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Variable Impedance Control for a Single Leg of a Quadruped Robot Based on Contact Force Estimation
Yanan Fan,Zhongcai Pei,Zhiyong Tang 제어·로봇·시스템학회 2024 International Journal of Control, Automation, and Vol.22 No.4
A quadruped robot interacts with the ground during the stance phase. This interaction will have a great impact on the feet, torso and joints of the robot, thus affecting the stability of its movement and reducing its adaptability in complex environments with features such as uneven terrain. The contact between each foot of the quadruped robot and the ground should not only control the movement trajectory of the leg but also control the force between the leg and the ground to comply with the environmental constraints. In general, the environment is constantly changing, whereas the traditional impedance control parameters are fixed and thus impose fixed-point constraints. To improve the compliance of the feet of a robot and achieve flexible interactions with the ground in various complex environments, such as pipelines, ruins and forests, variable impedance control is proposed. Based on variable inertia, damping and stiffness parameters, a new Lyapunov function is selected to analyse the stability of the closed-loop system. Furthermore, a force estimator is applied to estimate the contact forces, thereby reducing the burden of structural design and the cost of the robot. The effectiveness of the proposed variable impedance control scheme and contact force estimator is verified through numerical simulations in MATLAB.
Variable Impedance Control of Cable Actuated Continuum Manipulators
Guangping He,Yanan Fan,Tingting Su,Lei Zhao,Quanliang Zhao 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.7
Continuum manipulators are a class of special compliant robots that have important potential applications in the field of human-machine interactive operations, or work in cluttered and constrained environments. In these application scenarios, the most popular operation tasks are those with coupling force-position constraints. To simultaneously stabilize the desired operation force and the position of the manipulator, variable impedance control issues of the cable driven continuum manipulators are investigated in this paper. On the basis of constructing a novelLyapunov function, a variable impedance control law is presented and the stability of the closed-loop system has also been analyzed. Then the operation space variable impedance control for a single segment cable driven continuum manipulator is realized by the aid of a pseudo-rigid-body model. Some numerical simulations also demonstrate the stability of the variable impedance control system.
Prediction of Cellulose Crystallinity in Liquid Phase Using CBM-GFP Probe
Xiaoyu Guo,Fan Yang,Huixue Liu,Yingmin Hou,Yafang Wang,Jie Sun,Xiaoyi Chen,Yanan Liu,Xianzhen Li 한국고분자학회 2019 Macromolecular Research Vol.27 No.4
Carbohydrate-binding modules (CBMs) have been developed to investigate the presence of crystalline and amorphous regions of cellulose. However, systematic and quantitative assessment of cellulose crystallinity using such non-hydrolytic fusion proteins in liquid phase has not been reported. In this work, cellulose directed CBM probes containing a green fluorescent protein (GFP) were constructed and named CG17, CG28, and CG2a. The probe binding condition was determined as incubating 30 μg/mL probes in 10 mM phosphate buffer at 30oC for 60 min. Under the optimized condition, the linear correlations between CBM probe binding capability and X-ray diffraction (XRD) crystallinity were well established. Using linear regression equations, the crystallinity of several cellulosic materials was well calculated. Amorphous component and cellulosic surface area probably had a less effect on binding capability of CG2a than that of CG17 and CG28. Therefore, crystalline-region specific probe CG2a should be an efficient tool for interpreting the crystallinity of cellulosic materials.