Kinematic And Dynamic Analysis For Hole-wall Mounted Excavator In Piling Construction

Hong Kong,Chongqing and other cities have few land and many hills,and the common foundation cannot meet the requirements of high-rise buildings,so the hand-dug caisson construction and bored pile construction are very popular.The practice of digging caissons by hand has been banned by the Hong Kong Government due to the safety problem.What’s more,the large mechanical equipment is difficult to operate on steep slopes.So this paper designs a hole-wall mounted excavator to complete the excavation operation in foundation construction.The digging manipulator is an important part of the hole-wall mounted excavator.Its kinematics and dynamics performance directly affect the performance of the whole machine,especially the excavator works in the limited space of the shaft.Therefore,this paper carries on the kinematics and dynamics simulation and analysis of the manipulator.The details are as follows:Firstly,according to the design concept and the traditional excavator model,the hole-wall mounted excavator is designed and established.This paper analyzes the working process of excavator and puts forward three working schemes based on the different working time of the arm.The kinematics model of the excavator is established.The mapping relationship between the actuator space and the joint space,and the position coordinates of each hinge point are obtained.Then the optimal operation scheme is determined.The kinematic constraint model and equations of the excavator are established.Taking the shaft diameter of 2m as an example,the length selection ranges of boom,arm and bucket are analyzed,which provides a theoretical basis for the design of excavatorsSecondly,the forward and inverse kinematics of the digging manipulator is analyzed based on the D-H method.The mapping relationship between joint space and position and orientation space is obtained.The joint angles are obtained by given trajectory path points.In order to improve its stability,3-3-3-3-3 and 3-3-5-3-3 piecewise polynomial interpolation methods and 5-degree NURBS programming method are used to plan the trajectory in joint space.The simulation results show that 3-3-3-3-3 piecewise polynomial interpolation method and 5-degree NURBS programming method can get smoother curves and better kinematic characteristics.Finally,the dynamic model of the digging manipulator is established based on the Lagrange method.The digging resistance is estimated.Through the dynamic simulation,the force curves of each hinge point are obtained,and the overall force change is analyzed,which provides the basis for the structural improvement.