Simulation Analysis of Track Transporter based on Recurdyn

: China has always been an agricultural country. The hilly area covers a large area and the road condition is poor. At present, it is difficult for agricultural transporters on the market to operate efficiently in this area, so it is necessary to improve their adaptability to the hilly landform. Crawler transporter is a main type of machine widely used in agricultural transportation. Compared with wheeled transporter, crawler transporter has good adhesion performance and is not easy to slip. When driving on soft clay road, its ground pressure and road subsidence are smaller, so crawler transporter is more widely used.


Introduction
China has long been a country dominated by agriculture, but more than 43 percent of the country is hilly and mountainous, which is more than half of the arable area. Although hills and mountains are not suitable for cultivation of food crops, they are important land resources for cultivation of oil, tobacco, vegetables, melons and fruits, hemp plants and so on, playing a crucial role in China's food production [1] [2].
However, due to the congenital natural environment, although the hilly and mountainous areas of China have advantaged natural conditions, the land area is small, irregular shape, the surrounding terrain is uneven, the field path is narrow, the gradient is steep, and the road surface is tortuous and bumpy, which causes difficulties for the efficient operation of large-scale agricultural machinery. However, the walking chassis of small agricultural machinery is not stable enough to facilitate operation [3][4] [5]. As a result, it is difficult to transport and operate various agricultural products in hilly areas, and it is difficult for ordinary engineering vehicles to operate directly [6]. Therefore, it is a challenge to realize the smooth movement of the walking chassis under the complex landform. How to improve the adaptability of various engineering vehicles to the hilly landform has become an urgent problem to be solved. The chassis structure of agricultural tracked transporter is complex, so importing it directly into Recurdyn software for simulation will reduce the solving speed and affect the accuracy of simulation results. Therefore, it is necessary to simplify the chassis structure to improve the efficiency and accuracy of simulation calculation. The relative rotation between the two components is constrained and can be turned freely, but not translated

Fixed pair
The relative position and attitude between the two components are fixed

Translational pair
The relative translation between the two components is constrained and can be translated freely, but not rotated In order to ensure the accuracy of simulation results, corresponding constraints need to be added according to the actual situation after the completion of the three-dimensional model of the whole machine. These constraints include rotating pairs, fixed pairs and moving pairs. Among these constraints, the constraint of rotation pair involves the constraint of rotation, the constraint of fixed pair involves the constraint of some parts in the model, and the constraint of translation pair involves the constraint of some parts in the model. Table 1 and Table 2 provide specific definitions and 208 forms. Figure 2 shows the unilateral track model after constraint definition:

Multi-condition Simulation Analysis
In order to explore the influence of hilly terrain environment on transport vehicles, multi-condition coupling analysis was carried out with reference to Optimal Test Design [7]. The maximum longitudinal climb was taken as the evaluation index, and orthogonal experimental analysis was carried out with lateral slope, driving speed, different loads and different road surfaces as factors. Simulation factors and levels are shown in Table 3 below. According to the factors and levels in Table 3 above, the maximum vertical climb is taken as the index of the test, and the orthogonal table of 3 levels and 5 factors is also selected and treated by the pseudo-horizontal method. Table 4 below is the scheme and results of the orthogonal test.  1  2  3  1  50°5  1  3  2  3  42°6  1  3  3  2  44°7  2  1  1  3  38°8  2  1  3  1  50°9  2  2  2  2  44°1  0  2  2  3  3  39°1  1  2  3  1  2  42°1  2  2  3  2  1  46°1  3  3  1  2  3  36°1  4  3  1  3  2  41°1  5  3  2  1  2  44°1  6  3  2  2  1  50°1  7  3  3  1  1  46°1  8  3  3  3 3 38° In Table 4, a, b, c and d respectively represent lateral slope, different road surfaces, driving speeds and different loads. According to the above table, the maximum climbing slope is 52° and the minimum climbing slope is 36°. The primary, secondary and optimal combinations of range analysis factors are performed, as shown in Table 5. In Table 5, K 1j , K 2j and K 3j respectively represent the sum of maximum climbing slope of each factor at level 1, 2 and 3. K 1j , K 2j and K 3j correspond to the mean value of level 1, 2 and 3 data and respectively. R j is the range of each factor a, b, c and d, which can determine the influence degree of the influencing factors on the test index. According to Table 5-4 above, the factors affecting the maximum gradient are listed in the order of main and secondary: different load > lateral slope > different road surface > driving speed. Now, variance analysis is carried out to further understand the influence of each factor on the test indicators, as shown in Table 6 below.

Summary
Taking the longitudinal maximum climb slope as the test index, the simulation tests were carried out respectively with the transverse slope, road type, driving speed and different loads as the main factors. It is found that different loads and lateral slope have a greater impact on the longitudinal climb slope, while the road type and driving speed have a smaller impact. The order of influencing factors was: different load > lateral slope > different road surface > driving speed.

References
[1] Yang Zaihong. Current Situation, problems and countermeasures of agricultural mechanization in hilly and