Reset Control Research Articles

Limited Authority Adaptive PI Control

It is demonstrated that PI control seems to be a perfect candidate for Limited Authority Adaptive Control as envisaged by Grimble: it seems rather often possible to dispense with adapting the PI controller reset time, while it is equally often very much needed to adapt the PI controller gain. This is due to the fact that PI control system stability (and performance as well) is very robust towards large changes of properly adjusted controller reset time, but rather unrobust with respect to even moderate changes of the controller gain. This idea is illustrated for indirect adaptive PI control of SISO plants and for indirect decentralized adaptive PI control of MIMO plants.

Optimal Design for Automatic Control of On-Demand Canal Systems

A methodology is developed for the design of an automatic gate controller for an on-demand canal system. The design is based on the EL-FLO plus RESET control concept developed previously by the U.S. Bureau of Reclamation. Two additional design parameters are included in this study to ensure a smooth upstream gate operation. The basic design parameters are optimized to achieve a stable flow condition in the entire canal system where multiple gates are operated to supply water to meet unexpected turnout demands along the canal. Due to the complexity involved in canal hydraulics, the optimization model is highly nonlinear. Decomposition allied with successive approximations is used for solution. The proposed design methodology, when applied to a section of the Caraibas Project in northeastern Brazil, showed that the proposed methodology is successful in minimizing hydraulic transients in a multipool canal system. A sensitivity analysis of the optimal design is conducted with respect to maximum demand level and the two new design parameters.

Optimized supply-air temperature (SAT) in variable-air-volume (VAV) systems

A criterion, based on optimization principles, for determining the SAT setpoint in VAV systems is presented. It is generally accepted that conventional SAT reset controls (SATRC), bounded by either space humidity or ductwork size, will save cooling and/or heating energy. How-ever, the ventilation consequences and penalty resulting from increased fan power have generally been overlooked. Ventilation is impacted since changes in the SAT setpoint change the primary airflow rate and the operation of economizer cycles, i.e. the distribution of fresh outdoor air (OA). These changes may result in extra energy demand and ventilation inefficiency if the reset criterion is not appropriate. This optimization concept simultaneously reduces energy consumption and meets ventilation requirements. Simulation results illustrate that the use of the optimized SATRC saves more energy than a conventional one.

First and higher order, heuristically based generalized perturbation theory (HGPT) with optional control reset variable

The heuristically based generalized perturbation theory (HGPT), to first and higher order, applied to the neutron field of a reactor system, is discussed in relation to the criticality reset procedure. This procedure is implicit within the GPT methodology, corresponding to the so called filtering of the importance function relevant to the neutron field from the fundamental mode contamination. It is common practice to use the so called λ-mode filter. In order to account for any possible reset option, a general definition is introduced of an intensive control variable (ρ) entering into the governing equations, and correspondingly a fundamental ρ-mode filtering of the importance function is defined, relevant to the real criticality reset (control) mechanism adopted. A simple example illustrates the need in many circumstances of interest of taking into proper account the correct filtering so to avoid significant inaccuracies in the sensitivity calculation results. The extension of this filtering technique to other functions entering into the GPT perturbative formulations at first and higher order is also discussed.

Tuning Proportional−Integral−Derivative Controllers for Integrator/Deadtime Processes

Chien and Fruehauf proposed the use of a simple integrator/deadtime transfer function to model many chemical processes, particularly those with large time constants. Tyreus and Luyben presented tuning rules that give the optimal reset time and controller gain for proportional−integral (PI) control of this type of process. This paper extends the previous work with PI control to proportional−integral−derivative (PID) controllers. Tighter control is possible with PID control, provided signals are not noisy. Frequency domain methods are used to show that the derivative tuning constant should be set equal to the reciprocal of the ultimate frequency. The controller gain is then set equal to 0.46 times the ultimate gain. This process has unusual dynamic behavior when PID control is used, which makes controller tuning nontrivial. The system exhibits conditional stability: at low controller gains the loop is unstable, and at high controller gains the loop is again unstable. Contrary to conventional tuning, a decr...

Development of the PID controller

In 1939, the Taylor Instrument Companies introduced a completely redesigned version of its Fulscope pneumatic controller. In addition to proportional and reset control actions, this new instrument provided an action which the Taylor Instrument Companies called pre-act. In the same year the Foxboro Instrument Company added Hyper-reset to the proportional and reset control actions provided by their Stabilog pneumatic controller. The pre-act and Hyper-reset actions each provide a control action proportional to the derivative of the error signal. Reset provides a control action proportional to the integral of the error signal and hence both controllers offered PID control. The historical development of these controllers is discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Polarization control for coherent fiber-optic systems using nematic liquid crystals

One of the obstacles to coherent fiber-optic communications is the unpredictable polarization drift which necessitates the use of an active polarization controlling system to match the polarizations of the signal and local oscillator. The polarization match must be maintained during the reset of any of the finite range components to prevent loss of data. A novel and practical system which uses three liquid-crystal devices for the polarization matching process is presented, and the required reset control algorithm and its derivation are described in detail.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Processor Controller for the IBM 3081

The IBM 3081 represents an important step in the evolution of large-scale data processing systems. The incorporation of LSI technology in its design has resulted in a departure from the use of traditional support tools and techniques. Its increased processing capabilities and its dyadic organization have further accented the requirements for high availability and ease of operation. This paper describes the Processor Controller unit of the 3081 Processor Complex, which handles the functions of maintenance, monitoring, and control of the system. It discusses how this unit has dealt with these changes to keep pace with the demands of advanced technology and improved system availability. In providing the necessary test and support functions of reset and manual control, the Processor Controller exploits the level-sensitive scan design capability of the 3081 to obtain read/write access to all latches and arrays. This design approach, coupled with significantly expanded capabilities for error recovery, configuration control, and diagnostics, has significantly affected the structure and capabilities of the Processor Controller.

Burst reset and frequency control of the neuronal oscillators in the cardiac ganglion of the crab, Portunus sanguinolentus.

1. The five large and four small neurones in the cardiac ganglion of the crab, Portunus, are electrotonically coupled and behave as a single relaxation oscillator, exhibiting periodic bursting activity in vitro. Recorded from the large neurone somata, this activity consists of 200-400 ms slow depolarizations called 'driver potentials' (Tazaki & Cooke, 1979a), accompanied by attenuated action potentials and EPSP's from small neurone input. 2. There is a strong positive correlation between the duration of the driver potential and the duration of the following interburst interval in the spontaneously active ganglion. This correlation is preserved during prolonged depolarization and hyperpolarization. 3. When a driver potential is prematurely terminated by an injected current pulse, the following interburst interval is shortened in direct proportion to the decrease in driver potential duration. 4. When a driver potential or a burst of high-frequency action potential activity is evoked by a depolarizing current pulse, the cardiac oscillator resets to the point of maximum hyperpolarization of the burst cycle, and the following interburst interval is of normal duration. Resetting following an evoked driver potential is complete. Partial resetting occurs only after short, evoked action potential bursts in the absence of a driver potential. 5. Reset of the oscillator causes phase shifts in the subsequent cycles of activity, which vary with the phase of application and duration of the injected current pulse. Response curves have been constructed for a comprehensive range of durations and intensities of hyperpolarizing and depolarizing current pulses applied at all phases of the oscillator cycle. 6. The phase shifts are composed of contributions from the duration of the current pulse, from the premature initiation of the slow depolarizing pacemaker potential due to early termination of the burst, and from the change in interburst interval correlated with truncation of the driver potential. 7. Considering the cardiac ganglion as a relaxation oscillator, frequencey control by entrainment to periodically applied current pulses was quantitatively predicted from the phase-response curves and experimentally confirmed. 8. A high concentration (10(-5) M) of octopamine can inhibit driver potential activity in the large neurones. This was used to examine possible frequency modulating effects of electrotonic feedback from the large neurone driver potentials onto the small neurone pacemaker activity. 9. The observations are discussed in relation to the ionic model for driver potentials and slow pacemaker potential activity in the cardiac ganglion, as proposed by Tazaki & Cooke (1979a, b).

An inexpensive manual reset control for stepper motors

Describes an inexpensive TTL circuit for easy manual setting of stepper-motor-controlled devices.

A Digital Integrator with a Memory

ABSTRACT An inexpensive (∼ $120), versatile, easily constructed digital integrator is described. Linearity is better than 1% for voltages of 0.1 to 15 V inputs. Input uncertainties are ≤ ∼ 200 μ V. Input impedance is ∼ 0.5 M. Integrals spanning at least a 1000:1 range can be read with 1% or better accuracy without varying the gain. Sensitivity is 5 count/V-sec, but higher or lower sensitivities are available by changing component values. A memory permits the integral at a particular instant to be locked into the display without any effect on the continuing integration. The reset, store, and track controls are transistor transistor logic compatible and may be operated by external circuitry for added versatility.

Multivariable PID estimation and control in systems with biased disturbances

A solution is given to yield reset control action in multivariable control systems, where the controller consists of a state reconstructor and feedback from estimated process and environmental states. Integral action in the estimation loop follows from the assumptions about the disturbance model, and if a special choice for the “feed-forward” matrix operating on the estimated environmental states is made, integral, or reset, control action results. The classical least squares optimal control with modeling of the environment is illustrated using a linearized model of a plug flow tubular reactor as a basis for the design. As a second example which illustrates the reset control action, i.e. the tracking of a constant reference vector with zero control error, a simple third order linear system is used.

The Solid State Pipeline Gauger

Abstract Automatic receiving and delivery facilities have been installed by Federated Pipe Lines Ltd. at all gathering points where power is available. Thisequipment reduces the frequency of visits by operating personnel and, barringcomponent failure, provides reliable control of pipeline facilities. The "Fieldgate" operational technique now being employed by producingcompanies requires that the pipeline provide the most efficient handlingpossible. In the past, crude from a field was received at perhaps a dozen ormore locations; now the entire production may be received at one "Fieldgate"battery. This resulting high throughput from a single location must not be heldup, and down time of pipeline facilities has to be kept to a minimum. Remote control of pipeline facilities at these locations of high throughputpermits continuous monitoring, and equipment malfunction is indicated at theoperating control center. Remedial action can be initiated much quicker by thismonitoring than by the visual inspection of a passing operator. The installation of remote control equipment must be considered carefully, bearing in mind that the automatic equipment at the battery is accomplishingthe over-all function of accepting, metering and shipping crude. The essential requirements of the remote control system are to provide anindication of equipment status and equipment on-off control. Digital readout ofthe metering equipment is required to determine periodic throughput. Alarmindications are to be registered whenever a condition arises which affects theoperation of the pipeline facilities. Reset control is a requirement to rectifypower failure conditions once power has been restored. Introduction The gathering system installed by Federated Pipe Lines Ltd. serves variouscrude oil producers in an area some 60 miles long and, at one point, 30 mileswide. Until ten years ago, this region of Alberta was an isolated wildernessand the only surface access was over a few forestry trails. The currentproducing fields of Swan Hills, Judy Creek, Carson Creek, Virginia Hills, Morse River, Inverness, Deer Mountain and House Mountain lie within this area.

Steam Generator Water-Level Control

A combined digital-analog mathematical model for the dynamic analysis of vertical U-tube natural-circulation steam generators is presented. The application of this model to the optimal design of a water-level controller for a steam generating unit is demonstrated. It is shown that a control system consisting of standard proportional and reset controls on water-level deviation from a desired set point and the difference between the steam and feedwater mass flow rates can be successfully employed for the control of water level in such a plant. The optimum values, as well as the range of the controller parameter sellings for which the steam generator exhibits a desired stable response, are determined.

Iterative analog computations

Reviewing the terms repetitive and iterative analog computers, the objects and means of iterative analog computations are explained and defined, together with a discussion of the basic operational computer requirements in terms of dynamic performance, repetitive reset control and the types and operations of the computational equipment. A few simple circuits are given which indicate and illustrate the characteristic operations of signal generation, detection, and recording and displaying as realized in iterative analog computations. In a number of specific examples taken from various problem areas in conventional analog computations, the fundamental circuits are utilized in the instrumentation of iterative simulations and computations, substantiating the introduction and application of iterations to achieve increased solution speed and accuracy, operational conveniance and equipment utilization, and to obtain better overall computer performance. In the concluding remarks the significance of iterative analog computations is discussed in view of the present state of the art, and a few important problem areas virgin to iterative techniques and methods are mentioned. The employment of novel computational units and systems has clearly indicated new possibilities and areas of utilization of analog computations. Future trends of research and development are believed to be based on the requirements of larget, more satisfactory memory systems and more elaborate logic and control features *** . *** This work has been made possible through grants from the Norsk Hydro-Elektrisk Kv˦lstofaktieselskab, Oslo.

Analysis of a differential magnetic amplifier with flux reset control

This paper describes in detail the theoretical operation and mathematical analysis of a differential magnetic amplifier circuit operating on the flux reset control principle.Experimental results verify the theoretical operation and the usefulness of the derived gain and output range equations. With the results of this investigation, it is possible to make intelligent use of a simple, yet extremely versatile magnetic amplifier circuit.