Extending the Method for Development of Double-Loop Continuous Tracking Systems to Discrete Equivalents

Context. In combined automatic control systems (ACS) with the principle of control by disturbance, there are difficulties in controlling disturbances in some objects of radio engineering systems and somewhat lower accuracy. This is especially noticeable when the object is affected by several equal disturbances. Taking them into account requires increasing the complexity and reducing the reliability of the ACS. And neglect sharply reduces the accuracy of the system. Therefore, there is a need to develop a method of synthesis of radio technical tracking systems that eliminates the indicated shortcomings.
 Objective. The article presents a synthesis method for high precision radio tracking systems, which are equivalent to combined systems with split control and filtering procedures when the entry useful (preset) action, which is not measured and external disturbances and interferences are present simultaneously.
 Method. Methods of automatic control theory were used to achieve the goal of the research.
 Results. It has been demonstrated that there is a conflict between the conditions for split synthesis of the evaluation (smoothing) filter and the control filter (regulator) in automatic tracking control systems operating with deviation.
 The article offers a solution to the problem of control and evaluation in the framework of two-circuit systems, which are equivalent to combined systems. The second circuit can be presented as a product of a reverse transfer function with an error in the first circuit to the transfer function of Controller, which has a positive feedback from the operator, as well as the reverse transfer function of the control object without integrating links. It is proposed to use for evaluation an evaluation filter with closed filter transfer function instead of an open regulator.
 The characteristic polynomial of a two-circuit automatic control system (ACS) excludes the influence of the stable second-circuit evaluation filter on the stability of the entire ACS. The polynomial of the numerator of the transfer function must have the difference of polynomials by error, which ensures the achievement of invariance.
 A double-circuit ACS is equivalent to a combined one, since it provides the following: invariance of the error with respect to the preset action without directly measuring it; stability of the first circuit with a stable second circuit.
 The synthesized double-circuit ACS is equivalent to a combined one. The author has calculated and constructed the evaluation filter, the influence of this filter on ACS astatism (i. e., on its accuracy) has been analyzed.
 Conclusions. The scientific novelty of the developed method of synthesis of high-precision automatic tracking systems with separate control and filtering procedures in conditions where the controlled value is not measured in the presence of disturbances is as follows. Equivalence to combined systems, in contrast to the methods of differential connections, is achieved not by three, but by two control loops. The practical significance lies in the fact that the proposed method is advisable to use for the construction of surveillance radio engineering systems, where the input useful effect is not measured in the presence of external influences and disturbances. In aircraft control systems.

An approach is proposed for the adequate description of the processes of state change and optimization of complex discrete automatic control systems (ACS), in which the conver-sion of control signals into a sequence of pulses with time modulation is used. Requirements for actuators in many cases of practical use produce the need to use such a conversion to achieve proportional regulation of the output action in accordance with the input control sig-nal. The description of discrete automatic control systems of the specified type is generalized and an equivalent transformation of the discrete equations of their motion is proposed. The specified transformation allowed to take into account the change in the length of the control pulses for the linear continuous invariant part of the automatic control system. The proposed equivalent transformation of the equations of motion for discrete (im-pulse) systems with a constant sampling interval significantly simplifies their mathematical description and requires fewer resources for computational implementation. For automatic control systems with pulse-width modulation of the control signal, the algorithm for synthesis and obtaining the control signal has been improved, namely, the law of changing the polarity of the pulses and the form of the modulation characteristic based on the Lyapunov method. A distinctive feature of the proposed approach is the inclusion in the criteria of optimal-ity of energy costs for control in the form of a dependence on the duration of control pulses. Functional dependencies were obtained in a closed analytical form, which establish the form of the law of pulse polarity change and analytical description of the modulation characteristic of the pulse-width converter of the control signal according to the given criterion and pa-rameters of the invariable continuous part of the ACS. A computer experiment and simulation were performed when solving the test problem. The obtained results of solving the test problem confirm the effectiveness of the pro-posed approach. It was established that when using optimal nonlinear control laws, the qual-ity criterion is improved compared to the applied linear ones.

The algorithm of structural and parametric synthesis of automatic control systems for limitedly uncertain non-linear objects with unstable balance status and right own values in their exit matrix is proposed. The pecu-liarity of the structural synthesis algorithm is that synthesized automatic control systems use differential com-pensating connection with two components. The signal of one of them is proportional to the signal of disa-greement between the required and measured values of the state vector of the system. A signal of another com-ponent is formed by the sign-operated integral feedback on the module of the control influence. The algorithm of parametric synthesis is reduced to solving the problem at a conditional minimum of integral regulatory error when limiting the characteristic frequency multi-member module to an algorithmically linearized system.

In the design and synthesis of control systems in industrial companies, we have to face lots of unexpected problems caused by interactions between control systems with human operators (automated control systems) and control systems with no human operators (automatic control systems). While there are plenty of recommendations for design, synthesis and optimization of automatic control systems, in case of automated control systems the situation is exactly the opposite. Unlike the machine-precision control processes, the human control processes are more or less influenced by the human creativity and many unexpected control interventions which are not easy to assume and compensate. In the article we present our long-term experience we have gained in the industrial contemporary companies when optimizing the material flow control systems. The presented material flow begins at inputs of processing lines and is finished at the outputs of the companies.

The paper presents a new approach for the fuzzy modeling and analysis of automatic control systems in fully fuzzy environment. The proposed technique is based on the normalized fuzzy matrices and is an extension of the Arithmetic and Visual Fuzzy Logic-based Representations developed recently by Gabr and Dorrah. The approach is also suitable for determining the propagation of fuzziness in automatic control and dynamical systems where all system coefficients are expressed as fuzzy parameters. It is simply based on the assignment of corresponding fuzzy levels for parameters uncertainty that is made in a heuristic way circumventing the previous difficulties in assuming probabilistic or membership functions. Implementations of the approach are carried out for solving selected automatic control problems with parameters expressed in fully fuzzy environment. These problems cover fuzzy impulse response of systems, fuzzy Routh-Hurwitz stability criteria, fuzzy Controllability and Observability, and the stabilization of inverted pendulum through pole placement technique. The results demonstrated the robustness of the proposed formulation and illustrated in a systematic way how the system parameters fuzziness effect on output results can be effectively tracked for monitoring and control. Finally, it is pointed out that the suggested Arithmetic and Visual Fuzzy Logic-based Representations opens the door for a unified theory for fuzzy modeling, analysis and design of continuous and discrete automatic control systems operating in fully fuzzy environment.

The object of research is the towed underwater vehicle (TUV) spatial motion, operating as part of the towed underwater system (TUS). The TUV structure does not contain any propulsive devices; it is driven to the motion by the tugboat through the cable-tug. The task of controlling the TUV is provision of the desired dynamics of its translational motion. Manual control mode allows performing only short-term missions and does not exclude the occurrence of operator errors during control. To perform long underwater missions, it is necessary to use automated TUV.For the synthesis of automatic control system (ACS) controllers, the method of minimizing local functionals is used. It allows getting control laws without information about the structure and parameters of the mathematical model of the control object. To study the synthesized ACS, a simulation method using computer simulation is used. It allows assessing the ACS quality without significant financial costs necessary for the marine natural experiment.The ACS of TUV spatial motion is synthesized, it provides sufficient accuracy of control of the vertical and lateral coordinates of the TUV under uncertainty conditions. For its synthesis and operation, information about the structure and parameters of the mathematical model of the control object is not required. The control law, on the basis of which ACS controllers are synthesized, does not contain information on derivatives of a controlled variable. Therefore, the feedback loops of the synthesized ACS have a simple structure compared to the ACSs synthesized using the well-known methods that use the coordinates of the object's phase space.The dynamics of the operation of the synthesized TUV spatial motion ACS was studied at various towing speeds. The duration of the transient processes from the moment the ACS exits the saturation zone to the moment the control error falls within the permissible range and the control accuracy are quite satisfactory. In comparison with the underwater vehicles known spatial motion ACSs, the synthesized ACS does not require a mathematical model of the control object for its synthesis and operation.

A procedure for constructing a computer-integrated system for automating the technological process of processing associated petroleum gas has been developed. Development of the technological process according to the proposed procedure makes it possible to identify and overcome the difficulties encountered in solving the problems of technological calculation and synthesis of an automatic control system. Difficulties are exacerbated by the influence of heavy disturbances in the flow and concentration of associated petroleum gas. Using the procedure, a technological process for processing associated petroleum gases along with an automatic control system has been developed. The technological process was adapted to use in medium oil fields, such as Ukrainian, which are characterized by low bulks and territorial dispersion. This makes it economically inexpedient to design large gas processing plants operating at a fixed load and gas concentration, which are common in the main oil-producing countries. Therefore, the technological process ensures production of methane and propane-butane of a required quality in the conditions of deviation of composition, concentration and flow rate of the streams incoming from wells in a wide range. The automatic process control system has a two-level structure. The upper level is used to ensure operability at heavy disturbances, which is achieved by changing the operation conditions. The lower level ensures stabilization of the process for small disturbances. Two alternative implementations of the automatic control system based on PID controllers and linear quadratic regulator (LQR) were considered. The results of simulation made in HYSYS program show advantages of the cascade system of the proposed structure based on PID controllers. The control system ensures operability in conditions of deviation of gas flow by ±30 %, when the mole fraction of the gas components alters by 30–50 % and when the gas temperature deviates by ±15 °C from the values of working conditions

The work presents a simulation model of a “driver–automation–autonomous vehicles–road” system which is the basis for synthesis of automatic gear shift control system. The mathematical description makes use of physical quantities which characterise driving torque transformation from the combustion engine to the car driven wheels. The basic components of the model are algorithms for the driver’s action logic in controlling motion velocity, logic of gear shift control functioning regarding direction and moment of switching, for determining right-hand side of differential equations and for motion quality indicators. The model is realised in a form of an application software package, comprising sub-programmes for input data, for computerised motion simulation of cars with mechanical and hydro-mechanical – automatically controlled – transmission systems and for models of characteristic car routes.

The article discusses the creation of an algorithm and the synthesis of a two-loop automatic control system for level and density, instead of the current single-loop one. Aim. Density stabilization and stabilization of the flotation machine power supply by creating a two-circuit automatic level and density control system in order to improve the quality of the final product. Materials and methods. Since there is no net lag in the system, the controller is tuned using the parametric optimization method, namely: according to the criteria of modular (MO) or symmetric optimum (CO). The MO/CO criterion is also used to adjust the contour. All automatic control systems are obtained in the MATLAB Simulink software package. Control quality is measured by metrics such as transient time, overshoot, and system error. The first two indicators show the dynamics of the process, and the last indicator shows the accuracy of the system. Conclusion. The finished two-loop automatic control system, developed in the software package MATLAB Simulink, according to the analysis of the obtained process parameters, provides stabilization of the density and level in the agitation tank for flotation.

The software package "MVTU" (Modeling in Technical Devices; in Russian - Modelirovanie V Tehnicheskih Ustrojstvah) is intended for research and design of the systems described by the differential, algebraic and difference equations. Complex technical object is a controlled object, therefore in the package "MVTU", along with the methods of simulation, the methods of control theory are implemented. In terms of features this package is an alternative of package Simulink, which is a part of system of mathematical computations MATLAB. As well as in the package Simulink, in the package "MVTU" representation of mathematical model in the form of block diagram is accepted. Blocks of such diagram are described by the differential and difference equations, continuous and discrete transfer functions, algebraic relations and logical conditions. The package "MVTU" implements the following operating modes. The operating mode Simulation provides simulation of continuous, discrete and hybrid systems, including in real time in the presence of data exchange with external programs and devices. The mode Optimization allows us to find optimum parameters of the designed system. The modes Analysis and Synthesis provide the solution of problems of research and design of control systems with use of frequency and root methods. The paper describes the main features of the package "MVTU" according to the solution of problems of the analysis, synthesis, simulation and parametric optimization of automatic control systems. Examples of the solution of such problems are given. Experience of the solution of a large number of educational, scientific and applied problems showed that the package MVTU doesn't concede by the opportunities to the best foreign analogs.

Subject. System of automatic mobile control of distillation process. Objective. Improving the productivity and energy efficiency of the distillation process by developing an automatic control system that provides mobile control effects on the process, as well as the study of transients in the developed system during major disturbances. Tasks. Development of a system of automatic mobile control of the distillation process, calculation of transients in the developed system, definition and evaluation of quality control indicators. Methods. Methods of simulation digital modeling of automatic control system operation. Results. A system of automatic control of the distillation process has been developed, which provides for discrete and continuous mobile control actions. Discrete effects are changes in the point of introduction of feed into the column; continuous – in changing the ratio of the flow rates of feed flows supplied to the upper and lower parts of the installation. Traditional control effects are also used by changing the heat carrier flow rate in the cube evaporator and irrigation. Optimal traditional and mobile control effects are calculated by the computing control device according to the normalized criterion using a nonlinear predictive model and are realized by influencing the actuators on the supply lines of feed flows, irrigation in the column and the heat carrier in the evaporator. The system involves the use of an adequate mathematical model, for which its periodic identification is performed and the process is monitored by additional measurement of the temperature profile of the column, temperature and pressure on the control plate. In order to maintain the material balance in the liquid and steam phases, it is planned to stabilize the pressure at the top of the column, the levels in the distillate and the cubic product receivers by changing the flow rates, of refrigerant to the condenser, distillate and cubic product. Using the example of a distillation column for separating a methanol-water mixture, the operability of the proposed automatic mobile control system is studied by digital simulation methods. The disturbances consisted of changes in the flow rate, composition, and temperature of the feed. Conclusions. It is proved that the use of the developed system allows to increase the technical and economic indicators of the distillation process and to improve the quality of management. The results can be used in the chemical, petrochemical, oil refining, food industries to control and optimize the processes of binary, multicomponent distillation.

The double loop structure has been implemented to verify the feasibility of human-machine cooperative control in real environment in this paper, which can fully reflect the performance of the controller and realization of the sharing steering control between human driver and automatic control system. The outer loop adopts fuzzy proportional-integral-derivative(PID) controller to deal with different working conditions, on which the complexity of the algorithm is reduced and the real-time performance of the controller is improved. The inner loop adopts the active disturbance rejection controller (ADRC), which can effectively suppress the interference such as drivers’ faulty operations etc. and improve the tracking accuracy and system performance. The stability for extended state observe(ESO) and ADRC is described in theory to ensure the feasibility of the controller in the real world environment. The experiment results show that the human-machine cooperative control system based on the double-loop controller can effectively reduce the lateral error of the vehicle and the steering torque of the driver in the process. And the control performance of the vehicle is improved.

The article is devoted to the modernization of typical cascade automatic control systems with stabilizing and corrective PI controllers. Such automatic control systems, in addition to the main signal (of adjustable value), use an additional leading signal that reacts to the disturbance faster than the main one. The leading signal effectively compensates for internal disturbances arising in the system by adjusting the stabilizing controller. The temperature control system of superheated steam boiler units of thermal power plants may be taken as an example. The task of determining the configuration parameters of such dual-circuit systems is quite difficult. With a relatively low inertia of the internal circuit, the speed of the stabilizing controller is quite high, and transients in it do not affect the quality of regulation in the external circuit with a corrective controller. This makes it possible to calculate the optimal settings of the latter only by the dynamic characteristics of the inertial section using conventional methods developed for single-circuit systems. The main disadvantage of such automatic control systems is that they do not allow, with close inertia of the contours, to significantly improve the quality of working out the main impacts during the jump of the task, internal and external disturbances. To eliminate this drawback, an invariant cascade automatic control system with an internal model is proposed that takes into account the dynamics of both the internal and external contours with an inertial section of the object when choosing the structure and setting up the corrective controller. In this case, the internal model is used to fully compensate for the main feedback of the system when working out the task signal, as well as to isolate an equivalent external disturbance, for which an invariance differentiator is used to compensate. The invariant cascade automatic control system makes it possible to significantly increase the speed and accuracy compared to the standard one.

Advanced Automatic Control and Fault Detection systems are being developed for Navy Submarines and Surface Ships. Within this context a critical concern is the vehicle automatic control system response to the environment, damage that may significantly degrade the vehicle performance, as well as unexpected sensor, actuator, or control surface failures. Such an occurrence may well lead to an automatic control system response that is either inadequate or inappropriate given the current state of the vehicle. In order to maintain mission effectiveness, changes in the vehicle dynamics, as well as component failures must be rapidly detected and recovery actions must be promptly initiated within the automatic control loop. The overall system consists of combining three state-of-the-art techniques—Robust/Reconfigurable Control, Recursive Neural Networks (RNNs), and Fault Detection and Isolation (FDI) algorithms—into a real-time system that provides vehicle monitoring, fault detection, and automatic control of the vehicle from within the executive control loop. The combination of these technologies provides an innovative approach for the identification of both discrete and continuous failures, for differentiating between component failure and environmental influences, and for incorporating model-based fault protection into the autonomous control loop. The current paper describes the use of the RNNs as Virtual Sensors (VS) to provide real-time analytic redundancy of the sensor readings provided to the automatic control system. Since sensor failures will feed directly into the automatic control system, it is critical to check and verify the sensor readings prior to utilization in the automatic control loop since all subsequent commands are predicated on the assumption that the sensed information is correct. As such, a virtual sensor system has been developed which provides complete analytic redundancy of the sensor measurements utilized by the automatic control system. Each sensor reading is checked against real-time simulation predictions of the “true” sensor values and a decision is made as to the validity of the measurement. The sensed values are then either passed on as correct or flagged as being in error and a Virtual Sensor estimate of the “true” sensor reading values are provided to the automatic control system. The results show that the typical sensor failure modes, sensor drift, sensor lock-up, sensor drop-out, sensor data spikes, and sensor noise can be detected and corrected analytically using this approach with zero false positives. A key requirement in developing this system was the capability to avoid reporting false positives, sensor problems, when none actually existed. These real-time systems for Advanced Control and Monitoring can mean the difference between safe, continued operation and potentially catastrophic failures.

Purpose: To select an automatic speed control system of an electric train. To estimate the speed measurement error effects on the traction drive dynamics. To justify the selection and application of the low-pass filter, particularly Butterworth filter. To determine a set of quality criteria for an electric train speed control. To solve the problem of parametric synthesis of automatic speed control system. Methods: Simulation modelling, automatic control theory, optimizations. Results: Negative influence of speed measurement errors on the formation of the traction force control signal and, consequently, on the transient process in the traction drive has been established. As a result of solving the problem of the system parametric synthesis, proportionalintegral rational parameters with mismatch prediction of control law have been determined. The dependence of the value change of the control law parameters on the Butterworth filter order has been established. It has been revealed that with increasing the filter order it is required to increase its cut-off frequency. The inclusion of the Butterworth filter in the structure of the automatic speed control system has been proved to provide smoothing of high-frequency components in the measured speed signal. Practical significance: The structure of the automatic speed control system has been developed taking into account the presence of method error of the measuring device (pulse speed sensor). The simulation results obtained have shown the filters’ efficiency in the control system.