Positioning Error Compensation for Industrial Robots Based on Stiffness Modelling

Insufficient stiffness of industrial robots is a significant factor which affects its positioning accuracy. To improve the positioning accuracy, a novel positioning error compensation method based on the stiffness modelling is proposed in this paper. First, the positioning errors considering the end load and gravity of industrial robots due to stiffness are analyzed. Based on the results of analysis, it is found that the positioning errors can be described by two kinds of deformation errors at joints: the axial deformation error and the radial deformation error. Then, the axial deformation error is modelled by the differential relationship of kinematics equations. The model of radial deformation error is deduced through the recurrence method and rotation transformation between joints. Finally, these two models are transformed into a Cartesian coordinate system, and a positioning error compensation method based on these two models is presented. Simulations based on the finite element analysis are implemented to verify the positioning error compensation method. The results show that the suggested method can efficiently predict the positioning error according to the gravity and loads, so that the positioning accuracy of industrial robots can be improved with the proposed method.

Hybrid Position/Force Control for Dual-Machine Drilling and Riveting System

The deformation of riveting machine caused by riveting force during rivet formed makes the riveting tool out of positioning, which leads to gapping underneath the rivet manufactured head and insufficient rivet drive head. This paper proposes a hybrid position/force riveting control method for the dual-machine drilling and riveting system to eliminate the negative effects of machine deformation. The cooperative work of two-side machine tool is realized by a hybrid position/force control strategy, which compensates for the force-induced deformation error without an accurate stiffness model of the riveting system. The position of pressing foot relative to the machine which represents the deformation of skin-side machine is obtained for the compensation to the displacement of skin-side actuator. Simultaneously, the advanced force control is adopted for the stringer-side actuator. The dynamics model of the stringer-side actuator in consideration of the machine deformation is established and identified. The disturbance observer (DOB) and feedforward controller are introduced as the model-based control algorithm to achieve the high-performance force control. Also, contrast experiments are conducted to validate the effectiveness of the proposed riveting control method. The results show that the rivet manufactured head can be seated in the countersink during the forming process and the gapping under the head is eliminated. The driven head height tolerance of ±0.1 mm is achieved by accurate force control.

Research on influence of welding root node coupling on welding deformation of large mining dump truck frame

Taking the frame of large-scale mining dump truck as the research object, it established the model of coupling or not of T-joint welding root by the finite element analysis, and analyzed the deformation of coupling or not of T-joint welding root. The deformation trend of the two cases is the same, which verifies the correctness of the prediction results of deformation. The results show that the maximum deformation occurs at the arc starting welding of the vertical plate, and the error between the simulation results and the test results is small. At the same time, the deformation error of gantry frame and hinge-hole at the key position can meet the production requirements, which is of great significance to the field production.

Deformation Exploration in Mass Spring Model using Euler and Verlet Integration Methods

The paper assigns the firm technique that has been designed for the mesh based simulation by using the concept of mass spring model. The general mass spring model has been utilized in a lot of applications for instance, fashion designing, merging virtual booth and in the basics of cloth simulations, consecutively in order to develop effectual surgical training through virtual environments. Though, virtual simulators necessitate meeting both requirements that are, dynamic to be real time and high realistic. While dissimilar forces have applied on the particles they generate several differential equations. In order to, solve these equations, different kinds of integration methods have been used to get the best results. Here in this paper, it shows the procedure of generating a mesh based simulation using euler and verlet integrations method. Verlet method executes vigorous compared to Euler integration method on the basis of deformation error.

Aero-engine blade profile reconstruction based on adaptive step size bat algorithm and visualization of machining error

High-precision profile reconstruction is a key issue in the profile detection and visualization of aero-engine blades. A method based on adaptive step size bat algorithm (ASSBA) for blade profile reconstruction and an adaptive mesh model for visualization analysis of the key machining errors are proposed. Firstly, the original bat algorithm (BA) is improved to introduce the global stage and local search stage. Then, combined with the node layer characteristics of the blade measurement data, the ASSBA is used to fit the optimal surface. Further, the adaptive mesh is planned on the blade profile to extract various evaluation parameters. Finally, the algorithm analysis and verification are carried out based on a certain type of blade. The results show this reconstruction method can get the fitted surface more quickly and accurately than other iterative methods. Simultaneously, the visualization method and corresponding software system can intuitively visualize the blade profile error, the twist deformation error, the swept deformation error, the bending deformation error and the cross-section line profile error.