Josenalde Oliveira

Design and stability analysis of an indirect variable structure model reference adaptive control

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.

A swarm intelligence-based tuning method for the Sliding Mode Generalized Predictive Control.

This work presents an automatic tuning method for the discontinuous component of the Sliding Mode Generalized Predictive Controller (SMGPC) subject to constraints. The strategy employs Particle Swarm Optimization (PSO) to minimize a second aggregated cost function. The continuous component is obtained by the standard procedure, by Quadratic Programming (QP), thus yielding an online dual optimization scheme. Simulations and performance indexes for common process models in industry, such as nonminimum phase and time delayed systems, result in a better performance, improving robustness and tracking accuracy.

Variable Structure Adaptive Backstepping Controller for plants with arbitrary relative degree based on modular design

This paper presents a Variable Structure Adaptive Backstepping Controller (VS-ABC) for linear plants with arbitrary relative degree, using only input/output measurements. In order to improve the transient response, switching laws are proposed in the adaptive backstepping approach via modular design, instead of the integral adaptive laws. Furthermore, simplified algorithms are presented for the VS-ABC, motivating applications on industrial environments. Simulation results for an unstable system with relative degree three are shown.

Design and stability analysis of a Variable Structure Adaptive Pole Placement Controller for first order systems

This paper shows the design and the stability analysis of a Variable Structure Adaptive Pole Placement Controller (VS-APPC) for first order plants, both for regulation and tracking. The VS-APPC was proposed in previous papers and it provides a fast and non-oscillatory transient. Besides, it suggests robustness to parameter uncertainties and disturbances, by using switching adaptive laws for the plant parameters, instead of the traditional integral ones, as the gradient method. Additionally, simulations results are shown.

Indirect Binary Model Reference Adaptive Control

This paper proposes an Indirect Binary Model Reference Adaptive Controller (IB-MRAC), with the main objective of combining the steady-state features of controllers based in integral parameter adaptation with the fast and non oscillatory transient of variable structure based strategies. The indirect approach offers the possibility to get an easier controller design, either in the selection of the initial estimatives for the plant parameters or in the definition of a suitable region (ball) in which these ones should not escape. These more intuitive selections are due to the direct relationship between the plant parameters and physical system parameters, as inertia moments, resistances, capacitances, etc. The choice of adaptive gains defines how the IB-MRAC behaves between the Indirect MRAC (IMRAC) and the recently proposed Indirect Variable Structure Model Reference Adaptive Control (IVS-MRAC). Simulations to an unstable second order plant and a stability analysis for plants of relative degree one are presented, ensuring the global stability of system, considering a persistently exciting reference signal.

A Modified Design for the VS-MRAC Based on the Indirect Approach: Stability Analysis

Abstract Recently, an alternative to achieve a robust controller that provides a straightforward and intuitive design and tuning of its parameters named Indirect Variable Structure Model Reference Adaptive Controller (IVS-MRAC) was presented for relative degree one LTI plants, suggesting to be globally asymptotically stable with superior transient behavior and disturbance rejection properties. Its novelty is in the procedure to obtain the bounds for the relays amplitudes, used in the switching laws. These bounds are now associated with the plant parameters, instead of the controller parameters. In this paper, a modification is made on the plant high frequency gain switching law, in order to develop a first formal stability analysis, considering the presence of input disturbances and unmodeled dynamics. It is shown that the overall system error is stable with respect to some small residual set.

Smooth Adaptive Robust Temperature Control of a Seed Drying System

Abstract This paper addresses the problem of maintaining the temperature precisely tuned inside a seed drying system, in order to avoid thermal damage to that sensible biological entity and thus guarantee the right conditions for storage. This objective is achieved through an adaptive robust technique, known as Shunt Indirect Variable Structure Model Reference Adaptive Control (SIVS-MRAC), which has shown to be insensitive to external disturbances and unmodeled dynamics, although it presents a high frequency switching control signal that might be undesirable or even not compatible with some actuators. Here, besides the low control signal magnitude, control signal smoothness is obtained by using output error dependant linear regions and the equivalent control method. Simulations results are presented comparing the usage of such a technique.

Shunt Indirect Variable Structure Model Reference Adaptive Controller for plants with arbitrary relative degree

This paper extends the results and features of the recently proposed Indirect Variable Structure Model Refer- ence Adaptive Controller (IVS-MRAC) for non-minimum-phase plants and systems with arbitrary relative degree, through a suitable connection with a parallel feedforward (shunt) compensator, which turns the augmented system (plant + shunt) hyper minimum-phase. Simulations suggest that overall system properties are kept, such as fast transient and robustness to parametric variations, being these characteristics associated with sliding modes control techniques.

Automation and Control in Greenhouses: State-of-the-Art and Future Trends

This paper presents the state-of-the-art in terms of automation and control for protected cultivation in greenhouses. Aspects such as modeling, instrumentation, energy optimization and applied robotics are considered, aiming at not only to identify latest research topics, but also to foster continuous improvement in key cutting-edge problems.

Sliding Mode Generalized Predictive Control Based on Dual Optimization

This work presents a new approach to tune the parameters of the discontinuous component of the Sliding Mode Generalized Predictive Controller (SMGPC) subject to constraints. The strategy employs Particle Swarm Optimization (PSO) to minimize a second aggregated cost function. The continuous component is obtained by the standard procedure, by Sequential Quadratic Programming (SQP), thus yielding a dual optimization scheme. Simulations and performance indexes for a non minimum linear model result in a better performance, improving robustness and tracking accuracy.