Showing papers on "Proportional control published in 1989"

Improving the Performance of Photo-Electrically Controlled Lighting Systems

Abstract: 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.

End-Point Control of a Two-Link Manipulator with a Very Flexible Forearm: Issues and Experiments

Abstract: An important consideration when designing a control system is where to place sensors. For mechanical manipulators, a logical sensor location is at the manipulator end-point where tasks are performed. Unfortunately, when bending flexibility exists between an end-point sensor and a joint actuator, stability and performance are achieved only through a sophisticated control design. Some of the issues involved in utilizing end-point sensing for two-link flexible manipulators are addressed in this paper. First, a modelling technique is presented that properly represents the foreshortening of a flexible link undergoing deflections, as are the resulting terms that appear in the equations of motion. An example illustrates how this technique corrects a simulation that otherwise incorrectly predicts that the manipulator end-point will exceed workspace limits. Next, in order to realize fully the advantages of the assumed-modes modelling method, mode shapes are selected that allow a low-order model to be used effectively for simulation and control purposes. Then, a nonlinear controller, incorporating state feedback and a constant gain extended Kalman filter driven by end-point measurements, is designed and compared to a conventional proportional-plus-derivative controller that uses collocated sensors. Finally, the results are presented from implementing these controllers on the experimental Stanford Multi-Link Flexible Manipulator configured with a rigid upper arm and a very flexible forearm.

Replacing a PID controller by a lat-lead compensator for a robot-a frequency-response approach

Abstract: Because of their simplicity, PD (Proportional-derivative) or PID (proportional-integral-derivative) controllers are widely used with various robot control strategies. For dynamic control of robots, this algorithm can be shown to lead to unsatisfactory tradeoffs between static accuracy, system stability, and insensitivity to disturbances. These tradeoffs become more serious as the sampling rate decreases. By deriving a more realistic discrete-time system model and using frequency-response analysis, a lag-lead compensator is designed and implemented. Both theoretical analysis and real tests are given for the comparisons of the PD or PID controller and the lag-lead compensator. Replacing PD or PID controllers by lag-lead compensators results in a small increase of offline design and tuning effort and online computational load, but the improvements in robot performance are significant. >

Adaptive load control of the central processor in a distributed system with a star topology

Abstract: The author presents adaptive control techniques for controlling the flow of real-time jobs from the peripheral processors (PPs) to the central processor (CP) of a distributed system with a star topology. He considers two classes of flow control mechanisms: (1) proportional control, where a certain proportion of the load offered to each PP is sent to the CP, and (2) threshold control, where there is a maximum rate at which each PP can send jobs to the CP. The problem is to obtain good algorithms for dynamically adjusting the control level at each PP in order to prevent overload of the CP, when the load offered by the PPs is unknown and varying. The author formulates the problem approximately as a standard system control problem in which the system has unknown parameters that are subject to change. Using well-known techniques (e.g. naive-feedback-controller and stochastic approximation techniques), he derives adaptive controls for the system control problem. He demonstrates the efficacy of these controls in the original problem by using the control algorithms in simulations of a queuing model of the CP and the load controls. >

Proportional control valve

Abstract: A proportional control valve has a main fluid passage, a valve portion having a flap, a magnetic element disposed in proximity to the valve portion and mounted integrally in the main passage, a movable body disposed inside the magnetic element and actuated by the magnetic element to directly or indirectly displace the flap of the valve portion and an electric control unit connected to a detector for detecting a characteristic parameter to be controlled, and controlling the movable body in accordance with the detected parameter. This proportional control valve allows a precise and easy fluid flow rate control, as the fluid flow rate can be continuously and precisely varied in proportion to variations in the parameter detected by the detector.

On controller tuning for a flexible‐link manipulator with varying payload

Abstract: In this article experimental results are presented for system identification and control of a single-link flexible manipulator carrying an unknown, varying payload. The control objective is to maintain endpoint position accuracy in the presence of flexure effects after rapid movement due to a rigid body slew-angle commanded position. Various time-domain parameter estimation techniques are used to identify ARMA model representations to be employed in controller tuning schemes for vibration compensation. Only endpoint acceleration measurements and motor shaft angle measurements are utilized in relatively simple PID control schemes, which are tuned as dictated by a varying, unknown payload.

Stabilization of a spinning spacecraft of arbitrary shape

Abstract: A stabilization system (40) for a spacecraft which enables the spacecraft to be stabilized by rotation about any principal moment of inertia axis (x, y). The system includes two pairs of control thrusters (14, 16; 18, 20) for producing positive and negative control moments about two orthogonal axes (x, y) mutually perpendicular to the axis of rotation of the spacecraft. The control system (40) includes rate gyros (42, 46) which provide error signals which are sent to duty cycle modulators (54). The duty cycle modulators (54) provide a pulse width modulated control signal to the control thrusters (14 - 20) to approximate proportional control of spacecraft attitude.

Postural Control of a Monoaxial Bicycle

Abstract: 本研究は, 一つの軸の両端に二輪をもち, その軸で上部構造体を支える形式の同軸二輪車の姿勢制御とその応用に関するものである. この二輪車を倒立振子と車輪によってモデル化し, フィードバック制御系を設計した. 倒立振子に対する制御モーメント, すなわち復元トルクは車輪を制御することによって発生する. 制御の遅れ時間を考慮し, Routh-Hurwitzの安定条件により比例ゲインを求めた. これらの結果を用いて実験を行い, 同軸二輪車の姿勢制御に成功した. さらに, 姿勢制御の結果を利用したゲイン変化法とサーボ指令法の二方法により, 二輪車のサーボ制御を実現した.

Integration proportional controller in servo-control system

Abstract: An integration-proportional controller in a servo-control system comprises in one aspect, an integrator for integrating a deviation of an input speed reference signal from a feedback signal fed back from an object to be controlled, and a proportional amplifier connected with the integrator for amplifying the feedback signal, the integrator including a clamping function in which an output value therefrom and an initial value for the next successive integration are changed, when the output value as a result of integration of the deviation is out of a predetermined proper output region, to the nearest boundary of the predetermined region value. In another aspaect, a saturable integrator is provided for integrating a deviation of an input speed reference signal from a feedback signal fed back from an object to be controlled, a proportional amplifier is connected with the saturable integrator for amplifying the feedback signal, and a deviation clamping device is connected with the saturable integrator for limiting the upper and lower values of the deviation.

Speed governor for small engines

Abstract: A speed regulating governor system (10) is disclosed for a small internal combustion engine having a throttle valve (12) the position of which affects the speed of the engine, wherein the governor system includes a mechanical proportional controller (42) and an electromechanical integral controller (60). The throttle valve is mechanically linked to and controlled by a governor lever (24) that is acted upon by opposing forces provided by a mechanical speed selector (34) and a centrifugal flyweight apparatus (42) which measures the engine speed. Additionally, a solenoid actuator (52) is operably connected to the governor lever to apply a force thereto in response to a control signal (62) generated by an electronic integral controller (60). The control signal is proportional to the time integral of the difference between a desired electrical speed input (126, 128) and the actual speed of the engine measured by an electrical signal (66) generated by an alternator driven by the engine.

Multi-port self-regulating proportional pressure control valve

Abstract: A multi-port, self-regulating, proportional control valve preferably uses a load output feedback system to produce working fluid load output pressures that are proportional to pilot control fluid pressures. In some embodiments, the control valve is programmable and capable of different load output pressures selected either prior to, or during, operation. The control valve apparatus according to the present invention is capable of a center-off or neutral condition that requires substantially no pilot control flow when there in no control valve output flow.

Accurate Position Control of a Pneumatic Actuator

Abstract: We propose a new control strategy for on-off valve controlled pneumatic actuators and robots with focus on the position accuracy. A mathematical model incorporating pneumatic process nonlinearities and nonlinear mechanical friction has been developed to characterize the actuator dynamics; this model with a few simplifications is then used to design the controller. In our control scheme, one valve is held open and the other is operated under the pulse width modulation mode to simulate the proportional control. An inner loop utilizing proportional-plus-integral control is formed to control the actuator pressure, and an outer loop with displacement and velocity feedbacks is used to control the load displacement. Also, a two staged feedforward force is implemented to reduce the steady state error due to the nonlinear mechanical friction. Experimental results on a single degree of freedom pneumatic robot indicate that the proposed control system is better than the conventional on-off control strategy as it is effective in achieving the desired position accuracy without using any mechanical stops in the actuator.

Robust Control of Position and Force for a Robot Manipulator in Non-Contact and Contact Tasks

Abstract: The problem of designing a robust controller for position and force control of a robot manipulator in both non-contact and contact tasks is considered. Using classical dynamics concepts, and under certain assumptions, a mathematical model for non-contact and contact tasks is developed. A controller based on proportional-integral (PI) and feedforward control is proposed for this model. A sufficient condition, which ensures that the closed-loop system is asymptotically stable, and the proposed controller are both presented. Theoretical analysis and numerical simulations have shown that the proposed controller is robust with respect to perturbations in system parameters and joint friction force. It is shown in this paper, that there is no need to change the controller configuration when the robot comes into contact with the environment from free motion.

Joint-space adaptive control of a redundant telerobot manipulator

Abstract: The design of a joint-space adaptive control-scheme for controlling the slave arm motion of a dual-arm telerobot system developed to study the telerobotic operations in space is presented. Each slave arm of the dual-arm system is a kinematically redundant manipulator with 7 degrees of freedom (DOF). Using the concept of model reference adaptive control (MRAC) and the Lyapunov direct method, the authors derive an adaptation algorithm which adjusts the PD (proportional and derivative) controller gains of the control scheme. The development of the adaptive control scheme assumes that the slave arm motion is noncompliant and slowly varying. The implementation of the derived control scheme does not require the computation of manipulator dynamics which makes the control scheme sufficiently fast for real-time applications. A computer simulation study performed for the 7-DOF slave arm shows that the developed control scheme can efficiently adapt to sudden change in payloads while tracking various test trajectories such as ramps or sinusoids with negligible position errors. >

Parallel linkage steering for an automated guided vehicle

Abstract: The computer-aided design of suitable control strategies for parallel linkage steering of an experimental automated guided vehicle is described. The microprocessor-based steering control system is modeled, and stability characteristics using proportional control are investigated by means of describing functions. Although the approximation is coarse, the analysis indicates an upper bound for gain and suggests derivative action for improved control. For better accuracy, a flexible and fast simulation program that makes possible an efficient search for optimal control laws for operation of the vehicle under the constant speed mode and slow-down mode is developed. Time-independent control laws are investigated, and solutions are found that give tolerable tracking over 90 degrees arcs of 0.5 m radius. The simulation results show that time-dependent control laws are essential for improved, nonoscillatory tracking. >

Understanding Modern Generator Control

Abstract: A simple discussion about generator control without bode plots and other sophisticated references necessary to equipment design is presented. Two kinds of control schemes used for most generator drives, droop control, and frequency control are discussed. Synchronous and induction generators, and their differences in control, are also discussed. The operation of generators both connected to and disconnected from the utility grid is also examined. >

Microprocessor-based control of steel rolling mill digital DC drives

Abstract: Algorithms are presented for the digital control of double-loop DC machine drives used for applications where severe constraints on motor speed and position render conventional constant-torque or power control inadequate, such as in steel rolling mill drives. It is shown that the heavy current demand associated with maximal acceleration control can be reduced by using a form of proportional control where, in addition to the conventional inner-loop current feedback, a distance feedback term sets the high limiting value of the speed feedback signal, thus reducing the motor armature current. >

Portable data acquisition and control station for self-tuning control applications

Abstract: Single-input single-output control algorithms are implemented in a HP 9000/350 microcomputer. Especially a new "hybrid" self-tuning algorithm, P-STC, with a fixed proportional controller and a self-tuning part is described. Successful experiments with scalar PI controllers and P-STCs were performed at a pilot paper machine of Tampella Ltd. in Inkeroinen, Finland.

Valvistor based modern servo package

Abstract: Cartridge valve technology offers solutions in the situations where high integration level of hydraulic components are needed, like in the case of linear servo-packages. Valvistor, which is often regarded as a hydraulic transistor, is one of the most modern two-way cartridge valve designs both from the standpoint of the package integration level and the static and dynamic characteristics. In this paper, mathematical and experimental studies are made concerning the application of Valvistor in control of a differential cylinder. In addition, an example of an advanced construction of intelligent actuator is shown both from the standpoint of component packaging and control.

Position Control System Driven by Ultrasonic Motor

Abstract: The responses of position control systems driven by an ultrasonic motor are described One system utilizes a proportional controller and the other a pulse width modulation controller The responses of both systems for various reference positions are measured and discussed

Control method and device for power generating plant

Abstract: PURPOSE: To improve the stability of a power system, in a power generating plant where the steam introduced in a steam turbine is normally adjusted to a prescribed pressure by reversely interlocking the opening of a steam governing valve to that of a turbine by-pass valve according to the control signals determined from the output of a generator and so forth. CONSTITUTION: The subtraction 10 between a target generator output and an actual generator output is carried out for finding out an output deviation, so that a generator output control signal 14A is obtained according to the above deviation. Also subtraction 20 between a target generator frequency and an actual generator frequency is carried out for finding out a frequency deviation so that a frequency control signal 23A according to the above deviation. The addition 24 of these control signals 14A, 23A is carried out to obtain a target valve opening signal 25A, and the target signal 25A is distributed to respective target valve opening signals 28, 29 of steam governing valves 121, 122 and turbine by-pass valves 123, 124. The signal 28 is obtained by multiplying the signal 25A by a proper proportional gain KC through a proportional circuit 26, and the signal 29 is obtained by giving a negative gain -KB of opposite polarity to that of gain KC to the signal 25A. COPYRIGHT: (C)1991,JPO&Japio

Method of controlling clutch in continuously variable transmission

Abstract: PURPOSE:To make it possible to smooth the change-over operation of a clutch at a lower temperature by controlling the clutch pressure by a feed-forward amount in such a way that it is suddenly decreased during a normal start mode in which a continuously variable transmission satisfies a specified limit condition. CONSTITUTION:A control section 82 for changing the duty rate so as to control speed change in accordance with various inputted conditions such as a throttle opening degree, an engine rotational speed, a vehicle speed and the like from first to third rotational speed detectors 72, 76, 80, controls the opening and closing operation of a first primary pressure control three-way solenoid valve 42, a constant pressure control valve 38, a second line pressure control three-way solenoid valve 50 and a third clutch pressure control three-way solenoid valve 58. Further, the control section 82 multiplies an engine torque which is determined in accordance with a throttle opening degree detection signal during normal start mode, by a proportional gain so as to calculate a feed-forward amount for a required clutch pressure. The control section 82 initializes a first feed-forward filter during normal start mode in which a continuously variable transmission 2 satisfies a specified limit condition so as to abruptly decrease the pressure.

Practical Modelling and Control System Design Methods for CAE Systems

Abstract: In this paper, practical modelling and control system design methode for CAE (Computer Aided Engineering) systems are presented. The Partial Model Matching method (PMM) is effective in designing conventional PID (Proportional, Integral, Derivative) control systems used widely in industrial processes, and some extended types of PID control systems such as decoupling PID control systems and digital PID control systems. In order to design a control system by the PMM method, a transfer function for process dynamics that has a simple structure is needed. Furthermore the cut-off frejuency characteristics that determine the stabilty and response charscteristics of the control system are essential for control system design. Thus, an effective modelling method is proposed that identifies a transfer function by the response data that shows the cut-off frequency characteristics exactly and reduces it to a simple Structured transfer function. The combination of the modeling method and the PMM method is applicable to various dynamics, such as processes with delay time, dead time, overshooting, reverse shooting and oscillation. A CAE system developed on a laptop personal computer using the methods is outlined.

Fuzzy CAD for variable structure PI(D) controller

Abstract: A novel robust PI (proportional and integral) controller including differential action is devised. The algorithm is derived on the basis of variable structure system theories. The controller stability is examined by using the Lyapunov stability theory. A simple fuzzy expert system which is a real-time CAD (computer-aided design) system is introduced. Initial controller parameters are interactively determined by using the fuzzy CAD. The proposed CAD is much simpler due to the introduction of the robust variable structure PI(D) controller rather than a conventional CAD for a PID (proportional-integral-derivative) controller, since it is not required to make much effort in parameter identifications. >

Learning control for slewing of a flexible panel

Abstract: This paper studies the applicability of a discrete-time learning control method to the slewing control of a large flexible panel. Among the issues discussed are feasibility of the desired trajectories and their specification schemes, learning control by linear feedback, limitation of the actuator device output, and robustness to parameter changes or modeling errors associated with the chosen learning control design. To demonstrate the effectiveness of learning control, the system is designed with a proportional controller of the base angle only. Then application of the learning control is shown to make the system learn quickly to achieve the desired slewing without residual vibration at the end of the maneuver. Simulation results are reported and discussed.

Dosage of liquids at small feed rates with peristaltic pumps

Abstract: The paper deals with the problems associated with the accurate dosing with peristaltic pumps. The purpose is to achieve precise and a.djustable feed rates and high accuracy of mass. This presents problems because of the inherent pulsation in the flow. Depending on application three types of requirements can be identified: 1. A high accuracy requirement on the end mass and a constant mean flow rate, whereby pulsations over short intervalls are tolerated. 2. A high accuracy of the mean flow rate: whereby pulsations are tolerated. 3 . A high accuracy of the mean flow rate, whereby pulsations are suppressed. Corresponding to these requirements three control schemes are presented.

Output Feedback Control of Linear Multipass Processes

Abstract: An error actuated output feedback controller for a sub-class of linear multipass processes designated as `differential unit memory' is defined. Further, the design of this controller for closed-loop stbility is considered. In particular, a recently developed computationally feasible stability test is used to present some preliminary work on this problem.

Control of the Metal Rolling Process: A Multidimensional System Approach

Abstract: The metal-rotting process is modelled as a delay differential system with noncommensurate delays. Stability conditions for delay differential systems have been recently developed using asymptotic stability tests and the Lyapunov approach. These results are applied to the stability analysis and stabilization of the metal rolling process. Conditions on the gains of finite dimensional controllers such as proportional plus derivative controllers are developed to ensure the stability of the controlled process against delay variations.