Showing papers by "Vicente Feliu-Batlle published in 2021"

Control of the temperature in a petroleum refinery heating furnace based on a robust modified Smith predictor.

Abstract: The robust control of the crude oil outlet temperature uniformity in a heating furnace of a petroleum refinery is addressed. A reliable dynamic model of the nominal process has been attained using a system identification procedure based on real-time data. This procedure yields a second order model with a dominant time-delay. A PI controller embedded in a modified Smith predictor structure is therefore proposed. Sensitivity and robustness properties of this control system are analytically obtained. Based on that, a tuning procedure is developed for this control system which has lower sensitivity to disturbances than the standard Smith predictor while guaranteeing the system stability when plant parameters change. Simulations are carried out of the proposed control system and other well-known linear advanced process control systems. The comparison of the obtained results shows the superior performance of our control system in most cases, both in rejecting a variety of disturbances and in maintaining the closed-loop stability when the process parameters change.

Control of Very Lightweight 2-DOF Single-Link Flexible Robots Robust to Strain Gauge Sensor Disturbances: A Fractional-Order Approach

Abstract: This article deals with the control of two degrees of freedom manipulators that have a flexible and very lightweight link. These robots have a single low-frequency and high-amplitude vibration mode. Their actuators have high friction, and their vibration sensors are often strain gauges that have offset and high-frequency noise. These problems reduce the robot precision and produce noisy control signals that saturate actuators. An efficient control system is proposed to overcome these drawbacks. Actuator friction effect is nearly removed by closing a high gain position control loop around the actuator. It causes the separation of the robot dynamics into the controlled actuator fast subsystem and the link dynamics slow subsystem. Based on that, an innovative control system is designed to remove vibrations using the singular perturbation theory combined with the input-state linearization technique. This control system includes fractional-order controllers that nearly remove unknown sensor offset and sensor ramp disturbances while reducing the high-frequency component of the control signal caused by sensor noise. Simulated and experimental results show the superior performance of these controllers over other standard integer-order controllers of similar complexity and nominal behavior.

Design of a PIα Controller for the Robust Control of the Steam Pressure in the Steam Drum of a Bagasse-Fired Boiler

Abstract: This paper proposes the design of a PI $^{\alpha }$ robust controller with which to regulate the steam pressure in the steam drum of a bagasse-fired boiler. The dynamic behavior of this process was identified by means of experimentation. This identification procedure yielded an equivalent third order plus time delay model, and showed wide process static gain variations. We, therefore, propose a new method with which to design fractional-order robust controllers for this kind of processes. This method is based on the exact attainment of certain nominal time specifications while using one of the parameters of the controller to maximize the gain margin. The controllers attained were shown to significantly outperform the robustness achieved by using PI or PID controllers, in the sense of reducing the Integral Absolute Error ( IAE ) and improving the steam pressure uniformity.

Improving the Detection of the Contact Point in Active Sensing Antennae by Processing Combined Static and Dynamic Information.

Abstract: The design and application of sensing antenna devices that mimic insect antennae or mammal whiskers is an active field of research. However, these devices still require new developments if they are to become efficient and reliable components of robotic systems. We, therefore, develop and build a prototype composed of a flexible beam, two servomotors that drive the beam and a load cell sensor that measures the forces and torques at the base of the flexible beam. This work reports new results in the area of the signal processing of these devices. These results will make it possible to estimate the point at which the flexible antenna comes into contact with an object (or obstacle) more accurately than has occurred with previous algorithms. Previous research reported that the estimation of the fundamental natural frequency of vibration of the antenna using dynamic information is not sufficient as regards determining the contact point and that the estimation of the contact point using static information provided by the forces and torques measured by the load cell sensor is not very accurate. We consequently propose an algorithm based on the fusion of the information provided by the two aforementioned strategies that enhances the separate benefits of each one. We demonstrate that the adequate combination of these two pieces of information yields an accurate estimation of the contacted point of the antenna link. This will enhance the precision of the estimation of points on the surface of the object that is being recognized by the antenna. Thorough experimentation is carried out in order to show the features of the proposed algorithm and establish its range of application.