For a Fast-Steering Mirror (FSM) driven by Voice Coil Motors (VCMs), the coil of the VCM touches the stator as the FSM achieves a broad range of motion. A novel FSM was developed to prevent the occurrence of undesired contact between the coil and stator. A compliant decoupling mechanism was designed to minimize the transverse displacement of the coil of the VCM. Moreover, for the FSM with a broad range of motion, the force-displacement relationship was nonlinear, which resulted in variable resonant frequencies at different motion positions. We developed a variable notch filter to eliminate the variable resonant modes, and a Proportional-Integral(PI) controller was designed to achieve closed-loop control. Compared to the fixed notch filter, the resonant frequencies of the variable notch filter were a function of the motion positions of the FSM. The bandwidth of the FSM was studied by finite-element analysis and experiments using fixed and variable notch filters. According to the experimental results, as a fixed notch filter was applied, the bandwidth of the FSM varied in different motion positions. When the motion position is less than 15.2 mrad, the bandwidths of the FSM along the θx and θy axes are approximately 95 Hz and 110 Hz, respectively; when the motion position is 18.2 mrad, the bandwidths of the θx and θy axes drop to 4792 Hz and 571 Hz, respectively. As a variable notch filter is applied, the bandwidths of the FSM along the θx and θy axes are stable at 95 Hz and 110 Hz, respectively; this result illustrates the need and effectiveness of applying a variable notch filter in an FSM system with a broad range of motion.