Nonlinear Identification with Constraints in Frequency Domain of Electric Direct Drive with Multi-Resonant Mechanical Part

Knowledge of a direct-drive model with a complex mechanical part is important in the synthesis of control algorithms and in the predictive maintenance of digital twins. The identification of two-mass drive systems with one low mechanical resonance frequency is often described in the literature. This paper presents an identification workflow of a multi-resonant mechanical part in direct drive with up to three high-frequency mechanical resonances. In many methods, the identification of a discrete time (DT) model is applied, and its results are transformed into a continuous-time (CT) representation. The transformation from a DT model to a CT model has limitations due to nonlinear mapping of discrete to continuous frequencies. This problem may be overcome by identification of CT models in the frequency domain. This requires usage of a discrete Fourier transform to obtain frequency response data as complex numbers. The main work presented in this paper is the appropriate fitting of a CT model of a direct-drive mechanical part to complex number datasets. Fitting to frequency response data is problematic due to the attraction of unexcited high frequency ranges, which lead to wrong identification results of multi-mass (high order) drive systems. Firstly, a CT fitting problem is a nonlinear optimization problem, and, secondly, complex numbers may be presented in several representations, which leads to changes in the formulation of the optimization problem. In this paper, several complex number representations are discussed, and their influence on the optimization process by simulation evaluation is presented. One of the best representations is then evaluated using a laboratory setup of direct drive with unknown parameters of three high mechanical resonance frequencies. The mechanical part of the examined direct drive is described by three mechanical resonances and antiresonances, which are characteristic of a four-mass drive system. The main finding is the addition of frequency boundaries in the identification procedure, which are the same as those in the frequency range of the excitation signal. Neither a linear least-square algorithm nor a nonlinear least-square algorithm is suitable for this approach. The usage of nonlinear least-square algorithm with constraints as a fitting algorithm allows one to solve the issue of modeling multi-mass direct-drive systems in the frequency domain. The second finding of this paper is a comparison of different cost functions evaluated to choose the best complex number representation for the identification of multi-mass direct-drive systems.

Calculation of Vineyard Hail Protection Device

The kinematic and force analysis of an invented new mechanical system used to protect vineyards and other fruit-bearing plants from hail, which often occurs due to climatic changes, is determined. The system contains levers that support anti hail net. The offered mechanical scheme of system is simple and can be used for all type of vineyards. Moreover, the mechanical part of the system can be controlled remotely by a cell phone. In order to determine the mechanical parameters of the system the calculations are given based on the use of the principle of possible displacements, based on what theoretically is determined the necessary volume of weight of load that leads in motion of the system.

Estudo comparativo entre transmissões automotivas automáticas e manuais

O mercado automobilístico vem intensificando a criação e a aplicação de novas tecnologias veiculares. Nesse sentindo, entre os elementos que sofreram notável evolução, destacam-se as transmissões automotivas, que são objetos fundamentais na dinâmica veicular, pois contribuem para o deslocamento do automóvel e, além disso, são ofertadas no mercado nas mais diversas variações. O objetivo deste trabalho foi elaborar uma análise técnica comparativa entre os principais modelos de transmissões presentes no mercado: automática e manual. Primeiramente, foi realizada uma comparação em relação à parte mecânica estudando os principais cálculos associados ao desempenho de modelos equipados com esses mecanismos e foi realizada uma análise econômica. Os resultados mostram um relacionamento de aspectos que englobam desempenho, manutenção e consumo entre esses componentes com bons resultados. The automobile market has been intensifying the creation and application of new vehicle technologies. In this sense, among the elements that have undergone notable evolution, automotive transmissions stand out, which are fundamental objects in vehicle dynamics, as they contribute to the displacement of the automobile and, in addition, are offered in the market in the most diverse variations. The objective of this work was to elaborate a comparative technical analysis between the main transmission models present in the market: automatic and manual. First, a comparison in relation to the mechanical part was carried out, studying the main calculations associated with the performance of models equipped with these mechanisms, and an economic analysis was carried out. The results show a relationship of aspects that encompass performance, maintenance and consumption between these components with good results.

Influence of stiffness of the mechanical part of the drive and cutting parameters on the shaping elastic deformation control

Introduction. One of the ways to improve the accuracy of manufacturing parts by cutting is related to the control of elastic deformations of the tool and the workpiece. This is particularly true for slender parts, whose stiffness law along the tool path is given. In this case, the control parameter, as a rule, is the return flow rate, which affects the cutting forces, whose change causes variations in elastic deformations. To provide the specified accuracy of the diameter, it is required to coordinate the controlled trajectory of the feed drive speed with the feed rate and a priori given law of change in the stiffness of the workpiece or the law of variation of the cutting process parameters. To do this, it is required to determine the law of converting the engine speed into the feed rate, and, ultimately, into elastic deformations. This law depends on the stiffness of the mechanical part of the feed drive and the changing parameters of the cutting process.Materials and Methods. The paper presents mathematical modeling and, on its basis, analysis of the conversion of the feed rate into cutting forces, taking into account the final stiffness value of the mechanical part of the drive and the evolutionary parameters of the cutting process. Results. It is shown that, starting from a certain critical value, the law of converting the feed rate into cutting forces becomes fundamentally dependent on the stiffness of the mechanical part of the drive. At the same time, there is an increase in time for setting a new force value when the feed rate varies, which affects the accuracy of providing forces that are consistent with the stiffness law of the part. The paper presents algorithms for calculating elastic deformations for a given stiffness law, as well as algorithms for calculating the trajectory of the feed rate at which the deformations remain constant. It is shown that the law of conversion is also affected by variations in the cutting parameters. Discussion and Conclusion. The frequency and time characteristics of the conversion are discussed. A conclusion is made about the accuracy of the diameter formed through cutting, depending on the stiffness of the mechanical part of the feed drive and on some parameters of the cutting process.

Electrical equivalent circuit for modelling permanent magnet synchronous motors

In permanent magnet synchronous motor (PMSM) models, only the stator part is given as an electrical circuit and mechanical equations are used for modelling the mechanical part of the machine. In this study, electrical equivalents of mechanical equations are also obtained and mechanical parameters of a PMSM are expressed as an electrical circuit element. In this way, an exact electrical equivalent circuit is proposed in which both the stator and the mechanical part can be modelled as an electrical circuit for the PMSMs dynamic model. Although PMSM model includes mechanical parameters and variables, the complete model is expressed only in electrical elements and variables. The proposed PMSM circuit was simulated for different load torques in the circuit simulation program. Simulation results show that the proposed circuit operates like a PMSM. Simulation results were verified by another method in the form of solution of the differential equations that constitute the mathematical model of PMSM. Due to the proposed circuit that enables the conversion of mechanical parameters into electrical parameters, PMSM can be modelled and simulated as an electrical circuit with completely electrical elements in a circuit simulation program.

TECHNOLOGICAL FEATURES OF MANUFACTURING COMPLEX PARTS OF THE MECHANICAL PART OF OPTICAL DEVICES AT MACHINING CENTERS

The article defines the concept of "technological features". Examples of technological features of modern manufacturing by cutting complex parts of the mechanical part of optical devices are considered and analyzed. The examples contain fragments of manufacturing parts only on CNC machines of the "machining center" type. This type of metal-cutting equipment is accepted as the main one in the conditions of automation of processing by cutting metal products. The necessity of systematization of the features of manufacturing products in optical and assembly technology is stated. Attention is drawn to the practical and theoretical significance of this work.

MAGNETIC LEVITATION AS ENERGY HARVESTER

Magnetic levitation as energy harvester has been widely studied since past few years. It can be used to implement a low-cost and maintenance-free energy harvester. For self-powering a broad range of technologies for long periods of time, levitation-based harvesting systems able to operate autonomously. In this paper, a theoretical study is presented of a harvester conguration that utilizes the motion of a levitated hard-magnetic element to generate electrical power. The levitation used minimizes the loss caused due to wear and tear of mechanical part thus increasing the life of the system.

Development and research of selectively invariant electromechanical systems with elastic kinematic units based on the separation of the harmonic disturbance model

Currently there is a big variety of structure solutions of the selective invariant electromechanical systems with different layout schemes of disturbance internal model for electric drives with robust kinematic units. However, methods of structural parametric synthesis for controllers with combined triggering model only were developed selective invariant systems with “robust” kinematic of mechanical part. Consequently, further improvement of the structure variety of systems for special effects of elastic kinematic units of mechanical part is of current interest. It can be performed by including the distributed model of harmonic disturbance into the synthesis process. Structural parametric synthesis is based on the methods of modal control theory, regulators reduction, selective invariant principals, velocity separation in local sub-systems, regulation by coordinates of state and by output, cascade and slaved coordinates regulation, splitting of disturbance model to separate elements in managing contours. Investigation was performed by specified computing experiments with synthesized electromechanical system models. Now, new structure solutions of selective invariant electromechanical systems with elastic mechanical elements are developed. They are created by using the additional separation principle for disturbance model into separate parts and moving them in to the contours of “fast” and “slow” sub-systems. Acquired models of synthesized systems were compared upon the complex of main quality indicators, the comparison was based on the performed computing experiments. The acquired results of complex performance of set requirements demonstrate main pros and cons for each variant of selective invariant electromechanical systems with elastic elements, determine areas of their preferred usage and allow the developers to simplify the solution of structure optimization based on selected schema of compromises.