Sophisticated Control Strategies Research Articles

A Simply Stabilized Running Model

The spring-loaded inverted pendulum (SLIP), or monopedal hopper, is an archetypal model for running in numerous animal species. Although locomotion is generally considered a complex task requiring sophisticated control strategies to account for coordination and stability, we show that stable gaits can be found in the SLIP with both linear and "air" springs, controlled by a simple fixed-leg reset policy. We first derive touchdown-to-touchdown Poincaré maps under the common assumption of negligible gravitational effects during the stance phase. We subsequently include and assess these effects and briefly consider coupling to pitching motions. We investigate the domains of attraction of symmetric periodic gaits and bifurcations from the branches of stable gaits in terms of nondimensional parameters.

Improving the comfort of a fast ferry

A study was conducted to determine the effectiveness of using controlled flaps and a T-foil to smoothen a ship's vertical motion while navigating in head seas. The study comprised two steps: to develop a tool for control design in the form of a computer-based simulation and to use this tool to develop satisfactory controllers. The simulation was based on mathematical models of the ship, the actuators, the waves and the seasickness effect. Since the actuators have limited action, there is a limited margin for improvement based on more sophisticated control strategies. Possible improvements of motion sickness incidence (MSI) are linked to a control strategy that exploits better synchronization with incident waves.

Integrated energetic approach for a controlable electrochromic device

The potential of controlling techniques for an electrochromic device is investigated in a systematic way, using both experimental and theoretical tools. Concerning the theoretical part a model was developed in the TRNSYS environment and validated against experimental data. These data were collected from experiments, which were carried out in a PASSYS test cell with a movable wall. Having established a good model performance several cases of window types (such as a 4 mm clear window and a low-e double glazing) and controlling strategies for the electrochromic device are simulated. Obtained results from the series of simulations were compared in terms of the heating and cooling loads of the test cell for each case. It was found that the development of a scheduled control strategy for the electrochromic glazing is better in terms of cooling loads. Finally, a more sophisticated control strategy was examined based on the adaptive fuzzy approach.

Simultaneous Control of Apparent Extract and Volatile Compounds Concentrations in Beer Fermentation

The objective of this study is to develop a system for controlling apparent extract concentration which should be decreased below the target value at a fixed time under the constraint for admissible amounts of production of volatile compounds. To this end, a sophisticated control strategy comprising a state estimation step for fermentation degree, and calculation and decision steps for brewing temperature profile for the simultaneous control of apparent extract and volatile compounds concentrations was developed here. For the estimation of apparent extract and volatile compounds concentrations, CO 2 concentration in the exhaust gas was utilized. Temperature profiles, which will bring the brewing process to the target apparent extract concentration so as to produce fewer amounts of volatile compounds than the threshold concentrations at a fixed time, were searched and decided by feeding back the information of fermentative activity of the inoculated yeast cells. The developed feedback control of the brewing temperature profile was successfully applied to the brewing process, and apparent extract and volatile compounds concentrations at a fixed time satisfied the target conditions. The control technique developed here allows us to brew a wide variety of beers with different tastes.

Two Subtypes of Ecdysis-triggering Hormone Receptor inDrosophila melanogaster

Insect ecdysis is a hormonally programmed physiological sequence that enables insects to escape their old cuticle at the end of each developmental stage. The immediate events leading to ecdysis, which are initiated upon release of ecdysis-triggering hormones (ETH) into the bloodstream, include respiratory inflation and sequential stereotypic behaviors that facilitate shedding of the cuticle. Here we report that the Drosophila gene CG5911 encodes two functionally distinct subtypes of G protein-coupled receptors through alternative splicing (CG5911a and CG5911b) that respond preferentially to ecdysis-triggering hormones of flies and moths. These subtypes show differences in ligand sensitivity and specificity, suggesting that they may play separate roles in ETH signaling. At significantly higher concentrations (>100-fold), certain insect and vertebrate peptides also activate these receptors, providing evidence that CG5911 is evolutionarily related to the thyrotropin-releasing hormone and neuromedin U receptors. The ETH signaling system in insects is a vital system that provides opportunities for the construction of models for the molecular basis of stereotypic animal behavior as well as a target for the design of more sophisticated insect-selective pest control strategies.

Near Zero NOx Emissions and High Fuel Efficiency Diesel Engine: the Naditm Concept Using Dual Mode Combustion

The part of Diesel engines on the transport market should increase within the years to come thanks to their high thermal efficiency coupled with low carbon dioxide (CO2) emissions, provided their nitrogen oxides (NOx) and particulate emissions are reduced. At present, adequate after-treatments, NOx and particulates matter (PM) traps are developed or industrialized with still concerns about fuel economy, robustness, sensitivity to fuel sulfur and cost because of their complex and sophisticated control strategy. New combustion process such as homogeneous charge compression ignition are investigated for their potential to achieve near zero particulate and NOx emissions. Their main drawbacks are too high unburned hydrocarbons (HC) and carbon monoxide (CO) emissions, combustion control at high load and then limited operating range and power output. As an answer for challenges the Diesel engine is facing, IFP has developed a combustion system able to reach near zero particulate and NOx emissions while maintaining performance standards of the DI Diesel engines. This dual mode engine application called NADITM (Narrow Angle Direct Injection) applies homogeneous charge compression ignition at part load and switches to conventional Diesel combustion to reach full load requirements. At part load (including Motor Vehicle Emissions Group-MVEG-and Federal Test Procedure-FTP-cycles), HCCI combustion mode allows near zero particulate and NOx emissions and maintains very good fuel efficiency close to an Euro III Diesel engine. At 1500 and 2500 rpm, NADITM reaches 0. 6 and 0. 9 MPa (6 and 9 bar) of indicated mean effective pressure (IMEP) with emissions of NOx and particulate under 0. 05 g/kWh. That means respectively 100 and 10 times lower than a conventional Diesel engine. At full load, NADITM system is consistent with future Diesel engine power density standard. At 4000 rpm, 50 to 55 kW/l has been reached with conventional limiting factors and engine parameters settings. Advanced engine technology such as further generation of common rail fuel injection system, Variable Valve Actuation (VVA), Variable Compression Ratio (VCR) engine or electric assisted turbocharger will be useful for the well identified next development steps of the concept.

A Simply Stabilized Running Model

The spring-loaded inverted pendulum (SLIP), or monopedal hopper, is an archetypal model for running in numerous animal species. Although locomotion is generally considered a complex task requiring sophisticated control strategies to account for coordination and stability, we show that stable gaits can be found in the SLIP with both linear and ``air'' springs, controlled by a simple fixed-leg reset policy. We first derive touchdown-to-touchdown Poincare maps under the common assumption of negligible gravitational effects during the stance phase. We subsequently include and assess these effects and briefly consider coupling to pitching motions. We investigate the domains of attraction of symmetric periodic gaits and bifurcations from the branches of stable gaits in terms of nondimensional parameters.

A Flight Simulator for Surgeons - Novel Technologies for Haptic Devices in a Complex Virtual Reality Environment

This paper presents the development of an entire medical simulator for the training of minimally invasive surgery. This demands a global view on mechatronics engineering and includes the design of new mechanical structures, novel sensors and sophisticated control strategies to simulate realistic haptic feedback. Moreover, new deformation techniques for virtual organs have been implemented to allow real time operations in a complex virtual reality environment.

Model-based fault detection and diagnosis for diesel engines

Due to the increasing complexity of diesel engines with more and more electrical and electronic components and sophisticated control strategies, automatic fault detection and diagnosis is becoming increasingly important. Within the scope of the FVV project “Model-Based Fault Detection and Diagnosis for Diesel Engines” at the Institute of Automatic Control, Darmstadt University of Technology, new model-based methods for monitoring the intake system, the injection, the combustion and the exhaust system have been developed.

INTERVENING IN THE PUBLIC SPHERE: GERMAN GOVERNMENTS AND THE PRESS, 1815–1870

This article argues that the growth of a free press in nineteenth-century Germany went hand in hand with the growth of an official, government-sponsored, press. The collapse of pre-publication censorship in 1848 prompted the development of increasingly sophisticated (and relatively successful) press control strategies by German governments, in the shape of official newspapers, semi-official newspapers, and indirect government press influence. Government press policy was essentially reactive. Changes in press policy were usually prompted by political events. Furthermore, government press coverage was forced to reflect shifts in public opinion in order to maximize readership of official propaganda. Government press policy focused not just on the dissemination of pro-government opinion, but also on the dissemination of pro-government information, probably the most effective form of government press influence. News management was subtle, and targeted small circulation local newspapers, rather than high profile opposition newspapers. Consequently, historians have tended to overlook the scale of government news management.

Pseudorotor-flux-oriented control of an induction machine for deep-bar-effect compensation

In an induction machine with deep rotor bars, the rotor parameters change due to skin effect and saturation, and the skin effect is often modeled as a ladder network. For the high-performance drive of an induction machine with deep bars, many sophisticated control strategies and machine models have been discussed. As a control strategy, a complicated airgap flux-oriented control scheme is mostly adopted, because it is not possible to define a unique rotor flux in the deep bar model. However, a unique pseudorotor flux can be defined, and it is straightforward to achieve independent control of pseudorotor flux and torque. This control scheme can be applied to any nth multiple ladder network. In this paper, it is shown how a deep-bar effect of an induction machine can be negligible by performing the proper field-oriented control. By using the concept of pseudorotor flux, the conventional rotor-flux-oriented control using equivalent rotor parameters is effective for deep-bar and/or double-cage machines. The actual insulated gate bipolar transistor (IGBT) inverter systems with a high-precision torque transducer are implemented and thoroughly tested on a 250 hp induction machine and a 5.5 kW double-cage induction machine to confirm their validity.

Autonomously Learning Fault Detection System for Gas Turbine Engines

Abstract Highly sophisticated control strategies are generally employed to control aircraft gas turbine engines which have to operate in harsh environmental conditions. Faults are difficult to detect with this increased complexity and the present fault detection systems sometimes indicate the wrong components to be faulty. These faults cost the airline industry millions of pounds each year. To improve the performance of these existing systems an autonomously learning fault detection system is proposed. The system is capable of detecting new faults and also adapting to faults that are similar to faults previously encountered. This paper presents the performance of this system when applied to real engine data and gives details on the improvements made to the system.

Evaluation of lead/acid batteries under simulated electric-vehicle duty: development of design parameters on the basis of SFUDS performance

As manufacturers move to meet the expanding demand in batteries for electric-vehicle (EV) applications, there is a need to develop and apply test schemes that provide a true measure of battery performance. The Simplified Federal Urban Driving Schedule (SFUDS) is one of several such duty profiles that have been derived from extensive studies of urban vehicle duty. Accurate implementation of the SFUDS is, however, difficult because the load is specified in terms of power and is varied every few seconds. This necessitates a sophisticated control strategy, combined with high-speed monitoring. In our laboratories, these requirements have been met by a digital measuring and control system in which all functions are handled by a microprocessor. SFUDS testing reveals battery performance to be critically dependent on the specific power capability. In particular, maximum vehicle driving range depends primarily on the proportion of current-generating materials that are present. For optimum performance, lead/acid batteries for EV service should be designed for minimum unit weight and maximum power output. In this way, the average rate of discharge is minimized and the battery voltage remains longer above the cutoff value. From these observations, it is suggested that the next generation of EV batteries will probably resemble present-day automotive (thin plate) batteries rather than the heavier (thick plate) units that are currently used in motive-power applications. They will also need to incorporate improved negative plates which are better able to withstand repetitive high-rate cycling. The latter is the defining feature of EV duty because it places severe demands on both the positive and negative plates.

Progress in the control of chaos

Abstract In this review, we summarize several of the key contributions made over the past 5 years to the control of chaotic dynamical systems. The idea that chaotic systems can in fact be controlled may be counter-intuitive; after all they are unpredictable in the long term. Nevertheless, numerous theorists have independently developed methods which can be applied to chaotic systems, and many experimentalists have demonstrated that physical chaotic systems respond well to both simple and sophisticated control strategies. The great bulk of these researchers have restricted their study to low-dimensional systems, and correspondingly we critique this work at length. Most recently, a few researchers have proposed control techniques for application to high- or infinite-dimensional systems, and we describe this work in some detail as well.

On-line measurement in biotechnology: Exploitation, objectives and benefits

Sound data biologically relevant are prerequisites when developing high-performance bioprocesses. Understanding of physiological regulation as well as sophisticated control strategies are highly dependent on the observability of the culture, i.e. the generation and exploitation of suited signals even under complex environmental measurement conditions. Against this background, the increasing number of analytical systems is very supportive and, accordingly, an appropriate handling of sensors and measured data is of decisive importance. This article reports on practical experience with routines for maintenance, service and calibration of hardware sensors which improve the quality of measurements significantly. Verification and validation of signals is outlined in order to make the value of data exploitation tools obvious. A method for the characterization of information is introduced by practical examples of Saccharomyces cerevisiae cultures when explaining the specific properties of extracting biological information from raw data. Finally, examples for advantageous exploitation of on-line data are given.

Active Stabilization of Centrifugal Compressor Surge

Active suppression of centrifugal compressor surge has been demonstrated on a centrifugal compressor equipped with a servo-actuated plenum exit throttle controller. The control scheme is fundamentally different from conventional surge control techniques in that it addresses directly the dynamic behavior of the compression system to displace the surge line to lower mass flows. The method used is to feed back perturbations in plenum pressure rise, in real time, to a fast-acting control valve. The increased aerodynamic damping of incipient oscillations due to the resulting valve motion allows stable operation past the normal surge line. For the compressor used, a 25 percent reduction in the surge point mass flow was achieved over a range of speeds and pressure ratios. Time-resolved measurements during controlled operation revealed that the throttle required relatively little power to suppress the surge oscillations, because the disturbances are attacked in their initial stages. Although designed for operation with small disturbances, the controller was also able to eliminate existing, large-amplitude, surge oscillations. Comparison of experimental results with theoretical predictions showed that a lumped parameter model appeared adequate to represent the behavior of the compression system with the throttle controller and, perhaps more importantly, to be used in the design of more sophisticated control strategies.

Air movement in a partitioned industrial environment

A study of the effects of air movement within a complex factory building is described. Air conditioning systems operated to alleviate discomfort in some parts of the factory, and to satisfy product requirements in another. The interaction of the various air conditioning systems and potential overcapacity were considered to offer scope for improvement. Environmental investigations included the use of a tracer gas to examine air transfers. It was concluded that air transfers between adjacent partitioned areas were low, enabling the adoption of a more sophisticated control strategy which would reduce the demand for conditioned air.

Microcomputer Control of Power Converters

Thyristor power converters are charac terized by an inherent discrete control action and are, therefore, particularly well suited to on-line control by microcomputers. The paper presents a new design of digital controllers based upon powerfull 16-bit or bit-slice microprocessors, which provide high firing time resolution and enough computing power to implement sophis ticated control strategies. Both hardware and software are discussed, with special emphasis on the firing con trol algorithms. The properties of Pulse Frequency Con trol (PFC) and Pulse Phase Control (PPC) are examined and small-signal discrete models are presented. These models are used in the analysis of constant current and constant extinction angle control through the z-transform method.

A design approach to a computer‐controlled injection‐molding machine

AbstractPlastics injection molding is a complex, multi‐variable process which has not yet been clarified. The hardware controller is difficult to build without a realistic mathematical model. One powerful technique for solving such a difficulty is to employ digital control technology which can utilize sophisticated control strategies in order to optimize the system performance. Machine operation and resultant production can be tightly controlled by using computer monitoring, data storage and data logging. This paper presents elements of the various problems that process engineers may encounter in designing a computer‐controlled system for plastics injection‐molding machinery. The variables of the process and a functional analysis of process control are discussed. A hardware system design; including specification of computer, selection of peripheral devices, system design, and input/output interfacing; is presented.

Influence of the Process Computer on the Basic Instrumentation and on the Communication Between Operator and Process

It has long been recognized that the computer can make a valuable contribution to process control. Until now most computer implementations in this field have led to DDC or supervisory control. Promises of addition of substantial functions have seldom been fulfilled.The justification of the application of a computer is mostly based on the assumption that with the aid of a computer a more sophisticated control strategy would be possible or that a considerable decrease in the costs of the conventional instrumentation can be achieved.The expected benefits of the more sophisticated computer control are not often realized. Many large computer systems degraded to mere data logging devices, because it was not possible to implement the optimizing and other functions in due time.The “ break-even point” for the amount of control loops, to be replaced by the computer, for lower investment appears to be a fatamorgana.We believe, however, that there are other aspects of computer control, which should have more attention. We state that there has been no influence of the computer on conventional instrument deSign, that there has been no influence on the conventional control panel design, and that the possibilities of the communication between operater and plant are hardly recognized.In this paper these aspects will be illustrated in view of our experiences in several projects.We analyzed the functions of the instrumentation for a new plant carefully andwe split these functions up into different categories.This splitting up of tasks has led to a computer application with strongly reduced conventional instrumentation. Besides this reduction, the instruments applied could also be of a different and Simpler nature, which has led to considerable cost reductions.A closer examination of this and other computer installations in our works leads to the conclusion that there exists not yet a systematical approach in the man-machine relation and that the communication of the process and the operators with the computer system is often solved in an expedient way and is subject to personal taste.In connection with the instrumentation of the above-mentioned plant an analysis was made of the possibilities for the implementation of the process computer as an integral part of an instrumentation scheme.Problems discussed are the lay-out of control rooms, development of the input and output devices (displays) and influence on the basic instrumentation.