Main Parameter Optimization And Dynamical Simulation Analysis Of Replaceable Triangular Track For Skidder

With the establishment of the Natural Forest Conservation Program (NFCP) in 1998, China has reduced deforestation year by year. Consequently, the frequency of utilization of some skidding machinery, such as J-50 and J-80, has been on a downward trend. As a result, animal skidding has been the main method of skidding in forest. At present, because of the maturity of large-scale southern plantation, increasing cost of labor force in forest region, and animal skidding’s high cost and low efficiency, it is necessary to develop a multifunctional skidder which is new, efficient and environmentally friendly.As an emerging technology, replaceable triangular track has been applied to many different fields. It has higher passing capacity than wheeled devices, especially for the complex road conditions in forest region. Therefore, applying this technology to the multifunctional skidder could efficiently improve its dynamical properties.The main research contents include:①Determination of principal parameters. A study on choice of multifunctional skidder’s main parameters was made according to the survey data, the theoretical analysis results of mechanical models and the work requirements of skidder. ②Establishment of the virtual prototype. Solidworks and RecurDyn were used for modeling of the multifunctional skidder, then the virtual prototype was built. ③Simulation analysis on the straight conditions. Simulation analysis was made on the straight conditions under different pre-tension, road conditions, loading and skidding.④ Simulation analysis on turning performance. Simulation analysis was made on the effects of different pre-tension,velocities, accelerations, road conditions, gradients, loading and skidding on turning performance of skidder. ⑤Simulation analysis on passing capacity. Simulation analysis was made on the passing capacity under different pre-tension and velocities, so that the max width and max height in the case of different working conditions could be determined.Research results showed that 19.2kN (40% of the vehicle weight) was the suitable pre-tension of skidder track on the straight conditions. The soft road had a larger adhesion coefficient and generated a bigger running resistance than the hard one, so that the skidder got a worse handling stability. However, the soft road provided a better brake effect for the skidder. When the skidder was loading, it was much more difficult to accelerate, and the skidder vibrated more heavily. The skidder was steady when it ran at a constant speed, and got a enhanced braking capacity when it decelerated. While the skidder was skidding, it vibrated heavily on the condition of acceleration or deceleration. Only when it ran under the uniform state, all dynamical indexes got small fluctuation range and the skidder worked more smoothly.When the virtual prototype of the multifunctional skidder was turning, the proper pre- tension of track was 19.2kN (40% of the vehicle weight) and the proper turning velocity was 14rad/s. Different acceleration (positive, zero or negtive) had little impact on the turning properties. Besides, the bigger the turning angle was, the more easily the skidder turned, and meanwhile the more heavily it vibrated. The skidder turning on a soft road had a worse stability, being easier to off-wheel or chain scission than on a hard road. But due to the larger adhesion coefficient and vibration absorption of a soft road, the skidder still ran steadily on it. The climbing slope no more than 25° was suitable for the multifunctional skidder. When the skidder was turning on a loading condition, its starting smoothness got worse and dynamic performance became deteriorated. When the skidder turned on the condition of skidding, the fluctuation ranges of all dynamical indexes were larger than on the no-load state. However, the largest fluctuation ranges were in a permitted range, so the skidder turned smoothly and safely.The proper pre-tension for the virtual multifunctional skidder to cross the ditch was 24kN (50% of the vehicle weight). Too low speed was not suitable for crossing the ditch. Increasing speed properly was benefit for crossing, but the higher the speed was, the higher the demands for track properties were. The ditch width should not exceed 900mm when the skidder was no-load,800mm when loading and 1100mm when skidding.When the multifunctional skidder virtual prototype was climbing the vertical wall, the max speed should not exceed 14rad/s, and the proper speed was 10rad/s. Under this speed, the suitable pre-tension was 19.2kN (40% of the vehicle weight). The height of vertical wall should not exceed 600mm when the skidder was no-load,450mm when loading and 550mm when skidding.