Proportional Control Algorithm Research Articles

Design and evaluation of an efficient traffic control scheme for integrated voice, video, and data over asynchronous transfer mode networks: Explicit allowed rate algorithm

Asychronous transfer mode (ATM) networks are high-speed networks with guaranteed quality of service. The main cause of congestion in ATM networks is over utilization of physical bandwidth. Unlike constant bit-rate (CBR) traffic, the bandwidth reserved by variable bit-rate (VBR) traffic is not fully utilized at all instances. Hence, this unused bandwidth is allocated to available bit-rate (ABR) traffic. As the bandwidth used by VBR traffic changes, available bandwidth for ABR traffic varies; i.e., available bandwidth for ABR traffic is inversely proportional to the bandwidth used by the VBR traffic. Based on this fact, a rate-based congestion control algorithm, Explicit Allowed Rate Algorithm (EARA), is presented in this paper. EARA is compared with Proportional Rate Control Algorithm (PRCA) and Explicit Rate Indication Congestion Avoidance Algorithm (ERICA), in both LAN and WAN environments. Simulations of all three algorithms are conducted under both congestion and fairness configurations with simultaneous generation of CBR, rt-VBR, nrt-VBR and ABR traffic. The results show that, with very small over-head on the switch, EARA significantly decreases the required buffer space and improves the network throughput. Copyright © 1999 John Wiley & Sons, Ltd.

In situ compositional control of advanced HgCdTe-based IR detectors

The application of a feedback control system for maintaining a desired compositional profile during Hg 1− x Cd x Te epitaxy is reported. A spectroscopic ellipsometer monitored the optical properties of Hg 1− x Cd x Te films during deposition by molecular beam epitaxy. A library of optical constants was established from in situ measurements of multiple layers of varying composition. The compositions were subsequently determined ex situ using Fourier transform infrared spectroscopy. This work represents an extension of the compositional range of this control system to measure the x-values of Hg 1− x Cd x Te sensitive to long-, mid-, and short-wavelength infrared (LWIR, MWIR, and SWIR) radiation (0.16< x<0.6). The extension of the useful range of Hg 1− x Cd x Te compositions, which can be accurately determined in situ, has enabled epitaxy of a greater variety of detector structures and more complex device architectures. A proportional control algorithm, utilizing this library, adjusted the x-value in real time through changes in the temperature of the CdTe effusion cell. The application of this control system is demonstrated by measuring the compositional profile of a three layer Hg 1− x Cd x Te structure suitable for use as an MWIR/SWIR detector.

Active control of Rayleigh–Bénard convection

We report on stabilizing the unstable no-motion state in a moderate aspect ratio one-dimensional Rayleigh–Bénard convection experiment. A linear proportional control algorithm uses shadowgraphic convection images to determine heat flux perturbations which are applied to the lower boundary by a network of local heaters. We show that simple linear control stabilizes the otherwise unstable no-motion (conduction) state over a substantial range of supercritical Rayleigh numbers.

Active suppression of chatter in peripheral milling. Part II. Application of fuzzy control

In this paper, a feasibility study is conducted where fuzzy logic control is investigated to actively vary spindle speed modulation parameters for chatter suppression. A justification for using fuzzy control is given, as well as a brief synopsis of the fuzzy inferencing mechanism. Proportional and proportional-integral fuzzy control algorithms are developed. The set point in these controllers is established from experimental observations and measurements of the machined surfaces. Controller performance is tested by simulating changes in the axial depth of cut from a stable depth to 20% and 50% beyond the stable limit for constant speed cutting. It was found that both controllers were able to regulate the vibration in the milling process, however, the proportional-integral controller generally exhibited more desirable performance characteristics.

Radially Classified Aerosol Detector for Aircraft-Based Submicron Aerosol Measurements

A radially classified aerosol detector (RCAD) for fast characterization of fine particle size distributions aboard aircraft has been designed and implemented. The measurement system includes a radial differential mobility analyzer and a high-flow, high-efficiency condensation nuclei counter based on modifications to a commercial model (TST, model 3010). Variations in pressure encountered during changes in altitude in flight are compensated by feedback control of volumetric flow rates with a damped proportional control algorithm. Sampling resolution is optimized with the use of an automated dual-bag sampling system. This new system has been tested aboard the University of Washington Cl31a research aircraft to demonstrate its in-flight performance capabilities. The system was used to make measurements of aerosol, providing observations of the spatial variability within the cloud-topped boundary layer off the coast of Monterey, California.

Controlling chaos in a model of thermal pulse combustion

We describe methods for automating the control and tracking of states within or near a chaotic attractor. The methods are applied in a simulation using a recently developed model of thermal pulse combustion as the dynamical system. The controlled state is automatically tracked while a parameter is slowly changed well beyond the usual flame-out point where the chaotic attractor ceases to exist because of boundary crisis. A learning strategy based on simple neural networks is applied to map-based proportional feedback control algorithms both with and without a recursive term. Adaptive recursive proportional feedback is found to track farther beyond the crisis (flame-out) boundary than does the adaptive non-recursive map-based control. We also found that a continuous-time feedback proportional to the derivative of a system variable will stabilize and track an unstable fixed point near the chaotic attractor. The positive results suggest that a pulse combustor, and other nonlinear systems, may be suitably controlled to reduce undesirable cyclic variability and extend their useful operating range.

A combined admission and congestion control scheme for variable bit rate video

An approach is developed to maximize the bandwidth utilization of a network for continually transmitting sources, such as video sources. We assume that the sources use hierarchical encoding and can adapt their source coding rates in response to requests from the network congestion control algorithm, and we use this adaptability as the controlled input for a proportional control algorithm. We model flows entering or leaving the network as step inputs, and use the algorithm as the basis for admission control, using very little intelligence in the switches. We then present simulation results that demonstrate the algorithm working in a number of scenarios.

Active buckling control of smart composite plates-finite-element analysis

A finite-element model is developed for the active buckling control of laminated composite plates using piezoelectric materials. The finite-element model is based on the first-order shear deformation plate theory in conjunction with linear piezoelectric theory. The piezoelectric sensors and actuators can be surface bonded or embedded and can be either continuous or segmented. The dynamic buckling behavior of the laminated plate subjected to a linearly increasing uniaxial compressive load is investigated. The sensor output is used to determine the input to the actuator using a proportional control algorithm. The forces induced by the piezoelectric actuators under the applied voltage fields enhance the critical buckling load. Finite-element solutions are presented for composite plates with clamped and simply supported boundary conditions and the effectiveness of piezoelectric materials in enhancing the buckling loads is demonstrated.

Process Dynamics and Control of a Pilot Flotation Column

Abstract Froth flotation column is a counter-current bubble column that has recently been applied to separate hydrophobic mineral particles from mineral ore slurries. This paper describes the process control strategy, the process dynamics, and the control of a pilot scale froth flotation column. Control and monitoring of the flotation column was carried out using a personal computer equipped with an interface device. A direct digital feedback control loop was employed to control the interface level between the bubbly zone and the froth zone of the column. The incremental form of Proportional (P) and Proportionalintegral (PI) control algorithms were studied. Experimental results are presented for step changes in the interface level (set point), the feed flow rate, the wash water flow rate, and the gas flow rate. The start-up behaviour of the column is also described. Resume Une colo nne de flottation d'ecume est une colo nne a bulle fonctionnant a contre-courant. Recement, elle a ete utilisee pour separer ...

Glucose-stat, a glucose-controlled continuous culture

A predictive and feedback proportional control algorithm, developed for fed-batch fermentations and described in a companion paper (G. L. Kleman, J. J. Chalmers, G. W. Luli, and W. R. Strohl, Appl. Environ. Microbiol. 57:910-917, 1991), was used in this work to control a continuous culture on the basis of the soluble-glucose concentration (called the glucose-stat). This glucose-controlled continuous-culture system was found to reach and maintain steady state for 11 to 24 residence times when four different background glucose concentrations (0.27, 0.50, 0.7, and 1.5 g/liter) were used. The predictive-plus-feedback control system yielded very tight control of the continuous nutristat cultures; glucose concentrations were maintained at the set points with less than 0.003 standard error. Acetate production by Escherichia coli B in glucose-stats was found not to be correlated with the level of steady-state soluble-glucose concentration.

Adaptive PD controller for robot manipulators

Referring to the point-to-point control problem, a proportional and derivative (PD) control algorithm is presented that is adaptive with respect to the gravity parameters of robot manipulators. The proposed controller is shown to be globally convergent. Following the same approach, an application to the tracking problem is also presented. Simulation tests are included, with reference to a robot having three degrees of freedom. These tests show that the performances of the adaptive PD controller are scarcely influenced by the initial error. >

Design of a robot gripper with force feedback control

The design of a two-jaw robot gripper using a D.C. servomotor with optical encoder is described. Force control of the gripper is achieved using armature current sensing as a means of detecting motor torque and hence the force applied between the gripper jaws. The motor was modelled mathematically to obtain the second order equation relating armature current to the applied motor voltage. This relationship was used to develop a proportional plus integral digital control algorithm enabling force feedback to be achieved. Two-way communication between the ASEA robot controller and the IBM-XT gripper controller enables a range of gripping forces to be accessed throughout the robot programme cycle, any one of which may be selected at a particular time. Anticipated problems associated with the thermal drift and transient responses have largely been overcome by repeatedly recalibrating the gripper throughout a work shift.

Improving the Performance of Photo-Electrically Controlled Lighting Systems

The ability of a photo-electrically controlled lighting system to maintain a constant total light level on a task surface by responding to changing daylight levels is affected by the control algorithm used to relate the photosensor signal to the supplied electric light level and by the placement and geometry of the photosensor. We describe the major components of a typical control system, discuss the operation of three different control algorithms, and derive expressions for each algorithm that express the total illuminance at the task as a function of the control photosensor signal. Using a specially-designed scale model, we measured the relationship between the signal generated by various ceiling-mounted control photosensors and workplane illuminance for two room geometries under real sky conditions. The measured data were used to determine the performance of systems obeying the three control algorithms under varying daylight conditions. Control systems employing the commonly-used integral reset algorithm supplied less electric light than required, failing to satisfy the control objective regardless of the control photosensor used. Systems employing an alternative, closed-loop proportional control algorithm achieved the control objective under virtually all tested conditions when operated by a ceiling-mounted photosensor shielded from direct window light.

An Automatic Quality Controller for Resistance Spot Welding Processes

Quality control of the resistance spot welding is extremely important, since, even when the machine variables are held constant, there is considerable variation in the weld quality from part to part due to the large number of interrelated factors associated with the process. One such factor is the shunt effect which appears in practical welding situations. This paper presents an on-line feedback controller which can accomodate the shunt effect. The control system utilizes a proportional (P) control algorithm, incorporating with the electrode head movement as an output feedback variable. In this controller the welding current is generated so as to track a desired trace of the electrode movement which is representative of a good weld quality. A series of experiments was performed for various spot spacings to evaluate the performance of this tracking controller. The experimental results show that, as a result of this control the weld strength can be made to approach to a desired strength level.

A Microprocessor-Based Electrode Movement Controller for Spot Weld Quality Assurance

Quality assurance has been of a great concern in the process of resistance spot welding, since considerable variation in the weld quality often arises even when the machine variables are held constant. In this paper a new microprocessor-based control method is developed to obtain uniform weld quality regardless of the changing welding environments. The control system utilizes a proportional (P) control algorithm, incorporating with the electrode movement as a feedback variable. The controller generates the welding control current so as to track a desired trace of the electrode movement (reference electrode movement curve) throughout weld cycle. A series of experiments was performed to evaluate the performance of this control method. The results show that, as a result of the electrode movement tracking, weld strengths of all the weldments approach to a desired strength level.

Feedback control of a Darrieus wind turbine and optimization of the produced energy

This paper presents a microprocessor-driven control system, applied to the feedback control of a Darrieus wind turbine. The use of a dc machine as a generator to recover the energy and as a motor to start the engine, allows simplified power electronics. The architecture of the control unit is built to ensure four different functions: starting, optimization of the recoverable energy, regulation of the speed, and braking. An experimental study of the system in a wind tunnel allowed us to optimize the coefficients of the proportional and integral (pi) control algorithm. We found that the electrical energy recovery was much more efficient using our feedback system than without the control unit. This system allows a better characterization of the wind turbine and a regulation adapted to the wind statistics observed in one given geographical location.

Microprocessor-Based Data Acquisition and Control Software for Plant Growth Chambers (Spar System)

ABSTRACT COMPUTER software has been developed for a microprocessor-based data acquisition and control system to measure 64 transducers and to maintain closed loop environmental control for three sunlit Soil-Plant-Atmosphere Research (SPAR) units at Florence, SC. An assembly language program and a BASIC program were written to run concurrently by using a real-time inter-rupt. The assembly language program performs the data acquisition, real-time control, and time keeping. The BASIC program performs the dynamic signal condition-ing, the computation of control parameters, and the con-version and output of the acquired data in engineering units. Environmental control algorithms were im-plemented in software to control temperature, C02 con-centration, and relative humidity. The BASIC program utilizes the history of the absolute deviation from the control levels to compute the control parameters for the assembly language program to implement. The temperature control algorithm enabled control within 0.5 C for control temperatures ranging from 15 C to 35 C with ambient temperatures ranging from 4 C to 32 C. A proportional control algorithm written in BASIC enabled C02 control for three SPAR units within 10 mg/L under changing radiation load with full canopy closure using one infrared gas analyzer. A C02 control algorithm using light response curves is derived to pro-ject C02 uptake and absolute deviations from the control level to correct the coefficients of light response curves. Dynamic environmental control of the SPAR units, which involves process feedback influenced by random climatic variations, can be obtained using an inexpensive microprocessor-based system. This enables researchers to conduct precise experiments involving climatic variables to provide the necessary inputs for crop simula-tion modeling.