Digital Automatic Control System Research Articles

Analysis of the influence of the discrete period of the zero-order hold of the digital automatic control system on dynamic indicators of control quality

The issue of increasing the accuracy of reproduction of the master signal in a digital system for automatic control of an electric drive in the presence of a zero-order extrapolator in the block diagram is considered. The formation of discreteness in a control system with a zero-order extrapolator is considered. The analysis of the influence of the extrapolator discreteness on the dynamic indicators of the system control quality is carried out. As indicators of the quality of control direct indicators: overshoot and time of the transition process. The necessary relationship between the zero-order extrapolator quantization frequency and the bandwidth frequency of the linear part of the system is shown, which ensures the approximation of the above indicators of the quality of control of a discrete system to those of an analog prototype. The bandwidth of the analog part of the system is determined from the logarithmic frequency response. The article provides a recommendation for choosing the quantization frequency of digital controllers with zero-order extrapolators for multi-loop control systems, for example, built on the principle of slave control systems.

Advanced Algorithms in Automatic Generation Control of Hydroelectric Power Plants

The problem of load distribution between hydraulic units at hydropower plants is a difficult task due to the nonlinearity of hydro turbine characteristics and individual peculiarities of the generation units, in which operating conditions are often different. It is necessary to apply the most up-to-date optimization methods that take into account the nonlinearity of the turbine characteristics. The methods must also consider strict constraints on the operation conditions of the power equipment when searching for the extremum of the objective function specified in the form of equalities and inequalities. When solving the aforementioned optimization problem, the constraints on computing capacities of the digital automatic generation control systems that must operate in real-time mode were taken into account. To solve the optimization task, the interior point method was analyzed and the method of Lagrange multipliers was modified so that it could minimize turbine discharge and active energy losses in the windings of the power generators and unit power transformers. The article presents the simulation results of the developed optimization algorithms and the results of the field tests of the automatic generation control system executing the proposed algorithms. All of the tests showed a fairly high efficiency of the proposed optimization methods in real operation conditions.

Formalization of Functional Requirements for Digital Substation Protection and Automatic Control Systems

Formalization of Functional Requirements for Digital Substation Protection and Automatic Control Systems

Modern Digital Technologies and Automatic Control Systems In Logistics Companies - Digital Logistics

Digitization is one of the most important tools for survival in the new world. Today, business is moving from global digitalization to global adaptation. Business will have to solve the technical issues (hardware, components, software); develop new and replace existing IT services, enhance physical, economic, organizational, personnel, information, legal security The article considers the relevance and importance of introducing modern digital technologies into the activities of logistics companies. Thanks to innovations, many companies have the opportunity to increase their competitiveness and client-oriented approach in the logistics market. The article also contains examples of various automated control systems in certain logistics processes and their application in practice. The use of modern information technologies and intelligent transport management systems is a key area for improving the delivery of goods. The use of modern information technologies and intelligent transport management systems is a key area for improving the delivery of goods so the article considers the relevance and importance of introducing modern digital technologies into the activities of logistics companies. The article also contains examples of various automated control systems in certain logistics processes and their application in practice. Digitalization makes the transportation of goods much simpler, provides flexibility in working with customers and allows one to pay in any currency through various payment systems. In addition to simplifying electronic document management and communication process, digital logistics in the future is considered to use unmanned vehicles and drones. Such facilities provide faster delivery of goods or communication to remote areas when roads are congested. Key words: logistics, digitalization, information technology, automated logistics, digital logistics and technologies, increasing competitiveness and client-oriented approach, logistics market, intelligent transport management systems, multimodal cargo transportation.

Investigation of ACS image stabilization of on-board optoelectronic guidance and tracking devices

Introduction. The movement of the carrier and external factors (the effects of the atmosphere, temperature and pressure) degrade significantly the image quality of the servo optoelectronic systems (OES) and the positioning accuracy of the emitting OES. The issues of image quality improvement and the probability of keeping the image of the observation object (OO) on the optical axis of the servo EOS are considered.Materials and Methods. The development of an automatic control system for an optoelectronic device (ACS OED) involved solving a multi-criteria optimization problem taking into account a number of conflicting technical-andeconomic (TE) requirements. The determination of tolerated dynamic errors (TDE) of image stabilization was a key issue in the development of on-board optoelectronic devices (OOED). Lagrange equations of the second kind and the mixed Gilbert method made it possible to obtain a mathematical model of the CO OED. Then, the decomposition of a two-link ACS with nonlinear cross-couplings in the CO was performed. A functional diagram of the image formation model of the OOED was presented. The parameters of the matrix photodetector and the requirements for the dynamic error of the ACS OED, taking into account the permissible MTF of the OED, were listed. The functions of transferring modulation, as well as linear, harmonic and vibrational shift of the image corresponding to the permissible and achieved TDE were visualized. Logarithmic frequency characteristics were created in the Mathcad environment. The two-link control system of the OED with the specified parameters of the CO for the considered movement was presented as two independent azimuth and elevation control channels.Results. The processes of control of the on-board optoelectronic system in the stabilization and tracking modes were described. To study the dynamics of spatial control of the OOEP in accordance with the ACS methodology, a computer simulation model (CSM) of the digital automatic control systems (DACS) of the OED was developed. It was implemented in the Matlab environment and consisted of CSM CO, drives, proportional-integral-derivative (PID) controllers taking into account non-linearities, a central computing device (CCD), a guidance software device, a CSMcarrier that implemented the equations of motion. Harmonic vibrations of the carrier were described. The errors of tracking and stabilization in the tracking mode with an additional control action introduced in the form of a constant speed were determined. The dynamics of spatial control of the OOED was investigated. A computer simulation model of a digital automatic control system of an optoelectronic device, the results of modeling the DACS OED without considering the board movement, and the processes of OED control subject to movement were visualized.Discussion and Conclusions. The stabilization accuracy was calculated for the studied cases. It was established that the stabilization tens of times exceeded the previously stated indicators, and it tens of times reduced the requirements for the convergence of the laser beam and the laser radiation power when developing the optical path of the product in question. The proposed CSM can be used in the development of the on-board optoelectronic systems. In this case, the application of the presented methodology and CSM will help to reduce labor costs and minimize errors.

European consensus on patient contact shielding

Patient contact shielding has been in use for many years in radiology departments in order to reduce the effects and risks of ionising radiation on certain organs. New technologies in projection imaging and CT scanning such as digital receptors and automatic exposure control (AEC) systems have reduced doses and improved image consistency. These changes and a greater understanding of both the benefits and the risks from the use of shielding have led to a review of shielding use in radiology. A number of professional bodies have already issued guidance in this regard. This paper represents the current consensus view of the main bodies involved in radiation safety and imaging in Europe: European Federation of Organisations for Medical Physics, European Federation of Radiographer Societies, European Society of Radiology, European Society of Paediatric Radiology, EuroSafe Imaging, European Radiation Dosimetry Group (EURADOS), and European Academy of DentoMaxilloFacial Radiology (EADMFR). It is based on the expert recommendations of the Gonad and Patient Shielding (GAPS) Group formed with the purpose of developing consensus in this area. The recommendations are intended to be clear and easy to use. They are intended as guidance, and they are developed using a multidisciplinary team approach. It is recognised that regulations, custom and practice vary widely on the use of patient shielding in Europe and it is hoped that these recommendations will inform a change management program that will benefit patients and staff.

European consensus on patient contact shielding

Patient contact shielding has been in use for many years in radiology departments in order to reduce the effects and risks of ionising radiation on certain organs. New technologies in projection imaging and CT scanning such as digital receptors and automatic exposure control (AEC) systems have reduced doses and improved image consistency. These changes and a greater understanding of both the benefits and the risks from the use of shielding have led to a review of shielding use in radiology. A number of professional bodies have already issued guidance in this regard. This paper represents the current consensus view of the main bodies involved in radiation safety and imaging in Europe: European Federation of Organisations for Medical Physics, European Federation of Radiographer Societies, European Society of Radiology, European Society of Paediatric Radiology, EuroSafe Imaging, European Radiation Dosimetry Group (EURADOS), and European Academy of DentoMaxilloFacial Radiology (EADMFR). It is based on the expert recommendations of the Gonad and Patient Shielding (GAPS) Group formed with the purpose of developing consensus in this area. The recommendations are intended to be clear and easy to use. They are intended as guidance, and they are developed using a multidisciplinary team approach. It is recognised that regulations, custom and practice vary widely on the use of patient shielding in Europe and it is hoped that these recommendations will inform a change management program that will benefit patients and staff.

A Method for Assessing the Stability of Digital Automatic Control Systems (ACS) with Discrete Elements. Hypothesis and Simulation Results

The article presents a new approach to the analysis of the stability of automatic systems with discrete links. In almost all modern automatic control systems (ACS), there are links that break signals in time. These are power controlled switches—transistors or thyristors operating in a pulsed mode and digital links in regulators. Time discretization significantly affects the stability of processes in the automatic control system. The theoretical analysis of such systems is rather complicated and requires a significant change in engineering approaches to analysis. With the improvement of digital controllers and a significant increase in their performance, this problem has practically been forgotten. However, its mathematical “content” has not changed since the 1980s when discreteness began to play a major role in hindering the transition to digital automatic control systems. In this paper, we propose a new approach that consists of interpreting the sampling operation by a link with the proposed frequency characteristic, which determines the suppression of input high-frequency signals. This link greatly simplifies engineering calculations and demonstrates the new capabilities of sampling systems. These possibilities include the rational distribution of digitalization resources—the number of bits and the sampling interval between the regulator channels, depending on the frequency range of the efficiency of these channels. We verify and confirm our theoretical statements through simulations and show how this approach makes it possible to formulate new principles of construction of seemingly well-known controllers—PID (Proportional Integral Differential) controllers and variable structure systems (VSS).

Stability study of digital multi-connected automatic control system

A study of the stability of a multiply connected automatic control system containing digital links by the frequency method is proposed. The stability criterion is based on the system description of the dynamic properties of the system at the level of characteristics of subsystems and characteristics of communication.

Electricy Losses Management in Distribution Network as a Composition of Automated Meter Reading and Control System (AMRCS)

The problem of electricity losses management in distribution electric networks (DEN) operating in conditions of asymmetry of currents and voltages is reviewed. As it is known, the asymmetry factor leads to significant losses of active power and, as a result, decreases the efficiency and technical and economic indicators of the DEN. The purpose of the control is to minimize technical energy losses in the distribution network based on the creation of an automatic control system (ACS) for the process of balancing a three-phase network in the composition of automated meter reading and control system (AMRCS). The latter are currently being widely implemented to automate information processes in DEN. However, AMRCS does not include in its composition technologies designed to solve the problem under review. A method is proposed for constructing a digital ACS controller, the main function of which is to maintain phase currents at the network input at a given level in real time. The concept of the method is based on the idea of the desired redistribution of electricity flows between the phases of the distribution network by appropriate switching of single-phase consumers (customers) so that the minimum spread of phase currents from their specified level is ensured. To achieve the goal of control, criterion functions are constructed that determine the qualitative indicators of the functioning of the ACS. Algorithms for the functioning of the digital controller and the formation of control actions on the subject have been developed. The latter are a digital code containing data on the coordinates of electricity meters of consumers of a three-phase network to be switched to another phase.

Design of Digital Control Systems by Nonlinear Uncertain Objects

Minimum-phase nonlinear objects in the conditions of incomplete information about state variables and nonlinearities of the objects are considered. The design method of the digital automatic control systems in the conditions of uncertainty is offered. The decision is received with application of the asymptotic observers and control on state and impact under conditions of full controllability and observability of the controlled objects. This control provides the necessary performance of the control systems. The digital devices algorithm of digital control system is received by sampling of the found control. The efficiency of the developed method is shown on the numerical example. The developed method can be applied to design of digital control systems of production and technological objects of various assignment.

Synthesizing robust control systems for mechatronic objects with digital state controllers and observers

Currently, digital controllers with state observers are widely applied in automatic control systems for mechatronic objects, which great potential abilities are caused by structural flexibility and developed methods of synthesis. However, during design and practical implementation of the systems there is problem of robustness, associated with parametrical uncertainty of typical mechatronic objects. Most methods for synthesis of robust control systems are based on application of continuous mathematical models and do not take into account specific of digital realization of controllers with state observers. Methods of state space, modal control, digital system design, numerical optimization algorithms and simulation in MatLab environment were used. We propose a method of synthesizing robust digital modal control systems with state observers based on generating dynamic system characteristics within the areas of parametric robustness. Further, low sensitivity of the system to changes in controlled object parameters is ensured by the minimal phase character of the complex controller transfer function, while low sensitivity to changing parameters of the controller itself is ensured by excluding positive feedback in both control and adjustment circuits. Developed recommendations of choosing dynamic characteristics of state controller with observer loops within robustness areas and of forming rational state observer structure allow us to synthesize digital automatic control system with low sensitivity for variation of both control object parameters and inherent controller parameters.

Aircraft Turbine Engine Automatic Control Based on Adaptive Dynamic Models

Abstract One of the most perspective development directions of the aircraft engine is the application of adaptive digital automatic control systems (ACS). The significant element of the adaptation is the correction of mathematical models of both engine and its executive, measuring devices. These models help to solve tasks of control and are a combination of static models and dynamic models, as static models describe relations between parameters at steady-state modes, and dynamic ones characterize deviations of the parameters from static values. The work considers problems of the models’ correction using parametric identification methods. It is shown that the main problem of the precise engine simulation is the correction of the static model. A robust procedure that is based on a wide application of a priori information about performances of the engine and its measuring system is proposed for this purpose. One of many variants of this procedure provides an application of the non-linear thermodynamic model of the working process and estimation of individual corrections to the engine components’ characteristics with further substitution of the thermodynamic model by approximating on-board static model. Physically grounded estimates are obtained based on a priori information setting about the estimated parameters and engine performances, using fuzzy sets. Executive devices (actuators) and the most inertial temperature sensors require correction to their dynamic models. Researches showed, in case that the data for identification are collected during regular operation of ACS, the estimates of dynamic model parameters can be strongly correlated that reasons inadmissible errors. The reason is inside the substantial limitations on transients’ intensity that contain regular algorithms of acceleration/deceleration control. Therefore, test actions on the engine are required. Their character and minimum composition are determined using the derived relations between errors in model coefficients, measurement process, and control action parameters.

DIGITAL AUTOMATIC GAIN CONTROL SYSTEM MODELING

The goal of automatic gain control is to maintain a constant output power level. Automatic gain control systems are used in various communication systems, both analog and digital. However, for all the variety of digital automatic gain control algorithms, the adjustment of the control parameters during the simulation process in reality is often ignored. In practice, this can lead to long-term overloads with a large change of the input signal power. There is also the risk that the model used was designed to work in linear mode only. In nonlinear mode, its behavior may not always be predictable. Research subject. The purpose of this article is to analyze digital AGC system characteristics and to model its operation in Matlab. Method. As part of the study, a Matlab model of hybrid automatic gain control system was developed. Core results. It is shown that the control time of the digital automatic gain control system with a non-linear gain control characteristic does not depend on the amplitude of the input signal. The performance of the proposed digital model is limited by the dynamic range of the linear path and the analog-to-digital converter. The mathematical dependence of the response time of the model on the input signal level change is obtained, in which the time constant of the automatic gain control filter has been replaced by the time constant of the entire automatic gain control system. Practical relevance. A digital model of hybrid automatic gain control system is proposed, which will allow to simulate digital automatic gain control systems parameters for both small and large changes in the input signal level. The results of this work are relevant to the development of digital receivers for communication systems of various purposes.

Modular imaging system: Rapid scan EPR at 800 MHz.

An electron paramagnetic resonance (EPR) imaging system has been custom built for use in pre-clinical and, potentially, clinical studies. Commercial standalone modules have been used in the design that are MATLAB-controlled. The imaging system combines digital and analog technologies. It was designed to achieve maximum flexibility and versatility and to perform standard and novel user-defined experiments. This design goal is achieved by frequency mixing of an arbitrary waveform generator (AWG) output at the intermediate frequency (IF) with a constant source frequency (SF). Low noise SF at 250, 750, and 1000 MHz are available in the system. A wide range of frequencies from near-baseband to L-band can be generated as a result. Two-stage downconversion at the signal detection side is implemented that enables multi-frequency EPR capability. In the first stage, the signal frequency is converted to IF. A novel AWG-enabled digital auto-frequency control method that operates at IF is described that is used for automatic resonator tuning. Quadrature baseband EPR signal is generated in the second downconversion step. The semi-digital approach of mixing low-noise frequency sources with an AWG permits generation of arbitrary excitation patterns that include but are not limited to frequency sweeps for resonator tuning and matching, continuous-wave, and pulse sequences. Presented in this paper is the demonstration of rapid scan (RS) EPR imaging implemented at 800 MHz. Generation of stable magnetic scan waveforms is critical for the RS method. A digital automatic scan control (DASC) system was developed for sinusoidal magnetic field scans. DASC permits tight control of both amplitude and phase of the scans. A surface loop resonator was developed using 3D printing technology. RS EPR imaging system was validated using sample phantoms. In vivo imaging of a breast cancer mouse model is demonstrated.

Development of system of automatic control of robotic arm drive

Currently, the scope of application of robotic systems and complexes is expanding significantly. The introduction of industrial robots is one of the most promising areas of complex automation of production processes, which will significantly increase labor productivity and save people from monotonous, difficult and harmful work. Many tasks are solved by facilitating robotic manipulators to facilitate human performance and to achieve higher quality and accuracy of production. Thus, thanks to the development of automatic control systems, information technologies and their application in the creation of modern robotic systems, the opportunity has emerged to release a person from work that poses a threat to his life and health. When using manipulator robots, an important task is to develop a control system that provides positioned movement of the links of the manipulator. The main task of the automatic drive control system is to form and implement a set of control effects, in accordance with technological requirements. In this work we propose a system of automatic control of the actuator of the manipulator, which provides positioned movement of the manipulator link along a given trajectory. Using the tables of originals and images of typical functions for which continuous Laplace transforms and Z-transforms are calculated, a discrete linear steady-state mathematical model of the robot-manipulator automatic control system is constructed. The parameters of the corrective devices of the system of automatic control of the electric actuator of the robot manipulator were made, which allowed to improve the characteristics of the transient process, namely: to reduce the time of over-regulation and the duration of the transient. The obtained results of the simulation of transients allow to confirm that the synthesized parameters of the corrective devices for the analog automatic control system can be used in the digital automatic control system of the electric actuator of the robot manipulator.

Анализ цифровых линейных систем автоподстройки частоты высокостабильного генератора по радиосигналу глобальной навигационной системы

Анализ цифровых линейных систем автоподстройки частоты высокостабильного генератора по радиосигналу глобальной навигационной системы

Simulation Modelling of an Algorithm for Protection from Skidding and Wheel Locking of Wheel Pairs of Electric Rolling Stock

Modern electric rolling stock is equipped with a microprocessor control system of the traction electric drive and smooth contactless voltage regulation on traction motors. It allows implementing a flexible skidding (wheel locking) algorithm of protection. Untimely detection and location of skidding (wheel locking) processes leads to a decrease of the traction (braking) forces, damage to the wheel motor unit, and increased wear of wheels and rails. The simulation model of the electric rolling stock with the rotational-motor electric drive and smooth zone-phase voltage regulation on the traction electric motor was developed. Analysis of the algorithms for protection from skidding and wheel locking in the mode of traction and regenerative braking was made with the help of the above model. The model contains blocks of the MATLAB system and Simulink extension package: traction transformer blocks, traction motor blocks, digital automatic control system of the traction electric drive, current and voltage sensors, and an output module of the modelling results. Skidding (wheel locking) algorithms for protection from skidding (wheel locking) were considered. Their location is a result of the reduction of the armature current of the traction motors with the skidding (wheel–locking) wheel set. In the traction mode, the reduction of the armature current takes place due to the impact on the armature current regulator of the traction electrical motors, and in the mode of the regenerative braking on the exiting current regulator of the traction motors group with the wheel locking wheel set. The considered protective algorithms enable effective localization of the skidding (wheel locking) processes with a minimum loss of the traction (braking) forces.

Digital PID controller for pneumatic and hydraulic systems

In the development of technological systems with pneumatic or hydraulic drive, the use of automated means for their control is required. At present, automated control tools built with the help of logic controllers are widely used. The logical controller allows to solve a wide variety of tasks with minimal costs, both in terms of cost and time spent for developing the system. So the logic controller ensures the speed of systems with pneumatic or hydraulic drive up to 1 ms or less. With the use of digital automated controls, questions related to the synthesis of PID regulators and the stability of systems with pneumatic / hydraulic drive in the time domain arise. The purpose of this work was the creation and practical implementation of a digital PID controller for controlling the pneumatic / hydraulic system to provide practical recommendations for its use in engineering. The article presents a block diagram of analog and digital control systems with a proportional pneumatic distributor. The implementation of analog and digital PID-controller and optimization of its parameters by an integral criterion is presented. Comparison of analog and digital systems with the PID controller introduced into their composition is made. The quality of these systems is suggested to be estimated in the time domain by the time of the transient process and the maximum dynamic error. Practical recommendations for determining the sampling time of digital systems with a PID controller are given. An example of the developed digital automatic control system for tracking pneumatic drive is shown, its structural diagram, the general view of the control device with the logic controller and the graphic operator interface, which makes it easy to configure the automated control tool and monitor its state. The scientific novelty of the results presented in the article was that the task of investigating the dynamics of a pneumatic / hydraulic distributor with an electric control in the time domain was solved using a mathematical model that included a digital PID controller and a comparison of the results of modeling a digital system with analogue was made, and practical recommendations for determining the sampling time were given.

Model of the Digital Automatic Gain Control System of Pulse-Power Amplifiers with Bipolar Transistors for Transmitter Modules of Radar Systems

Problems in designing the systems for digital automatic control of parameters of pulse-power amplifiers of radar systems are outlined. A model of the digital automatic gain control system of pulse-power amplifiers with bipolar transistors is proposed. This system shapes the leading and trailing edges of a radio pulse and adjusts the gain within the pulse itself in order to maintain the set output power level. The behavior of the proposed model in operation with a long pulse and a train of short pulses is examined.