Showing papers on "Proportional control published in 1994"

Fast automatic tuning of a feedback controller

Abstract: A feedback controller configured to automatically tune a control system by determining proportional gain, integral time and/or derivative time control parameters based on estimates of process time delay, process time constant and process gain values which are monitored by the feedback controller. The feedback controller further determines control limits for estimating the process time delay based on the resolution of the sampled values of the process output and the standard deviation of the process output during the initial steady-state condition. The feedback controller also estimates characteristic areas for a first-order response based on a first-order plus time-delay model to determine process time constant and process gain values. These process time constant, process gain and process delay estimates are translated into proportional gain, integral time and/or derivative time control parameters based on design relations of the particular feedback controller.

Pattern recognition adaptive controller and method used in HVAC control

Abstract: A pattern recognition adaptive controller configured to dynamically adjust proportional gain and integral time control parameters to minimize integrated absolute errors between a setpoint temperature and a monitored temperature in an HVAC system. The pattern recognition adaptive controller receives a sampled signal representative of the temperature and determines a smoothed signal based on the sampled signal. The controller characterizes a disturbance in the smoothed signal by a damping factor and a closed loop response time. When a significant load disturbance or setpoint temperature change occurs, the controller estimates an optimal gain based on the damping factor, and an optimal integral time based on the response time. The estimated optimal gain and estimated optimal integral time are used to determining a new gain and a new integral time values, to which the control parameters of the controller are then set.

Regularization of descriptor systems by output feedback

Abstract: Conditions are given under which a descriptor, or generalized state-space system can be regularized by output feedback. It is shown that under these conditions, proportional and derivative output feedback controls can be constructed such that the closed-loop system is regular and has index at most one. This property ensures the solvability of the resulting system of dynamic-algebraic equations. A reduced form is given that allows the system properties as well as the feedback to be determined. The construction procedures used to establish the theory are based only on orthogonal matrix decompositions and can therefore be implemented in a numerically stable way. >

Proportional control of a solenoid actuator

Abstract: Solenoids are nonlinear actuating devices normally used in a switching mode. This paper proposes a dual rate cascade control for converting a switching solenoid into a proportional actuator. A fast inner loop current controller and a slower PID outer loop trajectory controller are employed, A simple static nonlinear map is used to partially linearise the system. This method results in a proportional actuator which is effective and practical. >

Dynamic analysis of parallel-module converter system with current balance controllers

Abstract: Dynamic response and stability analyses of a parallel-module power converter system with current balance controllers are described. The state-space averaging method is used to obtain a small-signal model for the dynamic analysis. The root locus method is used to discuss the stability of the parallel system. As a result, instability of the parallel system is observed in the system composed of modules with different circuit parameters. Influence of module parameters on the stability of the parallel system is discussed. Analytical results are confirmed experimentally for a two-paralleled forward power converter system. >

A fuzzy logic supervisor for PID control of unknown systems

Abstract: The design of a fuzzy logic supervisor for proportional plus integral plus derivative control of unknown systems is carried out in this paper. The PID controllers are designed using Ziegler-Nichols tuning rules. Since the Ziegler-Nichols method provides nominal parameter values for the PID controller, the desired system response is not realized without additional tuning. A fuzzy supervisor is proposed to reduce the amount of additional tuning. The objective of the fuzzy supervisor is to gradually increase the derivative gain of the controller as the system error approaches zero. When the error and change in error are in the zero membership regions, the proportional gain is increased to improve the settling time of the system and an integral gain, if required, is added to eliminate steady-state error. Simulation results, demonstrating improvements in the response of the systems with fuzzy supervisor, are presented. >

Control algorithms for fault-tolerant robots

Abstract: When a fault-tolerant robot fails, its fault responsive system detects and identifies the failure. During the recovery process, reconfiguration of the system isolates the fault, and a new system model and a suitable controller attempt to completely compensate for the faulty condition without interrupting the robot's operation. In this paper, the authors address the recovery process for fault-tolerant serial robots when they experience actuator failure. For this purpose, the authors consider three controllers based on PID feedback, sliding control, and parameter adaptation methods. It is shown that the sliding control implemented with a boundary layer reduces the system errors efficiently when the errors are large, and the controller behaves like an ordinary PID feedback as the errors get smaller. Additionally, when failures cause uncertainty in system parameters, inclusion of parameter identification capability in the controller design is suggested. Although the work is valid for a general robot, simulation results are presented on a four-axis robot. >

Force and contact transient control using nonlinear PD control

Abstract: Describes the use of a nonlinear proportional and derivative (NPD) controller for both non-contact transition force control (NCTFC) (zero velocity when contact occurs) and contact transition force control (CTFC) (non-zero velocity when contact occurs). The authors present a gain design method for NCTFC. Simulations and experiments on the Sarcos Dextrous Arm show that PD control becomes unstable for CTFC while NPD control is stable and reaches the steady state quickly. Experiments with human subjects on NCTFC and CTFC are also presented. >

Practical industrial control techniques

Abstract: This paper describes several practical control techniques which are most suitable for industrial control. The discussion is limited to the control of time-invariant linear deterministic systems. Both frequency-domain techniques and time-domain techniques are considered. Among them are PID control, lag/dead control, linear-quadratic control, dynamic matrix control, internal model control, disturbance observation control, variable structure control, fuzzy logic and/or neural network aided control. The basic concept of each technique is reviewed and its merits and drawbacks discussed. >

Variable structure based decentralized adaptive control

Abstract: This paper proposes a model free scheme for the design of a decentralised adaptive control scheme for large scale systems with higher order interconnections. The basic idea is to use a variable structure adaptive controller to guarantee the system stability and to account for the uncertain higher order interactions. The global stability of the overall system is established based on the Lyapunov theory.

Fuzzy logic for vehicle climate control

Abstract: Typical automobile automatic climate control systems use linear proportional control to maintain a comfortable interior environment. In the process of refining these systems, we have found two significant limitations of linear proportional control when viewed from the standpoint of an occupant's subjective comfort: 1) there are certain control situations in any HVAC (Heating, Ventilation, and Air Conditioning) system that are inherently nonlinear; and 2) it is not possible to realize occupant comfort merely by maintaining proximity to a desired temperature. In this paper, we describe a fuzzy logic control system which addresses these limitations by including rules that provide nonlinear compensation, and by allowing the control to be expressed in the same heuristic terms that an occupant would use in describing the level of comfort. >

Neural network control of a non-linear heater battery

Abstract: The unsatisfactory performance of conventional building services controls is frequently due to poor commissioning, and to the inability of conventional controllers to deal with non-linearities and to adapt to long-term changes in the behaviour of the plant. The paper describes a hybrid neural control scheme which is capable of compensating for plant static non-linearities and of adapting on-line to degradation in the plant, but avoids the instability problems that can arise when neural networks are introduced into the feedback control loop. The hybrid controller uses a neural network, which learns the non-linear static characteristics of the plant, to generate feed-forward control action, and a conventional proportional controller, acting as a feedback trimmer, to deal with unmeasured disturbances. Results of a detailed computer simulation of a heater battery are presented; these show that the hybrid scheme can produce more consistent control, and is less sensitive than a conventional PI algorithm to init...

Auto Guided Vehicle Control using Expanded Time B- Splines

Abstract: This paper deals with the controlproblem of an Auto Guided Vehicle (AGV) from a given trajectory. This trajectory is obtained from its B-spline representation profiting the implicit information contained in the B-spline formulation. For this, we manipulate the discrete tmjectory information to construct a second-derivative continuous and smoothed path, which will be included in the control law together with the kinematics of the vehicle. In this paper we propose a new reformulation of B-splines in an expanded time domain instead of the pammetric classical reptvsentation to get the desired approximation. The purpose of this new repwsentation is to include the path inside the control law regardless the kind of controller used. To easily illustrate the utility of the proposed approach we use a simple Proportional controller. the control law that will guide the robot through this path.

Auto-tuning PID control using neural predictor to compensate large time-delay

Abstract: This paper presents a scheme introducing an auto-tuning PID controller with a neural network based Smith type predictor to control nonlinear systems with large time-delay. To model the dynamic nonlinear systems, a diagonal recurrent neural network is applied. A fast RLS type algorithm is employed to train the weights of the neural model on-line. Finally, the presented control method is used to control some nonlinear systems with large time-delay. >

Control of unknown systems using switching controllers: an experimental study

Abstract: In this paper, the problem of implementing the Miller-Davison (1989) self-tuning integral robust servomechanism for the case of constant references and disturbances is considered and examined using an experimental multi-input multi-output apparatus; cases involving both known and unknown estimates of the steady state gain matrix T are considered. In order to improve the speed of response, proportional feedback has been added in both instances, and this has yielded a superior transient response.

Adaptive PID control with neural network based predictor

Abstract: In this paper, a novel approach to adaptive PID control with neural network based d-step ahead predictor is presented to deal with the control problem for a nonlinear process with time-delay. The paper is organized as follows:In section 2, both recursive and non-recursive d-step ahead predictors are presented to compensate for the influence of the time-delay on nonlinear control systems. In section 3, an adaptive PID control strategy with neural network predictor is proposed. Then, a RLS type learning algorithm is described in section 4 to speed up the learning of the feedforward neural network, thus allowing for on-line adaptive control strategies to become feasible. Finally, simulation results as well as the real-time control of a heat exchanger are illustrated.

Fluid control valve for a hydraulic system operating with variable viscosity, contaminated, fluid

Abstract: Problems such as slow frequency response and low reliability when operating with contaminated fluids of variable viscosity are alleviated in a low pressure hydraulic system (10) which utilizes a single stage, electro-hydraulic, clevis-type pressure control valve (40). The valve (40)includes a control piston (106) referenced to a control pressure within a control pressure cavity (60) to provide a feedback of control pressure which converts the valve (40) from an integral to a proportional control device, thereby enhancing stability of the hydraulic system (10). Compensation for changes in fluid viscosity, as a result of changes in fluid temperature, is provided by fabricating a bifurcated portion (98) and/or a metering bridge portion (62) of the valve (10) from materials having dissimilar coefficients of thermal expansion. Exemplary embodiments of a hydraulic system (10) suitable for use in either vehicular or stationary applications involving pressure actuated devices, such as a clutch (16), automatic transmissions or anti-lock brakes, are provided.

Hydraulic control system for an automatic transmission having an R-N-D control valve

Abstract: An R-N-D control valve of a hydraulic control system is disclosed which ensures the prevention of shock that may occur at the time of an "N-R" and an "N-D" manual shift, by unifying a shift control pressure with one valve in the case of an "N-R" shift and an "N-D" shift and first-second speed shift. The present invention discloses that a line pressure generated from a manual valve is changed to a control pressure controlled by the proportional control of a linear valve, and transmitted to each clutch and brake according to the movement position of a spool of a valve by the line pressure.

A Combined Admission and Congestion Control Scheme for Variable Bit Rate Video

Abstract: 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.

Hydrostatic travelling drive with proportional pressure control

Abstract: A description is given of a hydrostatic travelling drive with a closed circuit and pressure control, the hydrostatic drive having at least one variable-displacement pump with adjusting cylinders and a hydraulic motor. The pressure control is here designed as a proportional pressure control and a proportional-pressure valve unit is provided by means of which the proportional pressure control system can be implemented, the said system acting directly on the adjusting cylinders of the variable-displacement pump to produce a travelling speed which is determined exclusively by a torque provided at the output of the hydrostatic travelling drive. The control system furthermore has at least one first and one second individual control element, the first control element controlling the swivel angle of the variable-displacement pump in a proportional manner and the second control element controlling the system pressure in a manner proportional to an input signal and being superordinated to the first control element. The method for controlling hydraulic machines comprises a) proportional control of the swivel angle of the variable-displacement pump by the first control element and b) control of the system pressure in a manner proportional to the input signal by the second control element, the second control element being superordinated to the first.

Automatic adjusting device for proportional plus integral plus derivative control parameter

Abstract: PURPOSE: To provide the device which is applicable irrelevantly to whether a plant is in an open-loop state or in a closed-loop state and does not requires a long adjustment time. CONSTITUTION: This device is equipped with a plant identifying means 6 which inputs the input 3 and output 5 of the plant 4 and identifies the plant with a primary delay plus idle time model and a PID parameter determining means 7 which inputs the model from the means 6 and calculates and outputs the proportional gain, integral time, and differential time of the plant 4 to a PID control unit 2. Thus, the plant identifying means 6 can inputs the input 3 and output 5 of the plant 4 in operation and calculate the gain, time constant, and idle time of the model, so this device is applicable to the open loop and closed loop and usable even when the plant 4 is in operation; and PID parameters need not be determined through trial and error, so the device which does not requires a long time is obtained. COPYRIGHT: (C)1995,JPO

Supervisory fuzzy control design for a magnetic suspension system

Abstract: In this article, a supervisory fuzzy logic based controller is applied to a magnetic suspension system. The control architecture consists of two loops; a pole placement controller is utilized in the internal loop, and a supervisory fuzzy controller with a proportional-derivative structure is embedded in the outer loop to enhance the transient response of the system. This control design is compared in simulation studies with a classical pole placement controller on an example magnetic suspension system. >

Robust control system design for plants with recycle

Abstract: A general recycle compensator, applicable to multivariable (MIMO) plants is derived. Diagonal proportional plus integral controllers ensuring performance robustness are obtained by minimizing a performance index and considering the robustness measure as a constraint in the design. The overall dynamic characteristics of the system resulting from the compensated plant are more favourable than those of the system resulting from the uncompensated plant. >

Adaptive control method for plant and device for realizing the same

Abstract: PURPOSE:To exactly identify the dynamic characteristics of a plant by providing a step to adjust only a proportional gain as the control parameter of a controller based on a step for identifying the gain in the state of excluding disturbance operated upon the plant while using an observer. CONSTITUTION:An operating signal subtracting a plant output Y from a command U by a subtracter 12 is multiplied a proportional gain Kp by a controller 11, supplied to an adder 13, added an identifying signal and supplied to an adder 14. Estimated disturbance TL is calculated from a plant input and the plant output Y by an observer 16 and outputted to the adder 14. A discrete model 17a simulates a plant 10 with the output of the adder 13 as an identifying input X and outputs the model output Y. An identification unit 18 estimates the discrete system 17a minimizing error between the model output Y and the plant output Y, the discrete system model 17a is converted to a continuous system by a discrete system/continuous system converter 19, and a tuning unit 20 automatically tunes the proportional gain Kp and an estimated coefficient Tmm of the observer 16.

Comparison of three approaches on DSP based digital controlled 2-wheeler forward converter

Abstract: This paper presents the design of digital controls of PWM DC-DC converters on a digital signal processor (DSP) based platform. Three digital control approaches are being investigated: discretisation of analog control, digital proportional-integral-derivative (PID) control, and deadbeat control. Simulation results of the three types of control are shown. Experimental results of a 25W 2-wheeler forward converter prototype are presented to verify the design. >

Automatic setting method of control gain for motor and detecting method of backlash

Abstract: PURPOSE:To make the automatic setting of a control gain possible at the optimum value, in which resonance will never be generated with respect to a load having mechanical resonance or backlash, by a method wherein a control system is set considering the mechanical resonance while the control gain is set within a range, in which the backlash will never be generated. CONSTITUTION:A motor 14 is driven at first through constant acceleration driving to operate the inertia of a load. Next, a gain regulating means 2 is regulated and connecting vibration is detected by a current detecting means 12 while a mechanical resonance frequency is measured by a frequency measuring means 13. Sine wave of an arbitrary frequency is inputted from a sine wave input means 9 and the amplitude of an input sine wave frequency constituents, circulated through a control loop, is detected by a waveform amplitude detecting means 8, then, a speed proportional gain 4 is set so that a control system gain becomes one(1) or less in the mechanical resonance frequency within a range in which backlash will never be generated. A speed integrating gain 5 and a position proportional gain 3 are set automatically by the gain regulating means 2 from the speed proportional gain 4 and a load inertia.

Fuzzy PI control algorithm for the multiple effect evaporation station

Abstract: This paper presents a fuzzy PI control algorithm for the multiple effect evaporation station. A specially developed multiple effect evaporation station simulation model was used to verify the performance of the proposed control algorithm. The fuzzy PI control algorithm performance is compared to the classical PI algorithm one, using the square error sum criteria minimization. The classical heating vapor flow control algorithm is discussed, followed by the proposed control scheme based on the existing sensor information and human operator experience. The proposed control scheme simulation results, for both the classical and fuzzy PI algorithms, are discussed. The suggested control scheme is verified at the sugar refinery AIK "Senta" plant. >

Thrust Analysis of the Linear Proportional Solenoid for a Hydraulic Control Valve

Abstract: The linear proportional solenoid (LPS) is an actuator for a proportional control valve used in hydraulic pressure-control devices. The LPS must have a constant thrust over a designated displacement range, and the thrust must also increase in proportion to the exciting current. This paper deals with the effect of using dither to remove hysteresis phenomena, and describes numerical solutions for the thrust F and displacement x, which are characteristics of the LPS. Dither is a useful small-amplitude oscillation which is introduced to overcome the effect of hysteresis. When dither is applied, the maximum hysteresis of the thrust is decreased from 6% to 3%. The LPS consists of four different magnetic materials, and its F-x characteristic was calculated by the finite element method (FEM). The calculated F-x characteristics approximated the measured results to within an error of 2%. A newly proposed LPS, which maintains constant thrust over a broader range, is also described.