Identifying Viscous Damping and Coulomb Friction in the 12 Meter Truss Actuator

摘要

This report describes a method for measuring the viscous damping and coulombfriction force in a single degree-of-freedom (SDOF) dynamic system. The method is first derived from the steady state frequency response of a SDOF system with an equivalent viscous damping coefficient representing both viscous damping and a coulomb friction force. At resonance, the system response amplitude is a linear function of input force amplitude. The slope of the line is proportional to the viscous damping coefficient while the intercept depends on the friction force and viscous damping. Measured data are fit to a straight line using least squares and the unknown parameters are then extracted from the linear fit. The method is applied to analytical data and the results are very good. Finally, the method is applied to response data from a linear momentum exchange actuator on the 12 meter truss active control experiment. The resulting parameters are compared with an equivalent viscous damping estimate from free decay response. (Author)