bluuebunny/crossref_metadata_2025 huggingface dataset:
Pharmacological and anatomical separation of calcium currents in rat dentate granule neurones in vitro.
Authors: Blaxter T J , Carlen P L , Niesen C
Published: December 2014

1. Rat dentate granule neurones in hippocampal slices were voltage‐clamped at 21‐23 degrees C using CsCl‐filled microelectrodes. The perfusate contained TTX and K+ channel blockers to isolate pharmacologically inward Ca2+ currents. 2. From hyperpolarized holding potentials of ‐65 to ‐85 mV, depolarizing test potentials to between ‐50 and ‐40 mV elicited a transient (100‐200 ms) low‐threshold (TLT) current which was also elicited from more depolarized holding potentials following hyperpolarizing voltage steps of ‐40 mV or greater. 3. Larger depolarizing steps from a hyperpolarized holding potential triggered a large (2‐6 nA), transient high‐threshold (THT) inward current, rapidly peaking and decaying over 500 ms, followed by a sustained inward current component. 4. At depolarized holding potentials (‐50 to ‐20 mV), the THT current was apparently inactivated and a sustained high‐threshold (SHT) inward current was evident during depolarizing voltage steps of 10 mV or more. 5. From hyperpolarized holding potentials with depolarizing voltage steps of 10‐30 mV, most neurones demonstrated a small‐amplitude, sustained low‐threshold (SLT) inward current with similar characteristics to the SHT current. 6. Zero‐Ca2+ perfusate or high concentrations of Ca2+ channel blockers (Cd2+, Mn2+ or Ni2+) diminished or abolished all inward currents. 7. Repetitive voltage step activation of each current at 0.5 Hz reduced the large THT current to less than 25% of an unconditioned control current, reduced the SHT current by 50%, but had little effect on the TLT current. 8. A low concentration of Cd2+ (50 microM) blocked the THT and SHT currents with little effect on the TLT current. Nimodipine (1 microM) attenuated the SHT current. Ni2+ (100 microM) selectively attenuated the TLT current. 9. In low‐Ca2+ perfusate, high concentrations of Ca2+ (10‐15 mM), focally applied to different parts of the neurone, increased the THT current when applied to the dendrites, the SHT current when applied to the soma and the TLT current at all locations. Conversely, in regular perfusate, Cd2+ (1‐5 mM), focally applied to the dendrites decreased the THT current and somatic applications decreased the SHT current. The TLT current was diminished regardless of the site of Cd2+ application. 10. These results suggest the existence of three different Ca2+ currents in dentate granule cells separable by their activation and inactivation characteristics, pharmacology and site of initiation.
Cardio‐respiratory responses to cool ambient temperature differ with sleep state in neonatal lambs.
Authors: Berger P J , Horne R S , Walker A M
Published: December 2014

1. Responses to cool ambient temperature were tested with reference to the sleep‐wakefulness cycle in six chronically instrumented newborn lambs which were exposed to warm (20‐25 degrees C) and cool (10‐15 degrees C) ambient temperatures (Ta) in fifteen studies. 2. We measured cardio‐respiratory variables (cardiac output, heart rate, stroke volume, arteriovenous O2 difference and O2 consumption) together with body temperature (Tb) during behavioural states of quiet wakefulness (QW), quiet sleep (QS) and rapid‐eye‐movement sleep (REM). 3. In cool Ta, significant increases (P less than 0.05) occurred in cardiac output, O2 uptake and O2 consumption in QW (10 +/‐ 3%, 23 +/‐ 4% and 35 +/‐ 6%, respectively, mean +/‐ S.E.M.) and QS (12 +/‐ 3%, 21 +/‐ 7% and 35 +/‐ 8%, respectively), but these responses were absent in REM. Increases in heart rate (6 +/‐ 2%) and stroke volume (6 +/‐ 3%) were present during QS, but not during REM. 4. In REM, Tb was dependent upon the prevailing Ta, increasing in the warm Ta and tending to decrease in the cool Ta. 5. In cool Ta, REM sleep epochs were shorter and more frequent with no changes in total REM time. These changes were not seen in QS. 6. Thus, the behavioural state determines both the thermogenic and the associated cardio‐respiratory responses to cool stress in lambs. The consequences of disrupted thermogenesis during REM sleep include dependence of Tb upon the prevailing ambient temperature, and abbreviation of the REM epoch by arousal, possibly as a defence against falls in Tb in cool Ta.
Frequency‐dependent depression of inhibition in guinea‐pig neocortex in vitro by GABAB receptor feed‐back on GABA release.
Authors: Deisz R A , Prince D A
Published: December 2014

1. The mechanisms involved in the lability of inhibition at higher frequencies of stimulation were investigated in the guinea‐pig in vitro neocortical slice preparation by intracellular recording techniques. We attempted to test the possibility of a feedback depression of GABA on subsequent release. 2. At resting membrane potential (Em, ‐75.8 +/‐ 5.2 mV) stimulation of either the pial surface or subcortical white matter evoked a sequence of depolarizing and hyperpolarizing synaptic components in most neurones. An early hyperpolarizing component (IPSPA) was usually only obvious as a pronounced termination of the EPSP, followed by a later hyperpolarizing event (IPSPB). Current‐voltage relationships revealed two different conductances of about 200 and 20 nS and reversal potentials of ‐73.0 +/‐ 4.4 and ‐88.6 +/‐ 6.1 mV for the early and late component, respectively. 3. The conductances of IPSPA and IPSPB were fairly stable at a stimulus frequency of 0.1 Hz. At frequencies between 0.5 and 2 Hz both IPSPs were attenuated with the second stimulus and after about five stimuli a steady state was reached. Concomitantly IPSPs were shortened. The average decrease in synaptic conductance between 0.1 and 1 Hz was 80% for the IPSPA and 60% for the IPSPB. At these frequencies the reversal potentials decreased by 5 and 2 mV, respectively; Em and input resistance (Rin) were not consistently affected. 4. The amplitudes of field potentials, action potentials and EPSPs of pyramidal cells were attenuated less than 10% at stimulus frequencies up to 1 Hz, suggesting that alterations in local circuits between the stimulation site and excitatory input onto inhibitory interneurones may play only a minor role in the frequency‐dependent decay of IPSPs. 5. Localized application of GABA produced multiphasic responses. With low concentrations and application near the soma an early hyperpolarization prevailed followed by a depolarizing late component. Brief application of GABA at low frequencies induced constant responses; at higher frequencies, the responses sometimes declined. The current‐voltage relationships of the two GABA responses were similar to each other and to the early IPSP. An apparently fivefold higher conductance was estimated at lower Ems, suggesting that the GABA response had a voltage sensitivity. The slope conductance of IPSPs was decreased by up to 50% for tens of seconds after postsynaptically detectable effects of GABA had dissipated. 6. Application of the GABA uptake inhibitor nipecotic acid (50‐500 microM) reduced the conductance of both components of orthodromically evoked inhibition and shortened the IPSP at low frequencies, but had no additional effects at higher stimulation rates.(ABSTRACT TRUNCATED AT 400 WORDS)
Effects of fatigue and reduced intracellular pH on segment dynamics in ‘isometric’ relaxation of frog muscle fibres.
Authors: Curtin N A , Edman K A
Published: December 2014

1. Longitudinal movements of marked segments of single fibres from the anterior tibialis muscle were recorded during tetanus and relaxation under isometric (fixed‐end) conditions. 2. During relaxation, shortening and lengthening of different segments occurred simultaneously, starting at about the same time as the end of the linear fall of force (shoulder on the force record). 3. Variations in intracellular pH, measured with pH‐sensitive microelectrodes, along the length of fibres were not statistically significant, and are unlikely to be responsible for the non‐uniform behaviour of different segments. 4. As expected from earlier studies, both fatigue (produced by increasing tetanus duration or decreasing the time between tetani) and intracellular acidification (produced by raised extracellular CO2), reduced the tetanus force and prolonged the linear phase of force decline in relaxation. Each treatment delayed the start and markedly reduced the amount of segment movement in relaxation. 5. Fatigue and intracellular acidification have a smaller effect on force during stretching than on force produced under isometric conditions. This may contribute to making the segments behave in a more uniform way during relaxation under these conditions. 6. Changes in the Ca2+ uptake mechanisms are also discussed as possible causes for the changes in segment behaviour in relaxation.
Desensitization to cytoplasmic Ca2+ and Ca2+ sensitivities of guinea‐pig ileum and rabbit pulmonary artery smooth muscle.
Authors: Himpens B , Matthijs G , Somlyo A P
Published: December 2014

1. The free cytoplasmic Ca2+ concentration [( Ca2+]i) was measured in the tonic rabbit pulmonary artery and the phasic ileum smooth muscle. 2. Force development and [Ca2+]i were determined during either cumulative or non‐cumulative additions of [Ca2+]o to smooth muscles depolarized with 140 mM‐K+ solutions. 3. The level to which [Ca2+]i declined in Ca2+‐free, 140 mM‐K+ solutions was significantly lower in the ileum (40 +/‐ 4 nM) than in pulmonary artery (77 +/‐ 5 nM) smooth muscle. 4. The level of [Ca2+]i reached during non‐cumulative superfusion with 10 microM and 1 mM [Ca2+]o was higher in the pulmonary artery than in the ileum. 5. The force level reached for a given [Ca2+]i was also higher in the pulmonary artery than in the ileum. 6. During maintained depolarization there was a marked decrease in the sensitivity of ileum smooth muscle tension to [Ca2+]i. 7. We conclude that significant differences exist in the Ca2+ sensitivity of the regulatory/contractile apparatus among different smooth muscles; the lower sensitivity of depolarized ileum than pulmonary artery to [Ca2+]o is due to both differences in Ca2+ metabolism and in the Ca2+ sensitivity of the regulatory contractile system. We suggest that these two mechanisms also contribute to the decline in force during a phasic K+ contracture, and that desensitization to [Ca2+]i contributes to the decline of the K+ contracture in the ileum.
The action of ryanodine on rat fast and slow intact skeletal muscles.
Authors: Fryer M W , Lamb G D , Neering I R
Published: December 2014

1. The action of ryanodine on force development of bundles dissected from rat extensor digitorum longus (EDL) and soleus muscles has been examined. 2. Ryanodine (100‐5000 nM) irreversibly depressed twitch and tetanic tension of both muscle types in a dose‐related manner. 3. At concentrations above 250 nM, ryanodine induced a slowly developing, dose‐dependent contracture which could not be blocked by 5 mM‐Co2+. Increasing the stimulation rate or decreasing the oxygenation of the preparation accelerated the rate of contracture development while the total removal of extracellular Ca2+ was required to prevent it. 4. Following the relaxation of the initial contracture (IC) in Ca2+‐free solution, a second type of contracture (SC) could be induced by the readdition of Ca2+. This contracture differed from IC in that it was dependent on Ca2+ in the millimolar range and was prevented by 5 mM‐Co2+. Both IC and SC were relaxed by perfusion with Ca2+‐free, EGTA‐containing solution. 5. Subcontracture doses of ryanodine (100 nM) markedly potentiated caffeine contractures of both muscle types. 6. Asymmetric charge movement in EDL fibres was recorded with the Vaseline‐gap technique. The amount of charge moved near threshold was virtually unaffected by the presence of 10 microM‐ryanodine over the time examined. 7. The results are consistent with the suggestion that ryanodine locks the calcium release channels of the sarcoplasmic reticulum (SR) in an open subconductance state with reduced conductance. It appears that lowering the external calcium concentration might still inactivate the release channels after they have been blocked open by ryanodine, possibly by an effect on the T‐tubular voltage sensor.
Acetylcholine‐gated and chloride conductance channel expression in rat muscle membrane.
Authors: Heathcote R D
Published: December 2014

1. During the differentiation of skeletal muscle, there is a synchronized expression of a number of muscle‐specific proteins including the acetylcholine‐gated ion channel (AChR). Another muscle‐specific ion channel, responsible for chloride conductance, was shown to be expressed in an anticoordinate fashion to AChR. An organ culture system for rat lumbrical muscles was developed to manipulate the expression of these two ion channels. 2. Denervation induced a change in expression of both channels that was mimicked in culture and reversed by direct electrical stimulation. 3. The time course of the disappearance of both channels was similar and started immediately after denervation (chloride conductance) or stimulation (AChR). The time course of the appearance of AChR was delayed several days after denervation and culture but chloride conductance increased immediately upon stimulation. 4. The loss of chloride conductance in muscle cultured in cycloheximide exhibited first‐order kinetics, providing an estimate of the half‐life (2.3 days) for the chloride conductance channel. This resembled the disappearance of chloride conductance in normal medium, suggesting that synthesis of this channel ceases following denervation. The decrease in chloride conductance characteristic of denervated muscle was not halted by cycloheximide. 5. Changes in chloride conductance presumably alter the intracellular concentration of chloride. The possibility that chloride might regulate the expression of AChRs in skeletal muscle was tested by altering the intracellular concentration of chloride in muscles maintained in organ culture. 6. Denervated muscles, whose intracellular concentration of chloride is elevated, were cultured in medium containing 9 mM‐chloride (low‐Cl‐ medium). AChR expression was reduced by either low‐Cl‐ medium or electrical stimulation. Together, low‐Cl‐ medium and electrical stimulation reduced expression more than either treatment alone. 7. The loss of AChRs in low‐Cl‐ medium was blocked when muscle fibrillation was halted by TTX. 8. When chloride conductance was blocked by 9AC (9‐anthracene carboxylic acid) intracellular chloride was elevated to the levels seen in denervated muscle. The elevated levels of chloride did not prevent the reduction in AChR expression induced by electrical stimulation. 9. The uncoupling of AChR expression and the intracellular concentration of chloride showed that they were not rigidly linked. Chloride affects the expression of AChR indirectly, by altering the activity of muscle cells.
Effect of active pre‐shortening on isometric and isotonic performance of single frog muscle fibres.
Authors: Granzier H L , Pollack G H
Published: December 2014

1. We studied the effects of shortening history on isometric force and isotonic velocity in single intact frog fibres. Fibres were isometrically tetanized. When force reached a plateau, shortening was imposed, after which the fibre was held isometric again. Isometric force after shortening could then be compared with controls in which no shortening had taken place. 2. Sarcomere length was measured simultaneously with two independent methods: a laser‐diffraction method and a segment‐length method that detects the distance between two markers attached to the surface of the fibre, about 800 microns apart. 3. The fibre was mounted between two servomotors. One was used to impose the load clamp while the other cancelled the translation that occurred during this load clamp. Thus, translation of the segment under investigation could be minimized. 4. Initial experiments were performed at the fibre level. We found that active preshortening reduced isometric force considerably, thereby confirming earlier work of others. Force reductions as large as 70% were observed. 5. Under conditions in which there were large effects of shortening at the fibre level, we measured sarcomere length changes in the central region of the fibre. These sarcomeres shortened much less than the fibre's average. In fact, when the load was high, these sarcomeres lengthened while the fibre as a whole shortened. Thus, while the fibre‐length signal implied that sarcomeres might have shortened to some intermediate length, in reality some sarcomeres were much longer, others much shorter. 6. Experiments performed at the sarcomere level revealed that isometric force was unaffected by previous sarcomere shortening provided the shortening occurred against either a low load or over a short distance. However, if the work done during shortening was high, force after previous shortening was less than if sarcomeres had remained at the final length throughout contraction. The correlation between the force deficit and the work done during shortening was statistically significant (P = 0.0001). 7. Interrupting the tetanus for 0.5‐3.0 s did not reverse the effects of shortening on isometric force; at least 5‐10 min of rest were required before force recovered completely. 8. Sarcomeres accelerated during the period of shortening under constant load, indicating that the sarcomeres became progressively stronger. However, the acceleration was less than that predicted from the force‐velocity relation applicable at each of the sarcomere lengths transversed during shortening. 9. Velocity of shortening appeared to be much more sensitive to previous shortening than isometric force. 10. Results obtained with the diffraction method were the same as those obtained with the segment method.(ABSTRACT TRUNCATED AT 400 WORDS)
Axonal morphological changes following impulse activity in mouse peripheral nerve in vivo: the return pathway for sodium ions
Authors: Trigo Diogo , Smith Kenneth J.
Published: December 2014

Key points

Conduction in myelinated axons involves substantial ion movements that must be reversed to restore homeostasis.

The pathway taken by sodium ions returning to their original location and the potential osmotic consequences are currently unknown.

We report striking morphological changes in axons following sustained impulse conduction that appear to result from osmosis and to indicate accumulation of ions in the periaxonal space followed by their release at the paranode.

We conclude that the morphological changes illustrate a hitherto unrecognized part of normal axonal physiology that may also indicate the return pathway for the sodium ions involved in impulse formation.

Myelinated axons can conduct sustained trains of impulses at high frequency, but this involves substantial ion movements that must be reversed to restore homeostasis. Little attention has been paid to the potential osmotic consequences of the ion movements or to the pathway taken by sodium ions returning to their original endoneurial location, given that the axolemmal Na+–K+‐ATPase extrudes these ions into the periaxonal space beneath the myelin rather than into the endoneurium. Serial confocal imaging of fluorescent axons conducting at sustained physiological frequencies in vivo has revealed surprising morphological changes that may illuminate these problems. Saphenous nerves and spinal roots of anaesthetized transgenic mice expressing axoplasmic yellow fluorescent protein were stimulated electrically or pharmacologically (veratridine). Within 2 h, the axon herniated on one or both sides of the nodal membrane, displacing the paranodal myelin and widening the nodal gap. The herniated axoplasm became directed back towards the internode, forming a ‘cap’ up to 30 μm long. Concurrently, the fluid in the expanded periaxonal space accumulated into droplets that appeared to travel to the paranode, where they escaped. No such alterations occurred in axons treated with sodium channel or Na+–K+‐ATPase inhibitors. Remarkably, impulse conduction continued throughout, and all these changes reversed spontaneously over hours or days. The morphological changes were verified ultrastructurally, and occurred in virtually all myelinated axons. The findings appear to reveal an overlooked part of the physiological repertoire of nerve fibres, and here they are interpreted in terms of osmotic changes that may illuminate the pathway by which sodium ions return to the endoneurial space after they have entered the axon during impulse conduction.
Real-Time Battery Model Parameter Estimation With Improved Observability and Robustness
Authors: Lee Tae-Kyung , Anderson Dyche
Published: December 2014

Prediction of battery system responses and capability for next few seconds can provide key information to use battery hardware effectively. The prediction performance will be much improved, when battery models can capture the real battery responses as accurate as possible. Equivalent circuit models (ECMs) have been used for control purpose due to their proper balance between computational efficiency and prediction accuracy. The limitations of ECMs can be efficiently compensated through real-time model parameter estimation. Further enhancement is possible by improving system observability and robustness, specifically effective under low temperature and aggressive driving. This paper proposes an approach to improve the robustness and accuracy in estimating parameters by reformulating ECMs with new parameters. The proposed approach can estimate battery parameters less sensitive to both external disturbance and possible model mismatch under various driving conditions.
Design of a Biomimetic Robotic Fish Controlled by a Touch Screen
Authors: Phamduy Paul , Le Grand Raymond , Porfiri Maurizio
Published: December 2014

Biomimetic robotic fish exhibits have been an attraction for many visitors in informal learning settings. Although these exhibits are entertaining to the visitors, they generally lack interactive components to promote participants’ engagement. Interactivity in exhibits is an increasing trend in public educational venues, and is a crucial factor for promoting science learning among participants. In this work, we propose a novel platform for enhancing participant interaction through a robotic fish controlled by a touch screen device. Specifically, we develop and characterize a robotic fish based on a multi-link design with a pitch and buoyancy control system for three-dimensional biomimetic swimming. Performance tests are conducted to assess the robotic fish speed.
A Mobile Tailgating Detection System for Law Enforcement Surveillance
Authors: Zellmer Tyler J. , Freeman Paul T. , Wagner John R. , Alexander Kim E. , Pidgeon Philip
Published: December 2014

A number of automotive crashes occur each year due to semitrailers following passenger vehicles too closely on interstate highways and secondary roads. This hazardous practice, called tailgating, accounted for over 40% of the 110,000 trailer-passenger vehicle crashes recorded by the National Highway Traffic Safety Administration (NHTSA) in 2010. Tailgating is difficult to detect and document using visual methods and law enforcement agencies must depend on trained officers, whose abilities may be limited. In this paper, a proposed tailgating detection system, mounted to the officer’s patrol vehicle, continuously monitors both passenger and commercial vehicles, as the officer travels down the roadway. A rotating laser range-finding sensor feeds information to a microprocessor that continuously searches for the occurrence of tailgating. A weighting algorithm determines when a tailgating event has definitively occurred to reduce system sensitivity. If an event is detected, the officer is notified with audio and visual cues. A time stamped record including all relevant system information for later use in legal prosecution is also produced. In a virtual case study, the computer generated roadway environment was populated with vehicles of varying velocity and location. The numerical results show that the detection algorithm was able to successfully locate all of the virtual vehicles and accurately determine tailgating events under a number of different simulation conditions.
Estimating Angular Velocity, Attitude Orientation With Controller Design for Three Units CubeSat
Authors: Mao Yao-Ting , Auslander David , Pankow David , Sample John
Published: December 2014

CINEMA (CubeSat for Ions, Neutrals, Electrons and MAgneticfields) will image energetic neutral atoms (ENAs) in the magnetosphere, and make measurements of electrons, ions, and magnetic fields at high latitudes. To satisfy the mission requirements, the three unit cubesat was designed. The spin axis needs to be in the ecliptic normal and the spin rate needs to be 4 rpm. The only power source for CINEMA is the solar panels. External torques are generated by an orthogonal pair of coils acting with the earths magnetic field. This paper provides the control strategy, given the limited power and available sensors, to optimize the convergence of the spin and attitude control.
Adaptive Gain Modified Optimal Torque Controller for Wind Turbine Partial Load Operation
Authors: Ma Zheren , Shaltout Mohamed L. , Chen Dongmei
Published: December 2014

In this paper, an adaptive gain modified optimal torque controller (AGMOTC) is proposed and evaluated for wind turbine partial load operation. An internal PI technique is applied for gain scheduling in order to accelerate the controller response under volatile wind speed while the adaptive searching technique endows the controller with robust convergence to the optimal operating point under plant uncertainties. The light detection and ranging (LIDAR) technology is integrated with the AGMOTC to provide reliable previewed wind speed measurements. Simulations on the NREL 5MW wind turbine show that the LIDAR-enabled AGMOTC outperforms the baseline controller considering the wind energy yield. Additionally, the results show the impact of the proposed controller on the wind turbine fatigue loads.
Pitch Control for Wind Turbine in Yawed Inflow Condition
Authors: Girsang Irving Paul , Dhupia Jaspreet Singh
Published: December 2014

A wind turbine can experience yawed inflow with large yaw misalignment angle during faulty cases, such as faults in the yaw controller/drives, or during extreme atmospheric cases, such as thunderstorm downbursts. In such cases, it is risky for the turbine to continue operation because it is being exposed to large loads. Instead, it is recommended for the turbine to be transited to parking conditions. Currently, most turbine pitch controllers are designed without considering the yaw misalignment angle, correction of which is normally assigned to the yaw controller. This paper investigates the contribution of both a baseline and a proposed collective pitch controllers under yawed inflow conditions. The baseline controller tries to maintain the rated operating condition at an expense of large blade loads. On the contrary, simulation results show that the proposed controller slows down the turbine under the presence of yawed inflow, which helps to park the turbine and reduces the average blade root bending moments.
An Education-Oriented Robotic Anthropomorphic Hand System
Authors: Wu Molei , Kandra Alexander , Shen Xiangrong
Published: December 2014

In this paper, an interactive robotic anthropomorphic hand system is presented, which was developed as an important tool for the educational outreach activities. The robotic anthropomorphic hand incorporates 15 degrees of freedom, providing sufficient mobility in the demonstration of various postures. To increase the attractiveness of the robotic hand, pneumatic muscle actuators are used to drive the robotic hand motion through artificial tendons. The interaction of the robotic hand with a human is enabled with a control device, which allows the human operator to control the hand motion in a natural way. The robotic hand system has been successfully demonstrated in a recent engineering education outreach event, in which over 100 children at all ages operated the robotic hand through the control device.
Adaptive Shift Control for Automatic Transmissions
Authors: Thornton Sarah , Annaswamy Anuradha , Yanakiev Diana , Pietron Gregory M. , Riedle Bradley , Filev Dimitar , Wang Yan
Published: December 2014

Using feedback information of estimates from a model of the hydraulic clutch actuation and measurements from transmission mechanicals, a closed-loop adaptive controller is designed. The controller is structured to update at three different rates: every time instance, every shift, and every n-th number of shifts. Part of the controller is designed to operate in open-loop for the first two regions of the shift until feedback information is available. The open-loop controller adapts within the shift, thus allowing for corrections to the control design to be made during the current shift and in subsequent shifts. The model tuning parameters as well as the return spring pre-load force become the adaptive parameters, which are being adjusted so that the plant matches the model in real-time operation. The control design is validated against a high fidelity simulation model of the transmission hydraulics and mechanicals, as well as experimental data.
Selling Power System Flexibility: Ancillary Service and Real-Time Energy Market Challenges for Storage
Authors: Kirby Brendan
Published: December 2014

Power system operators obtain the flexibility required to reliably balance aggregate generation and load through ancillary service and five-minute energy markets. Market prices are based on the marginal opportunity costs of the generators. This market design works well for generators but inherently fails for storage and demand response, denying these new technologies a fair opportunity to compete and denying the power system access to potentially lower cost reliability resources. Market design or regulatory changes may be required for storage and demand response to be viable ancillary service providers.
Adaptive Observer Design for a Li-Ion Cell Based on Coupled Electrochemical-Thermal Model
Authors: Dey Satadru , Ayalew Beshah , Pisu Pierluigi
Published: December 2014

Accurate real-time knowledge of battery internal states and physical parameters is of the utmost importance for intelligent battery management. Electrochemical models are arguably more accurate in capturing physical phenomena inside the cells compared to their data-driven or equivalent circuit based counterparts. Moreover, consideration of the coupling between electrochemical and thermal dynamics can be potentially beneficial for accurate estimation. In this paper, a nonlinear adaptive observer design is presented based on a coupled electrochemical-thermal model for a Li-ion cell. The proposed adaptive observer estimates distributed Li-ion concentrations, lumped temperature and some electrochemical parameters simultaneously. The observer design is split into two separate parts to simplify the design procedure and gain tuning. These separate parts are designed based on Lyapunov’s stability analysis guaranteeing the convergence of the combined state-parameter estimates. Simulation studies are provided to demonstrate the effectiveness of the scheme.
Chaotic Synchronization of a Class of Nonlinear Systems via Sampled-Data State Feedback
Authors: Yan Song , Qian Chunjiang , Huang Tingwen
Published: December 2014

This paper presents a control strategy for the problem of using sampled-data feedback to synchronize a slave chaotic system with a master chaotic system. The problem is of practical importance since in practice the system states is transmitted as a sampled signal. In order to solve this problem, a sampled-data controller using state feedback is designed to make the tracking error converge to zero. An application to a chaotic Chua oscillator illustrates the effectiveness of the proposed approach.
Experimental Study of a Disturbance Rejection Controller for DFIG Based Wind Energy Conversion Systems
Authors: Tohidi Akbar , Abedinia Oveis , Hajieghrary Hadi , Jayasuriya Suhada
Published: December 2014

We consider a Double Fed Induction Generator (DFIG) based wind energy conversion system with highly nonlinear dynamics and abrupt changes as a test bed for optimally extracting wind energy. Dynamic backstepping is utilized to implement a sliding mode control that combines high order sliding mode control and Multi-Input/Multi-Output (MIMO) backstepping. A novel adaptive estimator is utilized to obtain the maximum active and reactive output power in the presence of stochastic wind velocity profiles which are fed as the reference signals to the algorithm. The controller developed is tuned and evaluated on a simulator of the DFIG based wind power conversion system; which is subsequently implemented on an experimental setup. Experimental results show that the proposed adaptive method outperforms the traditional control methods in terms of robustness and performance.
A Passive Upper Limb Exoskeleton for Macaques in a BMI Study: Kinematic Design, Analysis, and Calibration
Authors: Lu Junkai , Chen Wenjie , Haninger Kevin , Tomizuka Masayoshi
Published: December 2014

Integrating an exoskeleton as an external apparatus for a brain-machine interface has the advantage of providing multiple contact points to determine body segment postures and allowing control to and feedback from each joint. When using macaques as subjects to study neural control of movement, a singularity-free upper limb exoskeleton is required to guarantee safe and accurate tracking of joint angles over all possible range of motion. In addition, the compactness of a design is of more importance considering macaques’ significantly smaller body dimensions than humans’. Proposed in this paper is a 6-degree-of-freedom (DOF) passive upper limb exoskeleton with 4 DOFs at the shoulder complex. System kinematic analysis is investigated in terms of its singularity and manipulability. A real-time data acquisition system is set up, and system kinematic calibration is conducted.
Empirical Modifications to a Phase Space Planner Which Compensates for Low Stiffness Actuation in a Planar, Point-Foot, Biped Robot
Authors: Kim Donghyun , Zhao Ye , Thomas Gray , Sentis Luis
Published: December 2014

This paper presents an extensive experimental study of the first steps of the Hume robot. Hume is an adult sized, 20 kg, series-elastic, point-foot biped robot capable of very fast leg movements. In this study, Hume is constrained to planar motion by a linkage mechanism. We present our application of phase space planning to one, two, and three step walking, the last one over an obstacle. In the implementation, we modified the original theory and added ad-hoc adjustments since the robot could not follow the original theory’s planned walking trajectories despite their theoretical stability. We present a good correlation between the phase space plans and our various experiments, and an analysis of the robot’s final behavior. Overall the planner and ad-hoc modifications allowed us to execute very smooth gaits even over non-flat surfaces but at the same time demonstrated the shortcomings of open loop techniques.
Active Excitation for Battery Model Parameter Identification
Authors: Li Yonghua , Yu Hai
Published: December 2014

In this paper an active excitation approach to battery model parameter identification is discussed. Based on begin-of-life battery model, it is possible to establish a reference parameter table (either fixed, or adaptively learned), and based on such reference parameter table, as well as by analysing battery input signal, active excitation request may be generated. Active excitation is achieved based on maintaining overall torque level with regard to drive input, while adjusting both engine and battery power output (and input). Both conditions for active excitation request, as well as active excitation generation approaches, are presented in detail. Simulation examples using production electrified vehicle battery model parameters and real world drive cycles demonstrate that the proposed approach indeed improves battery model parameter identification accuracy.
Towards the Development of a Low-Cost Minimally Invasive Highly Articulated MRI-Compatible Neurosurgical Robot
Authors: Chowdhury Sagar , Desai Jaydev P. , Diakite Mahamadou , Shin Taehoon , Gullapalli Rao P. , Gupta Satyandra K.
Published: December 2014

Treatment for deeply seated brain tumors requires developing articulated surgical robots that are capable of navigating through narrow spaces with minimal damage to the surrounding tissues. These robots need to be low-cost to make them patient-specific as well as to reduce the health-care cost. This in turn requires lowering the manufacturing costs of the robots so that robots can be discarded after the surgical procedure. Injection molding is a mass manufacturing process for making low-cost plastic parts. We have developed a four degree-of-freedom surgical robot with multiple joints that can be manufactured using injection molding. We have designed a novel compliant mechanism to provide multiple articulated joints. The robot is currently actuated with servo motors located outside the robot that drive the joints using passive cables. Cables are routed through the robot to reduce the cross coupling between the joints and enable independent joint actuation. By detaching the actuation from the robot structure, we have made the robot suitable for operating under continuous magnetic resonance imaging (MRI).
Building Energy Consumption On-Line Forecasting Using System Identification and Data Fusion
Authors: Li Xiwang , Wen Jin
Published: December 2014

Model based control has been proven to have significant building energy saving potentials through operation optimization. Accurate and computationally efficient, and cost-effective building energy model are essential for model based control. Existing studies in this area have mostly been focusing on reducing computation burden using simplified physics based modeling approach. However, creating and identification the simplified physics based model is often challenging and requires significant engineering efforts. Therefore, this study proposes a novel methodology to develop building energy estimation models for on-line building control and optimization using an integrated system identification and data fusion approach. System identification model has been developed based on frequency domain spectral density analysis. Eigensystem realization algorithm is used to generate the state space model from the Markov parameters. Kalman filter based data fusion technique has also been implemented to improve the accuracy and robustness of the model by incorporating with real measurements. A systematic analysis of system structure, system excitation selection as well as data fusion implementation is also demonstrated. The developed strategies are evaluated using a simulated testing building (simulated in EnergyPlus environment). The overall building energy estimation accuracy from this proposed model can reach to above 95% within 2 minutes calculation time, when compared against detailed physics based simulation results from the EnergyPlus model.
Development of a Predictive Collision Risk Estimation Scheme for Mixed Traffic
Authors: Yoo Je Hong , Langari Reza
Published: December 2014

Driven by the emergence of autonomous/semi-autonomous driving technologies, the mixed situation of autonomous vehicles and human drivers is of considerable significance. Toward this end, it is necessary to better understand human driving characteristics so as to predict the actions of the other cars. In this regard, we develop a basic framework for modeling driver behaviors in view of human prediction ability. Through the game theoretic estimation of the counterpart’s behaviors and the corresponding time-evolution of unsafe collision areas, we compute an objective collision model. In turn, we design a human-like predictive perception model on collision with an adjacent vehicle based on the objective collision model and the driver’s subjective level of safety assurance. Since drivers have different safety requirements, the subjective estimate on the collision was designed as a region in which has less safety than the driver’s own safety requirement in the objective probabilistic collision prediction. The region that is subjectively perceived based on the driver’s own safety standard is regarded as a deterministic unsafe region for the driver. That is to say, the subjective perception acts as a collision area with the collision probability of 1 so that the driver should avoid while driving. In our subsequent work, we will address the issue of controller design to avoid the subjective collision estimation.
Design of Rightmost Eigenvalues Using Distributed Delay
Authors: Wei Feng , Orosz Gábor , Ulsoy A. Galip
Published: December 2014

This paper considers the problem of designing the right-most eigenvalues of linear scalar distributed delay systems using two different but complementary methods: generalized stability charts and matrix Lambert W functions. The generalized stability charts are based on generalized Hopf and fold curves that provide important insight into the problem, but the geometry of the curves may become complicated for certain delay distributions. The Lambert W function approach can be applied to general delay distributions, but requires numerical solutions which can suffer from convergence problems. We present simple examples for both approaches.
A Discrete-Time Nonlinear Estimator for an Orthosis-Aided Gait
Authors: Dani Ashwin , Sharma Nitin
Published: December 2014

To achieve automatic operation of a powered orthosis-aided gait or functional electrical stimulation-based walking restoration, accurate estimation of the leg angles is of utmost importance. Various phases of walking last for a short duration of time; thus, an accurate estimator is required with a fast convergence rate. To overcome this challenge, this paper presents a discrete-time nonlinear estimation algorithm to estimate lower-limb angles during an orthosis-aided walking. To this end, we use measurements from 6 degree-of-freedom (DOF) inertial measurement units (IMUs) to estimate the lower limb angles. The estimator is based on a state-dependent coefficient (SDC) linearization or extended linearization of the nonlinear functions. A combination of multiple discrete SDCs is used to compute an optimal gain of the nonlinear estimator based on uncertainty minimization criteria. The nonlinear estimator is robust to uncertainties in system modeling and sensor noise/bias from the IMUs. Monte Carlo simulation studies reveal that the estimator outperforms widely used discrete-time extended Kalman (EKF) filter with respect to average root-mean squared estimation error (RMSE) criteria.
Modeling, Validation, and Vibration Reduction in an Electronic Stethoscope
Authors: Nelson Garrett , Rajamani Rajesh , Erdman Arthur
Published: December 2014

This paper focuses on the influence of noise and vibration on auscultation with a digital stethoscope. Two types of vibrations, namely inputs through the patient chest and disturbances from the physician, influence the auscultation signal. The goal of this work is to reduce the influence of disturbances from the physician on the stethoscope’s digital signal without effectively reducing the coupling between the transducer and the patient’s chest.

A multi-DOF rigid body vibration model consisting of discrete connected components is developed for a digital stethoscope. The model is experimentally validated and its parameters identified by using a thorax simulator and vibration shaker. The introduction of vibration isolation so as to reduce the influence of physician noise on the transducer is then pursued. It is shown that directly introducing soft foam vibration isolation between the transducer and the rest of the stethoscope structure leads to a reduction in coupling with the patient’s chest. On the other hand, if the vibration isolation is introduced between the heavy transducer housing above the transducer and the rest of the stethoscope, then vibration isolation from the physician is achieved with a much less reduction in patient coupling. Experimental results are presented to study the influence of the proposed design changes.
Bang-Bang Trajectory Plans With Dynamic Balance Constraints: Fast Rotational Reconfigurations for RoboSimian
Authors: Byl Katie , Tobler Feodor
Published: December 2014

This paper investigates the problem of rapidly transitioning the pose of a limbed robot while remaining balanced. In particular, we consider motions where rotational accelerations may significantly affect the center of pressure location within a limited base of support. We consider solutions for high-impedance robots with stiff, high-torque actuators that essentially provide accurate, position-control outputs at the joints. We present and compare three methods for generating joint trajectories to achieve fast yet feasible dynamic motions for such systems while maintaining a safety margin for the center of pressure location, toward robust balance. We focus on development of theory and intuition for each method and quantify performance in terms of achievable speed of transition and required joint velocity limits.
Spatial ILC for Multi-Objective Systems
Authors: Lim Ingyu , Barton Kira L. , Hoelzle David J.
Published: December 2014

Iterative learning control is an adaptive, feedforward control technique traditionally used to improve the performance of systems that execute a task repetitively. While generally applied to systems driven by temporal dynamics, there exist applications, such as additive manufacturing, for which spatial dynamics play a particularly important role in determining system behavior. To ensure high fidelity functionality for these application spaces, this paper presents a spatial learning framework for optimizing multiple performance metrics simultaneously. Utilizing a one-step optimization approach enables direct evaluation of design trade-offs over a broad range of potential solutions. The multi-objective spatial learning framework, along with stability and convergence analysis is presented. Simulation results validate the control framework.
Adaptive Predictor-Based Output Feedback Control for a Class of Unknown MIMO Linear Systems
Authors: Nguyen Chuong Hoang , Leonessa Alexander
Published: December 2014

In this paper, the problem of characterizing adaptive output feedback control laws for a general class of unknown MIMO linear systems is considered. Specifically, the presented control approach relies on three components, a predictor, a reference model, and a controller. The predictor is designed to predict the system’s output with arbitrary accuracy, for any admissible control input. Subsequently, a full state feedback control law is designed to control the predictor output to approach the reference system, while the reference system tracks the desired trajectory. Ultimately, the control objective of driving the actual system output to track the desired trajectories is achieved by showing that the system output, the predictor output, and the reference system trajectories all converge to each other.
Automated Modeling of Building HVAC Systems for MPC
Authors: Chintala Rohit H. , Bay Christopher J. , Rasmussen Bryan P.
Published: December 2014

Model predictive control (MPC) offers a tremendous scope in optimizing the consumption of energy by building HVAC systems. This paper presents an automated real-time procedure for the development of linear parametric models of building air-conditioning systems through system identification for the implementation of the MPC algorithms. The procedure is used to decide on the various aspects of system identification such as selecting the model structure, the inputs to the system, the interaction of the systems with their neighbors, and the updating of the model coefficients in real-time. The effectiveness of the procedure is demonstrated by modeling the various components air-conditioning systems of a real building. The root mean squared error was used as a performance metric to gauge the models. The paper also demonstrates that a 15 minute sampling interval is sufficient to model the dynamics of the air-handling unit and the room temperatures, but a faster sampling rate may be required to model the VAV boxes.