bluuebunny/crossref_metadata_2025 huggingface dataset:
Systemic and forearm vascular resistance changes after upright bicycle exercise in man.
Authors: Coats A J , Conway J , Isea J E , Pannarale G , Sleight P , Somers V K
Published: December 2014

1. Blood pressure, cardiac function and forearm blood flow following voluntary maximal upright bicycle exercise were studied in thirteen normal volunteers in a cross‐over design against a control day. 2. After exercise there was a short‐lived (5‐10 min) increase in systolic blood pressure, peak aortic blood velocity and aortic acceleration suggesting a persistence of the positive inotropic influence of exercise. 3. Systemic vasodilation, which was seen immediately exercise stopped, lasted at least 60 min. This was associated with a reduction in diastolic blood pressure for the whole hour. After 30 min systolic blood pressure was also reduced. Heart rate and cardiac output were still significantly elevated and systemic vascular resistance still reduced at 60 min post‐exercise. 4. A non‐exercising limb vascular bed (forearm) showed a marked vasodilation for 1 h after predominately leg exercise indicating the presence of a vasodilatory influence affecting vascular beds other than the exercising muscle groups.
Contribution of human short‐wave cones to luminance and motion detection.
Authors: Lee J , Stromeyer C F
Published: December 2014

1. Human short‐wave S cone signals are important for colour vision and here we examine whether the S cone signals also contribute to motion and luminance. 2. Detection was measured with moving patterns that selectively stimulated S cones‐violet sine‐wave gratings of 1 cycle deg‐1 on an intense yellowish field. For rates up to 12 Hz, detection was governed by non‐directional mechanisms, possibly of a chromatic nature, as shown by three findings: moving gratings had to be suprathreshold for their direction to be identified; the threshold ratio of counterphase flickering versus moving gratings was low; and direction‐selective adaptation was essentially absent. 3. Evidence for less sensitive, directional mechanisms includes the following: at high velocity, the direction of movement of the violet gratings can be identified just slightly above the detection threshold; directional adaptation was strong with a suprathreshold test pattern; velocity was seen veridically for clearly suprathreshold patterns; and a counterphase flickering test, added in spatial‐temporal quadrature phase to a similar suprathreshold mask, had identical detection and direction‐identification thresholds. 4. Interactions of long‐wave L cone and S cone signals in direction‐selective mechanisms were measured with an orange counterphase grating and a violet counterphase test, both flickering at the same rate and presented in spatial quadrature phase on the yellowish adapting field. Direction identification thresholds, measured as a function of the temporal phase of two gratings, demonstrated both that the S cone signal lags considerably behind the L cone signal (an effect that strongly varies with S cone light adaptation), and more strikingly, the S cone signal summates with a negative sign and thus is effectively inverted in direction‐selective mechanisms. 5. Quantitatively similar temporal phase functions were obtained with uniform violet and orange flicker when a luminance discrimination criterion was used: thus the S cone signal summates negatively with the L cone signal for both discrimination of luminance flicker and the direction of motion. 6. The temporal phase functions accurately predicted threshold summation for identifying the direction of motion of a pair of violet and orange gratings moving with the same velocity but with different spatial phase offsets. Once the relative temporal phase lag of the S cones was compensated for, there was linear threshold summation for the violet and orange patterns when presented in effective (physiological) spatial antiphase, and clear cancellation when presented in phase. This and related experiments show a linear summation of S, M and L cone signals for direction detection, with the S cones having a negative sign.(ABSTRACT TRUNCATED AT 400 WORDS)
Geographutoxin‐sensitive and insensitive sodium currents in mouse skeletal muscle developing in situ.
Authors: Gonoi T , Hagihara Y , Kobayashi J , Nakamura H , Ohizumi Y
Published: December 2014

1. The whole‐cell voltage‐clamp technique was used to examine developmental changes of Na+ current properties in single fibres of mouse flexor digitorum brevis muscles developing in situ from birth to 20 days post‐natal. 2. Geographutoxin II (GTX II), a novel polypeptide toxin from the marine snail Conus geographus, distinguished two different types of voltage‐sensitive Na+ currents: GTX II‐sensitive and GTX II‐insensitive currents, which corresponded respectively to currents with high or low TTX sensitivity. 3. Voltage‐dependent activation and inactivation of the GTX II‐insensitive currents occurred at membrane potentials 10‐20 mV more negative than those for the GTX II‐sensitive currents. 4. The GTX II‐insensitive current in fibres from mice older than 8 days inactivated more slowly than the GTX II‐sensitive current. However, in fibres from younger mice, the two currents decayed with similar speed. 5. The mean specific Na+ conductance (gNa) for the total (GTX II‐sensitive plus GTX II‐insensitive) Na+ channels was 0.22 mS/muF at a Na+ concentration of 5 mM at birth. The total gNa increased 6‐fold to 1.32 mS/muF during the first 20 days after birth. 6. The mean specific gNa for the GTX II‐insensitive channels was 0.15 mS/muF at birth, remained at approximately the same level for the first 8 days, and then decreased progressively to become undetectable by day 16. 7. In muscle fibres denervated 12 days after birth, the GTX II‐insensitive gNa increased over the next 8 days, whereas the total gNa increased less than normal. 8. By contrast, in fibres denervated on day 4, the total gNa increased more than normal in the following 8 days, and the GTX II‐insensitive specific gNa increased above the level seen at birth. 9. Half‐maximal activation and inactivation potentials of the total and the GTX II‐insensitive currents shifted in the negative direction by 9‐17 mV in the first 8 days after birth. 10. We conclude that the regulatory effects of innervation on the total gNa are either suppressive or enhancing depending on the stage of development. On the other hand, denervation elicits an increase in GTX II‐insensitive Na+ currents at all ages studied.
Post‐natal development of K+ currents studied in isolated rat pineal cells.
Authors: Aguayo L G
Published: December 2014

1. The voltage‐activated outward currents in diencephalon‐derived neuroendocrine pineal cells, dissociated from rats aged 1 day to 3 weeks post‐natal, were studied with the whole‐cell variation of the patch‐clamp technique and compared with those of adult rats (1‐3 months post‐natal). 2. Thirty‐five per cent of the 1‐week‐old cells displayed a single slowly inactivating outward current that had properties which distinguished it from the classical IA and IK currents. This current, named IK(d) for developmental, activated at potentials near ‐35 mV. Its time to half‐maximal activation (t 1/2) ranged from 16 ms at ‐30 mV to 4 ms at + 15 mV. No other membrane currents were apparent with depolarizing steps up to +80 mV. 3. IK(d) displayed slow inactivation at depolarized potentials. The time constant for this inactivation was on the order of several hundred milliseconds. The curve for steady‐state inactivation disclosed that the current was 50% inactivated near ‐90 mV. This current was not found in cells dissociated from animals 4 or more weeks of age. 4. The reversal potential determined from the amplitude of the tail current at various repolarizing voltages was ‐76 mV. Tetraethylammonium and 4‐aminopyridine reduced the amplitude of the current. The amplitude and time course of this current was not affected by the removal of external Ca2+. Similarly, removal of Cl‐ did not affect the current characteristics. 5. Sixty‐five per cent of the 1‐week‐old cells displayed IA and IK. IK rose slowly with time and displayed a threshold of activation near ‐20 mV. No current decay was observed during a 160 ms pulse. IA activated with step potentials positive to ‐50 mV. This current rose faster than IK(d) and IK, and it had a significant decay over a 160 ms pulse. 6. IA and IK were observed as early as 1 day after birth. Comparison of the time course of activation of IA and IK from young and adult animals showed a small increase (2‐3 ms at 0 mV) in the time to peak and half‐maximal current, respectively. With a step potential to ‐20 mV, the time constant of decay of IA increased from 34.6 ms in 2‐day‐old animals to 42.9 ms in adult animals. 7. The results indicate that unlike adult pineal cells, some cells from young animals express a kinetically distinct outward current (IK(d)) which was observed in the absence of IA and IK.(ABSTRACT TRUNCATED AT 400 WORDS)
Strontium‐induced creep currents associated with tonic contractions in cardiac myocytes isolated from guinea‐pigs.
Authors: Niggli E
Published: December 2014

1. Strontium can replace calcium in a number of physiological and biochemical processes. The effects of Sr2+ were investigated in enzymatically isolated ventricular myocytes of the guinea‐pig. Action potentials and membrane currents were measured with the patch‐clamp technique used in the whole‐cell recording configuration. Mechanical activity was assessed utilizing a laser‐light diffraction system for sarcomere length measurements in single heart cells. 2. When experiments where carried out using 2 mM‐Sr2+ to replace 2 mM‐Ca2+ action potentials were found to be prolonged up to severalfold. Voltage‐clamp experiments revealed that the slow inward current (Isi) inactivated more slowly. With Ca2+ replaced by Sr2+, the onset of the twitch was delayed, the maximum shortening was increased and a marked voltage‐dependent tonic shortening developed. 3. Voltage‐clamp pulses of 3.3 s duration were applied to investigate changes of the steady‐state current‐voltage relationship produced by replacing Ca2+ with Sr2+. Large slow changes of membrane currents produced by Sr2+ were observed. The identity and time course of these currents were investigated after blocking Isi and potassium currents pharmacologically. The remaining current had many of the characteristics of ‘creep currents’ (Eisner & Lederer, 1979; Hume & Uehara, 1986 a, b). The creep currents were found to be paralleled by changes of the intracellular Sr2+ concentration, as determined by tracking the sarcomere length during the accompanying tonic contractions. 4. The creep currents were suppressed by Ni2+ (2 mM), a finding that suggests that the Na+‐Ca2+ exchanger may be responsible for producing these currents (Kimura, Miyamae & Noma, 1987). The question remains, however, whether the Na+‐Ca2+ exchanger is responsible for generating the currents itself or whether it may influence another current source by changing the intracellular Sr2+ concentration. 5. To test the role of the Na+‐Ca2+ exchanger in producing the creep currents, the reversal potential of the creep current was investigated. Simple voltage protocols were inadequate to distinguish between the two current sources. However, loading the cytosol with Sr2+ by means of a second pipette sealed to the same cell in the presence of Ni2+ as an inhibitor of the Na+‐Ca2+ exchanger revealed difference currents compatible with a non‐specific cationic channel activated by intracellular Sr2+ (Ehara, Noma & Ono, 1988). 6. In conclusion, the creep currents produced when Ca2+ is replaced by Sr2+ appear to arise from an increase of intracellular Sr2+ which activates a non‐specific cation channel. A contribution from the Na+‐Ca2+ exchanger can not be excluded.
Dual action (stimulation, inhibition) of D600 on contractility and calcium channels in guinea‐pig and cat heart cells.
Authors: McDonald T , Pelzer D , Trautwein W
Published: December 2014

1. We examined the effects of D600 (0.2‐40 microM, generally 2 microM) on the following (i) developed tension in guinea‐pig papillary muscles, (ii) calcium current (Ica) and tension in cat ventricular muscle strands, (iii) Ica in guinea‐pig and cat ventricular myocytes, (iv) single Ca2+ channel currents carried by Ba2+ in cell‐attached membrane patches of guinea‐pig ventricular myocytes, and (v) Ba2+ currents through dihydropyridine (DHP)‐binding sites (skeletal muscle) reconstituted into single functional Ca2+ channels in lipid bilayers. 2. In 27 of 140 preparations studied, D600 elicited a transient stimulation that preceded marked inhibition. The stimulation was normally of short duration (less than 5 min) and moderate strength (less than 50% increase). 3. D600 had no effect on the unit conductance of single cardiac Ca2+ channels. Stimulation was characterized by a decrease in the number of records with no openings (blanks) and an increase in the open‐state probability of non‐blanks (longer open times, shorter closed times). Inhibition began with an increase in the number of blanks and later included a curtailment of open times and a prolongation of closed times. The net effect after 9 min D600 was a 75% reduction in average current amplitude. 4. A similar pattern of changes in channel open and closed times produced enhancement and then depression of time‐averaged open‐state probability in single reconstituted channels. 5. Single Ca2+ channel current that was stimulated by adrenaline was only slightly depressed after 2 microM‐D600 for 30 min. It may be that channel phosphorylation or Gs‐protein activation following beta‐receptor stimulation reduces channel affinity for D600. 6. Short‐lived binding of D600 to a single inhibitory site may enhance association/activation of Gs‐protein and thereby cause transient up‐regulation prior to increased drug occupancy and inhibition. Alternatively, there may be separate stimulatory and inhibitory sites. One aspect of inhibition, the increased frequency of blanks, is attributed to a stabilization of the inactivated state; the other aspect, changes in fast kinetics, seems to require a different explanation.
Characteristics of a 5‐hydroxytryptamine‐sensitive adenylate cyclase in intact and intracellularly perfused squid axons.
Authors: Allen T J
Published: December 2014

1. Cyclic AMP metabolism was studied in intact and intracellularly perfused axons. 2. Cyclic AMP content of intact axons lay within the range 10‐100 nmol kg‐1 axoplasm. This was increased by exposure to caffeine (2‐fold) and to 5‐HT (15‐fold). The caffeine‐sensitive cyclic AMP increase was 30‐fold larger in the presence of 5‐HT. 3. A reduction in sodium concentration from the sea water bathing intact axons attenuated the 5‐HT‐evoked increase in cyclic AMP content, but had little effect on resting cyclic AMP. This effect was partially reversed by exclusion of external calcium, and suggests that free calcium plays a role in cyclic AMP homeostasis. 4. Prolonged exposure of intact axons to 5‐HT (up to 3 h) led to apparent desensitization of the cyclic AMP response. 5. Intracellular perfusion can be used as a method to study adenylate cyclase in a single axon, simply by measuring the cyclic AMP content of the emerging perfusate. 6. Intracellular perfusion revealed micromolar requirements for internal GTP (K0.5 approximately 1‐10 microM) and external 5‐HT (K0.5 approximately 1‐10 microM); a detailed investigation of this observation was limited due to the progressive loss of 5‐HT‐evoked adenylate cyclase activity with time. This slow loss was not seen during Gpp(NH)p (guanylylimidodiphosphate), NaF or forskolin activation of cyclase activity. 7. In perfused axons, an increase in intracellular calcium stimulated cyclase activated by 100 microM‐forskolin but inhibited cyclase activated by 500 microM‐Gpp(NH)p or 10 mM‐NaF. A reduction in intracellular magnesium from 10 to 4‐5 mM attenuated the effects of 5‐HT‐evoked cyclase activity. 8. Study of the perfused axon allows characterization of the intracellular requirements of a plasmalemmal transduction system which activates adenylate cyclase, whilst maintaining ionic asymmetry across the cell membrane.
Modulation of the delayed rectifier K+ current by isoprenaline in bull‐frog atrial myocytes.
Authors: Giles W , Nakajima T , Ono K , Shibata E F
Published: December 2014

1. The effects of isoprenaline (ISO) on the calcium current (ICa) and delayed rectifier K+ current (IK) were examined using a tight‐seal whole‐cell voltage‐clamp technique in single cells from bull‐frog atrium to examine the ionic mechanism(s) of catecholamine‐induced action potential shape changes. 2. The effects of ISO on the action potential were dose‐dependent. Very low doses (5 x 10(‐9) M) prolonged the action potential. Higher doses (10(‐6) M) of ISO increased the plateau height, but shortened the action potential by accelerating the early repolarization phase. 3. ISO increased IK and ICa in a dose‐dependent fashion. Both of these effects were blocked by a beta‐receptor antagonist, propranolol (3 x 10(‐7) M). In contrast IK1, the inwardly rectifying K+ current, was not changed significantly by ISO. 4. The ISO‐induced increase in IK was observed in the presence of CdCl2 (3 x 10(‐4) M), indicating that this effect is not due to a Ca2(+)‐activated potassium current. 5. The reversal potential of IK in normal Ringer solution (‐83 +/‐ 2 mV) was not significantly changed by ISO. Thus, stimulation of the Na(+)‐K+ pump and a consequent hyperpolarizing shift in EK are not responsible for the increase in IK. 6. In the presence of ISO (10(‐6) M) the steady‐state activation curve (n infinity) for IK was consistently shifted to more negative values (by approximately 10 mV). The activation and deactivation kinetics of IK were also changed by ISO: activation was accelerated, deactivation was slowed. These ISO‐induced changes in IK result in an increase in IK at voltages corresponding to the plateau of the action potential. 7. ISO (10(‐6) M) increased ICa dramatically, approximately 6‐fold at 0 mV. At the same time, the time constant of ICa inactivation decreased significantly (34 +/‐ 4 ms control; 23 +/‐ 4 ms ISO). 8. These results confirm that low doses of sympathetic agonists acting via beta‐receptors increase ICa. Relatively high doses of beta‐receptor agonists increase both ICa and IK, but these two effects appear to be generated by different biophysical mechanisms. 9. These dose‐dependent changes in ICa and IK can explain the observed ISO‐induced changes in action potential shape. At doses of approximately 10(‐8) M ICa is increased, resulting in a more depolarized plateau and small lengthening of the action potential.(ABSTRACT TRUNCATED AT 400 WORDS)
Characteristics of voltage‐gated Ca2+ currents in ovine gonadotrophs.
Authors: Mason W T , Sikdar S K
Published: December 2014

1. Voltage‐clamp recordings were obtained from gonadotrophs of the ovine pars tuberalis in dissociated cell culture, utilizing the whole‐cell recording mode of the patch‐clamp technique. 2. The amplitudes of Ca2+ and Ba2+ currents were dependent on the extracellular concentration of divalent cation. 3. Ba2+ tail currents were observed on termination of depolarizing voltage steps. The extrapolated amplitudes of ‘instantaneous’ tail currents increased with membrane depolarization and showed saturation beyond +15 mV. 4. True inactivation of currents occurred in the presence of both external Ca2+ and Ba2+, judged from decrease in tail current amplitudes with progressive increases in duration of the activating voltage pulse. The inactivation process was fitted by a single‐exponential function at membrane potentials below ‐25 mV, while at more depolarized potentials the inactivation was better described by a double‐exponential function. The inactivation time constants decreased with positive shifts in membrane potential favouring a voltage‐dependent inactivation. 5. The half‐value of steady‐state inactivation was observed at ‐40 mV using a two‐pulse protocol. 6. Power spectral analysis of Ba2+ current noise from the steady‐state portion of inward current showed a double Lorentzian fit of the power spectrum. 7. Two types of voltage‐activated Ca2+ currents were identified based on their kinetics, voltage dependence, dependence on activation frequency, differential sensitivity to intracellular ATP and cyclic AMP, and to extracellular application of nifedipine. The channels with faster kinetics had a lower activation threshold (‐50 mV) and the amplitude of the current was sensitive to clamping frequency. 8. From ensemble noise analysis of mean maximal inward current, single‐channel amplitude of about 1 pA was estimated in 50 mM‐Ba2+.
Sensations evoked by intraneural microstimulation of C nociceptor fibres in human skin nerves.
Authors: Ochoa J , Torebjörk E
Published: December 2014

1. Seventy‐one C polymodal nociceptors supplying glabrous and hairy skin in limbs of awake human volunteers were identified on the basis of cutaneous stimulus‐response characteristics recorded intraneurally by microneurography (MNG). The large majority of such units were primarily detected during intraneural microstimulation (INMS) on the basis of subjective quality and cutaneous localization of evoked painful sensation. Electrophysiological studies were supplemented with rigorous psychophysical testing during microstimulation delivered at intraneural C recording sites. 2. The conduction velocity of single C nociceptor units could be shown to become transiently slowed following repetitive INMS at threshold intensity for conscious sensation. Such ‘marking’ witnessed that particular C units, identified by recording, had been effectively activated during INMS and psychophysical testing. 3. Cognitive attributes of sensations evoked from C recording sites by INMS at threshold intensity for perception were estimated psychophysically for subjective quality, temporal attributes and localized projection. There was remarkable matching of physiological unit type (C polymodal nociceptor) with subjective quality of evoked sensation (dull or burning pain). Further, there was remarkable spatial matching of receptive field of given C nociceptors with projected field of the pain sensation evoked from the C recording site by INMS delivered at threshold intensity for conscious sensation. 4. Dissociated A nerve fibre blocks caused by compression‐ischaemia did not abolish the sensation of burning pain projected to hairy skin, evoked by INMS delivered at C recording sites. 5. While the double matching of (a) subjective quality and spatial localization with (b) objective physiological unitary type and receptor location, coupled with the results of A blocks, provide evidence that C nociceptor fibres can be fairly selectively activated during INMS, the results also attest that C polymodal nociceptors from human skin evoke delayed dull or burning pain, accurately projected to a defined locus in skin, even after spatial summation is reduced to a minimum.
Mixing and Entrainment Characteristics in Circular Short Ejectors
Authors: Hyun Im Ju , Jin Song Seung
Published: December 2014

Analytical and experimental investigations have been conducted to characterize the performance of “short” ejectors. In short ejectors, the core of primary (motive) flow still exists at the mixing duct exit, and nonuniform mixed flow is discharged from the mixing duct. Due to incomplete mixing, short ejector pumping performance is degraded and cannot be predicted by the existing “long” ejector models. The new analytical short ejector model presented in this paper is based on the control volume analysis and jet expansion model. The secondary (entrained) flow velocity and the corresponding shear layer (between the primary and the secondary flows) growth rate variations along the mixing duct are taken into account. In addition, measurements have been made in ejectors with length ratios (LRs) of two and three for an area ratio (AR) of 1.95; and a LR of two for an AR of 3.08. Velocity profiles at the mixing duct inlet and exit, and static pressure distribution along the mixing duct have been measured with pitot probes and pressure taps. All of the tests have been carried out at a Reynolds number of 420,000. Comparison shows that the new ejector model can accurately predict flow characteristics and performance of short ejectors. For all of the test cases, the velocity profiles at the mixing duct inlet and exit are well predicted. Also, both predictions and measurements show pumping enhancement with increasing mixing duct length. The pumping enhancement is due to the increase in the static pressure difference between the mixing duct inlet and atmosphere as the mixing duct is lengthened. Furthermore, both measured and predicted static pressure distributions along the mixing duct show a kink. According to the analysis, the kink occurs when the outer shear layer reaches the mixing duct wall, and the secondary flow velocity decreases along the mixing duct upstream of the kink and increases downstream of the kink. Thus, the new ejector model can accurately predict not only the integral performance but also different mixing regimes in short ejectors.
Conditional Extended Kalman Filter for Battery Model Parameter Identification
Authors: Li Yonghua , Wang Xu
Published: December 2014

In this paper a conditional Extended Kalman Filter is applied to battery model parameter and state estimations. A decision logic, based on battery input and output data, is designed such that parameter update is stopped when persistent excitation conditions are not met. Persistent excitation conditions are represented by a simpler, easier to implement set of calibrations. Examples, both from desktop simulation, and real world vehicle testing, have been provided to support the validity of this algorithm. The proposed strategy has been successfully deployed in production FHEV/PHEV vehicles.
Nonlinear Dynamic Analysis of EEG Using a Stochastic Duffing-van der Pol Oscillator Model
Authors: Ghorbanian Parham , Ramakrishnan Subramanian , Whitman Alan , Ashrafiuon Hashem
Published: December 2014

In this work, we model electroencephalography (EEG) signals as the stochastic output of a double Duffing - van der Pol oscillator networks. We develop a novel optimization scheme to match data generated from the model with clinically obtained EEG data from subjects under resting eyes-open (EO) and eyes-closed (EC) conditions and derive models with outputs that show very good agreement with EEG signals in terms of both frequency and information contents. The results, reinforced by statistical analysis, shows that the EEG recordings under EC and EO resting conditions are distinct realizations of the same underlying model occurring due to parameter variations. Furthermore, the EC and EO EEG signals each exhibit distinct nonlinear dynamic characteristics. In summary, it is established that the stochastic coupled nonlinear oscillator network can provide a useful framework for modeling and analysis of EEG signals that are recorded under variety of conditions.
Active Control of Four-Bar Tensegrity-Membrane Systems
Authors: Yang Shu , Sultan Cornel
Published: December 2014

Tensegrity-membrane systems are deployable structures that can be utilized in space applications such as solar sails and radar systems. This work addresses the control design for four-bar tensegrity-membrane systems. The tendons act as actuators, and the system can be controlled by changing the rest-lengths of the tendons. Lagrange’s method is used to model the system, and the equations of motion are expressed as a set of differential-algebraic equations (DAE). For control design, the equations of motion of the system in the DAE form are converted into the form of second order ordinary differential equations based on coordinate partitioning and coordinate mapping. Since the number of control inputs is less than the number of state variables, these systems can be classified as underactuated nonlinear systems. The collocated partial feedback linearization (PFL) technique is implemented to design a nonlinear controller. Simulation results of the closed-loop system under initial perturbation are presented, and the performance of the controller is discussed.
Indirect Adaptive Robust Controller Design for Drilling Rotary Motion Control
Authors: Bu Fanping , Dykstra Jason
Published: December 2014

This paper presents the design and simulation of an indirect adaptive robust controller (IARC) for the rotatory drilling motion used in oil and gas exploration operations. To eliminate drill string vibrations, such as stick-slip, and achieve better control of drill bit rotating motion, an IARC controller was designed to compensate nonlinear friction torque directly and address system uncertainties during drilling. Simulation results are presented to illustrate the effectiveness of the designed IARC controller.
Fault Prognosis of Roller Bearings Using the Adaptive Auto-Step Reinforcement Learning Technique
Authors: Afshari Hamed Hossein , Al-Ani Dhafar , Habibi Saeid
Published: December 2014

This paper presents the implementation of a new adaptation algorithm to model the crack propagation of roller bearings and to predict their Remaining Useful Life (RUL). The developed algorithm is designed based on the adaptive auto-step reinforcement-learning method combined with a crack propagation model. The advantage of this algorithm is that it is now able to not only estimate the defect growth rate online, but also to predict the RUL of a roller bearing element. The presented defect propagation model incorporated in this work is an extension to the Paris’s formula that is well known in the fracture mechanics community. Further, a new adaptive filtering technique, referred to as the auto-step, is presented in this paper and is used to estimate the parameters of the crack propagation model in real-time. The prognosis structure is first compares values of both the predicted and the measured defect sizes, and then, tunes the parameters of the crack propagation model. Simulation results obtained by the auto-step method are then compared with results obtained by the Recursive Least Square (RLS) adaptive filter. The proposed prognosis strategy is distinct itself from other approaches in terms of obtaining higher accuracy as well as faster convergence rate.
Stochastic Oscillator Model of EEG Based on Information Content and Complexity
Authors: Ghorbanian Parham , Ramakrishnan Subramanian , Ashrafiuon Hashem
Published: December 2014

In this study, a stochastic Duffing - van der Pol coupled two oscillator system is designed to produce output matching the information content, complexity measure, and frequency content of actual electroencephalography (EEG) signals. This is achieved by deriving the oscillator model parameters and noise intensity using an optimization scheme whose objective is to minimize a weighed average of errors in sample entropy, Shannon entropy, and powers of the major brain frequency bands. The signals produced by the optimal model are then compared with the EEG signal using phase portrait reconstruction. The study shows that the model can effectively reproduce signals that match EEG recorded under different brain states with respect to multiple metrics.
A Two-Phase Framework for Linear Permanent-Magnet Machines and Multi-Axis Stages With Magnetic Levitation
Authors: Nguyen Vu Huy , Kim Won-jong
Published: December 2014

This paper presents the electromagnetic design and experimental validation of a new framework for linear permanent-magnet (PM) machines with magnetic levitation. In this framework, a single forcer, which can generate two force components in two perpendicular directions, consists of a stationary Halbach magnet array and two Lorentz coils with a phase difference of 90° or 270°. Any number of coil pairs can be attached on the same moving frame to work with a common magnet array or matrix, forming a linear or planar permanent-magnet motor. Key advantages of this framework are simple force calculation, linear force, and a reduced number of coils for force generation and allocation in multi-axis positioners. The proposed framework effectively allows for decoupled dynamics of multi-axis stages, simplifying their linear controller design and real-time implementation. This framework is experimentally verified by a high-precision 6-degree-of-freedom (6-DOF) magnetically–levitated (maglev) stage.
Sensing User Input on a Human Exoskeleton Device
Authors: Perry Bradley W. , Kazerooni Homayoon
Published: December 2014

To practically help those with limited mobility disorders, human exoskeletons need to be intelligent devices that not only guide the pilot along a particular gait but do so in a manner that is comfortable to the pilot and sensitive to pilot intent. This paper proposes sensing the user’s intent and then weighing gait tracking with amplifying the user’s input. To do so, this method utilizes a strain gauge to sense user intent, a Kalman filter to estimate the user’s input to the system, and an LQ-based controller that will weigh pure amplification of the user’s forces with tracking the ideal gait trajectory. This method is implemented in a simulation that showed the user’s input can be estimated under reasonable noise assumptions. This estimate is then supplied to the LQ-based controller with cost function weights on tracking, amplification, and motor input. Varying these weights changes the motor input torque profile to be smoother for the pilot’s comfort or better for tracking performance. These weights can be used to simply and quickly personalize the exoskeleton’s effect for each pilot. The LQ controller is found to yield a smooth torque profile to the user when compared to a PD trajectory tracking controller.
Energy Equipartition Control for Geospatial Cyber-Physical Network Systems
Authors: Zeng Xianlin , Hui Qing
Published: December 2014

This paper develops three novel hybrid control techniques addressing fast energy equipartition for cyber-physical network systems, and discusses the future application of the proposed approaches to power network systems. The proposed hybrid distributed controller architectures are designed to mimick the dynamic behavior of thermodynamic systems to achieve the robust performance of cyber-physical network systems. The proposed controller architectures are constructed in such a way that each controller has a one-directional energy transfer from a plant to itself, and exchanges energy with its neighboring controllers. Energy-based resetting laws and power-based resetting laws are utilized in the hybrid controllers. Then, the hybrid control techniques are applied to power network systems, and simulation studies are carried out to show the efficacy of the proposed approaches.
Electrospinning Nanofibers: Measurements, Dynamics, and Control Strategy Development
Authors: Cai Yunshen , Gevelber Michael
Published: December 2014

Electrospinning produces submicron fibers for a variety of applications using a wide range of polymers. Achieving the desired fiber diameter, maximizing productivity, and minimizing variation are important production objectives. This paper addresses several important areas needed to develop a general electrospinning control approach including: developing a correlation between measurements, process conditions, and the resulting fiber diameter, developing a method to determine an operating regime that meets manufacturing objectives, and identifying process dynamics for controller design.
Contaminant Detection and Localization With Design of Experiment and Response Surface Methodology
Authors: Liu Zhenyi , Smith Philip , Hui Qing
Published: December 2014

The spread of contaminant into the environment due to a high volume of leakage from point sources is a very real threat in the modern world. Since the contaminant can often be dangerous to human operators, multiple robotic agents equipped with suitable sensors are playing an increasingly important role in the so-called contaminant detection problem than before. This paper proposes a contaminant detection methodology which can not only locate the (possibly multiple) source of the contaminant, but also estimate the intensity in an environment evolving over both space and time. The methods can deal with measurement noise and do not need any gradient information.
A New Model-Free Stability-Based Cognitive Control Method
Authors: Nowak Xi , Söffker Dirk
Published: December 2014

This contribution considers a new realization of the cognitive stabilizer, which is an adaptive stabilization control method based on a cognition-based framework. It is assumed, that the model of the system to be controlled is unknown. Only the knowledge about the system inputs, outputs, and equilibrium points are the preliminaries assumed within this approach. A new improved realization of the cognitive stabilizer is designed in this contribution using 1) a neural network estimating suitable inputs according to the desired outputs, 2) Lyapunov stability criterion according to a certain Lyapunov function, and 3) an optimization method to determine the desired system outputs with respect to the system energy. The proposed cognitive stabilizer is able to stabilize an unknown nonlinear MIMO system at arbitrary equilibrium point of it. Suitable control input can be designed automatically to guarantee the stability of motion of the system during the whole process although the changing of the system behavior or the environment. Numerical examples are shown to demonstrate the successful application and performance of this method.
A Wireless Human Motion Monitoring System Based on Joint Angle Sensors and Smart Shoes
Authors: Zhang Wenlong , Tomizuka Masayoshi , Byl Nancy
Published: December 2014

In this paper, a wireless human motion monitoring system based on joint angle sensors and smart shoes is introduced. An inertial measurement unit (IMU) is employed in a joint angle sensor to estimate the lower-extremity joint rotation in three dimensions. Four pressure sensors are embedded in a smart shoe to measure the distribution of ground contact forces (GCFs). Zig-bee and Bluetooth modules are combined with the joint angle sensors and smart shoes respectively to make the whole system wireless. It is shown that gait phase and step length can be calculated based on the raw sensor data for gait analysis. To provide visual feedback to the users, with the consent of Apple Inc., an user interface application is developed on an iPad. Experimental results are obtained from both a healthy subject and a stroke patient for comparison. Some discussions are made about the potential use of this system in a clinical environment.
Adaptive Sliding Mode Spacecraft Attitude Control
Authors: Wang Yizhou , Chen Xu , Tomizuka Masayoshi
Published: December 2014

An adaptive sliding mode spacecraft attitude controller is derived in this paper. It has the advantage of not requiring knowledge of the inertia of the spacecraft, and rejecting unexpected external disturbances, with global asymptotic position and velocity tracking. The sliding manifold is designed using optimal control analysis of the quaternion kinematics. The sliding mode control law and the parameter adaptation law are designed using Lyapunov stability. Numerical simulations are performed to demonstrate both the nominal and the robust performance.
Steady-State Marginalized Particle Filter for Attitude Estimation
Authors: Wang Yizhou , Wai Dennis , Tomizuka Masayoshi
Published: December 2014

A marginalized particle filter (MPF) is designed for attitude estimation problem. Unit quaternions are used to parameterize rotations. The linear structure in the gyroscope bias dynamics enables us to completely decouple its evolution from quaternion particles. We further show that the linear part of the proposed MPF reaches a steady state, similar to what Kalman filter does for controllable and observable linear stochastic systems. Although the steady-state MPF is similar to the particle filter in structure, it has two advantages: (i) the theoretical superiority of marginalizing linear substructure, and (ii) the reduction in total computational time. Numerical simulations are performed to demonstrated the performance of the proposed filter.
A Novel Gait and Foot Slip Detection Algorithm for Walking Robots
Authors: Okita Nori , Sommer H. J.
Published: December 2014

A novel gait and slip detection algorithm for walking robots using an inertial measurement unit was developed. An unscented Kalman filter was formulated with a simple dynamic model as a block on a slope without translations. Considerable prediction errors resulted when unmodeled dynamics (i.e., translation) occurred. These prediction errors were used in a binary Bayes filter to estimate the probability of gait and slip states. A proof of concept experiment was conducted with a monopedal walker under three floor conditions (nonslip, poly, and poly-oil) and three orientations (flat, uphill, and downhill). Realtime and offline detection at 100 Hz were successful. Continuous gait cycles were detected in proper order. Slip detection was successful except for very mild slips involving small jerk. The proposed algorithm provided a robust gait and slip detection method with a single set of parameters without knowledge of floor conditions and inclinations.
Automated Modeling and Mode Screening for Exhaustive Search of Double-Planetary-Gear Power Split Hybrid Powertrains
Authors: Zhang Xiaowu , Peng Huei , Sun Jing , Li Shengbo
Published: December 2014

Double Planetary Gear (PG) power-split hybrid powertrains have been used in production vehicles from Toyota and General Motors. Some of the designs use clutches to achieve multiple operating modes to improve powertrain operation flexibility and efficiency at the expense of higher complexity. In this paper, an automatic modeling and screening process is developed, which enables exhaustively search through all designs with different configurations, clutch locations and operating modes. A case study was conducted based on the configuration used in the model year 2010 Prius and Camry hybrids. It was found that by adding clutches, fuel economy can be improved significantly for plug-in hybrid (charge depletion) operations.
Actuator Fault Sensitivity Analysis for In-Wheel Motor Electric Ground Vehicle With Active Steering System
Authors: Zhang Guoguang , Zhang Hui , Wang Junmin , Yu Hai , Graaf Roger
Published: December 2014

This paper presents the sensitivity analyses on vehicle motions with regard to faults of in-wheel motors and steering motor for an electric ground vehicle (EGV) with independently actuated in-wheel rear motors. Based on the vehicle model, direct method is applied to determine, to what extent, that different actuator faults affect vehicle motions such as the longitudinal velocity, lateral velocity, and yaw rate. For motion indices like vehicle sideslip angle and longitudinal acceleration, linearizations around equilibrium points are conducted and their sensitivities to actuator faults are analyzed. Results show that all mentioned vehicle motions are more sensitive to the fault of steering motor than that of in-wheel motors. In addition, the effects on vehicle motions due to four types of faults, i.e. additive, loss-of-effectiveness, time-varying-gain and stuck-at-fixed-level faults, are examined through CarSim® simulations and vehicle experiments under a representative maneuver.
Information Sharing via Active Sensing in a Multi-Agent System Inspired by Echolocating Bats
Authors: Lin Yuan , Abaid Nicole
Published: December 2014

Current models for multi-agent systems almost exclusively employ sensory modalities such as vision where agents passively receive information from the environment. Active sensing, defined as acquiring environmental information using self-generated signals, allows widespread sharing of sensory information among agents and thus gives rise to more complex interactions within engineered multi-agent systems using radar or sonar, for example. In nature, bat swarms are animal groups that successfully employ active sensing with each individual broadcasting echolocation pulses in the environment and responding to echoes. Bats flying in groups may cope with the dense sound environment through their behavior; one hypothesized strategy is the cessation of echolocation pulses in the presence of peers and “eavesdropping”, which has been demonstrated in controlled laboratory settings. In this work, we build a self-propelled-particle model with each agent avoiding obstacles in three dimensions by emitting echolocation pulses of a unique frequency. We implement a bat-inspired rule of eavesdropping to take advantage of information sharing via active sensing while reducing the energy expenditure of the group. Through a simulation study, we show that agents indeed capitalize on peers’ pulses and echoes for obstacle avoidance and we find a maximum of this effect for a set of model parameters which relate to the domain size.
Fault Detection and Isolation for Lithium-Ion Battery System Using Structural Analysis and Sequential Residual Generation
Authors: Liu Zhentong , Ahmed Qadeer , Rizzoni Giorgio , He Hongwen
Published: December 2014

This paper presents a systematic methodology based on structural analysis and sequential residual generators to design a Fault Detection and Isolation (FDI) scheme for nonlinear battery systems. The faults to be diagnosed are highlighted using a detailed hazard analysis conducted for battery systems. The developed methodology includes four steps: candidate residual generators generation, residual generators selection, diagnostic test construction and fault isolation. State transformation is employed to make the residuals realizable. The simulation results show that the proposed FDI scheme successfully detects and isolates the faults injected in the battery cell with cooling system at different times. In addition, there are no false or missed detections of the faults.
LMI Control Design With Input Covariance Constraint for a Tensegrity Simplex Structure
Authors: Al-Jiboory Ali Khudhair , Zhu Guoming , Sultan Cornel
Published: December 2014

The Input Covariance Constraint (ICC) control problem is an optimal control problem that minimizes the trace of a weighted output covariance matrix subject to multiple constraints on the input (control) covariance matrix. ICC control design using the Linear Matrix Inequality (LMI) approach was proposed and applied to a tensegrity simplex structure in this paper. Since it has been demonstrated that the system control variances are directly associated with the actuator sizes for a given set of ℒ2 disturbances, the tensegrity simplex design example is used to demonstrate the capability of using the ICC controller to optimize the system performance in the sense of output covariance with a given set of actuator constraints. The ICC control design was compared with two other control design approaches, pole placement and Output Covariance Constraint (OCC) control designs. Simulation results show that the proposed ICC controllers optimize the system performance (the trace of a weighted output covariance matrix) for the given control covariance constraints whereas the other two control design methods cannot guarantee the feasibility of the designed controllers. Both, state feedback and full-order dynamic output feedback controllers have been considered in this work.
Compensation of HVAC System Nonlinearities Using Cascaded Control Architecture
Authors: Price Christopher R. , Rasmussen Bryan P.
Published: December 2014

Research into heating, ventilation, and air conditioning systems has shown that coordinating building climate control leads to large energy savings. However, most analyses have assumed linear dynamics not reflective of actual systems. Using a cascaded control architecture, this linear behavior can be recovered, allowing for maximum energy savings to be realized. Case studies on variable air volume, hydronic radiator, and terminal fan controlled systems demonstrate the broad application and benefits of this approach. Also, because of the architectural simplicity and lack of required a priori knowledge of system performance or characteristics, the cascaded controller can be implemented immediately in the HVAC community.