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A servo drive system with a permanent magnet synchronous motor (PMSM), ball-screw, gear and timing-belt is widely used in industrial applications such as numerical control (NC) machine, machine tool, robot and factory automation. These systems have torsional vibration in the torque transmission from the motor to the mechanical load owing to the mechanical couplings. This vibration reduces the dynamics of the speed responses and may result in damage to the mechanical plant. This study presents an adaptive notch filter with automatic searching of the resonant frequency and bandwidth from the speed error without any mechanical signal feedback to reject the mechanical vibration of the linear feeder system. The proposed control scheme can suppress the torque command signal of a PMSM in the resonant frequency area to reject the mechanical torsional vibration. Since the resonant frequency can be varied by the mechanical configurations and load conditions, the adaptive notch filter is designed to search the vibration frequency automatically and consequently suppress the mechanical resonant vibration. Experimental results show the verification of the proposed adaptive notch filter in a linear feeder system.