Vibration suppression control of robot arms using a homogeneous-type electrorheological fluid

A variable viscous damper using electrorheological (ER) fluid is developed to suppress torsional vibration of industrial robot. An integrated system consisting of drive motor, harmonic drive, arm linkage and ER damper was measured experimentally and found to be able to reduce the resonance/antiresonance phenomenon by increasing the viscosity of ER damper. A position control system, which is based on both the conventional semi-closed loop control and this new type ER damper, is analyzed and the relation between the ER damping coefficient and the bandwidth of the system is discussed using pole assignment technique. It is shown that the ER damper provides both vibration suppression and disturbance rejection.