Robust Distributed Control Protocols for Large Vehicular Platoons with Prescribed Transient and Steady State Performance

In this paper, we study the longitudinal control problem for a platoon of vehicles with unknown nonlinear dynamics under both the predecessor-following and the bidirectional control architectures. The proposed control protocols are fully distributed in the sense that each vehicle utilizes feedback from its relative position with respect to its preceding and following vehicles as well as its own velocity, which can all be easily obtained by onboard sensors. Moreover, no previous knowledge of model nonlinearities/disturbances is incorporated in the control design, enhancing in that way the robustness of the overall closed loop system against model imperfections. Additionally, certain designer-specified performance functions determine the transient and steady-state response, thus preventing connectivity breaks due to sensor limitations as well as inter-vehicular collisions. Finally, extensive simulation studies and a real-time experiment conducted with mobile robots clarify the proposed control protocols and verify their effectiveness.Comment: IEEE Transactions on Control Systems Technology, accepte

Funnel Control Under Hard and Soft Output Constraints

This paper proposes a funnel control method under time-varying hard and soft output constraints. First, an online funnel planning scheme is designed that generates a constraint consistent funnel, which always respects hard (safety) constraints, and soft (performance) constraints are met only when they are not conflicting with the hard constraints. Next, the prescribed performance control method is employed for designing a robust low-complexity funnel-based controller for uncertain nonlinear Euler-Lagrangian systems such that the outputs always remain within the planned constraint consistent funnels. Finally, the results are verified with a simulation example of a mobile robot tracking a moving object while staying in a box-constrained safe space.Comment: 9 pages, 6 figures, submitted to 61st IEEE Conference on Decision and Control 202

Consumer default and optimal consumption decisions

We examine the optimal consumption decisions of households in a micro-founded framework that assumes two financial frictions: heterogeneity between borrowing and saving households, and endogenous default. We study default in the context of two-period overlapping processes of consumer behavior, assuming that penalty costs are imposed on borrowers if they are delinquent in the first period and are subsequently refinanced by banks. The utility function of borrowing households is specified to include a term reflecting strategic decisions as regards non-payment of debt. From the solution of the household optimization problem, we derive an augmented Euler equation for consumption, which is a function inter alia of an expected default factor. We use this equation to calculate in a static equilibrium the optimal value of the percentage of debt repaid. We finally provide an ordering by size of the household discount factor: borrowers who do not repay all of their loans have the lowest discount factor, followed in turn by borrowers who fully repay them and by savers

Acute effects of whey protein isolate on blood pressure, vascular function and inflammatory markers in overweight postmenopausal women.

Previous evidence indicates that chronic consumption of dairy whey proteins has beneficial effects on CVD risk factors. The present study investigated the postprandial effects of whey protein isolate on blood pressure, vascular function and inflammatory markers in overweight and obese postmenopausal women. This was a randomised, three-way cross-over design study where twenty overweight and obese postmenopausal women consumed a breakfast meal in conjunction with one of three supplements: 45 g whey protein isolate, 45 g sodium caseinate or 45 g of a glucose control. Fasting and postprandial blood samples, blood pressure and pulse wave analysis readings were taken for up to 6 h. After consumption of the meal, both systolic and diastolic blood pressure, and augmentation index (AI) decreased initially for all interventions and gradually returned to baseline levels by 6 h. However, there were no significant differences in AI, systolic or diastolic blood pressure within or between the glucose control, casein or whey groups. There were also no significant group effects on plasma inflammatory markers (IL-6, TNF-a and C-reactive protein). The health effects previously seen with chronic whey protein ingestion were not seen in the acute 6 h postprandial period in relation to blood pressure, vascular function or inflammatory markers when compared with casein and a glucose control. This suggests that such effects are better observed from the long-term consumption of whey proteins

Consumer default and optimal consumption decisions

We examine the optimal consumption decisions of households in a micro-founded framework that assumes two financial frictions: heterogeneity between borrowing and saving households, and endogenous default. We study default in the context of two-period overlapping processes of consumer behavior, assuming that penalty costs are imposed on borrowers if they are delinquent in the first period and are subsequently refinanced by banks. The utility function of borrowing households is specified to include a term reflecting strategic decisions as regards non-payment of debt. From the solution of the household optimization problem, we derive an augmented Euler equation for consumption, which is a function inter alia of an expected default factor. We use this equation to calculate in a static equilibrium the optimal value of the percentage of debt repaid. We finally provide an ordering by size of the household discount factor: borrowers who do not repay all of their loans have the lowest discount factor, followed in turn by borrowers who fully repay them and by savers

The differentiated effects of minimum wage reforms on unemployment Evidence from the Greek labor market

The paper studies the relative effect between two groups, a treatment group of low-wage workers and a control group of high-wage workers, when a minimum wage reform is introduced. The empirical analysis uses a rich dataset from the Greek labor market over the period between 2010 and 2020. The study examines whether the employees’ responses and the potential effects of two different minimum wage reforms on unemployment were heterogenous. Our results are straightforward: among the two groups, the relative possibility of job loss is associated with an increase in the minimum wage, while the relative possibility of job search difficulty is strongly affected by a minimum wage cut. The former result is getting worse for employees who engaged in a minimum wage-intensive sector in the previous year and are now inactive. The latter result is reinforced for very young workers

On-Line Identification of Autonomous Underwater Vehicles through Global Derivative-Free Optimization

We describe the design and implementation of an on-line identification scheme for Autonomous Underwater Vehicles (AUVs). The proposed method estimates the dynamic parameters of the vehicle based on a global derivative-free optimization algorithm. It is not sensitive to initial conditions, unlike other on-line identification schemes, and does not depend on the differentiability of the model with respect to the parameters. The identification scheme consists of three distinct modules: a) System Excitation, b) Metric Calculator and c) Optimization Algorithm. The System Excitation module sends excitation inputs to the vehicle. The Optimization Algorithm module calculates a candidate parameter vector, which is fed to the Metric Calculator module. The Metric Calculator module evaluates the candidate parameter vector, using a metric based on the residual of the actual and the predicted commands. The predicted commands are calculated utilizing the candidate parameter vector and the vehicle state vector, which is available via a complete navigation module. Then, the metric is directly fed back to the Optimization Algorithm module, and it is used to correct the estimated parameter vector. The procedure continues iteratively until the convergence properties are met. The proposed method is generic, demonstrates quick convergence and does not require a linear formulation of the model with respect to the parameter vector. The applicability and performance of the proposed algorithm is experimentally verified using the AUV Girona 500. © 2013 IEEE

The impact of the Covid-19 lockdown on the i-banking use: An empirical inquiry from Greece

This paper studies the impact of Covid-19 lockdown on the i-banking use. During the first lockdown period in Greece, between April 13th and May 3rd, 2020, we conducted a survey of 4,807 respondents between 18 and 64 years old who participated in the labor force and used internet. The sample was appropriately weighted to accurately reflect the real population. The main result is straightforward: more days in a lockdown is associated with an increased possibility for further i-banking use. We also provide important insights to financial services’ providers by pointing out female gender, increasing age, living in a metropolitan area, and job security status as the most crucial predictors for shaping changing i-banking use

The link between consumption and leisure under Cobb-Douglas preferences:Some new evidence

The assumption of multiplicative non-separable (Cobb-Douglas) consumer preferences is a key assumption for analyzing the interdependence of consumption and leisure choices. In this paper we solve the consumer utility maximization problem under these preferences and derive a simultaneous system of two equations corresponding to a static and an inter-temporal equation of consumption and leisure choice. The system is estimated with GMM to obtain consistent estimates of the consumer's preference parameters, of which the relative weight of consumption in the utility function is found to be much higher than that commonly assumed in DSGE model calibration exercises