Abstract: To study the influence of pump motors under mixed operating conditions on the steering performance of tracked special vehicles,a performance evaluation model of pump motors under mixed conditions was established. The external characteristic equations for different leakage locations were solved,and key performance parameters such as volumetric efficiency and leakage flow were calculated.Combined with a steering dynamics model,the changes in pump motor performance under various conditions were analyzed. The model enabled the calculation of critical internal performance parameters of pump motors under complex conditions,providing a theoretical foundation for evaluating the steering performance of special vehicles. It is indicated by the result that steering performance was significantly affected by the degradation of the pump motor. As hydraulic system leakage flow increases and volumetric efficiency decreases,central steering time and turning radius increase.Under dynamic steering conditions,steering performance showed a nonlinear relationship with leakage flow and volumetric efficiency. The mixed-condition pump motor model effectively improved the accuracy and applicability of pump motor performance evaluation in special vehicle steering,providing a scientific basis for optimizing vehicle steering systems.

Key words: pumpmotor, tracked vehicles, hybrid model, performance evaluation