To address the issue of low trajectory tracking accuracy in six-degree-of-freedom robotic arms, this study proposes a trajectory tracking control strategy that integrates a Radial Basis Function Neural Network (RBFNN) with non-singular fast terminal sliding mode (NFTSM) control. (1) The Lagrangian method is utilized to develop the dynamic model of the robotic arm. At the same time, a non-singular fast terminal sliding surface is designed to accelerate trajectory convergence and resolve the singularity problem commonly associated with traditional sliding mode control by integrating nonlinear and fast terminal terms. (2) The RBF neural network is employed to globally approximate and compensate for uncertainties in the model and variations in the parameters of the robotic arm. (3) To confirm the overall stability of the control system with the proposed NFTSM control strategy, the Lyapunov stability theory is applied to formulate a Lyapunov function. (4) The six-degree-of-freedom robotic manipulator is simulated in the MATLAB/Simulink environment to assess the effectiveness of the proposed control method. In addition, experimental validation is carried out on a real robotic manipulator to verify the effectiveness of the proposed method. The simulation and experimental results show that, compared with NFTSM and RBFNN-SMC, the proposed control strategy significantly enhances the trajectory tracking accuracy of the six-degree-of-freedom robotic manipulator, thereby offering an effective and practical solution for its trajectory tracking control.

To clarify the nonlinear degradation of volumetric performance caused by piston–cylinder wear in axial piston pumps under multiple operating conditions, this study develops an integrated framework linking local wear-induced leakage to whole-pump output characteristics. A mathematical model incorporating piston kinematics, eccentric-clearance leakage, chamber-pressure dynamics, and whole-pump flow was established and implemented in Amesim. A four-factor mixed-level orthogonal design and analysis of variance were then employed to quantify the effects of wear clearance, eccentricity, load pressure, and shaft rotational speed. The results show that their contributions to volumetric efficiency follow the order: motor rotational speed > load pressure > wear clearance > eccentricity, whereas load pressure is the dominant factor affecting pressure ripple. A wear clearance of approximately 0.1 mm marks the onset of pronounced leakage-induced performance degradation. At this clearance and a load pressure of 20 MPa, increasing the rotational speed from 500 to 3000 r/min improves the volumetric efficiency from 67.48% to 94.44%, with an average increase of 5.39 percentage points per 500 r/min. Comparative experiments on normal and artificially worn pumps were conducted to validate the model. The measured motor-speed slip under high-load conditions was incorporated to correct the theoretical displacement and distinguish speed-induced flow reduction from internal leakage. After correction, the maximum relative error between the simulated and experimental results was below 3.7%. The proposed framework integrates mechanism-based leakage modeling, multi-factor contribution analysis, and speed-corrected experimental validation, providing a theoretical basis for the wear assessment, piston–cylinder clearance design, and flow compensation of axial piston pumps under variable operating conditions.

In axial piston pumps under variable loading, the system-level excitation and local tribological responses of the slipper pair can become temporally and spatially decoupled. The scientific contribution of this paper is a phase-consistent chain that achieves three things: it resolves the central-pocket pressure boundary with a dual-orifice and dual-control-volume model instead of directly imposing piston chamber pressure, propagates this boundary through posture-dependent clearance to three-dimensional flow–thermal and single-slipper structural responses within the same local cycle, and screens candidate high-risk regions from the spatial proximity and phase relationship of multi-field cycle envelopes rather than from a single peak. The results show that the central pocket pressure exhibits peak attenuation, peak-time difference, and pressure-rate weakening relative to the piston chamber pressure. The steady peak attenuation ratio is $2.83$–$3.33\%$, while pressure-rate weakening under variable loading is $6.29$–$7.14\%$; the high-to-low unloading case gives the largest attenuation of $4.81\%$. Increasing steady load reduces the tilt amplitude and raises the minimum film thickness from about $13.024$ to $13.452\mathsf{\mu }\mathrm{m}$, but the maximum temperature rise increases from $34.12$ to $65.01\mathrm{K}$. A $10\%$ cycle-envelope projection shows no common overlap among the film-thinning, oil-film temperature-rise, and structural-stress core high-response regions with pairwise overlap ratios of 0–$3.27\%$. This traceable chain supports comparative lubrication-safety screening; the identified zones remain numerical candidates rather than experimentally confirmed wear or failure regions.

Existing piston–cylinder lubrication studies often simplify the pressure boundary as a constant load or a single field, making it difficult to capture pump-level pressure excitation, local oil-film response, and non-concentric posture under variable loading. This paper establishes a thermo–fluid–solid coupling framework integrating an AMESim full-pump model, a Fluent transient oil-film model, and a Transient Structural model; UDF transfer of periodic pressure, dynamic meshes, and a calibrated Roelands law were used to analyze parallel-offset and center-tilted postures. As the load pressure increased from 10 to 30 MPa, the maximum discharge–half-cycle temperature rose from 28.39 to 36.95 °C, and the average positive leakage during the third-cycle high-pressure stage increased from 0.0201 to 0.1026 L/min; increasing speed from 1000 to 3000 r/min reduced cycle-averaged leakage by 8.93%. At 500 r/min and 30 MPa, the parallel-offset case reached 46.34 °C, 41 kPa, and 0.0990 L/min in maximum temperature, maximum shear stress, and average leakage, whereas the center-tilted case produced a peak resultant force of 3537.12 N, a cylinder inner-wall high-stress band of 76.96 MPa, and a maximum piston deformation and equivalent stress of 4.31 μm and 83.16 MPa. These results clarify the distinct lubrication behavior and potential uneven-wear risk associated with the two representative non-concentric postures, and provide a basis for clearance design and posture-sensitive condition assessment of axial piston pumps.