Samaherni Dias

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.

Modular variable structure adaptive backstepping controller: Design and stability analysis☆

Abstract This paper presents the design and stability analysis of a Modular Variable Structure Adaptive Backstepping Controller (MVS-ABC) for plants with arbitrary relative degree, using only input/output measurements. In order to improve the transient response of adaptive backstepping approach via modular design, switching laws are proposed instead of traditional integral adaptive laws. Robustness properties with respect to external disturbances are also demonstrated. Furthermore, simplified algorithms are presented, where the number of relays was significantly reduced (only one is necessary). Simulation results for an unstable system with relative degree three are shown.

Robust Adaptive Control Applied to Chua's Circuit

Abstract Many practical systems (for example: robotic systems, power system and electronic circuits) are multiple-input multiple-output nonlinear systems and some of them have coupled relations between inputs and outputs. Besides all that, these systems can suffer from plant uncertainties and external disturbances. Any control techniques to be applied to these systems are complex. This work proposes a new control structure, based on the union between the variable structure model reference adaptive control and a decouple left-inverse technique, to transform the nonlinear multiple-inputs multiple-outputs system into a number of single-input single-output linear systems. In that case each input affects only one output and with a desired closed-loop performance. The proposed structure uses only input/output measurements, improves the transient performance (reducing the output “chattering”) and it is robust to parametric uncertainties and disturbances. All these features are demonstrated by simulation results of a simple electronic circuit that exhibits chaotic behavior (Chuas circuit). The proposed structure may be used to smooth the control signal, thus reducing the chattering in the output signal.

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.

Soccer robot identification using Kernel based weighted least squares

In this paper we present an application of weighted least squares WLS for identification of the dynamics of soccer robot (MIROSOT category). We used a linear model represented by state space equations to represent the dynamics of the robot and used an off-line WLS algorithm to find the coefficients of the linear model. Our main contribution is to use a kernel based (gram matrix) weight matrix to avoid the effect of the outliers in the noise acquired during the data acquisition phase for the training. The results show that this approach is better them using non-weighted algorithms.

Real time angular velocity measure using median filter

We present a simple approach to reduce the noise present in velocity measurements when using encoders. The approach is to use the median filter together with a simple first order linear filter and show that this combination avoids the errors due to warp of the encoder (when the angle goes from 2π back to 0 of vice versa). We test this new method and compare with different kinds of filters and algorithms to avoid the warp problem. We show that the proposed method can be implemented only with simple arithmetic and is perfectly suitable for embedded and hardware implementation.

Stability analysis of a Variable Structure Adaptive Backstepping Controller

This paper presents the stability analysis of a Variable Structure Adaptive Backstepping Controller (VS-ABC) for linear plants with relative degree one. Robustness properties with respect to parametric uncertainties and external disturbances are demonstrated, as well as, the system convergence in finite time. Moreover, simulation results are included for an unstable second order plant in order to corroborate the theoretical studies.