Jelena Vidaković

A control algorithm for improving the accuracy of five-axis machine tools

An algorithm for reducing the influence of geometrical, thermal, kinematic and stiffness errors in five-axis machine tool components on the desired tool position and orientation is given. This new algorithm is based on the calculation of the cutting tool error matrix for orthogonal machine tools. In the new model of this matrix, all angular errors of the machine links are considered as infinitesimal rotations. The error matrix is a function of the commanded machine component positions and the errors in these positions. To correct errors in the three translational and two angular tool positions, a matrix of commanded tool position and orientation is multiplied by the inverse error matrix in every period of the tool trajectory interpolation. This corrected matrix of the tool position and orientation provides the inverse kinematics used for calculation of the successive links positions required for achieving the given tool trajectory. The control algorithm for five-axis machine tools with the error compensation is implemented both in the CNC system and in the postprocessor. The proposed algorithm is applied on a vertical five-axis turning centre with two translational and three rotational axes. Twenty-four errors that could cause inaccurate machining are recognised on this machine. The machine links and their coordinate frames are denoted using the Denavit–Hartenberg parameters.

Virtual robot in distributed control system

Before the development of robotic systems, it is of great importance to perform verification of various types of scenarios within the machine work and testing. That is especially important in designing the machine with new control logic, before releasing the machine. This paper describes 3D simulator, as part of the offline system, within distributed system for robot control. It is developed in Lola Institute and it provides robot control and monitoring. Parts of the developed system communicate via CORBA protocol, allowing remote control of the robot system through an intuitive graphical user interface.

3D simulator for human centrifuge motion testing and verification

In the process of defining commands and developing algorithms for movements of complex and massive devices, such as human centrifuge, it is unsafe and demanding to perform testing on the real machine. Getting overview of devices operations might be of great importance especially before the final realization. This paper presents a system for programming and simulation of the human centrifuge motion with integrated 3D motion simulator. The simulator is used for verification of newly defined motion commands and testing the new algorithms for the human centrifuge motion.