Variable Structure Model Research Articles

BLDC Multi-Motor Speed Synchronization by Leader Following Multi-Agent and Hybrid Control

In this article, a unique and innovative design for addressing the speed synchronization problem in a multi-motor system using Brush less DC (BLDC), motors is presented by utilizing motor back emf equation and rotor position commonly called sensor less technique. In the proposed method, the system is modelled as a consensus problem of leader following multi-agent system (MAS), and a hybrid controller is designed by using Model Reference Adaptive Control (MRAC) along with Variable Structure (VS) control technique of Sliding Mode Control (SMC), herein called Variable Structure Model Reference Adaptive Control (VS-MRAC). The consensus algorithm of MAS (reformed w.r.t motor speed data), is fused with the hybrid controller to reach consensus on speed regulated by proposed hybrid controller. The stability of a system is endorse by designing a Lyapunov function. The efficiency of the proposed methodology is proven by simulations performed in MATLAB and the acquired results validate the success of proposed design methodology.

Coparenting and Parental School Involvement

Parental school involvement is associated with social, psychological, and academic child outcomes. Beyond school, demographic, and individual influences, research on the relationship between family level processes and parental school involvement is limited. Coparenting is a unique family level relationship that influences parental engagement, but its link with parental school involvement is less understood. The goal of this study was to examine the association between coparenting support and biological mothers’ and fathers’ home-based involvement and school-based involvement when the child was 9-years-old. This study also tested whether biological parental union transitions (i.e., parental union dissolution; parental union formation with each other; stable coresident relationship with one another) significantly moderated these relationships, and whether the associations among the variables of interest were empirically stronger for mothers or fathers. Using data from the Fragile Families and Child Wellbeing Study (N = 1896 biological mothers and fathers), the current study utilized multiple-sample latent variable structural equation modeling analyses to explore the above associations. Higher levels of coparenting support were associated with higher levels of mothers’ and fathers’ home-based involvement, and higher levels of fathers’ school-based involvement. Union transitions did not moderate these relationships. The link between coparenting support and home-based involvement was significantly stronger for mothers, and the link between coparenting support and school-based involvement was significantly stronger for fathers. Coparenting support may be important to understanding the many components that influence parental school involvement.

Predicting the Intention to Use Condoms and Actual Condom Use Behaviour: A Three-Wave Longitudinal Study in Ghana.

Growing cross-sectional research shows that the theory of planned behaviour (TPB) is robust in predicting intentions to use condoms and condom use behaviour. Yet, little is known about the TPB's utility in explaining intentions to use condoms and condom use behaviour over time. This study used a longitudinal design and latent variable structural equationmodelling to test the longitudinal relationships postulated by the TPB. School-going youths in Ghana provided data on attitudes, subjective norms, perceived control, intentions, and behaviour regarding condom use at three time points, spaced approximately three months apart. As predicted by the TPB, the results showed that attitudes were significantly positively associated with intentions to use condoms over time. Contrary to the TPB, subjective norms were not significantly associated with intentions to use condoms over time. Perceived control did not predict intentions to use condoms over time. Moreover, intentions to use condoms were not significantly associated with self-reported condom use over time. These results suggest that school-going youths in Ghana may benefit from sex education programmes that focus on within-subject attitude formation and activation. The theoretical and methodological implications of these results are discussed.

A latent structural equation model of protective behaviors and pressure ulcer outcomes among people living with spinal cord injury.

Cross-sectional. To develop a latent structural model to demonstrate the relationship between factor structures of protective health behaviors and pressure ulcer (PrU) outcomes among participants with spinal cord injury (SCI). Data were collected at a large specialty hospital and analyzed at a medical university in the Southeastern USA. A total of 1871 participants with traumatic SCI of at least 1 year duration were included. A latent PrU variable was measured by four observable PrU-related outcomes. Latent variable structural equation modeling was performed to assess the relationship between latent protective behavior (fitness and productive activities) and latent PrU outcome. Several exogenous variables were included: sex, age, race, marital status, injury severity and years since injury. The protective behavior dimension had a significant direct effect on the latent PrU (direct effect=-0.275, P<0.01). All direct relationships between protective behavior dimension and healthy behaviors were also significant (rfit=0.899 and rproductive activity=0.568). Relationships between the latent PrU and fitness (indirect effect=-0.247) and productive activities (indirect effect=-0.156) were mediated through the protective behavior dimension. Participants who were African American, had higher injury levels, and had longer time since SCI were more likely to have worse PrU outcomes. The overall findings of this study suggest the need to enhance healthy behaviors to prevent adverse PrU outcomes, especially among people who are African American, have longer time since SCI and have higher level of SCI.

Mechanism design and motion ability analysis for wheel/track mobile robot

A wheel/track mobile robot with a one-way tail rod is studied. First, from the analysis of its performance, the mechanical structure of the wheel/track mobile robot is designed and the hardware composition of its control system is given. Second, based on the analysis of its variable structure movement process, the variable structure model of wheel/track mobile robot is established using the geometry analysis method. Third, two kinds of analysis are proposed. One is analysis of the wheel movement on flat ground. Another is track obstacle-crossing kinematics of the robot, in which the conditions for its stairs-climbing are determined. Then, the dynamical model of stairs-climbing is established either in wheel mode or in track mode using the classical mechanics analysis on the robot during the stairs-climbing process. Through simulation and experiments, the effectiveness of the model and the evaluation method of the wheel/track mobile robot in stairs-climbing are verified, which can provide design and analysis foundations for the wheel/track mobile robot.

Discrete variable structure model reference adaptive control using only input-output measurements

Designing an adequate controller for a plant with an arbitrary relative degree is still an active area of research. In this paper, a discrete variable structure model reference adaptive control using only input-output measurements (DVS-MRAC-IO) for not strictly positive real systems with a relative degree of two is proposed. In order to show the effectiveness of the proposed controller, a detailed stability analysis is studied using Lyapunov theory. Further, a straightforward generalization of DVS-MRAC-IO for systems with arbitrary relative degree is presented. Numerical results are used to show the effectiveness of the proposed methods.

Translating Dental Flossing Intentions into Behavior: a Longitudinal Investigation of the Mediating Effect of Planning and Self-Efficacy on Young Adults.

Although poor oral hygiene practices can have serious health consequences, a large number of adults brush or floss their teeth less than the recommended time or not at all. This study examined the mediating effect of two key self-regulatory processes, self-efficacy and planning, as the mechanisms that translate dental flossing intentions into behavior. Participants (N=629) comprised young adults attending a major university in Queensland, Australia. A longitudinal design guided by sound theory was adopted to investigate the sequential mediation chain for the effect of dental flossing intentions (time 1) on behavior (time 3) via self-efficacy and planning (time 2). A latent variable structural equation model with standardized parameter estimates revealed the model was a good fit to the data. Controlling for baseline flossing, the effect of intentions on behavior was mediated via self-efficacy and planning, with 64% of the flossing variance accounted for by this set of predictors. Controlling for age and sex did not change the results. The results extend previous research to further elucidate the mechanisms that help to translate oral hygiene intentions into behavior and make a significant contribution to the cumulative empirical evidence about self-regulatory components in health behavior change.

Building a pantheoretical model of dehumanization with transgender men: Integrating objectification and minority stress theories.

With a national sample of 304 transgender men, the present study tested a pantheoretical model of dehumanization (Moradi, 2013) with hypotheses derived from objectification theory (Fredrickson & Roberts, 1997), minority stress theory (Meyer, 2003), and prior research regarding men's body image concerns. Specifically, we tested common objectification theory constructs (internalization of sociocultural standards of attractiveness [SSA], body surveillance, body satisfaction) as direct and indirect predictors of compulsive exercise. We also examined the roles of transgender-specific minority stress variables-antitransgender discrimination and transgender identity congruence-in the model. Results of a latent variable structural equation model yielded mixed support for the posited relations. The direct and indirect interrelations of internalization of SSA, body surveillance, and body satisfaction were consistent with prior objectification theory research, but only internalization of SSA yielded a significant direct relation with compulsive exercise. In addition, neither internalization of SSA nor body surveillance yielded significant indirect relations with compulsive exercise. However, antitransgender discrimination yielded predicted indirect relations with body surveillance, body satisfaction, and compulsive exercise, with transgender congruence playing a key mediating role in most of these relations. The implications of this pantheoretical model for research and practice with transgender men are discussed. (PsycINFO Database Record

A Test of Social Cognitive Theory to Explain Men's Physical Activity During a Gender-Tailored Weight Loss Program.

Physical inactivity is a leading contributor to the burden of disease in men. Social-cognitive theories may improve physical activity (PA) interventions by identifying which variables to target to maximize intervention impact. This study tested the utility of Bandura's social cognitive theory (SCT) to explain men's PA during a 3-month weight loss program. Participants were 204 overweight/obese men (M [SD] age = 46.6 [11.3] years; body mass index = 33.1 [3.5] kg/m2). A longitudinal, latent variable structural equation model tested the associations between SCT constructs (i.e., self-efficacy, outcome expectations, intention, and social support) and self-reported moderate-to-vigorous PA (MVPA) and examined the total PA variance explained by SCT. After controlling for Time 1 cognitions and behavior, the model fit the data well (χ2 = 73.9, degrees of freedom = 39, p < .001; normed χ2 = 1.9; comparative fit index = 0.96; standardized root mean residual = 0.059) and explained 65% of the variance in MVPA at Time 2. At Time 2, self-efficacy demonstrated the largest direct and total effects on MVPA (βdirect = .45, p < .001; βtotal = .67, p = .002). A small-to-medium effect was observed from intention to MVPA, but not from outcome expectations or social support. This study provides some evidence supporting the tenets of SCT when examining PA behavior in overweight and obese men. Future PA and weight loss interventions for men may benefit by targeting self-efficacy and intention, but the utility of targeting social support and outcome expectations requires further examination.

Students' views on mathematics in single-sex and coed classrooms in Ghana

In this study, we investigated students’ views on themselves as learners of mathematics as a function of school-by-sex (N = 2034, MAge = 18.49, SDAge = 1.25; 12th-grade; 58.2% girls). Using latent variable Structural Equation Modeling (SEM), the measurement and structural equivalence as well as the equality of latent means of scores across single-sex and coed schools were tested. Findings regarding the latent mean differences revealed that girls in single-sex schools had significantly higher mathematics self-confidence than did students’ in coed schools. Girls in coed schools had significantly lower mathematics self-concepts than did boys in single-sex, girls in single-sex and boys in coed schools. Girls in single-sex schools had significantly higher family encouragement than students’ in all other school types. Moreover, a more complex dynamics were found on the teacher quality variate. This paper argues for a deeper understanding of sex-school interaction and of possible causes of students’ views on mathematics.

Different Effects of Cognitive Shifting and Intelligence on Creativity

AbstractThe relationship between creativity and executive control has long been controversial. Some researchers view creative thinking as a defocused process with little executive control involvement, whereas others claim that executive control plays a vital role in creative thinking. In this study, we focused on one subcomponent of executive control, cognitive shifting, and examined its relationship with creativity by using latent variable analysis and structural equation modeling. We also analyzed whether this relation was mediated by intelligence. The results showed that: (a) cognitive shifting ability had a positive relationship with creativity, but only on the quantitative aspects (fluency and flexibility); (b) Intelligence had a positive relationship with both quantitative and qualitative aspects (originality) of creativity, and its effect on qualitative aspect was stronger than that on the quantitative aspect; (c) There was a mediating effect of intelligence on the relationship between creativity cognitive and shifting.

A Tool for Predicting the Dynamic Response of Biotrickling Filters for VOC Removal

This article presents the development of a MATLAB® computer program to simulate the performance of biotrickling filters. Since these filters behave differently during spraying and nonspraying cycles, the presented simulation tool is built on top of a mathematical description of each situation. The resulting variable-structure model is then used as the basis for simulation experiments. The model presented herein represents the first attempt to take into account the variable spraying pattern usually found in industrial installations. Overall, the software is flexible and easy to use, allowing the user to specify the emission concentration pattern, the gas concentration pattern, as well as the spraying cycle periods for up to two different emission patterns per day. The model is able to predict experimental data from a biotrickling filter treating isopropanol under intermittent conditions of loading and spraying. Simulation examples are then provided to study the effect of variable inlet concentrations and gas flow rates.

Family Relational Health, Psychological Resources, and Health Behaviors: A Dyadic Study of Military Couples.

In addition to facing stressors that are typical of life course development (e.g., marital struggles, balancing work/family demands), military families face additional stress attributed to their military context (e.g., deployments, relocations). Using a systems framework and stress process perspective, this study examined military couples' relational health, as a gauge for how couples collectively cope and address challenges as a united front and how their relational health influences crucial health behaviors (sleeping and eating) through the promotion or erosion of psychological resources (N = 236 couples). This study evaluated a latent variable structural equation dyadic model whereby each partner's perspective of their family's relational health was hypothesized to influence their own eating and sleeping behaviors (actor effects), as well as the eating and sleeping behaviors of their spouse (partner effects). The role of psychological resources (high self-efficacy, few depressive symptoms, and minimal anxiety) as a mechanism linking family functioning to health behaviors was also examined. Overall, the findings supported the hypothesized model, particularly for actor (intraindividual) effects. Discussion is provided pertinent to service providers and researchers, including the importance of improving, or maintaining, family relational health, as a means for encouraging positive health behaviors among active duty military members and their spouses.

Intensional Couplings in Variable-Structure Models

In modular, hierarchical modeling, couplings (connections) describe and constrain the communication, and thus interaction, between model components. Defining couplings between a large set of components in an extensional manner—listing all existing couplings individually—often proves to be rather tedious. Moreover, if models change their structure, that is, composition and interaction patterns and, in some cases, even their interfaces during simulation, questions about the consistency of the couplings arise. For instance, an extensionally defined coupling may refer to a model that no longer exists. Instead, an intensional coupling definition, based on attributes of the components to couple and dynamically translated into concrete couplings during simulation, promises to alleviate these problems. We propose a concept that combines a flexible, yet expressive, definition of couplings that rests on component interfaces announcing attributes of interest. However, intensional couplings come at a price, as they need to be translated during simulation; in variable-structure models, this translation has to happen frequently. We illuminate our concept based on a revision of the modeling formalism Multilevel Discrete Event System Specification ( ML - DEVS ). Developed for multilevel modeling and simulation, ML - DEVS exhibits another alternative to intensional couplings, that is, sharing parts of model states for up- and downward causation. The intricate interplay between these different types of couplings is revealed in the abstract simulator of ML - DEVS .

Robust control of robotic manipulators based on left inverse system and variable structure model reference adaptive control

SummaryThis work proposes a control structure to be applied to robotic manipulators, which are articulated mechanical systems composed of links connected by joints. The proposed controller can be divided into two parts. The first one is a left inverse system, which is used to decouple the dynamic behavior of the joints. The second is a sliding mode controller, which is applied for each decoupled joint. It is important to note that the proposed structure, using only input/output measurements, reduces the control signal ‘chattering’, and it is robust to parametric uncertainties. Besides all the characteristics presented, the proposed structure simplifies the design of sliding mode controller to be applied in robotic manipulators. All these features are verified by simulations. Copyright © 2016 John Wiley &amp; Sons, Ltd.

A taxonomy of path-related goodness-of-fit indices and recommended criterion values.

Almost all goodness-of-fit indexes (GFIs) for latent variable structural equation models are global GFIs that simultaneously assess the fits of the measurement and structural portions of the model. In one sense, this is an elegant feature of overall model GFIs, but in another sense, it is unfortunate as the fits of the 2 different portions of the model cannot be assessed independently. We (a) review the developing literature on this issue, (b) propose 6 new GFIs that are designed to evaluate the structural portion of latent variable models independently of the measurement model, (c) that are couched within a general taxonomy of James, Mulaik, and Brett's (1982) Conditions 9 and 10 for causal inference from nonexperimental data, (d) conduct a Monte Carlo simulation of the usefulness of these 6 new GFIs for model selection, and (e) on the basis of simulation results provide recommended criteria for 4 of them. Supplemental analyses also compare 2 of the new GFIs to 2 other structural model selection strategies currently in use. (PsycINFO Database Record

Lateral roll control of vehicle based on UKF and sliding model control

A 3-DOF dynamical model of vehicle is built in this paper by using MATLAB/Simulink. Considering nonlinear tyre performance, the magic formula tyre model is used to improve the accuracy of the model. For the difficulty of measuring the roll angle and roll rate, an observer for the roll angle and roll rate based on the dynamical model of vehicle and kinematic relations is designed in this paper, tracking the roll angle and roll rate in the process of driving based on the easily measured status parameters, using unscented Kalman filter. Then, this method is tested through experiments. Finally, based on the estimated roll angle and roll rate, a roll stability controller based on the sliding model variable structure control theory is designed.

Variable Structure Model of an Articulated Robotic Arm

In this paper, a novel method for the structure variable modeling of a two links articulated robotic arm is considered. First, the dynamic model of the robotic arm is obtained. Second, two different equilibrium points yield two different models which are derived from the first model. The different models are presented in simulations.

Narcissistic Vulnerability and Grandiosity as Mediators Between Insecure Attachment and Future Eating Disordered Behaviors: A Prospective Analysis of Over 2,000 Freshmen.

This study aimed to build on existing literature by examining the potential mediating role of two variants of narcissism (grandiosity and vulnerability) in explaining part of the underlying mechanism by which insecure (avoidant and anxiety) attachment affects behavioral elements of eating pathology (dieting and bulimic behaviors). Longitudinal data collected from 2,055 freshman college students (52.2% women; mean age 18.34 years) were analysed using a latent variable structural equation modelling approach, controlling for initial levels of the endogenous (i.e., dependent) latent variables and holding body mass index, anxiety, stress, depression, and self-esteem levels as time-varying covariates. The effect of attachment anxiety on future bulimic behaviors was fully mediated through vulnerable narcissism (i.e., no significant direct link between attachment anxiety and bulimic behaviors), whereas grandiose narcissism fully mediated the association between attachment avoidance and future dieting behaviors. Dieting also predicted future bulimic behaviors and served as an additional (full) mediator between grandiose narcissism and bulimic behaviors. Differences in the strength of these associations across gender were not observed, and all indirect effects were statistically significant. Overall, the findings (a) seem to support the theoretical postulations linking different insecure attachment experiences to different narcissistic tendencies, (b) imply that specific insecure attachment patterns may pass through different mediating pathways (narcissistic grandiosity and vulnerability) to specific behavioral elements of eating pathology (dieting and bulimic behaviors) regardless of gender, and (c) suggest that individuals with high grandiose narcissistic levels may not be protected from bulimic behaviors as previously indicated.

Quality management, job-related contentment and performance

Purpose– The purpose of this paper is to investigate whether a quality management (QM) philosophy underlies the joint use of operations and human resource management practices, and the relationships with job-related contentment and performance.Design/methodology/approach– Data from an economy-wide survey are used to test hypotheses via latent variable analyses (latent trait and latent class models) and structural equation models. The sensitivity of each path is then assessed using regression models.Findings– Different elements rather than a unified philosophy are identified. A managerial approach that integrates total QM and just-in-time procedures is rare, but is associated with the quality of the product or service delivered. Labor productivity and quality are independent of the level of job-related contentment in the workplace. Although the average workforce is content, high involvement management and motivational support practices are associated with job anxiety. On the positive side, job enrichment is linked to labor productivity, thus suggesting potential gains through job design.Originality/value– The study adds evidence from a national sample about a comprehensive range of management practices, and suggests distinct outcomes from different elements of QM. Additionally, it shows that performance expectations based on previous studies may not hold in large nationwide heterogeneous samples.