A zero-stiffness suspension system featuring a noncircular disk is used as an application in counteracting gravity loads in ground-based structural testing. The dynamic behavior of this mechanism is analyzed in closed form, in which this mechanism is shown to be very sensitive to inertial properties of noncircular disk which can introduce inertial forces to trigger nonlinear dynamic behavior in the system, thereby degrading testing performance under such inertial loading. An adaptive feedforward control law is developed for eliminating these inertial effects upon the suspension system during dynamic testing. Under this control manipulation, the output signals of disk mechanism are regulated and tracked along the desired trajectories so that the error signals can vastly be reduced. Stability of the control system is investigated, and simulated-time histories of test articles under an active band-drive suspension system will also be presented to show the effectiveness of the present approach.
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