Entwicklung einer Vorrichtung zur Selbstkalibrierung einer 6-DoF-Lastzelle für einen Hartgesteinsprüfstand

Sandvik Mining and Construction G.m.b.H. operates a High-Load-Rock-Cutting-Test-Rig (HLRCTR) for the testing and development of hard rock cutting tools. The objective is the economical and safe extraction of hard rock with UCS values exceeding 150 MPa using undercutting technology. This thesis focuses on the 6-DoF load cell installed at the HLRCTR for measuring the acting forces and moments. Precise calibration and the determination of an appropriate calibration matrix significantly improve measurement accuracy and enable the compensation of coupling effects between individual measurement channels. Two common calibration methods and their influencing factors, which affect precision and measurement accuracy, can be described: static and dynamic calibration procedures. This thesis highlights the importance and growing need for calibration and verification procedures for load cells in industrial applications. To verify the sensitivity of the load cell, calculation models for determining the fingerprints were developed, and a calibration adapter consisting of a welded structure weighing 153 kg was developed; this serves as a reference setup. Through calibration tests with weight variations in the range of 1¿10 kg, linear relationships between the load values and the root mean square error (RMSE) are established. To define the deviation limits, limit load ranges of 500 N for the force component and 100 Nm for the moment component are selected. This results in deviation limits ranging from approximately 4 % for the Fx component up to 48 % for the Fz component. Due to this high deviation, the Fz measurement channel is classified as particularly critical and is therefore only suitable for reliable evaluation to a limited extent. Due to its availability, low complexity, and low investment costs, a static calibration procedure with hydraulic force application for self-calibration is recommended.