Technical University of Varna

The paper presents advanced methods for motion planning and sensor filtering in differentially driven robots. The focus is on the comparative analysis between the standard PID control and the proposed modified version of the vector field histogram (VFH) algorithm for obstacle avoidance. Methodology for local positioning using sensor fusion of data from the encoders and gyroscope module is presented. The results show a significant reduction in data processing latency and improved trajectory smoothness when passing through critical sections of the testing track.

The paper reveals an alternative technique for application of the modified variational approach with transferring coefficients for analysis of non-linear magnetic circuits operating in constant regimes. That specific technique is developed for analysis of non-linear magnetic circuits on the base of the basic laws for the magnetic circuits. That variational method is based on a special theorem for variational analysis of electric circuits, which is reformed for the case of magnetic circuits, using analogy between the electric and magnetic circuits. A corresponding methodology, which facilitates the application of the modified variational approach with transferring coefficients for analysis of non-linear magnetic circuits, is developed for that case. Some practical examples for variational analysis of non-linear magnetic circuits are presented in order to illustrate the peculiarities of that new approach.

This paper presents a methodology for extracting and calibrating the B–H characteristic of a steel load plate in a three-phase split-phase inductor. The magnetic core characteristic is assumed known, while the plate behavior is identified from experimental measurements using probe coils. An initial plate B–H curve is derived from measured electrical quantities through a field-consistent formulation that separates core and plate magnetomotive contributions. The extracted characteristic is subsequently refined using finite element method (FEM) simulations, where the plate B–H curve is iteratively adjusted until the simulated current response matches the measured one under identical excitation conditions. The results demonstrate that direct experimental extraction alone is insufficient due to distributed flux effects, and that FEM-assisted calibration provides a physically consistent and accurate plate characteristic. The proposed approach establishes a reliable bridge between measurement and numerical modeling for complex magnetic systems.

The present research investigates the optimization of ball burnishing (BB) process parameters to create regular lubricating grooves on multilayer connecting rod liners to prevent engine seizure. The study utilized a Taguchi L9 fractional orthogonal array to evaluate the impact of ball diameter, deforming force, and feed rate on the resulting groove widths. Statistical analysis (ANOVA) revealed that ball diameter is the primary driver of groove width variation, exhibiting a non-linear parabolic relationship where the diameter serves as a stabilizing threshold. While deformation force showed a steady linear progression in widening traces, higher feed rates were found to restrict localized plastic flow, resulting in narrower groove widths. For the bimetallic structure (steel back with AlSn20Cu coating), the research recommends tailoring forces to the specific layer—forces for the anti-friction layer and for the substrate to avoid structural destruction. Profilometry confirmed that the height of edge inflows directly correlates with groove depth, ranging from 6 to 30 μm. The optimized non-linear regression model developed in this study achieved an exceptionally high coefficient of determination (R2 = 99.84%), ensuring precise predictive accuracy. Overall, these findings provide a robust framework for researchers to enhance the durability of heavy-duty engine components through controlled surface topography.