Desired Point Research Articles

Switching Rule Design for Switched Dynamic Systems With Affine Vector Fields

In this paper, we propose a method for designing switching rules that drive the state of the switched dynamic system to a desired equilibrium point. The method deals with the class of switched systems where each mode of operation is represented by a dynamical system with an affine vector field. The results are given in terms of linear matrix inequalities and they guarantee global asymptotic stability of the tracking error dynamics. Switching rules based on complete and partial state measurements are proposed. The case of uncertain polytopic systems is also considered and a numerical example illustrates the approach.

Pinning Stabilization of Linearly Coupled Stochastic Neural Networks via Minimum Number of Controllers

Pinning stabilization problem of linearly coupled stochastic neural networks (LCSNNs) is studied in this paper. A minimum number of controllers are used to force the LCSNNs to the desired equilibrium point by fully utilizing the structure of the network. In order to pinning control the LCSNNs to a certain desired state, only one controller is required for strongly connected network topology, and m controllers, which will be shown to be the minimum number, are needed for LCSNNs with m -reducible coupling matrix. The isolate node of the LCSNNs can be stable, periodic, or even chaotic. The coupling Laplacian matrix of the LCSNNs can be symmetric irreducible, asymmetric irreducible, or m-reducible, which means that the network topology can be strongly connected, weakly connected, or even unconnected. There is no constraint on the network topology. Some criteria are derived to judge whether the LCSNNs can be controlled in mean square by using designed controllers. The given criteria are expressed in terms of strict linear matrix inequalities, which can be easily checked by resorting to recently developed algorithm. Moreover, numerical examples including small-world and scale-free networks are also given to demonstrate that our theoretical results are valid and efficient for large systems.

A test points selection method for analog fault dictionary techniques

The problem of test point selection is important in the area of fault diagnosis and circuit testing. In this paper, the problem of near optimum test points set selection for analog fault dictionary is considered. This problem is formulated as a depth-first graph search problem. So the test points selection progress is transformed to a graph node expanding progress. The graph node construction method and node expanding procedure are given also. The proposed graph search method guarantee a maximum information increase of S opt by adding a test point to S opt each time, where S opt is the desired test points set used on the path from current node to root node. So a global minimum test points set can be more likely achieved than other methods. The results of statistical experiments indicate that the proposed method more accurately finds the global minimum set of test points without increasing time complexity; therefore, it is a good solution to minimize the size of test points set.

Safe‐steering of batch process systems

AbstractThis work considers the problem of controlling batch processes to achieve a desired final product quality subject to input constraints and faults in the control actuators. Specifically, faults are considered that cannot be handled via robust control approaches, and preclude the ability to reach the desired end‐point, necessitating fault‐rectification. A safe‐steering framework is developed to address the problem of determining how to utilize the functioning inputs during fault rectification to ensure that after fault‐rectification, the desired product properties can be reached upon batch termination. To this end, first a novel reverse‐time reachability region (we define the reverse time reachability region as the set of states from where the desired end point can be reached by batch termination) based MPC is formulated that reduces online computations, as well as provides a useful tool for handling faults. Next, a safe‐steering framework is developed that utilizes the reverse‐time reachability region based MPC in steering the state trajectory during fault rectification to enable (upon fault recovery) the achieving of the desired end point properties by batch termination. The proposed controller and safe‐steering framework are illustrated using a fed‐batch process example. © 2009 American Institute of Chemical Engineers AIChE J, 2009

Bacteriolytic activity of the alternative pathway of complement differs kinetically from the classical pathway

The interaction between bacterial cells and activated complement components as a kinetic biological event is described. The bacteriolytic activity of complement in human and fish serum was assayed by measuring the decrease of bioluminescence of Escherichia coli transformed with lux genes. From the kinetic curves, the bacteriolytic CB 50- and AB 50-units were derived at any desired time point. It was observed that these values were irregular but decreased as a function of incubation time, and reached equal values during prolonged incubation, suggesting that the difference between the classical and alternative pathway activity is kinetic. From the kinetic curves, entirely new parameters could be derived: rate of the activation phase, rate of killing by the lytic phase and rate of killing by the entire pathway in undiluted serum. The rates of human and fish classical pathway were about five and two times higher than those of the alternative pathway respectively.

Almost global stabilization of fully-actuated rigid bodies

This paper addresses the problem of stabilizing a fully-actuated rigid body. The problem is formulated by considering the natural configuration space for rigid bodies, the Special Euclidean group SE(3). The proposed solution consists of a landmark-based controller for force and torque actuation that guarantees almost global asymptotic stability of the desired equilibrium point. As such the equilibrium point is asymptotically stable and only a nowhere dense set of measure zero lies outside its region of attraction. The controller uses velocity measurements and the position coordinates of a collection of landmarks fixed in the environment. As an additional feature, the control law is designed so as to verify prescribed bounds on the actuation.

Online Walking Control System for Humanoids with Short Cycle Pattern Generation

The present paper presents an online walking control system that frequently generates and updates dynamically stable motion patterns with a cycle time of 20 ms. We show that frequently updating the motion pattern contributes to maintaining long-term balance while performing online walking control. In addition, the system enables a robot to respond quickly to changes in the commanded walking direction. Using preview control theory, we generate dynamically stable walking patterns. We propose a method to adjust the future desired zero moment point (ZMP) by modifying the foot landing position in order to maintain the dynamic balance of the generated motion pattern. This technique can be used to filter input commands that would result in sudden changes to the foot landing position, which would result in dynamic instability. The method is also used to compensate for errors between the actual and desired ZMP due to disturbances encountered while walking. We also present an extension of the short cycle pattern generation method that can accommodate external forces measured online. Experimental results for activities such as pushing a table are demonstrated on the full-size humanoid HRP-2 to evaluate the performance of the proposed walking control system.

펙인홀 작업을 위한 임피던스 제어 기반의 직접교시 및 재현 알고리즘

Industrial manipulators have been mostly used in large companies such as automakers and electronics companies. In recent years, however, demands for industrial manipulators from small and medium-sized enterprises are on the increase because of shortage of manpower and high wages. Since these companies cannot hire robot engineers for operation and programming of a robot, intuitive teaching and playback techniques of a robot manipulator should replace the robot programming which requires substantial knowledge of a robot. This paper proposes an intuitive teaching and playback algorithm used in assembly tasks. An operator can directly teach the robot by grasping the end-effector and moving it to the desired point in the teaching phase. The 6 axis force/torque sensor attached to the manipulator end-effector is used to sense the human intention in teaching the robot. After this teaching phase, a robot can track the target position or trajectory accurately in the playback phase. When the robot contacts the environment during the teaching and playback phases, impedance control is conducted to make the contact task stable. Peg-in-hole experiments are selected to validate the proposed algorithm since this task can describe the important features of various assembly tasks which require both accurate position and force control. It is shown that the proposed teaching and playback algorithm provides high positioning accuracy and stable contact tasks.

The Impact of Innovation on Employment in Small and Medium Enterprises with Different Growth Rates

Summary This article examines the impact of innovation on employment growth in innovating small and medium enterprises. In contrast to existing studies, which typically use the least squares estimation technique, quantile regressions were carried out to analyse the data. This method allows one to examine the effects of innovation at any desired point on the distribution function - for example, in firms experiencing positive or negative growth - providing a more complete picture of the relationship between innovation and employment growth than the standard method of viewing deviations in the average effect. The key finding of the study is that innovation has a positive effect on employment in both growing and shrinking small and medium enterprises. In addition, innovation has a much stronger impact on employee headcounts in companies that are already experiencing strong growth than in their slower growing or shrinking counterparts. When differentiating between product and process innovations, the analysis shows that the introduction of new or improved processes has a larger impact on employment than product innovations. Thus, positive employment effects of innovations are not restricted to narrow segments of the economy. Economic policy aimed at bolstering the innovative strength of firms is thus a strong encouragement to employment on a broad basis.

Grid method for computation of generalized spheroidal wave functions based on discrete variable representation

We present an efficient and accurate grid method for computations of eigenvalues and eigenfunctions of the generalized spheroidal wave equation. Different from previous studies, our method is based on the expansion of the spheroidal wave function by discrete-variable-representation basis functions constructed from the associated Legendre polynomials. The differential operator can be expressed analytically on the grid points, which are the zeros of the associated Legendre polynomials. The resultant potential matrix is simply diagonal and evaluated directly on the same grid. The corresponding differential equation is thus converted to an eigenvalue problem of a small matrix, whose eigenvalues and eigenvectors are converged very fast. The wave functions can then be evaluated accurately at any desired point from the expansion formula with the computed eigenvectors. Compared to previous methods, our method is direct and efficient for any parameter c , either small or large.

To Burst or Circuit Switch?

We develop, analyze and then numerically compare performance models of a fast-adapting and centrally controlled form of optical circuit switching (OCS) with a conservative form of optical burst switching (OBS). For the first time, we consider a unified model comprising both: edge buffers at which arriving packets are aggregated and enqueued according to a vacation-type service discipline with nondeterministic set-up times, together with a core network comprising switches arbitrarily interconnected via fibers to allow transmission of packets from an edge buffer to their desired egress point through use of a dynamic signaling process to establish a lightpath, and in the case of OCS, also acknowledge its establishment. As such, edge buffers dynamically issue requests for wavelength capacity via a two or one-way reservation signaling process. Previously analyzed models of OCS and OBS have either been for a stand-alone edge buffer or a core network without edge buffering. We compare OCS with OBS in terms of packet blocking probability due to edge buffer overflow and blocking at switches in the case of OBS; mean packet queueing delay at edge buffers; and, wavelength capacity utilization. Also for the first time, we derive the exact blocking probability for a multi-hop stand-alone OBS route, assuming Kleinrock's independence, which is not simply a matter of summing the stationary distribution of an appropriate Markov process over all blocking states, as shown to be the case for an OCS route.

Explore Clinical Problems by Wearing Different Hats

In a previous column (Levin, 2008), I discussed the need to describe a practice problem using both background literature and internal organizational data in order to determine whether a problem really exists and, if it does, to describe its importance to the agency and in the broader health care context. The question I posed was this: Is this really a problem that needs our attention or is it simply an infrequent occurrence or outlier that one or two clinicians thought might be an (p. 5). I gave an example of how to collect internal data to substantiate the problem. One of my colleagues, Dr. Gina Myers, shared with me at a recent meeting another way of helping clinicians hone a clinical practice problem using the Six Thinking Hats method described by de Bono (1999), which is described in this column. The Six Thinking Hats approach provides a structure to examine a problem by efficiently exploring all sides or aspects of an issue. The hats are easy to use and allow an individual or group to organize and explore a large and seemingly overwhelming situation without much effort. This method can foster a sense of teamwork and open-mindedness because each member of a team has an opportunity to put on each thinking hat and thus view a problem from multiple frames of reference. THE SIX THINKING HATS The Six Thinking Hats, or thinking styles, are the following: 1. The White Hat is neutral and objective and is concerned only with data (Just the facts, ma'am). Wearing this hat, the team or group would describe findings from the literature and internal evidence from the organization regarding the clinical problem or issue. Clinical expertise can also be included here as well as patient values and preferences from a population-based, culturally competent perspective. 2. The Red Hat symbolizes the emotional view and provides a vehicle for us to address our own preconceived notions or feelings. 3. The Yellow Hat is sunny and positive. When wearing this hat, one focuses on the benefits or pluses of a decision. 4. The Black Hat is the devil's advocate. Although some may consider this hat negative and gloomy, paying attention to potential negative consequences of a decision can be important. 5. The Green Hat is associated with fertile growth, creativity, and new ideas. With this hat, clinical expertise and innovative ideas can be discussed. 6. The Blue Hat is cool and calm and helps to organize discussions and orchestrate decision making. The Blue Hat should be worn at least at the beginning and end of a discussion. The group facilitator often wears this hat while simultaneously wearing the others in turn. The first Blue Hat will determine why a group is together, what is being looked at, and the desired end point. Roles, such as timekeeper or scribe, may be assigned at this time to keep the discussion organized. As the last hat, blue also gives an opportunity to review achievements and summarize the group's conclusions. It is here that the next action steps are determined. USING THIS METHOD How can this method help us decide on the clinical problems to be studied? First, identify a clinical situation you want to address. The situation may be a burning clinical question, a process or system issue that is not working well, or the desire to enhance outcomes. …

Feedback Controller Design for the Four-Tank Process using Dissipative Hamiltonian Realization

This paper considers the problem of stabilizing the quadruple-tank process using an approximate dissipative Hamiltonian realization. The proposed approach consists in canceling by feedback the deviation of the system from a Hamiltonian system. First, we obtain a characteristic one-form for the system by taking the interior product of a non vanishing two-form with respect to the controlled vector field. We then construct a homotopy operator on a star-shaped region centered at a desired equilibrium point. The dynamics of the system is then decomposed into an exact part and an anti-exact one. The exact part is generated by a potential, hence stability of this part is guaranteed using the generating potential as a Lyapunov function. The stabilizing feedback controller is designed by canceling the anti-exact part of the characteristic one-form. Application of the resulting controller is illustrated by numerical simulations.

Output-feedback control for stabilization on [formula omitted

This paper addresses the problem of stabilizing systems that evolve on SE ( 3 ) . The proposed solution consists of an output-feedback controller that guarantees almost global asymptotic stability of the desired equilibrium point, in the sense that the equilibrium point is stable, and we have convergence for all initial conditions, except for those in a nowhere dense set of measure zero. The output vector is formed by the position coordinates of a collection of landmarks fixed in the environment. The resulting closed-loop system exhibits the following properties: (i) the position and orientation subsystems are decoupled, (ii) the position error is globally exponentially stable, and (iii) the orientation error is almost globally exponentially stable. Results are also provided, that allow one to select landmark configurations, so as to control how the position and orientation of the rigid body converge to their final equilibrium values.

Two‐stage design for dose‐finding that accounts for both efficacy and safety

We introduce a two-stage design for dose-finding in the context of Phase I/II studies, where two binary correlated endpoints are available, for instance, one for efficacy and one for toxicity. The bivariate probit model is used as a working model for the dose-response relationship. Given a 'desirable point' for the marginal probabilities of efficacy and toxicity, the goal is to find the target dose that is 'closest' to the desirable point. The criterion of optimality (objective function) is the variance of the estimator for that dose. Optimal experimental design methodology is used to construct efficient dose allocation procedures that treat patients in the study at doses that are both safe and efficacious.

Hybrid formulation and solution for transient conjugated conduction–external convection

This work presents a hybrid numerical–analytical solution for transient laminar forced convection over flat plates of non-negligible thickness, subjected to arbitrary time variations of applied wall heat flux at the fluid–solid interface. This conjugated conduction–convection problem is first reformulated through the employment of the coupled integral equations approach (CIEA) to simplify the heat conduction problem on the plate by averaging the related energy equation in the transversal direction. As a result, an improved lumped partial differential formulation for the transversally averaged wall temperature is obtained, while a third kind boundary condition is achieved for the fluid from the heat balance at the solid–fluid interface. From the available steady velocity distributions, a hybrid numerical–analytical solution based on the generalized integral transform technique (GITT), under its partial transformation mode, is then proposed, combined with the method of lines implemented in the Mathematica 5.2 routine NDSolve. The interface heat flux partitions and heat transfer coefficients are readily determined from the wall temperature distributions, as well as the temperature values at any desired point within the fluid. A few test cases for different materials and wall thicknesses are defined to allow for a physical interpretation of the wall participation effect in contrast with the simplified model without conjugation.

Controlling the onset of Hopf bifurcation in the Hodgkin-Huxley model

It is a challenging problem to establish safe and simple therapeutic methods for various complicated diseases of the nervous system, particularly dynamical diseases such as epilepsy, Alzheimer's disease, and Parkinson's disease. From the viewpoint of nonlinear dynamical systems, a dynamical disease can be considered to be caused by a bifurcation induced by a change in the values of one or more regulating parameter. Therefore, the theory of bifurcation control may have potential applications in the diagnosis and therapy of dynamical diseases. In this study, we employ a washout filter-aided dynamic feedback controller to control the onset of Hopf bifurcation in the Hodgkin-Huxley (HH) model. Specifically, by the control scheme, we can move the Hopf bifurcation to a desired point irrespective of whether the corresponding steady state is stable or unstable. In other words, we are able to advance or delay the Hopf bifurcation, so as to prevent it from occurring in a certain range of the externally applied current. Moreover, we can control the criticality of the bifurcation and regulate the oscillation amplitude of the bifurcated limit cycle. In the controller, there are only two terms: the linear term and the nonlinear cubic term. We show that while the former determines the location of the Hopf bifurcation, the latter regulates the criticality of the Hopf bifurcation. According to the conditions of the occurrence of Hopf bifurcation and the bifurcation stability coefficient, we can analytically deduce the linear term and the nonlinear cubic term, respectively. In addition, we also show that mixed-mode oscillations (MMOs), featuring slow action potential generation, which are frequently observed in both experiments and models of chemical and biological systems, appear in the controlled HH model. It is well known that slow firing rates in single neuron models could be achieved only by type-I neurons. However, the controlled HH model is still classified as a type-II neuron, as is the original HH model. We explain that the occurrence of MMOs can be related to the presence of the canard explosion where a small oscillation grows through a sequence of canard cycles to a relaxation oscillation as the control parameter moves through an interval of exponentially small width.

Comprehensive evaluation on the heating capacities of four typical whole body hyperthermia strategies via compartmental model

The whole body hyperthermia (WBH) is being regarded as a very promising way of efficiently treating patients with tumors already distributed throughout the human body. However, quite a few important issues still remain unclear, some of which are how much energy can be deposited into human body or how long will it take for a patient’s body core temperature to rise from its normal to the desired point. Aiming to provide a general background for tackling the complex heat transfer behavior throughout the whole human body during a WBH treatment, we propose in this paper to adopt a compartmental model for a comprehensive evaluation of several existing typical WBH methods. The heating performance of four heating strategies such as contact-heating-based WBH (CWBH), radiative- heating-based WBH (RWBH), extracorporeal circulative-heating-enabled WBH (EWBH) as well as interventional WBH (IWBH) were compared and evaluated. The characteristics of different WBH methods were assessed in detail from the engineering perspective. Further, the effect of the thermal regulation mechanism and brain cooling upon body temperature response during WBH was investigated. Specially, this research explained for the first time the reason why intravascular heating strategies could have a higher heating efficiency in raising body core temperature than that of the heating from outside. This study would help probe into the complex behavior of the temperature response of the human body subject to various WBH. The theoretical model and calculation method could serve as a valuable guidance for future tumor treatment planning.

Design of Fuzzy Logic Controlled Thermoelectric Renal Hypothermia System

In this study, a fuzzy logic controlled Thermoelectric Renal Hypothermia System has been implemented for use in renal surgery. Herein, temperature control of the Thermoelectric Renal Hypothermia System has been carried out via a Fuzzy Logic Controller. Since the most important issues in long‐lasting parenchymatous renal surgery are to provide an operation medium that is free of blood and to prevent renal dysfunction in the postoperative period, control of the temperature has become very important in renal surgery. The final result is seriously affected by changes in temperature; therefore, it is necessary to reach some desired temperature points quickly and to avoid a large overshoot. The PIC16F877 microcontroller has been used as the fuzzy logic controller. The designed system is energy saving, decreases temperature swings to a minimum level; so, it offers efficient results. Also, the designed system takes into consideration appropriate parameters that can reflect very small changes in the kidney and can be applied to people safely in the future.

Robust control of chaos in the Lorenz system with the variable structure control approach

This paper is concerned with the robust control for a class of the uncertain Lorenz system subject to sector nonlinear input. Based on rigorous mathematical analysis, the proposed variable structure controller can drive the system state exactly to a class of a specific point or in the predictable neighborhood of an arbitrary desired point in the state space even with mismatch uncertainties. Moreover, the controller ensures that one of the error components can approach zero as time approaches infinity. Finally, numerical simulation results show the effectiveness of our work.