Rapid development of mechanical cultivation demands satisfactory wear performance and lower soil adhesion on the soil-engaging components of terrain machinery. A thick 2Cr13 hard coating was used in conjunction with surface textures in this sector. The results showed that 2Cr13 coating and surface texture decreased the friction coefficient and wear rate enormously. The surface wettability of the coating was reduced by a dimpled-surface texture. The adhesion test suggested that dimples greatly decreased the adhesion force by decreasing the friction component and the decrement increased with the increase of dimple size. The adhesion force increased with the soil moisture and then decreased when exceeding the moisture content threshold.

To address the search-and-docking problem in multi-stage prescribed performance switching (MPPS) scenarios, this paper presents a novel compound control method for three-dimensional (3D) underwater trajectory tracking control of unmanned underwater vehicles (UUVs) subjected to unknown disturbances. The proposed control framework can be divided into two parts: kinematics control and dynamics control. In the kinematics control loop, a novel parallel model predictive control (PMPC) law is proposed, which is composed of a soft-constrained model predictive controller (SMPC) and hard-constrained model predictive controller (HMPC), and utilizes a weight allocator to enable switching between soft and hard constraints based on task goals, thus achieving global optimal control in MPPS scenarios. In the dynamics control loop, a finite-time terminal sliding mode control (FTTSMC) method combining a finite-time radial basis function neural network adaptive disturbance observer (RBFNN-FTTSMC) is proposed to achieve disturbance estimation and fast convergence of velocity tracking errors. The simulation results demonstrate that the proposed PMPC-FTTSMC approach achieved an average improvement of 33% and 80% in the number of iterations compared with MPC with sliding mode control (MPC-SMC) and traditional MPC methods, respectively. Furthermore, the approach improved the speed of response by 35% and 44%, respectively, while accurately achieving disturbance observation and enhancing the system robustness.

The microstructure and properties of Cu-0.4wt%Cr alloys prepared by a shortened process and a conventional process were investigated by means of optical microscopy (OM), transmission electron microscopy (TEM), hardness testing and electrical conductivity measurement. After online hot rolling- quenching and cold rolling with 60% reduction and then aging at 450°C for 30min (process A), and solution treatment - cold rolling with 60% reduction - aging 450°C for 60min (process B), good properties combination of the alloys are obtained, and the hardness and electrical conductivity reach to 156HV, 86.4%IACS and 169HV, 81.1%IACS, respectively, and the shortened process (A) is suitable for commercial copper strip production. Plenty of fine and dispersed precipitates are responsible for the hardness and electrical conductivity improvement of the alloys. The difference of properties between process A and B is resulting form the difference of effective precipitates volume fraction under the various processes.