Showing papers by "Hamid Reza Karimi published in 2016"

A Robust Observer-Based Sensor Fault-Tolerant Control for PMSM in Electric Vehicles

Abstract: This paper investigates the problem of automatic speed tracking control of an electric vehicle (EV) that is powered by a permanent-magnet synchronous motor (PMSM). A reconfiguration scheme, based on higher order sliding mode (HOSM) observer, is proposed in the event of sensor faults/failures to maintain a good control performance. The corresponding controlled motor output torque drives EVs to track the desired vehicle reference speed for providing uninterrupted vehicle safe operation. The effectiveness of the overall sensor fault-tolerant speed tracking control is highlighted when an EV is subjected to disturbances like aerodynamic load force and road roughness using high-fidelity software package CarSim. Experiments with a 26-W, three-phase PMSM are presented to demonstrate the validity of the proposed fault-detection scheme.

Tracking Control of Networked Multi-Agent Systems Under New Characterizations of Impulses and Its Applications in Robotic Systems

Abstract: This paper examines the problem of tracking control of networked multi-agent systems with multiple delays and impulsive effects, whose results are applied to mechanical robotic systems. Four kinds of impulsive effects are taken into account: 1) both the strengths of impulsive effects and the number of nodes injected with impulses are time dependent; 2) the strengths of impulsive effects occur according to certain probabilities and the number of nodes under impulsive control is time varying; 3) the strengths of impulses are time varying, whereas the number of nodes with impulses takes place according to certain probabilities; 4) both the strengths of impulses and the number of nodes with impulsive control occur according to certain probabilities. By utilizing the comparison principle, criteria are established for these different cases and a relationship between the frequencies (occurrence probabilities) of impulses and systems' parameters is unveiled. Finally, an example for tracking control of robotic systems is provided to show the effectiveness of the presented results.

A review of diagnostics and prognostics of low-speed machinery towards wind turbine farm-level health management

Abstract: Large wind farms are gaining prominence due to increasing dependence on renewable energy. In order to operate these wind farms reliably and efficiently, advanced maintenance strategies such as condition based maintenance are necessary. However, wind turbines pose unique challenges in terms of irregular load patterns, intermittent operation and harsh weather conditions, which have deterring effects on life of rotating machinery. This paper reviews the state-of-the-art in the area of diagnostics and prognostics pertaining to two critical failure prone components of wind turbines, namely, low-speed bearings and planetary gearboxes. The survey evaluates those methods that are applicable to wind turbine farm-level health management and compares these methods on criteria such as reliability, accuracy and implementation aspects. It concludes with a brief discussion of the challenges and future trends in health assessment for wind farms.

Adaptive Neural Control of MIMO Nonstrict-Feedback Nonlinear Systems With Time Delay

Abstract: In this paper, an adaptive neural output-feedback tracking controller is designed for a class of multiple-input and multiple-output nonstrict-feedback nonlinear systems with time delay. The system coefficient and uncertain functions of our considered systems are both unknown. By employing neural networks to approximate the unknown function entries, and constructing a new input-driven filter, a backstepping design method of tracking controller is developed for the systems under consideration. The proposed controller can guarantee that all the signals in the closed-loop systems are ultimately bounded, and the time-varying target signal can be tracked within a small error as well. The main contributions of this paper lie in that the systems under consideration are more general, and an effective design procedure of output-feedback controller is developed for the considered systems, which is more applicable in practice. Simulation results demonstrate the efficiency of the proposed algorithm.

A Robust Predictive Control Design for Nonlinear Active Suspension Systems

Abstract: This paper proposes a novel method for designing robust nonlinear multivariable predictive control for nonlinear active suspension systems via the Takagi-Sugeno fuzzy approach. The controller design is converted to a convex optimization problem with linear matrix inequality constraints. The stability of the control system is achieved by the use of terminal constraints, in particular the Constrained Receding-Horizon Predictive Control algorithm to maintain a robust performance of vehicle systems. A quarter-car model with active suspension system is considered in this paper and a numerical example is employed to illustrate the effectiveness of the proposed approach. The obtained results are compared with those achieved with model predictive control in terms of robustness and stability.

Special Issue on Recent Developments on Modeling and Control of Hybrid Electric Vehicles

Abstract: Environmental pollution and energy shortages are not only the two major problems currently in the sustainable development of the automotive industry, but also the two major bottlenecks in the global automotive industry. Facing the enormous requirement of energy-saving and environment protection, the development of new energy vehicles have become an important measure to solve this problem. Recently, hybrid electric vehicles (HEVs) or electric vehicles (EVs) have become a hot topic from both theoretical and practical perspectives. Among various types of electric vehicles, hybrid electric vehicles (HEVs) — or as they are commonly dubbed “hybrid vehicles” — offer the distinct advantages of energy diversification, versatile operation, long driving range and high sustainability. Particularly, the aim is to employ advanced control strategies to improve the vehicle performance, including fuel economy and dynamic property, for instance.

Finite-time stability and stabilisation for a class of nonlinear systems with time-varying delay

Abstract: This paper is concerned with the problems of finite-time stability FTS and finite-time stabilisation for a class of nonlinear systems with time-varying delay, which can be represented by Takagi–Sugeno fuzzy system Some new delay-dependent FTS conditions are provided and applied to the design problem of finite-time fuzzy controllers First, based on an integral inequality and a fuzzy Lyapunov–Krasovskii functional, a delay-dependent FTS criterion is proposed for open-loop fuzzy system by introducing some free fuzzy weighting matrices, which are less conservative than other existing ones Then, the parallel distributed compensation controller is designed to ensure FTS of the time-delay fuzzy system Finally, an example is given to illustrate the effectiveness of the proposed design approach

Robust Composite Nonlinear Feedback Path-Following Control for Independently Actuated Autonomous Vehicles With Differential Steering

Abstract: This paper investigates utilizing the front-wheel differential drive-assisted steering (DDAS) to achieve the path-following control for independently actuated (IA) electric autonomous ground vehicles (AGVs), in the case of the complete failure of the active front-wheel steering system. DDAS, which is generated by the differential torque between the left and right wheels of IA electric vehicles, can be utilized to actuate the front wheels as the sole steering power when the regular steering system fails, and thus avoids dangerous consequences for AGVs. As an inherent emergency measure and an active safety control method for the steering system of electric vehicles, DDAS strategy is a valuable fault-tolerant control approach against active steering system failure. To improve the transient performance of the fault-tolerant control with the DDAS, a novel multiple-disturbance observer-based composite nonlinear feedback (CNF) approach is proposed to realize the path-following control for IA AGVs considering the tire force saturations. The disturbance observer is designed to estimate the external multiple disturbances with unknown bounds. CarSim–Simulink joint simulation results indicate that the proposed controller can effectively achieve the fault-tolerant control and improve the transient performance for path following in the faulted-steering situation.

Equivalent-input-disturbance-based repetitive tracking control for Takagi–Sugeno fuzzy systems with saturating actuator

Abstract: This study investigates the output tracking problem for a class of Takagi–Sugeno fuzzy systems subject to periodic signals and actuator saturation via equivalent-input-disturbance (EID) technique. In particular, to ensure the periodic signals tracking, a state-space repetitive control structure is considered. Further, the EID technique is utilised to improve the disturbance rejection performance without any prior knowledge of the disturbance and inverse dynamics of the plant. By constructing a suitable Lyapunov–Krasovskii functional and using the Wirtinger-based integral inequality, a new set of sufficient conditions is derived in terms of linear matrix inequalities (LMIs) which ensures the stability of the addressed system. In addition to that by using a Lyapunov level set, saturation-dependent Lyapunov function captures the real-time information on the severity of actuator saturation and leads to less conservative estimate of the domain of attraction, which is based on the solution of an LMI optimisation problem. Moreover, the designed fuzzy repetitive controller is reliable in the sense that the stability and the satisfactory performance of the closed-loop system are achieved not only under normal operation, but also in the presence of any actuator faults, saturation and dead zone. Finally, the proposed method is validated through two numerical examples to illustrate the effectiveness and superiority of the developed controller design.

Novel Results on Generalized Dissipativity of Two-Dimensional Digital Filters

Abstract: Existing results on the generalized dissipativity of digital filters are limited to 1-D cases. This brief presents some novel results on the generalized dissipativity of 2-D filters in the discrete Fornasini–Marchesini second (FMS) form. More specifically, we propose a criterion to ascertain that single 2-D filters in the discrete FMS form are 2-D generalized dissipative. Using this result, a condition is established such that the interconnected 2-D filters in the discrete FMS form are 2-D generalized dissipative. Furthermore, the asymptotic stability of unforced interconnected 2-D filters is examined. It is shown that the results developed in our recent work for 1-D filters and in this brief for 2-D filters serve as an overall framework for the generalized dissipativity of digital filters.

Dissipativity-Based Small-Gain Theorems for Stochastic Network Systems

Abstract: In this paper, some small-gain theorems are proposed for stochastic network systems which describe large-scale systems with interconnections, uncertainties and random disturbances. By the aid of conditional dissipativity and showing times of stochastic interval, small-gain conditions proposed for the deterministic case are extended to the stochastic case. When some design parameters are tunable in practice, we invaginate a simpler method to verify small-gain condition by selecting one subsystem as a monitor. Compared with the existing results, the existence-and-uniqueness of solution and ultimate uniform boundedness of input are removed from requirements of input-to-state stability and small-gain theorems.

New delay-dependent stability of Markovian jump neutral stochastic systems with general unknown transition rates

Abstract: This paper investigates the delay-dependent stability problem for neutral Markovian jump systems with generally unknown transition rates GUTRs. In this neutral GUTR model, each transition rate is completely unknown or only its estimate value is known. Based on the study of expectations of the stochastic cross-terms containing the integral, a new stability criterion is derived in terms of linear matrix inequalities. In the mathematical derivation process, bounding stochastic cross-terms, model transformation and free-weighting matrix are not employed for less conservatism. Finally, an example is provided to demonstrate the effectiveness of the proposed results.

Observer-Based H ∞ Sliding Mode Controller Design for Uncertain Stochastic Singular Time-Delay Systems

Abstract: The paper is concerned with the observer-based $$H_\infty $$H? sliding mode controller design for a class of uncertain stochastic singular time-delay systems subjected to input nonlinearity. Using the sliding mode control, a robust law is established to guarantee the reachability of the sliding surface in a finite time interval, and the sufficient condition for asymptotic stability of the error system and sliding mode dynamics with disturbance attenuation level is presented in terms of linear matrix inequalities. Finally, an example illustrates the proposed method.

Towards farm-level health management of offshore wind farms for maintenance improvements

Abstract: This paper studies a conceptual architecture for health management of offshore wind farms. To this aim, various necessary enablers of a health management sys- tem are presented to improve reliability and availability while optimizing maintenance costs. The main focus lies on improving existing condition monitoring systems based on concepts of condition-based maintenance and relia- bility centered maintenance. A brief review of the rel- evant state-of-the-art is presented and gaps to be filled towards realization of such health management system are discussed.

Dissipative based adaptive reliable sampled-data control of time-varying delay systems

Abstract: This paper is concerned with the problem of dissipative based adaptive reliable controller for a class of time delay systems subject to actuator failures and time-varying sampling with a known upper bound on the sampling intervals. By constructing a proper Lyapunov-Krasovskii functional which fully uses the available information about the actual sampling pattern and time delays, a new set of sufficient conditions is derived to obtain the required result. Then, a dissipative based adaptive sampled-data controller is designed such that the resulting closed-loop system is reliable in the sense that it is asymptotically stable and has the prescribed dissipative performance under given constraints. The existence condition of the desired dissipative based adaptive reliable sampled-data controller is obtained in terms of linear matrix inequalities. Further, the performance of the proposed controller is implemented on a liquid propellant rocket motor with a pressure feeding system model. The simulation results show the effectiveness and better performance of the proposed adaptive reliable sampled-data controller over conventional reliable controller.

New results on stability analysis and stabilization of time-delay continuous Markovian jump systems with partially known rates matrix

Abstract: Summary In this note, the problems of stability analysis and controller synthesis of Markovian jump systems with time-varying delay and partially known transition rates are investigated via an input–output approach. First, the system under consideration is transformed into an interconnected system, and new results on stochastic scaled small-gain condition for stochastic interconnected systems are established, which are crucial for the problems considered in this paper. Based on the system transformation and the stochastic scaled small-gain theorem, stochastic stability of the original system is examined via the stochastic version of the bounded realness of the transformed forward system. The merit of the proposed approach lies in its reduced conservatism, which is made possible by a precise approximation of the time-varying delay and the new result on the stochastic scaled small-gain theorem. The proposed stability condition is demonstrated to be much less conservative than most existing results. Moreover, the problem of stabilization is further solved with an admissible controller designed via convex optimizations, whose effectiveness is also illustrated via numerical examples. Copyright © 2015 John Wiley & Sons, Ltd.

Small Wind Turbines: Specification, Design, and Economic Evaluation

Abstract: In this work, we consider various aspects of small wind turbines' (SWTs) design and operation. First, an extensive literature study is presented by considering SWTs specification, market statistics, the smart grid, and the prosumer concepts as well as the most important parameters affecting the efficiency of wind turbines. Then, both the literature review and series of coupled numerical simulations investigating impact of the chosen design solutions on small wind turbine operation are performed. It allowed objective evaluation of different design approaches, which in turn enabled the systematic identification of actual limitations as well as the opportunities for specific design solutions of SWTs: horizontal axis wind turbines (HAWTs) and vertical axis wind turbines (VAWTs); the rotor position in relation to the tower (upwind vs. downwind); and diffusor-augmented wind turbine (DAWT). Additionally, an economic evaluation is carried with the use of an advanced numerical Weather Research & Forecasting (WRF) model. It is shown that auxiliary power generation using privately owned SWTs can be an economically viable option. Finally, a set of design goals for future SWTs is formulated based on the performed numerical analyses.

Vibration control strategy for large-scale structures with incomplete multi-actuator system and neighbouring state information

Abstract: The synthesis of optimal controllers for vibrational protection of large-scale structures with multiple actuation devices and partial state information is a challenging problem. In this study, the authors present a design strategy that allows computing this kind of controllers by using standard linear matrix inequality optimisation tools. To illustrate the main elements of the new approach, a five-story structure equipped with two interstory actuation devices and subjected to a seismic disturbance is considered. For this control setup, three different controllers are designed: an ideal state-feedback H 8 controller with full access to the complete state information and two static output-feedback H 8 controllers with restricted neighbouring state information. To assess the performance of the proposed controllers, the corresponding frequency responses are investigated and a proper set of numerical simulations are conducted, using the full scale North-South El Centro 1940 seismic record as ground acceleration input. The obtained results indicate that, despite the severe information constraints, the proposed static output-feedback controllers attain a level of seismic protection that is very similar to that achieved by the ideal state-feedback controller with complete state information.

Morphological characterization of intra-and interspecific diversity in some Iranian wild Allium species

Abstract: Alliums, a botanically diverse genus of the Alliaceae family, is an important horticulture crop with unknown potential for economically purposes such as spices, vegetables, medicinal or ornamental usage. This genus is morphologically very variable and therefore, there is controversy between species of the some subgenus and their sections. In order to represent the efficiency of morphological descriptors on intra-and interspecific diversity of Allium genus, 41 accessions of Allium from 13 species were evaluated with the use of 23 qualitative characteristics on inflorescence, scape and leaf; along with 6 quantitative morphological descriptors of seeds. Nineteen qualitative characteristics could clearly define taxonomic delimitation, even in sect. Acanthoprason, as one of the most confusing groups. Moreover, basal position of Allium species, subgenus, sections and species arrangement was confirmed by the constructed UPGMA dendrogram generated with these traits. These qualitative morphological descriptors can successfully applied for evaluating intraspecific morphodiversity that can be beneficial for horticultural usage such as ornamentals. However, six quantitative characteristics recorded on seeds could not discriminate the taxonomic arrangements. The results of this research might be important in gene bank management and agricultural and breeding programs to develop new Allium varieties in the future.

Effects of Artificial Pollination Using Pollen Suspension Spray on Nut and Kernel Quality of Pistachio Cultivar Owhadi

Abstract: Yield and nut quality in pistachio are highly dependent on cultural practices especially pollination. This study was conducted to investigate the effects of pollen suspension spray containing 0.01% and 0.02% boric acid combined with 1% (w/v) pollen on nut and kernel quality of pistachio (Pistacia vera L. cv. Owhadi). The experiment was carried out as RCBD with three replications over 2011–12 period. The results showed that application of medium containing agar (A) and 0.01% boric acid (B1) combined with 1% (w/v) pollen decreased fruit set in both years compared to control whereas nut splitting was increased during 2012. Pollen suspension sprays unaffected nut and kernel dimensions in both years but increased kernel proteins and decreased oil during 2011. According to this study, it could be postulated that artificial pollination in pistachio using pollen suspension spray is possible.

On integral input-to-state stability for a feedback interconnection of parameterised discrete-time systems

Abstract: This paper addresses integral input-to-state stability iISS for a feedback interconnection of parameterised discrete-time systems involving two subsystems. Particularly, we give a construction for a smooth iISS Lyapunov function for the whole system from the sum of nonlinearly weighted Lyapunov functions of individual subsystems. Motivations for such a construction are given. We consider two main cases. The first one investigates iISS for the whole system when both subsystems are iISS. The second one gives iISS for the interconnected system when one of subsystems is allowed to be input-to-state stable. The approach is also valid for both discrete-time cascades and a feedback interconnection of iISS and static systems. Examples are given to illustrate the effectiveness of the results.

A Mathematical Model for Vehicle-Occupant Frontal Crash Using Genetic Algorithm

Abstract: In this paper, a mathematical model for vehicle-occupant frontal crash is developed. The developed model is represented as a double-spring-mass-damper system, whereby the front mass and the rear mass represent the vehicle chassis and the occupant, respectively. The springs and dampers in the model are nonlinear piecewise functions of displacements and velocities respectively. More specifically, a genetic algorithm (GA) approach is proposed for estimating the parameters of vehicle front structure and restraint system. Finally, it is shown that the obtained model can accurately reproduce the real crash test data taken from the National Highway Traffic Safety Administration (NHTSA). The maximum dynamic crash of the vehicle model is 0.05% less than that in the real crash test. The displacement of the occupant is 0.09% larger than that from the crash test. Improvement of the model accuracy is also observed from the time at maximum displacement and the rebound velocities for both the vehicle and occupant.