieved. The effectiveness and validity of the proposed robot have been proved by actual polishing experiments using a duralumin mold with curved surface.