A variable viscous damper using electrorheological fluid is developed to suppress vibrations of industrial robots. An integrated system consisting of drive motor, harmonic drive, arm linkage, and electrorheological (ER) damper is experimentally measured, and it is found that the resonant/antiresonant phenomenon is effectively reduced by increasing the viscosity of the ER damper. A position control system based on the conventional semi-closed-loop control with this new type of ER damper is analyzed, and the relationship between the properties of the control system and the ER damping coefficient is discussed by means of pole-assignment technique. It is shown from analysis and experiment that the ER damper contributes both to vibration suppression and disturbance rejection.
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