Variable Structure Model Reference Adaptive Control for autonomous steering of vehicle

In this paper, we consider the design of a variable structure model reference adaptive control (VS-MRAC) for plants with relative degree one without the knowledge of the sign of the plant high frequency gain. A switching method for the control signal, based on an appropriate monitoring function, is proposed. As a result, we show that after a finite number of switchings, the tracking error converges to zero at least exponentially. Interestingly enough, if the initial conditions of some states of the closed-loop system are zero, we show that at most one switching is needed.

Variable Structure Model Reference Adaptive Control with Unknown High Frequency Gain Sign

This paper presents an angular shaft speed control scheme of an induction motor. The induction motor modelling is performed through vector control with rotor flux orientation. The used control strategy is variable structure model reference adaptive control, that is applied to control uncertain plants. Its main characteristics are the use of a switched control law under a structure with a reference model and the need of only the input and output measures of the plant. The system is formed by a 0.25 hp induction motor with a squirrel cage rotor, supplied by a voltage source inverter with pulse width modulation and current control, and a Pentium-100 MHz microcomputer with acquisition cards. Practical results are presented upon different conditions of system functioning, assuring the efficiency of this strategy related to its robustness to load disturbances and parameters variations.

This paper presents the stability and robustness analysis of an indirect adaptive control based variable structure algorithm for uncertain plants with relative degree one. The indirect approach has been proposed as a way to get an easier design of the switching laws, compared to the direct relationship between the plant transfer function parameters and the physical parameters of the system. Here, a singular perturbation approach is used to establish the robustness of the controller in the presence of unmodelled dynamics and disturbances. It is shown that, for sufficiently small parasitics, the system remains stable with respect to some small residual set.

In this article, a unique and innovative design for addressing the speed synchronization problem in a multi-motor system using Brush less DC (BLDC), motors is presented by utilizing motor back emf equation and rotor position commonly called sensor less technique. In the proposed method, the system is modelled as a consensus problem of leader following multi-agent system (MAS), and a hybrid controller is designed by using Model Reference Adaptive Control (MRAC) along with Variable Structure (VS) control technique of Sliding Mode Control (SMC), herein called Variable Structure Model Reference Adaptive Control (VS-MRAC). The consensus algorithm of MAS (reformed w.r.t motor speed data), is fused with the hybrid controller to reach consensus on speed regulated by proposed hybrid controller. The stability of a system is endorse by designing a Lyapunov function. The efficiency of the proposed methodology is proven by simulations performed in MATLAB and the acquired results validate the success of proposed design methodology.

This paper presents an overview of a technique for the design of variable structure model reference adaptive control (VS-MRAC) systems, using only input-output data. The main ideas underlying the design and the analysis, as well as the main properties of the controller, are described having as point of departure a well known parameter adaptive MRAC scheme. Then, asymptotic properties of the VS-MRAC system are established taking into account the effect of the averaging filters necessary to implement some equivalent control signals. In particular, global exponential stability of the associated error system with respect to a small residual set is demonstrated. The effect of linear zones in the relay functions is assessed showing that they can alleviate the chattering phenomena. This is related with the fact that the VS-MRAC has a high-gain stability property. A procedure for noise sensitivity reduction is also proposed. Simulations illustrate the very satisfactory performance of the VS-MRAC in adverse operating conditions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

This paper considers the output feedback control of single input single output uncertain nonlinear systems without the matching condition. The approach is based on the control parametrization employed in classical model reference adaptive control (MRAC). The nonlinearities are allowed to depend not only on the plant output but also on the plant unmeasurable state. The variable structure model reference adaptive control (VS-MRAC) is redesigned with an appropriate state upper bound for the rejection of state dependent input disturbance. Global or semi-global exponential stability of the closed loop system with respect to a small residual set is achieved. A simplified version of VS-MRAC with constant modulation functions is applied to the nonlinear longitudinal dynamics of a Twin Otter aircraft for pitch pointing manoeuvre.

Neste artigo é apresentado o Controlador em Modo Dual Adaptativo Robusto (DMARC). O DMARC é um sistema de controle que combina as estratégias de Controle Adaptativo por Modelo de Referência (MRAC) com leis integrais de adaptação e o Controle Adaptativo por Modelo de Referência e Estrutura Variável (VS-MRAC) com leis chaveadas de acordo com a teoria de sistemas com estrutura variável. A idéia básica é incorporar as vantagens de desempenho transitório de um VS-MRAC, com as propriedades de regime permanente de um MRAC convencional. Desta forma, obtém-se um sistema de controle robusto a incertezas paramétricas e perturbações externas, com desempenho rápido e pouco oscilatório durante o transitório e um sinal de controle suave em regime permanente.

SummaryThis work proposes a control structure to be applied to robotic manipulators, which are articulated mechanical systems composed of links connected by joints. The proposed controller can be divided into two parts. The first one is a left inverse system, which is used to decouple the dynamic behavior of the joints. The second is a sliding mode controller, which is applied for each decoupled joint. It is important to note that the proposed structure, using only input/output measurements, reduces the control signal ‘chattering’, and it is robust to parametric uncertainties. Besides all the characteristics presented, the proposed structure simplifies the design of sliding mode controller to be applied in robotic manipulators. All these features are verified by simulations. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Designing an adequate controller for a plant with an arbitrary relative degree is still an active area of research. In this paper, a discrete variable structure model reference adaptive control using only input-output measurements (DVS-MRAC-IO) for not strictly positive real systems with a relative degree of two is proposed. In order to show the effectiveness of the proposed controller, a detailed stability analysis is studied using Lyapunov theory. Further, a straightforward generalization of DVS-MRAC-IO for systems with arbitrary relative degree is presented. Numerical results are used to show the effectiveness of the proposed methods.

Robustness and Alleviation of Chattering by New Modified Update Laws and Sigmoid Function in Variable Structure Adaptive Control

The goals of this paper are: (a) to investigate adaptive and fractional-order adaptive control algorithms for an automatic anesthesia process, using a closed-loop system, and (b) to develop an easy-to-use tool for MATLAB/Simulink to facilitate simulations for users with less knowledge about anesthesia and adaptive control. A model reference adaptive control structure was chosen for the entire system. First of all, to control the patient’s state during the surgery process, the patient mathematical model is useful, or even required for simulation studies. The pharmacokinetic/pharmacodynamics (PK/PD) model was determined using MATLAB’s SimBiology tool, starting from a previously available block diagram, and validated through simulation. Then, to achieve the desired control performances, two controllers are designed: a PI adaptive controller and a PIλ (PI-fractional) adaptive controller, using the MIT algorithm. The time response during anesthetic drug infusion for each patient can be plotted with the AnesthesiaGUIDE tool, which is also designed in MATLAB/Simulink. The tool was tested on data from 12 patients, subjected to general anesthesia, with successful results. Through this tool, the article provides a good opportunity for any user to experience with adaptive control for the anesthesia process.

SummaryThe rejection of unknown periodic disturbances in the plant output through adaptive feedback has been an active area of research. In most successful efforts, it is assumed that the plant model is a known LTI stable system. In this paper, we relax the assumption of stable known plant and consider the case where the plant model can be unstable with unknown parameters. We do assume, however, that the plant model is minimum phase and use the model reference adaptive control structure to meet the objectives of reference tracking and unknown periodic disturbance rejection without amplifying the effect of broadband noises. The cost of achieving these objectives is the use of overparameterization that adds to the number of computations. The main contribution of this paper is that it shows that the problem of rejecting unknown periodic disturbances can be solved for unstable plants with unknown parameters as long as they are minimum phase. Numerical examples illustrate the effectiveness of the proposed control methodology.

In the control algorithm of digital hydraulic position tracking system, there exists many modeling assumptions and limited robustness. By the combining of the sliding mode variable structure control and model reference adaptive control, the present essay is to design a new sliding mode adaptive controller and do a simulation analysis. The simulation results indicate that the controller has high precision in controlling and fast in responding. It overcomes the problem of the control precision's decreasing when the adaptive control is applied alone and the output of the system is zero and avoids the influences of the uncertain parameters and the external disturbance, thus the robustness of the system.

In order to improve the steering performance of vehicles on low adhesion roads, this paper proposed a drift control method by coordinating the steering angle and the rear wheel slip ratio. Because lateral force of rear wheels is saturated with high longitudinal slip ratio under the drift condition, a vehicle dynamic model considering the coupling of the rear wheels’ longitudinal and lateral force is established. In view of the fact that the lateral tire force is affected by the nonlinearity of sideslip angle and slip ratio, the vehicle dynamic model is complex and makes it difficult for controller design. Due to this, a description method of the nonlinear relationship is presented for simple which introduces a virtual control quantity representing the influence of slip ratio on lateral tire forces based on the function of tire force with sideslip angle and slip ratio. Then, a sliding mode control method is proposed to ensure the stability of the closed-loop system and an off-line two-dimensional map is constructed to convert the virtual control quantity into the actual control quantity. The simulation results in the high-precision vehicle dynamics simulation software show that even if the initial state is far from the equilibrium point of drift, the drift controller also can ensure the stability of the closed-loop system and achieve a good drift performance.