Control Issues Research Articles

ANALYSIS OF THE CAUSES OF DEFECTS IN THE PRODUCTION PROCESS OF PILLOWCASES AND BOLSTERS USING THE FMEA METHOD APPROACH AT UD ARJUNO

In the world of manufacturing industry, it is not far from the name of maintaining and improving the quality of its products because it is the most important part of the production process. Quality is defined as a general characteristic of a product or service that affects its ability to meet needs. UD Arjuno is classified as an SME engaged in the manufacture of pillowcase and bolster products. In this business, the quality control carried out is still not optimal, this is indicated by the presence of a number of defective products found in each production. The purpose of this study is to identify the causes of disability that occur with the largest percentage and causative factors and provide suggestions for improvement. In quality control issues, UD Arjuno needs to use the FMEA analysis method to identify the impact of system or process failures, and reduce or eliminate the chances of failure. The results showed that of the 17 potential failure modes that cause defects in pillowcase products, there are 4 failure modes which are the highest RPN values or tercuritis failures that often occur, namely tilted malls, workers lack control of machines, materials easily eaten by rats and operators are less careful.

Asynchronous event-triggered [formula omitted][formula omitted] control for 2D Markov jump systems subject to networked random packet losses

This paper investigates the issue of asynchronous event-triggered control for two-dimensional Markov jump systems subject to networked random packet losses. The asynchronous behavior between the plant and controller is characterized by a hidden Markov model, and the packet loss behavior is described by a Bernoulli stochastic process. To relieve the communication pressure, an event-triggered strategy with independent triggering behavior in the horizontal and vertical directions is given. A sufficient condition is established to ensure stochastic stability and H∞ performance for the closed-loop system. Then, a method for designing an asynchronous event-triggered controller is developed through eliminating nonlinearities formed by the inverse of Lyapunov matrices. Moreover, based on convex optimization of the H∞ performance, an algorithm is proposed to find the maximum feasible domain of the event-triggered thresholds. Finally, a Darboux equation with Markov jump properties is applied to verify the effectiveness of the presented design method.

Asynchronous robust fuzzy event-triggered control of nonlinear systems

This paper deals with the problem of event-triggered integral sliding mode control (ISMC) for the perturbed nonlinear based-Takagi-Sugeno (TS) fuzzy systems. To reduce the chattering introduced by the unmatched disturbances, a disturbance observer is designed to get the estimated unmatched disturbances. To further reduce the computational burden and communication resources, compared with previous studies, two types of sliding surfaces are established. The time-triggered-based sliding surface which is used to ensure the reachability of the system states and the event-triggered-based sliding surface that is presented to calculate the control law, directly which benefits from less updates and consequently, less chattering that enhance the system performance. Moreover, the suggested control scheme is proposed based on asynchronous trait, i.e., the premise variables of the controller are in different time scale with the fuzzy systems which also leads to communication resource reduction. As a key issue in event-triggered control, it is ensured that the proposed controlled system is Zeno-free along the implementation. By the Lyapunov theory, the appropriate conditions for the ultimate boundedness stability (UBS) of the closed-loop system with a prescribed H∞ performance are derived in new offline LMIs. In order to illustrate the effectiveness of the suggested event-triggered integral sliding mode control, the Rossler system and track-trailer system are simulated and the obtained results are evaluated with the existing methods.

Robust trajectory tracking control scheme using transformed velocities for asymmetric underactuated marine vehicles

The paper addresses the issue of trajectory tracking control for underactuated underwater vehicles whose model is described by quasi-velocities resulting from the decomposition of the inertia matrix. The control algorithm takes into account unmodeled dynamics and external disturbances. It is shown that such mathematical models can be diagonalized and described by inertial quasi-velocities (IQV). The control scheme consists of a kinematic velocity controller and a dynamic adaptive integral sliding mode control algorithm. The paper extends the concept based on velocity transformation and backstepping methods to systems with a symmetric inertia matrix. A proof of the stability of a closed system in IQV space was carried out. The proposed approach was verified on two 3 DOF models of underwater vehicles with constraints due to the application of thruster force limitations.

Practical issues in data-driven model-free adaptive control for an omnidirectional mobile manipulator

This article focuses on addressing three practical issues encountered when applying a data-driven model-free adaptive control (MFAC) approach to mobile robots. The first practical issue lies in a common assumption in MFAC schemes that the sign of all elements in pseudo-partial derivative (PPD) should be constant, while it cannot be satisfied if omnidirectional mobile manipulators (OMMs) move with platform rotation. To solve this problem, a new coordinate frame is introduced, which is crucial for applying MFAC to any mobile robots with rotation. The second one is that the initial value setting method for estimation of PPD is unclear. Improper settings may easily lead to control system instability. An initial value setting method for estimation of PPD is proposed with explicit physical interpretation. Lastly, applying the typical MFAC scheme directly to OMM fails to converge well to the desired trajectory. To tackle this, a new data-driven MFAC controller is proposed by incorporating a sliding mode control. Finally, experimental tests on an OMM are carried out to verify the effectiveness of the proposed control scheme. To the best of our knowledge, this is the first MFAC scheme that has been experimentally verified on a prototype mobile robot with rotation.

Event-triggered adaptive neural networks tracking control for incommensurate fractional-order nonlinear systems with external disturbance

The event-triggered adaptive neural networks (NNs) tracking control issue is considered in this paper for a type of incommensurate fractional-order systems (IFOSs) with disturbance. Unlike the existing works for IFOSs, the hypothesis of disturbance-like function and the frequency distributed model are avoided in this study by utilizing the continuity of fractional-order derivative (FOD). Then, based on the radial basis function (RBF) NNs and backstepping method, the adaptive control scheme is proposed to ensure that the reference signal can be tracked by the system output, where the derivative order of adaptive laws does not depend on the one of IFOS. Additionally, to further reduce the burden of communication network, an exponentially convergent term is introduced into traditional dynamic event-triggered mechanism (ETM) and the Zeno behavior is avoided. Finally, two illustrative examples are exhibited to verify the performance of designed control scheme.

Evaluation of supply air temperature control performance with different control strategies at air handling units

Due to its nonlinear feature, supply air temperature control systems at air handling units using single-loop fixed gain control frequently suffer unstable response under dynamic conditions. This paper is aimed at identifying a more effective control strategy to stabilize the valve control and achieve desirable supply air temperature response under various operation conditions by evaluating three control strategies, cascade, gain scheduling and cascade plus gain scheduling controls. Firstly, a control-oriented model is developed and calibrated through open-loop tests. Then, the control issues with single-loop fixed gain control are evaluated through simulations and field tests, which indicates that the system has more aggressive response or becomes unstable under lower load conditions when the chilled-water flow rate is less than 0.1 L/s. Finally, three control strategies are proposed and evaluated. The results reveal that all three proposed controls can achieve better robustness with the integral square error of supply air temperature decreased to 16%, 47% and 5%, respectively, under lower load condition. However, since high-frequency oscillation of the control valve occurs with cascade and cascade plus gain scheduling control, the gain scheduling control is recommended considering a trade-off among the supply air temperature response, valve lifetime and implementation complexity.

Controllability of consensus of multi-agent networks over heterogeneous dynamics

This work investigates controllability issues under the leader–follower framework of consensus problem on multi-agent networks where its agents exhibit the heterogeneous dynamics involving first-, second-, and third-order integrator agents on a continuous time-scale. The communication topology is directed, time-invariant, and the reliability of all interactions are unity. We employ two kinds of consensus protocols that are linear and distributed. The necessary and sufficient criteria for the controllability of followers’ dynamics through the selected leaders are obtained in terms of matrix-rank conditions. We also obtain some necessary conditions of controllability involving eigenvectors of system matrices. It is verified that, if either of the first-, second-, or third-order integrator agents are absent, then the controllability of the network becomes equivalent to the controllability of the communication topology just like those of the networks with homogeneous dynamic agents. Obtained results are verified with illustrative examples.

Computational prediction of muscle synergy using a finite element framework for a musculoskeletal model on lower limb.

Previous studies have demonstrated that the central nervous system activates muscles in module patterns to reduce the complexity needed to control each muscle while producing a movement, which is referred to as muscle synergy. In previous musculoskeletal modeling-based muscle synergy analysis studies, as a result of simplification of the joints, a conventional rigid-body link musculoskeletal model failed to represent the physiological interactions of muscle activation and joint kinematics. However, the interaction between the muscle level and joint level that exists in vivo is an important relationship that influences the biomechanics and neurophysiology of the musculoskeletal system. In the present, a lower limb musculoskeletal model coupling a detailed representation of a joint including complex contact behavior and material representations was used for muscle synergy analysis using a decomposition method of non-negative matrix factorization (NMF). The complexity of the representation of a joint in a musculoskeletal system allows for the investigation of the physiological interactions in vivo on the musculoskeletal system, thereby facilitating the decomposition of the muscle synergy. Results indicated that, the activities of the 20 muscles on the lower limb during the stance phase of gait could be controlled by three muscle synergies, and total variance accounted for by synergies was 86.42%. The characterization of muscle synergy and musculoskeletal biomechanics is consistent with the results, thus explaining the formational mechanism of lower limb motions during gait through the reduction of the dimensions of control issues by muscle synergy and the central nervous system.

How (Not) To Wrong Others with Our Thoughts: A Liberal Challenge Against the Possibility of Doxastic Wronging

In recent years, a number of authors have claimed that we can wrong each other simply by having certain beliefs—in particular sexist, racist, ableist etc. beliefs—about each other. So far, those who argue for the possibility of so-called doxastic wronging have tried to defend this idea by focusing on issues of doxastic control and coordination. In this paper, I raise a distinctly moral challenge against the possibility of doxastic wronging. I show that the idea of doxastic wronging runs afoul of the liberal principle according to which all moral obligations have to be justifiable vis-à-vis those they presume to bind. In addition, I argue that there is a better way to account for the fundamental intuition driving the debate: instead of assuming the possibility of doxastic wronging and the morally grounded epistemic duty it implies, we should conceptualize what is morally problematic about bigoted beliefs in terms of the harm they constitute for their targets.

Unveiling the Shadows: Exploring the Security Challenges of the Internet of Things (IoT)

The Internet of Things (IoT) has revolutionized the way we interact with the digital world by connecting numerous devices and enabling seamless communication and data sharing. However, the widespread adoption of IoT has brought forth significant security challenges. This research paper aims to provide a comprehensive analysis of the security challenges faced in the IoT ecosystem. The paper discusses various security vulnerabilities, including device-level vulnerabilities, network security threats, data privacy concerns, and authentication and access control issues. Furthermore, the paper explores existing security solutions and proposes strategies to mitigate the identified challenges. By addressing these security challenges, organizations and individuals can deploy and utilize IoT devices and systems in a more secure and trusted manner. Key Words: Internet of Things, IoT, security challenges, device-level vulnerabilities, inadequate authentication, network security threats, data privacy, data confidentiality, authentication, access control, encryption, cryptographic techniques, intrusion detection, prevention systems

Dynamic modeling and control of a solar sail considering large-amplitude nonlinear vibration

The solar sail spacecraft utilizes Solar Radiation Pressure (SRP) to achieve propulsion, which can realize long-term acceleration without fuel consumption, making it an appealing option for deep space exploration and polar-sitter observation. However, because of the large-scale and high-flexibility of the membrane structure, the solar sail poses challenging dynamic and control issues. Precise dynamic modeling and effective control design can provide theoretical guidance for the efficient functioning of solar sail, which are of great significance and urgently need to be studied. In this paper, a dynamic model that can describe the large-amplitude vibrations of the solar sail is established. Additionally, an attitude tracking controller and a cable-based nonlinear vibration controller are designed to control the attitude motion and flexible vibration of the solar sail. The results show that the established nonlinear rigid-flexible coupling dynamic model is more accurate compared to the linear dynamic model. The polynomial fitting method can characterize the nonlinear dynamics of the solar sail extremely effectively while cutting the program runtime to 5% of the original. Two controllers designed in this paper can make the solar sail maneuver follow the desired trajectory accurately while reducing the sail surface vibration by more than 40%. The research outcomes of this paper can provide references for the dynamic study and active control of large-scale membrane spacecraft.

Parliamentary control of the state budget as a myth about fiscal control

The aim of the article is to analysis the issues of parliamentary control of the state budget and to identify the problems associated with the implementation of this control. In particular, the role of the Sejm is discussed in terms of preliminary control (ex ante) concerning the compliance of the bill on the budget with the law, current control (ex dure) consisting in assessing the implementation of the budget law, and subsequent control involving in assessing the implementation (ex post) of the state budget. The analysis made it possible to show that proper implementation of parliamentary budgetary control will be impossible without a reform of the system of public finances involving ensuring the preparation of independent macroeconomic forecasts as a basis for the preparation of draft state financial plans, reducing the number of organizational and legal forms of public financial management, abandoning the reporting of public debt in two different ways, and changing the rules of discharge. From this point of view, efforts should be made to give this control this rank so that it does not remain a myth of fiscal control.

Event-triggered-based fuzzy adaptive tracking control for nonstrict-feedback asymmetric state constrained systems

In this article, a fuzzy adaptive command filtered event-triggered control issue is considered for a category of nonstrict-feedback nonlinear systems under the conditions of asymmetric state constraints and time-varying input delay. Firstly, the nonlinear state constrained system is transformed into a new system without state constraints by utilizing nonlinear mappings, which achieves state constraints while removing the feasibility conditions of virtual control signals. Secondly, unknown nonlinear terms in the novel system are approached by using the fuzzy logic systems, a state observer is established to estimate the unmeasurable states in the system, and an auxiliary system is constructed to make up for the influence of time-varying input delay. In addition, the command filtered technology is introduced to overcome the complexity explosion problem in the conventional backstepping design process. It is shown that the fuzzy adaptive event-triggered control scheme can not only ensure the convergence of the tracking error at the origin and the boundedness of all closed-loop signals, but also lighten the communication burden from the controller to the actuator. Finally, a numerical example and an underwater vehicle system are simulated to verify the availability and feasibility of the developed approach.

Does greater access to employees with information technology capability improve financial reporting quality?

AbstractAlthough information technology (IT) plays an essential role in financial reporting, many companies today lack sufficient human capabilities to utilize IT competently. We examine the association between a firm's access to IT‐capable labor and financial reporting quality (FRQ). We proxy for access to IT‐capable labor using workforce measures in the metropolitan statistical area (MSA) where the firm operates, including (1) the number of IT‐related college degrees relative to the total active workforce, (2) the level of education of IT graduates, (3) the income level of IT graduates, and (4) a composite measure. We find that firms in MSAs with a higher IT‐competent labor force are associated with fewer financial reporting misstatements and internal control issues. This study contributes to the emerging literature stream examining the influence of geographic labor characteristics on firm‐level outcomes and the research on the impact of IT capability on financial reporting processes. We also inform the current movement of integrating IT knowledge into the education curriculum.

Flocking Control for Cucker–Smale Model Subject to Denial-of-Service Attacks and Communication Delays

This paper examines the flocking control issue of the Cucker–Smale model in the presence of denial-of-service (DoS) attacks and communication delays. In the setting of DoS attacks, the attacker only obstructs the information communication between agents during the activation phases, while it concentrates on supplying its own energy during the dormancy phases. Furthermore, the communication delays are assumed to be time-varying and heterogeneous. Firstly, a general control input scheme that defends against DoS network attacks and communication delays is constructed. Secondly, on the basis of the presented control input and the properties of graph theory, the flocking control issue is equivalently transformed into a products convergence issue of infinite sub-stochastic matrices. Finally, an algebraic condition is obtained to formulate all the agents that asymptotically achieve the flocking behavior. Moreover, the obtained theoretical results are verified by a numerical example.

Adaptive Fault-Tolerant Control for a 2-Body Point Absorber Wave Energy Converter Against Actuator Faults: An Iterative Learning Control Approach

In this paper, the design issue of adaptive fault-tolerant control (FTC) is investigated for a class of continuous-time 2-body point absorber wave energy converter (WEC) systems against actuator faults based on the iterative learning approach. The actuator faults considered in this paper contain both the lock-in-place and the loss of effectiveness faults, simultaneously. The WEC dynamic equations, including two moving parts (i.e., the float and the spar), are firstly transformed into a state-space model. Then, a group of novel iterative learning based adaptive multiple controllers are developed to decrease the tracking error between the measurement output and the desired output, and two novel adaptive laws are designed to cope with two types of actuator faults. Based on the theories mentioned above, a novel algorithm is provided to present the operation flows of both adaptive laws and iterative learning. Furthermore, a sufficient condition is obtained with the aid of proper Lyapunov function, such that the related closed-loop faulty-WEC system is asymptotically stable with a guaranteed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$H_{\infty }$</tex-math></inline-formula> performance index. Finally, an example with a set of physical parameters of a WEC dynamic model is worked out to verify the applicability and effectiveness of the proposed iterative learning based adaptive FTC strategy.

Pricing and inventory decision in a two-layer supply chain under the Weibull distribution product deterioration: an application of NSGA-II

Academicians and practitioners have focused a lot of attention on the separate issues of pricing and inventory control in a competitive setting. However, integrating these choices in a competitive environment has received scant attention for deteriorating inventory systems from academics despite being crucial to practitioners. From this perspective, our research focuses on designing a supply chain model with inventory coordination to reflect time systems with improved accuracy and optimal control systems. In this research, we develop a two-layer supply chain model consisting of one manufacturer and one retailer incorporating the inventory classification of the retailer. Price-sensitive market demand and two-parameter time-varying Weibull distribution deterioration have been assumed to develop the mathematical model. First, a collective decision on price and inventory control of a deteriorating product has been evaluated in a duopoly environment. Secondly, to explore the decentralized scenario, we have proposed the NSGA-II algorithm to solve the bi-objective programming problem of the two-layer supply chain. The paper aims to explore product collaborative pricing policies and the inventory decision of the deteriorating item in two-layer supply chain coordination. Finally, numerical research is conducted to execute the centralized supply chain and NSGA-II application in a decentralized supply chain. The research findings can provide valuable insights for members of the two-layer supply chain to make optimal product pricing and inventory scheduling decisions.

PRESTRESSED MULTILAYER DESIGNS OF POLYMER COMPOSITES FOR THE VIBRATION AND NOISE CONTROL OF AIRCRAFTS

This paper presents an approach for designing the compact and miniature infra- and low-frequency vibration isolation systems based on the layered composite elastic elements with adjustable negative and quasi-zero stiffness. New problems of modeling the specified parameters of stiffness and bearing capacity of the elements of a certain geometry under combined mode loading are solved by varying the structure, elasticity and configuration of the layers, and by controlling the local mobility of the binder. The approach is valid with the results of experimental designing and studying the system models. Application of the approach makes a qualitatively change in solving a number of critical issues of vibration and noise control in the aerospace and other promising engineering.

It is time to revisit and re-evaluate Africa’s sub-par emergency surgical delivery

It is time to revisit and re-evaluate Africa’s sub-par emergency surgical delivery