Open-loop Technique Research Articles

Dynamics of in vivo power output and efficiency of Nasonia asynchronous flight muscle

By simultaneously measuring aerodynamic performance, wing kinematics, and metabolic activity, we have estimated the in vivo limits of mechanical power production and efficiency of the asynchronous flight muscle (IFM) in three species of ectoparasitoid wasps genus Nasonia (N. giraulti, N. longicornis, and N. vitripennis). The 0.6 mg animals were flown under tethered flight conditions in a flight simulator that allowed modulation of power production by employing an open-loop visual stimulation technique. At maximum locomotor capacity, flight muscles of Nasonia are capable to sustain 72.2 +/- 18.3 W kg(-1) muscle mechanical power at a chemo-mechanical conversion efficiency of approximately 9.8 +/- 0.9%. Within the working range of the locomotor system, profile power requirement for flight dominates induced power requirement suggesting that the cost to overcome wing drag places the primary limit on overall flight performance. Since inertial power is only approximately 25% of the sum of induced and profile power requirements, Nasonia spp. may not benefit from elastic energy storage during wing deceleration phases. A comparison between wing size-polymorphic males revealed that wing size reduction is accompanied by a decrease in total flight muscle volume, muscle mass-specific mechanical power production, and total flight efficiency. In animals with small wings maximum total flight efficiency is below 0.5%. The aerodynamic and power estimates reported here for Nasonia are comparable to values reported previously for the fruit fly Drosophila flying under similar experimental conditions, while muscle efficiency of the tiny wasp is more at the lower end of values published for various other insects.

Compensation of decoherence from telegraph noise by means of an open-loop quantum-control technique

With the growing efforts in isolating solid-state qubits from external decoherence sources, the origins of noise inherent to the material start to play a relevant role. One representative example is charged impurities in the device material or substrate, which typically produce telegraph noise and can hence be modeled as bistable fluctuators. In order to demonstrate the possibility of the active suppression of the disturbance from a single fluctuator, we theoretically implement an elementary bang-bang control protocol, a protocol based on sudden pulses. We numerically simulate the random walk of the qubit state on the Bloch sphere with and without bang-bang compensation by means of a stochastic Schrodinger equation and compare it with an analytical saddle-point solution of the corresponding Langevin equation in the long-time limit. We find that the deviation with respect to the noiseless case is significantly reduced when bang-bang pulses are applied, being scaled down approximately by the ratio of the bang-bang period to the typical flipping time of the bistable fluctuation. Our analysis gives not only the effect of bang-bang control on the variance of these deviations, but also their entire distribution. As a result, we expect that bang-bang control works as a high-pass filter on the spectrum of noise sources. This indicates how the influence of 1 / f noise ubiquitous to the solid-state world can be reduced.

The Effect of Hands-Free Cellular Telephone Conversation Complexity on Choice Response Time in a Detection Task

This paper presents the results of a study addressing the effect of hands-free cellular phone conversation complexity on choice response time in a detection task. The study utilized an open-loop simulation technique to study four different levels of the secondary task of using a hands-free cellular telephone and their effect on the primary task of responding to stimuli presented through a driving scene. Results from the study showed that the inclusion of the secondary task had a significant effect on choice response time. Also, choice response time associated with complex conversations involving visual scanning was found to be significantly different from that when the phone was not used. The implications of the use of hands-free phones are also discussed.

Effects of FDD on open-loop downlink eigen-beamforming in WCDMA mobile communication systems

This work examines the effects of the separation between the carrier frequencies of the uplink and downlink channels due to frequency division duplex on the performance of open-loop downlink beamforming antenna array techniques that make use of eigenvectors as beamformers. The main effects are the de-correlation of the uplink and downlink eigenvectors and the performance loss, both of which are quantified. Also, a simple compensation technique is examined, and is shown to eliminate most of the performance loss.

Physiological Measurement of Insulin Action across a Range of Insulin Sensitivities

2265 Resistance to insulin action, i.e. decreased uptake of glucose from the blood at a given plasma insulin concentration, is a large public health problem in the U.S. Insulin action is quantifiable using 2 broad classes of methods. Open-loop techniques in which endogenous insulin production is replaced by exogenous infusion, e.g. the hyperinsulinemic clamp, allow quantitative assessment of peripheral glucose uptake (PGU) but do not closely approximate physiological conditions. Closed-loop techniques based on endogenous insulin secretion, e.g. the oral glucose tolerance test (OGTT), better simulate physiological conditions but do not allow calculation of PGU. The CIGMA technique (Continuous Infusion of Glucose with Model Assessment) is a closed-loop system developed and validated to quantitatively measure glucose uptake under “physiological” conditions. CIGMA is useful to characterize insulin resistance in a population but not to assess changes before and after an intervention. Purpose: To compare insulin action measured with by CIGMA, modified by scaling the infusion rate to fat free mass and including a glucose stable isotope to quantify glucose (m- CIGMA), to the Composite Insulin Sensitivity Index (C-ISI) derived from the glucose and insulin responses to a standard OGTT. Methods: On 2 separate mornings, in balanced order, insulin action was measured by m-CIGMA or C-ISI in 18 individuals (8 F, 9 M) who were expected to encompass a wide range of insulin actions. In the m-CIGMA test, [6,62H]glucose was infused for 90' in the fasted state followed by infusion of 20% dextrose (2% enriched with [6,62H]glucose) at 8.45 mg/kg FFM for 60'. During the steady-state period (last 10 minutes of the infusion) glucose (SSPG) and insulin (SSPI) concentrations were used to calculate insulin action (SSPG/SSPI). Insulin action was calculated from Glucose and insulin concentrations measured every 30' during the OGTT were incorporated into a mathematical model to derive C-ISI. Measures of whole-body insulin action generated by the 2 methods were compared with Pearson's correlation analysis. Results: There was a statistically significant relationship (r=.707, p =.003) between insulin action measured by M-CIGMA and C-ISI. Conclusion: These results suggest that for individuals with a range of insulin sensitivities, steady-state plasma glucose and insulin responses to the m-CIGMA infusion simulate the responses to a typical mixed meal. Insulin action measured by the m-CIGMA method is in good agreement with estimates based on the OGTT and can be used in conjunction with stable isotope dilution to assess peripheral and hepatic insulin action under physiological conditions

Tool force and deflection compensation for small milling tools

A technique to compensate for deflection of small milling tools (diameter<1 mm) has been demonstrated. This open-loop technique involves predicting the cutting and thrust forces, applying these forces to the tool, calculating the shape error due to tool deflection and creating a new tool path to eliminate this error. The tool force model has evolved from a decade of research to predict the forces in diamond turning. This model was modified to include the effects of tool rotation in milling as well as the changes in contact area and force direction using a ball end mill to create a free form surface. Experimental measurements were made to corroborate the components of the tool forces in the cutting and thrust directions. The force model was then combined with tool stiffness to calculate the deflection of the tool as a function of the depth of cut, the up-feed per revolution and the geometry of the part. Two experiments were used to demonstrate the effectiveness of this error compensation technique—a slot and a large circular groove. Each experiment reduced the error due to tool deflection by an order of magnitude from 20–50 μm to 2–5 μm.

Optimal pole shifting for power system stabilization

A method for shifting the real parts of the complex open-loop poles to any desired positions while preserving the imaginary parts is presented. In each step of this approach, it is required to solve a first-order or a second-order linear matrix Lyapunov equation for shifting one real pole or two complex poles, respectively. This presented method yields a solution, which is optimal with respect to a quadratic performance index. The attractive feature of this method is that it enables solutions to complex problem to be easily found without solving any non-linear algebraic Riccati equation. The gain feedback is calculated one time only and it works over wide range of operating conditions. The digital computation results verify the effectiveness of the proposed PSS for less overshoot and less settling time compared with the open-loop techniques. Moreover, the damping and synchronizing torques of the synchronous machine with and without the proposed robust PSS are calculated.

Fundamentals of Force Feedback and Application to a Surgery Simulator

Force feedback increases the effectiveness of virtual-reality surgery training systems. An overview of the fundamentals of applying force feedback is presented. An impedance control technique and data processing methods for stability preservation are illustrated. A flexible interface for general force-feedback applications has been developed. This interface is capable of controlling several different force-feedback hardware systems, including the SensAble PHANTOM, the Laparoscopic Impulse Engines from Immersion, and the VS-One virtual endoscopic surgery trainer. The findings are evaluated using the main simulation system, KISMET, and the modeling tools KISMO and VESUV. Within the scope of a cooperative project called HapticIO (funded by the German Ministry of Education and Research [BMBF]), new haptic devices have been designed for virtual neuroendoscopy and laparoscopy. The concept and implementations presented in this paper have been found to be flexible, stable and suitable for universal use. The impedance method, combined with the open-loop feed-forward control technique, is well suited and appropriate for the task.

Multicell converters: basic concepts and industry applications

Multicell power converters were introduced ten years ago. This paper summarizes the main results obtained through the research done on these converters over this period: topology and derivation of multicell choppers and voltage-source inverters; harmonics cancellation; open-loop modulation techniques; self-balancing understanding; and optimization. During this same period, industrial products using this technique have been developed and the corresponding know-how has contributed to the field in various ways, such as modular design, low inductance busbars, specific drivers, etc.

A new approach to closed-loop linear system identification via a vector autoregressive model.

A new vector autoregressive (VAR) model algorithm is developed for closed-loop identification. The new VAR approach is an extension of a recently developed algorithm, named the optimal parameter search (OPS), thus, we call the new technique VOPS, for vector OPS. Monte Carlo simulations of closed-loop systems were performed to compare the performance of VOPS to the widely utilized vector least squares (VLS) and vector fast orthogonal search (VFOS) approaches. In addition, we examined the effect on parameter estimates obtained via open-loop identification techniques, when using data from closed-loop systems. Comparative results show that both the VOPS and VFOS algorithms produce far more accurate parameter estimates than does the VLS. Furthermore, open-loop identification via univariate OPS and to a lesser extent univariate FOS for closed-loop systems, does not adversely affect the accuracy of the parameter estimates. An open-loop identification via the univariate least-squares method for closed-loop systems showed the most deleterious effect on the accuracy of the parameter estimates. In addition to developing the VOPS algorithm, we also developed approaches termed constrained OPS (COPS) and constrained FOS (CFOS). For closed-loop systems considered in this paper, both COPS and CFOS resulted in more accurate parameter estimates (less biased and more efficient) than did VLS, VFOS, and VOPS.

Fault detection and tolerance in synchronous vibration control of rotor—magnetic bearing systems

The use of magnetic bearings in rotating machinery provides contact-free rotor support, and allows vibration control using both closed-loop and open-loop strategies. One of the simplest and most effective methods to reduce synchronous lateral vibration when using magnetic bearings is through an open-loop adaptive control technique, in which the amplitude and phase of synchronous magnetic control forces are adjusted automatically to minimize the measured vibrations along the rotor. However, transducer malfunction, or faults in the signal-processing channels, may cause the controller to adapt incorrectly, with unwanted and possibly catastrophic effects. It is shown that an extension to the control strategy, which utilizes the variances of the measured system response and identified parameters, enables the faults to be detected and accounted for so that a modified control action can achieve continued and effective control of the synchronous vibration. The approach is extended further to identify changes in external factors, such as unbalance and rotor dynamics. Various faults and perturbations are examined experimentally, and the ability of the controller to detect and compensate for these changes is demonstrated.

Artificial endocrine pancreas.

Diabetes and its complications are a significant cause of morbidity and mortality in the world. Patients with diabetes have an excess risk of mortality compared with the nondiabetic population. Mortality rates are 41.8% for the diabetic population and 10.1% for the nondiabetic population. Among the diabetic population, the most common cause of death is cardiovascular disease, which accounts for 49.1% of deaths. The amount of life-years lost for patients with diabetes is strongly related to age at diagnosis and is a means of expressing mortality without relying on accurate prevalence data. The prevalence of physician-diagnosed diabetes has been steadily increasing in the US population, based on national household interview surveys conducted during the past 40 years. The prevalence of diagnosed diabetes from 1988 to 1994 was estimated to be 5.1% for US adults 20 years of age and older (10.2 million people when extrapolated to the 1997 US population). There were similar rates of diabetes for men and women. Based on American Diabetes Association criteria, the prevalence of diabetes (diagnosed plus undiagnosed) in people 40 to 74 years of age increased from 8.9% in the period 1976 to 1980 to 12.3% by 1988 to 1994. The prevalence of diabetes rose from 4.9% in 1990 to 6.5% in 1998. Increases were observed in both genders, all ages, all ethnic groups, all education levels, and nearly all states in the US. Many factors influence the prevalence of diabetes, including the development of new cases of diabetes and those that affect mortality from diabetes. High rates of abnormal fasting and postchallenge glucose, together with the increasing frequency of obesity and sedentary lifestyles in the population, make it likely that diabetes will continue to be a major health problem in the US. The prevalence of hypertension, hyperlipidemia, and the incidence of and mortality from heart disease and stroke are markedly declining in the US, but the prevalence of diabetes remains high. A similar increase also has been found world-wide. Diabetic complications such as neuropathy, retinopathy, nephropathy, and cardiovascular disease continue to pose major health risks for diabetic patients. Longterm complications associated with diabetes may result from a lack of blood glucose control. Consequently, much effort has focused on approaches that could replace conventional insulin therapy and provide more precise regulation of blood glucose levels. Indeed, the Diabetes Control and Complications Trial has conclusively demonstrated that improved metabolic control of glucose leads to the reduction in the rate of microvascular complications of diabetes. Conventional insulin treatment of diabetes mellitus does not prevent the vascular complications associated with longterm disease. To solve these problems, much investigation is conducted toward developing a means to provide near-physiologic insulin administration. Table 1 shows various treatments for diabetic patients. There are advantages and disadvantages to these treatments, which include pancreas transplants, islet or beta-cell transplants, hybrid devices in which the islet or beta cells are contained within permeable membranes, and a totally artificial endocrine pancreas (electromechanical artificial pancreas) that consists of a glucose sensor, a computer, and a pumping device. Biologic approaches are expected to fulfill all the endocrine functions of the normal pancreas, but at great expense; mechanical approaches fall short of total endocrine replacement but offer the substantial advantages of mass production. Each approach has inherent problems, and none is available for widespread clinical use now. So in general, many diabetic patients receive daily injections of insulin and face a high degree of compliance with a strict regimen of diet and exercise. Intensive insulin therapy is also usually associated with clinical problems including severe hypoglycemia and inherent instability of glucose control from the open-loop control technique. The difficulty of achieving longterm effective glucose control has encouraged us to develop a closed-loop control system, the artificial endocrine pancreas. PancreNo competing interests declared.

Detection of PD utilizing digital signal processing methods. Part 3: Open-loop noise reduction

The paper shows that open-loop noise reduction techniques can be effective in separating partial discharge (PD) signals from noise. Wavelet-based denoising through the use of thresholding of wavelet coefficients provides near optimal noise reduction for many classes of signals including PD signals in noise. The effectiveness of wavelet transform-based noise reduction depends on selection of an appropriate wavelet basis function as well as on careful selection of threshold function and levels.

Deconvolution of local surface response from topography in nanometer profilometry with a dual-scan method

In profilometric measurements, by scanning the sample twice with a fixed vertical offset, one can separate the signal that comes from surface heterogeneity from the topographic signal. Using differential confocal microscopy, a newly developed open-loop nanometer profilometric technique, we demonstrated this dual-scan method on composite samples and obtained 10-nm depth resolution. This technique can also be applied to other profilometric techniques such as atomic force microscopy and scanning tunneling microscopy.

Response of ASCE Task Committee Test Cases to Open-Loop Control Measures

Automated open- and closed-loop control systems can enhance the performance of irrigation delivery systems. This paper examines the response of the canal test cases developed by the ASCE task committee on canal automation algorithms to a particular anticipatory open-loop control technique, gate stroking. The performance of the ideal gate-stroking solution is compared with the performance of an approximate gate-stroking schedule that was generated by imposing practical constraints on the frequency and magnitude of the gate adjustments. Also analyzed were the performance of a nonanticipatory open-loop control scheme and the effect of model parameter uncertainties on the effectiveness of the control. For the test cases, the approximate gate-stroking schedules performed similarly to the ideal schedules. For two of the test cases, delivery performance was similar with and without anticipation, but was substantially different for the other two tests. The quality of the control degraded as a result of errors in model parameters, particularly in cases with incorrect check gate calibrations and submerged gate flows. Results point out the importance of combining open- and closed-loop control measures to improve the overall effectiveness of the control.

BLOOD/GAS SOLUBILITY AND ALVEOLAR RATE OF RISE OF POTENT INHALED ANESTHETICS DURING OPEN-LOOP FEEDBACK ADMINISTRATION USING A CLOSED-CIRCUIT ANESTHESIA LIQUID INJECTION TECHNIQUE

S342 INTRODUCTION: When using a high fresh gas flow (FGF) and a constant inspired concentration, the end-expired concentration [Et] of potent inhaled anesthetics rises faster with agents that have a lower blood/gas solubility (lambdaB/G): fast with desflurane (des), slower with sevoflurane (sevo), and slowest with isoflurane (iso) (lambdaB/G = 0.42, 0.60, and 1.38, respectively). [1] We determined whether this is still true when FGF is very low and an attempt is made to reach the [Et] as quickly as possible by using an overpressure technique. METHODS: With IRB approval and informed consent, 54 ASA I-III patients undergoing elective surgery under general endotracheal anesthesia with controlled mechanical ventilation were assigned to 1 of 3 groups, depending on the anesthetic studied: des (n=10), sevo (n=34), and iso (n=10). After IV induction and endotracheal intubation, liquid anesthetic was injected into the inspiratory limb of a closed circle system using a syringe pump. An [Et] of 1.3 MAC of des, sevo, or iso (8.5, 2.6, or 1.5%, respectively) was obtained as quickly as possible (overpressure). The initial bolus of liquid anesthetic was administered based on the known amount needed to prime the anesthesia circuit and functional residual capacity. Subsequently, the infusion rate of the syringe pump was adjusted to obtain and maintain the [Et] at 1.3 MAC. The [Et] was recorded every minute (Datex-Engstrom AS/3 multigas analyzer). The rate of rise of the three agents, expressed as a fraction of MAC, was compared. RESULTS: The [Et] over time for each agent is presented in Fig. 1. The rate of rise of [Et] did not differ between the three groups. DISCUSSION: When overpressure is used during an open-loop feedback closed-circuit anesthesia liquid injection technique, the rate of rise of [Et] of des, sevo, and iso is identical, and thus becomes independent of lambdaB/G. Commonly used pharmacokinetic principles of uptake of potent inhaled anesthetics do not apply when an overpressure open- or closed-loop (e.g., Physioflex, Drager) feedback closed-circuit anesthesia liquid injection technique is used.

Closed-Loop Identification of Flexible Structures: An Experimental Example

The application of a closed-loop identie cation procedure to a e exible structure, the Jet Propulsion Laboratory Control Structure Interaction Phase B testbed, is described. The approach is based on an indirect, closed-loop identie cation procedure, recently developed by Van den Hof and Schrama (Van den Hof, P. M., and Schrama, R. J., “ An Indirect Method for Transfer Function Estimation from Closed-Loop Data,” Automatica, Vol. 29, No. 6, 1993,pp.1523 ‐1527),whichgivesaconsistentmodelestimateinthecasewherethesystemnoise/outputdisturbance model is not accurate. The procedure is modie ed and applied, in the frequency domain, to closed-loop data from a e exible structure control experiment. The results of the analysis are compared to a purely open-loop frequencydomain identie cation approach. Enhancements to the experimental cone guration are also discussed. EEDBACK control for active vibration suppression is an area of signie cant importance to large spaceborne structures. The majorityofcontroldesigntechniquesappliedtothisproblemrequire a mathematical model of the system, compatible with the proposed design methodology. The identie cation of such models has been an area of active research interest within the e exible structure control design community. This paper examines a closed-loop approach to this problem, using frequency-domain data. Several identie cation approaches have received widespread attention, and for the most part, these are open-loop techniques. The

The multimedia multicasting problem

This paper explores the problems associated with the multicasting of continuous media to support multimedia group applications. The interaction between multicasting and the delivery of multiple time-correlated continuous-media streams with real-time delay requirements poses various new and interesting problems in research on communication protocols and architectures. We describe these problems, and identify where the opportunities are for effective solutions, all in the context of providing an overview of the current state of research in multimedia multicasting. The issues we discuss include quality of service, resource reservations, routing, error and traffic control, heterogeneity, and the use of hierarchical coding and open-loop control techniques.

Experimental Verification of Vibration Reduction in Flexible Spacecraft Using Input Shaping

The performance of many spacecraft can be improved by using closed-loop control and command-shaping techniques. However, because little information exists about the operation of controlled structures in zero gravity, it is dife cult for designers to anticipate and place cone dence in the on-orbit performance of their ground-based control designs. To address this issue, the middeck active control experiment was conducted aboard the Space Shuttle Endeavor in March of 1995. The results of the command shaping experiments implemented during the mission are presented, and guidelines forusing command shaping to suppress unwanted vibration in e exible space structures are proposed. HE combination of stringent performance specie cations and lightly damped structural modes makes the effective operation of many space systems vulnerable to vibration. To attack this problem, closed-loop control and open-loop command-shaping techniques are often enlisted. However, with only ground-based testing available prior to on-orbit implementation, uncertainty about zerogravity(0-g) behavior can hamper the success of these 0- g control designs. The Massachusetts Institute of Technology (MIT) middeck activecontrolexperiment (MACE)isaSpaceShuttlee ightexperiment designed to expose critical issues associated with the design of controllers and shaped commands for 0 g. As part of this experiment, data were collected from a e exible structure on-orbit, and results illustrated that both the control and command-shaping strategies employed on the test article could effectively reduce problematic vibration. Additionally, as a result of careful ground-based modeling efforts, predictions of 0- g behavior were accurate enough to achieve high-performance control and command shaping without on-orbit redesign. After introducing the MIT MACE project and the MACEcommand-shaping efforts, this paper presents the results from a specie c subset of the mission experiments: the MACE input shaping tests. Based on these results, key points are summarized and conclusions are drawn.

Pseudoheterodyne demodulation technique for fiber Bragg grating sensors using two matched gratings

A pseudoheterodyne, open-loop demodulation technique for detecting wavelength shifts in wavelength encoded fiber Bragg grating sensors is presented. The scheme uses a processing Bragg grating that is identical to one used as a sensor. When the processing fiber grating is stretched periodically, the system of two gratings produces a carrier at this frequency with its phase modulated by the measurand signal applied to the sensing grating. The demodulation technique is intrinsically immune to fluctuation of optical power in the system and is independent of the source spectral profile characteristics. A resolution of /spl ap/1 /spl mu//spl epsiv///spl radic/(Hz) for static axial strain was achieved.