With the demand for the materials are increasing in the field of military and civilian application with each passing day, an ultrasonic-electric surface modification treatment was employed to improve the surface properties of metal material with different heat-treated conditions. The surface properties of the specimens after conventional cutting and ultrasonic-electric surface modification treatment were characterized, respectively. A grain refinement layer was formed on the surface of different heat-treated specimens after ultrasonic-electric surface modification treatments. The average grain size on the top surface was refined into the submicrometer or nanometers scale. This is caused mainly by two aspects: one is the accumulation of initial tiny particles during deformation; the other is that the ferrite is smashed into pieces due to micro-fatigue damage. Moreover, it was found out the specimens after ultrasonic-electric surface modification treatment had shown the optimal surface properties and friction-wear properties.
Predicting the maneuvering motion of an unmanned surface vehicle (USV) plays an important role in intelligent applications. To more precisely predict this empirically, this study proposes a method based on the support vector regression with a mixed kernel function (MK-SVR) combined with the polynomial kernel (PK) function and radial basis function (RBF). A mathematical model of the maneuvering of the USV was established and subjected to a zig-zag test on the DW-uBoat USV platform to obtain the test data. Cross-validation was used to optimize the parameters of SVR and determine suitable weight coefficients in the MK function to ensure the adaptive adjustment of the proposed method. The PK-SVR, RBF-SVR, and MK-SVR methods were used to identify the dynamics of the USV and build the corresponding predictive models. A comparison of the results of the predictions with experimental data confirmed the limitations of the SVR with a single kernel function in terms of forecasting different parameters of motion of the USV while verifying the validity of the MK-SVR based on data collected from a full-scale test. The results show that the MK-SVR method combines the advantages of the local and global kernel functions to offer a better predictive performance and generalization ability than SVR based on the nuclear kernel function. The purpose of this manuscript is to propose a novel method of dynamics identification for USV, which can help us establish a more precise USV dynamic model to design and verify an excellent motion controller.
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