The backdrivable servovalve is a desirable component for force and interaction control of hydraulic actuation systems because it provides direct force generation mechanical impedance reduction by its own inherent backdrivability. However, high parametric uncertainty and friction effects inside the hydraulic actuation system significantly degrade its advantage. To solve this problem, this letter presents a disturbance-adaptive robust internal-loop compensator (DA-RIC) to generate ideal interactive control performance from the backdrivable-servovalve-based system. The proposed control combines a robust internal-loop compensator structure (RIC) with an explicit disturbance estimator designed for asymptotic disturbance tracking, such that the controlled system provide stable and ideal dynamic behavior for impedance control, while completely compensating the disturbance effects. With the aid of a backdrivable servovalve, we show that the proposed control structure can be implemented based on a simplified nominal model, and the controller enables implementation without accurate knowledge of the target system parameters and disturbances. The performance and properties of the proposed controller are verified by simulation and experiments.

Abstract
1. 서 론
2. 문제 정의
    2.1 역구동성 유압 구동 시스템
    2.2 Robust internal-loop compensator (RIC)의 특성 및 한계
3. Disturbance-adaptive RobustInternal-loop Compensator
    3.1 외란 추정기 설계
    3.2 성능 분석 및 물리적 해석
    3.3 역구동성 유압 시스템에의 적용
4. 시뮬레이션 및 실험
    4.1 시뮬레이션
    4.2 실험
5. 결 론
References

• 유선겸(Mechanical Engineering, POSTECH) | Sunkyum Yoo
• 정완균(Mechanical Engineering, POSTECH) | Wan Kyun Chung Corresponding author