Stable haptic rendering based on frequency domain observer and adaptive controller

Stability and transparency of the feedback force are essential to the haptic rendering system. By now, most of stability control schemes are working in the time domain. This paper introduces an updated stability control architecture based on stability estimation of the feedback force in frequency domain. The proposed stability control method comprises a frequency domain observer (FDO) and an adaptive coupling controller (ACC). This paper presents that the stability state of the haptic rendering force has an inherent relation with its frequency distribution. The proposed method uses such relation for stability estimation through FDO and regulates the feedback force via ACC to achieve stable interaction. Consequently, the necessary and sufficient stability condition of the adaptive controller is derived to justify that the proposed scheme can broaden the stability range of haptic system. Experimental results demonstrate that the proposed control methodology can render a stable haptic interaction when displaying high stiffness virtual model or variable stiffness virtual model.