Volumetric efficiency (VE) is an extremely important index to evaluate the performance of pump and motor. Efforts have been concentrated on the causes and character of leakage loss, but few quantitative analyses of pump kinematic clearances (KCs) identification and nonlinear compression loss caused by air content are discussed. This paper clarifies the nonlinear compression loss resulted from the air content of the oil in detail and proposes an improved flow loss model of the swash-plate axial piston pump (SAPP). Then, combining the improved model with experimental results, the KCs of SAPP are identified. It has been verified that a reasonable sampling path is useful for reducing sampling numbers and guaranteeing identification accuracy. Finally, the identification and quantization of the wear fault of SAPP are realized by analyzing the estimated value of KCs. The proposed method is simple and easy to implement and shows high predictive accuracy. It provides a possible and promoting technology support for the autonomous calibration of the system parameters and the active compensation of the system control.

容积效率（VE）是评价泵和电机性能的一个极其重要的指标。努力集中在泄漏损失的原因和特征上，但很少讨论泵运动间隙（KCs）识别和由空气含量引起的非线性压缩损失的定量分析。本文详细阐明了油中含气量导致的非线性压缩损失，并提出了斜盘轴向柱塞泵（SAPP）的改进流量损失模型。然后，将改进的模型与实验结果相结合，确定了 SAPP 的 KCs。经验证，合理的采样路径有利于减少采样次数，保证识别精度。最后，通过分析KCs的估计值，实现SAPP磨损故障的识别和量化。所提出的方法简单易行，具有较高的预测精度。为系统参数的自主标定和系统控制的主动补偿提供了可能的和促进的技术支持。