| China railway industry is in a stage of rapid development towards high-speed and heavy load. We move from doing theoretical studies on the line to setting the substantial line project as a research object and carrying out the system testing study of the physical lines in the line project subsystems. Track loading vehicle have therefore become one of the essential test equipment. At present, many countries have developed track loading equipment and China has also developed the newly six-axis track loading vehicle in2011. Heretofore, all of the track-loading vehicles have been four-axis. Therefore, it’s very necessary to carry out the dynamic study for the four-axis track loading vehicle and analysis of the operational state on the China’s railway lines. The result of the study could help developing the China’s own six-axis track loading vehicle. This paper will carry out the dynamics optimization analysis and the vertical dead load control on the existing four-axis track loading vehicle, and further investigation of the safety of the four-axis track loading vehicle on fixed-point loading conditions will be calculated.Firstly, aiming at the maximum rate of wheel load reduction which has exceeded China’s standard in the preliminary dynamics analysis of the four-axis track loading vehicle, this paper will make all the indexes including the maximum rate of wheel load reduction in the standard range and get the primary and secondary suspensions parameter scope by means of the optimization analysis on the vertical performance.Secondly, Vertical actuator is set up for the purpose of analyzing influence of the track irregularity on the four axles track loading vehicle. This paper uses the simulation software for the combined simulation of the dynamics and the PI control, and analyzes the influence of the different stiffness of the actuator, the track cycle irregularity and random irregularity on the loading force of the track vehicle when the vertical force is loading to the straight track line. The result demonstrates that using the soft stiffness will improve the stability of the loading force. The track cycle high frequency affects the stability of the vertical loading force and the vertical Ride Index a lot. The middle-wave and the long-wave irregularity have a small influence to the dynamics performances and the stability of the loading force, but the effects to the stability of the loading force of the middle-wave and the long-wave track irregularity which have a high amplitude can not be ignored, especially the20m wave is very sensitive to the loading force. To carry out the PI control on the vertical loading force of the loading vehicle on the straight line which has the worse irregularity, it can promise the vertical loading force constant. The calculation shows PI control has few influences on the dynamic performances of the loading vehicle.The fixed-point loading conditions are calculated at last. The coefficients of overturn stability of all the fixed-point loading conditions are below0.8which meet the standards. With increase of the dynamic load frequency and decrease of the amplitude of the dynamic load, the coefficients of overturn stability decrease whether fixed-point load is exerted on the straight line or the curve. Also, the effect of the vertical static load on coefficients of overturn stability is greater compared with the dynamic load.As demonstrated in the calculation result, all indexes of the four-axis track loading vehicle can meet the standards after the optimizations. The overturning securities of the fixed-point loading conditions are within the acceptable standard range. The vertical load stability can be ensured effectively by PI control of the vertical load force. |
