Research of oscillation in mechanisms with asynchronous drive

Наведено аналіз коливних явищ, які виникають при розгоні асинхронного привода механізму. При проведенні розрахунків використано двомасову динамічну модель. Зв’язок між зосередженими масами механізму – пружно-в’язкий. Показано, що нехтування у розрахунках електродинамічними перехідними процесами двигуна (використання статичної механічної характеристики) може призвести до резонансу та перевантаження елементів механізму динамічними зусиллями. Вказано способи забезпечення відсутності резонансу в механізмах, обладнаних асинхронним приводом та наведено основні напрямки подальших досліджень.The analysis of oscillatory phenomena that occur during acceleration of asynchronous drive mechanism is presented in the article. In the calculations two-mass dynamic model was used. Generalized coordinates of the mechanism and its drive are adopted to be angular. The constraint between localized mass of mechanism is elastic- viscous. The equation of motion of a dynamical system with help of the numerical methods has been solved. The maximum dynamic moment in the elastic-viscous constraint of mechanism was found. The influence of the values of the system parameters on the value of the dynamic forces in its elements is shown. In the research the dynamic and static mechanical characteristics of the engine are used. Dynamic characteristic is given in the form of equations in orthogonal coordinates fixed α and β. It is shown that the neglection of in the calculation of electrodynamic transients of engine (use of static mechanical characteristics) can lead to resonance and overload of elements of the mechanism of dynamic forces. The conditions of resonance in the mechanism, associated with the coincidence of the natural oscillation frequencies of the mechanism with one harmonic frequency electromagnetic torque have been investigated. It is shown that in the resonance appearance the width of the resonance zone, the attenuation coefficients of pulsating component of the electromagnetic torque and damping coefficients of the mechanical parts of the system are of great importance. Some considerations about the work of distributed parameter systems with an induction engine have been stated. The methods to ensure the absence of resonance in the mechanisms with asynchronous drive have been presented. Basic directions of further researches are listed. In order to establish the degree of danger of resonance for systems with distributed parameters it is necessary to carry out the numerical integration of differential equations of motion of the system and to find the maximum force in the elements of machines and mechanisms. Analytical dependences presented in the article are also shown in the graphical form

Optimization of mode of start-up of scraper conveyor

Представлено методику оптимізації режиму пуску скребкового конвеєра. За критерій оцінювання режиму руху конвеєра обрано середньоквадратичне відхилення швидкостей центра мас скребків і тягового органу в момент збігання з натяжного барабана. Отримано оптимальний режим руху системи та закон зміни рушійного моменту, який зводить до мінімуму величину динамічних навантажень.Optimization technique of mode of start-up of scraper conveyor is presented. For criterion of optimization of estimation of mode of movement of the conveyor the root-mean-square deviation of speed of center of weights of scrapers and traction body during the moment when run from tension drum is chosen. Optimum mode of movement of system and the law of change of the driving moment which reduces size of dynamic loadings to a minimum is received

Influence of threshing drum's disbalance in combine harvester on its vibration

Приведено дослідження неврівноваженості молотильного барабана зернозбирального комбайна. Виведено рівняння зміни коливань вертикального переміщення центру мас барабана та кута повороту барабана навколо центру мас, а також побудовано графіки цих коливань. Досліджено вплив зміни неврівноваженої маси, жорсткості опор та відстані між площиною неврівноваженої маси і площиною центру мас на амплітуду коливань вертикального переміщення центру мас та кута повороту.In this paper research of threshing drum’s disbalance in combine harvester is presented. Modern threshing drum of tangential type in combine harvester are made open. Central and extreme disks are mounted on the cylinder shaft. Bars or rasp bars are mounted on disks. This construction of threshing drum makes possible falling of grain, plant residues, powder and soil into the threshing drum. All this results in the imbalance of threshing drum and the emergence of oscillation. The oscillation is transmitted to the bearings and hull of combine harvester. These oscillations lead to reduced reliability rate of combine harvester, and also to reduce threshing quality of grain crops. In this paper oscillation equation of threshing drum system is solved. The free oscillation equations of threshing drum are shown. Equations of oscillation’ change vertical centroidal displacement and shaft rotation angle of threshing drum are derived. The oscillation’ graph of change vertical centroidal displacement and shaft rotation angle of threshing drum for different unbalanced mass, different stiffness of left and right carriage and for different placement unbalanced mass. It was considered that unbalanced mass can be placed on the left, center and right beater in bars of threshing drum. In this article we reviewed at an example, where an unbalanced mass on a single stick of bars in threshing drum of combine harvester. All of graphs are plottedfjr combine harvester KZS-9-1 «Slavutych» with characteristic І=13,64 kg∙m3, m=200 kg, ρ1=0,3 m; ω=85,7 rad/s. The unbalance mass is changed from 100 g to 500 g. The stiffness of left and right carriage is changed from 100000 Nm 145000 Nm. The impact of change of input parameters for oscillatory amplitude is researched. It was found that the stiffness of left and right carriage reduce oscillations of vertical centroidal displacement and shaft rotation angle of threshing drum in combine harvester. Increase of an unbalanced mass or characteristic a1 increases the forced oscillations of vertical centroidal displacement and shaft rotation angle of threshing drum in combine harvester

Ematical model of the bucket elevator's movement dynamics

Dynamic stresses, which arise in drive and traction element during operation of the conveyor have been investigated on the basis of the developed mathematical model. Calculation has been conducted with regard to its elastic and dissipative properties. The analysis of the obtained results has been carried out, with and without taking into consideration dissipative properties of the conveyor's element

The conveyor start-up mode optimization by a dynamic criterion tacking into consideration resistance forces

The way of reducing oscillations of the belt bucket elevators elements, during the transients, has been resulted by optimizing the start-up mode of the drive mechanism for the kinematic criteria. On calculation the resistance forces at scooping the material have also been taken into consideration

Optimization of regime of acceleration of one-mass dynamic system with integral limitations

In the given research the solution of problem of optimisation of regime of acceleration of one-mass dynamic system is resulted. Optimisation is carried out by means of variational calculus methods. For the account of limitations superimposed on regime of driving of system the Lagrangian multiplier method is used. The analysis of agency of magnitude of factor of Lagrange on parametres of driving of system is carried out

Synthesis of quasi-optimal motion crane’s control in the form of feedback

The solution of the problem of optimal crane’s control is proposed in this article. The crane’s model is adopted as two-mass. The synthesized quasi-optimal control allows one to eliminate vibrations during braking load of the crane. Control is a function of phase coordinates of dynamic system ”truck-load“ and it’s limited in size. One may use for the solution of the problem the method of dynamic programming. The results are illustrated with the help of graphics which are bold on the phase planes