ModelingandProportionalIntegralSlidingModeControlofHydraulicManipulators;AnalysisanddesignofintegralslidingmodecontrolbasedonLyapunov'sdirectmethod;Commentson“Aclassofproportional-integralslidingmodecontrolwithapplicationtoactivesuspensionsystem;Aclassofproportional-integralslidingmode