scholarly journals A Robust Observer—Based Adaptive Control of Second—Order Systems with Input Saturation via Dead-Zone Lyapunov Functions

Computation ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 82
Author(s):  
Alejandro Rincón ◽  
Gloria M. Restrepo ◽  
Fredy E. Hoyos
Keyword(s):  
Lyapunov Functions ◽  
Dead Zone ◽  
Tracking Error ◽  
Input Saturation ◽  
Chemical Reactor ◽  
Second Order ◽  
Control Law ◽  
Compact Set ◽  
State Variables ◽  
Robust Observer

In this study, a novel robust observer-based adaptive controller was formulated for systems represented by second-order input–output dynamics with unknown second state, and it was applied to concentration tracking in a chemical reactor. By using dead-zone Lyapunov functions and adaptive backstepping method, an improved control law was derived, exhibiting faster response to changes in the output tracking error while avoiding input chattering and providing robustness to uncertain model terms. Moreover, a state observer was formulated for estimating the unknown state. The main contributions with respect to closely related designs are (i) the control law, the update law and the observer equations involve no discontinuous signals; (ii) it is guaranteed that the developed controller leads to the convergence of the tracking error to a compact set whose width is user-defined, and it does not depend on upper bounds of model terms, state variables or disturbances; and (iii) the control law exhibits a fast response to changes in the tracking error, whereas the control effort can be reduced through the controller parameters. Finally, the effectiveness of the developed controller is illustrated by the simulation of concentration tracking in a stirred chemical reactor.

scholarly journals Adaptive Control for a Biological Process under Input Saturation and Unknown Control Gain via Dead Zone Lyapunov Functions

2020 ◽  
Vol 11 (1) ◽  
pp. 251
Author(s):  
Alejandro Rincón ◽  
Fredy E. Hoyos ◽  
John E. Candelo-Becerra
Keyword(s):  
Lower Bounds ◽  
Distinctive Feature ◽  
Biological Process ◽  
Dead Zone ◽  
Tracking Error ◽  
Input Saturation ◽  
Auxiliary System ◽  
Upper And Lower Bounds ◽  
Compact Set ◽  
Control Gain

In this work, substrate control of a biological process with unknown varying control gain, input saturation, and uncertain reaction rate is addressed. A novel adaptive controller is proposed, which tackles the combined effect of input saturation and unknown varying control gain with unknown upper and lower bounds. The design is based on dead zone radially unbounded Lyapunov-like functions, with the state backstepping as control framework. The convergence of the modified tracking error and the boundedness of the updated parameters are ensured by means of the Barbalat’s lemma. As the first distinctive feature, a new second-order auxiliary system is proposed that tackles the effect of saturated input and the unknown varying control gain with unknown upper and lower bounds. As the second distinctive feature, the modified tracking error converges to a compact set whose width is user-defined, so that it does not depend on bounds of either external disturbances, model terms, or model coefficients. The convergence region of the current tracking error is determined for the closed loop system subject to the formulated controller and the proposed auxiliary system. Finally, numerical simulation illustrates the performance of the proposed controller.

Enhanced Composite Nonlinear Control Technique using Adaptive Control for Nonlinear Delayed Systems

2020 ◽  
Vol 13 (3) ◽  
pp. 396-404
Author(s):  
Sonal Singh ◽  
Shubhi Purwar
Keyword(s):  
Adaptive Control ◽  
Actuator Saturation ◽  
Input Saturation ◽  
Chemical Reactor ◽  
Control Technique ◽  
Control Law ◽  
Nonlinear Feedback ◽  
Composite Nonlinear Feedback ◽  
Delayed Systems ◽  
Analysis Of Stability

Background and Introduction: The proposed control law is designed to provide fast reference tracking with minimal overshoot and to minimize the effect of unknown nonlinearities and external disturbances. Methods: In this work, an enhanced composite nonlinear feedback technique using adaptive control is developed for a nonlinear delayed system subjected to input saturation and exogenous disturbances. It ensures that the plant response is not affected by adverse effect of actuator saturation, unknown time delay and unknown nonlinearities/ disturbances. The analysis of stability is done by Lyapunov-Krasovskii functional that guarantees asymptotical stability. Results: The proposed control law is validated by its implementation on exothermic chemical reactor. MATLAB figures are provided to compare the results. Conclusion: The simulation results of the proposed controller are compared with the conventional composite nonlinear feedback control which illustrates the efficiency of the proposed controller.

Deterministic robust control design for an iron core linear drive including second-order electrical dynamics

2018 ◽  
Vol 232 (8) ◽  
pp. 951-962 ◽  
Author(s):  
Fernando Villegas ◽  
Rogelio Hecker ◽  
Miguel Peña
Keyword(s):  
Robust Control ◽  
Tracking Error ◽  
Second Order ◽  
Iron Core ◽  
State Variables ◽  
State Transformation ◽  
Robust Controller ◽  
Current Controller ◽  
Bounded State ◽  
Robust Control Design

This work proposes a deterministic robust controller to improve tracking performance for a linear motor, taking into account the electrical dynamics imposed by a commercial current controller. The design is split in two parts by means of the backstepping technique, in which the first part corresponds to a typical deterministic robust controller, neglecting the electrical dynamics. In the second part, a second-order electrical dynamics is considered using a particular state transformation. There, the proposed control law is composed of a term to compensate the known part of the model and a robust control term to impose a bound on the effect of uncertainties on tracking error. Stability and boundedness results for the complete controller are given. To this effect, a general result on boundedness and stability of nonlinear systems with conditionally bounded state variables is derived first. Finally, experimental results for the complete controller show an improvement on tracking error of up to 31.7% when compared with the results from the typical controller that neglects the electrical dynamics.

scholarly journals Approximation-Based Quantized State Feedback Tracking of Uncertain Input-Saturated MIMO Nonlinear Systems with Application to 2-DOF Helicopter

Mathematics ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 1062
Author(s):  
Byung Mo Kim ◽  
Sung Jin Yoo
Keyword(s):  
Nonlinear Systems ◽  
State Feedback ◽  
Tracking Error ◽  
Multiple Input Multiple Output ◽  
Input Saturation ◽  
Lyapunov Theory ◽  
Experimental Results ◽  
State Variables ◽  
Mimo Nonlinear Systems ◽  
Feedback Tracking

This paper addresses an approximation-based quantized state feedback tracking problem of multiple-input multiple-output (MIMO) nonlinear systems with quantized input saturation. A uniform quantizer is adopted to quantize state variables and control inputs of MIMO nonlinear systems. The primary features in the current development are that (i) an adaptive neural network tracker using quantized states is developed for MIMO nonlinear systems and (ii) a compensation mechanism of quantized input saturation is designed by constructing an auxiliary system. An adaptive neural tracker design with the compensation of quantized input saturation is developed by deriving an augmented error surface using quantized states. It is shown that closed-loop stability analysis and tracking error convergence are conducted based on Lyapunov theory. Finally, we give simulation and experimental results of the 2-degrees-of-freedom (2-DOF) helicopter system for verifying to the validity of the proposed methodology where the tracking performance of pitch and yaw angles is measured with the mean squared errors of 0.1044 and 0.0435 for simulation results, and those of 0.0656 and 0.0523 for experimental results.

scholarly journals An Improved Robust Adaptive Controller for a Fed-Batch Bioreactor with Input Saturation and Unknown Varying Control Gain via Dead-Zone Quadratic Forms

Computation ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 100
Author(s):  
Alejandro Rincón ◽  
Gloria María Restrepo ◽  
Óscar J. Sánchez
Keyword(s):  
Distinctive Feature ◽  
Quadratic Forms ◽  
Dead Zone ◽  
Tracking Error ◽  
Input Saturation ◽  
Adaptive Controller ◽  
Fed Batch ◽  
Batch Bioreactor ◽  
Control Gain ◽  
Robust Adaptive

In this work, a new adaptive controller is designed for substrate control of a fed-batch bioreactor in the presence of input saturation and unknown varying control gain with unknown upper and lower bounds. The output measurement noise and the unknown varying nature of reaction rate and biomass concentration and water volume are also handled. The design is based on dead zone quadratic forms. The designed controller ensures the convergence of the modified tracking error and the boundedness of the updated parameters. As the first distinctive feature, a new robust adaptive auxiliary system is proposed in order to tackle input saturation and control gain uncertainty. As the second distinctive feature, the modified tracking error converges to a compact region whose bound is user-defined, in contrast to related studies where the convergence region depends on upper bounds of either external disturbances, system states, model parameters or terms and model parameter values. Simulations confirm the properties of the closed loop behavior.

Observer based direct adaptive fuzzy second-order-like sliding mode control for unknown nonlinear systems

2020 ◽  
pp. 095440892095259
Author(s):  
Hongzhuang Wu ◽  
Songyong Liu ◽  
Cheng Cheng ◽  
Changlong Du
Keyword(s):  
Sliding Mode Control ◽  
Control Method ◽  
Nonlinear Dynamical Systems ◽  
Sliding Mode ◽  
Tracking Error ◽  
Second Order ◽  
Control Law ◽  
Adaptive Fuzzy ◽  
Mode Control ◽  
The Stability

This work proposes a novel observer based direct adaptive fuzzy second-order-like sliding mode control (SMC) method for a certain class of high order unknown nonlinear dynamical systems with unmeasurable states. An observer is firstly developed to estimate the tracking error vector directly, and the stability of the observer is analyzed based on Meyer-Kalman-Yakubovich (MKY) lemma. Based on the observer, the equivalent control law is approximated by a double-input single-output fuzzy logic system (FLS), in which the observation of the sliding surface and its derivative are applied as the inputs. In addition, an adaptive switching control law is added to mitigate the system chattering and improve the stability of the system. The free parameters of the controller are adjusted online by the adaptive laws that are derived from the Lyapunov stability analysis. Finally, the convergence of the overall closed-loop system is demonstrated, and the simulation examples illustrate the efficacy of the proposed control method.

Adaptive consensus for heterogeneous unknown nonlinear multi-agent systems with asymmetric input dead-zone: A finite-time approach

2021 ◽  
pp. 014233122110240
Author(s):  
Mehdi Zamanian ◽  
Farzaneh Abdollahi ◽  
Seyyed Kamaleddin Yadavar Nikravesh
Keyword(s):  
Neural Networks ◽  
Finite Time ◽  
Sliding Mode ◽  
Dead Zone ◽  
Second Order ◽  
Compact Set ◽  
Multi Agent Systems ◽  
Agent Systems ◽  
Position Errors ◽  
Multi Agent

This study deals with the adaptive finite-time consensus problem of heterogeneous multi-agent systems composed of first-order and second-order agents with unknown nonlinear dynamics and asymmetric input dead-zone under connected undirected topology. Under the proposed protocol and adaptive laws, a sliding mode variable for every agent converges to a compact set in finite time, and also the position errors and the velocity errors (for second-order agents) between any two agents converge to a small desired neighborhood of the origin in finite time. Each agent requires its states and the relative positions of its neighbors. By applying sliding mode control, the external disturbances, and the imperfect approximation of neural networks are rejected. The unknown terms of the agents’ dynamics are approximated using radial basis function neural networks. The adaptive compensator plus dead-zone is applied to overcome the asymmetric input dead-zone. Based on Lyapunov stability theory, analysis is led on stability. Different from the previous works, the global information graph is not used in the proposed protocol. Finally, our approach is examined for two examples to evaluate its performance.

Uniformly ultimately bounded tracking control of sandwich systems with nonsymmetric sandwiched dead-zone nonlinearity and input saturation constraint

2021 ◽  
pp. 107754632098794
Author(s):  
Meysam Azhdari ◽  
Tahereh Binazadeh
Keyword(s):  
Dead Zone ◽  
Input Saturation ◽  
Closed Loop System ◽  
Unknown Parameters ◽  
External Disturbances ◽  
Uniformly Ultimately Bounded ◽  
Output Tracking ◽  
Saturation Constraint ◽  
Two Phases ◽  
Practical Constraints

This article studies the uniformly ultimately bounded output tracking problem of uncertain nonlinear sandwich systems with sandwiched dead-zone nonlinearity in the presence of some practical constraints such as nonsymmetric input saturation, model uncertainties, time-varying external disturbances, and unknown parameters. Due to the existence of both dead-zone and saturation nonlinearities, the design process is more complicated; therefore, to solve the design complexities, the designing process is divided into two phases. The proposed method leads to output tracking with acceptable accuracy. Moreover, all signals in the closed-loop system are ultimately bounded. Simulation results illustrate the applicability and effectiveness of the proposed method by its application on two practical sandwich systems (robotic system and electrohydraulic servo press system).

Observer-based synchronization of uncertain chaotic systems subject to input saturation

2017 ◽  
Vol 40 (8) ◽  
pp. 2526-2535 ◽  
Author(s):  
S Mohammadpour ◽  
T Binazadeh
Keyword(s):  
Chaotic Systems ◽  
Actuator Saturation ◽  
Input Saturation ◽  
State Variables ◽  
Adaptive Stabilization ◽  
External Disturbances ◽  
Van Der Pol ◽  
Robust Synchronization ◽  
Effective Performance ◽  
Uncertain Chaotic Systems

This paper considers the synchronization between two chaotic systems (i.e. master and slave systems) in the presence of practical constraints. The considered constraints are: the unavailability of state variables of both master and slave system, the presence of non-symmetric input saturation, model uncertainties and/or external disturbances (matched and/or unmatched). Considering these constraints, an adaptive robust observer-based controller is designed, which guarantees synchronization between the chaotic systems. For this purpose, a theorem is given and, according to a Lyapunov adaptive stabilization approach, it is proved that the robust synchronization via the proposed observer-based controller is guaranteed in the presence of actuator saturation and it is shown that even if the control signal is saturated, the proposed controller leads to a robust synchronization objective. Finally, in order to show the applicability of the proposed controller, it is applied on the Van der Pol chaotic systems. Computer simulations verify the theoretical results and show the effective performance of the proposed controller.

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