Abstract
A novel redundantly actuated parallel robot for mold polishing work is proposed. Cogging-less direct drive motors are implemented in the prototype. Instead of using conventional spherical sliding bearings, ball bearings with appropriate preload are implemented in the rolling pairs of the prototype. These mechanical parts enable fine force control for mold polishing work. The rated force of the robot perpendicular to the surface on the workpiece is 20 N with a tangential force of 5 N, which enable the robot to execute polishing tasks as well as skilled workers. In addition, the polishing velocity along the tangential direction is 60 m/min, which exceeds skilled workers’ velocity of 10 m/min. High speed feed contributes to reducing the polishing force and improving the quality of the surface of the mold. Kinematics, statics, dynamics and control of redundantly actuated parallel robot are discussed in this paper. Impedance control was implemented to the prototype for stably executing the mold polishing work.
Highlights
In the mold polishing work, operator oscillates a stick type grinding stone on the surface of the work piece by hand at approximately speed of 10 m/min, with from 20 N to 30 N, up to 50 N contacting force
There have been a lot of requests for automating this heavy work, and several researches for automating the mold polishing work using industrial robot manipulators[1,2,3,4,5]
Conventional researches polishing by industrial robot use rotating polishing tools for increasing the polishing speed
Summary
In the mold polishing work, operator oscillates a stick type grinding stone on the surface of the work piece by hand at approximately speed of 10 m/min, with from 20 N to 30 N, up to 50 N contacting force. Industrial robot, consisted by serial mechanisms include heavy motors, has large effective mass at the tip, that disturbs high speed oscillating motion for mold polishing. The characteristics of the finished surface by the rotating polishing tool is differs from that by the human operator using stick grinding stone by hand. Parallel robots have sufficient speed for the mold polishing tasks These robots are not suitable when the robots contact their environment because almost all parallel robots are aimed not for force control but for position control
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