bluuebunny/crossref_metadata_2025 huggingface dataset:
Myometrial mechanoadaptation during pregnancy: implications for smooth muscle plasticity and remodelling
Authors: Wu X. , Morgan K. G. , Jones C. J. , Tribe R. M. , Taggart M. J.
Published: March 2008

The smooth muscle of the uterus during pregnancy presents a unique circumstance of physiological mechanotransduction as the tissue remodels in response to stretches imposed by the growing foetus(es), yet the nature of the molecular and functional adaptations remain unresolved. We studied, in myometrium isolated from non‐pregnant (NP) and pregnant mice, the active and passive length–tension curves by myography and the expression and activation by immunoblotting of focal adhesion‐related proteins known in other systems to participate in mechanosensing and mechanotransduction. In situ uterine mass correlated with pup number and weight throughout pregnancy. In vitro myometrial active, and passive, length‐tension curves shifted significantly to the right during pregnancy indicative of altered mechanosensitivity; at term, maximum active tension was generated following 3.94 ± 0.33‐fold stretch beyond slack length compared to 1.91 ± 0.12‐fold for NP mice. Moreover, mechanotransduction was altered during pregnancy as evidenced by the progressive increase in absolute force production at each optimal stretch. Pregnancy was concomitantly associated with an increased expression of the dense plaque‐associated proteins FAK and paxillin, and elevated activation of FAK, paxillin, c‐Src and extracellular signal‐regulated kinase (ERK1/2) which reversed 1 day post‐partum. Electron microscopy revealed close appositioning of neighbouring myometrial cells across a narrow extracellular cleft adjoining plasmalemmal dense plaques. Collectively, these results suggest a physiological basis of myometrial length adaptation, long known to be a property of many smooth muscles, whereupon plasmalemmal dense plaque proteins serve as molecular signalling and structural platforms contributing to functional (contractile) remodelling in response to chronic stretch.
Neuropsychiatric symptoms in 921 elderly subjects with dementia: a comparison between vascular and neurodegenerative types
Authors: Caputo M. , Monastero R. , Mariani E. , Santucci A. , Mangialasche F. , Camarda R. , Senin U. , Mecocci P.
Published: March 2008

Objective:  i) to describe the neuropsychiatric profile of elderly subjects with dementia by comparing vascular (VaD) and degenerative dementias, i.e. dementia with Lewy bodies (DLB) and Alzheimer’s disease (AD); ii) to assess whether the severity and type of dementia are associated with clinically relevant neuropsychiatric symptoms (CR‐NPS).

Method:  One hundred and thirty‐one out‐patients with VaD, 100 with DLB and 690 with AD were studied. NPS were evaluated by the neuropsychiatric inventory (NPI).

Results:  Vascular dementia had lower total and domain‐specific NPI scores and a lower frequency of CR‐NPS than AD and DLB, for which frequency of CR‐NPS increased significantly with disease severity, particularly in AD. Logistic regression analysis showed that a higher CDR score and a diagnosis of degenerative dementia were independently associated with CR‐NPS.

Conclusion:  Vascular dementia is associated less with CR‐NPS than AD and DLB. Frequency of CR‐NPS increases with disease severity in AD and, to a lesser extent, in DLB.
Topical photodynamic therapy of murine non‐melanoma skin carcinomas with aluminum phthalocyanine chloride and a diode laser: pharmacokinetics, tumor response and cosmetic outcomes
Authors: Kyriazi Maria , Alexandratou Eleni , Yova Dido , Rallis Michail , Trebst Tilmann
Published: March 2008

Background/purpose: Topical photodynamic therapy (PDT) is potentially useful for the treatment of non‐melanoma skin cancer and other skin diseases. We investigated the therapeutic effects of PDT using topical application of aluminum phthalocyanine chloride (AlClPc) and a diode laser emitting at 670 nm in murine non‐melanoma skin carcinomas.

Methods: AlClPc solution (0.7% w/v) was applied to tumors in mice for 1–6 h. The penetration depth and the optimum drug–light interval were assessed using pharmacokinetic studies. Then, PDT was performed on a murine model of non‐melanoma skin cancer using seven different combinations of therapeutic parameters (fluence rate and energy dose).

Results: Pharmacokinetic studies revealed that AlClPc was absorbed 40 times more and penetrated 19 times deeper in tumors than normal skin. PDT using AlClPc (0.7% w/v) and a diode laser (75 mW/cm2, 150 J/cm2) resulted in complete tumor remission in 60% of the mice, excellent cosmetic outcomes and growth retardation of tumors with partial remission.

Conclusions: The results indicate that AlClPc‐PDT is an effective treatment for non‐melanoma skin carcinomas in experimental mouse models.
Cloning and functional analysis of 5′‐upstream region of the Pokemon gene
Authors: Yang Yutao , Zhou Xiaowei , Zhu Xudong , Zhang Chuanfu , Yang Zhixin , Xu Long , Huang Peitang
Published: March 2008

Pokemon, the POK erythroid myeloid ontogenic factor, not only regulates the expression of many genes, but also plays an important role in cell tumorigenesis. To investigate the molecular mechanism regulating expression of the Pokemon gene in humans, its 5′‐upstream region was cloned and analyzed. Transient analysis revealed that the Pokemon promoter is constitutive. Deletion analysis and a DNA decoy assay indicated that the NEG‐U and NEG‐D elements were involved in negative regulation of the Pokemon promoter, whereas the POS‐D element was mainly responsible for its strong activity. Electrophoretic mobility shift assays suggested that the NEG‐U, NEG‐D and POS‐D elements were specifically bound by the nuclear extract from A549 cells in vitro. Mutation analysis demonstrated that cooperation of the NEG‐U and NEG‐D elements led to negative regulation of the Pokemon promoter. Moreover, the NEG‐U and NEG‐D elements needed to be an appropriate distance apart in the Pokemon promoter in order to cooperate. Taken together, our results elucidate the mechanism underlying the regulation of Pokemon gene transcription, and also define a novel regulatory sequence that may be used to decrease expression of the Pokemon gene in cancer gene therapy.
Full‐length prion protein aggregates to amyloid fibrils and spherical particles by distinct pathways
Authors: El Moustaine Driss , Perrier Veronique , Smeller Laszlo , Lange Reinhard , Torrent Joan
Published: March 2008

As limited structural information is available on prion protein (PrP) misfolding and aggregation, a causative link between the specific (supra)molecular structure of PrP and transmissible spongiform encephalopathies remains to be elucidated. In this study, high pressure was utilized, as an approach to perturb protein structure, to characterize different morphological and structural PrP aggregates. It was shown that full‐length recombinant PrP undergoes β‐sheet aggregation on high‐pressure‐induced destabilization. By tuning the physicochemical conditions, the assembly process evolves through two distinct pathways leading to the irreversible formation of spherical particles or amyloid fibrils, respectively. When the PrP aggregation propensity is enhanced, high pressure induces the formation of a partially unfolded aggregated protein, AggHP, which relaxes at ambient pressure to form amorphous aggregates. The latter largely retain the native secondary structure. On prolonged incubation at high pressure, followed by depressurization, AggHP transforms to a monodisperse population of spherical particles of about 20 nm in diameter, characterized by an essentially β‐sheet secondary structure. When the PrP aggregation propensity is decreased, an oligomeric reaction intermediate, IHP, is formed under high pressure. After pressure release, IHP relaxes to the original native structure. However, on prolonged incubation at high pressure and subsequent depressurization, it transforms to amyloid fibrils. Structural evaluation, using optical spectroscopic methods, demonstrates that the conformation adopted by the subfibrillar oligomeric intermediate, IHP, constitutes a necessary prerequisite for the formation of amyloids. The use of high‐pressure perturbation thus provides an insight into the molecular mechanism of the first stages of PrP misfolding into amyloids.
Metrosexuality! Cameron, Brown and the politics of ‘new masculinity’
Authors: Whitehead Stephen
Published: March 2008

Dr Stephen Whitehead argues that in the post‐Blair‐Babe era, a new discourse of masculinity has come to define UK politics, and this is most clearly seen in the behaviour of our two most prominent male politicians…
The crisis in our Critical National Infrastructure
Authors: Norton Jim
Published: March 2008

Professor Jim Norton, a member of ippr's Commission on National Security in the 21st Century, argues that in the drive for economic efficiency we may have neglected the resilience and security of our national infrastructure, with potentially catastrophic results.
Anatomy and ultrastructure of the reproductive organs in Dactylopodola typhle (Gastrotricha: Macrodasyida) and their possible functions in sperm transfer
Authors: Kieneke Alexander , Arbizu Pedro Martínez , Ahlrichs Wilko H.
Published: March 2008

Abstract. The reproductive anatomy of gastrotrichs is well known for several species, especially for the marine taxon Macrodasyida. However, there is little information on the reproductive organs and the modes of mating and sperm transfer in putative basal taxa, which is necessary for accurate reconstruction of the ground pattern of the Gastrotricha. We present the first detailed morphological investigation of the reproductive system of a putative basal gastrotrich, Dactylopodola typhle, using transmission and scanning electron microscopy, histology, and microscopic observations of living specimens. Dactylopodola typhle is a hermaphrodite that possesses paired female and male gonads, an unpaired uterus with an outlet channel that we call the cervix, and an additional accessory reproductive organ, the so‐called caudal organ. We hypothesize that the hollow, secretory caudal organ serves for picking up autospermatozoa (self‐sperm), for spermatophore formation, and finally for transferring the autospermatophore to a mating partner. The allospermatophore (foreign spermatophore) is stored within the uterus where fertilization occurs. We think that the mature and fertilized egg is released through the cervix and the dorsolateral female gonopore, and not by rupture of the body wall. Based on the morphology, we provide a plausible hypothesis for spermatophore formation and transfer in D. typhle. Preliminary phylogenetic considerations indicate that the stem species of Macrodasyida, perhaps that of all Gastrotricha, had paired ovaries and paired testes, an unpaired uterus, and only one accessory reproductive organ.
As the PMI Turns: A Tool for Supply Chain Managers
Authors: Lindsey Matthew D. , Pavur Robert J.
Published: March 2008

Supply chain managers use the PMI, an index of business activity and proxy for the general business cycle, to obtain valuable information important to strategic managerial planning. This research explores a methodology to provide managerial insight into the general business cycle by tracking and forecasting cycle turns in the PMI. A regression model is developed based on inherent cycles in the PMI between 12 and 65 months to forecast turning points for the index and anticipate changes in the business cycle, which is superior to the more commonly used Box‐Jenkins forecasting technique. Strategic planning using this knowledge allows management to optimally adjust long‐term levels of production, inventory, employment and orders as necessary.
Lymphangiectasia in a dog
Authors: GRIFFITHS G. L. , CLARK W. T. , MILLS J. N.
Published: March 2008

Summary. A 5‐year‐old speyed female silky terrier was presented with ascites. Clinical pathology revealed hypoproteinaemia, lymphpaenia, hypocalcaemia and hypocholesterolaemia. Surgical biopsy of the small intestine enabled the diagnosis of intestinal lymphangiectasia to be made.
Incidence of oral complications and application of a preventive protocol in children with acute leukemia
Authors: Levy‐Polack Mariana P. , Sebelli Patricia , Polack Noemi L.
Published: March 2008

This prospective, controlled study was designed to assess the effectiveness of a preventive oral protocol in children receiving antineoplastic treatment for acute lymphoblastic leukemia (ALL). During a 13‐month period, 96 children from one to 16 years of age with a diagnosis of ALL were evaluated. When the study was initiated, 60 patients already undergoing chemotherapy received palliative treatment for complications (Group I). Thirty‐six children (Group II) with newly diagnosed ALL received a daily preventive protocol consisting of: (1) elimination of bacterial plaque; (2) application of a mouthwash with a non‐alcoholic solution of chlorhexidine 0.12% and (3) topical application of lodopovidone, followed by “swish and swallow” with nystatin 500,000 units. Children in both groups were examined every 7 to 14 days by our pediatric dentistry team. We found a significant improvement in oral hygiene (p = 0.001) and a significant decrease in the incidence of mucositis grade 2 (p = 0.0013) and oral candidiasis (p = 0.009) in the Group II children. These findings show that the systematic application of a preventive protocol significantly reduces the incidence of oral complications. The results of this study identify a need to include a pediatric dentist in a multidisciplinary team which provides oral care for cancer patients.
Ontario's Rae Report: Investing in growth
Authors: Cameron David M.
Published: March 2008

“I am urging the provincial government to adopt as a key mission for the province the goal for Ontario to be a leader in learning, and to fund higher education accordingly”

Ontario: A Leader in Learning ‐ Report & Recommendations. By BOB RAE, Advisor to the Premier and the Minister of Training, Colleges and Universities. Toronto: Queen's Printer. 2005. Pp. iii, 124.
Book note Resume de liver
Authors: Smythe Elizabeth
Published: March 2008

Shereen T. Ismael, editor, Globalization: Policies, Challenges and Responses
Public‐service values and ethics: Dead end or strong foundation?
Authors: Heintzman Ralph
Published: March 2008

Abstract: In the Winter 2004 issue of this journal, John Langford pronounced a negative verdict on the concern for public‐service values, which has been a feature of public‐service reform over the past decade. This article reconsiders Langford's arguments. It suggests that public‐service renewal requires ongoing attention to public‐service values but also a widening of perspectives. It is now necessary to give more attention to the organizational, professional and institutional conditions for sound individual behaviour. Renewed attention to public‐service values did not seek to supplant traditional approaches to individual decision‐making but rather to re‐frame them, grounded in the principles without which they cannot make sense of the world. The research literature on values and ethics contradicts the critique's main contentions. The critique is also based on a mistaken premise, false dichotomies, and inadequate and contradictory assumptions about the nature of individual decision‐making. Three points that are useful contributions to the ongoing dialogue on public‐service values and ethics are noted. But an individual perspective must now be augmented by a focus on organizational performance. Far from being a “dead end,” public‐service values remain the strong foundation – the only possible foundation – for the public service of the future.

Sommaire: Le présent article réexamine celui de John Langford, publié dans le numéro d'hiver 2004, dans lequel il prononqait un verdict négatif sur la préoccupation au sujet des valeurs du service public qui a été un élément de la réforme de la fonction publique au cours de la dernière décennie. Une nouvelle attention portée aux valeurs du service public n'a pas cherchéà remplacer les approches traditionnelles concernant la prise de décisions, mais plutôt à les recadrer, à les faire reposer sur des principes sans lesquels le monde n'a pas de sens. La littérature de recherche sur les valeurs et l'éthique conrredit les principales allégations du critique et est également fondée sur des assomptions erronées et contradictoires au sujet de la nature de la prise de décision individuelle. Trois points qui représentent des contributions utiles au dialogue actuel sur les valeurs et l'éthique du service public sont mentionnés. Mais la perspective individuelle doit aussi avoir pour objectif la performance organisarionnelle. Loin d'être une « voie sans issue », les valeurs du service public restent le fondement solide – et en fait le seul fondement possible – du service public de l'avenir.
Optimal Product Portfolio Formulation by Merging Predictive Data Mining With Multilevel Optimization
Authors: Tucker Conrad S. , Kim Harrison M.
Published: March 2008

This paper addresses two important fundamental areas in product family formulation that have recently begun to receive great attention. First is the incorporation of market demand that we address through a data mining approach where realistic customer preference data are translated into performance design targets. Second is product architecture reconfiguration that we model as a dynamic design entity. The dynamic approach to product architecture optimization differs from conventional static approaches in that a product architecture is not fixed at the initial stage of product design, but rather evolves with fluctuations in customer performance preferences. The benefits of direct customer input in product family design will be realized through the cell phone product family example presented in this work. An optimal family of cell phones is created with modularity decisions made analytically at the engineering level that maximize company profit.
Rotor Profile Design for the Twin-Screw Compressor Based on the Normal-Rack Generation Method
Authors: Wu Yu-Ren , Fong Zhang-Hua
Published: March 2008

This paper proposes a method for designing the rotor profiles of twin-screw compressors using a rack defined in the normal plane. All tooth profile segments are explicitly defined as tangent continuous in the normal section to generate a pair of conjugated rotors. Numerical comparisons between the two types of screw rotor tooth profile design, one based on a normal system, the other on an axial system, show the advantages of using the normal-rack generation method (NRGM). Most particularly, this method allows the same hob used for screw rotors to be used to manufacture mating rotors even as the helix angle varies, because in a normal system the circular pitch remains the same. The numerical results also indicate that the rotor tooth thickness generated by the NRGM rack cutter can prevent serious deflection for a variety of helix angles and tooth combinations.
Design of a Linear Controller for Robust Tracking and Model Following
Authors: Hopp T. H. , Schmitendorf W. E.
Published: March 2008

We consider a class of linear systems in which there is time-varying uncertainty. These linear uncertain systems can be divided into two types. Systems in which the structure of the uncertainty satisfies certain matching conditions are called matched, and those systems in which the uncertainty does not satisfy the matching conditions are called mismatched. A linear control law is determined which produces tracking of dynamic inputs. The tracking error does not asymptotically decrease to zero because the systems are uncertain, instead the error is bounded. In the case of matched systems this error bound can be made arbitrarily small, and the system is said to practically track the input. In mismatched systems, the tracking error cannot be made arbitrarily small, and the system is said to ε-track the input. Previously published theory requires nonlinear controllers for practical tracking. Here, we derive a linear feedforward control law. Several examples illustrate the results.
A Method for the Real Time Solution of the Forward Dynamics Problem for Robots Incorporating Friction
Authors: Gogoussis A. , Donath M.
Published: March 2008

A modular and computationally efficient method for solving the forward dynamics problem of robot mechanisms incorporating Coulomb friction is developed. This hybrid approach incorporates both analog and digital components that facilitate real time solutions. Coulomb friction effects associated with both transmissions and bearings are considered. Moreover, the methods accounts for joint flexibility as well as actuator gyroscopic effects. In our approach, the inverse dynamics formulation is used for solving the forward dynamics problem. The positive definiteness property of the inertia matrix of the dynamic equations of motion is exploited by intentionally introducing algebraic loops so that simultaneous algebraic equations are solved without iterations. By resolving these algebraic loops using linear electronics, one avoids the computational burden and time delays associated with purely digital solutions, thus facilitating real time operation. A proof of stability is also presented. The formulation developed here is useful in cases requiring either or both the inverse and forward dynamics solutions typically associated with design and control.
Real Time Measurement for High Frequency Pulsating Flow Rate in a Pipe
Authors: Zhao Tong , Sanada K. , Kitagawa A. , Takenaka T.
Published: March 2008

Two kinds of analog transformation methods for the measurement of high frequency pulsating flow rates in pipe flow are investigated. By use of the methods, the high frequency pulsating flow rates can be obtained by feeding differential pressure or centerline velocity to analog electronic circuits. First, the frequency characteristics of the electronic circuits for the measurement are examined by experiments. Then a criterion for determining the measurement distance of the differential pressure is derived analytically in order to ensure the required accuracy of the measurement when the flow rate is obtained from the differential pressure signal. Both methods are experimented with over a wide range of frequency. The results show that both methods are not only simple and practical, but also very accurate for the measurement of high frequency pulsating flow rates.
Dynamics of Robotic Manipulators With Flexible Links
Authors: Chang Liang-Wey , Hamilton J. F.
Published: March 2008

This paper presents a dynamic model for the robotic manipulators with flexible links by means of the Finite Element Method and Lagrange’s formulation. By the concept of the Equivalent Rigid Link System (ERLS), the generalized coordinates are selected to represent the total motion as a large motion and a small motion. Two sets of coupled nonlinear equations are obtained where the equations representing small motions are linear with respect to the small motion variables. An example is presented to illustrate the importance of the flexibility effects.
On the Accuracy of End-Point Trajectory Tracking for Flexible Arms by Noncausal Inverse Dynamic Solutions
Authors: Moulin H. , Bayo E.
Published: March 2008

The problem of open-loop control of the end-point trajectory of a single-link flexible arm by an inverse dynamic solution is addressed in this paper. A finite element discretization of the system is used to obtain a set of ordinary differential equations describing the motion. Theoretical difficulties pertaining to the inverse problem for flexible structures are exposed, and it is shown that a noncausal solution for the actuating torque enables a tracking of an arbitrary tip displacement with any desired accuracy.
Application of an Adaptive Model Following Control Technique to a Hydraulic Servo System Subjected to Unknown Disturbances
Authors: Yun J. S. , Cho H. S.
Published: March 2008

This paper deals with a position control of hydraulic servo systems subjected to unknown and time-varying external load disturbances. Since hydraulically operated processes are often subjected to unknown disturbances, an adaptive model following control (AMFC) scheme was derived based upon the Liapunov’s Direct Methods which was employed by Monopoli (1981). As an adaptation criterion this method utilizes an ultimate boundary of the uncertain parameters associated with the plant dynamics and the unknown disturbances. The performance of the derived adaptive controller is evaluated through simulation and experimental studies. The results show that the proposed AMFC is fairly insensitive to unknown and time-varying external load disturbances, yielding much better response characteristics, compared with those of a conventional constant PI feedback controller.
A Method of Fault Signature Extraction for Improved Diagnosis
Authors: Chin Hsinyung , Danai Kourosh
Published: March 2008

Efficient extraction of fault signatures from sensory data is a major concern in fault diagnosis. This paper introduces a self-tuning method of fault signature extraction that enhances fault detection, minimizes false alarms, improves diagnosability, and reduces fault signature variability. The proposed method uses a Flagging Unit to convert the processed measurements to binary vectors, and utilizes nonparametric pattern classification techniques to estimate the fault signatures. The performance of the Flagging Unit, which relies on its adaptation algorithms to optimize its performance based upon a sample batch of measurement-fault vectors, is demonstrated in simulation.
The Design and Predicted Performance of a Regenerative System for Testing Positive Displacement Pumps
Authors: Edge K. A. , Harris R. M.
Published: March 2008

Regenerative systems are frequently encountered where positive displacement pumps and motors are to be tested at high pressure levels or for prolonged periods. However, there is little published information regarding the design and performance of these systems. This paper aims to redress this shortfall by developing general relationships applicable to regenerative systems as well as presenting the design of a system for a specific application. The steady running performance of a system has been simulated, and it is shown that the system operates with a good power saving over a wide range of conditions. The dynamic behavior of the system has also been predicted and several areas of caution noted.
Unstabilizability of Linear Unstable Systems With Input Limits
Authors: Ma C. C. H.
Published: March 2008

It is shown that a linear strictly unstable system with actuation limits cannot be stabilized globally, regardless of whatever control methodology is applied. This has important implications for control practices, especially for the control of unstable plants whose dynamics may vary abruptly during operation. It also implies that a feedback controller should be stable by itself, which further aggravates the problem of controlling certain unstable plants in practice.
Computation of Path Constrained Time Optimal Motions With Dynamic Singularities
Authors: Shiller Zvi , Lu Hsueh-Hen
Published: March 2008

An algorithm for computing the time optimal motions of robotic manipulators along specified paths is presented which accounts for singular points and arcs, at which one actuator does not contribute to the acceleration along the path. It is proven that the optimal trajectory is extremal in the acceleration along the path at all times except at singular points and arcs where it maximizes the feasible velocity along the path. This algorithm is robust to path variations unlike the original methods (Bobrow et al., 1985; Shin and McKay, 1984) that fail at singular points. The algorithm is demonstrated for a two-link planar manipulator to produce smooth controls along singular arcs.
Synchronization of Two Motion Control Axes Under Adaptive Feedforward Control
Authors: Tomizuka Masayoshi , Hu Jwu-Sheng , Chiu Tsu-Chih , Kamano Takuya
Published: March 2008

In this paper, motion synchronization of two d-c motors, or motion control axes, under adaptive feedforward control is considered. The adaptive feedforward control system for each axis consists of a proportional feedback controller, an adaptive disturbance compensator and an adaptive feedforward controller. If the two adaptive systems are left uncoupled, a disturbance input applied to one of the two axes will cause a motion error in the disturbed axis only, and the error becomes the synchronization error. To achieve a better synchronization, a coupling controller, which responds to the synchronization error, i.e., the difference between the two motion errors, is introduced. In this case, when a disturbance input is applied to one axis, the motion errors appear in the undisturbed axis as well as in the disturbed axis. The motion error in the undisturbed axis is introduced by the coupling controller and the adaptive feedforward controller. The adaptive synchronization problem is formulated and analyzed in the continuous time domain first, and then in the discrete time domain. Stability conditions are obtained. Effectiveness of the adaptive synchronization controller is demonstrated by simulation.
Discrete-Time Inverse Dynamics Control of Flexible Joint Robots
Authors: Jankowski K. P. , Van Brussel H.
Published: March 2008

This paper focuses on the problem of the application of inverse dynamics control methods to robots with flexible joints and electromechanical actuators. Due to drawbacks of the continuous-time inverse dynamics, discussed in the paper, a new control strategy in discrete-time is presented. The proposed control algorithm is based on numerical methods conceived for the solution of index-three systems of differential-algebraic equations. The method is computationally efficient and admits low sampling frequencies. The results of numerical experiments confirm the advantages of the designed control algorithm.
Application of Screw Theory to Rigid Body Dynamics
Authors: Pennock G. R. , Oncu B. A.
Published: March 2008

This paper applies screw theory to the dynamic analysis of a rigid body in general spatial motion. Particular emphasis is placed upon the geometric interpretation of the velocity screw, the momentum screw, and the force screw which provide valuable physical insight into the dynamic behavior of the rigid body. The geometric relation between the velocity screw and the momentum screw is discussed in some detail. The paper shows that the dual angle between the two screws provides insight into the kinetics of the rigid body. The dynamic state of motion of the body is then described by a dual vector equation, referred to as the dual Euler equation. The paper shows that the geometric equivalent of the dual Euler equation is a spatial triangle which can be used as a graphical method of solution, or as a check, of the analytical formulation. The concepts introduced in this paper are illustrated by the well-known example of a thin, homogeneous, circular disk rolling without slipping on a flat horizontal surface. With the widespread use of computer graphics and computer-aided design, the geometric approach presented here will prove useful in the graphical representation of the dynamics of a rigid body.
On the Design of Finite Time Settling Control for Linear Systems
Authors: Choura S.
Published: March 2008

The design of controllers combining feedback and feedforward for the finite time settling control of linear systems, including linear time-varying systems, is considered. The feedforward part transfers the initial state of a linear system to a desired final state in finite time, and the feedback part reduces the effects of uncertainties and disturbances on the system performance. Two methods for determining the feedforward part, without requiring the knowledge of the explicit state solutions, are proposed. In the first method, a numerical procedure for approximating combined controls that drive linear time-varying systems to their final state in finite time is given. The feedforward part is a variable function of time and is selected based on a set of necessary conditions, such as magnitude constraints. In the second method, an analytical procedure for constructing combined controls for linear time-invariant systems is presented, where the feedforward part is accurately determined and it is of the minimum energy control type. It is shown that both methods facilitate the design of the feedforward part of combined controllers for the finite time settling of linear systems. The robustness of driving a linear system to its desired state in finite time is analyzed for three types of uncertainties. The robustness analysis suggests a modification of the feedforward control law to assure the robustness of the control strategy to parameter uncertainties for arbitrary final times.
Dynamics and Control of a Translating Flexible Beam With a Prismatic Joint
Authors: Tadikonda Sivakumar S. K. , Baruh Haim
Published: March 2008

The complete dynamic model of a translating flexible beam, with a tip mass at one end and emerging from or retracting into a rigid base at the other, is presented. The model considers the effect of elastic and translational motions of the beam on each other. The properties of the eigenfunctions of a fixed-free beam are exploited to obtain closed-form expressions for several domain integrals that arise in the model. It is shown that neglecting the effect of elastic motion on the rigid body motion leads to inaccuracies in positioning control. Issues associated with the feedback control of such a beam are discussed.
Synthesis of Actively Adjustable Springs by Antagonistic Redundant Actuation
Authors: Yi Byung-Ju , Freeman Robert A.
Published: March 2008

A methodology for active spring generation is presented based on antagonistic redundant actuation. Antagonistic properties are characterized using an effective system stiffness. “Antagonistic stiffness” is generated by preloading a closed-chain (parallel) linkage system. Internal load distribution is investigated along with the necessary conditions for spring synthesis. The performance and stability of a proposed active spring are shown by simulation, and applications are discussed.
Model Reference Adaptive Control of Dual-Mode Micro/Macro Dynamics of Ball Screws for Nanometer Motion
Authors: Ro P. I. , Hubbel P. I.
Published: March 2008

A desire to improve the positioning accuracy of ball screws prompted an investigation into the dynamics of nanometer motion. Characterization of the ball screw indicated that nanometer motion is possible prior to friction breakaway via elastic deformation of the frictional contacts while macroscopic motion involves slipping across the friction interfaces. The observed dynamics are nonlinear, and consequently result in inconsistent and unpredictable closed-loop response while under PI position control. The ball-screw can be modeled in two stages: The microdynamic stage includes “elastic” friction while the macrodynamic stage incorporates kinetic (sliding) friction. A two-stage model reference adaptive control (MRAC) strategy is adopted and a Lyapunov design technique is applied to derive the adaptive laws. Experimental results obtained via a DSP implementation of the adaptive controller indicate that the each stage of the adaptive control performs well within the respective dynamic regions, but performance deteriorates as either controller is operated near the boundary of the regions.
Directional Response of a B-Train Vehicle Combination Carrying Liquid Cargo
Authors: Ranganathan R. , Rakheja S. , Sankar S.
Published: March 2008

Directional dynamics of a B-train tank vehicle is investigated by integrating the three-dimensional vehicle model to the dynamics associated with the movement of free surface of liquid within the partially filled tanks. The motion of the free surface of liquid due to instantaneous tank roll and lateral acceleration is computed assuming steady state fluid flow conditions. The influence of liquid motion on the dynamic response of the rearmost trailer is investigated for both constant and transient steer inputs, assuming constant forward speed. Directional response characteristics of the B-train tank vehicle are compared to those of an equivalent rigid cargo vehicle to demonstrate the destabilizing effects of the liquid movement within the tank vehicle. Directional response characteristics are further discussed for variation in weight density of liquid and thus the fill height, while the axle loads are held constant around maximum permissible values.
Tracking Controller for Linear Systems With Time Delays in Both State and Control Variables
Authors: Chyung Dong H.
Published: March 2008

Linear time invariant control systems with time delays in both state and control variables are studied. The problem is to design a controller so that the system response will follow a given reference input with zero steady-state error. The reference input is assumed to be a polynomial function of time. The controller is based on feeding forward the reference input and its delayed values. A method is derived for determining the feed-forward gain matrices. Necessary and sufficient condition for the existence of proposed tracking controller is also obtained. An example is given to illustrate the proposed method.
Dynamic Analysis and Control of High Speed and High Precision Active Magnetic Bearings
Authors: Youcef-Toumi K. , Reddy S.
Published: March 2008

The successful operation of actively controlled magnetic bearings depends greatly on the electromechanical design and control system design. The function of the controller is to maintain bearing performance in the face of system dynamic variations and unpredictable disturbances. The plant considered here is the rotor and magnetic bearing assembly of a test apparatus. The plant dynamics consisting of actuator dynamics, rigid rotor dynamics and flexibility effects are described. Various components of the system are identified and their corresponding linearized theoretical models are validated experimentally. Tests are also run to identify the coupling effects and flexibility modes. The highly nonlinear behavior of the magnetic bearings in addition to the inherent instability of such a system makes the controller design complex. A digital Time Delay Controller is designed and its effectiveness evaluated using several simulations based on linear and nonlinear models for the bearing including bending mode effects. This controller is implemented as an alternative to an existing linear analog compensator. Several experiments are conducted with each controller for spinning and nonspinning conditions. These include time responses, closed loop frequency responses and disturbance rejection responses. The experimental results and comparisons between those of a digital Time Delay Controller and an analog compensator indicate that the Time Delay Controller has impressive static and dynamic stiffness characteristics for the prototype considered. The Time Delay Controller also maintains almost the same dynamic behavior over a significantly wide range of rotor speeds.
Controller Design for a Force-Reflecting Teleoperator System With Kinematically Dissimilar Master and Slave
Authors: Jansen J. F. , Kress R. L. , Babcock S. M.
Published: March 2008

The purpose of this paper is to develop a controller for a force-reflecting teleoperator system having kinematically dissimilar master and slave. The controller is a stiffness controller for both the master and the slave. A mathematical problem associated with representing orientations using Euler angles is described, and Euler parameters are proposed as a solution. The basic properties of Euler parameters are presented, specifically those pertaining to stiffness control. The stiffness controller for both the master and the slave is formulated using Euler parameters to represent orientation and a Liapunov stability proof is presented for the controller. The master portion of the control scheme is implemented on a six-degree-of-freedom master.
Robotic Manipulator Collisions: Modeling and Simulation
Authors: Mills J. K. , Nguyen C. V.
Published: March 2008

In this paper, a new formulation of the dynamics of a robotic manipulator work environment is presented. The work environment is modeled in a way that permits the robot transition to and from contact with the work environment to be effectively simulated. This method circumvents the discontinuities inherent in previously proposed models of work environment dynamic models that have, until now, prevented researchers from considering that phase of manipulation. Combined with an existing model of the manipulator dynamics, the overall model of the manipulator-work environment system is such that the system states evolve continuously in time, as is the case in reality. Specifically, a continuous dynamics model is presented which models dynamic behavior of an n degree of freedom rigid link robotic manipulator during the transition to and from frictionless point contact with a work environment. The dynamic model of the work environment is sufficiently general to encompass, as limiting cases, both constrained motion and compliant motion contacts. The general properties of the work environment dynamics model are readily altered with only two parameters. A singular perturbation analysis provides an analytical approach to verification of the properties of the model of the work environment known to be true from an intuitive perspective. Results concerning the behavior of the impact force during a collision between the manipulator and work environment are also obtained using a singular perturbation theory approach. Detailed dynamic simulation results are given to illustrate the behavior of the proposed model. Simulation results of a two-degree-of-freedom manipulator with proportional and derivative control applied during the transition from noncontact to contact motion are given. Comparison of simulation results to experimentally obtained results reported in the robotics literature reveal a remarkable similarity in the time responses, given the simplicity of the work environment dynamic model.
Modeling and Parameter Estimation of Heat Exchangers—A Statistical Approach
Authors: Jonsson G. , Palsson O. P. , Sejling K.
Published: March 2008

A continuous in time dynamic model of counterflow and parallel flow heat exchangers is presented. The model is on state space form and it is shown how to use statistical methods, Kalman filtering and least squares, to estimate the model parameters. Empirical relations for convection heat transfer are incorporated in the parameters in order to improve the model performance. The parameters in these empirical formulas may be estimated with the same methods, thereby adjusting the relations to the specific heat exchanger. As a case-study, a small counterflow plate heat exchanger is modeled and some results from the parameter estimation are given.
Failure Detection Diagnostics for Thermofluid Systems
Authors: Wagner J. , Shoureshi R.
Published: March 2008

Advances in microprocessor technology have enabled the application of modern control techniques and failure detection diagnostics to various processes for improved system performance. This paper presents experimental results for an on-board microprocessor-based failure detection package designed to assist in the diagnosis of heat pump failures. A model-free limit and trend checking scheme, and a model-based innovations detection formulation operate in parallel to detect anomalous behavior. This dual approach permits the study of tradeoffs between failure detection performance and method complexity. A series of typical anomalies are experimentally simulated in a heat pump, and results are presented to demonstrate the performance of each detection strategy.
Influence of Gravity on the Manipulability Ellipsoid for Robot Arms
Authors: Chiacchio P. , Chiaverini S. , Sciavicco L. , Siciliano B.
Published: March 2008

The dynamic manipulability ellipsoid is a common tool in robotics to measure the ability of a manipulator to produce arbitrary accelerations of the end-effector for a given set of torques at the joints. This article is intended to demonstrate that for a robot arm, when gravitational forces (due to arm and payload) are properly embedded into the derivation of the ellipsoid, these do not cause a compression in the volume of the ellipsoid, as stated in the original approach, but they just produce a translation of the ellipsoid which in general occurs along all task space directions. Further, we characterize the ellipsoid for redundant manipulators by investigating the properties of the manipulator Jacobian involved in the core of the ellipsoid. Numerical case studies are developed.
Low Velocity Friction Compensation and Feedforward Solution Based on Repetitive Control
Authors: Tung E. D. , Anwar G. , Tomizuka M.
Published: March 2008

One of the most significant sources of tracking error for an X-Y table is static friction, a nonlinear disturbance at low velocity. In traversing a circular profile, an X-Y table encounters zero velocity crossings at ninety degree intervals around the circle, leaving relatively large tracking errors referred to as “quadrant glitches.” To learn the control input which eliminates errors caused by stiction, repetitive control, a subclass of learning control, is employed. Experiments, conducted on the X-Y bed of a CNC milling machine, demonstrate that near-perfect tracking can be achieved in twelve cycles or less. Of particular interest is the velocity command input generated by repetitive control. The input contains feedforward information for developing perfect trajectories at low velocities.
Human Extenders
Authors: Kazerooni H. , Guo Jenhwa
Published: March 2008

A human’s ability to perform physical tasks is limited by physical strength, not by intelligence. We coined the word “extenders” as a class of robot manipulators worn by humans to augment human mechanical strength, while the wearer’s intellect remains the central control system for manipulating the extender. Our research objective is to determine the ground rules for the control of robotic systems worn by humans through the design, construction, and control of several prototype experimental direct-drive/non-direct-drive multi-degree-of-freedom hydraulic/electric extenders. The design of extenders is different from the design of conventional robots because the extender interfaces with the human on a physical level. The work discussed in this article involves the dynamics and control of a prototype hydraulic six-degree-of-freedom extender. This extender’s architecture is a direct drive system with all revolue joints. Its linkage consists of two identical subsystems, the arm and the hand, each having three degrees of freedom. Two sets of force sensors measure the forces imposed on the extender by the human and by the environment (i.e., the load). The extender’s compliances in response to such contact forces were designed by selecting appropriate force compensators. The stability of the system of human, extender, and object being manipulated was analyzed. A mathematical expression for the extender performance was determined to quantify the force augmentation. Experimental studies on the control and performance of the experimental extender were conducted to verify the theoretical predictions.
Control of Machining Processes
Authors: Ulsoy A. Galip , Koren Y.
Published: March 2008

This paper reviews the important recent research contributions for control of machining processes (e.g., turning, milling, drilling, and grinding). The major research accomplishments are reviewed from the perspective of a hierarchical control system structure which considers servo, process, and supervisory control levels. The use and benefits of advanced control methods (e.g., optimal control, adaptive control) are highlighted and illustrated with examples from research work conducted by the authors. Also included are observations on how significant the research to date has been in terms of industrial impact, and speculations on how this research area will develop in the coming decade.