Modellering og styring af elektro-hydraulisk system med fire frihedsgrader
Authors
Vad, Claus ; Jensen, Niels Haldrup
Term
4. term
Education
Publication year
2013
Submitted on
2013-06-10
Pages
108
Abstract
This thesis examines whether advanced nonlinear control methods can match or surpass conventional linear controllers in a complex four-degree-of-freedom electro-hydraulic system. A detailed physics-based model of a Case III 580 “Super King” backhoe arm is developed, capturing asymmetric valves with and without overlap, fluid compressibility, asymmetric cylinders, friction, and a load model formulated via the Euler–Lagrange approach. The kinematic representation follows the Denavit–Hartenberg convention and enables inverse kinematics for trajectory control. On top of this model, both a linear reference controller (PI with feed-forward and a pressure-feedback variant) and second-order sliding-mode algorithms (Super Twisting and Twisting) are designed, with proposed modifications aimed at reducing control signal activity near actuator constraints without sacrificing position tracking. The methods are evaluated on two predefined trajectories—one with high accelerations and one involving lifting a heavy chain to induce large load variations—in simulation and experiment. Results indicate that the sliding-mode controllers achieve tracking accuracy comparable to, and in some cases better than, the linear reference while the proposed modifications effectively attenuate control signal activity near constraints. Overall, the work highlights the potential of modified second-order sliding-mode control to improve performance in industrial electro-hydraulic applications.
Specialet undersøger, om avancerede ikke-lineære styringsmetoder kan matche eller overgå traditionelle lineære controllere i et komplekst elektrohydraulisk system med fire frihedsgrader. Der udvikles en detaljeret fysisk model af en Case III 580 “Super King” rendegraverarm, der inkluderer asymmetriske ventiler med og uden overlap, oliestivhed, asymmetriske cylindre, friktion samt en lastmodel formuleret med Euler–Lagrange-metoden. Den kinematiske repræsentation følger Denavit–Hartenberg-konventionen og muliggør beregning af invers kinematik til banestyring. På basis af denne model designeres både en lineær referencestyring (PI med feed-forward og trykfeedback-variation) og andenordens sliding-mode-algoritmer (Super Twisting og Twisting), for hvilke der foreslås modifikationer med henblik på at reducere kontrolsignalaktivitet nær styrebegrænsninger uden at kompromittere positionssporing. Metoderne evalueres via to foruddefinerede baner—en med høje accelerationer og en med løft af en tung kæde, der giver stærkt varierende belastning—i både simulering og eksperiment. Resultaterne viser, at sliding-mode-controllere opnår positionsnøjagtighed på niveau med, og til tider bedre end, den lineære reference, og at de foreslåede modifikationer effektivt reducerer kontrolsignalaktiviteten omkring begrænsninger. Samlet peger arbejdet på et potentiale for forbedret ydeevne i industrielle elektrohydrauliske applikationer gennem modificerede andenordens sliding-mode-styringer.
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