Design And Dynamic-static Performance Analysis Of A Type Of Controllable Palletizing Robot With Joint Clearance

The majority of palletizing robot on the market adopt series structure,which is known as flexible motion,large work space and low cost.But robot designed by that structure have a.serious defect—the drive motor must be installed at each joint.Not only will it increase the total mass,the Moment Inertial and the amplitude of vibration,but also it can accumulate error andreduce working accuracy.To cover these shortage,a new type of palletizing robot,which combines the concept of controllable mechanism and parallel mechanism,is proposed.By lowering the horizontal height of motor and cylinder,the arm load will decrease and dynamic characteristics will improve accordingly,which provides a new design idea to enhance the dynamic-static performance of palletizing robot.The contents of this paper include the following aspects:(1)Based on the method of joint closure,the optimum mechanism of the palletizing robot is selected from 40 kinematics chain diagrams.To improve the bearing capacity and working accuracy,a kind of improved palletizing robot is constructed.The loop module diagram is drew and the degree of freedom is calculated to verify the rationality of modeling.(2)Kinematics of this palletizing robot is analyzed.Firstly,the kinematic model of the mechanism is established by the D-H method,and the forward and inverse solution of position and posture is obtained.Secondly the velocity is solved by complex number vector method.Then the diagram of work space is plotted by MATLAB.Finally,the influence of the joint clearance is analyzed and an error compensation scheme,which is based on a modified PSO Technique,is proposed.(3)The joints that load changed frequently are considered as imperfect and the dynamics of the palletizing robot is analyzed.The dynamical models are established in two different patterns:For the continuous contact model,the rigid-body dynamics model is established by the Lagrangian equation;For the contact-separation-collision model with three states,the rigid-flexible coupled dynamics model is established by Newton Euler equation with Lagrangian multiplier.According to the working condition of the palletizing robot,the appropriate dynamics model is selected.(4)Dynamic characteristic of the palletizing robot is analyzed.The rigid-flexible coupled model is established by importing the 3D model into Adams software and the swing arms are replaced by flexible links,which is made in ANSYS software.By setting performance indexes of joint clearance,the influence of the clearance factor such as driving speed,clearance radius and load is analyzed quantitatively.(5)Strength and modal of the palletizing robot is analyzed.The 3D model is imported into ANSYS Workbench software and the mesh is divided.The effects of the joint clearance on the stress and deformation are considered,the comparative data of vibration modal is obtained,whether there have joint clearance or not.That provides a theoretical basis for clearance optimization and phototyping.