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This work addresses the lateral stabilisation problem of four-wheels ground vehicles. The objective is to estimate the largest state-space region such that the closed-loop vehicle lateral stability...

In this paper, an adaptive nonlinear control design for quadrotors is presented using nonlinear dynamic inversion and model-following neuro-adaptive techniques. The baseline controller is designed using dynamic inversion approach that exploits the time scale separation principle. The design works well if the model is perfectly known. However, the quadrotor system can have uncertainty in parameters. To tackle this, a neuro-adaptive controller is augmented with the baseline controller. The approach uses a single layer neural network to learn unknown dynamics and an adaptive law is employed to ensure that the quadrotor behave in the desired manner. A Lyapunov approach is used to show that the approximated dynamics remains bounded.

In this paper, we propose a control Lyapunov function based on a nonlinear controller for a turbocharged diesel engine. A model-based approach is used which predicts the experimentally observed engine performance for a biodiesel. The basic idea is to develop an inverse optimal control and to employ a Lyapunov function in order to achieve good performances. The obtained controller gain guarantees the global convergence of the system and regulates the flows for the variable geometry turbocharger as well as exhaust gas recirculation systems in order to minimize the NOx emission and the smoke of a biodiesel engine. Simulation of the control performances based on professional software and experimental results show the effectiveness of this approach.

Gain scheduling (GS) is one of the most popular approaches to nonlinear control design and it is known that GS controllers have a better performance than robust ones. Following the terminology of control engineering, linear parameter-varying (LPV) systems are time-varying plants whose state space matrices are fixed functions of some vector of varying parameters. Our approach is based on considering that the LPV system, scheduling parameters and their derivatives with respect to time lie in a priori given hyper rectangles. To guarantee the performance we use the notion of guaranteed costs. The class of control structure includes centralized, decentralized fixed order output feedbacks like PID controller. Numerical examples illustrate the effectiveness of the proposed approach.

This paper proposed a novel nonlinear control approach to improve vehicle yaw stability and trajectory tracking ability after a tire blow-out. By using the triple-step nonlinear method, the controller design procedure is presented for a class of non-affine systems where the control inputs take their actions through a nonlinear and implicit way. Simulation results are obtained in a commercial software veDYNA. The simulation results show the efficiency of the proposed approach.

A new approach to designing a robust nonlinear controller for longitudinal flexible body models of canard configured air-breathing hypersonic flight vehicles with significant couplings and interactions is presented. The methodology uses a robust feedback linearization method to feedback linearize the nonlinear air-breathing hypersonic flight vehicle model with 24 uncertainty parameters. Using this approach, a linearized uncertainty model of the air-breathing hypersonic flight vehicle is obtained in the first step by considering an upper bound on each uncertain parameter. In the second step, a minimax linear quadratic regulator-based velocity and altitude robust tracking controller is synthesized for the linearized model. Simulation studies are conducted using the original nonlinear model of the air-breathing hypersonic flight vehicle with a large flight envelope and time-varying uncertainties. Simulation results show that the feedback linearization-based minimax linear quadratic regulator controller effectively achieves the tracking requirement and robustly stabilizes the air-breathing hypersonic flight vehicle.

In this paper we consider design of control laws for a marine cooling system with flow dependent delays by use of principles from feedback linearization. To deal with model uncertainties and delay mismatches, a robust linear H ∞ controller is designed for the feedback linearized system. In this context, we apply a bilinear transformation to obtain a well-posed H ∞ problem. Robustness of performance for the resulting robust nonlinear control design is evaluated through a simulation example where a comparison is made to a linear control design.

This paper presents a nonlinear control design approach for active suspensions based on the backstepping method with a special class of control Lyaponov functions. This approach is shown to yield a good performance and to allow an easy tuning of the trade-off between safety and comfort, a strong asset in order to simplify the experimental tuning work required in the vehicle development process. The paper presents the methods and conditions for the simplified tuning to be possible. Different road profiles are used to test the method, and the results are presented at the end of the paper, confirming the validity of the approach.

The conflict between ride comfort and safety is well-known for vehicle suspension systems. This work presents a control design concept which tries to ease this conflict for a fully active nonlinear suspension system using velocity-based linearisations. Within the corresponding velocity-based design framework, any nonlinear system can be approximated by a family of local linear subsystems which facilitates classical linear control design and analysis methods. In case of the active suspension system, first two robust linear controllers for good comfort and safety, respectively, are determined by numerical optimization. Then the velocity-based design framework is used to identify an adequate, locally stable way of continuously interpolating between those two controllers with scheduling variables. By that, a nonlinear controller is gained which is aimed at high performance and which avoids unnecessary restrictive slow-variation requirements on the scheduling variables. Finally the nonlinear controller is tested and evaluated in simulations with a realistic quarter-car model of a quad vehicle.

This paper deals with a first application of the new framework of model-free control to the promising technology of shape memory alloys actuators. In particular antagonistic shape memory alloys actuator. These devices are known to be difficult to model in a control perspective. Simulations results are exposed and some preliminary experimental results illustrates the paper.

In this paper, a design method of nonlinear controllers is proposed. While physical or chemical analysis is a reliable approach for the construction of nonlinear models, it needs many experiences and might result in very complicated models. The Black-box model approach is adopted in this paper. Identification and controller design of nonlinear processes are very troublesome and complicated. Therefore, a direct design method of nonlinear control, which means not to identify process models, is proposed. The controller is designed using the idea of VRFT (virtual reference feedback tuning). In order to deal with the nonlinearity, input–output data in various operating conditions must be obtained. However, it is very difficult to get sufficient quantities of data for identification of the nonlinearity. Therefore, the model reliability should be evaluated. If the operating condition was not included in the learning data for the nonlinear model identification, the reliability of the model should be judged low. In such a case, it is proposed to suppress the magnitude of the manipulation change. Moreover, in such a case, the online data are stored and are used to re-design the nonlinear model offline. The effectiveness of the proposed controller was shown in a simulation of a tank system.

The problem of path following for marine surface vessels using rudder angle is addressed in this paper. A 4 degrees of freedom nonlinear surface vessel model, together with the Serret-Frenet equations, is introduced to describe the ship dynamics and path following error dynamics. While similar models have been used and reported in literature for path following control algorithm development, the novelty of the approach presented in this work lies in the following aspects: (a) The back-stepping nonlinear controller design is based on feedback dominance, instead of feedback linearization and nonlinearity cancellation; (b) Relying on feedback dominance, the resulting controller is almost linear, with very benign nonlinearities allowing for analysis and evaluation; (c) Performance of the nonlinear controller, in terms of path following, is analyzed for robustness in the presence of rudder saturation and rate limits, delays in the control execution, as well as measurement noises. Because of its simple form, very limited on-board computational power is required to implement the control. The simulation results are presented to verify and illustrate the analytic development and the effectiveness of the resulting control.

This paper introduces the virtual reference feedback tuning (VRFT) approach for controller tuning in a nonlinear setup. VRFT is a data-based method that permits to directly select the controller based on data, with no need for a model of the plant. It is based on a global model reference optimization procedure and, therefore, does not require to access the plant for experiments many times so as to estimate the control cost gradient. For this reason, it represents a very appealing controller design methodology for many control applications.

We consider the problem of orbital transfer under propulsion constraints. The solution is arrived at by appealing to several recent nonlinear control design methods including backstepping, forwarding, and a modified form of Jurdjevic-Quinn control.

In this paper we propose a scheme for output tracking of nonminimum phase flat systems. The technique, which is applicable even in the minimum phase case, uses an inverse trajectory for feedforward which is stabilized by a state tracker built using the flat output. In contrast to approximate-linearization based control [Hauser, J., S. Sastry and G. Meyer (1992). Nonlinear control design for slightly nonminimum phase systems: application to v/stol aircraft. Automatica, 28, 665–679], which yields good performance in slightly nonminimum phase systems, our approach applies equally well to slightly and strongly nonminimum phase systems. The proposed control scheme and the approximate-linearization based controller are applied to a Vertical Take Off and Landing (VTOL) aircraft example and the performances are compared.

International audience; This paper first emphasizes how the well-known backstepping procedure for constructive nonlinear control design can be adapted to further guarantee some {\em constraints} on the output evolution. This approach is then illustrated with the problem of angle or voltage control in a simple Single-Machine-Infinite-Bus model of an electrical network. Various simulations are finally provided accordingly.

This paper presents a control design for the tip position trajectory tracking of a two-link manipulator arm with a flexible forearm. The control design is based on two steps. First, input-output linearization is applied to decouple the shoulder arm dynamics from the forearm dynamics, which transforms the trajectory tracking control of the nonlinear non-minimum phase system into the trajectory tracking control of two linear subsystems. Then trajectory tracking control design of each subsystem is carried out in the second design step. Stability and performance properties of the control design are presented together with simulation results. This study demonstrates a control design method for trajectory tracking control of a nonlinear non-minimum phase system.

In recent years, Sum–Of–Squares (SOS) method has attracted increasing interest as a new approach for stability analysis and controller design of nonlinear dynamic systems. This paper utilizes SOS method to design a robust nonlinear controller for longitudinal dynamics of a hypersonic aircraft model. Specifically, the searching of the nonlinear robust controller is reformulated as a robust SOS/robust LMI problem, and then solved via a stochastic iterative algorithm. As the simulation results show, the designed controller is capable of stabilizing the aircraft and following pilot commands in presence of parametric uncertainties in the aircraft model.Copyright © 2010 by ASME

VSC-HVDC transmission systems may overcome some unexpected stochastic time variant (STV) parameters uncertainties such as frequency disadjustments and cable parameters uncertainties inherent with AC grids. This paper first presents a mathematical modeling of VSC-HVDC transmission systems. These systems exhibit a nonlinear character, and therefore, two different methodologies for robust nonlinear controllers design based on Asymptotic Output Tracking (AOT) and the Sliding Mode Control (SMC) techniques are investigated to control theVSC-HVDC transmission systems submitted to network nonlinearities introduced by requirements to power flow and line voltage. Robust stabilizing feedback control laws are formulated to govern the DC link voltage and to control the active and reactive powers under STV parameters uncertainties. Both kinds of robust nonlinear controllers are demonstrated and compared through simulation studies on the VSC-HVDC transmission systems using MATLAB©-Simulink software. Dealing with systems of high power ratings up to 300 MW, based on this comparison, the simulation results significantly clarify the controllers robustness and the control flexibility towards improving the system's dynamic behaviour and enhancing the system's stability under STV parameters uncertainties. Regarding the economical feasibility and the relative structural simplicity, the superiority of the controller based AOT over that of the SMC controller is pointed out.

It has been well documented in the engineering education literature that introductory linear control systems courses present unique pedagogical challenges. Similarly, it has been reported that engaging undergraduate students in control systems research is challenging. The control of nonlinear systems is the focus of much research; Therefore, a paradox exists; research programs involving undergraduate students are often conducted in a “nonlinear before linear” fashion. Prior research by the authors approached this paradox by investigating whether a meaningful research project in nonlinear control systems could be conducted. While the author and co-author were willing to execute this research (despite the intense time commitment), this type of project is not sustainable long-term unless the significant time invested results in Item 1) illumination of new pedagogical techniques that generalize to each student in the linear control systems course (not just participants in the research project). This manuscript will describe in detail Item 1) . Given the student and faculty mentors experience in the nonlinear controls research project and the student’s experience in the linear control systems course, pedagogical insights gained through this endeavor will be detailed by the faculty member. These are meant to close the loop of instructor assessment of the course during preparation for future offerings. Therefore, the undergraduate student directly provides an accounting of the experiences throughout the research program and introductory control systems course. The result is a proposed pedagogical approach to be implemented by three distinct methodologies. Methodology (1) Traditional lecture format, Methodology (2) Targeted physical or hands-on experiences where students are exposed to a controlled system/process commonly seen in industry, and Methodology (3) Direct student participation in the design of certain aspects of course materials.Copyright © 2009 by ASME

Benchmarks and Design and Analysis Challenges.- The AIRBUS On-Ground Transport Aircraft Benchmark.- On-Ground Transport Aircraft Nonlinear Control Design and Analysis Challenges.- The ADMIRE Benchmark Aircraft Model.- Nonlinear Flight Control Design and Analysis Challenge.- Applications to the Airbus Benchmark.- Nonlinear Symbolic LFT Tools for Modelling, Analysis and Design.- Nonlinear LFT Modelling for On-Ground Transport Aircraft.- On-Ground Aircraft Control Design Using an LPV Anti-windup Approach.- Rapid Prototyping Using Inversion-Based Control and Object-Oriented Modelling.- Robustness Analysis Versus Mixed LTI/LTV Uncertainties for On-Ground Aircraft.- Applications to the ADMIRE Benchmark.- An LPV Control Law Design and Evaluation for the ADMIRE Model.- Block Backstepping for Nonlinear Flight Control Law Design.- Optimisation-Based Flight Control Law Clearance.- Investigation of the ADMIRE Manoeuvring Capabilities Using Qualitative Methods.- Industrial Evaluation and Concluding Remarks.- Industrial Evaluation.- Concluding Remarks.

This paper deals with the application of a Multivariable Nonlinear Controller (MNC) to a multivariable nonlinear boiler-turbine unit. The method can asymptotically estimate and compensate the nonlinearity, coupling and disturbances owing to its observation ability. A decentralized MNC system is obtained for a nonlinear boiler-turbine model, and then evaluated under a wide range of operating conditions and perturbations. Simulation results show that the MNC can achieve decoupling, asymptotic tracking property without steady-state errors, disturbance rejection and better robust performance for boiler-turbine plants, compared with GA/LQR and standard optimal controller LQR.

In this paper, we propose to regulate the output of an auto-catalytic bioprocess (a biological process associated with a growth of a micro-organism) by means of a recirculation loop and by-pass. We give conditions on the volume of the reactor and the kinetic function for which it is possible to stabilize the output concentration under a constant or disturbed unmeasured input flow. Furthermore, we obtain convergence of the output variable in finite time with a Lipschitz continuous feedback.

[Departement_IRSTEA]EA [TR1_IRSTEA]TESAD / MOST; Control design of mobile robots dedicated to path tracking tasks is generally based on the rolling without sliding assumption at the wheel/ground contact point. However, such an hypothesis is not relevant for off-road vehicle and the use of non sliding assumption in this case leads to important tracking errors. Moreover, the vehicles considered for offroad applications (such as agricultural tasks) have generally important mass and inertia and are equipped with low reactive actuators. As a result, delays are introduced into the control loop, which depreciate considerably the performances of autonomous path tracking, especially during a modification of path curvature. This paper proposes several developments, relying on adaptive and predictive observer-based control, dedicated to automatic guidance of off-road mobile robots. The relevancy of the proposed algorithm is investigated via full scale experiments, carried out with a farm tractor, as the considered application is agricultural work.

[Departement_IRSTEA]EA [TR1_IRSTEA]TESAD / MOST; Automatic devices dedicated to vehicle guidance in off-road conditions are necessarily confronted with sliding phenomenon, since it may considerable damage the accuracy of the following task. Control laws taking explicitly into account such a phenomenon have already been designed in previous work. They can actually improve the guidance accuracy. However, their efficiency is highly dependent on the sliding parameters estimation (since these parameters cannot be provided by a direct measurement). In this paper, an observer-like estimator is designed, providing sideslip angles from a single exteroceptive sensor, namely a Real Time Kinematic GPS (RTK-GPS). Improvements in guidance accuracy, with respect to previous estimation approaches, is demonstrated through full scale experiments, addressing agricultural applications.

This contribution presents a mathematical model for cold rolling mills suited for the control purpose. Founded on physical considerations, particular emphasis is laid on the modelling of the roll gap, including a detailed description of the elastic work roll deformations. Typically, non-circular arc roll gap models involve significant computational effort. Thus, a key objective of this paper is to propose a model which is applicable for control due to clearly reduced computational cost. This roll gap model is combined with the dynamics of the mill stand and the bridle rolls in the entry and the exit section. By virtue of the flatness property of the entire model, the nonlinear control design for the mill is addressed by applying the flatness based control theory

A nonlinear optimization PID controller for BLDCM is designed. The design method is based on the fuzzy model for BLDCM other than conventional math model on some assumed conditions. The fuzzy model is gained through neuro-fuzzy identification. By virtue of nonlinear control design (NCD) toolbox in Matlab the controller is easily developed. Simulation and experiment result that the identified model fits the real BLDCM well and the designed controller has fairly strong robust performance

Automatic guidance of urban electric vehicles is addressed in this paper. It is shown that nonlinear control design (namely chained form conversion) and the use of a RTK GPS sensor allow to achieve curved path following with a very high accuracy. Extensive experiments, carried out with a Cycab vehicle, are discussed.

Linear equivalence of nonlinear systems is applied to a helicopter model. The nonlinear control design obtained allows a transformation of the nonlinear helicopter model to a set of four linear controllable and single-input subsystems to be obtained. The main difference between the application presented and other work is that the authors express the diffeomorphic map of the state-input space in explicit form. >

The concept of control Lyapunov-Razumikhin function (CLRF) has been introduced as a tool for designing globally stabilizing control law for time delay systems. The control law has the same form as the domination redesign control law for nondelay systems which is (inverse) optimal and, hence, provides infinite gain margin and a nonlinear equivalent of 60/spl deg/ phase margin. In this paper we show that the CLRF based control laws also posses robustness to input unmodeled dynamics. The robustness to static input uncertainties is the same as the one of optimal nondelay systems. The robustness to dynamic uncertainties proven in this paper is weaker than that of optimal systems.

A design method is presented for the analysis and synthesis of robust nonlinear controllers for chemical engineering systems. The method rigorously treats the effect of unmeasured disturbances and unmodeled dynamics on the stability and performance properties of a nonlinear system. The results utilise new extensions of structured singular value theory for analysis and recent synthesis results for approximate linearisation.

Compared to more conventional ships, little attention was given to nonlinear control design for ships sailing by the wind. Following our previous work, this paper addresses the issue of trajectory and reference input generation for a model that imitates the general behavior of sailing vessels. Specifically, we consider the generation of paths to perform a wearing maneuver. A feedforward controller scheme is then introduced to steer the modeled vehicle along this maneuver, and simulation results are presented as an illustration.

International audience; This paper presents a nonlinear control strategy based on dynamic feedback linearization control theory and a backstepping-like procedure for a multi-terminal voltage-source converter based high-voltage direct current (multi-terminal VSC-HVDC) system. The controller is able to provide asymptotic stability for the power transmission system with multiple terminals. In particular, it is shown that the zero dynamics (mostly representing the DC network) is exponentially stable. These results are obtained by a stability proof for the whole system under the proposed controller, and its performance is illustrated by computer simulations.