Research On Trajectory Planning Algorithm Of Automatic Excavator

Excavators are machine which play a significant role in the field of construction and have been widely applied in various mechanized construction and disaster scene. The independent excavating is an indispensable assistant in many working conditions, where humans are difficult to enter directly, such as space explorations, underwater operations, etc. Those issues also prompt excavators to develop intelligently and automatically. Trajectory planning is the foundation of automatic excavating, but excavator trajectory planning is complicated compared to general industrial robots due to the complexity of work conditions and particularity of excavator performances. The reasons are shown as follows:(1) For the trajectory planning of automatic excavator, in addition to satisfying the constraints of trajectory planning in general industrial robots, the excavating volume of the trajectory planning should be equal to the volume of the full bucket.(2) Obstacles in the soil are unpredictable in excavating process. Because of that, excavators will inevitably collide with the large obstacles in inhomogeneous media contain large obstacles. If this problem cannot be solved, mechanical life of excavators will reduce and serious consequences will occur.(3) Costs of testing on real machine are excessive and time-consuming.According to these factors, problems in designing trajectory plan of excavators become complex. Several constraint conditions need to be considered and the requirements of trajectory planning for excavators become rigorous. During excavation, based on the characteristics of excavators, selecting high quality trajectory planning method can effectively guarantee the efficiency of excavators and a smooth-efficient completion of excavating operations in different soil conditions.Several algorithms of trajectory planning are raised according to the problems above:(1) The excavating amount after trajectory planning should be equated to the volume of full excavating. In order to achieve the goal,this paper proposes a trajectory planning method based on five polynomials and integration method.(2) For the case of encountering obstacles during excavating in inhomogeneous media, using two-level planning approach of preimage planning and the lower forward searching to complete smooth-efficient excavating. In excavating, excavators can make adaptive motions along them when encountered obstacles.JGM915 excavator which made by Fujian Jingong Machinery Co.,Ltd. is chosen for this research. Using simulation software of Matlab, kinematical and dynamical models of the excavator have been built, the equations for the relationship between hydraulic cylinder length and joint ankles and the model of trajectory planning algorithm have been derived. Simulation software of AMESim has been used simultaneously for modeling mechanism and hydraulic system of the excavator. This modeling process achieve the joint simulation of AMESim and Matlab/Simulink.Experiments show that the proposed design can effectively verify the feasibility of the proposed method, it is possible to provide guidance for the actual excavation operations, while reducing development costs, it can be used in actual production test.