scholarly journals Generalized Reliability Analysis of Mechanical Systems with Imperfect Maintenance

2022 ◽  
Vol 2022 ◽  
pp. 1-14
Author(s):  
Peng Gao ◽  
Liyang Xie
Keyword(s):  
Mechanical Systems ◽  
Strength Degradation ◽  
Design Parameters ◽  
Time Varying ◽  
Imperfect Maintenance ◽  
Working Mechanism ◽  
Load Effect ◽  
Clear Physical Meaning ◽  
Reliability Models ◽  
Failure Correlation

Generalized reliability models and failure rate models of mechanical systems are developed in this paper according to the system working mechanism, which take the design parameters as input. The models consider strength degradation and imperfect maintenance. Besides, the models take into account the failure correlation caused by homologous load effect and the maintenance correlation owing to group maintenance. Unlike traditional reliability models, the models do not rely on empirical assumptions when considering failure correlation and maintenance correlation and have clear physical meaning. Moreover, the correctness and effectiveness of the models are verified by Monte Carlo simulations. Finally, the influences of failure correlation and maintenance correlation on generalized reliability, the influences of failure correlation on maintenance correlation, and the influences of maintenance correlation on failure correlation are analyzed via numerical examples. The results show that failure correlation and maintenance correlation have great influences on generalized reliability, and the interaction between the two correlation shows obvious time-varying characteristics.

scholarly journals Fuzzy Dynamic Reliability Models of Parallel Mechanical Systems Considering Strength Degradation Path Dependence and Failure Dependence

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Peng Gao ◽  
Liyang Xie
Keyword(s):  
Path Dependence ◽  
Mechanical Systems ◽  
Strength Degradation ◽  
Sensitivity Function ◽  
Bolted Joint ◽  
Paper Strength ◽  
Dynamic Reliability ◽  
Reliability Models ◽  
Proposed Model ◽  
Failure Dependence

Fuzzy dynamic reliability models of mechanical parallel systems with respect to stress parameters and strength parameters are developed in this paper. Strength degradation path dependence (SDPD) and failure dependence of components in the system are two main problems to be addressed in developing fuzzy dynamic reliability of mechanical systems, which are taken into account in the proposed reliability models. In addition, the SDPD sensitivity function and the failure dependence sensitivity function are defined to analyze the influences of the fuzzy characteristics of stress on the effects of SDPD and failure dependence of mechanical components on dynamic reliability. The bolted joint systems for connection between launch vehicle and satellite are chosen as illustrative examples to demonstrate the proposed model. Moreover, Monte Carlo simulations are carried out to validate the effectiveness of the proposed models. The results show that SDPD and failure dependence of components have significant impacts on fuzzy dynamic reliability of mechanical systems. Besides, the influences of the fuzzy characteristics of stress on SDPD sensitivity and that on failure dependence sensitivity are different.

scholarly journals Modeling and Performance Optimization of an Irreversible Two-Stage Combined Thermal Brownian Heat Engine

Entropy ◽  
2021 ◽  
Vol 23 (4) ◽  
pp. 419
Author(s):  
Congzheng Qi ◽  
Zemin Ding ◽  
Lingen Chen ◽  
Yanlin Ge ◽  
Huijun Feng
Keyword(s):  
Power Output ◽  
Performance Optimization ◽  
External Load ◽  
Thermal Contact ◽  
Heat Engine ◽  
Design Parameters ◽  
Load Effect ◽  
Heat Engines ◽  
Heat Leakage ◽  
Steady Current

Based on finite time thermodynamics, an irreversible combined thermal Brownian heat engine model is established in this paper. The model consists of two thermal Brownian heat engines which are operating in tandem with thermal contact with three heat reservoirs. The rates of heat transfer are finite between the heat engine and the reservoir. Considering the heat leakage and the losses caused by kinetic energy change of particles, the formulas of steady current, power output and efficiency are derived. The power output and efficiency of combined heat engine are smaller than that of single heat engine operating between reservoirs with same temperatures. When the potential filed is free from external load, the effects of asymmetry of the potential, barrier height and heat leakage on the performance of the combined heat engine are analyzed. When the potential field is free from external load, the effects of basic design parameters on the performance of the combined heat engine are analyzed. The optimal power and efficiency are obtained by optimizing the barrier heights of two heat engines. The optimal working regions are obtained. There is optimal temperature ratio which maximize the overall power output or efficiency. When the potential filed is subjected to external load, effect of external load is analyzed. The steady current decreases versus external load; the power output and efficiency are monotonically increasing versus external load.

scholarly journals Reliability and Random Lifetime Models of Planetary Gear Systems

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Peng Gao ◽  
Liyang Xie ◽  
Wei Hu
Keyword(s):  
Load Distribution ◽  
Planetary Gear ◽  
Working Process ◽  
Random Load ◽  
Working Mechanism ◽  
Dynamic Reliability ◽  
Reliability Models ◽  
Process Failure ◽  
Failure Dependence ◽  
Gear Systems

Conventional reliability models of planetary gear systems are mainly static. In this paper, dynamic reliability models and random lifetime models of planetary gear systems are developed with dynamic working mechanism considered. The load parameters, the geometric parameters, and the material parameters are taken as the inputs of the reliability models and the random lifetime models. Moreover, failure dependence and dynamic random load redistributions are taken into account in the models. Monte Carlo simulations are carried out to validate the proposed models. The results show that the randomness of the load distribution is obvious in the system working process. Failure dependence has significant influences on system reliability. Moreover, the dispersion of external load has great impacts on the reliability, lifetime distribution, and redundancy of planetary gear systems.

scholarly journals State Estimation with Reduced-Order Observer and Adaptive-LQR Control of Time Varying Linear System

2020 ◽  
Vol 26 (2) ◽  
pp. 24-31
Author(s):  
Omer Aydogdu ◽  
Mehmet Latif Levent
Keyword(s):  
Optimal Control ◽  
Linear System ◽  
State Estimation ◽  
Servo System ◽  
Variable Load ◽  
Time Varying ◽  
Load Effect ◽  
Reduced Order ◽  
Lqr Control ◽  
Reduced Order Observer

In this study, a new controller design was created to increase the control performance of a variable loaded time varying linear system. For this purpose, a state estimation with reduced order observer and adaptive-LQR (Linear–Quadratic Regulator) control structure was offered. Initially, to estimate the states of the system, a reduced-order observer was designed and used with LQR control method that is one of the optimal control techniques in the servo system with initial load. Subsequently, a Lyapunov-based adaptation mechanism was added to the LQR control to provide optimal control for varying loads as a new approach in design. Thus, it was aimed to eliminate the variable load effects and to increase the stability of the system. In order to demonstrate the effectiveness of the proposed method, a variable loaded rotary servo system was modelled as a time-varying linear system and used in simulations in Matlab-Simulink environment. Based on the simulation results and performance measurements, it was observed that the proposed method increases the system performance and stability by minimizing variable load effect.

A Probabilistic Tolerance Allocation Method for Dynamic Mechanical Systems With Periodic Response and Discontinuous Forcing Functions

1995 ◽  
Author(s):  
F. Zhang ◽  
B. J. Gilmore ◽  
A. Sinha
Keyword(s):  
Combustion Engine ◽  
Equations Of Motion ◽  
Mechanical Systems ◽  
Optimization Procedure ◽  
Tolerance Allocation ◽  
Radial Clearance ◽  
Time Varying ◽  
Link Length ◽  
Design Variables ◽  
Forcing Functions

Abstract Tolerance allocation standards do not exist for mechanical systems whose response are time varying and are subjected to discontinuous forcing functions. Previous approaches based on optimization and numerical integration of the dynamic equations of motion encounter difficulty with determining sensitivities around the force discontinuity. The Alternating Frequency/Time approach is applied here to capture the effect of the discontinuity. The effective link length model is used to model the system and to account for the uncertainties in the link length, radial clearance and pin location. Since the effective link length model is applied, the equations of motion for the nominal system can be applied for the entire analysis. Optimization procedure is applied to the problem where the objective is to minimize the manufacturing costs and satisfy the constraints imposed on mechanical errors and design variables. Examples of tolerance allocation are presented for a single cylinder internal combustion engine.

Dynamic Analysis of Mechanical Systems With Time-Varying Topologies: Part 1 — Dynamic Model and Stability Analysis

1990 ◽  
Author(s):  
Yu Wang
Keyword(s):  
Stability Analysis ◽  
Dynamic Model ◽  
Local Stability ◽  
Global Analysis ◽  
Equations Of Motion ◽  
Mechanical Systems ◽  
Time Varying ◽  
Discrete Equations ◽  
Local Stability Analysis ◽  
Multiple Collisions

Abstract A model is developed for analyzing mechanical systems with a pair of bodies with topological changes in their kinematic constraints. It is built upon the concept of Poincaré map rather than following the traditional methods of differential equations. The model provides a set of well-defined and naturally-discrete equations of motion and is capable of giving physical insights of dynamic characteristics of deadbeat convergence of multiple collisions and periodic or chaotic responses. The development of dynamic model and a local stability analysis are presented in Part 1, and the global analysis and numerical simulation are discussed in Part 2.

Lateral Dynamics of Walking-Like Mechanical Systems and Their Chaotic Behavior

2019 ◽  
Vol 29 (09) ◽  
pp. 1930024
Author(s):  
Sergej Čelikovský ◽  
Volodymyr Lynnyk
Keyword(s):  
Stability Region ◽  
Inverted Pendulum ◽  
Chaotic Behavior ◽  
Mechanical Systems ◽  
Small Time ◽  
Time Varying ◽  
External Forcing ◽  
Double Support ◽  
Lateral Dynamics ◽  
Detailed Mathematical Analysis

A detailed mathematical analysis of the two-dimensional hybrid model for the lateral dynamics of walking-like mechanical systems (the so-called hybrid inverted pendulum) is presented in this article. The chaotic behavior, when being externally harmonically perturbed, is demonstrated. Two rather exceptional features are analyzed. Firstly, the unperturbed undamped hybrid inverted pendulum behaves inside a certain stability region periodically and its respective frequencies range from zero (close to the boundary of that stability region) to infinity (close to its double support equilibrium). Secondly, the constant lateral forcing less than a certain threshold does not affect the periodic behavior of the hybrid inverted pendulum and preserves its equilibrium at the origin. The latter is due to the hybrid nature of the equilibrium at the origin, which exists only in the Filippov sense. It is actually a trivial example of the so-called pseudo-equilibrium [Kuznetsov et al., 2003]. Nevertheless, such an observation holds only for constant external forcing and even arbitrary small time-varying external forcing may destabilize the origin. As a matter of fact, one can observe many, possibly even infinitely many, distinct chaotic attractors for a single system when the forcing amplitude does not exceed the mentioned threshold. Moreover, some general properties of the hybrid inverted pendulum are characterized through its topological equivalence to the classical pendulum. Extensive numerical experiments demonstrate the chaotic behavior of the harmonically perturbed hybrid inverted pendulum.

LPV-Based-Method Aiming at a Win-Win Situation for Analytical Control Theories and Intelligent Optimization Methodologies

2009 ◽  
Author(s):  
Kazuhiko Hiramoto
Keyword(s):  
Control Strategy ◽  
Closed Loop ◽  
Control Method ◽  
Control Object ◽  
Gain Scheduling ◽  
Design Parameters ◽  
Analytical Control ◽  
Time Varying ◽  
Intelligent Optimization ◽  
Gain Scheduling Control

A new collaborative control strategy between time varying design parameters in LPV plants and the feedback controllers is proposed in the present paper. As the feedback control law the gain scheduling control scheme is adopted to guarantee the closed-loop L2 gain performance against the variation of the time varying parameter in the control object. The gain-scheduling controller can be obtained in an analytical manner by solving LMIs. For the closed-loop system with the LPV plant and the gain scheduling controller Genetic algorithm (GA), known as a so-called intelligent optimization method, is applied to optimize the closed-loop response. The proposed control system has a complementary structure between the LMI-based analytical control strategy and the flexible intelligent control method that does not impair their advantages each other. In this sense a win-win situation for the LMI-based gain scheduling control and the GA-based intelligent optimization is realized in the proposed approach. A simple simulation example is presented to show the effectiveness of the proposed method.

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