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Output Robust Control with Anti-Windup Compensation for Robotic Boat

Name
Igor
Surname
Petranevsky
Scientific organization
ITMO University, Kronverkskiy pr. 49, St. Petersburg, 197101, Russia
Academic degree
-
Position
engineer, 4th year student
Scientific discipline
Information technologies
Topic
Output Robust Control with Anti-Windup Compensation for Robotic Boat
Abstract
In this work a problem of saturated control for a robotic boat with unknown parameters and unmeasurable velocity and acceleration is addressed. The controller design is based on the output robust control approach “consecutive compensator'' augmented with an integral loop, which allows to eliminate a static error and implement the anti-windup scheme. As result, the regulator generating the bounded control signal and avoiding windup was obtained. The efficiency of the proposed algorithm was illustrated by the experimental approval using the robotic boat setup
Keywords
Robotics, Output control, Robust control, Anti-Windup
Summary

In this paper a problem of saturated control for a robotic boat with unknown parameters and unmeasurable velocity and acceleration is addressed. The controller design is based on the output robust control approach ``consecutive compensator''. It was augmented with an integral loop, which allows to eliminate a static error and implement the anti-windup scheme to reduce overshoot of the output variable. As result, the regulator generating the bounded control signal and avoiding windup for the boat was obtained. The efficiency of the proposed algorithm was illustrated by the experimental approval using the robotic boat setup. The comparison between three types of controllers (regular consecutive compensator, integral modification and one equipped with anti-windup) is presented.

This practical study is devoted to development of simple control algorithms, which can be useful in stabilization tasks of various applications. The proposed in this paper robust output controller with anti-windup compensation has shown the satisfactory experimental results at the robotic boat setup. This approach is applicable for plants with bounded input and uncertain parameters. Its useful feature is a possibility to specify limits of the generated control signal with reduced (or even without) undesirable overshoot of the output variable. It is important for real technical systems due to their hardware constraints

The results of the experiments are presented in Figs.~\ref{experimental_approval_inputs} and \ref{experimental_approval_error}. Note that these plots correspond only to motion along X-axis. The original and saturated control signals generated by the consecutive compensator with anti-windup are depicted in Fig.~\ref{experimental_approval_inputs}. Three plots of the output variable are illustrated in Fig.~\ref{experimental_approval_error}. The green curve is assigned to the regular consecutive compensator (\ref{regular_control_law_experiment}), the blue one corresponds to the integral consecutive compensator (\ref{integral_control_law_experiment}) and the last red curve refers to the consecutive compensator equipped with the anti-windup scheme (\ref{control_law_AW_experiment}). The process of motion and visualization of the computer vision are shown in Fig.~\ref{experiment}. As it can be seen on the obtained plots the regular consecutive compensator leads to the small static error caused by the nonlinear input of the actuators. Small values of error lead to small control, which is not sufficient to counteract waves and move the boat. This effect is removed by the integral term, which accumulates the error value and increase the control signal. Note that increasing of the controller parameters is undesirable, because it may lead to self-oscillations of the boat. Smooth red curve is achieved by the anti-windup approach. Little oscillations of the boat are caused by wave disturbances and noise in the measurement channels.