Zyuzin Dmitry

Faculty: Electrical Engineering
Speciality: Electric Drive and Industrial Installation Automation

Theme of master's work:

Research of Anti-Sway in the Electromechanical Systems of the Cranes

Scientific adviser: Kotsegub P.H

Summary of research and developments

INTRODUCTION

• Currency
• The Purpose and Problems
• Scientific Novelty and Practical Value

MAIN PART

• Mathematical Description of Two-Mass Electromechanical System
• Mathematic descriptions of the cargo sway process
• Anti-Sway Methods

CONCLUSION

• The Received Results
• Planned Results

REFRENCES

INTRODUCTION

           Currency

       In the modern industry the big share among all hoisting-and-transport mechanisms is occupied with cranes to which various functions are assigned: raw materials transportation, finished goods moving, installation and equipment repair.

       One of the main features of cranes is that in most cases a cargo with movement gear is connected not rigidly but with the means of elastic bracings that is the main cause of the appearance of swaying in horizontal movement of the cargo. Cargo swaying appears during start-up and braking of movement gear and slewing gear of the crane. Swaying considerably increases work cycle time, causes fluctuations of the torque and uneven crane movement, increases valve recession of some units, and in some cases can lead to the danger of cargo and object collision. Also the cargo sway has special importance in crane automation and for cranes which carry out exact mounting operation. This sways don’t stop for a long time because of low air resistance and rope rigidity. That is why it is necessary to apply anti-sway measures.

           The Purpose and Problems

       The purpose of the work is to research different anti-sway methods in crane electromechanical systems. To get an assigned aim it is necessary to solve next problems:

• to design a mathematic model of the two-mass mechanical part of electromechanical system with elastic bracings;
• to get mathematical description of cargo swaying;
• to research different ways of sway damping;
• to compare different methods.

           Scientific Novelty and Practical Value

       There are not enough works which completely and thoroughly open all the questions connected with sway damping in systems with elastic bracings.

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MAIN PART

           Mathematical Description of Two-Mass Electromechanical System

       Design model of the most general two-mass mechanical part of the electromechanical system is shown in fig. 1. On this model all the values are reduced to the motor velocity and mean: J₁ and J₂ – inertia moment of the first (the motor rotor) and second (the suspended cargo) mass; w₁ and w₂ – their angular velocities; c₁₂ and b₁₂ – equivalent coefficient of rigidity and a viscous friction of an elastic link;M – the motor torque; M_c1 and M_c2 – drag torques of the first and second mass, which for simplification represent the torque of a dry friction.

Figure 1 – Design model of the two-mass electromechanical system

       The system of the equations of the two-mass mechanical part is

       According to the received equations it is possible to make block schematic diagram of mechanical part according to the received equations, which is shown in the fig. 2.

Figure 2 – Block schematic diagram of mechanical part

       On the block schematic diagram are depictured: M_в=b₁₂(w₁-w₂) – viscous friction torque, – elastic link torque.

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           Mathematic descriptions of the cargo sway process

       For the calculation of the cargo sway process it is comfortable to use a design model, which is in the fig. 3.

Figure 3 – Design model of the cargo sway process
(Animation: 52.8 кВ, 8 shots, 5 cycles, GIF Animator)

       In the point M the masses of rotary elements of the movement gear and translatory moving parts are concentrated (m₁). In the point K cargo mass m₂ is concentrated. The differential equations of cargo movement:

;              (2)

where F(t) – accelerating or decelerating influence, which is applied in point M and generally depends on time; S₀ – тcurrent distance from the trolley to reference point in the fixed coordinate system; S – amplitude of cargo sway in the moving coordinates.

       Transformation of the equation (2) leads to the equation:

;              (3)

       General solution of the equation (3) with zero initial condition and constant force F(t) during the acceleration or deceleration periods will be of the form:

;              (4)

       Maximum amplitude of cargo sway will be equal:

;              (5)

       The cargos sway frequency:

;              (6)

       The derivative from (4) gives the following result:

;              (7)

       From the formulas (4) and (7) follows that in a time interval:

;              (8)

a cargo deflection S and velocity v_K will be equal 0, where n=1, 2, 3... is the quantity of cargo sway. In the other way swaying remains and their amplitude depends on initial conditions.

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           Anti-Sway Methods

       There are different ways of sway damping and methods of their realization. The most simple and less effective of them are [12]:

• the limitation of average drive acceleration, which main disadvantage is increasing of transient process time of a drive, that in most cases reduces the performance of the plants;
• the experienced hoist man actions and presence of the slide torque control in a range not less than 2:1, however a disadvantage is start-up behavior with constant cargo deflection;
• the limitation of rate of dynamic torque rise, this method has the same disadvantages as the first one has.

       Among the most perspective and giving good results following method can be singled out:

       1) Those which are based on the determination of the sway period:

• Acceleration to a half of velocity (it is used in a crane card VW3 A3 510 for frequency convertors Altivar 71 by "Schneider Electric");
• control that is optimal at performance [3].

        2) Modal control [10].

       3) Those which are based on the application of the intellectual units, such as

• FUZZY-control [9];
• Neuron networks.

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CONCLUSION

           The Received Results

       In a course of researching in Simulink/Matlab according to the fig. 1 the model of asynchronous electrical drive with two-mass mechanical part was designed. The sway period and amplitude conforms to formulas (5) and (6).

       Following anti-sway methods was modeled:

       1. Control that is optimal at performance. The results of modeling are in fig. 5.

Figure 5 – Results of the modeling of the drive system without sway damping (a) and with optimal performance control (b)

       Fig. 5 illustrates that using this anti-sway method cargo sways stop to the end of acceleration (), in spite of the first cargo deflection rather bigger than in a system without sway damping.

       2) Half-velocity acceleration method.. РThe results of modeling are in fig. 6.

Figure 6 – Transient processes in the drive system with half-velocity acceleration method (a) and without sway damping (b)

       Fig. 6 illustrates that after acceleration cargo sway stops (). When using this method the first cargo deflection is not bigger than in a system without sway damping. However start-up is rather prolonged that when using optimal performance control.

           Planned Results

       In the course of further research it is planned to design and model anti-sway system with FUZZY-controller and with artificial neuron networks.

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REFRENCES

1. Синтез вентильних приводів постійного струму: Навч. посібник/ Коцегуб П.Х. – Київ, ІЗМН, 1997. – 122 с.
2. Толочко О.І. Аналіз та синтез електромеханічних систем зі спостерігачами стану : Навч. посібник для ВНЗ. – Донецьк: Норд-Прес, 2004. – 298 с.
3. Герасимяк Р.П., Лещёв В.А. Анализ и синтез крановых электромеханических систем. – Одесса, СМИЛ, 2008. – 192с
4. Герасимяк Р.П., Мельникова Л.В. Оптимальное управление крановым механизмом передвижения./ Автоматика. Автоматизация. Электротехнические комплексы и системы./ – 1999 – № 1. с. 87-94.
5. Герасимяк Р.П., Аит А.М., Рамарувахуака А.М. Синтез электромеханической системы подъёмных механизмов с подавлением упругих колебаний // Електромашинобудування та електроустаткування: Респ.міжвід.наук. - техн.зб. – 1996. – Вип.48. – с.30-37.
6. Мельникова Л.В., Тепляков А.Г. Реализация оптимального управления механизмом передвижения с использованием системы ТПН-АД. //Електромашинобудування та електрообладнання: Міжвід.наук.-техн.зб. – 2000. – Вип 54. – с.21-25.
7. А.Г. Тепляков Оптимальное управление крановым механизмом передвижения с использованием тиристорного преобразователя тока. //Електромашинобудування та електрообладнання: Міжвід.наук.-техн.зб. – 2000. – Вип 55. – с.21-25.
8. К.П. Здрозис Повышение качества электромеханических систем с регулируемым асинхронным электроприводом – Диссертация канд. техн. наук: 05.09.03 / Одесский национальный политехнический ун-т. – О., 2001. – 144 с.
9. Tae-Young Lee, Sang-Ryong Lee Anti-sway and Position 3D Control of the Nonlinear Crane System using Fuzzy Algorithm. //International Journal of the Korean Society of Precision Engineering Vol. 3, No. 1, January 2002/ - c.66-75.
10. Stefan Palis, Frank Palis, Mario Lehnert Anti-Sway System for Slewing Cranes. //22nd International Symposium on Automation and Robotics in Construction ISARC 2005 - September 11-14, 2005.
11. Mahmud Iwan Solihin, Wahyudi Sensorless Anti-swing Control for Automatic GantryCrane System: Model-based Approach. // International Journal of Applied Engineering Research Vol.2, No.1 (2007), pp. 147–161
12. Ключев В.И., Терехов В.М. Электропривод и автоматизация общепромышленных механизмов: Учебник для вузов. – М.: Энергия, 1980. – 360с.
13. Altivar 71. Crane card. User’s manual. – 2008. – 48c.