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Incorporation of Ir cations into Co3O4 could cause a lattice expansion effect and thus promote both the hydrogen evolution reaction and the glycerol oxidation reaction.

In this article, an active disturbance rejection control (ADRC) scheme is proposed for the electromagnetic docking of spacecraft in the presence of time-varying delay, fault signals, external disturbances, and elliptical eccentricity. By introducing an auxiliary variable, an intermediate observer (IO) is presented to estimate the relative motion information and the total disturbance resulting from fault signals, unknown mass, external disturbances, and elliptical eccentricity. Then, an ADRC scheme is developed to guarantee that the relative position, relative velocity, and the estimation errors of relative motion information and the total disturbance can all converge into the neighborhood of the equilibrium. With the proposed control scheme, the time-delay factor is fully considered in the controller design to avoid adverse effect, and the uniform ultimate boundedness stability of the entire closed-loop system is analyzed with a rigorous theoretical proof. In comparison to conventional ADRC and other state-of-the-art schemes, the proposed ADRC scheme has several advantages, e.g., high accuracy, strong robustness, and requires no prior knowledge of the fault, time-varying delay and states information due to IO-based relative motion information and total disturbance estimations. Finally, numerical simulations are performed to show the effectiveness of the proposed control scheme.

The synergism of the hetero-phase Ni2P–Ni12P5 interface effect and Ru-doping induced strain effect in Ru–NixPy/N–C hybrid arrays enabled simultaneous H2 generation and formate electrosynthesis.

OsP/PHMCSs-600 exhibits excellent electrocatalytic activity and stability toward the hydrogen evolution reaction under alkaline and neutral conditions.

In this paper, the simplified electromagnetic force/torque model and coupled orbit-attitude dynamics modeling in spacecraft electromagnetic docking are investigated, and an improved sliding mode control scheme based on planned trajectory is proposed. In this scenario, the docking two spacecraft are equipped with four energized solenoids with iron cores fixed in the body frame, and small-angle hypothesis is used to derive the simplified electromagnetic force/torque model, based on which the coupled orbit-attitude dynamics equation is established. With trajectory planning of relative orbit and attitude, where the tracking process of coupled orbit-attitude is divided into three successive parts with predefined time using three characteristic time instants, a sliding mode control strategy is proposed to solve the tracking problem. Simulation results illustrate the simplification rationality of electromagnetic force/torque model, and the good tracking performance of coupled orbit-attitude tracking controller at predefined time.

CuO@MnO2 core–shell hierarchical nanoarrays with built-in electric field effects could trigger interfacial accumulation of nitrate ions and accelerate nitrate electroreduction kinetics.

Selective electrocatalytic nitrate-to-ammonia conversion holds significant potential in treatment of nitrate wastewater and simultaneously produces high-value-added ammonia. However, today's development of nitrate-to-ammonia technology remains hindered by the lack of electrocatalysts with high activity and selectivity. In this work, metal-organic framework-derived CuPd bimetallic nanoparticles/nitrogen-doped carbon (CuPd/CN) hybrid nanoarrays for efficient ammonia electrosynthesis from nitrate are designed and synthesized. Systematic characterization reveals that the electronic metal-support interaction between the CuPd nanoparticles and N-doped nanocarbon matrix could trigger interfacial charge polarization over the CuPd/CN composite and make Cu sites electron deficient, which is conducive to the adsorption of nitrate ions. Moreover, the Pd atom sites separate by Cu atoms and could catalyze the dissociation of H

In neuroscience, protein activity characterizes neuronal excitability in response to a diverse array of external stimuli and represents the cell state throughout the development of brain diseases. Importantly, it is necessary to characterize the proteins involved in disease progression, nuclear function determination, stimulation method effect, and other aspects. Therefore, the quantification of protein activity is indispensable in neuroscience. Currently, ImageJ software and manual counting are two of the most commonly used methods to quantify proteins. To improve the efficiency of quantitative protein statistics, the you-only-look-once-v5 (YOLOv5) model was proposed. In this study, c-Fos immunofluorescence images data set as an example to verify the efficacy of the system using protein quantitative statistics. The results indicate that YOLOv5 was less time-consuming or obtained higher accuracy than other methods (time: ImageJ software: 80.12 ± 1.67 s, manual counting: 3.41 ± 0.25 s, YOLOv5: 0.0251 ± 0.0003 s, p < 0.0001, n = 83; simple linear regression equation: ImageJ software: Y = 1.013 × X + 0.776, R2 = 0.837; manual counting: Y = 1.0*X + 0, R2 = 1; YOLOv5: Y = 0.9730*X + 0.3821, R2 = 0.933, n = 130). The findings suggest that the YOLOv5 algorithm provides feasible methods for quantitative statistical analysis of proteins and has good potential for application in detecting target proteins in neuroscience.

The purpose of this paper was to study the failure behavior of SUS304 stainless steel in view of cooling water leakage in actual service conditions. The temperature field and thermal stress distribution in the thickness direction of SUS304 stainless steel under actual service conditions were further analyzed by the finite element method. The results show that chromium-rich carbides are precipitated at the grain boundaries, which may cause intergranular corrosion. The morphology of the corrosion grooves is ditch structure, which has high intergranular corrosion susceptibility. The expansion direction of the cracks is from the contact surface of cooling water to the high-temperature contact surface. Fracture is characterized by a river pattern and rock candy pattern. Fracture morphology is characterized by brittle rupture. The Cl contained in the corrosion products comes from the circulating cooling water. XRD patterns show that the corrosion products are composed of CaCO3 (the high-temperature contact surface) and Fe3O4 (the contact surface of cooling water), respectively. EDS results of corrosion products are consistent with XRD results. The results of finite element simulation show that the temperature field along the thickness direction of SUS304 stainless steel plate is in the range of 436.6-450 °C. The peak of thermal stress is located in the middle of cross section. The cause of failure is acceleration of the initiation and extension of the cracks under the combined action of chloride ion stress corrosion, intergranular corrosion, and thermal stress. The form of crack fracture is mixture of transgranular and intergranular fracture, mainly transgranular fracture, which belongs to typical chloride ion stress corrosion.

This paper studies the problem of attitude stabilization for a rigid spacecraft subject to external disturbances, time-varying inertia uncertainties, and input magnitude and rate constraints (MRCs). By analyzing the influence of inertia uncertainties, the reconstruction of lumped disturbances is accomplished to facilitate the controller design. Then, a disturbance observer is designed, based on which, a simple state feedback control strategy including estimation of lumped disturbances is proposed. By choosing new state variables using attitude information and estimation errors, an augmented plant is constructed. Using standard Lyapunov stability analysis, which shows that all states are uniformly ultimately bounded, sufficient conditions for the existence of the disturbance observer and controller are given based on linear matrix inequalities (LMIs). It is worth pointing out that the observer and controller gains are obtained simultaneously. It is shown that the control scheme developed is not only robust against external disturbances and unknown time-varying inertia uncertainties, but also able to steer the attitude control performance and estimation errors of lumped disturbances. Numerical simulations are performed to demonstrate the effectiveness of the proposed control strategy.

Objectives: Brain arteriovenous malformation (AVM) is one of the most common causes of intracranial hemorrhage in young adults, and its expeditious diagnosis on digital subtraction angiography (DSA) is essential for clinical decision-making. This paper firstly proposed a deep learning network to extract vascular time-domain features from DSA videos. Then, the temporal features were combined with spatial radiomics features to build an AVM-assisted diagnosis model.Materials and method: Anteroposterior position (AP) DSA videos from 305 patients, 153 normal and 152 with AVM, were analyzed. A deep learning network based on Faster-RCNN was proposed to track important vascular features in DSA. Then the appearance order of important vascular structures was quantified as the temporal features. The structure distribution and morphological features of vessels were quantified as 1,750 radiomics features. Temporal features and radiomics features were fused in a classifier based on sparse representation and support vector machine. An AVM diagnosis and grading system that combined the temporal and spatial radiomics features of DSA was finally proposed. Accuracy (ACC), sensitivity (SENS), specificity (SPEC), and area under the receiver operating characteristic curve (AUC) were calculated to evaluate the performance of the radiomics model.Results: For cerebrovascular structure detection, the average precision (AP) was 0.922, 0.991, 0.769, 0.899, and 0.929 for internal carotid artery, Willis circle, vessels, large veins, and venous sinuses, respectively. The mean average precision (mAP) of five time phases was 0.902. For AVM diagnosis, the models based on temporal features, radiomics features, and combined features achieved AUC of 0.916, 0.918, and 0.942, respectively. In the AVM grading task, the proposed combined model also achieved AUC of 0.871 in the independent testing set.Conclusion: DSA videos provide rich temporal and spatial distribution characteristics of cerebral blood vessels. Clinicians often interpret these features based on subjective experience. This paper proposes a scheme based on deep learning and traditional machine learning, which effectively integrates the complex spatiotemporal features in DSA, and verifies the value of this scheme in the diagnosis of AVM.

This paper addresses the control problem of spacecraft electromagnetic docking in the presence of external disturbances, fault signals, elliptical eccentricity, and input magnitude and rate constraints (MRCs). More specifically, the dynamic model of translational motion in an elliptical orbit is derived first; by analyzing the influence of external disturbances, fault signals and elliptical eccentricity, a lumped disturbance is reconstructed to facilitate the controller design. Then, a state feedback control strategy based on disturbance observer, i.e. a disturbance observer-based controller (DOBC), is proposed, where the compensation of the lumped disturbance is considered. This controller thus has the nature of fault tolerance and robustness, and it requires no mass information on chaser or target spacecraft, no information on external disturbances, fault signals or even orbital elements except for semi-major axis. By choosing new state variables using the information on relative motion and estimation errors, an augmented plant is established. Using Lyapunov stability analysis, which shows that all states are uniformly ultimately bounded, sufficient conditions for the existence of the disturbance observer and controller subject to input MRCs are given based on linear matrix inequalities (LMIs). Numerical simulations are performed to demonstrate the validity and performance of the proposed strategy.

This paper addresses the attitude stabilization and vibration suppression problem for flexible spacecraft subject to model parameter uncertainty, controller perturbations, external disturbances and input constraints. The attitude model of flexible spacecraft is described and converted into a state space form in terms of passive and active vibration suppression schemes. A novel state feedback controller is proposed based on the exactly available expectation of a new variable, which is introduced to model a randomly occurring controller gain perturbation. Based on Lyapunov stability theory, sufficient conditions for the existence of the nonfragile H∞ controller considering input constraints are given based on linear matrix inequalities (LMIs) in terms of additive perturbation and multiplicative perturbation. Then, the developed controller subject to required constraints can be obtained, where the nonfragile property is fully considered to improve the tolerance to uncertainties in the controller. Numerical simulations are performed to demonstrate the effectiveness and superiority of the proposed control strategy in attitude stabilization and vibration suppression, where it should be noted that the passive vibration suppression scheme is superior for high natural frequencies while the active vibration suppression scheme is superior for low natural frequencies. Moreover, the low natural frequencies have more influence on the performance of attitude stabilization and vibration suppression.

The observer-based fault tolerant attitude control problem for spacecraft is addressed, wherein the constraints of H∞ performance, quadratic stability, model parameter uncertainty, measurement errors, external disturbances, controller perturbation, and actuator fault and saturation are considered simultaneously. A novel fault estimation approach is proposed, where a stochastically intermediate variable is introduced. Based on the exactly available expectation of such a variable, a new kind of intermediate observer is proposed to estimate the attitude information and fault signals simultaneously. Compared with the traditional fault estimation methods, the approach proposed in this paper is less conservative for it requires neither equation constraints nor observer matching condition and can tolerate stochastic failure. To achieve fault tolerant and nonfragile control performance, the estimation of fault signals and explicit controller perturbation are also exploited in the controller design. Based on Lyapunov stability theory, sufficient conditions for the existence of the observer-based fault tolerant nonfragile H∞ controller are given based on linear matrix inequalities (LMIs) in terms of additive perturbation and multiplicative perturbation. Numerical simulations are performed to demonstrate the effectiveness of the proposed method and also illustrate the advantage over the existing state feedback control method in terms of great reduction in energy consumption.

Long noncoding RNAs (lncRNAs) are crucial factors during plant development and environmental responses. High-throughput and accurate identification of lncRNAs is still lacking in plants. To build an accurate atlas of lncRNA in cotton, we combined Isoform-sequencing (Iso-seq), strand-specific RNA-seq (ssRNA-seq), cap analysis gene expression (CAGE-seq) with PolyA-seq and compiled a pipeline named plant full-length lncRNA (PULL) to integrate multi-omics data. A total of 9240 lncRNAs from 21 tissue samples of the diploid cotton Gossypium arboreum were identified. We revealed that alternative usage of transcription start site (TSS) and transcription end site (TES) of lncRNAs occurs pervasively during plant growth and responses to stress. We identified the lncRNAs which co-expressed or be linked to the protein coding genes (PCGs) or GWAS studied SNPs associated with ovule and fiber development. We also mapped the genome-wide binding sites of two lncRNAs with chromatin isolation by RNA purification sequencing (ChIRP-seq) and validated the trans transcriptional regulation of lnc-Ga13g0352 via virus induced gene suppression (VIGS) assay. These findings provide valuable research resources for plant community and broaden our understandings of biogenesis and regulation function of plant lncRNAs.One sentence summaryThe full-length annotation and transcriptional regulation of long noncoding RNAs in cotton.

Long noncoding RNAs (lncRNAs) are crucial factors during plant development and environmental responses. To build an accurate atlas of lncRNAs in the diploid cotton Gossypium arboreum, we combined Isoform-sequencing, strand-specific RNA-seq (ssRNA-seq), and cap analysis gene expression (CAGE-seq) with PolyA-seq and compiled a pipeline named plant full-length lncRNA to integrate multi-strategy RNA-seq data. In total, 9,240 lncRNAs from 21 tissue samples were identified. 4,405 and 4,805 lncRNA transcripts were supported by CAGE-seq and PolyA-seq, respectively, among which 6.7% and 7.2% had multiple transcription start sites (TSSs) and transcription termination sites (TTSs). We revealed that alternative usage of TSS and TTS of lncRNAs occurs pervasively during plant growth. Besides, we uncovered that many lncRNAs act in cis to regulate adjacent protein-coding genes (PCGs). It was especially interesting to observe 64 cases wherein the lncRNAs were involved in the TSS alternative usage of PCGs. We identified lncRNAs that are coexpressed with ovule- and fiber development–associated PCGs, or linked to GWAS single-nucleotide polymorphisms. We mapped the genome-wide binding sites of two lncRNAs with chromatin isolation by RNA purification sequencing. We also validated the transcriptional regulatory role of lnc-Ga13g0352 via virus-induced gene suppression assay, indicating that this lncRNA might act as a dual-functional regulator that either activates or inhibits the transcription of target genes.

Background Intracranial aneurysm is a common type of cerebrovascular disease with a risk of devastating subarachnoid hemorrhage if it is ruptured. Accurate computer-aided detection of aneurysms can help doctors improve the diagnostic accuracy, and it is very helpful in reducing the risk of subarachnoid hemorrhage. Aneurysms are detected in 2D or 3D images from different modalities. 3D images can provide more vascular information than 2D images, and it is more difficult to detect. The detection performance of 2D images is related to the angle of view; it may take several angles to determine the aneurysm. As the gold standard for the diagnosis of vascular diseases, the detection on digital subtraction angiography (DSA) has more clinical value than other modalities. In this study, we proposed an adaptive multiscale filter to detect intracranial aneurysms on 3D-DSA. Methods Adaptive aneurysm detection consists of three parts. The first part is a filter based on Hessian matrix eigenvalues, whose parameters are automatically obtained by Bayesian optimization. The second part is aneurysm extraction based on region growth and adaptive thresholding. The third part is the iterative detection strategy for multiple aneurysms. Results The proposed method was quantitatively evaluated on data sets of 145 patients. The results showed a detection precision of 94.6%, and a sensitivity of 96.4% with a false-positive rate of 6.2%. Among aneurysms smaller than 5 mm, 93.9% were found. Compared with aneurysm detection on 2D-DSA, automatic detection on 3D-DSA can effectively reduce the misdiagnosis rate and obtain more accurate detection results. Compared with other modalities detection, we also get similar or better detection performance. Conclusions The experimental results show that the proposed method is stable and reliable for aneurysm detection, which provides an option for doctors to accurately diagnose aneurysms.

Electromagnetic docking could enable autonomous spacecraft docking with no need for propellant consumption and without plume contamination. This paper addresses the robust electromagnetic docking problem for spacecraft in the presence of external disturbances, fault signals, unknown mass, elliptical eccentricity, measurement errors and input constraints. In this scenario, an intermediate observer is developed to estimate the relative motion information and the lumped disturbance resulting from these uncertainties. Based on this, an anti-disturbance controller is proposed, where the compensation of the lumped disturbance is considered. It is proved via Lyapunov analysis that the intermediate observer-based controller can achieve the objective of spacecraft electromagnetic docking with input constraints and in the presence of uncertainties. Finally, the observer-based controller is illustrated, in simulation, to demonstrate the effectiveness and improved performance compared with a disturbance observer-based controller.

This paper addresses the non-fragile control problem for a class of uncertain linear systems subject to model uncertainty, controller perturbations, fault signals and input constraints. The controller to be designed is supposed to have additive gain perturbations. A novel state feedback controller is proposed based on the exact available expectation of a Bernoulli random variable, which is introduced to model the feature of the controller gain perturbation that randomly occurs. By using Lyapunov stability theory, new sufficient conditions are derived to design non-fragile controller for a class of uncertain linear systems considering input constraints. Compared with the existing non-fragile state feedback controller methods, the non-fragile property is fully considered to improve the tolerance of uncertainties in the controller, where the conservativeness can be reduced via the Bernoulli random variable. The effectiveness of the proposed control strategy is illustrated by two numerical examples.

A continuous globally stable control algorithm is presented to track angular velocity for spacecraft chaotic attitude motion affected by external disturbances using adaptive variable structure controller. Affected by some external disturbances, the spacecraft attitude dynamics system can generate many types of chaotic motion. Once it is required that a spacecraft with chaotic attitude motion should track the other spacecraft chaotic attitude plant to achieve angular velocity synchronization, the design of a robust tracking controller becomes necessary. The controller design is based on adaptive control theory and variable structure control theory, and adopts integral sliding surface and a single vector adjusted dynamically. Numerical simulations are performed to demonstrate the effectiveness and feasibility of the proposed adaptive variable structure controller.

A novel improved mixed H2/H∞ control technique combined with poles assignment theory is presented to achieve attitude stabilization and vibration suppression simultaneously for flexible spacecraft in this paper. The flexible spacecraft dynamics system is described and transformed into corresponding state space form. Based on linear matrix inequalities (LMIs) scheme and poles assignment theory, the improved mixed H2/H∞ controller does not restrict the equivalence of the two Lyapunov variables involved in H2 and H∞ performance, which can reduce conservatives compared with traditional mixed H2/H∞ controller. Moreover, it can eliminate the coupling of Lyapunov matrix variables and system matrices by introducing slack variable that provides additional degree of freedom. Several simulations are performed to demonstrate the effectiveness and feasibility of the proposed method in this paper.

This paper investigates the robust dynamic output feedback non-fragile control (RDOFNFC) strategy for spacecraft attitude stabilization problem with nonlinear perturbations. The spacecraft attitude dynamics model takes the actuator saturation limits, external disturbances, controller perturbation and model parameter uncertainty into account. To make spacecraft attitude system satisfy H ∞ performance and quadratic stability, with respect to the additive perturbation in initial state and multiplicative perturbation in decay phase, the corresponding RDOFNFC is designed respectively. Based on Lyapunov theory, the controller design is transformed into a multi-objective convex optimization problem based on linear matrix inequalities (LMIs). Simulation results based on the on-orbit servicing spacecraft show good performance under external disturbances, model parameter uncertainty and controller perturbation, which validates the effectiveness and feasibility of the proposed control method.

This paper investigates the robust non-fragile state feedback attitude control problem for uncertain spacecraft, and the problem explored here is subject to H∞ performance constraint, quadratic sta...

Modified nanoscale zero-valent iron (nZVI) is a promising functional material for the remediation of combined pollutants involving polychlorinated biphenyls (PCBs) and heavy metals. However, the interaction between the two types of pollutants has not been systematically studied for this method of treatment. In this study, 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB153), Cu2+, and Ni2+ were selected as the target pollutants. To understand the interaction between pollutants, the efficiencies of nZVI, sulfidated nZVI (S-nZVI), and carboxymethylcellulose stabilized nZVI (CMC-nZVI) were investigated for removal of PCB153, Cu2+/Ni2+, and combined pollution system (PCBs-Cu2+/Ni2+). Results showed that the removal kinetics of the two types of pollutants by the three materials fitted a pseudo-first-order model well and that the reaction mechanisms were similar. Among the three materials, CMC-nZVI showed the highest reactivity to degrade PCB153 (pseudo-first-order kinetic constants (kobs) = 2.7 × 10−4 min−1) and remove Cu2+ (kobs = 2.890 min−1), while S-nZVI showed higher affinity for the removal of Ni2+ (kobs = 0.931 min−1). For the combined pollution system, PCB153 had little effect on the removal of heavy metals by the three materials, while the effect of heavy metals on PCB153 degradation was related to the types of heavy metals and the materials. Cu2+ had no significant effect on PCB153 degradation by the three materials, while the coexistence of Ni2+ promoted PCB153 degradation by nZVI and CMC-nZVI. XPS and electrochemical analysis showed that Cu0 and Ni0 were produced on the surface of the three materials. Ni is a more effective catalyst and promoted the electron transfer efficiency of the materials and had a positive impact on the dechlorination reaction.

Sulfide-modified nanoscale zerovalent iron (S-nZVI) has excellent reducing performance for heavy metals in water. The influence of environmental factors on the reactivity can be used to explore the practical feasibility of S-nZVI and analyze the reaction mechanism in depth. This study compared the removal effect and mechanism of Cu2+ and Ni2+ by nanoscale zerovalent iron (nZVI), S-nZVI, and carboxymethyl cellulose-modified nanoscale zerovalent iron (CMC-nZVI). The results show that the pseudo-first-order kinetic constant of Cu2+ removal by nZVI, S-nZVI, and CMC-nZVI was 1.384, 1.919, and 2.890 min-1, respectively, and the rate of Ni2+ removal was 0.304, 0.931, and 0.360 min-1, respectively. The removal mechanism of S-nZVI was similar to that of nZVI and CMC-nZVI. Specifically, Cu2+ was predominantly removed by reduction, while Ni2+ removal included adsorption and reduction. Environmental factors had a specific inhibitory effect on the removal of Cu2+ but had a negligible impact on Ni2+. The condition of low pH, the presence of Cl- and humic acid (HA) promoted the corrosion consumption of Fe0, in which H+ directly corroded Fe0 at low pH. At the same time, Cl- and HA inhibited the adsorption or binding of heavy metal ions on the particle surface, thereby reducing the electron transfer and utilization efficiency. The passivation of NO3- reduced the anaerobic corrosion of the material in water but suppressed the release of electrons, thereby reducing the reduction efficiency of the three types of materials. The anaerobic corrosion of S-nZVI was less affected by environmental factors, and it can still maintain more than 80% of the electronic utilization efficiency under different environmental factors, which illustrates that S-nZVI has broad prospects for practical applications in heavy metal polluted water.

Because the artificial bee colony(ABC) algorithm has problems of poor development ability, slow convergence rate and easy to fall into local optimum, an improved ABC algorithm is proposed. The algorithm combines the global optimal guidance strategy, we propose a new location update formula to improve the efficiency of the iterative optimization process, and introduce the mining coefficient in the formula to improve the accuracy of global optimization. In addition, the beta distribution is introduced during the scouting bee phase, which improves the disturbance ability of the algorithm and prevents it from falling into local extremum effectively. Finally, the simulation results of four benchmark functions of Sphere, Rastrigin, Rosenbrock and Griewank show that compared with the traditional algorithm and other improved artificial bee colony algorithm, the proposed algorithm has faster convergence speed and better optimization ability.

The control problem of underactuated spacecraft chaotic attitude motion is investigated based on exponential reaching law in this paper. First, the underactuated spacecraft chaotic attitude system is written in nonlinear equation form with two controls. Once the trajectory planning of angular acceleration is preset, the dynamics equation of angular velocity error can be obtained. Then, the sliding mode controller based on exponential reaching law and linear matrix inequality is designed, which consists of equivalent control term and switching control term. Finally, simulations are performed to test the performance of the proposed controller.

A novel model of space electromagnetic docking is established to solve the problem of traditional plume contamination and short service life in this paper. A new modelling technique regarding space electromagnetic docking for CubeSat is proposed. The mathematical model with four core-containing energized solenoids is derived and simplified to the magnetic dipole far-field model of single-turn coil. Simplifying the magnetic dipole far-field model will yield the model of space electromagnetic docking, and the numerical simulation results also verify the reliability and feasibility of simplification process.

This paper investigates the design method of full order state observer for satellite attitude control system using mixed H 2 /H ∞ optimal approach. A linear system described by state space form is introduced first to state the problem of full order state observer design. The designed observer should meet the requirement of H 2 performance and H ∞ performance so that the disturbance would influence the observer as little as possible. Thus, we convert the satellite attitude control system to the same state space form, and deduce the mixed H 2 /H ∞ approach based on linear matrix inequalities (LMIs). By solving LMIs, we can obtain the solution of corresponding convex optimization problem. Then, the observer gain can be decided. The simulation results based on satellite attitude control system show that the magnitude of observer error is 10−6 rad/s within 10000s. We can conclude that the mixed H 2 /H ∞ approach of full order state observer design is effective and the external disturbance has little influence on the observation error.

Due to the space missions' limited budget, microsatellite would be an economical choice, so there has been a great decrease in size and weight. Micro satellite is vulnerable to space environmental disturbances and perturbation of controller. As to the multiplicative perturbation in attitude controller, this paper investigates a robust H ∞ controller design with model uncertainties and subject to external disturbances and controller's multiplicative perturbations. By using linear matrix inequality (LMI) method, the numerical solution of state feedback controller in terms of multiplicative perturbation can be efficiently solved. The performance differences between the non-fragile control and the mixed H 2 /H ∞ control without considering controller's multiplicative perturbation are discussed in detail. The attitude control design taking controller perturbation into account shows excellent effectiveness with respect to simulation results.