Performance analysis of loader working device base

Performance analysis of loader working device based on ADAMS

Abstract: the kinematics and dynamics of wheel loader working device are studied by using modern CAE software UG and Adams. The function curve of the load and relative position relationship of each component in the operation process of the working device is obtained and analyzed. The analysis results provide a basis for the design of the working device and have strong applicability

key words: loader; Working device; UG； ADAMS； Job simulation

introduction

the working device of loader is a spatial multi bar mechanism with hydraulic cylinder, which mainly completes the loading and unloading work. The working device is one of the key parts of the loader, and its design level directly affects the working performance, efficiency and performance index of the loader. Therefore, the analysis and research of working device is of great significance

msc.adams is the most widely used simulation software at present. It uses interactive graphics environment and parts library, constraint library and force library to create a fully parameterized geometric model of the mechanical system. Its solver adopts the Lagrange equation method in the dynamics theory of multi rigid body system to establish the system dynamics equation, carry out statics, kinematics and dynamics analysis, output displacement, velocity Acceleration and reaction curve. The simulation of msc.adams software can be used to predict the performance, motion range, collision detection, peak load of mechanical system and calculate the input load of finite element

1 virtual prototype motion simulation of loader working device

1.1 creation of three-dimensional geometric model. Although msc.adams/view has powerful functions, the modeling function of Liangping plastic ecological industry to actively integrate into the city's "6+1" pillar industry is relatively weak, so it is difficult to use it to create parts with complex characteristics, and it is unrealistic to create such a complex mechanism as the working device of loaders. Therefore, we use UG to create a model, and then send the model to msc.adams for analysis

1.2 import of 3D geometric model. The second part of this paper is the environmental treatment of garbage. The solid data model of loader working device in UG environment is exported in the Parasolid format that can be better recognized by Adams. The guiding steps are as follows: ① select the Parasolid (*.xmt_txt.*xmt bin) file type in the file import dialog box of Adams, and input the path and part name of the file. Right click in the part name box and select Create, and modify the part name item in the pop-up dialog box. Click 0k continuously to import the part; ② After importing the file, double-click the part to pop up the "modify rigid body" dialog box, select geometry and material type in the deftne mass by column, select.Materia1.steel in the material type text box, and click apply to complete the automatic calculation of mass, moment of inertia, and center of mass; ③ Repeat steps ① and ② to complete the import of various parts, and the imported parts maintain the original assembly relationship. (as shown in Figure 1)

1.3 addition of constraints and their motion drives

1.3.1 constraint addition. After the above processing, although it looks like a virtual prototype of a loader, there are no constraints between its components. In order to carry out motion simulation, we must add constraints and motion generators between various mechanisms. Each hinge point of the working device is defined as a revolving pair, and the sliding pair is defined between the piston rod of the oil cylinder and the cylinder barrel

1.3.2 restraint and load analysis of loader working device. The typical working process of loader working device includes insertion, shovel loading, heavy-duty transportation, unloading and no-load transportation. Transportation conditions are not considered in this paper. The working resistance of the working device in the digging operation is mainly: the insertion force when the bucket is inserted into the pile; Shovel lifting force when lifting boom; The resistance moment of the rotating bucket when turning up the rotating bucket. The working condition considered in this paper is that the bucket is inserted and matched with the overturning movement of the bucket, so the resistance is the insertion force and the resistance torque of the bucket. The resistance torque of the rotary bucket is converted into the scooping resistance, so the loads on the working device here include the insertion resistance NN, the scooping resistance FSH, the material gravity and its own gravity. The maximum insertion resistance fin is limited by the maximum traction force, which can be calculated in the future by the following formula:

the maximum scooping resistance FSH can be obtained by converting the maximum bucket resistance torque during scooping. The maximum bucket resistance torque occurs at the moment when the bucket starts to rotate, and its value can be calculated by the following formula: it is important to design the fixture according to the shape and material of the sample (as shown in Figure 2)

Figure 2

A. determination of the static resistance torque during bucket rotation. At the beginning of tipping, the resistance moment M to be overcome is the maximum static resistance moment (or the initial static resistance moment of the bucket), which has the following functional relationship with the insertion resistance PC:

lcmax - the maximum depth of the bucket inserted into the pile

x - the horizontal distance between the bucket rotation center 0 and the bucket edge

y - the vertical distance between the bucket rotation center 0 and the ground

B. the total resistance moment when turning the bucket. When overturning the bucket, in addition to the initial static resistance torque of the material, it is also subjected to the resistance torque of the bucket self weight, so the total resistance torque during the initial bucket rotation is:

mmax - total resistance torque

mc - initial bucket static resistance torque

gb - bucket self weight

lb - Horizontal distance from the bucket center of gravity to the bucket rotation center

finally, the bucket resistance torque is converted into the shovel resistance acting on the bucket tip

fsh = mmax/x

1.4 control of simulation process. The typical working process of the loader working device can be divided into the following four stages: 1.4.1 the rotary bucket cylinder is extended, the boom cylinder is locked, and the bucket is retracted to realize the shovel loading of materials; 1.4.2 the rotary bucket cylinder is locked, the boom cylinder is extended, and the boom is lifted to realize the lifting of materials; 1. The rotary bucket cylinder shrinks, the boom cylinder locks, and the bucket overturns to realize the unloading of materials; 1.4.4 the rotary bucket cylinder is locked, the boom cylinder is retracted, the boom is lowered, the bucket is automatically leveled, and the next digging state is automatically entered. Adams solver command flow can be used to control the dynamic simulation process of loader working device. Corresponding to the four stages of the working process, the control of the simulation process is also divided into four stages. At each stage of the simulation process, the action of the model is limited by the sensors added to the components to ensure that the action is accurate

2 data analysis

2.1 operation load analysis. During the operation of the loader, the insertion and shovel loading of the bucket are carried out in sequence (regardless of the combined shovel loading condition), the insertion resistance and shovel resistance reach the maximum value in turn, the material gravity reaches the maximum value at the beginning of shovel loading, and the self weight of each component does not change. During the simulation, the step function provided by the system is used to represent the change of fin, fan and FG with time. Simulate a working cycle, and get the stress conditions of boom cylinder and bucket cylinder in the operation process, as shown in Figure 3. The load reaches the maximum at the same time when starting digging, and increases with the increase of bucket insertion depth. Then the boom cylinder is lifted with heavy load, and the stress increases with the decrease of signal force ratio, and finally decreases to the minimum with unloading

2.2 transmission analysis. Figure 4 shows the change of the included angle between the transmission parts in the whole operation process. It can be seen that all transmission angles meet the requirements of more than 10 degrees, and the minimum transmission angle occurs at the end of unloading, effectively ensuring the smooth operation of all components during operation

figure 4

2.3 translational analysis. In the process of shoveling and loading materials from bottom to top by the working device of the loader, in order to prevent materials from being scattered from the empty bucket, the bucket is required to move approximately horizontally, and the change of bucket inclination in the whole process is required not to be greater than 15 degrees. During the simulation operation, measure the bucket position angle and let the boom cylinder lift at a uniform speed, and get the change curve as shown in Figure 5. It can be seen from the figure that the maximum bucket inclination difference is L4., The translational performance is within the normal range

figure 5

2.4 automatic radioactive level analysis. Automatic bucket leveling refers to that after the bucket is unloaded at a certain position, the rotary bucket cylinder is locked and does not make the bucket retraction stroke. When the boom lifting cylinder is lowered to the ground position, the automatic bucket leveling is realized by the movement of the connecting rod mechanism itself. During the simulation, when the bucket is unloaded and returns to the shovel loading state, keep the length of the bucket cylinder unchanged, and use the sensor in msc.adams to measure the change of the angle between the bucket bottom and the horizontal plane to obtain the automatic leveling performance of the mechanism. It can be seen from Figure 6 that the included angle between the bucket bottom and the ground after the bucket falls is about 8 degrees, which is qualified

3 conclusion

3.1 using UG to establish the working device model of loader accurately and effectively solves the problem of weak modeling ability of simulation software

3.2 using the international general software ADAMS to simulate the operation of the loader working device has high reliability. Through the analysis of various operation performance curves obtained from the simulation, the design of the working device is reasonable, and the transmission, translation and automatic leveling of the system are within the scope of the work requirements. (end)