Kinetic Analysis of Four-link Gantry Crane Hoisting System

This paper establishes a flexible dynamics model of MQ2533 portal crane boom system. In the premise of ignoring control system, this paper analysis the mechanical dynamics of boom hoisting system. Simulation results show that: Dynamics response of the hoisting boom system have great fluctuation when excluding the control effects, this paper provide a theoretical basis for crane hoisting system to optimize control strategies, which committed to improve their performance and ensure safety, reliability and economy.


Introduction
Gantry crane is a large construction machinery, mainly used for port, berth, open stockyards and outfitting site.
It has good transport, big depth of spreader decentralization, better adapt to the temporary work and so on.we should full considerate its strength, rigidity and safety when design, but also to reduce the supplies and cost savings.Boom system is an actuator of portal crane, it is the design basis of electrical systems and other subsidiary organs.In order to simplify the calculation under the normal circumstances, we consider the mechanical components as rigid body [1] , But when we need a high precision calculation or study the stress magnitude, distribution and deformation within the body, you need to regard it as a flexible member.Precise kinetic analysis can make sure the gantry crane safety and performance, minimize its weight reduce noise and prevent the shock loads.Thus, kinetic analysis of four-link gantry crane hoisting system is particularly necessary [2][3] .
ADAMS has unparalleled advantages in dynamics analysis of rigid body than the other software, but very weak in flexible mesh unit and other processing functions.Flex module provides bi-directional data exchange interface with other finite element software(such as ANSYS, NASTRAN etc).We can import the modal neutral file(*.mnf) of other finite element software into ADAMS through interface [4] .
The main component of MQ2533 portal crane boom system comprises of nose, large rod, small rod, girder and etc.In order to understand its mechanical properties of displacement response of key nodes, stress, deflection, vibration frequency, we need to treat it as a flexible body; For the pulley, reel, small rod, balance beam and hoist and other ancillary components, we only need to know their motion parameters such as size, quality and moment inertia, thus regard them as rigid bodies [5][6] .MQ2533 portal crane is shown in Figure 1.

Parameters Calculation
Table 1 lists the device types of power and drive system of MQ2533 gantry crane [7] .Then driving torque of drum to wire rope is 80K times of the single motor(K is equal to 0.9, which is the total efficiency of motor to drum [8] ).
Nameplate data of the motor shows that ratio of 1.9e4

Simulation Results
We set parameters as follws in ADAMS: starting torque of equivalent drum is 1.8 times of the rated torque, which is equal to 203760N.m, then we can calculate the driving torque of equivalent drum acording to the equivalent above, and the terminal simulation time is 5s [9] .This paper analysis the mechanical dynamics of MQ2533 portal crane hoisting system ignoring the role of system control.Simulation results show that: Dynamics response of boom hoisting system has a great fluctuatation when excluding the effect of control system.
Next, we will be able to optimize the hoisting system of portal crane considering the frequency vector control mode and improve its control strategy and performance, which can ensure its safety, reliability and economy.

Figure 2 .
Figure 2. Rigid and flexible coupling model of boom system starting torque and rated torque 1700N/m is 0 1.8 O , ratio of the biggest torque and rated torque is 3 O , The diving torque equation are as follows: system parameters are shown in Table2:

Figure3Figure 3 .
Figure3 to Figure8 show the front and rear displacement responses and stress changes of the elephant nose girder, load

Figure 4 .
Figure 4.The rear displacement response Seen from Fig.3, the front displacement of girder gradually decreases to -0.055m from static equilibrium position within the first 1.5 seconds, For the 3.5 seconds behind, the displacement changes in vicinity of -0.0466m,The biggest amplitude is -0.03m, and relative rate of change is 35.6%, which explains a large fluctuation.

Fig. 4 Figure 5 .Figure 6 .Figure 8 . 7 andFigure 9 .Figure 10 .
Fig.4shows the rear displacement of girder fluctuation both sides of the equilibrium position which is equal to -0.01m, and the biggest displacement exceed the static equilibrium position before lifting.Comparate Fig.3and Fig.4after lifting, we can see the front equilibrium value is 5.5 times the rear one, so the front stiffness of girder is worse than the rear.

Fig. 10 4 Summary
Fig.10 demonstrate that rope force increase to 74200N within the first 1.5s, and it has a large fluctuation at the equilibrium position which is equal to 65756N, the biggest change is 26656N after 1.5s, accounting for 59.5% of the average one.

Table 1 .
Device types of power and system SZ 4Seen from Tab.1 above, driving motor and transmission system both have two sets.motor is variable for frequencies and reducer magnification is 40,