Open-loop Mode Research Articles

Application of Self-tuning Predictive Control in Lead and Zinc Smelting Blast-furnace

Due to the complication of the technology, the process control of lead and zinc smelting blast-furnace until now is still a kind of manual control depending on the operator's experience. This paper presents a self-tuning predictive control method, suitable for complicated process, and its application in smelting process control of the blast-furnace. The control system has two operating modes: partial closed-loop mode and open-loop mode (man-machine system). Owing to the combination of the computer's self-tuning prediction with the operator's experience and intuitive judgement, little risk will be invovled in this control system, making it appropriate for controlling complicated and slow processes

A class of adaptive model- and object-driven nonuniform sampling methods for 3-D inspection

Inspection of manufactured parts and assemblies often requires large amounts of information in the form of test probe point locations and large amounts of time to perform the inspection. By optimally locating the probe points it is possible to maintain inspection reliability using fewer test probes in a reduced amount of time. We have developed algorithms which use part model and manufacturing process information to generate an optimal probe-point location set for routine inspection in a modelbased, open-loop mode. An alternate set of adaptive algorithms that sequentially generates probe-point locations in an object-based, closed-loop mode characterizes a fault when one is detected. Test results show that the algorithms perform favorably on a large class of surfaces.

BWR natural circulation experiments at ROSA-III under low-power and reduced inventory conditions.

The natural circulation core cooling is important during small break loss-of-coolant accidents and transients involving loss of forced-circulation core cooling. This paper presents results of natural circulation experiments conducted in the ROSA-III (Rig of Safety Assessment No. 3) facility under reduced mass inventory conditions. Three distinct modes of BWR natural circulation were identified in the experiments: the primary circulation mode, the internal circulation mode and the open-loop (core uncovery) mode. One-dimensional quasi-steady analytical model was developed for the internal natural circulation mode to determine the core uncovery criterion. The model predicted well the two-phase mixture level inside the core shroud for quasi-steady state natural circulation at pressures of 7.35 and 2.06 MPa, and scaled core powers below 20%, and was used to predict BWR natural circulation behaviors.

A New Criterion and a New Algorithm for Fixed Modes in Decentralized Control

Based on Matrix Fraction Description (MFD) and decomposition of the feedback structure into fundamental substructures, a new criterion for testing fixed modes as well as their orders w.r.t. arbitrary constrained feedback structure is presented, which leads straightly to a new algorithm for evaluating fixed polynomials and fixed modes without solving high order characteristic equation. Some new concepts are introduced to illustrate the successive procedure of the open-loop modes changing from fixed to variable, which provide detailed structural information about the occurence of fixed modes.

Acoustic Range Sensing Servo Control: Improved Robot Positioning and Trajectory

Absrracr-A technique is described for improving the accuracy of the path followed by a robot arm in precision tracking of an object’s surface contour. Acoustic pulse-echo range data from a sensor mounted on a robot end effector was used to enable real time path modification, correcting for errors in the robot’s internal sensors, calibration, and servo-control. An eddy current proximity sensor positioned approximately 30 mil from the surface monitored the acoustic sensor and robot performance. In open-loop mode, both sensors produced identical results in tracking variations in distance from the surface. Variation from a linear path was as large as 10 mil. The acoustic range sensor enabled a servo control algorithm to reduce path deviation lo +3 mil using single measurements in real time. This variation is attributable to the inherent noise level of the sensor system and ambient fluctuations in sound velocity. Averaging ten measurements reduced the standard deviation in position measurement and control to +_l2 mil. The acoustic ranging system has also proved capable of correcting position error induced by a dynamic change in mass loading at the end effector.

A simple open-loop vibrating system for variable amplitude and frequency sinusoidal stretching of muscles

A device designed to provide controlled variable amplitude and frequency sinusoidal stretching of muscles is described. The constructed vibrator included a pivoted lever with one arm fixed and the other variable, and was driven by an electric motor. The use of a powerful motor ensured that the stimulation parameters would not be significantly affected with tension changes in the muscle during contraction, which enables operating the system in an open-loop mode. This device is simple, low cost, and may be used in a variety of neurophysiologic studies with only conventional grounding, shielding, and noise suppression.

Effects of muscle model parameter dispersion and multi-loop segmental interaction on the neuromuscular system performance.

The effects of parameter dispersion among motor units on the neuromuscular system performance as well as interaction between muscle segments and spinal cord mechanisms are investigated. Elementary components of the system are modeled to simulate with simple models their input-output characteristics. A leaky SS-IPFM encoder with a time-dependent threshold simulates the motor-neuron encoding characteristics. An amplitude and time dependent nonlinear model represent the motor unit mechanical output to neuronal input relationship. The dispersion of parameters in the components of the whole muscle control model is investigated in the open loop mode. It is shown that the dispersion of parameters in the multi-efferent channels converging on a common tendon provides a spatial filtration generating a smoother muscle force in addition to extending the linear dynamic range compared to a similar system having identical motor units. Muscle segmental interaction is investigated in this distributed model by closing the loop through a coupling matrix, representing afferent-motorneuron interaction on the spinal cord level. A diagonal matrix represents no segmental interaction and a uniform matrix represents a uniform interaction between segments through the muscle spindles and Golgi tendon feedback elements. The close loop simulation studied shows that (a). The type of segmental interaction has little effect on the overall system performance, i.e., range of linerity and stability, which is the result of having a muscle system with a large number of motor units. (b) There are only minor differences in results between the uniform and normal parameter distributions tested. (c) A loop gain of 4 divided by 8 in the distributed model can provide linearity through the full physiological force range. (d) Type of segmental interaction has significant effects on the individual segment. A uniform matrix provides a more stable segment due to the spatial filtration resulting from the segmental interaction, while the diagonal noninteracting matrix shows instabilities on the local segmental level despite global stability. The more realistic exponentially decaying spatial interaction matrix yields both global neuromuscular and local segmental stability with the same linear dynamic range generated with the uniform or diagonal matrices.

The computer-controlled stabilization of a noisy two-dimensional hyperbolic system

The computer-controlled stabilization of a noisy two-dimensional hyperbolic system is described. A meter-square flexible wire mesh, suspended vertically in tension by rigid boundaries, supported transverse deflections about a planar equilibrium which were destabilized by the application of a transverse electrostatic bias. The number of open-loop unstable deflection modes was adjustable with bias strength. Using information from up to nine electrostatic deflection sensors, a minicomputer manipulated nine electrostatic deflection actuators so as to stabilize the mesh. Linear-quadratic-Gaussian control laws, based upon a truncated normal mode system description and modified to include rate-limited deflection integration, were implemented throughout. Experiments are reported in which the open-loop system stability, the number and location of actuators and sensors used, and the computer sampling rate were variable. Three open-loop unstable modes were stabilized at an electrostatic bias pressure nearly three times that required to initially destabilize the mesh. The limits of this stability, regime and the resulting mesh surface tolerances were found to be consistent with theory. Spillover was experimentally observed to be a predictable cause of mesh deflection destabilization.

An Analysis of Mid-Frequency Resonance Phenomenon in Permanent-Magnet Step Motors

An analytical study on the phenomenon called mid-frequency resonance is described. This phenomenon is frequently observed with pronounced oscillation when a step motor is driven in open-loop mode at relatively high input pulse rate. It limits the operations of the step motors. An analytical method is developed for predicting the behavior of the phenomenon in permanent magnet step motors. Comparison between predicted and experimental result is also presented.

Minimal response time design for linear multivariable sampled-data control systems

The method of minimum, finite settling time design used for single-loop systems is extended to cover multivariable systems. Sensitivity analysis is applied and results of considerable generality are derived which indicate the effects of gain changes and pole or zero movement in the plant transfer functions. A design policy is developed which satisfies the need for low sensitivity in implementation. Further development evolves a design technique in which speed of response can be systematically traded for sensitivity. At the same time the technique satisfies the need to achieve a digital control algorithm of minimal complexity. The method of design has been shown to be particularly relevant to systems with lightly damped open-loop modes and an example of this type of system is analysed in detail.

A Two-Level Model of Driver Steering Behavior

In evaluating the performance of the driver-vehicle system and in establishing design criteria for favorable vehicle dynamics, a quantitative description of driver steering behavior such as a mathematical model is likely to be helpful. The steering task can be divided into two levels: (1) the guidance level involving the perception of the instantaneous and future course of the forcing function provided by the forward view of the road, and the response to it in an anticipatory open-loop control mode; (2) the stabilization level whereby any occuring deviations from the forcing function are compensated for in a closed-loop control mode. This concept of the duality of the driver's steering activity led to a newly developed two-level model of driver steering behavior. Its parameters were identified on the basis of data measured in driving simulator experiments. The parameter estimates of both levels of the model show significant dependence on the experimental situation which can be characterized by variables such as vehicle speed and desired path curvature.

Coordination Concepts in Multilevel Hierarchical Differential Games

This paper presents possible extensions of the usual differential game theory to the case where the players, say the supremal players do not completely govern the plant, but control it only via infimal players who have their own pay-off functions. One assumes that the internal structure of the game is given in the sense that the supremal players cannot define arbitrary decompositions for the system. One further assumes that these supremal players have given programming terminal objectives which they desire to attain. In this framework, the supremal players can only select suitable functions, which are the coordination controls, to coordinate the system for the best. It follows that the problem so defined is simultaneously an optimum control problem and a programming one. The direct coordination mode, the open-loop indirect coordination mode and the closed-loop indirect coordination mode are defined and are mainly based upon a direct reference to the overall system, together with a two-level optimization process. The explicit equations are given in the important case where the comparison criterion is defined in the form of an Euclidean norm, and an illustrative example is solved. This approach would be interesting to apply to the problem of learning and self-learning in optimum control systems for instance, via gradient techniques.

Delayed Closed-Loop Scheme for Stepping Motor Control

An efficient method for control of stepping motor speed and position, the delayed closed-loop (DCL) mode, is described. The new technique permits control of high-speed motor motion by means of a programmed speed-displacement characteristic. The method combines the static-speed control characteristic of the open-loop mode with the stable dynamic behavior of the closed-loop mode. Unlike other schemes for delayed closed-loop control, the present configuration features an extension of delay time to more than one step duration, significantly improving the velocity control. The phase angle can also be varied to ±180°, permitting adequate control of deceleration as well as acceleration. A stability analysis is made of the DCL control method. In an illustrative example, the technique is applied to control of the carriage drive on an experimental high-speed line printer.

Pacing of avian respiration with CO 2 oscillation

Seven awake chickens were prepared in such a manner that ventilatory movements did not affect intrapulmonary CO 2 concentration. This then opens a possible CO 2 regulator loop involving intrapulmonary CO 2 receptors. In an open-loop mode CO 2 concentration could be manipulated externally. The loop could be closed using an analog computer which sensed breathing and controlled intrapulmonary CO 2 concentration accordingly. Breathing movements in this chicken-computer com- bination are seen to lock onto an open-loop administered Fco, oscillation even when this is frequency modulated. Also in the closed-loop mode breathing locks onto a decrease in gas Fco, generated via the analog computer by the bird's own breathing movements. The period between breaths increases linearly with increasing delay added between breathing movement and decrease in FCO 2. Those results fit the model of a ring oscillator. This suggests that the normal respiratory pacemaker consists of interaction between a CO 2 chemoreceptor in the lung and a pacemaker cell in the brain. Birds