New Contact Force Measuring Method for Overhead Catenary Systems Based on Strain

Pantograph dynamic contact force is the key factor for assessing the current collection quality of a pantograph, operation conditions of the catenary, abrasion on the pantograph slide, and the localized defect detection of the catenary. Taking into account the drawbacks of currently used methods, a new contact force measuring method based on optical fibre strain sensors is proposed. First, the pantograph head was simplified to a freely supported beam, the strain responses under the effect of a concentrated force acting on the pantograph head were analysed, and a new model for calculating the contact force was developed. Next, the linear relationship between the strain responses and the acting force was proved via static tests, and the equivalent stiffness and equivalent strip length were calibrated via static tests. The veracity of the proposed measuring method was proved via dynamic tests. Furthermore, the reliability of the method at high frequencies was verified via simulation. Finally, the contact force measured before and after inertial force correction were compared to the corresponding actual values. The results indicate that the effect of the inertial force on the contact force increases with increasing frequency. The measurement errors of the minimum and maximum values of the contact force, without considering the inertial force, are 26.57% and 11.13%, respectively, at 10 Hz. These large error values indicate that the inertial force cannot be ignored. After inertial force correction, the measurement errors of the minimum and maximum values of the contact force reduced to 3.12% and 1.54%, respectively. Thus, the measured values of the contact force are in good agreement with the corresponding actual values.