Showing papers in "IEEE Control Systems Magazine in 2013"
TL;DR: In this article, a review of feedback control design for a family of robotic aerial vehicles with vertical take-off and landing (VTOL) capabilities such as quadrotors, ducted-fan tail-sitters, and helicopters is presented.
Abstract: This article is an introduction to feedback control design for a family of robotic aerial vehicles with vertical take-off and landing (VTOL) capabilities such as quadrotors, ducted-fan tail-sitters, and helicopters. Potential applications for such devices, like surveillance, monitoring, or mapping, are varied and numerous. For these applications to emerge, motion control algorithms that guarantee a good amount of robustness against state measurement/ estimation errors and unmodeled dynamics like, for example, aerodynamic perturbations, are needed. The feedback control methods considered here range from basic linear control schemes to more elaborate nonlinear control solutions. The modeling of the dynamics of these systems is first recalled and discussed. Then several control algorithms are presented and commented upon in relation to implementation issues and various operating modes encountered in practice, from teleoperated to fully autonomous flight. Particular attention is paid to the incorporation of integral-like control actions, often overlooked in nonlinear control studies despite their practical importance to render the control performance more robust with respect to unmodeled or poorly estimated additive perturbations.
288 citations
TL;DR: The management of the urban water cycle is a subject of increasing interest because of its social, economic, and environmental impact as discussed by the authors, and the most important issues include sustainable use of limited resources and the reliability of service to consumers with adequate quality and pressure levels, as well as the urban drainage management to prevent flooding and polluting discharges to the environment.
Abstract: The management of the urban water cycle (UWC) is a subject of increasing interest because of its social, economic, and environmental impact. The most important issues include the sustainable use of limited resources and the reliability of service to consumers with adequate quality and pressure levels, as well as the urban drainage management to prevent flooding and polluting discharges to the environment.
190 citations
TL;DR: Control problems such as multirobot control, distributed intelligence, swarm intelligence, distributed decision, distributed cognition, congestion control in networks, collective motion in biology, oscillator synchronization in physics, parallelization in optimization theory, distributed estimation, cooperative estimation, equilibria in economics, social interaction modeling, and game theory may be analyzed under the theory of interconnected dynamic systems.
Abstract: Control problems such as multirobot control, distributed intelligence, swarm intelligence, distributed decision, distributed cognition, congestion control in networks, collective motion in biology, oscillator synchronization in physics, parallelization in optimization theory, distributed estimation, cooperative estimation, equilibria in economics, social interaction modeling, and game theory may be analyzed under the theory of interconnected dynamic systems. Those topics have several overlapping research communities; for that reason they are characterized by different definitions and a variety of approaches ranging from rigorous mathematical analysis to trial-and-error experimental study or emulation by observation of natural phenomena. The areas involved concern robotics, dynamic systems, computer science, signal theory, biology, economics, and mathematics. A shared taxonomy is missing; for example, dynamic systems can be identified in robots, agents, nodes, processors, and entities. An ensemble is called a group, network, platoon, swarm, team, and cluster, and the algorithms are defined as controllers, protocols, and dynamics. In the following, the term agent is used to denote the single dynamic system and network or collective the ensemble.
190 citations
Journal Article•
TL;DR: In this article, a review of feedback control design for a family of robotic aerial vehicles with vertical take-off and landing (VTOL) capabilities such as quadrotors, ducted-fan tail-sitters, and helicopters is presented.
Abstract: This article is an introduction to feedback control design for a family of robotic aerial vehicles with vertical take-off and landing (VTOL) capabilities such as quadrotors, ducted-fan tail-sitters, and helicopters. Potential applications for such devices, like surveillance, monitoring, or mapping, are varied and numerous. For these applications to emerge, motion control algorithms that guarantee a good amount of robustness against state measurement/ estimation errors and unmodeled dynamics like, for example, aerodynamic perturbations, are needed. The feedback control methods considered here range from basic linear control schemes to more elaborate nonlinear control solutions. The modeling of the dynamics of these systems is first recalled and discussed. Then several control algorithms are presented and commented upon in relation to implementation issues and various operating modes encountered in practice, from teleoperated to fully autonomous flight. Particular attention is paid to the incorporation of integral-like control actions, often overlooked in nonlinear control studies despite their practical importance to render the control performance more robust with respect to unmodeled or poorly estimated additive perturbations.
122 citations
TL;DR: In this paper, the authors describe quantitative tools to drive the user's choice toward a suitable compromise in a probabilistic cost function, where a cost value can only be guaranteed with a certain probability.
Abstract: Many problems in systems and control, such as controller synthesis and state estimation, are often formulated as optimization problems. In many cases, the cost function incorporates variables that are used to model uncertainty, in addition to optimization variables, and this article employs uncertainty described as probabilistic variables. In a probabilistic setup, a cost value can only be guaranteed with a certain probability. Like pulling down one end of a rope wrapped around a pulley lifts the other end, decreasing the probability improves the cost value. This article analyzes this trade-off and describes quantitative tools to drive the user's choice toward a suitable compromise.
86 citations
TL;DR: The polynomial chaos expansions (PCEs) as discussed by the authors were proposed as a method for probabilistic uncertainty quantification in nonlinear dynamical systems and applied in the control literature.
Abstract: One purpose of the "Historical Perspectives" column is to look back at work done by pioneers in control and related fields that has been neglected for many years but was later revived in the control literature. This column discusses the topic of Norbert Wiener's most cited paper, which proposed polynomial chaos expansions (PCEs) as a method for probabilistic uncertainty quantification in nonlinear dynamical systems. PCEs were almost completely ignored until the turn of the new millennium, when they rather suddenly attracted a huge amount of interest in the noncontrol literature. Although the control engineering community has studied uncertain systems for decades, all but a handful of researchers in the systems and control community have ignored PCEs. The purpose of this column is to present a concise introduction to PCEs, provide an overview of the theory and applications of PCE methods in the control literature, and to consider the question of why PCEs have only recently appeared in the control literature.
80 citations
TL;DR: The interaction between sampling and the behavior of continuous-time systems is an important ingredient in all real-world signals and systems problems.
Abstract: Modern signal processing and control algorithms are invariably implemented digitally, yet most real-world systems evolve in continuous time. Hence, the interaction between sampling and the behavior of continuous-time systems is an important ingredient in all real-world signals and systems problems.
75 citations
TL;DR: In this article, the authors focus on the design and control of nanopo-sitioning systems (nanoposi-tioners) that operate mostly in a repetitive fashion, and the desired motion trajectory of the nanopositioner repeats from one operating cycle to the next.
Abstract: This article focuses on the design and control of nanopo-sitioning systems (nanoposi-tioners) that operate mostly in a repetitive fashion. In addition to accuracy, speed is also a crucial requirement for these systems. Multi-axis nanopositioners are critical in applications such as atomic force microscopy (AFM) [1], fiber optic alignment [2], micro- and nanoma-chining [3], [4], and nanometrology [5], [6]. More specifically, for video-rate scanning probe microscopy (SPM) and high-throughput probe-based nano-fabrication [7], the desired motion trajectory of the nanopositioner repeats from one operating cycle to the next and the motion should be as fast and accurate as possible. However, vibrations caused by mechanical resonance are a major factor limiting the speed. Typically, the bandwidth of these systems is limited by the first mode of vibration [8], [9].
62 citations
TL;DR: In this paper, a simple model-based approach is presented for the robust and rapid detection of EFCS failure cases, which may affect structural loading, and real flight tests have confirmed that a high level of performance and robustness can be obtained.
Abstract: Many innovative solutions have been developed by the aeronautical sector toward achieving the future "sustainable" aircraft that will be cleaner, quieter, smarter, and more affordable. Weight reduction is one of the most significant contributors to sustainability, as it improves aircraft performance (fuel consumption, noise, range) and consequently decreases its environmental footprint. This article deals with two challenging electrical flight control system (EFCS) failure cases, which may affect structural loading. A simple model-based approach is presented for the robust and rapid detection of such failures. The techniques were tested and validated at the Airbus test facility, and real flight tests have confirmed that a high level of performance and robustness can be obtained.
43 citations
TL;DR: Vascular networks are of special interest in medical microrobotics since they allow navigable agents to be delivered anywhere within the body and would allow targeted surgical, diagnostic, and therapeutic interventions.
Abstract: Although navigation control has been applied in a multitude of environments, relatively little is known about the challenges and issues of navigation control in the vascular network. In an adult human, the vascular network consists of nearly 100,000 km of blood vessels, with diameters ranging from a few millimeters in the artery to just a few micrometers in the capillaries, and blood flow rates ranging from a few tens of centimeters per second to a few millimeters per second. Although vascular networks present great challenges, due to various environmental conditions, they are of special interest in medical microrobotics since they allow navigable agents to be delivered anywhere within the body. Controlled endovascular navigation would allow targeted surgical, diagnostic, and therapeutic interventions. In cancer therapy, for instance, although many of the most deadly cancers are initially located in a single region, modern therapies such as chemotherapy continue to inject excessive amounts of toxic agents thecirculate systematically throughout the vascular network. In general, only a tiny fraction of the drug reaches the treatment region [1]. Even the level of targeting achieved by agents with special coatings to enhance tumor cell specificity is far from optimal when they are injected systematically in the vascular network. Since the therapeutics do not discriminate between cancerous and healthy cells, systemic circulation of these agents must be avoided to eliminate, or at least minimize, secondary toxicity that affects healthy organs.
38 citations
TL;DR: In this article, the authors present a method to control motion and position at length scales down to the size of a single atom, often referred to as nanopositioning, which is a key enabling tool for many applications.
Abstract: Since its birth in the 1980s, nanotechnology has significantly advanced our understanding and control of physical processes on the nanometer and subnanometer scale. Manipulation and interrogation of matter on these length scales have become indispensable in various fields of engineering and science and have been instrumental in some of the most exciting scientific and engineering breakthroughs of the past decades. Application areas include scanning probe microscopy (SPM) [1], data storage [2], and semiconductor device fabrication [3]. In all these applications, control of motion and position at length scales down to the size of a single atom, often referred to as nanopositioning, is a key enabling tool.
TL;DR: In this article, the authors used the extended Kalman filter (EKF) and the iterated EKF (IEKF), as well as the unscented KF and the particle filter (PF) to estimate hidden system states based on sensor data.
Abstract: Dynamic filters can provide powerful means to estimate hidden system states based on sensor data. For linear problems with Gaussian noise, the Kalman filter is the known optimal solution and has been available for a long time [1], [2]. Exact optimal solutions are rarely available for nonlinear problems, and the user typically selects from a variety of approximate techniques. These techniques include the traditional extended Kalman filter (EKF) [3]?[5], the iterated EKF (IEKF) [4], the unscented Kalman filter (UKF) [5]?[7], the particle filter (PF) [5], [8], [9], and the Gaussian mixture filter (GMF) [5], [10]?[12]. The EKF is widely used but is known to have degraded accuracy, or even to lose stability, for certain problems [5], [13], [14].
TL;DR: An overview of the atomic force microscope and its three main modes of operation is provided in this paper, with a focus on the tapping mode of operation and the challenges associated with obtaining high-speed images with a tappingmode AFM while minimizing image artifacts are outlined and control techniques that have been developed to overcome these challenges are reviewed.
Abstract: The atomic force microscope (AFM) [1] is a mechanical microscope capable of producing three-dimensional images of a wide variety of sample surfaces with nanometer precision in air, vacuum, or liquid environments. This article provides an overview of the AFM and its three main modes of operation, with a focus on the tapping mode of operation. The challenges associated with obtaining high-speed images with a tapping-mode AFM while minimizing image artifacts are outlined and control techniques that have been developed to overcome these challenges are reviewed.
TL;DR: It is a tough job to attract the attention of students, especially at the undergraduate level, to a technical subject and motivate learning within a limited time with the aid of in-class experiments, laboratory practice, and newly emerging advances in technology.
Abstract: As technology is evolving rapidly, the consumers of education systems, namely students, are exposed to more visual and audio media. Advertisements, computer games, movies, and all types of digital media are doing their best to attract young people's attention using the latest technologies. The question of whether or not this situation is beneficial for students is not discussed here. However, it is of vital importance to recognize the challenge that this situation poses for teachers. It is a tough job to attract the attention of students, especially at the undergraduate level, to a technical subject and motivate learning within a limited time. The control courses should also be logical, practical, up to date, and insightful. These objectives are best achieved with the aid of in-class experiments, laboratory practice, and newly emerging advances in technology.
TL;DR: In 2013, I taught a massive open online course (MOOC) called Control of Mobile Robots (COMR) to over 40,000 students worldwide as mentioned in this paper, where upper-level engineering classes were virtually absent from all the major MOOC content providers(Udacity, Coursera, edX).
Abstract: During the spring of 2013, I taught a massive open online course (MOOC), Control of Mobile Robots, to over 40,000 students worldwide. Online resources for higher education have received significant attention during the last year, but upper-level engineering classes have been virtually absent from all the major MOOC content providers(Udacity, Coursera, edX).
TL;DR: In this paper, the authors provide a tutorial on the development of a complete and systematic optimal and robust control theory for SISO systems using only preclassical tools growing out of the Routh stability test and the polynomial Diophantine equation.
Abstract: This article provides a tutorial on the development of a complete and systematic optimal and robust control theory for SISO systems using only preclassical tools growing out of the Routh stability test and the polynomial Diophantine equation. The presented analysis problems are the computations of signal and system energy (two-norm) and system resonance peak (∞-norm). The presented synthesis problems are optimal transient stabilization (linear quadratic Gaussian control) and suboptimal and optimal robust stabilization (H∞-control). Our experience indicates that these materials are well suited for undergraduate teaching.
TL;DR: The discontinuous conduction mode (DCM) arises when the ripple, that is, sustained oscillations of small amplitude, is large enough to cause the polarity of the signal (current or voltage) applied to the switch to reverse as mentioned in this paper.
Abstract: Ideal switches in power converters are typically implemented using unidirectional semiconductor devices that may lead to a new operation mode generically called discontinuous conduction mode (DCM). The DCM arises when the ripple, that is, sustained oscillations of small amplitude, is large enough to cause the polarity of the signal (current or voltage) applied to the switch to reverse. Due to the presence of diodes, switches are assumed to operate unidirectionally, but in DCM this unidirectionality assumption is violated. In classicalconverter topologies, DCM appears very frequently in low load operating modes. More interestingly, to achieve high performance some new converters are purposely designed to operate all the time in DCM [1].
TL;DR: Drop-on-demand (DoD) ink-jet printing as discussed by the authors is an efficient technology for depositing picoliter drops on various printing surfaces, which is compatible with various liquids and does not require contacting the printing media.
Abstract: Drop-on-demand (DoD) ink-jet printing is an efficient technology for depositing picoliter drops on various printing surfaces. DoD technology is compatible with various liquids and does not require contacting the printing media. DoD inkjet printing combines several advantages including high speed, quiet operation, and compatibility with a variety of printing surfaces. Moreover, DoD printing can make patterns without any additional lithographic process. Ink-jet printing can reduce the number of processing steps compared to conventional patterning processes, which results in a lower production cost. Therefore, DoD ink-jet technology is applied in many engineering and scientific applications (see Figure 1), such as the formation of the conductive tracks for printed circuit boards, color filters in flat panel displays and plasma displays, polymer light-emitting diode displays, organic transistors, and the construction of DNA microarrays [1]-[5].
TL;DR: Atomic force microscopy (AFM) was invented in 1986 by using a compliant flexure probe, such as a microcantilever beam with a sharp tip at one end as discussed by the authors.
Abstract: Atomic force microscopy (AFM) was invented in 1986 [1]. By using a compliant flexure probe, such as a microcantilever beam with a sharp tip at one end, the interaction forces between atoms on the probe-tip and atoms on the material surface can be measured (see Figure 1). Since its invention, the simple strategy of using a beam with a sharp tip is now being employed to measure many diverse properties of matter at the nanometer scale including electrical, magnetic, chemical, and mechanical properties [2]. Many different operational modes have evolved that have demonstrated the versatility of the basic underlying principle [3]. AFM has led to many seminal insights in science such as obtained in the recent imaging of pentacene molecules with subatomic resolution [4].
TL;DR: In many cases, the laboratory courses are not taken in the same semester as the lecture courses, preventing students from practicing the concepts learned in the lecture in a timely manner as discussed by the authors.
Abstract: Most electrical and mechanical engineering curricula include courses in controls and mechatronics, with mechanical engineering curricula also including system dynamics and vibrations courses. The laboratory component for these courses is often limited and involves using a limited number of experimental setups. At many institutions, the laboratories associated with these courses are not taken in the same semester, preventing students from practicing the concepts learned in the lecture in a timely manner. Even in laboratory courses that are offered in the same semester as the lecture courses, in many cases it is not possible to synchronize the concepts covered in the lecture with the laboratory exercises since there are usually only a few lab setups for each experiment.
TL;DR: The Second Workshop on Dynamics and Control of Micro-and Nanoscale Systems as discussed by the authors was held at the University of Newcastle, Australia, in February 2012, with a focus on dynamic models of these systems.
Abstract: The articles in this special issue of IEEE Control Systems Magazine are selected from the papers presented at the Second Workshop on Dynamics and Control of Micro- and Nanoscale Systems, which was held at the University of Newcastle, Australia, in February 2012. A report on the workshop appeared in the December 2012 issue of this magazine [1]. Control is a critical technology for emerging micro- and nanoscale systems. Control at such small scales is difficult. These systems tend to have very fast dynamics, which makes control implementation a challenging task for the control engineer. Often significant uncertainty is associated with the dynamic models of these systems, which can also be nonlinear and time varying. Furthermore, sensing at such small scales is a demanding task, and sensor noise often is a key concern. The problems faced by control engineers at the micro- and nanoscales are therefore among the most challenging in the field.
TL;DR: In this paper, a model of chemical and biochemical reaction networks derived using the law of mass action has the form x = Sv(k,x), (1) where x is a vector of concentrations, S is the stoichiometric matrix, and v is the vector of rate expressions formed by multivariate polynomials with real coefficients k.
Abstract: Many systems can be represented using polynomial differential equations, particularly in process control, biotechnology, and systems biology [1], [2]. For example, models of chemical and biochemical reaction networks derived using the law of mass action have the form x = Sv(k,x), (1) where x is a vector of concentrations, S is the stoichiometric matrix, and v is a vector of rate expressions formed by multivariate polynomials with real coefficients k . Furthermore, a model containing nonpolynomial nonlinearities can be approximated by such polynomial models as explained in "Model Approximation". The primary aims of differential algebra (DALG) are to study, compute, and structurally describe the solution of a system of polynomial differential equations,f (x,x, ...,x(k)) =0, (2) where f is a polynomial [3]-[6]. Although, in many instances, it may be impossible to symbolically compute the solutions, or these solutions may be difficult to handle due to their size, it is still useful to be able to study and structurally describe the solutions. Often, understanding properties of the solution space and consequently of the equations is all that is required for analysis and control design.
TL;DR: A nonlinear measurement-based approach is presented here to aid in the teaching of linearization and is illustrated by measuring the nonlinearity of the cart-pole system, an example commonly used in control education.
Abstract: The first undergraduate control course is usually on automatic control theory. Correctly understanding the concepts in that course has far-reaching implications for students. Linearization is a standard topic covered in this introductory course. A nonlinear measurement-based approach is presented here to aid in the teaching of linearization. The pedagogical objective is to help students understand the concept of the neighborhood of linearization. The pedagogical approach is illustrated by measuring the nonlinearity of the cart-pole system, an example commonly used in control education. Drawing on student surveys in two consecutive academic years, we recommend combining demonstration software visualization with relevant mathematic introduction.
TL;DR: In the last 20 years or so, large monetary prizes to recognize major engineering accomplishments have been created in specific countries, but such prizes have not had the same gravitas as the Nobel Prize as discussed by the authors.
Abstract: A fact that does not appear to be well known is that the Nobel Prize has recognized some engineering accomplishments, including an accomplishment in control engineering in 1912 when Nils Gustaf Dalen received the Nobel Prize in Physics for his "invention of automatic regulators for use in conjunction with gas accumulators for illuminating lighthouses and buoys." In the last 20 years or so, large monetary prizes to recognize major engineering accomplishments have been created in specific countries, but such prizes have not had the same gravitas as the Nobel Prize - partly because the prizes are newer, partly because many of the prizes are restricted to people from one country, and partly because the recipients are often scientists rather than engineers. For example, the recipients of one of the two large U.S. engineering prizes are typically biochemists, biologists, or medical doctors rather than engineers - the author feels this practice obscures the distinction between science and engineering rather than better educating the public on the value of engineering. One engineering-related international prize is the Kyoto Prize in Advanced Technology, with past recipients including some engineers such as Rudolf Emil Kalman, but the prize is not focused on engineering per se and is still largely awarded to scientists.
TL;DR: A large proportion of control problems involve the control of fluids, such as coaxing fluids to moving into desired spatial positions or acting as a medium for moving the positions of solid objects into desired positions or orientations as discussed by the authors.
Abstract: A large proportion of control problems involve the control of fluids, such as coaxing fluids to moving into desired spatial positions or acting as a medium for moving the positions of solid objects into desired spatial positions or orientations. Such fluid control problems are ubiquitous in a wide range of applications including in the process industries, nuclear reactors, biological systems, marine vehicles, and aeronautics. This issue of CSM is devoted to various kinds of fluid control problems.
TL;DR: In this article, the authors discuss the role and value of professional societies and why they should be a part of them, and propose a simple answer: belonging to a society means that you can belong to a community that suits you, and this expands the horizon of your life.
Abstract: The author would like to share some thoughts on the role and value of our very Society, the CSS. He poses a question: "What is the value of a professional society, and why do we wish to belong to it?" Being a member of a professional society like the CSS has many advantages. You can get a member discount; have a subscription to journals, which is handy; submit a paper; attend a conference; meet people, etc., etc. But as argued here, these may not be entirely decisive factors by themselves. His simple answer is that belonging to a society means that you can belong to a community that suits you, and this expands the horizon of your life. Is this answer simple? Yes. Is this answer too simplistic? Maybe. But I think this is an important aspect.
TL;DR: The range of mathematical techniques relevant to at least one branch of control engineering is large and includes multivariable calculus, ordinary and partial differential equations, real and complex analysis, linear algebra, multivariability statistics, convex optimization, functional analysis, and differential geometry.
Abstract: How can mathematics courses be taught so as to be more effective for the training of control engineers? Without doubt, the range of mathematical techniques relevant to at least one branch of control engineering is large and includes multivariable calculus, ordinary and partial differential equations, real and complex analysis, linear algebra, multivariable statistics, convex optimization, functional analysis, and differential geometry. To be effective in applications, a control engineer should also be versed in at least one other engineering discipline (such as electrical, mechanical, or aeronautical) as an understanding of a system is required before an effective control system can be designed. A control engineer should also be trained in systems and control problems and techniques, such as model identification, experimental design, fault detection and diagnosis, dynamic optimization, model predictive control, robust control, and nonlinear control. Collectively, the number of courses needed to cover all of these topics would be too high to fit into one curriculum, or even two curricula, which means that most control engineers take courses in only some of these topics.