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Prescribed performance model-free hybrid force/position control for 3-DOF SEA-based manipulator under partial state constraints

Abstract

In this paper, for 3-DOF series elastic actuator (SEA) -based manipulators under partial state constraints, a prescribed performance model -free hybrid force/position controller (PPMHC) is designed. The PPMHC contains an outer force and an inner position control loop. The outer force control loop is designed by impedance control. Then, the inner position control loop is proposed according to the idea of model -free control. The inner position control loop consists of the prescribed performance control, integral -barrier Lyapunov function (IBLF), time -delay estimator, and neural approximation algorithm. It can be proven that the designed PPMHC can achieve stability of the closed -loop system under the partial state constraints by the Lyapunov function. Finally, the effectiveness of PPMHC is illustrated by the simulation results.

article Article

date_range 2024

language English

link Link of the paper

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Wei Yangchun

Wang Haoping

Tian Yang

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Featured Keywords

Model-free control

Prescribed performance control

Partial state constraints

Integral barrier Lyapunov function

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Effect of corrosion on flexural strength of reinforced concrete beams with polypropylene fibers

Abstract

An experimental study was performed to investigate the effects of polypropylene fibers on uncorroded and corroded reinforced concrete beams. Three different volume fractions of polypropylene fibers having 0, 0.5, and 1.5%, were tested at four corrosion levels of 0% and approximately 5, 7, and 9%. A full scale of an accelerated corrosion pool was used for the accelerated corrosion process. Reinforced concrete beams were used for an under monotonic bending test. The contribution of the actual corrosion levels of transverse and longitudinal reinforcement bars to the total corrosion levels were obtained from reinforcement bars fully extracted from concrete. Flexural strength, bond-slip, and moment-curvature relationships were examined for uncorroded and corroded reinforced concrete beams. A new model was developed to predict the flexural strength of corroded reinforced concrete beams. The proposed model for predicting the residual flexural strength of corroded beams was compared with test data published in previous studies. Furthermore, a novel model is presented for improved predictions between the actual and theoretically estimated corrosion mass losses, based on Faraday’s law, with the aid of fully extracted reinforcement bars. The model used to predict the flexural strength of corroded reinforced concrete beams with large sizes demonstrated good agreement with current and previously published literature data. In the case of corroded beams comprising differing amounts of polypropylene fibers, the performance of the corroded beams was limited by a fiber volume fraction of 1.5% at low corrosion levels.

article Article

date_range 2018

language English

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