Showing papers on "Proportional control published in 1996"

Adaptive, High Bandwidth Control of a Hydraulic Actuator

Abstract: Hydraulic servovalve controlled systems contain many time-varying dynamic characteristics that are difficult to model. Controllers for such systems must either adapt to these changing parameters or be robust enough to handle the parameter variations. In order to achieve the highest possible bandwidth, an adaptive controller is developed for the system that uses full-state feedback for simultaneous parameter identification and tracking control. This controller takes into account the hydraulic fluid compressibility with an on-line identification scheme. Experimental results demonstrate a four fold improvement in bandwidth as compared to a conventional fixed gain proportional controller.

Integrated structure/control design of mechatronic systems using a recursive experimental optimization method

Abstract: A recursive experimental design method for simultaneously optimizing both mechanical structure and control is presented in this paper. Control gains are optimally tuned for a given prototype of mechatronic system, and its mechanical structure is physically modified so that control performance can be further improved. The entire control tuning, evaluation, and structure alteration process is repeated until the desired performance goals are achieved. In each iteration, incremental design changes are determined based on a sensitivity Jacobian relating structural changes to performance improvements. The sensitivity Jacobian is updated during the recursive process using the actual data of the design changes. To estimate the Jacobian despite few data points, a pseudoinverse method and a parameter perturbation algorithm, termed singular-value excitation, are developed. The mechanical structure is modified recursively and quickly by using structure reinforcement and rapid prototyping techniques. The feasibility of mechanical structure changes is taken into account in determining the design changes. The proposed methodology is verified through simulation and applied to the design of a robot positioning system. The robot arm structure is modified with regard to stiffness and damping by using steel reinforced epoxy. PD control gains are optimized every time the structure is modified. Through the recursive procedure, an optimal combination of the arm structure and control gains is obtained.

Position-based impedance control of an industrial hydraulic manipulator

Abstract: This paper addresses the problem of impedance control in hydraulic robots. Whereas most impedance and hybrid force/position control formulations have focussed on electrically-driven robots with controllable actuator torques, torque control of hydraulic actuators is a difficult task. A position-based impedance controller is proposed and demonstrated on an existing industrial hydraulic robot (a Unimate MKII-2000). A nonlinear proportional-integral (NPI) controller is first developed to meet the accurate positioning requirements of this impedance control formulation. The NPI controller is shown to make the manipulator match a range of second-order target impedances. Various experiments in free space and in environmental contact, including a simple impedance modulation experiment, demonstrate the feasibility and the promise of the technique.

A new extension of one-cycle control and its application to switching power amplifiers

Abstract: A new extension of one-cycle control is proposed for controlling DC-AC switching converters. Instability, encountered in the implementation, was studied and resolved. An automatic switching-error correction scheme is developed. This control technique overcomes the nonlinearity of DC-AC switching converters, eliminates the crossover distortion, rejects the power source ripple, and achieves a large dynamic range and a wide bandwidth. A half-bridge experimental circuit was built to verify the theory. This new extension is suitable for high efficiency, small volume, and low distortion audio power amplification.

Analytic PIDA controller design technique for a third order system

Abstract: In this paper a new analytical design technique for a proportional, integral, derivative and acceleration (PIDA) controller is presented to satisfy specifications for transient and steady state response of a third order control system. The PIDA controller values are analytically calculated by equating two characteristic equations: one is formed from desired root locations with specifications based on the design criteria, and another one is formed from the nominal control structure. Thus the calculation of values of the controller is so simple. The PIDA controller designs for different third order plant models are shown to illustrate the benefits of the proposed techniques. The proposed controller design techniques are also employed to show the practicality of the technique for controlling AC motor system models.

Feedback linearization and solar pressure satellite attitude control

Abstract: The question of large angle pitch attitude maneuver of satellites using solar radiation pressure is considered. For pitch axis maneuver, two highly reflective control surfaces are used to generate radiation moment. Based on dynamic feedback linearization, a nonlinear control law is derived for large pitch attitude control. In the closed-loop system, the response characteristics of the pitch angle are governed by a fourth-order linear differential equation. Robustness of control system is obtained by the integral error feedback. Simulation results are presented to show that in the closed-loop system, attitude control of the satellite is accomplished in spite of the parameter uncertainty in the system.

Adaptive fuzzy proportional integral power control for a cellular CDMA system with time delay

Abstract: We investigate the use of fuzzy logic control techniques for adaptive power control in a direct-sequence code-division multiple-access (DS/CDMA) cellular system over the mobile fading radio channels with propagation time delay. A fuzzy PI (proportional-plus-integral) control whose input variables are the received power error and error change is introduced to determine each user transmitting power in order to simultaneously equalize all users' signal powers received at the base station and achieve better system stability and control performance. This control strategy can ensure long loop transmission delays without causing the system to become unstable. According to the well-known phase-plane method, the derivation of the fuzzy PI control has been carried out by analyzing the response areas, cross-over, and extreme points of the system step response with apriori knowledge of the dynamics of the CDMA mobile fading channels. For a long time-delay fading process, a methodology is developed to modify the rule base to contain the delay information for reducing the deadtime effects of the process. Moreover, the additional advantages of fuzzy PI control over conventional control theories are: increased robustness in spite of interference and the ability to handle the time-delay process whose parameters are not accurately known. Simulation results show that a good performance can be achieved both in RMS tracking error and traffic capacity by use of fuzzy PI power control, especially in poor interuser interference and long time delay conditions.

Setpoint PI controllers for systems with large normalized dead time

Abstract: This paper derives proportional-integral (PI) control algorithms for first-order plants with time lag. First, the effects of proportional control on overshoot and rise time are analyzed. Then these results are applied to aid in the design of PI controllers that utilize a pole-zero cancellation. New PI tuning methods are proposed for design criteria typical of those found in metal rolling mill applications with large normalized dead time.

Clutch control system particularly for motor vehicle

Abstract: The clutch is operated by a hydraulic slave cylinder (6) with the hydraulic pressure regulated by a proportional control valve (2). The servo pressure is applied in a programmed characteristic over the movement of the clutch to provide a controlled variation of the torque. The system operates automatically or manually. The control takes into account the temperature of the hydraulic fluid and the state of the engine e.g. it makes allowances for cold starting. The transmission slip between the drive and the driven sections of the system is monitored to provide the optimum torque change. The proportional control valve is controlled by a solenoid control.

Gated proportional flow control valve with low flow control

Abstract: A gated proportional control valve is disclosed which allows both high-flow proportional dispensing and precision low flow. The design includes one or more controlled diameter and controlled-shape orifices in the control path, which, when both of the gate valves are opened, allow for consistent low flow dispensing. The gate valves can alternatively be opened or closed to allow proportional dispensing or valve closure. The invention is particularly useful in a fuel dispensing apparatus.

Analysis and design of a proportional plus derivative fuzzy logic controller

Abstract: The objective of this paper is to present the analysis and design of a proportional plus derivative fuzzy logic controller (PDFLC) that combines the mathematical approach with the linguistic interpretation of the control system. The design of a fuzzy logic controller (FLC) generally involves manipulation of controller parameters based mainly on the designer's experience. A mathematical approach is needed to correlate FLC parameters with the system response but without obscuring the meaning of the actual physical action. In this paper, mathematical expression of PDFLC is developed and then used in time domain analysis to see the effect of controller parameter variation on the system response. The results from the analysis provide the basis for the design methodology developed. Finally, the step by step design procedure is presented and then demonstrated with a numerical example.

Tuning PID controller parameters using tabu search algorithm

Abstract: In the design of a proportional-integral-derivative (PID) controller for a process three parameters have to be specified: proportional gain; integral gain; and derivative gain. The performance of the controller directly depends on these parameters. In order to specify the appropriate values of the parameters in a acceptable time a robust and quick method is required. This paper describes a new method for tuning the control parameters of a PID controller. The method is based an the tabu search algorithm which is a general heuristic procedure for guiding search in a complex search space to find global optimal solutions for difficult problems.

Converting a Switching Solenoid to a Proportional Actuator

Abstract: Solenoids are presently used as cheap and robust switching components. These are variable reluctance devices with their characteristics dictated by a highly nonlinear magnetic circuit. This paper describes the research work done on converting a switching solenoid into a proportional device. It first investigates the magnetic characteristics of a solenoid, followed by developing a control model for the device. Based on this model, a dual rate cascade control scheme with a nonlinear force mapper is proposed for proportional control. This scheme is tested out by simulation and implemented on a Digital Signal Processor based controller.

On the robustness of fuzzy control of an overhead crane

Abstract: This paper presents the robustness analysis of a fuzzy logic control (FLC) system of the crab of an overhead crane. The proposed control system has two independent feedback loops: the conventional proportional (P) regulator is used to stabilise crane velocity, while the fuzzy proportional-derivative (PD) controller has been designed to improve damping of the load angle changes during operation at the maximum travelling speed and after the crane stops. Robustness of the system is crucial because the system parameters change under normal operating conditions. Improved robustness of the proposed FLC system may be explained on the basis of the variable structure control theory. The fuzzy control of the nonlinear second order system is designed with a two-dimensional phase plane in mind. We show that the robustness results from the FLC property of driving the system into the sliding mode.

Self-tuning PID control structures

Abstract: There has been much work on self-tuning PID controllers. There are many possible structures for PID controllers. The basic concepts of PID control can be generalised within the same structure but allowing for the control of complicated dynamic systems using advanced control design algorithms. This structure arises naturally from the system description and does not need to be imposed artificially. The concept of PID control can be usefully generalised to make contact with recent methods such as internal-model control and generalised predictive control. One should not start with a PID controller and then decide how to tune it, but rather one should start with a rational design method and system model from which a (generalised) PID structure will then materialise. Recent advances in local model networks using multiple-model self-tuning PID controllers give a neat extension of the basic (generalised) PID structure to handle nonlinear or time-varying systems. The PID concept is alive and well.

Automatic adjusting device for arithmetic control parameter

Abstract: PURPOSE:To make an automatic adjusting device applicable to an open loop system and a closed loop system, and further a cascade control system and to adjust an arithmetic control parameter in a short time during the automatic operation of a plant. CONSTITUTION:This device is equipped with a plant identification part 16 which identifies a plant 14, inputting the output of a PID controller 12 inputting the deviation 11' between a target value 11 and the output 15 of the plant 14, with integral characteristics and an idle time model by using the input 13 and output 15 of the plant 14, and a PID parameter determination part 17 which calculates a proportional gain, an integral time, and a differential time as parameters of the PID controller 12 with the idle time model obtained by the plant identification part 16 and supplies them to the PID controller 12.

Current controller of linear solenoid

Abstract: PROBLEM TO BE SOLVED: To accurately perform current control of a linear solenoid in any temperature environment. SOLUTION: A PI control unit 14 has a feedforward gain KR, a proportional gain KP, and an integral gain KI, and an output voltage value Vr based on the output from the PI control unit 14 is applied to a linear solenoid 4. In the linear solenoid 4, the solenoid current is monitored, voltage/current conversion is performed, a feedback current value ifb is compared with a command current value ir in a current comparing unit 13 and fed back. The outputs of an oil pressure/current converting unit 12, the current comparing unit 13, and the PI control unit 14 are connected to a resistance value calculating, comparing and correcting unit 16, and the data of a storing device 17 can be read to the IP control unit 14. When the difference between ir and ifb is in the specified range, the resistance value R=Vr×1000/ir is calculated, the resistance value of the linear solenoid is found and taken as the feedforward gain KR of feedback control.

Fuzzy-logic controller synthesis for electro-mechanical systems with nonlinear friction

Abstract: We report on preliminary results in developing a new method for the synthesis of fussy-logic controllers for amplitude-sensitive nonlinear plants based on sinusoidal-input describing-function methods. This technique exploits the fact that two traditional classes of fuzzy-logic controllers are, in functional terms, of the proportional-plus-derivative (PD) and proportional-plus-integral (PI) types. It involves the direct generation of the membership functions and output levels based on the "frequency response" of the nonlinear plant in the describing-function sense. The resulting fuzzy-logic controller obtained in this paper includes derivative action in an inner-loop feedback path (nonlinear rate feedback) and nonlinear PI compensation in the forward path; the performance of the closed-loop system is, by design, quite insensitive to reference-input amplitude. An illustration of the method and its effectiveness is provided, based on a prototypical position control problem where a servomotor plus mechanical load are characterized by torque saturation and nonlinear friction.

Control of a chaotic polymerization reaction using linear and nonlinear controllers.

Abstract: Chaos has been found in a number of nonlinear chemical processes including electrochemical reactions, fluidized beds, pulsed combustors, and polymerization reactions. While the control of chaos has recently a received a great deal of attention, the performance of traditional control schemes is poorly understood. Rather than implement a specific chaos control scheme, such as the well-known OGY method, we examine the feedback control of a chaotic polymerization reaction to a steady state using conventional linear and nonlinear control techniques. We show that it is possible to control a chaotic reaction system using a simple proportional controller, a discrete controller, a nonlinear model predictive controller which includes process-model mismatch. The performance of each control scheme is evaluated from the basin of successful control. While model predictive control yields a the most extensive basin and thus the best performance, in all cases the basin has a fractal structure for some values of the control parameter. The implications of a fractal basin to the robustness of the controller and the likelihood of successful control are discussed.

Device and method for selecting control mode in power construction vehicle

Abstract: A device and method for selecting a control mode in a power construction vehicle is disclosed. The device has a control mode select switch which selects a function for setting new matching relations between the control levers and the proportional control valves. A controller sets the new matching relations and stores the new matching relations, and controls the actuators in accordance with the new matching relations. In the control mode selection method, one operational motion of an actuator is primarily selected and displayed on a display means. Thereafter, a voltage signal indicative of a levering angle of a control lever associated with the selected actuator is output, thus setting a new matching relation between the control lever and an associated proportional control valve. The above process is repeated in order to continuously set and store new matching relations between the control levers and proportional control valves associated with the other actuators.

Control method of assist gas for laser machining and device therefor

Abstract: PURPOSE: To provide a method and device for controlling all kinds of assist gases for laser machining without using an expensive flow rate control device by controlling pressure or mass flow rate with a pressure command CONSTITUTION: The pressure or mass flow rate of an assist gas selected from a plurality of assist gasses is controlled by means of a proportional control valve 11; also, a control circuit from the proportional control valve 11 to a discharge part 25 is branched into a pressure command control circuit 15 and a flow rate command control circuit 17; and the assist gas is discharged from the discharge part 25 The pressure command control circuit 15 is made a bypass circuit; the pressure is controlled through the feedback of a pressure value from a pressure sensor 41 provided in the discharge part 25 to control devices 43, 45; and the flow rate is controlled through the feedback of a flow rate from a mass flow rate sensor 35 provided in the flow rate command control circuit 11 to the control devices 43, 45

Self controllable regulator device

Abstract: A self tuning control system and a method for tuning such a system. The system has a controller formed by a PI controller and a proportional control unit with a mixing point therebetween to which the absolute reference valve is connected. The system has another mixing point upstream of the controller to which the reference variable and the absolute reference valve are connected. The self tuning method involves two cycles. In the first cycle the control loop of the controller is closed only through the proportional control unit and the proportional component of the proportional control unit is determined. In the second cycle the control loop is closed through both the PI controller and the proportional control unit and the integral action time and proportional action coefficient of the PI controller are determined.

Fuzzy control in a single-machine system

Abstract: As a new application area we have been tried to apply the fuzzy control concept in discrete event dynamic systems (DEDS) control problems. The fuzzy control of a single-machine system is presented. Simulation studies have been performed on the basis of a descriptive model for investigating the control performance. Two other control approaches, namely proportional control (P-control) and load-oriented order release control (LOOR-control), are employed to compare with the fuzzy control approach. It is concluded that fuzzy control is a practical and effective way to control DEDS. The fuzzy control module developed during this study can be easily adapted for fuzzy control of other DEDS, for example job-shop systems. This paper should be considered as the first step in using fuzzy control concept for the control of DEDS.

Servo controller for motor and control method

Abstract: PURPOSE: To reduce power consumption by interrupting delivery of an operational signal from an integration control system when a motor is in a stop state thereby interrupting delivery of driving power from a drive control system. CONSTITUTION: A difference circuit 10 determines the difference between a target position signal C(t) from a central control means 9 and a feedback signal E(t) from an encoder circuit 11 and delivers an error signal e(t) to a proportional control system A, an integration control system B and a differentiation control system C. Subsequently, a PWM circuit 23 outputs a PWM signal PWM(t) having a duty corresponding to the sum of operational signals R(t), I(t) and D(t) and a drive circuit E delivers a power amplified power signal P(t) to a motor M thus controlling the driving thereof. When the motor M stops, a central control means 9 interrupts a limiter circuit 15 in the integration control system B based on a control signal RS and generates the PWM signal PWM(t) and the power signal P(t) in order to nullify the operational signal I(t). This constitution reduces power consumption under a state where the motor is stopped.

Process and device for operating dynamic-type compressors with regulators with high proportional amplification

Abstract: A process and a device for avoiding regulator instabilities in surge limit regulators for protecting a turbocompressor from surging if a high proportional gain is selected for the surge limit regulator by a blow-off via a blow-off valve The control of the velocity of closing of the blow-off valve over time is performed by a gradient limiter of asymmetric design, wherein no velocity limitation acts in the opening direction, but a freely parameterizable velocity limitation of the closing process of the blow-off valve is provided in the closing direction The gradient limiter is inserted between the surge limit regulator, which receives the control signals on the actual value of flow and the desired value of flow from a subtracter, and the control line for a pneumatic or hydraulic operating device of the blow-off valve

Performance comparison of fuzzy and proportional controllers in the application of image compression

Abstract: In this work, the performance comparison of fuzzy controllers using the MOI (mean-of-inversion) defuzzification method and conventional proportional controllers with respect to accuracy and convergence speed in the application of image compression (JPEG) is given. The simulation results based on 15 USC pictures and various test points indicate that the performance of the fuzzy controller with MOI is less sensitive to its configurations than that of conventional proportional controllers. In additional, the largest performance difference between these two kinds of controllers is in the steep slope area.