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In this paper, the non-fragile joint state and fault estimation problem is investigated for a class of nonlinear time-varying complex networks (NTVCNs) with uncertain inner coupling and mixed time-delays. Compared with the constant inner coupling strength in the existing literature, the inner coupling strength is permitted to vary within certain intervals. A new non-fragile model is adopted to describe the parameter perturbations of the estimator gain matrix which is described by zero-mean multiplicative noises. The attention of this paper is focussed on the design of a locally optimal estimation method, which can estimate both the state and the fault at the same time. Then, by reasonably designing the estimator gain matrix, the minimized upper bound of the state estimation error covariance matrix (SEECM) can be obtained. In addition, the boundedness analysis is taken into account, and a sufficient condition is provided to ensure the boundedness of the upper bound of the SEECM by using the mathematical induction. Lastly, a simulation example is provided to testify the feasibility of the joint state and fault estimation scheme.

A cable-driven redundant manipulator (CDRM) characterized by redundant degrees of freedom and a lightweight, slender design can perform tasks in confined and restricted spaces efficiently. However, the complex multistage coupling between drive cables and passive joints in CDRM leads to a challenging dynamic model with difficult parameter identification, complicating the efforts to achieve accurate modeling and control. To address these challenges, this paper proposes a dynamic modeling and adaptive control approach tailored for CDRM systems. A multilevel kinematic model of the cable-driven redundant manipulator is presented, and a screw theory is employed to represent the cable tension and cable contact forces as spatial wrenches, which are equivalently mapped to joint torque using the principle of virtual work. This approach simplifies the mapping process while maintaining the integrity of the dynamic model. A recursive method is used to compute cable tension section-by-section for enhancing the efficiency of inverse dynamics calculations and meeting the high-frequency demands of the controller, thereby avoiding large matrix operations. An adaptive control method is proposed building on this foundation, which involves the design of a dynamic parameter adaptive controller in the joint space to simplify the linearization process of the dynamic equations along with a closed-loop controller that incorporates motor parameters in the driving space. This approach improves the control accuracy and dynamic performance of the CDRM under dynamic uncertainties. The accuracy and computational efficiency of the dynamic model are validated through simulations, and the effectiveness of the proposed control method is demonstrated through control tests. This paper presents a dynamic modeling and adaptive control approach for CDRM to enhance accuracy and performance under dynamic uncertainties.

In this paper, we developed a new algorithm to find the set of a non-dominated points for a multi-objective integer programming problem. The algorithm is an enhancement on the improved recursive method where the authors have used a lexicographic method for analysis. In this approach a sum of two objectives is considered as one weighted sum objective for each iteration. Computational results show that the proposed approach outperforms the currently available results obtained by the improved recursive method with respect to CPU time and the number of integer problems solved to identify all non-dominated points. Many problems such as assignment, knapsack and travelling salesman have been investigated on different sized problems. The benefit of this approach becomes more visible with the increase in the number of objective functions.

Purpose The typical approach of modeling the aerodynamics of an aircraft is to develop a complete database through testing or computational fluid dynamics (CFD). The database will be huge if it has a reasonable resolution and requires an unacceptable CFD effort during the conceptional design. Therefore, this paper aims to reduce the computing effort required via establishing a general aerodynamic model that needs minor parameters. Design/methodology/approach The model structure was a preconfigured polynomial model, and the parameters were estimated with a recursive method to further reduce the calculation effort. To uniformly disperse the sample points through each step, a unique recursive sampling method based on a Voronoi diagram was presented. In addition, a multivariate orthogonal function approach was used. Findings A case study of a flying wing aircraft demonstrated that generating a model with acceptable precision (0.01 absolute error or 5% relative error) costs only 1/54 of the cost of creating a database. A series of six degrees of freedom flight simulations shows that the model’s prediction was accurate. Originality/value This method proposed a new way to simplify the model and recursive sampling. It is a low-cost way of obtaining high-fidelity models during primary design, allowing for more precise flight dynamics analysis.

En los sistemas hidráulicos de redes de tuberías, uno de los parámetros fundamentales es el factor de fricción A. El factor de fricción se determina con la ecuación implícita de Colebrook-White por medios iterativos, lo cual dificulta su aplicación. En el presente trabajo se construye una correlación basada en el método recursivo para el cálculo del factor de fricción, para lo cual se empleó la ecuación de Colebrook-White. Para el cierre de la correlación se proponen dos relaciones empíricas, donde sus coeficientes y exponentes fueron calibrados en Excel 2019. Se compararon los resultados de las dos relaciones que se proponen con las relaciones de Swamee-Jain y Haaland, para incrementos recursivos, donde para la correlación Ag se obtuvo el error porcentual máximo del factor de fricción de 0,0000017 %, para la rugosidad relativa de 0,00001 y número de Reynolds 4000; así como, los decimales arrojaron siete dígitos decimales exactos para el factor de fricción. Para Reynolds mayores de 4000, el error porcentual disminuye. Se concluye que la correlación en función de las relaciones explícitas que se proponen satisface a la solución de la ecuación implícita de Colebrook-White.

The dynamic behavior of filled joints is mostly controlled by the filled medium. In addition to nonlinear elastic behavior, viscoelastic behavior of filled joints is also of great significance. Here, a theoretical study of stress wave propagation through a filled rock joint with linear viscoelastic deformation behavior has been carried out using a modified time-domain recursive method (TDRM). A displacement discontinuity model was extended to form a displacement and stress discontinuity model, and the differential constitutive relationship of viscoelastic model was adopted to introduce the mass and viscoelastic behavior of filled medium. A standard linear solid model, which can be degenerated into the Kelvin and Maxwell models, was adopted in deriving this method. Transmission and reflection coefficients were adopted to verify this method. Besides, the effects of some parameters on wave propagation across a filled rock joint with linear viscoelastic deformation behavior were discussed. Then, a comparison of the time-history curves calculated by the present method with those by frequency-domain method (FDM) was performed. The results indicated that change tendencies of the transmission and reflection coefficients for these viscoelastic models versus incident angle were the same as each other but not frequency. The mass and viscosity coupling of filled medium did not fundamentally change wave propagation. The modified TDRM was found to be more efficient than the FDM.

Investor interest in single-trigger catastrophe bonds (STCB) has the potential to decline in the future. It is triggered by the increasing trend of global catastrophe loss and intensity every year, which increases the probability that a claim of STCB will occur. To increase investor interest again, the issuance of multiple-trigger catastrophe bonds (MTCB) can be one solution. However, to issue MTCB, its pricing is more complex because it involves more factors than STCB. Therefore, this study aims to design a simple MTCB pricing model. The claim trigger indices used are actual loss and fatality. Then, a nonhomogeneous compound Poisson process is used to model actual losses and fatalities aggregate to consider catastrophe intensity. In addition, this study proposes numerical methods, namely the continuous distribution approximation method and the Nuel recursive method, to facilitate the application of the model. Finally, an analysis of the effect of catastrophe intensity and other factors on MTCB prices is also presented. This study is expected to help special-purpose vehicles as MTCB issuers in MTCB pricing.

Nested, or cascade speed and torque control has been widely used for DC motors over recent decades. Simultaneously, fractional-order control schemes have emerged, offering additional degrees of control. However, adopting fractional-order controllers, particularly in cascade schemes, does not inherently guarantee better performance. Poorly paired fractional exponents for inner and outer PI controllers can worsen the DC motor’s behavior and controllability. Finding appropriate combinations of fractional exponents is therefore crucial to minimize experimental costs and achieve better dynamic response compared to integer-order cascade control. Additionally, mitigating adverse couplings between speed and current loops remains an underexplored area in fractional-order control design. This paper develops a computational model for fractional-order cascade control of DC motor speed (external) and current (internal) loops to derive appropriate combinations of internal and external fractional orders. Key metrics such as overshoot, rise time, and peak current values during speed and torque changes are analyzed, along with coupled variables like speed drop during torque steps and peak torque during speed steps. The proposed maps guide the selection of effective combinations, enabling readers to deduce robust or adaptive designs depending on specific performance needs. The methodology employs Oustaloup’s recursive approximation to model fractional-order elements, with MATLAB–SIMULINK simulations validating the proposed criteria.

Applying a semi-recursive multibody approach enables the solution of the equations of motion of a complex system in real time. This makes it possible to conduct human-in-loop simulations and analyse the user experience. The idea of recognizing the user experience to produce more efficient, competitive, and user-friendly products has been limited thus far to the field of information technology and the development of light physical products. This study introduces a simulation modelling procedure for a complex forklift mast system that can be used to help analyse the user experience. A multibody forklift model is introduced that includes the electric motors, a pump, a freelift, a mainlift and tilt cylinders, actuators, pulley and chain mechanisms, contacts, and tyres. The viscoelastic behaviour of the chain during longitudinal and transverse movement is simulated using a discrete model approach. Triplex mast speeds and hydraulic system efficiencies across working cycles are used to verify the performance of the introduced real-time simulation model against measurements taken from an equivalent reference forklift. To better evaluate the developed model, experienced and inexperienced forklift drivers were asked to drive an updated simulator and provide feedback. User experience inputs that can be made available early on in development using this new modelling approach will permit experts to evaluate and design more efficient complex mechanical systems.

Purpose In this paper, the formulation and analytic solutions for fractional continuously variable order dynamic models, namely, fractional continuously mass-spring damper (continuously variable fractional order) systems, have been presented. The authors will demonstrate via two cases where the frictional damping given by fractional derivative, the order of which varies continuously – while the mass moves in a guide. Here, the continuously changing nature of the fractional-order derivative for dynamic systems has been studied for the first time. The solutions of the fractional continuously variable order mass-spring damper systems have been presented here by using a successive recursive method, and the closed form of the solutions has been obtained. By using graphical plots, the nature of the solutions has been discussed for the different cases of continuously variable fractional order of damping force for oscillator. The purpose of the paper is to formulate the continuously variable order mass-spring damper systems and find their analytical solutions by successive recursion method. Design/methodology/approach The authors have used the viscoelastic and viscous – viscoelastic dampers for describing the damping nature of the oscillating systems, where the order of the fractional derivative varies continuously. Findings By using the successive recursive method, here, the authors find the solution of the fractional continuously variable order mass-spring damper systems, and then obtain close-form solutions. The authors then present and discuss the solutions obtained in the cases with the continuously variable order of damping for an oscillator through graphical plots. Originality/value Formulation of fractional continuously variable order dynamic models has been described. Fractional continuous variable order mass-spring damper systems have been analysed. A new approach to find solutions of the aforementioned dynamic models has been established. Viscoelastic and viscous – viscoelastic dampers are described. The discussed damping nature of the oscillating systems has not been studied yet.