| Logging operation is the primary stage of timber production. The quality of logging operation has a direct impact on the ecological and socio-economical benefits of timber production. Skidding operation is the process of the largest labor consumption of logging operation and the most serious destruction of the environment, so the skidding operation is one of the main processes of timber production. With more and more people focusing on the forest ecological benefits and the decline of timber production of state-owned forestry enterprises, the traditional large-scaled skidding tractors, such as J-50and J-80, are not suitable for current forest working conditions because of the scattered operation sites, steep slope, sparse trees, and the low of the skidding volume per hectare and standing timber volume per tree. At the same time, the contradiction between animal skidding and actual production in forest region is getting more serious. Therefore, it is urgent for developing flexible and environmental multifunctional machinery which is more suitable for forest production.The dissertation focuses on the development of an ecological multifunctional skidder with higher efficiency and lower environmental effects. The new skidder has multiple functions including winching, loading and unloading, obstacle clearance and road preparation. The developed skidder also has some other characteristics such as small size, flexible turning and good climbing ability. Additionally, the new skidder could drive within the forests without damaging young trees and construction of skidding roads. It also has less soil damages and good ecological benefits. It could improve productivity, reduce production cost, and has better economic benefits. As a multifunction machine, the new skidder could be used for site clearance and preparation, and silviculture during in non-skidding operation period.First, the dissertation introduces the development of skidding machineries and summaries the existing of problems of the traditional skidding machines. The key parameters of multifunctional wheeled skidder have been classified and the selection principles for key parameters of the new skidder are determined. Based on the forest statistics data of forest industries in Heilongjiang and Jilin provinces, as well as combined with the actual investigation in the northeast forest region, a mathematic model for the key parameters optimization design is established by using multiobjective optimization method. The key parameters are optimized and determined, and the corresponding technical indices and design scheme are formulated. Secondly, based on the selected key parameters, the prototype’s type and structure is determined and refitted, respectively. The multifunctional operating devices including the log grapple, winches, and the board are designed and assembled. Multi-body dynamics simulation software (ADAMS) is used for loading and skidding simulations. The critical angle of tipping is determined for loading and skidding operations. The alarm device for preventing machine tipping is then designed and programmed. In the analysis of dynamics process, it is noticed that the skidding device may reduce the possibility of rollover during skidding if the damping and knuckle-joint are added. Site experiments and testing including skidding, loading, and obstacle clearance are conducted in Daxin forest farm, Linjiang Forest Bureau, Jilin Forest Industry Group. Operating costs of the multifunction skidding machine are estimated and the effects of skidding operation on soil compaction, soil respiration, soil physical and chemical properties as well as the residual tree damage are analyzed. Finally, all of the measured indicators are analyzed and compared with the previous small tracked skidder, small wheeled skidder and the traditional J-50skidder. Recommendations and suggestions are proposed based on the problems appeared in the tests.The following results are obtained in this study:(1) The basic data for selecting the key parameters are obtained through field investigation and then the key parameters for the multifunction wheeled skidder are calculated based on the theoretical model. A mathematic model for the key parameters optimization design is established by using multiobjective optimization method. The selected key parameters are optimized and the best combination of key parameters for the multifunction wheeled skidder is determined.(2) The structural parameters and performance parameters are determined for the log grapple, winch and the loading board. The structure design and strength check are completed for the log grapple, winch and the loading board. The hydraulic system is improved correspondingly.(3) Multibody system dynamics simulation software ADAMS is used for the simulation of operating stability during loading and skidding of the multifunction wheeled skidder. The dangerous angle for forward-tipping during loading is calculated as21°and the dangerous angle for side-tipping during skidding is19.5°. The hardware design and programming are completed for the tipping alarm device.(4) Production tests are conducted with the multifunction wheeled skidder and the skidding and loading efficiency and productivity are analyzed quantitatively. The average skidding efficiency and loading efficiency were7m3·h-1and16.45m3·h-1. respectively, while the skidding productivity and loading productivity were29.62m3and56.2m3per machine-team. Results showed that multifunction skidder developed in this study fits the complex timber production conditions in northeast forest areas with higher skidding and loading productivity and less impacts on soil physical and chemical properties and soil respirations as well as less residual tree damages. The machine could meet the needs of operational requirements in forest area and be able to better protect the forest environment. (5) Comparisons of skidding operations among the multifunction wheeled skidder and small wheeled and tracked skidders, as well as the J-50skidder are conducted. Results showed that the skidding efficiency decreased as increase of the skidding distance for the first three types of skidders. As increase of the skidding volume per turn, the skidding efficiency of the multifunction wheeled skidder increases accordingly while no obvious changes of skidding efficiency noticed for both small wheeled and tracked skidders. In comparison with the J-50skidder, the multifunction wheeled skidder fits the site and forests conditions of northeast forest areas better with less residual tree damages. The latter can effectively protect the forest ecological environment.(6) Further improvements and simulations are done based on the deficiencies of the skidding device, and the results are compared with the ones from the original conditions. The rigid connection between skidding device and the base machine is modified as knuckle-joint. The torque comparison charts shows that the increases of the torque getting slow down after modification. The risk for slippage is reduced by18.5%, and the risk for side-tipping is reduced by19.2%. |
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