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For output-constrained switched systems, uniformly local stabilization problem via state feedback is addressed. A unified tool, a common tangent-type barrier Lyapunov function (Tan-BLF), is developed to deal with the stabilization problem of switched systems and to cope with constraints imposed on system output with or without. Then, combining adding a power integrator technique (APIT) and the developed common barrier Lyapunov function, state-feedback stabilizing laws are designed systematically to make the resultant closed-loop switched systems asymptotically stable while preventing the violation of output constraints. The efficiency of the proposed method is illustrated by numerical results. [ABSTRACT FROM AUTHOR]

This article proposes a time-domain procedure for a non-Gaussian stationary random vibration test with prescribed power spectral densities. Previous procedures for generating non-Gaussianity suffered from certain defects. For example, zero-memory nonlinear transformation, an algorithm frequently applied to transform Gaussian signals into non-Gaussian signals, often produces changes in both auto-power spectral densities and cross-power spectral densities, which might result in control instability under certain circumstances. In this article, the authors propose a different approach for the zero-memory nonlinear function. First, a time-domain procedure for a non-Gaussian random test is introduced. Second, a rescaling method is applied to correct the magnitude amplification on the auto-power spectral density because of zero-memory nonlinear transformation. We offer experience formulas in this method to adjust the auto-power spectral density of both super-Gaussian and sub-Gaussian responses. Third, a control strategy using a finite impulse response filter is proposed to further improve the auto-power spectral density if the shape of the auto-power spectral density is distorted. The kurtosis loss induced by the filtering process is also analysed and a corresponding solution is put forward to ease the reduction. Numerical test and a biaxial shaker table test are conducted to validate the availability and superiority of the proposed procedure. [ABSTRACT FROM AUTHOR]

The dynamic model is significant for the analysis of the vibrational characteristics of the wheeled tractor system with implement and front axle hydropneumatic suspension. In this work, the nonlinear stiffness and damping equations are derived first. The dynamic coupling relationship among cabin, three-point hitch structure, and implement are figured out, and the dynamic model of the half agricultural wheeled tractor/implement system is presented considering the effects of three-point hitch structure, passive silent blocks of cabin, and front axle hydropneumatic suspension together. To validate the model, the power spectral densities (PSDs) of the driver seat, cabin, chassis, and implement acquired from numerical simulations are compared with those from experiments, respectively. Under different forward speeds, two groups of results match well. Based on the model, the influences of passive cabin suspension, implement, and front axle hydropneumatic suspension on the dynamical characteristics of the tractor system are investigated. Results indicate that the front axle hydropneumatic suspension will deteriorate the ride comfort of the driver but improve the handing stability. The passive cabin suspension reduces the operational stability while improving much more ride comfort than the front axle hydropneumatic suspension does. The driver's comfortableness will be increased due to implement; meanwhile, handling stability will be compromised. Besides, the impacts of initial nitrogen volume, pressure of accumulators, and orifice diameter of throttle valves on the vibration characteristics of the tractor system are also inspected. [ABSTRACT FROM AUTHOR]

In traditional models, only the effect of temperature change of bearings on the heat generation power and thermal contact resistance is considered. But the effect of bearing stiffness and flexibility of crank shaft on the heat generation power is often neglected, thereby impairing the accuracy of the thermal analysis. Therefore, a better thermal model is demanded to accurately analyse the thermal characteristics of a Multi-link ultra-precision press system (MLUPPS). By combining the effect of stiffness of bearing and flexibility of crank shaft on the heat generation power, an improved thermal model of MLUPPS was developed in this work. The model was based on as-derived kinematic and dynamic equations of Multi-link transmission mechanism (MLTM) and flexible dynamic model of crankshaft-bearing system. The dimension chain of thermal error is constructed to analyse the dimensional error between the slider and the work table at the position of Bottom dead point (BDP). The developed thermal model of MLUPPS and its analysis results from this model are in good agreement with the measurement results, and that is more accurate than the traditional one. The simulation results reveal that the maximum temperature rise of MLUPPS occurs at the crank shaft, and the dimensional error between the slider and the work table at the position of BDP is due to thermal expansion fluctuation before the generation and conduction of heat power reaches balance. The temperature rise and thermal error of MLUPPS under different rotation speeds, piling forces and bearing stiffness were also studied. [ABSTRACT FROM AUTHOR]

It is necessary to establish a dynamic model to predict and evaluate the dynamic performance of closed high-speed press system during design procedure, when it is impossible to carry out the test of prototype. In this work, a dynamic model for the closed high-speed press system is developed to predict and evaluate its dynamic performance. Unlike in previous models where the press frame is considered to be a single mass and the effects of the transmission mechanism and complex frame structure are neglected, the present model can be used to analyze the dynamic response of a multi-body vibration-impact system treating it as a coupled one. The simulation results reveal that the dynamic responses of press under piling condition include a transient impact and a free vibration process. The vibration acceleration and velocity curves of the upper beam of the closed high-speed press decrease with the increasing speed of rotation. In contrast, vibration acceleration and velocity curves of the lower beam of the press increase with the increasing rotation speed. The experimental results demonstrate that the dynamic model proposed herein is consistent with the actual working state of the closed high-speed press and the validity of the dynamic model is verified. [ABSTRACT FROM PUBLISHER]

In the framework of digital control, finite-time stabilization of input-delay switched systems with saturating actuators is investigated. Digital state feedback controllers (DSFC) and digital output feedback controllers (DOFC) are proposed to make input-delay switched systems finite-time stable for the cases that states are available or unavailable. Sufficient conditions for finite-time stability (FTS) of the resultant closed-loop systems are also presented. A constructive way is used to proof the main results, which is constructing an exact comparison function. Numerical examples are employed to verify the efficiency of the methods proposed in this paper. [ABSTRACT FROM AUTHOR]

Background: Depression is common and serious among elderly patients. The treatment of elderly depression is often delayed owing to insufficient diagnosis, which eventually leads to adverse consequences., Aims: To explore the association between the parameters of the Comprehensive Geriatric Assessment and depression in elderly patients., Methods: A cross-sectional study of 211 outpatients and inpatients aged ≥ 65 years from the Comprehensive Geriatric Assessment database was conducted. A Comprehensive Geriatric Assessment inventory was prepared by compiling and screening general characteristics, chronic diseases (cardiovascular disease, diabetes, and peptic ulcer disease), nutritional status, daily living ability, anthropometric measurements (body mass index (BMI), upper arm circumference, and calf circumference), and blood biochemical indicators (hemoglobin, albumin, prealbumin, triglycerides, and low-density lipoprotein cholesterol). The Geriatric Depression Scale was also conducted for each elderly patient to screen for depression. A multivariable logistic regression analysis was used to determine the association between the parameters of the Comprehensive Geriatric Assessment and geriatric depression., Results: There were 63 patients in the depression group with a median age of 84.00 years, and 148 patients in the non-depression group with a median age of 78.50 years. After controlling for confounders, the risk of depression in elderly patients with cardiovascular diseases was 6.011 times higher than that in those without cardiovascular diseases ( p < 0.001); and the risk of depression in elderly patients with peptic ulcer diseases was 4.352 times higher than that in those without peptic ulcer diseases ( p < 0.001); the risk of depression in elderly patients decreased by 22.6% for each 1-point increase in the Mini Nutritional Assessment ( p < 0.001). The risk of depression in elderly patients decreased by 19.9% for each 1-point increase in calf circumference ( p = 0.002), and by 13.0% for each 1-point increase in albumin ( p = 0.014)., Conclusion: Our findings suggest that Comprehensive Geriatric Assessment parameters, such as cardiovascular disease, peptic ulcer disease, Mini Nutritional Assessment score, calf circumference, and albumin, were associated with depression. The Comprehensive Geriatric Assessment can assist in the early identification of depression in the elderly population., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Ju, Liu, Zhang, Lin, Zheng and Leng.)