Abstract
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.
Highlights
With the rapid development of intelligent manufacturing, industrial robots have been widely applied in automobile manufacturing, logistics systems, mechanical processing, food packaging industries, etc. [1]
According to the report of the International Federation of Robotics (IFR), more than 72% of industrial robots are used in the lowprecision occasions, e.g., sorting, palletizing, handling, spot welding, painting, and assembly of simple parts [2] for the positioning, and the trajectory accuracy of industrial robots is still relatively low [3]
The open-chain structure results in a low stiffness and an error accumulation amplification which are the main reasons for the low accuracy of industrial robots. erefore, improvement of the stiffness error has always been an important research field for industrial robots
Summary
With the rapid development of intelligent manufacturing, industrial robots (noted as robots) have been widely applied in automobile manufacturing, logistics systems, mechanical processing, food packaging industries, etc. [1]. (1) A novel positioning error model is proposed for ndegree-of-freedom (DOF) industrial robots based on the relationship between its kinematics and dynamics parameters, which can be applied to arbitrary multi-DOF serial robots (2) e Newton–Euler method is introduced to calculate the balance torque of joints, which makes it convenient to calculate the positioning error caused by the EE loads and gravity of the robot (3) e radial deformation error at joints is modelled and included into the stiffness error model, which improves the accuracy of prediction and compensation for positioning error compared to the traditional methods (4) e positioning error model is linearized by introducing proper assumptions, which reduces the complexity of the proposed method and makes it convenient to applications e rest of the paper is organized as follows: in Section 2, the displacement and deformation at joints of robots are analyzed with the gravity and EE load.
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