Andres San-Millan

Bio: Andres San-Millan is an academic researcher from University of Castilla–La Mancha. The author has contributed to research in topics: Control theory & Fractional-order control. The author has an hindex of 7, co-authored 17 publications receiving 132 citations. Previous affiliations of Andres San-Millan include University of Essex.

Design of a teleoperated wall climbing robot for oil tank inspection

Abstract: This paper presents a climbing robot with wheeled locomotion which uses permanent magnets as adhesion mechanism. The robot designed is intended for the inspection of various types of ferromagnetic structures, such as ship hulls, wind turbine towers, bridges, and fuel tanks, in order to detect surface faults or cracks caused by, for example aging or atmospheric corrosion. The proposed robotic system consists of a cordless teleoperated mobile platform which can move on vertical ferromagnetic walls. The robot can be equipped with the various testing probes and cameras that are necessary for different inspection tasks. First, different prototypes of magnetic wall climbing robots are analyzed in order to establish the current state-of-the-art, and to provide the background required to analyse the main advantages and drawbacks of the prototypes presented. The design of the proposed robotic system is then explained, and details are provided of the new approach for the design of the permanent magnetic adhesion mechanism. Finally the mechanical and electrical construction, the control architecture implemented, and the human-machine interface for its control and teleoperation are presented too.

A Modified Positive Velocity and Position Feedback scheme with delay compensation for improved nanopositioning performance

Abstract: This paper presents a controller design to compensate the effects of time delay in a flexure-based piezoelectric stack driven nanopositioner. The effects of the time delay in flexure nanopositioners is illustrated and identified by means of experimentally obtaining the frequency response of the system. Moreover, a theoretical model which takes into account the dependence between the sampling time and the delay introduced is proposed. The proposed control design methodology not only accommodates for time delay but also ensures the robust stability and allows its application to systems with a larger delay than other schemes proposed previously. Limitations and future work are discussed.

A Fast Online Estimator of the Two Main Vibration Modes of Flexible Structures From Biased and Noisy Measurements

Abstract: Vibrations are present in many mechanical structures and machines, and are often associated with their elastic parts. Characterizing these vibrations, i.e., obtaining their frequencies, amplitudes and phases, is of most interest in many applications ranging from the maintenance of civil structures to motion control. This paper presents a method for the online and reliable identification of the defining parameters of two unknown sinusoidal signals through the use of their measured sum in the presence of noise and an offset. It is based on the algebraic derivative approach, defined in the frequency domain, which yields exact calculation formulae for the unknown parameters of the signal, i.e., the amplitudes, phases, and frequencies of the two sinusoids and the value of the constant term. The online estimation is performed in a time interval which is only a fraction of the first full cycle of the slower component of the measured signal. This feature allows the algorithm to be used to monitor time-varying parameters in these vibration signals. This algorithm has been used in experiments with a flexible beam, which is a representative platform of a vibrating mechatronic system. It estimated all the vibration signal parameters quickly and accurately, proved to be insensitive to high-frequency noises, and accurately tracked the time variations of the signal parameters.

Butterworth Pattern-based Simultaneous Damping and Tracking Controller Designs for Nanopositioning Systems

Abstract: The Butterworth filter is known to have maximally flat response. Incidentally, the same response is desired in precise positioning systems. This paper presents a method for obtaining a closed-loop Butterworth filter pattern using common control schemes for positioning applications, i.e. Integral Resonant Control (IRC), Integral Force Feedback (IFF), Positive Position Feedback (PPF), and Positive Velocity and Position Feedback (PVPF). Simulations show a significant increase in bandwidth over traditional design methods and verify the desired pole placement is achieved. The simulations also show a significant limitation of the achievable bandwidth in the case of IRC, IFF, and PPF. For this reason, only PVPF is considered in experimental analysis. Experiments are performed using a two-axis serial kinematic nanopositioning stage. The results show a significant improvement in bandwidth and increased positioning accuracy, specifically at the turn-around point. This allows a greater portion of the scan to be used and improved positioning accuracy at high scanning speeds.

Review on the use of piezoelectric materials for active vibration, noise, and flow control

Abstract: Considering the number of applications, and the quantity of research conducted over the past few decades, it wouldn't be an overstatement to label the piezoelectric materials as the cream of the crop of the smart materials. Among the various smart materials, the piezoelectric materials have emerged as the most researched material for practical applications. They owe it to a few key factors like low cost, large frequency bandwidth of operation, availability in many forms, and the simplicity offered in handling and implementation. For piezoelectric materials, from an application standpoint, the area of active control of vibration, noise, and flow, stands, alongside energy harvesting, as the most researched field. Over the past three decades, several authors have used piezoelectric materials as sensors and actuators, to (i) actively control structural vibrations, noise and aeroelastic flutter, (ii) actively reduce buffeting, and (iii) regulate the separation of flows. These studies are spread over several engineering disciplines-starting from large space structures, to civil structures, to helicopters and airplanes, to computer hard disk drives. This review is an attempt to concise the progress made in all these fields by exclusively highlighting the application of the piezoelectric material. The research carried out in the past five years, in the areas of modeling, and optimal positioning of piezoelectric actuators/sensors, for active vibration control, are covered. Along with this, investigations into different control algorithms, for the piezoelectric based active vibration control, are also reviewed. Studies reporting the use of piezoelectric modal filtering and self sensing actuators, for active vibration control, are also surveyed. Additionally, research on semi-active vibration control techniques like the synchronized switched damping (on elements like resistor, inductor, voltage source, negative capacitor) has also been covered

Automated Robotic Monitoring and Inspection of Steel Structures and Bridges

Abstract: This paper presents visual and 3D structure inspection for steel structures and bridges using a developed climbing robot. The robot can move freely on a steel surface, carry sensors, collect data and then send to the ground station in real-time for monitoring as well as further processing. Steel surface image stitching and 3D map building are conducted to provide a current condition of the structure. Also, a computer vision-based method is implemented to detect surface defects on stitched images. The effectiveness of the climbing robot's inspection is tested in multiple circumstances to ensure strong steel adhesion and successful data collection. The detection method was also successfully evaluated on various test images, where steel cracks could be automatically identified, without the requirement of some heuristic reasoning.