Individual Axis Research Articles

Design and application of a sliding mode controller for accurate motion synchronization of dual servo systems

This paper presents a continuous time sliding mode controller (SMC) design to deal with the problem of motion synchronization in dual spindle servo systems. Synchronization error is defined as the differential position error between the two servo drives that follow identical reference motion trajectory. Proposed SMC controller penalizes three error states; namely individual axis tracking errors and the synchronization error for accurate synchronization. The control law is derived from Lyapunov energy function without switching condition. The controller shows robust motion synchronization against disturbances and parameter variations. Proposed SMC control is implemented in conventional double-sided machining operation.

Synchronous control for high-accuracy biaxial motion systems

This paper presents an efficient synchronization control scheme for a high-accuracy synchronous motion system. In particular, an optimal PID controller for individual motion axis is first developed to guarantee satisfactory tracking performance according to traditional controller tuning strategy. Then, an additional synchronous controller is introduced to generate cross-coupling control action, so that synchronous position error across axes due to system manufacturing tolerance or disturbance could be suppressed. Experimental results on a positioning system equipped with two permanent-magnet linear motors demonstrate that the synchronization performance with the proposed control scheme could be enhanced.

Monolithic Tri-Axes Nickel-Based Accelerometer Design Verified Through Finite Element Analysis

The complete mathematical modeling and design verification of a novel monolithically integrated tri-axes MEMS capacitive accelerometer is presented in this paper. The designed accelerometer is a single structure having three individual single axis accelerometers, integrated on a single substrate uniformly centered on single axis with chip size of 3.2 mm × 3.5 mm. We have used standard commercially available surface micromachining technology MetalMUMPs available from MEMSCAP Inc. The designed accelerometer is optimized by analytical technique using Matlab. The physical level simulation is done in the Analyzer module of CoventorWare to verify the structural model of designed accelerometer. It is concluded that the results obtained from the physical level simulation are in good agreement with the analytically calculated results. The design has been successfully verified using the Finite Element Analysis.

Haptic-based training for tank gunnery using decoupled motion control.

For training human motor skills, haptic guidance has proven more effective than traditional visual-feedback-only approaches. However, novices might become dependent on the feedback force provided during training and become unable to adapt to real operating environments. To overcome haptic-based training's limitations, a proposed approach uses decoupled motion control, which divides a motion into individual coordinate axis movements controlled by multiple operators. Using a networked haptic interaction system, the trainee cooperates with an expert to complete a training task. Unlike previous approaches, the force or torque exerted by the trainee's device doesn't directly correct the trainee's hand action. Instead, the trainee regulates his or her manipulation to cooperate with the expert by feeling motion feedback from the expert. The Web extra at http://youtu.be/qYBsR6AOjzQ is a video that shows a test subject operating a training simulator for tank gunnery that uses haptics.

Marker-free dual-axis tilt series alignment

Dual-axis tilt series in electron tomography are collected by successively tilting the object about two approximately orthogonal tilt axes. Here we report on the extension of marker-free image registration based on cross-correlation techniques to dual-axis tilt series. A simultaneous geometry refinement yields accurate parameters for the computation of the final reconstruction. Both, image registration and 3D-reconstruction operate on the combined data from the paired single axis series rather than computing individual single axis tomograms followed by a separate combination step. We show that with simultaneous registration and reconstruction of dual-axis tilt series, tomograms with higher resolution are obtained than by merging separately computed tomograms.

Development of a surgical instrument for measuring forces applied to the ossicles of the middle ear

Surgery of the middle ear is a delicate process that requires the surgeon to manipulate the ossicles, the smallest bones in the body. Excessive force applied to the ossicles can easily be transmitted through to the inner ear which may cause a permanent sensorineural hearing loss. An instrument was required to measure the forces applied to cadaveric temporal bone ossicles with the vision of measuring forces in vivo at a later stage. A feasibility study was conducted to investigate a method of measuring force and torque applied to the ossicles of the middle ear. Information from research papers was gathered to determine the expected amplitudes. The study looked at commercially available transducers as well as constructing an instrument using individual axis transducers coupled together. A prototype surgical instrument was constructed using the ATI industrial automation Nano17 six axis transducer. The Nano17 allows for the measurement of force and torque in the X, Y and Z axis to a resolution of 1/320N. The use of the Nano17 enabled rapid development of the surgical instrument. It meets the requirements for its use on cadaveric models and has the potential to be a useful data collection tool in vivo.

Association study of molecular polymorphisms in candidate genes related to stress responses with production and meat quality traits in pigs

The hypothalamic-pituitary-adrenal (HPA) axis exerts a large range of effects on metabolism, the immune system, inflammatory processes, and brain functions. Together with the sympathetic nervous system, it is also the most important stress-responsive neuroendocrine system. Both systems influence production traits, carcass composition, and meat quality. The HPA axis may be a critical target for genetic selection of more robust animals. Indeed, numerous studies in various species have demonstrated the importance of genetic factors in shaping the individual HPA axis phenotype, and genetic polymorphism can be found at each level of the axis, including hormone production by the adrenal cortices under stimulation by adrenocorticotropic hormone (ACTH), hormone bioavailability, or receptor and postreceptor mechanisms. The aim of the present experiment was to extend these findings to the brain neurochemical systems involved in stress responses. To this end, a number of candidate genes were sequenced for molecular polymorphisms and their association was studied with stress neuroendocrine and production traits in a genetically diverse population consisting of 100 female pigs from an advanced intercross (F10-F12) between 2 highly divergent breeds, Large White (LW) and Meishan (MS). The LW breed has a high production potential for lean meat and a low HPA axis activity, and the MS breed has low growth rate, fat carcasses—but large litters of highly viable piglets—and a high HPA axis activity. Candidate genes were chosen in the catecholaminergic and serotonergic pathways, in the pituitary control of cortisol production, among genes previously demonstrated to be differentially expressed in ACTH-stimulated adrenal glands from LW and MS pigs, and in cortisol receptors. Sixty new polymorphisms were found. The association study with carcass and meat quality traits and with endocrine traits showed a number of significant results, such as monoamine oxidase (MAOA) polymorphisms with growth rate (P = 0.01); lean content and intramuscular fat (P < 0.01), which are the most important traits for carcass value; dopamine receptor D3 (DRD3) with carcass composition (P < 0.05); and vasopressin receptor 1B (AVPR1B) with meat quality traits (P ≤ 0.05). The effect of these polymorphisms on neuroendocrine parameters (eg DRD3 and HPA axis or AVPR1B and catecholamines) indicates information regarding their biological mechanism of action.

Real-time inertia compensation for multi-axis CNC machine tools

Variation of the effective moment of inertia due to load disturbance in a CNC feed drive system may increase control error for each axis of motion and thereby degrading total precision including contouring accuracy. Although some investigations have been made on estimation and control of variation of the effective moment of inertia, most of them are for individual axis control: there has been no research that considered the improvement of contouring accuracy in CNC machine tools under load variation. In this paper, a real-time inertia compensation method is proposed including a newly defined contour error model that represents error caused by load disturbance. Position error due to load variation is calculated based on the estimated disturbance torque by a full-order disturbance observer for each drive axis. The position error is then used to establish the new contour error model considering the effect of load variation. The proposed compensation method is realized by adjusting velocity loop gains in the control system using the least square method such that the effect of variation of the effective moment of inertia on the contour error is minimized. The proposed method is evaluated with a 3-axis open CNC testbed.

Indicators of deforestation in the Southern Brazilian Pre-Amazon

In recent years, Amazonian deforestation has become a question of global concern. Deforestation in Amazon is a complex phenomenon in nature and has been related to traditional agriculture expansion. In this work, land use, socioeconomic and conservation indicators, combined with statistical analysis, were used to understand forces associated with patterns of deforestation. This approach was applied in Southern Brazilian Pre-Amazon in Mato Grosso State, which represents an extensive rain forest-savanna ecotone, located in the south border of Amazon biome. Based on data from the last two agricultural censuses (1995/1996–2006), we compared agricultural expansion in this area and Mato Grosso state. Results have shown that 85 % of state deforestation was concentrated in Southern Pre-Amazon and was closely related to increase in number of cattle and pasture area. PCA results pointed that population (92 %), number of cattle (86.5 %), pastures (84.2 %) and tractors (78.4 %) were variables with highest positive correlation to deforestation. It showed that GDP contributes to an individual axis and has a low correlation to deforestation (37.8 %). Conservation units and indigenous reserves also contribute to a single axis and were negatively correlated to temporary crops area. Results revealed a significant reduction in production and commercialization of extractive products in the region, revealing that the main, almost only conservation policy in Mato Grosso remains the creation of Special Areas. We suggest that further studies are necessary to screen development alternatives to simple cutting trees down. It is important to diversify strategies for deforestation control, and development aspects must be more seriously considered to reach a sustainable deforestation control policy.

Growth and Asymmetry of Soil Microfungal Colonies from “Evolution Canyon,” Lower Nahal Oren, Mount Carmel, Israel

BackgroundFluctuating asymmetry is a contentious indicator of stress in populations of animals and plants. Nevertheless, it is a measure of developmental noise, typically obtained by measuring asymmetry across an individual organism's left-right axis of symmetry. These individual, signed asymmetries are symmetrically distributed around a mean of zero. Fluctuating asymmetry, however, has rarely been studied in microorganisms, and never in fungi.Objective and MethodsWe examined colony growth and random phenotypic variation of five soil microfungal species isolated from the opposing slopes of “Evolution Canyon,” Mount Carmel, Israel. This canyon provides an opportunity to study diverse taxa inhabiting a single microsite, under different kinds and intensities of abiotic and biotic stress. The south-facing “African” slope of “Evolution Canyon” is xeric, warm, and tropical. It is only 200 m, on average, from the north-facing “European” slope, which is mesic, cool, and temperate. Five fungal species inhabiting both the south-facing “African” slope, and the north-facing “European” slope of the canyon were grown under controlled laboratory conditions, where we measured the fluctuating radial asymmetry and sizes of their colonies.ResultsDifferent species displayed different amounts of radial asymmetry (and colony size). Moreover, there were highly significant slope by species interactions for size, and marginally significant ones for fluctuating asymmetry. There were no universal differences (i.e., across all species) in radial asymmetry and colony size between strains from “African” and “European” slopes, but colonies of Clonostachys rosea from the “African” slope were more asymmetric than those from the “European” slope.Conclusions and SignificanceOur study suggests that fluctuating radial asymmetry has potential as an indicator of random phenotypic variation and stress in soil microfungi. Interaction of slope and species for both growth rate and asymmetry of microfungi in a common environment is evidence of genetic differences between the “African” and “European” slopes of “Evolution Canyon.”

Apparent mass and head vibration transmission responses of seated body to three translational axis vibration

The apparent mass and seat-to-head vibration transmissibility response functions of the seated human body were investigated under whole-body vibration exposures to fore-aft (x), lateral (y), and vertical (z) applied individually and simultaneously. The experiments were performed with 9 adult male subjects to measure the biodynamic responses to single and uncorrelated three-axis vibration with and without hands and back supports under different magnitudes of random vibration in the 0.5–20Hz frequency range. The apparent mass and the head vibration transmission responses were derived using two different frequency response function estimators based upon the cross- and auto-spectral densities of the response and excitation signals, denoted as H1 and Hv estimators, respectively. The two methods resulted in identical single-axis responses but considerably different responses under multi-axis vibration. The responses derived from the Hv estimator revealed significant coupling effects of three-axis vibration, which could be directly related to contributions of cross-axis responses observed under single-axis vibration, particularly those attributed to sagittal plane motion of the upper body. Such coupling effect, however, was not evident in the three-axis responses derived using the commonly used H1 estimator. The results also revealed significant effects of hands and back support conditions on the coupling effects of multiple axis vibration and the measured responses. The results suggest that biodynamic responses of the seated body exposed to simultaneous three-axis vibration, commonly encountered in work vehicles, differ considerably from the widely reported responses to individual axis vibration. A better understanding of the seated human body responses to uncorrelated three-axis whole-body vibration could be developed using the power-spectral-density based Hv estimator. Relevance to industryThe seated body biodynamic responses to multi-axis whole-body vibration and knowledge of coupling in the responses are essential for developing more efficient analytical models of the seated human body for applications in vehicular seating design and dynamics, and for deriving improved frequency-weighting for exposure assessment.

Experimental characterization of lateral profiles of scanned proton and carbon ion pencil beams for improved beam models in ion therapy treatment planning

Scanned ion pencil beams carry a low-dose envelope which can extend up to several centimeters from the individual beam central axis. Depending on the energy and species of the beam, this halo consists mainly of secondary particles produced by nuclear interactions in the target or of particles undergoing multiple Coulomb scattering in the beam line components. This halo is often neglected by single Gaussian beam modeling in current treatment planning systems. One possibility of improving the accuracy of treatment planning is to upgrade the used pencil beam models by adding a description of the low-dose envelope. But at the same time it is crucial to keep the calculation time and the complexity for treatment planning in reasonable limits. As a first approach we measured the lateral beam profiles of scanned proton and carbon ion pencil beams at different energies and depths in water and air at the Heidelberg Ion Beam Therapy Center. Then we tried to describe their beam halo by adding a supplementary Gaussian function to the standard single Gauss modeling which is used at the moment by our treatment planning systems. This analysis helped to identify trends in the parameters describing the lateral beam broadening to support its modeling. Finally, it is shown that the accuracy of treatment planning could be improved by the proposed upgrade of the pencil beam model. In particular, the presented experimental data can be either used directly as input for dose calculation or serve for representative comparison with the results of calculation models such as Monte Carlo simulations for the generation of lateral basic data to be input in upgraded beam models of treatment planning systems.

Physical Level Simulation of PolyMUMPs Based Monolithic Tri-Axis MEMS Capacitive Accelerometer Using FEM Technique

In this paper, we present the design verification of PolyMUMPs based monolithic tri-axis MEMS capacitive accelerometer. The physical level simulation has been done using the analyzer module of Coventorware to verify the performance of the three-axis accelerometer using Finite Element Method (FEM) and compared with the optimized results obtained in ANSYS and in MATLAB. The 2D model is created in the designer module of Coventorware. The 3D layout is generated in the preprocessor module and mesh is created on solid model. Proposed three axis accelerometer has three individual single axis accelerometers, integrated on a single substrate uniformly centered on single axis. Low mechanical noise, high sensitivity and sense capacitance have been measured for all axes individually and presented. The results obtained from both the analytical and finite element models are found to be in excellent agreement.

Stochastic finite element analysis of composite plates considering spatial randomness of material properties and their correlations

Considering the randomness of material parameters in the laminated composite plate, a scheme of stochastic finite element method to analyze the displacement response variability is suggested. In the formulation we adopted the concept of the weighted integral where the random variable is defined as integration of stochastic field function multiplied by a deterministic function over a finite element. In general the elastic modulus of composite materials has distinct value along an individual axis. Accordingly, we need to assume 5 material parameters as random. The correlations between these random parameters are modeled by means of correlation functions, and the degree of correlation is defined in terms of correlation coefficients. For the verification of the proposed scheme, we employ an independent analysis of Monte Carlo simulation with which statistical results can be obtained. Comparison is made between the proposed scheme and Monte Carlo simulation.

Probing dipole coupled nanomagnets using magnetoresistance read

We experimentally demonstrated magnetoresistance (MR) read of dipole coupled nanomagnets using magnetic tunnel junctions. The MR allowed the magnetic state of individual nanomagnets to be electrically measured. The sensitivity of the read scheme enabled a systematic study regarding the nanomagnet spacing and revealed a transition in behavior. Below a spacing of 15 nm the dipole field overcomes the individual shape anisotropy and redefines the individual element easy axis along the direction transmission line. The demonstration of MR electrical read marks a significant step forward for applications such as magnetic quantum cellular automata logic devices.

Research on Geometric Errors Model and Identification of 5-Axis Machining Center for Processing Turbo Molecular Pump Rotor

This paper investigates the accuracy evaluative factors of 5-axis turbo molecular pump rotor machining center.Using rigid body kinematics techniques and homogenous transformation matrices, the systemic geometric volumetric error model are established for error synthesis. Novel volumetric accuracy model can be verified effectiveness better estimation of machine performance, by means of physical simulation and measurement. The effect of the individual axis geometric errors can become increasingly significant as the chain of dependent axis is extended. The effect of the rotary axis and their errors cannot be ignored. Calculating volumetric accuracy as the maximum difference between the error vector at any two positions can be computationally intensive.

Population-Attributable Fractions of Axis I and Axis II Mental Disorders for Suicide Attempts: Findings From a Representative Sample of the Adult, Noninstitutionalized US Population

We aimed to determine the percentage of suicide attempts attributable to individual Axis I and Axis II mental disorders by studying population-attributable fractions (PAFs) in a nationally representative sample. Data were from the National Epidemiologic Survey on Alcohol and Related Conditions Wave 2 (NESARC; 2004-2005), a large (N = 34 653) survey of mental illness in the United States. We used multivariate logistic regression to compare individuals with and without a history of suicide attempt across Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Axis I disorders (anxiety, mood, psychotic, alcohol, and drug disorders) and all 10 Axis II personality disorders. PAFs were calculated for each disorder. Of the 25 disorders we examined in the model, 4 disorders had notably high PAF values: major depressive disorder (PAF = 26.6%; 95% confidence interval [CI] = 20.1, 33.2), borderline personality disorder (PAF = 18.1%; 95% CI = 13.4, 23.5), nicotine dependence (PAF = 8.4%; 95% CI = 3.4, 13.7), and posttraumatic stress disorder (PAF = 6.3%; 95% CI = 3.2, 10.0). Our results provide new insight into the relationships between mental disorders and suicide attempts in the general population. Although many mental illnesses were associated with an increased likelihood of suicide attempt, elevated rates of suicide attempts were mostly attributed to the presence of 4 disorders.

Reliability of Lower Limb Frontal Plane Alignment Measurements Using Plain Radiographs and Digitized Images

This study evaluated the reliability of lower limb frontal plane alignment measures obtained from plain radiographs measured manually and digitized images measured using a custom computer software package (TheHTO Pro; Fowler Kennedy Sport Medicine Clinic, London, Ontario, Canada). Radiographic measurements used in the planning of high tibial osteotomy, including the mechanical axis angle and mechanical axis deviation, were measured on 42 hip-to-ankle radiographs on two separate occasions by two different raters (A.V.S., J.J.D.). Intraclass correlation coefficients (0.96-0.99) indicated excellent agreement between the manual and computer measurements, suggesting both methods can be used interchangeably. Although test-retest and inter-rater reliability tended to be slightly better when using TheHTO Pro, intraclass correlation coefficients were excellent for both methods (0.97-0.99). The standard errors of measurement were <1 degree for mechanical axis angle and <2 mm for mechanical axis deviation, regardless of method or rater. Based on the observed standard errors of measurement, conservative estimates for the error associated with an individual's mechanical axis angle at one point is approximately 1.5 degrees, and the minimal detectable change on reassessment is approximately 2 degrees. The error associated with an individual's mechanical axis deviation at one point is approximately 4 mm, and the minimal detectable change on reassessment is approximately 6 mm. These results suggest that manual and computer measurements of lower limb frontal plane alignment can be calculated with minimal measurement error. However, the small errors associated with both methods should be considered when making clinical decisions.

Monte Carlo investigation of the low-dose envelope from scanned proton pencil beams

Scanned proton pencil beams carry a low-dose envelope that extends several centimeters from the individual beam's central axis. Thus, the total delivered dose depends on the size of the target volume and the corresponding number and intensity of beams necessary to cover the target volume uniformly. This dependence must be considered in dose calculation algorithms used by treatment planning systems. In this work, we investigated the sources of particles contributing to the low-dose envelope using the Monte Carlo technique. We used a validated model of our institution's scanning beam line to determine the contributions to the low-dose envelope from secondary particles created in a water phantom and particles scattered in beam line components. Our results suggested that, for high-energy beams, secondary particles produced by nuclear interactions in the water phantom are the major contributors to the low-dose envelope. For low-energy beams, the low-dose envelope is dominated by particles undergoing multiple Coulomb scattering in the beam line components and water phantom. Clearly, in the latter situation, the low-dose envelope depends directly on beam line design features. Finally, we investigated the dosimetric consequences of the low-dose envelope. Our results showed that if not modeled properly the low-dose envelope may cause clinically relevant dose disturbance in the target volume. This work suggested that this low-dose envelope is beam line specific for low-energy beams, should be thoroughly experimentally characterized and validated during commissioning of the treatment planning system, and therefore is of great concern for accurate delivery of proton scanning beam doses.

Human models in acute and chronic stress: Assessing determinants of individual hypothalamus–pituitary–adrenal axis activity and reactivity

Stress is one of the most significant health problems in modern societies and the 21st century. This explains a pressing need for investigations into the biological pathways linking stress and health. Besides the locus coeruleus–noradrenaline/autonomic (sympathetic) nervous system (), the hypothalamus–pituitary–adrenal (HPA) axis is the major physiological stress response system in the body. Since alterations in HPA axis regulation under basal conditions and in response to acute stress appear to be a close correlate or even a determining factor of the onset of different diseases or disease progression (; ; ; ; ; ; ), the characterization of an individual's HPA axis activity as well as reactivity pattern to psychosocial stress appears to be of major interest. It is obvious that such a research agenda substantially depends on the availability of appropriate measures. However, since the HPA axis is a highly adaptive system which is characterized by marked inter- and intraindividual variability (; ), the development of such markers of HPA axis regulation in humans was—and still is—a rather challenging task. In this brief review, we focus on findings on two HPA axis measures, namely the cortisol-awakening response (CAR) to assess HPA axis basal activity and the Trier social stress test (TSST) to investigate HPA axis stress reactivity.