## 1 Introduction  
The positioning accuracy of the gripper is one of the main characteristics of robots. A number of factors affect the resolution, accuracy and repeatability of industrial robots. Accuracy and repeatability describe the robot's ability to follow a given trajectory with little or no variance. Two types of accuracy are considered: absolute accuracy (accuracy of the robot when returning to its previous position during repeated movement) and relative accuracy (accuracy of positioning the robot for any point of the workplace relative to a known coordinate system). The characteristics of robots, such as resolution, accuracy and repeatability, are the subject of many scientific studies [1; 2; 3; 4; 5; 6; 7], which solve various problems regarding the influence of variations in the length of the manipulator link, relative orientation of joints, friction, temperature, load, manufacturing tolerances, and drive characteristics. The accuracy of robots is affected by the movement of heavy masses at different speeds and the elasticity of links [8; 9], as well as gaps in joints and inertial forces, including Coriolis inertial forces. Accordingly, during operation, the positioning accuracy of the robot gripper is adjusted [10; 11; 12]. Positioning accuracy is a critical indicator of robot efficiency [13]. Errors that lead to the low positioning accuracy of industrial robots can be divided into two categories: geometric and non-geometric errors. Geometric errors can be reduced by parameter identification and compensation, which can reduce the errors between nominal and actual parameters. Industrial robots have an open kinematic chain, which causes low structural rigidity and nonlinearities in movement, which affects the overall positioning accuracy of the robot gripper [14; 15]. A number of studies are aimed at analyzing the characteristics in order to increase the productivity of the robot [16; 17; 18; 19; 20]. Positioning is of great importance for industrial robots in high-tech industries. [PERSON] et al. propose a method of increasing the positioning accuracy of an industrial robot, which takes into account both the errors of kinematic and dynamic parameters. The method consists of using the improved Denavit-Hartenberg function to create a kinematic model and identify geometric errors. Then the deformation of the connection is analyzed, and the angular deviation of each connection due to the final load is compensated [21]. [PERSON] et al. considered typical linear and non-linear models and various calculation methods for dynamic robot calibration. Using simulations, the authors analyzed the features of various methods, including torque error, parameter error, model adaptability, solution time, and the ability of calibration results to counteract the interference [22]. In particular, [PERSON] et al. checked the accuracy of a dynamic model of a planar robotic arm using gravity tests [23]. Accuracy depends on a number of factors including, but not limited to: the parameters of the actuators that guide the robot's movements, the tolerances in the manufacture of structural elements, tolerances due to the hinged connection of robot chains [24], control algorithms [25; 26], the dynamic properties of a mobile platform [27; 28], and the properties of the robot manipulator [29; 30]. Each of the factors can become important for the accuracy of the robot depending on its type, load capacity, and operating conditions [24]. Positioning errors in autonomous mode can be determined using special algorithms [31] and mathematical models [32; 33; 34; 35]. Common problems of positioning accuracy in path and trajectory planning can be solved by improving autonomous programming software, where the code for the robot is automatically generated, or by implementing online feedback [36; 37; 38; 39; 40]. However, typical compensation methods are limited by the chaotic nature of positioning errors.