Journal of Aerospace Engineering

This paper proposes analytical solutions to optimal underactuated spacecraft formation reconfiguration in elliptic orbits, without either the radial or in-track thrust. For either underactuated case, the dynamical model of underactuated formation reconfiguration was developed, based on which the system controllability and reconfiguration feasibility then were analyzed. By using the indirect optimization method, a detailed optimization procedure was designed, and the optimal trajectory of formation reconfiguration was derived analytically for the underactuated cases. A fully actuated optimal reconfiguration scheme was introduced to make comparisons. Numerical simulations indicated that the proposed optimal underactuated reconfiguration schemes can manage formation reconfiguration with a control cost similar to that of the fully actuated scheme, even in the absence of radial or in-track thrust. Numerical comparisons with existing nonoptimal reconfiguration schemes further verified that the proposed optimal schemes can perform underactuated formation reconfiguration in an energy-optimal way.

Microturbojets are one of the main thrust sources in several high-performance unmanned aerial vehicles (UAVs). In many applications these vehicles operate in conditions that may demand performance at the limits of microturbojets’ capabilities. These conditions can eventually result in component degradation and engine malfunction. Safety and reliability demand to monitor and diagnose the health of the motor during the operation of the vehicle. One of the main microturbojet health indicators is the exhaust gas temperature (EGT). The scope of this article is to evaluate the estimation accuracy and computational cost of several EGT models through extensive experimental data. The evaluated models include classical, data-based, and novel approaches: an adiabatic nozzle representation, a nozzle model with a lineal correction, a nozzle model including heat transfer, a genetic programming model, a feed-forward neural network, a polynomic approximation and a multiphysics model. This evaluation provides information regarding the advantages and disadvantages of each model. The results show that the best-suited model depends mainly on the application and available identification data.

Because transmission tower-line systems are always exposed to the natural environment, such structures are vulnerable to various meteorological conditions, and the rupture of a transmission line is a particularly serious potential accident. Although many studies have been conducted on the dynamic responses of transmission towers subjected to cable rupture, few have considered the uncertainties that exist in the structures of transmission towers. To investigate the effects of the uncertainties in material properties and geometric parameters on the dynamic responses caused by cable rupture, a finite-element (FE) model is established in Abaqus; then deterministic, sensitivity, and probability analyses are conducted in succession. This study reveals that the yield strength and geometric size of diagonal members have significant effects on the responses of a transmission tower subjected to conductor rupture. In addition, based on the probability analysis, the results of the deterministic analysis are reliable, and structures under a conductor rupture load have a substantial probability of being partially damaged, which means that current design codes must be improved.

This experimental investigation focuses on the feasibility of attaching winglets to an indigenously developed fixed-wing mini unmanned aerial vehicle (UAV) to improve its aerodynamic efficiency. Winglets are well known for their application to reduce lift-induced drag and thereby saving fuel for manned aircraft. In this study, the effectiveness of winglets in the form of a simple end plate for a fixed-wing mini UAV, whose operating speed is low ($\mathrm{Re}<200\mathrm{k}$) is explored through wind tunnel tests and actual flight tests. To understand the flow field features, a flow diagnostics of wingtip flow with and without end plates was performed using a stereoscopic particle image velocimetry technique. Force measurements were also performed to quantify the improved aerodynamic efficiency of the mini UAV with the application of end plates. An approximately 10%–12% increase in the $L/D$ ratio is achieved by attaching the end plates to the wingtips of the fixed-wing mini UAV. An actual flight trial shows that flight endurance increased by 15% with the application of end plates compared to the baseline flight.

Mesh reflectors are widely employed for large space antennas due to their lightweight, compact, and easy package. Their cable length has to be carefully designed to guarantee the reflector surface shapes the desired paraboloid rigidly. In this paper, a robust optimal design is addressed for mesh reflectors, aiming at reducing the adverse impact on reflector surface accuracy of the inevitable inaccuracy in cable lengths during manufacturing and assembly. The objective of the robust design of mesh reflectors is to find the optimal cable length, so that mesh reflectors have the best nominal surface accuracy with as low as possible variations that result from uncertain cable length inaccuracies. Because the best surface accuracy is at a minimum and has a zero first-order gradient, a second-order variation model for the surface accuracy is employed. Numerical examples show the proposed method can achieve an effective, robust optimal design that is insensitive to the inaccuracy in cable lengths.

In this paper, the assessments of structural health monitoring (SHM) for metallic structures are presented. Tests were conducted on three specimens for fatigue crack testing and damage index measurements. In each specimen, a transducer array of six Stanford Multiactuator-Receiver Transduction (SMART) Layers, each of which contains a piezoelectric transducer, was mounted near the fatigue crack. The Lamb wave was driven by one SMART Layer and received by another. The transducer array generated nine forward and nine backward propagating paths. The damage index defined in the first arrival window (FAW) was obtained for each path. In this work, we propose an averaging process to obtain average damage index from the transducer array. The Lamb waves with various driving frequencies were tested to conduct the performance of the damage monitoring. The results show that the plot of the average damage index versus the actual crack length reveals a narrow band, indicating a small standard deviation of the measurement data. The data of numerous crack lengths and Lamb wave paths are processed statistically to determine the probability of detection (POD) of this damage detection method. It was found that the Lamb wave with the driving frequency of $f=450\mathrm{kHz}$ performed best in the crack monitoring. By using an threshold damage index ${\mathrm{DI}}_{\mathrm{th}}=0.01$, the detectable crack sizes $a_{50/50}$, $a_{90/50}$, and $a_{90/95}$ for the case of $f=450\mathrm{kHz}$ are 4.83, 5.79, and 5.92 mm, respectively. Based on the proposed approach, the relations between the damage index and actual crack length and the POD curves can be applicable to a real structure with the same geometry.

Shock-boundary layer interaction (SBLI) at hypersonic inlets can alter the flow pattern and impose adverse effects on engine operation if not controlled. A two-dimensional surface modification in the form of a sinusoidal wavy patch was introduced to a standard wedge-plate model in a hypersonic freestream of Mach 8.5 to test its influence on incident SBLI. Experimental and numerical comparison of flow visualization and wall pressure readings on the model with and without the wavy patch indicated a mitigating effect of the wavy patch on incident SBLI. The controlled SBLI induced significantly smaller flow separation compared with an uncontrolled case. Because of the minimally intrusive design of the wavy patch, the flow distortion/instability was notably less than that observed in the uncontrolled case.

In this paper, an optimization-based computational framework for the spatial tailoring of a metal-ceramic composite panel subjected to high-speed flow is discussed. The framework includes the modeling, evaluation, and optimization of the spatial material grading and thermostructural response of the metal-ceramic composites over a wide range of temperatures. The framework relies on micromechanics and a finite-element analysis (FEA) of representative volume elements (RVEs) to obtain the overall elastic, thermoelastic, and thermal properties of the graded microstructure as functions of temperature and spatial position. The effective thermostructural response of the airframe is analyzed using the FEA. The time-dependent thermal and structural loads are representative of a characteristic high-speed trajectory. Optimal multivariable material distribution is determined numerically using a constrained sequential quadratic programming (SQP) method of surrogate models to evaluate the response at multiple design locations efficiently. Three example cases are presented to showcase the developed framework. In all three example cases, optimal material variation and panel thickness are found such that they reduce the section mass when compared to a benchmark titanium (Ti-6Al-4V) structural skin and Acusill II thermal protection system (TPS) solution. Furthermore, these studies demonstrate that the use of metal-ceramic spatially tailored materials makes excellent material choices for operation in the high-speed environment.

The unbalance of the rotor system is the main factor causing the vibration of aeroengines. Research on unbalancing vibration coupling, vibration transmission, and vibration sensitivity of inner and outer dual rotors is the key link of the whole machine vibration and dynamic balance research. In this paper, the motion differential equation and dynamic model of the inner-outer dual-rotor system are established, and the unbalanced vibration of the dual-rotor system considering the coupling effect of the intermediate bearing is studied by combining theoretical analysis and simulation methods. The influence of unbalanced position, the magnitude and phase of unbalance, and the stiffness of the intermediate bearing on the vibration response of dual rotors are obtained. Aiming at the randomness of the unbalance vector distribution in the rotor system, the unbalance vector is extracted based on the Monte Carlo sampling principle. The multidisk and multiplane unbalanced vibration response law of the dual-rotor system is obtained, and the vibration transmission law and vibration sensitivity of the rotor under an unbalanced state caused by the coupling action of the inner-outer rotors are revealed. Finally, an experiment is carried out based on a self-designed test bed; the measured results are consistent with the analytical and simulation results.

Negative external pressure coefficients for design of components and cladding of steep-slope gable roofs (27° to 45° roof slope) on low-rise buildings subjected to wind loads were determined in this study based on data from wind tunnel tests of small-scale building models. The effect of exposure and building height were removed from the wind tunnel data, and the peak negative external pressure coefficients were determined using a Gumbel-fitting method. The spatial distribution of area-averaged peak negative external pressure coefficients was examined, and the results indicate that the effect of roof slope is not significant and that the largest magnitude peak negative external pressure coefficients do not always occur in the roof corner zone. Roof zones and equations for negative external pressure coefficients from current ASCE standard are generally in close agreement with the values based on wind tunnel test data, but negative external pressures on the roof edge normal to ridge and near ridge are underestimated. Modified roof zones and equations developed in this study are shown to improve the agreement with wind tunnel test data.

The global optimal solution for the underactuated attitude maneuver plays a significant role in the fields of spacecraft, robotics, and mechanics. This paper investigated the global optimal underactuated attitude maneuver by using angular velocity on a principal plane in the quaternion statement. The integral of angular velocity was considered as the performance criterion, and a correlation vector was introduced based on the coincidence of equations for the state and co-state. According to the Pontryagin minimum principle, it was concluded that the optimal angular velocity has the opposite direction as the correlation vector’s projection on the principal plane, thereby indicating that the optimal process is to roll the principal plane around a cone. The solution of the cone was obtained through two geometric constraints. One is that the angle between the correlation vector and the principal plane remains invariant; the other is that the trajectories of the correlation vector’s projection have the same length on the principal plane and the cone surface. The solution of the cone led to the analytical solution of the angular velocity and the control torque. For validation, the simulation results indicated that the optimal cost value obtained with the proposed cone-rolling solution, i.e., the integral of angular velocity, is lower than the suboptimal value obtained with the genetic algorithm. That is, the proposed cone-rolling principle–based global optimal analytical solution is reasonable and feasible.

Unmanned aerial vehicle (UAV) swarm technology can expand the working scope of tasks and improve the overall task efficiency. Traditional single leader-follower fusion algorithms for cooperative navigation cannot fully utilize collaborative navigation information, and low reliability and navigation precision in interference cases. Meanwhile, the full connected fusion algorithm for cooperative navigation shows a large relative computing and communication burden and inflexibility to overcome the faults. Therefore, this paper proposes a collaborative navigation algorithm for a UAV swarm based on a hierarchical structure. A model for intervehicle collaborative measurement of UAV swarm cooperative navigation, with the line-of-sight calculation uncertainty estimation, is established. The hierarchical collaborative navigation fusion algorithm that could be adaptive to asynchronous updating of members in the swarm is designed. A comparison of simulation results of cooperative navigation of the UAV swarm by the different cooperative fusion algorithms is provided. The results indicate that the proposed method can improve the positioning accuracy and robustness of the cooperative navigation of a UAV swarm.

Estimating the wing weights of personal air vehicles (PAVs) is limited by lack of comparable data, as there were no PAV data available to the public. In this study, the limits were confirmed by verifying estimation equations published in the literature. Research was then conducted to derive an equation to estimate PAV wing weight to overcome such limits. To address difficulties which arose during the data collection process, research was conducted on the derivation of a PAV wing-weight estimation equation that could be used in the initial design stage, based on single-engine turbo-propeller aircraft with specifications similar to those of PAVs. The estimation equation was derived using a regression analysis. Typically, data estimation models created with statistical methods frequently result in the overfitting phenomenon, in which the model cannot properly respond to actual data. To address this problem, the model creation and evaluation steps were performed using the K-fold cross-validation method, which was made into a program using Microsoft Excel version 2016 Visual Basics for Application (VBA). The final model was verified using actual data not used in the estimation model creation process. The variations in the final model were examined using a Monte-Carlo simulation. A final equation was derived that also considered the weight increase caused by the installation of a folding mechanism.

This work is focused on the development of a novel strategy to achieve dimensional stability for 55NiTi actuators that operate at a relatively higher temperature; i.e., with an austenite finish temperature, $A_f$, greater than 90°C. The key ingredient in this is to place the actuators in a state of significant deformations before the thermal cycling. Correspondingly, this will provide increased-stiffness regions purely due to kinematic/geometric nonlinearity effects. In turn, this effectively counteracts the tendency for cyclic evolutionary behavior inherent in the commercial NiTi material. To demonstrate the success of the new approach, modeling results are presented involving different actuators having various shapes, i.e., beams, disks, and rings, which are operating for many repeated thermal cycles under different bias load conditions, such as concentrated point force, ring line load, or distributed surface tractions.

Since damage identification results can be impressed by the effects due to changes in environmental and operational conditions, developing an effective monitoring system without any prior measured baseline data, while a structure is in its pristine condition, has gained much attraction recently. The instantaneous baseline damage identification method is one of the advanced techniques that works based on the concept of identicality of measured signals of similar paths. To hold this concept true, not only must the material properties, electromechanical characteristics, and the structure geometric features be identical, but also other features such as the sensor distance between equivalent paths and the geometrical parameters of the sensors must be the same. In this work, the influence of uncertainties in the length of sensing paths, which can be caused by sensor installation and tolerances in the dimensions of transducers, on the accuracy of instantaneous damage identification results is thoroughly investigated. In this paper, two damage index algorithms, i.e., correlation-based and wavelet-based algorithms, are employed, and the sensitivity of the methods to the mentioned uncertainties are numerically examined utilizing finite element (FE) simulation. The results are verified with the existing experimental data. Conclusively, the instantaneous wavelet-based method is not much sensitive to the transducers’ dislocation, and no special requirement is needed for their installation. However, the instantaneous damage identification results obtained using the correlation-based method are independent of the inequality in the dimensions of the transducers.

At present, the method of model testing is rarely used to study the low-frequency vibration problems of bridge structures, because it is difficult to keep the similarity between the bridge model and the prototype in model testing. Based on the similarity law of elastic force, a similarity model of a 32-m simply supported box girder bridge, a model bridge with a geometric similarity ratio of $10:1$, was designed and manufactured in this paper. The validity of the similarity model was verified by modal testing and numerical simulation. Then, through the hammer test of the similarity model, the vibration transmission characteristics of the model box girder between the panels and along the longitudinal direction of the bridge were studied. Also, the influence of the bridge support on the box girder vibration and the vibration reduction effect of the bridge support were analyzed. The results showed that when the top plate of the box girder is excited, the vibration attenuation from the top plate to the bottom plate is the fastest, followed by the top plate to the web, and from the top plate to the wing plate is the slowest. In the frequency range of less than 45 Hz, the vibration of the top plate attenuates slowly along the longitudinal direction of the bridge; in the frequency range of 45–200 Hz, the vibration of the top plate attenuates rapidly from the middle span to the 1/4 span section of the bridge and attenuates slowly from the 1/4 span to the support section of the bridge. The vibration reduction effect of the elastic support on the bridge pier was related to support stiffness and vibration frequency; the general rule was that the smaller the support stiffness, the better the vibration reduction effect. In addition, the vibration reduction effect varied greatly with different vibration frequencies.

Wind tunnel tests of an aeroelastic tower model at a length scale of $1:40$ were conducted to investigate the dynamic responses of an electricity transmission tower under synoptic and typhoon winds. The aeroelastic tower model was successively subjected to boundary layer and typhoon wind forcing in a single wind tunnel. The purpose of this study is to assess differences of the dynamic structural responses under two types of wind forcing and understand the underlying mechanism of transmission tower failures due to strong typhoons. The results indicated that the acceleration responses of the aeroelastic tower model were composed of resonant and background parts, while dominated by the resonant counterpart, and the dynamic responses of the transmission tower could be increased by up to 30% in the along-wind and crosswind directions under typhoon wind forcing. The wind load factors determined from the experimental results under typhoon winds were generally larger than those obtained from Chinese codes and standards. Suggestions on the wind-resistant design of an overhead transmission tower in typhoon-prone areas were proposed. The dynamic wind loads should be substituted by the most conservative values among different Chinese standards in estimating the equivalent static wind loadings of overhead towers under typhoon wind forcing.

Manufactured with a multilayer functional composite fabric envelope, lighter-than-air (LTA) airships offer a cost-effective approach for payload platforms. Considering the long-term service of LTA airships and their severe operating environments, the weathering degradation of the envelope materials is of extreme importance. However, few researchers have focused on the mechanical degradation of envelope materials from authentic LTA airships. In this study, URETEK3216LV, a typical weathered airship envelope, was sampled from a decommissioned authentic airship structure. A series of tests, including monouniaxial tensile tests, uniaxial cyclic tensile tests, and biaxial cyclic tensile tests, were performed to determine different specimen specifications. It was found that the strength reduction in warp reached more than 40%, and the breaking strain decreased. The elastic constants were calculated using the stress-strain curve fitting and the minimal residual strain method. According to the results, the degradation of the biaxial tensile elastic moduli was more severe than that of the uniaxial parameters, as the Poisson’s ratio remained almost unchanged. In future research, the results can be applied to the long-term analyses of airship structures, such as durable evaluation and deformation calculation.

Many transmission towers have collapsed during typhoon events, and the design wind loads in most current standards consider only the turbulence characteristics of monsoons. The gust response factor (GRF) is a parameter that is directly related to the wind field characteristics, and thus, it is necessary to address GRFs under typhoons to improve the calculation methods of design wind loads. First, the calculation methods of the GRF for transmission towers in various standards are introduced and compared. Then, two operational transmission towers are selected to carry out full-scale measurements, followed by detailed descriptions of a structural health monitoring (SHM) system. Finally, the GRFs are calculated based on on-site measurements during monsoon and three observed typhoon events. The measured results show that a higher turbulence intensity leads to a greater GRF. At low wind speeds, the larger the wind speed, the smaller the GRF; inversely, at high wind speeds, a larger wind speed leads to a greater GRF with a critical wind speed of approximately $9\mathrm{m}/\mathrm{s}$. Most of the measured GRFs are larger than the standard values, indicating that the current standards underestimate the GRFs of transmission towers. In typhoon-prone areas, the GRF of a transmission tower is recommended to be at least 3.0 to ensure structural safety.

An overhead transmission line system is a typical wind-sensitive structure with high flexibility, light weight, and low structural damping. Wind-induced dynamic reaction of the transmission line system is a determining factor in structural design of the supporting tower. In this study, we employ a closed-form solution and a series of wind tunnel tests to investigate three-dimensional dynamic reaction of transmission lines bundled with an insulator in three types, including I-type, V-type, and strain-type. The response comprises the background and resonant component. It is found that the background component constitutes a major part of the response, and the resonant component is closely related to the first symmetric out-of-plane mode. Furthermore, the closed-form solution is discussed and validated by the aeroelastic wind tunnel testing in the frequency domain. Based on the experimental data, this study provides a theoretical method for predicting wind-induced loads on transmission tower structures.

Structural damage diagnosis is still a challenging task because most current methods are either insensitive to local structural damage or sensitive to measurement noise. A statistical moment–based structural damage detection (SMBDD) algorithm has been proposed to locate and detect damages, revealing superiority in noise immunity. However, it requests that the number of measured responses should be no fewer than that of unknown structural parameters. In this paper, to reduce the number of measurements required in the SMBDD algorithm, an improved method for damage diagnosis is proposed based on the temporal moment of partially measured structural responses. Firstly, structural partial acceleration responses are measured and split into several time segments. Then, the temporal moment in each segment of the measured acceleration response time history is estimated. Finally, an objective error function is established by the temporal moments of measured accelerations and calculated accelerations, and structural stiffness can be identified by minimizing the objective error function. The proposed method is simple and feasible with a robust antinoise property and can identify structural damage when the number of measured responses is lower than that of the structural stiffness. Numerical simulations and an experimental study are conducted, respectively, to verify the feasibility and effectiveness of the proposed method.

Currently, the fluidic thrust vectoring technique is a promising method offering an alternative to the classical method of thrust deviation employing mechanical actuators with potential mass gain. In this article, theoretical and computational fluid dynamics investigations of counterflow fluidic thrust vectoring technique of a rectangular nozzle are carried through. A new engineering-type analytical approach based on mass and momentum conservation laws applied to specific control volumes is developed to predict the vectoring performance. Furthermore, the performance of the vectoring technique is computationally clarified for diverse nozzle pressure ratios (NPRs) and secondary pressure ratios (SPRs). Obtained conclusions indicate that the vectoring deflection angle diminishes with an increase in the NPR, whereas the thrust vectoring efficiency coefficient increases. The vectoring deflection angle and the thrust vectoring efficiency coefficient increase with a decrease in the SPR.

In this paper, a robust adaptive iterative learning control (ILC) scheme is developed for the high-precision attitude tracking control of spacecraft in the presence of parametric uncertainties and external disturbances. The proposed robust adaptive ILC law consists of three parts, i.e., the classic proportional-derivative (PD) feedback control term, the PD-type feedforward learning term, and the robust term. The adaptive updating laws are designed for the gain matrices of both the classic PD feedback control term and the PD-type feedforward learning term. The asymptotic stability of the whole closed-loop system is proved through the Lyapunov function–based convergence analysis. The proposed robust adaptive ILC scheme can not only compensate for the parametric uncertainties and repetitive disturbance, but also handle the nonrepetitive disturbance owing to the robust control concept. Moreover, the proposed robust adaptive ILC scheme can achieve the fast convergence speed benefiting from the adaptive technique. Numerical simulations illustrate the effectiveness and superiority of the proposed ILC scheme.

Several experimental databases of aeroelastic measurements performed on aircraft wing models are available for the validation of fluid–structure interaction (FSI) numerical methodologies. Most of these databases are used to model scaled systems focusing primarily on aerodynamic aspects, rather than on structural similitude with a full-scale model. To study flow regimes that replicate realistic operating conditions, wind tunnel test campaigns generate relatively high loads on models whose safe sizing forces the adoption of structural configurations that lose any similitude with typical wing box topologies. The aeroelastic measurements campaign conducted within the European Union “Radial basis functions at fluid Interface Boundaries to Envelope flow results for advanced Structural analysis” (RIBES) project was set up to shift attention to the structural similitude of aeroelastic mechanisms. The objective is to generate a database of loads, pressures, stresses, and deformations that is significant for a realistic aeronautical design problem. A wind tunnel model of a half wing that replicates a typical metallic wing box structure, instrumented with pressure taps and strain gauges, was designed and manufactured. This paper describes the experimental procedure and results by detailing the model design, its manufacture, and the measurements performed. All experimental data and numerical models are freely available online to the scientific community.

The procedures that couple finite-element method (FEM) solutions and fluid dynamic solvers to develop so-called high-fidelity fluid–structure interaction (FSI) numerical methods involve a series of awkward processes that affect both the robustness and accuracy of the tools. In particular, two aspects represent critical issues when coupling the two environments in two-way analysis procedures: the mapping of the computational fluid dynamics (CFD) solution, in the form of loads, to the structural model, and the adaptation of the CFD domain according to the shape deformation estimated by the FEM analysis. The enhancement of such coupling, and, more generally, the improvement of accuracy in numerical FSI procedures, was the objective of the European Union (EU)-funded radial basis functions at fluid interface boundaries to envelope flow results for advanced structural analysis (RIBES) research project. Specifically, the main tasks involved the development of a mapping procedure capable of nullifying the interpolation errors in the mapping process and the generation of an experimental database aimed at the validation of FSI methodologies while focusing on the structural modeling of realistic aeronautical topologies. The problem of the solver coupling was solved by approaching the CFD domain adaptation problem using a mesh morphing technique based on radial basis functions. The tool can smoothly propagate the deformation of wet surfaces by directly importing the vector displacements of the FEM mesh nodes in the native format of the structural solver. In addition to computational fluid dynamics–computational structural mechanics (CSM) direct coupling, a modal approach to model the FSI mechanism is proposed and was compared with the two-way procedure. This paper reports the validation of the two aeroelastic analysis methodologies performed within the RIBES project. The wind tunnel campaign investigated the structural aeroelastic response of realistic wing structures. The validation verified the tool’s capability to capture the stress state and the deformation of a typical wing box structure under aerodynamic loads.

This paper proposes a time-varying nonsingular terminal sliding mode control (TVNTSMC) law to control the attitude of rigid spacecraft. It provides an advantage for users to stipulate convergence time beforehand, and the proposed control algorithm will ensure global robustness to uncertainties as well as to external disturbances. A minimal (three-dimensional) modified Rodrigues parameter (MRP) explanation is used to represent the dynamics of a rigid satellite; then, the state-space representation of the dynamics is developed by transforming the dynamics into Lagrangian form. MRPs are used to design a new nonlinear sliding surface. The attitude control algorithm is expressed by a piecewise continuous function with time-varying properties. The Lyapunov theory is used to calculate the convergence and settling time to reach the equilibrium point. The time-varying function parameters are derived from convergence time prespecified by the user, which will ensure the system trajectories converge to the origin within the time specified. The global finite-time stability of the overall system is presented using the Lyapunov theorem in the presence of external disturbance. The simulation results are presented for different convergence times as input by the user to show the efficacy of the proposed controller.