Robot automation is a growing interest in both, research and industry, resulting in exponential growth of robot integration in factories. In machining processes, industrial robots can be more economical for machining workpieces with complicated sculpted geometry and large dimensions. They are cheaper than CNC machining centers, yet they offer the same operational volume and can be easily integrated into an existing production flow due to their simpler setup. Industrial robots cannot, however, be used in all machining applications because their structural stiffness is typically 50 times lower than that of the CNC machine centers. Their low structural stiffness amplifies vibrations when the robot moves or cuts, which degrade machining accuracy, tool life, and performance. Consequently, the vibrations in robot manufacturing machines should be mitigated in order to satisfy the automation performance pursued by the industries. This study focuses on suppressing robot’s vibration using vibration absorbers, which have been mainly applied to buildings, bridges, and machine tools. The novelty of the final proposed designs lays in the ability to mitigate vibrations in 2 degrees of freedom, and having a range of natural frequencies that can be adjusted smoothly and instantly, through electro-permanent magnets. The goal of this study is to investigate the feasibility of several concept designs of semi-active vibration absorbers, mainly with simulation and partially with experiments. Experimental modal analysis was conducted to different joint configurations of the Kuka KR6 R900-2 robot arm to study the range of its varying resonance frequencies and to help define the appropriate frequency range for the absorbers. Several proposed absorber designs were simulated to estimate the range of their natural frequencies, while others were prototyped, and their ranges of natural frequencies were investigated experimentally. This study concluded that the proposed semi-active vibration absorbers based on electro-permanent magnets can be applied to large robots with a larger load capacity. This contribution can minimize the dimensional form errors in robot machining, enhance the cutting tool life, allow for a higher material removal rate, mitigate the noise, and decrease the energy consumption.
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