Open-loop Design Research Articles

Beam Switching Antenna Based on a Reconfigurable Cascaded Feeding Network

In this paper, a beam switching antenna (BSA) based on a reconfigurable cascaded feeding network (RCFN) is presented. The RCFN is engineered by cascading several varactor-loaded quasi-lumped couplers (QLCs). As the output port of the RCFN, the coupled port of every QLC is connected to an endfire radiator. BSAs based on two types of RCFN, the open-loop RCFN and closed-loop RCFN, are designed, simulated, and measured. The open-loop design features flexible beam switching strategies with the dynamic control of operation modes allocating the input power to the intended radiator(s), and single-/multibeam switching is achieved. In the case of the closed-loop RCFN, a power-recycling circuit is introduced to improve the efficiency of the single-beam switching mode of the BSA. Measured results show that the BSA operating in single-beam mode is able to radiate six switched beams each with a 3 dB beamwidth of 60°, covering 360° in the azimuth plane. The return losses and gain fluctuation of both prototypes are better than 15 dB and less than 1 dB, respectively. The corresponding experiments agree well with both the theoretical analysis and the simulation results.

Assessment of a novel pinhole supplementary implant for sulcus fixation in pseudophakic cadaver eyes

PurposeTo evaluate a novel small-aperture supplementary implant that applies the principle of pinholes for management of irregular astigmatism, in postmortem human eyes.MethodsPseudophakic human cadaver eyes were imaged by anterior segment optical coherence tomography (AS-OCT) to assess position of the in-the-bag intraocular lens (IOL). Eyes were prepared as per the Miyake-Apple technique. Two versions of the supplementary implant (open-loop and tripod designs) were then inserted into the sulcus of each eye. Evaluations under AS-OCT and from anterior and posterior views of the anterior segment were used to assess IOL fixation, centration, tilt, and interlenticular distance (ILD). This experimental study has been conducted in John A. Moran Eye Center, University of Utah.ResultsNine eyes were selected, with various sizes, primary IOL materials/designs, and Soemmering's ring formation. The open-loop model exhibited a mild degree of decentration and tilt in 2 eyes with zonular dehiscence. Mild decentration and tilt of the tripod were observed in 4 eyes; in 1 additional eye it was centered but mildly tilted. Three eyes with zonular dehiscence had one of the closed loops of the tripod located posteriorly to the ciliary processes. In all cases, an ILD was observed between the lenses (open loop: 0.65±0.13 mm; tripod: 0.41±0.12 mm).ConclusionsIt is important to take into account anatomical aspects related to ciliary sulcus fixation of supplementary IOLs. Both designs evaluated, exhibited appropriate centration and ILD. The open-loop design had less risk of tilt in association with haptics protruding posteriorly through areas of zonular weakness.

Open-Loop Precoder Design for Spatial Multiplexing Systems in Transmit Correlated MIMO Channels

The performance of spatial multiplexing (SM) systems is significantly degraded in transmit correlated multiple-input multiple-output (MIMO) channels. In communication systems that are available for feedback, precoding can enhance performance by exploiting channel state information (CSI) at the transmitter. However, broadcasting systems have no reverse channel nor any CSI. Furthermore, channel mismatches in communication systems severely affect performance. For these systems, open-loop precoders that require no feedback CSI were proposed. However, an analytical precoder design method was not presented in the previous works. In this paper, we present an open-loop precoder design method for SM systems with a maximum-likelihood receiver in transmit correlated MIMO channels. We first describe how to design an open-loop precoder using a rotational matrix over the amplitude of the correlation. Our precoder design method is derived by observing the effect of correlation mismatch between the feedback CSI and the actual channel condition on a minimum Euclidean distance-based precoder. Next, we present a method to design an open-loop precoder that takes into account the impact of the phase of the correlation. For this precoder, a phase rotation matrix is added on the rotational matrix, and optimum parameters are obtained by maximizing the worst-case minimum distance for the phase of the correlation. The simulation results illustrate the validity of proposed open-loop precoder in transmit correlated MIMO channels.

Open ring-shaped guider for circular continuous curvilinear capsulorhexis during cataract surgery

We describe a new type of open-loop caliper for capsulorhexis during cataract surgery. This tool, which is made of poly(methyl methacrylate), can optimize capsulorhexis shape, size, and centration. One of the strengths of this tool, which derives from the open-loop design, is its ease of insertion and removal via a small incision site compared with other calipers used for capsulorhexis. The caliper is positioned on the anterior capsule after the anterior chamber is filled with an ophthalmic viscosurgical device and removed after creation of the continuous curvilinear capsulorhexis. The caliper enables the surgeon to achieve an ideal capsulorhexis and promotes long-lasting circularity. Dr. Joo is one of the inventors on the patent filed by the Catholic University of Korea covering details in this manuscript. Dr. Lee has no financial or proprietary interest in any material or method mentioned.

Can analysis of performance and neuromuscular recoveries from repeated sprints shed more light on its fatigue-causing mechanisms?

Can analysis of performance and neuromuscular recoveries from repeated sprints shed more light on its fatigue-causing mechanisms?

Stabilization of the wheel and ball system

Abstract. In this article the design of the controller for wheel and ball system has been addressed. This system with the nonlinear properties in addition to unstable equilibrium point in open loop design is a good candidate for studying the control of the nonlinear systems in the laboratory. This system is able to be linearized with including the feedback for stabilization. The purpose of this study is to stabilize the ball at the equilibrium point. One of the novelties of the current research is including the effect of the constraint limits in design of the controller for this system which has not been mentioned in previous studies. Overcoming this short come it the aim of this paper.

Phase-conjugation-based fast RF phase stabilization for fiber delivery

In this paper, we propose a phase-conjugation-based fast radio frequency (RF) phase auto stabilization technique for long-distance fiber delivery. By phase conjugation at the center site, the proposed scheme pre-phase-promotes the RF signal with the shift which is acquired by round-trip transferring another RF whose frequency is half of the one to be sent. Such phase pre-promotion is then used to counteract exactly the following retard induced by one-way delivery. Different from the previous phase-locking-loop-based schemes, the proposed open-loop design avoids the use of any tunable parts and dynamic phase tracking, enabling a fast phase stabilization at the remote site. An end-less compensation capacity can also be achieved. Our design is analyzed by theory. Experimentally, the new scheme is verified by transferring a frequency of 2.42 GHz through a 30-km optical fiber link. Significant phase drift compression is observed. The rapid phase stabilization is verified by introducing sudden time delay change into the link. The recovery time equals to the round-trip time of the link plus the transitional duration of the delay change, which is much shorter than the traditional trial-and-error phase locking loop. Important issues of the system design are discussed.

Supercritical fluids as the desorbent for simulated moving bed—Application to the concentration of triterpenoids from Taiwanofugus camphorata

This study employs the SFE (supercritical fluid extraction) to extract the triterpenoids from the fruiting bodies of Antrodia cinnamomea (Syn. Antrodia camphorata and Taiwanofugus camphorata) cultivated in Petri-dish, followed by applying SF-SMB (supercritical fluid–simulated moving bed) to remove impurities from the crude extract of SFE to enrich the triterpenoids. Ethanol is used as cosolvent for the SFE extraction and SMB separation. A three-section SMB with open-loop design is employed and silica gel and C18 adsorbent are used as adsorbent. Four SMB experiments were designed and conducted to study the feasibility in removing impurities from the crude extract. When silica gel is used, two experiments of SF-SMB were conducted. The first SF-SMB experiment is conducted at constant concentration of ethanol and called as iso-SF-SMB, and the second experiment is designed to create gradient of elution power along the columns of the SMB unit and named as grad-SF-SMB. If RP-18 is used, iso-SF-SMB and classical SMB with liquid as desorbent are testified. The results show that grad-SF-SMB with silica gel has the highest effectiveness on removing the impurities and iso-SF-SMB with silica gel can also be applied to remove the impurities. The iso-SF-SMB with RP-18 can also be used for removing impurities with little loss of the triterpenoids, but classical SMB with RP-18 is not suitable for removing impurities from the crude extract. This study demonstrates that grad-SF-SMB could be a useful technology for developing botanical drugs and provides greener alternative for industries. This study also found that the operation of iso-SF-SMB and grad-SF-SMB can only qualitatively predictable by the triangle theory, and the removing of impurities can mainly achieved by serial trials.

Generalized feedforward tuning rules for non-realizable delay inversion

This paper describes the problem of load disturbance rejection using feedforward for the case when perfect compensation is not realizable due to processes delays inversion. First, a new generalized open-loop design tuning rule for feedforward compensators is proposed. Simple and intuitive guidelines are given for aggressive, moderate, and conservative performance results. Moreover, a switching feedforward compensator is proposed to be used when oscillations are not allowed in the process output. Simulation results show important improvements in disturbance rejection, reference tracking error and control effort.

Refractive outcomes in anterior chamber intraocular lenses

To the Editor,The 2008 United Kingdom Royal College of Oph-thalmologists’ (RCOphth) Cataract Surgery Guide-lines included, for the first time, a biometricbenchmark of achieving a final spherical equivalent(SE) within ±1 dioptre (D) of the target in 85 % ofcases [1]. This was based on a prospective analysis of4,806 eyes with in-the-bag lens implantation, with83.4 and 53.6 % within ±1 and ±0.5 D of predictedSE, respectively [2].We retrospectively applied this benchmark to anauditofrefractiveoutcomesforanteriorchamberlenses(ACIOL). Data were available in 52 eyes implantedwith 122UV lenses (Bausch & Lomb Inc., New York,NY,USA),a polymethylmethacrylate open-loop angle-supported design available in two lengths: 12.5 mm(S122UV) and 13.75 mm (L122UV). The manufac-turer’s A-constant of 115.8 was used in all cases.Subjective refractions were performed in 41 (79 %) of52 eyes, with the remainder by auto-refraction. Finalrefraction following suture removal revealed 71.2 %within ±1Dand40.4%within±0.5 D of target SE.Mean difference between target and achieved SE was0.37 D (range -1.77 to 2.54, SD 0.89); no differenceswere observed between refraction methods (p = 0.31,t test) or the two lens lengths (p = 0.44, t test), norwhether the lens was implanted as a primary orsecondary procedure (p = 0.41, t test). Weak correla-tion between increasing anterior chamber depth andgreater hypermetropic error was demonstrated (Pear-son’s correlation, r = 0.23). Raw data were submittedto the Users Group for Laser Interference Biometry(ULIB) website, providing an optimized A-constant of115.1 for use with the SRK/T formula (http://www.augenklinik.uni-wuerzburg.de/ulib/c1.htm).Comparative published outcomes predominantlyinvolve extracapsular extractions, although none pro-vide SE outcomes in the same RCOphth format:98 % ± 3D[3], 86 % ± 2D[4] and mean SE -0.73[5]. The largest series of 83 ACIOLs between 1991and 2005 (method of surgery not stated), reported amean refractive outcome of -0.8 D ± 1.67 [6].While RCOphth guidelines are not explicitly lim-ited to in-the-bag implantation, with the routine use ofoptical biometry, modern lens calculation formulaeand A-constant optimization there is no reason whyrefractive benchmarks should not be applied toanterior chamber implantation. While the inherentlimitations of this small retrospective audit areacknowledged, our data suggest that refractive out-comes with ACIOLs can be judged by the samebiometric standards.

Fractionation of polyethylene glycol particles by simulated moving bed with size-exclusion chromatography

In this study, a three-section simulated moving bed (SMB) with an open-loop design is used to fractionate polyethylene glycol (PEG) with different molecular weights. The purchased PEGs are mixed and separated by the open-loop SMB. A size-exclusion column with a pore size ranging from 10 to 100nm, TOSOH GMPW 7.5mm×30cm, is used to separate the mixtures. Based on the Triangle theory, the operating parameters of the SMB are determined and used to separate the three binary mixtures. The results show that the PEG mixtures with molecular weights of 400 and 8000, and those of 1500 and 20,000, are separable, yet those of 1500 and 3500 are difficult to separate by the selected column. The relative elution for molecular weights of 400 and 8000, and 1500 and 2000, is 1.49 and 1.54, respectively, resulting in easy separation. However, the difference in the elution volume for mixtures with molecular weights of 1500 and 3500 is so small that the operation condition is confined to a tiny area on the (m2, m3) plane defined by the Triangle theory. This makes robust application of the SMB impossible. Fortunately, it is still possible to obtain pure raffinate with low recovery, but a pure extract is still not possible. It is concluded that the low selectivity of the binary mixture and the fluctuation of the operation result in the difficulty in separating the 1500 and 3000 molecular weight mixtures. This paper presents the operation procedures, including the selection of the column, the discovery of selectivity, the application of the Triangle theory and the experimental results, in order to illustrate how to apply an SMB to the fractionation of PEGs.

Optimal Feed Point Design and Regulation of a Novel Plate Reactor

This work uses an open-loop analysis of a novel plate reactor to determine the optimum number of feed points and their locations to achieve maximum conversion. Once the open-loop design is optimized, a control system is designed to achieve maximum conversion of the reactants by regulating the reactor temperature using discrete proportional-integral-derivative (PID) controllers. It was found that the optimum number of feed points is two, equidistantly spaced from each other, and also that a PID controller design based on the internal model control method gives the best closed-loop performance.

Interdisciplinary Research-based Design: the Case of a kinetic form-active Tensile Membrane

In the last years it is increasingly acknowledged that advances in digital technology are paving the way to achieve integrated interdisciplinary design, a type of practice that covers a mindset of collaboration and cross-disciplinary communication and experimentation, visualization and research at all stages of the architectural design process. Along these lines interdisciplinary research is necessary to engage complex topics that bridge between design and engineering. An open loop design methodology of interdisciplinary physical and digital investigations from the conceptual development up to the detailed physical prototyping is proposed in the current paper. The approach is exemplified with the design of a kinetic form-active membrane system. Membrane surfaces comprise the basic component of the hybrid system developed, whereas any form modification is activated through the system’s cablenet and struts. The interactive platform of investigation, based on physical- and digital modelling serves for the definition of the system’s adaptability, its composition and the structural components design.

Separation of Resveratrol and Emodin by Supercritical Fluid-Simulated Moving Bed Chromatography

To separate resveratrol and emodin, supercritical carbon dioxide with ethanol was employed as the desorbent for a three-section simulated moving bed with an open-loop design called SF-SMB. Experimental validation of the separation was accomplished in this work. Silica was used as the stationary phase, and a crude extract of Polygonum cuspidatum containing mainly the resveratrol and the emodin, was purchased from a bio-technology company and used as the feedstock for the SF-SMB. Using single column chromatography, the operating conditions for a series of experiments conducted with 18 wt% ethanol were examined. The results were then compared to those predicted by the Triangle theory to determine the separable operating conditions and the dead volume of the SF-SMB unit. The robust operation of the SF-SMB against the concentration fluctuation of ethanol was also examined by conducting experiments with varied ethanol concentrations in different sections. It was found that the system is able to retain robust operation with about a 1.0 wt% ethanol fluctuation. Lowering the ethanol concentration to 15 wt% for each section was expected to relocate the separable operating conditions. A series of experiments with 12 wt% ethanol showed no pure raffinate. This is explained by the fact that the high flow rate of desorbent in the first section needed to obtain pure extract and raffinate would result in a high pressure drop, and lower the efficiency of the SF-SMB. From this study, the SF-SMB is demonstrated as being a useful technology for the separation of natural products, while providing a potentially greener alternative in the development of botanical drugs.

Low-K BCB Based 60 GHz Band Pass Filter on Al2O3 Substrate

A BCB based 60 GHz band pass filter implemented on Al2O3 substrate has been successfully designed, fabricated and tested. The CPW bended square open-loop resonator design has been adopted for its bending structure is beneficial to the size reduction. Al2O3 substrate is selected for reducing the process steps. The measurement results show a 45 GHz to 63 GHz bandwidth with an insertion loss of −1.8 dB across the band. Au and Cu filmed filter layer S-parameters are compared. The band rejection of −30 dB at 20 GHz and −20 dB at 100 GHz are observed.

The Design of Fast-Settling Three-Stage Amplifiers Using the Open-Loop Damping Factor as a Design Parameter

This paper presents an open-loop design method for fast-settling three-stage class-A amplifiers. Specifically, using the open-loop damping factor as a design parameter, the presented method delivers robust settling performance of a third-order system in the presence of process and component variation. As an illustration of the proposed approach, we show Spice simulation results of a nested-Miller-compensated three-stage-amplifier designed in 0.35-μm CMOS technology. The design achieves a 1% and 0.1% dynamic-error settling times of 6.4 ns and 13.7 ns, respectively, at a gain-bandwidth product of 55 MHz and a dynamic range of 80 dB, while consuming 5.4 mW from a 3-V supply.

Integrated open loop control and design of a food storage room

Usually, control design in a food storage room takes place after the plant has been designed. However, the performance of the plant connected to the controller might be improved by simultaneous design of the plant and the controller. In the case of open loop control, expressions that describe the dynamics of a controlled system (a bulk storage room) and its design criteria are deduced. These expressions contain all the physical system parameters, and give insight on how the system performance (in terms of energy usage and temperature uniformity) depends on the physical parameters. This insight gives realistic guidelines for integrated systems design and control, without the need for complex numerical computations. The physical relations that could not be found in the literature are identified experimentally. It is shown that a higher fan capacity reduces energy costs and improves the bulk temperature uniformity considerably, whereas the bulk shape is of very little influence. Furthermore, better wall insulation leads to a substantial energy cost decrease.

An engine control systems design for low‐emission vehicles by generalized predictive control based on identified model

AbstractConservation of the environment has become critical to the automotive industry. Recently, requirements for on‐board diagnostic and engine control systems have been strictly enforced. In the present paper, in order to meet the requirements for low‐emission vehicles, a novel method for construction of the air‐fuel ratio (A/F) control system is proposed. The method of construction of the system is divided into two steps. The first step is to design the A/F control system for the engine based on an open loop design. The second step is to design the A/F control system for the catalyst system. The design method is based on generalized predictive control in order to assure robustness to open loop control as well as model uncertainty. The effectiveness of the proposed A/F control system is verified through experiments using full‐scale products. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 169(3): 47–55, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20907

A tunable highly linear CMOS transconductor with 80 dB of SFDR

This paper presents a new tunable CMOS differential transconductor with an SFDR ranging from 80 to 94 dB. It is based on a core of two voltage buffers with local feedback loops to achieve low-output impedance. The two buffers drive an integrated polysilicon resistor, which is the actual transconductance element. The current generated at the resistor is delivered directly to the output using source coupled pairs. This avoids distortion generated by conventional architectures using current copying cells. The voltage buffers are based on the compact flipped voltage follower (FVF) cell. The proposed transconductor relies on the gain of local feedback loops instead of harmonic cancellation. This leads to a simpler design and less mismatch sensitivity. The proposed transconductor bandwidth is closer to that of the typical open-loop design than to one with global feedback, since the local feedback loop is much faster than a global one. It can be tuned down 20% of its maximum g m which is enough to compensate for process variations. The proposed circuit was fabricated in a 0.5 μm CMOS technology and powered by a 5 V single supply. It was measured with 2 Vpp input signals up to 10 MHz. The maximum g m value is 660 μA/V. The transconductor consumes 30 mW and occupies roughly a die area of 0.17 mm 2. Experimental results are presented to validate the proposed circuit.

Design method of gain-scheduled controllers not depending on derivatives of parameters

In general, designing Gain-Scheduled (GS) controllers for Linear Parameter-Varying (LPV) systems using Parameter-Dependent Lyapunov Functions (PDLFs) yields controllers that depend on the derivatives of parameters. This makes their implementation impractical because ideal parameter derivatives are not available in the real world. In contrast to this, for open-loop system design, such as filter design and inverse system design, we propose a GS controller design method using PDLFs that gives controllers which do not depend on parameter derivatives. Although the proposed method uses structured PDLFs, we show that it is as conservative as existing methods. Numerical examples of designing GS filters and GS right inverse systems for LPV systems are included to demonstrate our conclusion.