| The ratio of load capacity to self-weight is an important index to measure the efficiency of the mechanism.It is a new research direction for modern excavators to improve functions of rapid excavation and mobile transportation through lightweighted structure design and driving mode.With the development of green circular economy and urbanization,small-sized excavators play an increasingly important role in the construction of urbanization due to their advantages of simple operation,flexible movement,and green and low-carbon.However,traditional hydraulic excavators fueled by diesel make use of hydraulic system to transfer the power,which will inevitably lead to a set of problems,such as insufficient combustion of fuel,substandard exhaust emission,etc.What's more,on one hand,the hydraulic system is easy to spill and is not suitable for working under cold climate and requires high maintenance cost.On the other hand,the manufacturing cost of hydraulic excavators is high with big noise at work,and the key components need to be imported.All of these deficiencies make the promotion of small hydraulic excavators difficult.In terms of the problems of the aforementioned hydraulic excavating mechanism,this paper takes excavators as the research object and puts forward a controllable excavating mechanism which has many advantages.To be specific,by using the servo motor as the driving source,it can effectively avoid the problem that the exhaust emission of diesel engine cannot meet the standard;by making use of the connecting rod as the driving link,it can effectively avoid using the complex hydraulic piping system of hydraulic excavators which is difficult to repair,and avoidable problems such as oil spilling,high and difficult assembly precision the and high maintenance cost.The main contents of this paper are as follows:(1)two schemes of threedegree-of-freedom of controllable excavating mechanism are proposed,and the controllable mechanism scheme based on the principle of low self-weight is selected with three servo motors as the driving mode.(2)Based on the closedloop vector method,this paper establishes the kinematic mathematical model of the mechanism and obtains the forward and inverse solutions of the pose and velocity of the mechanism.And the bucket structure is designed.The kinematics equation calculated by Matlab is compared with the simulation results obtained by Solidworks,which verifies the correctness of the kinematics model.The singularity analysis of excavators is carried out to obtain the singular position of controllable excavating mechanism.According to the existence theorem of implicit function,the workspace of controllable excavators is analyzed to acquire the workspace boundary conditions of controllable excavating mechanism.And with the implementation of Matlab programming,the workspace of controllable excavating mechanism is obtained.(3)On a basis of the dynamic and static method,the rigid body dynamics analysis of the mechanism is carried out when the agency is in working condition of mining,and the calculation equation of driving torque is obtained and the maximum of digging resistance of the controllable excavating mechanism is worked out in the light of empirical formula.In the meanwhile,this paper adopts the simulation analysis of dynamics of the new controllable excavating mechanism based on ADAMS and obtains the driving torque curves of each active member,which provides guidance for the selection of driving motor.(4)Given that the situation where excavators may suddenly dig hard objects.Therefore,on the basis of the simulation of ADAMS software,we utilize the LS-DYNA software to simulate the collision with barriers from different directions under the maximum kinetic energy when the excavator is unloaded,and analyze what influence would exert on the contact force and maximum dynamic stress of excavators from different colliding angels as well as the influence on the distribution of the mechanical stress under the action of external incentives. |
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