The subject matter of the article is the processes of virtual localization of near shape parts during adaptive machining. The aim is to develop an effective method for finding the starting location of a CAD model of a part with virtual localization inside a point cloud obtained by laser scanning of a workpiece. The task is to formalize the procedure for starting positioning of the part model as the first stage of the virtual localization process. The second stage for final localization proposed to use iterative algorithms with the objective function which is sensitive to the intersection of the surface parts and the workpiece. In solving the problem the starting position used tools available in today's CAD packages and 3D scanning tools. The methods used are the methods of matrix algebra, in particular, the methods for finding the main central moments of inertia of three-dimensional objects based on the tensor of inertia. The following results were obtained. When calculating the inertia tensor components is proposed to use three-dimensional scanning data of workpiece and geometrical data of part obtained from the CAD system. The result is an algorithm starting location of CAD model in the virtual localization, which in the case of blanks with oversize close to uniform can provide enough current location parts for adaptive machining tasks. It is shown that to minimize computational errors and to ensure satisfactory accuracy of localization proposed algorithm can require several iterations of the shift vector search model. Conclusions. The scientific novelty of the results obtained is as follows: in contrast to the previously used approaches, when solving the problem of virtual localization for the starting position, using the condition of coincidence of the centers of the weight of thin shells coinciding with the surfaces of the workpiece and the part, it was proposed to additionally ensure the alignment of the main central axes of inertia of these shells, which, in the case of near shape blanks, provides a positioning accuracy that may not require additional iterative procedures.
The subject of the research is mathematical models of a gas-dynamic non-stationary process of filling a vessel with a component of a gas mixture. The aim of the study is the scientific and experimental substantiation of the choice of a model of filling a vessel with a component of a gas mixture with a given accuracy. The objectives of the study are to conduct full-scale experiments on filling the vessel with gas for further verification of the gas mixture generation control system, as well as in the development of adequate mathematical models of gas-dynamic flow, the analysis of simulation results, and the use of verified results in the system of automated generation of a gas mixture of a given accuracy by assessing the mass of its components depending on the filling parameters. The tasks are solved by studying the results of numerical modeling of the process and full-scale experiments. The following results are obtained. A series of full-scale experiments on filling a vessel with high-frequency monitoring of the pressure and temperature of the gas being filled was carried out. Significant factors were analyzed. The use of SAS SST turbulence models was substantiated. Models of the gas-dynamic unsteady process of filling the vessel with a component of the gas mixture for various values of the mass flow rate had been built. All the simulations were carried out using the ANSYS CFX software package. The influence of considering a heat exchange with the vessel walls on the studied parameters of the mixture is determined, namely: pressure, gas temperature averaged over the volume, gas temperature in a control point, mass of the component of a gas mixture. It was found that the deviation of the calculated data when using a model with an adiabatic condition on the wall compared to a model with a constant temperature regime is: for pressure – no more than 5 %, for averaged temperature – 6 %, for the temperature at the monitor point – 9 %, for mass – 1.5 %. The discrepancy between the simulation results and the full-scale experiment does not exceed 12 % in pressure and temperature at the monitor point, as well as 4 % in the mass of the component. By the experimentally determined accuracy parameter of the gas mixture (the mass of the mixture component in particular), the numerical models had been corrected to provide the mass value error of no more than 0.5 %.
A promising direction in the production of high-pressure pipelines is the use of composite materials with special properties. Characteristics of composite products are set by reinforcement schemes and the use of various binders. The stability of the strength characteristics significantly depends on the stability of the process of laying reinforcing fibers. The development of automated technological systems of production, ensuring the stability of the process, is an urgent task. A method of fiberglass pipe bends manufacturing by the method of pre-impregnated tape winding on a folding mandrel. To implement this method the problem of developing technological equipment, equipment and methods of adjustment are solved. The proposed solution provides the formation of a branch from the inner surface. The kinematic scheme of the equipment realizes the rotation of the tape stacker around the axis of the cross-section of the mandrel and the longitudinal-angular displacement of the mandrel relative to the stacker, which provides the possibility of cylindrical and spiral stacking of the tape. The installation of tap winding, which is a three-axis CNC machine that implements the proposed scheme, is described. The rotation of the coils with tape around the mandrel is provided with a hollow rotary axis – stacker. Moving the mandrel relative to the stacker is provided by its installation on a movable platform. Following the proposed method of manufacturing bends, the outer surface of the collapsible mandrel ensures the formation of the inner surface of the branch, including the connecting-butt surfaces. Rules for the choice of the surface of the connector mandrel, ensuring its extraction from the manufactured branch is formulated. A method for programming winding operations has been developed. A method for determining the parameters of the control system of the CNC system is given, which specifies the structure of laying the tape and the wall thickness of the outlet. A procedure is described for setting up a tap manufacturing operation consisting in changing the relative position of the installation elements and the mandrel fixing devices. The use of traditional for CNC systems approaches to adjust the coordinate systems ensures the accuracy of the initial position is not worse than 0.1 mm.
The production of complicated profile parts for aerospace technology is carried out by processing along spatial paths. The nature of the movement of each axis of the equipment is dynamic and unsteady-state. Accuracy must be ensured not only in a steady-state but also in dynamic mode. The determination of dynamic characteristics of the executive bodies is an important and urgent task to optimize the control process. An experimental research method using capabilities of the CNC system, which was equipped with additional hardware and software, is proposed. This allows to register a large number of parameters that describe the state of the equipment, the solving of the task of trajectory interpolating, the formation of control actions, the actual movement of the executive bodies. The methods of conducting experimental studies with the setting of a stepwise change in speed and with a change in speed according to the harmonic law for an open-loop and closed-loop system using various components of the feedforward in the regulator are considered. The use of circular interpolation for the formation of a harmonic law of speed change is proposed. The results of the study of the dynamic of the transition process of an open system are shown. The frequency characteristics of the drive under study are obtained. Its bandwidth is determined. The study of the moving process when the axis velocity changes in harmonic law was performed within the passband. The possibility of determining the maximum permissible values of inertial loads by the nature of the change in actual acceleration is shown. The influence of the regulator feedforward composition on the accuracy of positioning of the servo drive and the accuracy of the contour processing at various frequencies of the control action is studied. For each feedforward method, the frequency ranges of the control action are determined, on which the specified processing accuracy is ensured. It was found that the technological frequency limitation by the accuracy of the reproduction of the path turned out to be significantly more stringent compared to the classical approach for determining the bandwidth.
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