Sami El Ferik

Modeling and Identification of Nonlinear Systems: A Review of the Multimodel Approach—Part 1

The efficacy of the multimodel framework (MMF) in modeling and identification of complex, nonlinear, and uncertain systems has been widely recognized in the literature owing to its simplicity, transparency, and mathematical tractability, allowing the use of well-known modeling analysis and control design techniques. The approach proved to be effective in addressing some of the shortcomings of other modeling techniques such as those based on a single nonlinear autoregressive network with exogenous inputs model or neural networks. A great number of researchers have contributed to this active field. Due to the significant amount of contributions and the lack of a recent survey, the review of recent developments in this field is vital. In this two-part paper, we attempt to provide a comprehensive coverage of the multimodel approach for modeling and identification of complex systems. This paper contains a classification of different methods, the challenges encountered, as well as recent applications of MMF in various fields. In this part 2, the review of multimodel internal structures and parameter estimation as well as validity computation methods is presented. In addition, a multimodel application and future direction are covered. In this literature survey, our main focus is on the MMF where the final system’s representation and behavior is generated through the interpolation of several possible local models. This is of prime importance to control designers. All through this paper, different active research areas and open problems are discussed.

A Behavioral Adaptive Fuzzy controller of multi robots in a cluster space

Display Omitted Novel cluster-space controller for non-holonomic systems based Behavioral Adaptive Fuzzy tuning algorithm (BAFC).Controller is easy to implement and performs tasks based on their importance.Fuzzy tuned controller uses position error and its rate of change as inputs.Implementation using SIMULINK on Lego EV3 WMRs wheeled robot is presented.Wi-Fi link establishes communication between agents and controller. Cooperation between autonomous robot vehicles holds several promising advantages like robustness, adaptability, configurability, and scalability. Coordination between the different robots and the individual relative motion represent both the main challenges especially when dealing with formation control and maintenance. Cluster space control provides a simple concept for controlling multi-agent formation. In the classical approach, formation control is the unique task for the multi-agent system. In this paper, the development and application of a novel Behavioral Adaptive Fuzzy-based Cluster Space Control (BAFC) to non-holonomic robots is presented. By applying a fuzzy priority control approach, BAFC deals with two conflicting tasks: formation maintenance and target following. Using priority rules, the fuzzy approach is used to adapt the controller and therefore the behavior of the system, taking into accounts the errors in the formation states and the target following states. The control approach is easy to implement and has been implemented in this paper using SIMULINK real-time platform. The communication between the different agents and the controller is established through Wi-Fi link. Both simulation and experimental results demonstrate the behavioral response where the robot performs the higher priority tasks first. This new approach shows a great performance with a lower control signal when benchmarked with previously known results in the literature.

Adaptive control of autonomous bicycle kinematics

In this paper, an adaptive Self-Tuning Regulator is proposed to control an autonomous bicycle kinematics. The model used for describing the dynamics of the bicycle is Whipples bicycle model. The roll (lean) and the steer angle of the bicycle the two outputs of the model and the torques across the roll and steer angle as the two control variables. The identification technique used in here is recursive least square identification and the proposed control strategy is state feedback control with the controller gain calculated using linear quadratic regulator. The autonomous bicycle was tested for varying velocities and it was observed that the adaptive controller gives a good control action of the bicycle model not just within the stable velocity region but outside it as well.

Backstepping control of an electro-hydraulic servo system subject to disturbance and parameter uncertainty

This paper addresses the control of a hydraulic servo system rod subject to uncertainty in parameters and to an unknown but bounded disturbance. The proposed backstepping-based robust controller guaranties a uniformly ultimately bounded tracking error leading to practical stability of the closed loop system. Two schemes are proposed. First, a constant gain-based controller that achieves a good tracking accuracy with a steady state error in the millimeter range, but induces control input oscillations in transient. To improve such behavior, a second controller with time varying gain is proposed. Both controllers assure robustness against perturbations and uncertainties in the dynamics of the system. Numerical simulations illustrate the efficacy of the proposed scheme.

AN INVESTIGATION ON THE INCONSISTENCY OF CONSUMER PREFERENCES FOR PRODUCT APPEARANCE: A CASE STUDY OF RESIDENTIAL SOLAR PANELS

The importance of the appearance of consumer products is widely understood. This paper considers an evaluation of the appearance of a technology-oriented product, the residential solar panel, from the perspective of individuals. This study uses a quantitative approach, visual conjoint analysis, to determine preferences for product appearance of solar panels, and further explores how presenting a solar panel in its context of use can influence the consistency of consumer preferences. Approximately 200 survey respondents were shown two kinds of images of solar panels, one of a standalone panel and the other of a panel installed on a roof. Results show a significant shift of preferences when first showing the non-contextualized image and then showing the contextualized image. Such preference inconsistency provides insights with which to inform the process of user-needs revealing.Copyright

MPC-based controller for augmented boiler-NO x model

This paper addresses the problem of controlling a drum type boiler operation as well as its NOx emission level. For that purpose an augmented model integrating both boiler and NOx models has been developed. The system has multiple roots at the origin causing poor phase and gain stability margins. In addition, one of its inputs has been considered as an undesirable disturbance. Different control strategies have been studied and benchmarked. A two-stage Augmented Model Predictive control (MPC) controller with constraints demonstrated best performance. Computer simulations show the performance of such approach.

Backstepping-based output feedback control of an electro-hydraulic servo system

This paper addresses the control of a hydraulic servo system rod subject to uncertainty in parameters and to an unknown but bounded disturbance. The proposed backstepping-based robust controller guaranties a uniformly ultimately bounded tracking error leading to practical stability of the closed loop system. State-Observer is also designed using backstepping approach to estimate the states. The controller assures robustness against perturbations and uncertainties in the dynamics of the system. Numerical simulations illustrate the efficacy of the proposed scheme.

An Investigation of Design Requirement Volatility, Risk and Priority in Early Stage Design Projects

In new product development, design requirements are a formalization of a product vision and can evolve substantially in the early stages of product design. This paper describes an empirical study of the relationships among design requirements volatility, risk, prioritization and the quality of design outcome in the context of a graduate level product development course for mid-career professionals. Among other findings, a pattern of decreasing risk of a design requirement, especially the risk of high priority requirements, was found to be a key predictor of success. The findings suggest the importance of managing design requirement risk in early stage design and the potential benefit of using risk and priority level of design requirements to monitor design project health.Copyright

LQG-based control of unmanned helicopter using OKID-based identification approach

This paper presents the system identification and control of an unmanned helicopter(UH) with ducted fan. The plant is an unstable multi-input-multi-output (MIMO) system. First, four identification methods have been considered in this work. Two of these methods studied the identification of the system as a set of transfer functions relating different inputs and outputs, namely the least square method with QR-factorization (LS-QR) and the recursive least square method (RLS). The other two methods are state-space identification method. Indeed, the classical subspace identification method and the observer-Kalman filter identification (OKID) method have been used to identify the system in state space representation. Analytical formulations of these methods as well as comparison of their performances based on their degree of fitness are presented for the special case of UH system. The results show that OKID out-performs the other methods. Based on this result, an OKID-LQGI-based controller for velocities tracking controller is proposed. The simulation results show excellent tracking performance.

Robust adaptive path-following control of underactuated marine vessel with off-track error constraint

ABSTRACT In this paper, a new robust adaptive controller is investigated to force an underactuated surface marine vessel to follow a predefined parameterised path at a desired speed, despite actuator saturation and the presence of model uncertainties as well as environmental disturbances induced by waves, wind and sea-currents. To ensure robustness of the path-following controller, time-varying constraint on the off-track error (i.e. the maximal distance from the ship to the reference path) is considered. To address the off-track error constraint the tan-barrier Lyapunov function is incorporated with the control scheme, where the idea of auxiliary design system introduced in Chen, Sam, and Ren (2011) is adopted and its states are used in combination with backstepping and Lyapunov synthesis to adaptive tracking control design with guaranteed stability. Furthermore, the command filters are adopted to implement physical constraints on the virtual control laws so that analytic differentiation of the virtual control laws is avoided. We show that the proposed robust adaptive control law is able to guarantee semi-global uniform ultimate bounded stability of the closed-loop system. Numerical simulations and experimental results are carried out to demonstrate the effectiveness of the proposed algorithm.