Spiking-free HGO-based DSC for flexible joint manipulator

The tracking control problem for Flexible Joint Manipulator Control System(FJMCS)with unmeasurable states is addressed in this paper.Firstly,a High-Gain Observer(HGO)is constructed to estimate the unmeasurable states and the uncertainties.Then,a Dynamic Surface Control(DSC)scheme is developed by using the estimation of HGO.The newly proposed controller has two advantages over the existing methods:(A)a novel Spike Suppression Function(SSF)is developed to avoid the estimation spike problem in the existing HGO-based controllers.(B)Unlike the existing observer-based partial feedback control scheme that can only estimate the unmeasurable states,the proposed HGO can estimate both the unmeasurable states and uncertainties.The closed-loop system stability is proved by the Lyapunov theory.Simulation results demonstrate the effectiveness of the proposed controller.

A review on experimental techniques and their applications in the effects of mineral content on geomechanical properties of reservoir shale rock

Understanding the effects of mineral composition on geomechanical characteristics is critical in order to design and optimize the hydraulic fracturing necessary for shale gas reservoir production.Fundamental information is still missing in effects of mineral content and the experimental methodologies used.This paper provided an in-depth assessment of the various experimental methodologies and their applications in the relationship between the mineralogical and geomechanical features of the shale formation.The results revealed that more brittle minerals increase their strength,but chemical reaction that creats pores decrease their strength.High content of carbonate or quartz increases a rock's brittleness,while a high content of clay increases a rock's plasticity and decreases its brittleness.As phyllosilicate content increases,the uniaxial compressive strength decreases,and this could be because phyllosilicate minerals have a weakening effect on the mineral bond.Young's modulus often climb as clay minerals decline and as silica with carbonate concentration rises,however Poisson's ratio increases in relation to an increase in clay minerals,which also increases the ductility of the reservoir shale rock.However,compared to minerals and matrix,does not significantly impact the strength of shale rock.Besides,the benefits and drawbacks of using uniaxial and triaxial compression,ultrasonic testing,and nano-indentation techniques in unconventional reservoirs were described.The findings suggest that,because of the possibility for experimental testing repeatability for increased accuracy,ultrasonic testing is the most appropriate experimental approach in the scenes of assessing static and dynamic geomechanical properties of reservoir shale rock.We suggested that numerically-based simulation of experimental techniques used for shale geomechanical evaluations and numer-ical modeling of heterogeneous shale rock samples will be necessary in light of the limitations faced in the ap-plications of experimental techniques for shale geomechanical evaluation.