Closed-loop Automatic Control System Research Articles

A Single-Cycle Forward-Flybaсk Stabilized DC-DC Voltage Converter Part. 2. Power Stage Control Device

The article addresses the development of a single-cycle single-transistor forward-flyback DC voltage converter. The article’s second part shows the features of constructing a secondary power supply source based on a single-cycle single-transistor forward-flyback power converter stage considered in the article’s first part [1]. The power supply is constructed as a closed-loop automatic control system responding to mismatch of the output voltage from its setpoint value based on the principle of subordinate current control. The PWM controller initial starting scheme with its subsequent auxiliary feeding from the power transformer additional windings is proposed. The results of studying the scheme carried out using computer simulation in the OrCAD software are presented. The proposed scheme allows the device to remain operational even with a relatively poor coupling coefficient between the transformer’s power and auxiliary feed windings. In the OrCAD software, a simulation computer model was developed for a secondary power supply source based on the new structure of a single-cycle single-transistor forward-flyback power converter stage with the proposed method for starting the PWM controller. Based on the results obtained from studying the processes running in the secondary power supply source, time diagrams confirming the circuit operability are presented. The simulation has shown that a sufficiently large output power can be obtained on a single-cycle single-transistor forward-flyback power converter stage.

Effect of Mismatch Prediction on the Control Quality in Closed Loop Automatic Control Systems

Effect of Mismatch Prediction on the Control Quality in Closed Loop Automatic Control Systems

Optimization of the precision gear grinding operation based on integrated information system

In accordance with the principles of hierarchical management, a comprehensive two-level management system is presented for the development and manufacturing of products for the stages of pre-production (the upper level of the management hierarchy) and for the actual production stage (the lower level of the management hierarchy). At the stage of pre-production, the gear grinding oper-ation design on the “MAAG”type machines was carried out. For this purpose, a technique for optimizing the gear grinding parame-ters for a two dish-wheel rolling scheme has been developed, a mathematical optimization model containing an objective function with restrictions imposed on it has been created. The objective function is the gear grinding machine time, which depends on theoperation parameters (gear grinding stock allowance, cutting modes, grinding wheel specification, part material) and the design fea-tures of the gears beingground (module, diameter, number of teeth, radius of curvature of the involutes). The article showsthat at the stage of pre-production,the gear grinding optimizationis a method of operation design. At the stage of actual production, a closed-loop automatic control system with feedback on the deviation of the adjustable value (gear grinding power) automatically supports the numerical power values that were found at the operation design stage, taking into account ensuring defect-free high-performance gear grinding (minimum number of working strokes and maximum longitudinal feeds). At this stage, i.e. when a robust longitudinal feed automatic control system is operating, the optimization carried out at the previous stage (pre-production) sets the functioning algorithm for the adaptive systemwithcorresponding control algorithm. Thus, at the production stage (when the gear grinding ma-chine is running), the operation optimization is a control method. Therefore, it is shown that with two-level control, the gear grinding operation optimization performs a dual function. On the one hand, it is a design method (at the pre-production stage), and on the other –a management method (at the actual productionstage). With this approach, i.e. with the integration of production and its preparation based on a single two-level management, the efficiency of a single integrated design and production automation system is significantly higher due to general (unified)optimization, rather than partialone.

Synthesis of an automatic temperature controller with sequential switching on of the correcting links

The paper presents a method for the synthesis of an automatic control system regulator by means of integral assessment, which provides tuning to the technical optimum in the case when the object of control is a high-inertia process - control of the temperature of the traction motor. The proposed correction scheme assumes that a PI controller and a low-pass filter are connected in series together with the control object. The data obtained as a result of the modeling indicate satisfactory values of the quality criteria of the control process. It was found that overshoot and control time in a closed-loop automatic control system increases with an increase in the temperature setting, with an increase in the initial temperature, overshoot decreases, control time increases, with an increase in the load current of the traction motor, overshoot decreases and control time increases.

Design and Fabrication of a Multi-motion Mode Soft Crawling Robot

This article proposes a novel pneumatic soft actuator, which can perform bending in different directions under positive or negative air pressure. The actuators are composed of multiple airbags, and the design of the airbags is analyzed. A pneumatic soft robot based on these soft actuators is designed and fabricated by 3D printing technology. This robot consists of three soft multi-bladder actuators, one soft sensor, middle layer, bottom layer, front barb, front feet and rear feet. According to the different positive or negative pressure control of the three soft multi-bladder actuators, the robot can perform both linear, crossing and climbing movements. The soft robot has excellent environmental adaptability and can pass through complex environments by combining three modes of motion. Then, we establish the closed-loop automatic control system using soft sensor. The soft sensor can be stretched and compressed as the soft robot’s movement. Finally, the automatic control system is verified by linear, crossing and climbing movement experiments. Results indicate that the robot can pass through complex environments under the closed-loop control system.

Снижение мощности высокочастотных помех в сигнале управления автоматических систем гребенчатыми фильтрами

The article addresses the matter of reducing the power of high-frequency noise in the control signal produced by industrial automatic systems through the use of algorithms implementing the properties of comb filters in microprocessor controllers. The specific features relating to the frequency responses of open- and closed-loop automatic control systems of industrial facilities are analyzed - both taken alone and in combination with the characteristics of comb filters. The frequency properties of three filter groups that are conventionally used in continuous automatic control systems are compared with three groups of comb filters that implement similar functions. As applied to control tasks, such filters include real differentiating sections or first-order high-pass filters, first-order lag sections or low-pass filters, and proportional sections. The ratios between the parameters of continuous filters and comb filters at which their frequency properties coincide in the operating frequency band are determined. These ratios known, it becomes possible to synthesize the controllers of systems using the existing techniques. It is shown that the amplitude-frequency responses of comb filters have dips in the high-frequency band, due to which the high frequency noise power is finally decreased by up to 30%. The advantage of comb filters in control systems lies in simplicity of implementing them in digital form in a microprocessor controller. The application of comb filters in automatic control systems makes it possible to cut undesirable harmonic noise of large amplitude in the control signal.

English

A prototype of a real-time closed loop automatic control system has been successfully developed to suit trickle irrigation systems management. The control system was designed to manage the irrigation system based on collecting data through soil moisture sensors located at three different locations acting each third of the lateral to put the effect of emitters’ flow rate variation along laterals on soil moisture content distribution in consideration. Soil moisture content which will be used to start and stop the irrigation process will be based on the average of three sensors’ readings. Required inputs to manage the irrigation system were soil field capacity (FC), permanent wilting point (WP), and percentage of moisture allowed depletion (MAD). Irrigation process will begin when the soil moisture content equals the desired percentage of available water and it will stop after reaching soil field capacity. The system was provided with ability to check some defects that are related to the irrigation system like clogging, poor uniformity, and water pumping failure. Laboratory assessment showed that the control system has applied the design considerations and is expected to save irrigation time if implemented with low or poor uniformity trickle irrigation networks when compared to high uniformity networks. The study recommended evaluating the effect of this control system implementation in field especially with trickle irrigation networks which show poor uniformity to use the potentials of the control system to predict emitter clogging, and poor uniformity which are mostly appear in such irrigation systems. Key words: Automatic control, closed loop, flow rate variation, modern irrigation systems, real time. &nbsp

SYNTHESIS OF THE NOISE IMMUNE ALGORITHM FOR ADAPTIVE CONTROL OF ORE CONCENTRATION

Annotation Context. Consideration of the transient process characteristics under current industrial conditions, i.e. a controlled object’s static and dynamic characteristics when forming controlling impacts in automatic control systems of ore grinding and sizing is one of the advanced ways to increase their efficiency. Variations in characteristics of initial materials and equipment conditions while changing a command value in closed-loop automatic control systems (ACS) result in transient processes when the granularmetric composition of output products of grinding and sizing aggregates change in a wide range. It leads to additional losses of the recovered grade. Duration of transient processes depends on how the controlled object’s current condition (its static and dynamic characteristics) corresponds to the controller’s adjustment in the ACS. It causes the necessity to readjust the controller’s parameters from time to time that is done in the adaptive ACS to the best advantage. The authors suggest an algorithm of noise immune correction of the controller’s parameters in the closed-loop automatic control system, which is based on preliminary identification of the controlled object’s static and dynamic characteristics in accordance with parameters of the transient process starting in the closed-loop ACS of the transient process. There are determined limits to its applicability at concentration plants. Objective. The research aims to develop a noise immune algorithm of adaptive control over objects with variable static and dynamic characteristics on the basis of the controlled parameter value and the rate of its changes on the initial stage of transient processes in the closed-loop ACS. Method. Current approaches and methods of improving ore concentration control are analyzed to substantiate the research topicality, goals and objectives. The adaptation algorithm for local ACS of ore concentration is synthesized and analyzed by methods of analytical design and computer simulation. Conclusions. The theory of forming specified parameters of transient processes in the closed-loop ACS by means of objects with variable static and dynamic characteristics on the basis of the controlled parameter value and the rate of its changes on the initial stage of these processes is developed in the present research. It allows synthesizing adaptive ACS, in which the error ratio in the transient process reaches zero in a minimum of time without changing its sign subject to disturbances and noises.

DETERMINATION OF PULSATION FACTORS OF THE SYSTEM OF SUPPRESSION OF INTERFERING HARMONICS OF A SEMICONDUCTOR CONVERTER

Purpose. The purpose of the paper is to define the pulsation factors of a closed-loop automatic control system (ACS) of interfering harmonics containing a semiconductor converter with double-sided pulse-width modulation (PWM), as well as confirmation of theoretical assumptions about possibilities of self-compensation of pulsation factors’ influence in the system with double-sided PWM. Methodology. The research was conducted with the usage of classic electric circuit theory, frequency analysis methods, generalized function theory. Results. The obtained expressions mathematically relate pulsation factors, value of the damping coefficient and manipulative variable for different frequencies of interfering harmonics in the system with double-sided PWM. The research concerned harmonics with frequencies 100, 300, 600, 900 and 1200 Hz as the most significant constituents of the output voltage of a 12-pulse semiconductor converter. The obtained expressions allow taking into account settings of the selective link and its approximation on the level of supreme frequencies with aperiodic link. Originality. The research has experimentally proved theoretical assumptions about self-compensation of pulsation factors in the system with double-sided PWM. It has been shown that the damping coefficient has a low-impact influence on the values of pulsation factors. It is caused by the pass band of the selective link, which is included in the closed-loop control system of harmonics regulation. Practical value. Application of the research results can contribute to the development of the closed-loop control system for effective attenuation of interfering harmonics in direct current contact wire without interfering in the power part of the semiconductor converter. Besides the possibility to regulate output voltage, it will also help to solve the problem of electromagnetic compatibility of a traction substation semiconductor converter with contact wire. The application of the developed closed-loop control system will as well provide for decreasing the size of the filter in the direct current traction substation unit.

Analysis of dynamic characteristics of the active filter-stabilizer

At the railway sections with intensive and high-speed train traffic, it is advisable to use active stabilizer-filters to increase efficiency of DC traction power supply systems. They are introduced into converter units of traction substations to ensure active filtration and stabilization of the output voltage. The active filter stabilizer consists of a voltage converter based on a capacitive energy storage unit and is connected in series with the main rectifying unit of the traction substation. The voltage converter with a two-way pulse-width modulation simultaneously forms a voltage for compensating harmonics and deviations of the mean value of the rectified voltage with respect to the specified voltage. It was established that the voltage converter of the active filter-stabilizer with two-way pulse width modulation for small values of the control signal increment is an amplitude-pulse second-order modulator. In this converter, information is transferred by two channels having static and dynamic transfer coefficients. Dynamic connection between the increments of the input and output signals of the active filter-stabilizer converter is of a variable character at each interval of discreteness of the pulse-width modulation. This property of the voltage converter is called forth by the changes in the static and dynamic transfer coefficients which must be taken into account when describing dynamic processes in closed-loop automatic control systems.

Determining direct measures of performance based on the location of zeros and pole of the transfer function

An analysis is made of the effect of zeros and poles of a closed-loop automatic control system on its direct measures of performance: overcontrol and control time. The necessity of determining the dominant poles in the root-locus plane is shown. A criterion for the ɛ-dominance of the components of the transient function of automatic control system is presented. A method for calculating direct measures of performance based on the location of zeros and poles of the system is developed. Numerical examples are considered.

Modified technique of automatic and automated tuning of thermal-engineering process controllers

A technique of automatic optimization of tuning parameters of the closed-loop automatic control system in the course of operation of the latter is presented. This technique is based on the use of a new correlation for calculating tuning parameters of controllers from the coefficients of a transfer function of the object to be controlled. Simple analytical dependences are given that do not require large computer capacities and can easily be incorporated into a microprocessor-based controller, which in this case is converted into a self-tuning device.

A comparison of the efficiencies of the maximally rapid-response prognostic algorithm and a PID algorithm in a closed-loop automatic control system

Results from synthesizing a maximally rapid-response control algorithm in a closed-loop system for two groups of state variables and prediction schemes are presented. The control quality and sensitivity of systems equipped with time-optimal and PID controllers are analyzed by way of comparison on the example of calculating a system for automatically regulating the temperature of superheated steam in a TPP-210 once-through boiler designated for operation with a K-300-240 turbine.

New Concept of Automatic Control for a Passenger Car Clutch

This paper highlights the main functions of clutch automatic control systems. These are: forced clutch disengagement during gear shifting and when the engine falls below its minimum operating speed; forced clutch engagement under conditions of increasing engine speed or vehicle speed at a preset level or at a definite throttle position; adjustment of clutch friction torque, depending on the control parameter used. To achieve this, a closed-loop automatic control system is required. The system compares control signals with feedback from a selected parameter and generates commands for changing clutch friction torque. At present some automatic clutch systems use either the position of the accelerator pedal (‘Drivematic’ and ‘Guidosimplex’) or engine speed (ACTS) as the control parameter. The feedback parameter in these systems is the position of the clutch drive element. Comparison of the two systems shows that those using engine speed as the control parameter are more advanced, although their design is more complex. Engine speed is also used in the system of automatic electrovacuum friction clutch control (EPS) designed at the Central Automobile and Automobile Engine Scientific Research Institute (NAMI), but the principle of operation is totally different from existing systems. Particular features of this system are as follows: all necessary modes of automatic control are provided by only one multi-function electromagnet acting on the vacuum valve in the clutch actuating servo chamber; the feedback is dependent on the position of the clutch actuator and is provided by a spring acting on the armature of the valve drive electromagnet—the force of this spring changes in proportion to the position of the clutch actuator; clutch friction torque control as a function of engine speed is provided by changing the current strength in the electromagnetic winding—these changes are initiated by the electronic control unit of the automatic control system. To achieve the optimal performance of modern high-speed engines in combination with an automatic clutch system, all elements of the clutch control system must have minimal delay in converting input signals into control signals. This requirement resulted from an investigation of the EPS mathematical model comprising three non-periodic dynamic elements. The same results were experimentally proved when amplitude and phase frequency characteristics of the control system were measured. It was shown in particular that the time constants of dynamic elements must not exceed 0.04–0.06 s. This required the application of a brand new engineering circuit for designing the EPS electronic unit. The EPS system is now in mass production and is standard equipment for some models of small passenger cars manufactured in the former Soviet Union. The system has been patented in the United States, Japan, Germany, Great Britain, France and Italy.

Analyzing the effect of noise on the performance of a closed-loop automatic control system

Analyzing the effect of noise on the performance of a closed-loop automatic control system

New magnet power supply of the Birmingham proton synchrotron

This paper describes the new power supply of the Birmingham proton synchrotron which is used to produce the required field-density waveform in the main magnet air gap. After discussion of the original power supply and its control system, the design of the new power supply is described. This is a closed-loop automatic control system incorporating one loop to accurately control the field-winding currents of the two paralleled main generators, with a second overall loop of a digital nature which modifies the control program in response to preset magnet field densities. The resulting improvements to the synchrotron performance are indicated.

A thermionic rheostat for automatic control

The paper describes an experimental thermionic rheostat in which the spacing between the two thermionic cathodes is controlled by rotating the valve while one cathode is held stationary by means of an external permanent magnet. The valve has a small receiving-valve envelope and will control a.c. loads of up to 60 watts when operated as a series resistor from 240-volt mains. Three experimental closed-loop automatic-control systems are described whose electrical circuits consist simply of experimental valves actuated by mechanical error signals and controlling the current delivered to a.c. motors: the systems are a position control, a velocity-integral control for moving materials and an air-flow control.