Vibration Suppression of Robot Arm by Feedforward Control with Auto-Measurement of System Parameter

In many industrial application fields, servo drive systems have widely applied to various load systems with complicated mechanisms such as low stiff structures and gears with backlash. Since such systems form multimass resonant systems and cause mechanical vibration, suppression of the vibration is required to achieve the high performance motion control. To overcome this problem, the modern control theory-based various techniques are suggested by using simple feedforward control or feedback control.The paper presents the vibration suppression control of a robot arm with a flexible joint by feedforward control based on a transfer function of the robot arm. The proposed controller can be simply realized using a conventional position controller and it generates a position command which does not cause the resonant vibration. The algorithm is quite practical, however, it is sensitive to mechanical parameters because the feedforward controller is designed by mechanical system parameters. Therefore, an auto-measurement of mechanical parameters using a Fast Fourier Transform (FFT) is also proposed to achieve the necessary control accuracy for practical usage. Experiments with the prototype show an effectiveness of the proposed control.