Synthesis of towed underwater vehicle spatial motion automatic control system under uncertainty conditions

Synthesis of automatic control systems (ACS) of nonlinear objects is a well-known scientific problem. The method of inverse dynamics makes it possible to synthesize high-precision ACSs of nonlinear objects. However, under conditions of uncertainty, control quality is significantly compromised and ACS does not fulfill the set task. The result of present research is the further elaborated method of inverse dynamics for the synthesis of high-precision ACS of nonlinear objects under conditions of uncertainty. We have synthesized a generalized structure of the inverse control law as a basis for control of nonlinear objects under conditions of uncertainty. Under this structure, the inverse control law is built based on an imprecise inverse model of the object of control and contains an uncertain component of controlling influence to compensate for uncertainties. We have synthesized a law to compensate for uncertainties based on the method of minimizing local functionals. It includes an imprecise model of the object of control and ensures that its output approaches the controlled magnitude. The compensation law makes it possible for ACS to operate under conditions of uncertainty and, at the proper choice of reference models, to provide for a high dynamic accuracy in control over a nonlinear object. We have synthesized ACS of the vertical movement of a tethered remotely operated underwater vehicle. The synthesis was implemented based on an imprecise model of the object of control. The model's order was one order of magnitude less than the object’s order; part of the model responsible for generating a controlling force was considerably simplified; the disturbing influences of a tether-cable were not taken into consideration. Thus, the structural and parametrical uncertainties were accounted for. The dynamics of ACS transient processes were studied based on computer implementation of the model of one-dimensional motion of a remotely operated underwater vehicle as a third-order object taking into account the disturbing influence of a tether-cable. Results of computer experiment showed high dynamic accuracy of ACS under conditions of structural and parametrical uncertainties of the control object's model under the influence of uncertain disturbances of a tether-cable

The towed underwater system is one of the fixed assets of the study of water areas. The effectiveness of its application depends on the characteristics laid at the design stage. The main task of the towed underwater vehicle (TUV) is the motion of technological equipment. Therefore, it is important to ensure the specified dynamic properties of the unit and automate the control of its motion. In the paper the typical forms of the unit are analyzed, the features of their control at small depths are set. TUV control is carried out in conditions of uncertainty. Therefore, the design of an automatic control system (ACS) for its motion is proposed to be carried out using the appropriate synthesis method – the method of minimizing local functionals. The control law contains integral components and, under the constraints of control actions, generates the problem of integral saturation. To eliminate the integral saturation in the work, the condition integration method is improved. On its basis, the control law and the structure of the controller of high dynamic accuracy of a second-order nonlinear object are synthesized. It is the basis for the synthesis of ACS controlled degrees of freedom of the underwater vehicle in conditions of uncertainty. Usually TUVs contain two degrees of mobility. Translational motions of the unit are generated by changing its angular orientation. The paper synthesizes TUV controllers of pitch and roll based on the control law of the second order. Each control signal of the unit can affect both the roll and the pitch of the unit, which leads to decrease in the quality of control in general. To coordinate the work of controllers, a method is proposed, which is based on adjusting the initial conditions of the controller with greater error. On its basis, the automatic control system of the rotational motion of the unit is synthesized. It provides high dynamic precision control of two-dimensional rotational motion of the unit in uncertainty and is the basis for the ACS synthesis of its translational motion in space.

There is developed a specialized simulating complex for computer-aided study of the efficiency of automatic control systems for the underwater towed system «carrier ship — tether winch — tether — towed underwater vehicle». The complex includes mathematical models of the dynamics of a marine moving object, flexible connection and tether winch. The former is used to simulate the spatial motion dynamics of a towing vessel and a towed underwater vehicle as solid bodies in a water flow. Tether simulation employs a method of simulating a flexible connection with automatic control of the axial motion of its elements, which makes it possible to account for the dynamics of the change in the length of its released part. The model of the tether winch dynamics provides simulation of the tether release and gathering. The simulation complex enables studying the spatial motion of a towed underwater vehicle in the water column in relation to the towing vessel as a control object at the dynamic change of the length of the released part of the tether.

The study is based on the use of the discrete time equalizer method for the synthesis and practical implementation of an automatic speed control system of a direct current electric drive. A laboratory research bench was created to carry out experimental research. The synthesis of automatic control systems by the discrete time equalizer method differs from the traditional subordinate coordinate control or the generalized characteristic polynomial method in complete rejection of the use of the desired characteristic polynomials. This approach allows obtaining the desired dynamic and static properties of the system solely on the basis of the desired transition function, which should be close to the natural character of the transition processes (monotonic, aperiodic or oscillatory). The Code Composer Studio integrated design environment allows practical implementation of the proposed discrete time equalizers, the inverse model of the control object, and the inverse transformation modification unit in the form of special routines for the Texas Instruments TMS320F28335 microcontroller – macros in the C/C++ programming language. The main body of the control program, constructed in accordance with the developed functional diagram of macros interaction, made it possible to carry out the experimental studies using both the main control channel with one discrete time equalizer and the combined control with two discrete time equalizers (main and compensating). Since the entire program code used in the research was written in the high-level programming language C/C++ using object-oriented approaches, it is hardware independent of the microprocessor type and can be transferred easily to another hardware base

The definition of a new class of control objects is proposed. It is an underwater complex with flexible tethers (UCFT) for which there is the need to automate motion control under uncertainty and nonstationarity of own parameters and external disturbances. Classification of marine mobile objects and characteristics of the flexible tethers as UCFT elements is given. The basic UCFTs configurations that are used in the implementation of advanced underwater technologies are revealed. They include single-, double- and three-linked structures with surface or underwater support vessels and self-propelled or towed underwater vehicles. The role of mathematical modeling in tasks of motion control automation is shown. The tasks of UCFT mathematical modeling are formulated for synthesis and study of its automatic control systems. Generalized structures of mathematical models of UCFT basic elements are proposed as the basis for the creation of simulating complex to study the dynamics of its motion. The tasks of UCFT identification as a control object are formulated. Their consistent solution will help to obtain a UCFT mathematical model. The basic requirements for UCFT automatic motion control systems are determined. Their satisfaction will ensure implementation of selected underwater technology. Areas of development of synthesis methods of UCFT automatic control systems are highlighted.

The paper is devoted to a problem of synthesis of the robust control system for a distributed parameters plant. The vessel descent-rise device has a heave compensation function for stabilization of the towed underwater vehicle on a set depth. A sea state code, parameters of the underwater vehicle and cable vary during underwater operations, the vessel heave is a stochastic process. It means that the plant and external disturbances have uncertainty. That is why it is necessary to use the robust theory for synthesis of an automatic control system, but without use of traditional methods of optimization, because this cable has distributed parameters. The offered technique has allowed one to design an effective control system for stabilization of immersion depth of the towed underwater vehicle for various degrees of sea roughness and to provide its robustness to deviations of parameters of the vehicle and cable’s length.

Structural analysis and parametric synthesis of automatic control system of initial oil refining technological process on AVT unit is produced with engineering design procedure based on alternance parametric optimization method.

The solution of inverse dynamic problems using the symmetry principle of structural schemes can be a basis for the synthesis of automatic control systems of technical objects. This approach requires compensation of the dynamic properties of the control object. Most scientific papers idealize the object, that is assume that its dynamic characteristics can be fully compensated by controllers. The impact of transfer functions of modifying links on dynamic and static characteristics of automatic control systems is also understudied. The possibility of using methods for solving inverse dynamic problems for the synthesis of automatic control systems of technical objects is investigated. The mathematical modeling confirmed that ideal tracking of inputs under the full compensation of dynamic properties of the control object is impossible in real systems. The rules, which allow determining the inverse model of the control object directly by its structural scheme in the first canonical controllability form, without having to convert differential equations, are formulated. The modified symmetry principle of the structural schemes, which lies in introducing the integrating link to a direct branch of the closed system, which is included consistently with the inverse model, and provides formation of achievable dynamic characteristics desired with a limited gain is developed.

This section of the study proposes the conceptual foundations for the use of artificial intelligence in intelligent decision support systems. In the course of the research, the authors:– justified the feasibility of using artificial intelligence theory for processing heterogeneous data in automated control systems;– developed a methodology for data distribution in automated control systems;– designed a model for evaluating the process of heterogeneous data processing in automated troop control systems using expert information;– improved the methodology for configuring an information system to evaluate the process of heterogeneous data processing in automated control systems under conditions of uncertainty. The analysis conducted in the study established that the application of fuzzy graphs and the mathematical apparatus of fuzzy logic in decision support tasks for data distribution and the evaluation of heterogeneous data processing under various conditions, including uncertainty, enables the distribution of data among elements of automated control systems based on the importance of the elements and the number of features in real-time. The methodology for rational data distribution based on the importance of automated control system elements and the number of features in such systems under conditions of uncertainty has been improved. This methodology differs from existing ones by combining the mathematical apparatus of information theory, fuzzy logic, and expert evaluation, enabling the formalization of features in a unified parameter space and the intellectualization of information processing processes. A quantitative assessment of the proposed methodology’s efficiency was conducted. The results of this assessment demonstrated that data distribution among the elements of automated control systems based on importance and the number of features using the proposed methodology improves the timeliness of data processing and decision-making regarding the state of the heterogeneous data processing process by 15–17 %. An enhanced methodology for configuring the information system for evaluating the heterogeneous data processing process in automated control systems under conditions of uncertainty, utilizing a genetic algorithm, was developed. This methodology addresses limitations of other methods in varying specific features while holding other indicators constant, thus improving the efficiency of the developed information system for evaluating heterogeneous data processing in automated control systems. The scientific outcome is the improvement of the genetic algorithm for differentiated tuning of the fuzzy knowledge base of the information system for evaluating heterogeneous data processing in automated control systems based on posterior data. A quantitative assessment of the improved methodology’s effectiveness was performed. The results indicated that the proposed methodology enhances the timeliness of configuring the information system for processing heterogeneous data in automated control systems under conditions of uncertainty.

The paper is devoted to a problem of synthesis of the automatic control system of a damping winch. The vessel descent-rise devices are used for vessel heave compensation and immerging depth stabilization of a towed underwater vehicle. Most of them have essential disadvantages. First, a cable destructs during its bending strains on descent-rise device’s blocks. Second, a power of such device increases due to the compensation function. To eliminate these disadvantages it is offered to use a special damping winch. It is on the underwater vehicle. There are two controllers in the suggested automatic control system. The rope’s tension controller is used for a heave compensation function of the damping winch and the rope’s length controller is used for immerging depth stabilization of a towed underwater vehicle. For optimization of controllers the standard coefficients method with binomial decomposition and an optimal module method were used. Due to the offered approach vertical displacements of the underwater vehicle are reduced ten times at any sea state codes and stepless depth changing for a towed underwater vehicle is provided.

Synthesis of automatic control systems (ACS) of spatial motion of underwater systems with flexible connections (USFC) forms the actual scientific problem. Own nonlinearity remotely operated underwater vehicle (ROV) enhanced nonlinearity flexible connections that make up USFC. Synthesis of ACS and USFC link forms the basis for automatic control of both onelink and multilink USFC. The method of the formalization of USFC structure is in the form of a graph model. It is represented on the basis of defined-controlled units of USFC. The method of inverse dynamics is synthesized from the regulators spatial movement of TPA and cable winches to control the length of the flexible part of the issued bonds. A BAC USFC link, which includes TPA, a cable winch and synthesized regulators, is the basis for the automation of spatial movement of onelink and multilink USFC. Computer simulation work of NAO investigates USFC link. The result is quite satisfactory for the automatic management of objects of such complexity.

Main requirements to the systems of automatic control of underwater complexes are specified. Main points of the synthesis of control systems by the method of inverse dynamics are given. The drawbacks of the method of inverse dynamics are defined, which consist in the limiting of the choice of the structure of a reference model and the necessity of bringing a mathematical model of the object of control to the view of a reference model. A mathematical model of an underwater complex is developed for the synthesis and study of the systems of its control that simulates a one-dimensional motion of an underwater vehicle under conditions of perturbing influence of a tether cable. Impossibility of the use of the method of inverse dynamics in the classic form for the synthesis of automatic control systems of underwater complexes is determined because their mathematical models contain elements that are set in arbitrary form. The method of inverse dynamics was improved by applying the principle of decomposition of a reference model, which boils down to its formation as a set of reference submodels based on the actual structure of an object. Decomposition of a reference model makes it possible to synthesize high–precision control systems of underwater complexes by the method of inverse dynamics and to set reference submodels of dynamics of phase coordinates of an object in the form of arbitrary functions of time. Automatic control system of a one-dimensional motion of an underwater complex was synthesized by the method of inverse dynamics using the principle of decomposition of a reference model. The author proposed three variants of a reference model of an automatic control system. The first variant makes it possible not to execute conversion of a mathematical model of the object to the view of a reference model. The second and the third variants are formed on the basis of the structure of a mathematical model of an object, presented in the form of Cauchy. This allows setting the dynamics of transition processes for each phase coordinate of the object in the form, accordingly, of differential equations of the first order and arbitrary functions of time. Computer simulation of an automatic control system revealed that the transitional process of eliminating an error of the controlled magnitude corresponds to the reference one. After eliminating the error, the controlled magnitude strictly follows the set one without delay.

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.

The synthesis of automatic control system (ACS) of industrial conditioner is examined within the framework of the single computer-integrated complex taking into account technological connections between a climatic equipment, that provides for that in space of the state from the present mathematical models of climatic equipment the complex dynamic model of industrial conditioner is got. In order to avoid the additional cooling and repeating of heating of air the modified method of management is realized on the mode for that as parameters of adjusting ACS of industrial complexes of artificial microclimate (ICAM) it is suggested to use temperature and moisture content of air. Such approach allows to divide influence between the contours of adjusting of temperature and humidity for the single material stream of air mixture. A synthesis of ACS for an industrial conditioner is conducted, where or relative humidity, or moisture content of air, is used in the contour of adjusting of humidity. Quality of synthesized control system studied on the channels of indignation at equal terms. Basic principles of synthesis modern automatic control system for industrial conditioner are considered for a concrete example, that differ from traditional on such points. Firstly, it is an analysis of dynamics of heat- and mass-transfer of equipment of conditioner with creation of complex models of ICAM as a single object of management in the coordinates of temperature and moisture content of air. Secondly, cross-coupling of contours of adjusting of temperature and humidity did differentiation due to using of temperature and moisture content of air as parameters of adjusting. Thirdly, modern algorithms used for synthesis of optimal ACS ICAM. It is possible to draw conclusion on researches of work, that the use of moisture content of air instead of relative humidity of air in the contour of stabilizing of humidity allows to delimit a cross-coupling between the contours of adjusting of temperature and humidity in two-dimensional ACS ICAM. If in two-dimensional ACS ICAM in the contour of adjusting of humidity used moisture content, the integral indexes of quality get better in 1.5 - 2 times, also diminishes shake and duration of transients. The offered principles can be used by specialists on automation for an analysis and tuning of parameters of control system by industrial conditioners

The technology for implementing a precise soil beating after precise soil levelling was proposed to improve the flatness of the paddy field and shorten the cycle time between the soil beating and levelling; in addition, a laser-controlled paddy field levelling-beater was designed according to the working principle. And the grade and tilt of the levelling scraper and beating mechanism are automatically controlled according to the levelling-beater vertical height and the tractor roll angle, respectively. The designed levelling-beater is capable of precise levelling and beating paddy fields at the same time with an adjustable beating depth. A paddy field test of the levelling-beater was conducted to compare the performance under both manual and automatic control modes, with the roll angles of the tractor and the levelling-beater measured using two attitude and heading reference systems (AHRSs), and the change in grade of the levelling-beater was measured using a global navigation satellite system (GNSS). The test results demonstrate that the operational quality of the levelling-beater is more stable when operating in automatic control mode than when operating in manual control mode. More specifically, the elevation of the levelling-beater varied ±4 cm around the mean elevation and roll angle varied within the range of ±0.5° when operating in automatic control mode. However, when operating in manual control mode, the elevation and roll angle were greater than ±11 cm and ±2.5°, respectively. The test results also demonstrate that the laser-controlled paddy field levelling-beater significantly improves the paddy field flatness, and enables it to operate at a stable depth to realise an even levelling and beating layer. More specifically, the maximum variation of elevation was reduced from 26.4 cm before the levelling and beating operation to 11.5 cm after the operation. In addition, the standard deviation of the elevation was reduced from 4.13 cm to 2.18 cm after the operation. The total number of flatness sampling points with the absolute difference of the desired elevation less than or equal to 3cm was more than 86%. The effective beating depth was 14.2 cm, compared with the set beating depth of 15cm, and the standard deviation of the beating depth was 2.46 cm. Keywords: laser control, levelling, beating, paddy field, flatness DOI: 10.25165/j.ijabe.20201301.4989 Citation: Zhou H, Hu L, Luo X W, Tang L M, Du P, Mao T, et al. Design and test of laser-controlled paddy field levelling-beater. Int J Agric & Biol Eng, 2020; 13(1): 57–65.