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This paper develops a novel sliding mode control technology and a comprehensive evaluation methodology for speed control of permanent magnet synchronous motor (PMSM). In most of the existing literature, only control precision of the speed corrector is investigated. However, the control strategy should be stable to the noise and disturbance caused by the environment and parameter uncertainties. In order to possessing faster dynamic response, stronger anti-interference ability and high stability of input, a highly stable sliding surface is proposed for siding mode control. Unlike most of reaching laws that requires the variation of designed sliding surfaces, this method takes state vectors in consideration. In addition, a comprehensive evaluation algorithm is presented to obtain reasonable assessment on speed control for synchronous PMSMs in different operating phases (starting, transient, steady-state rating). Finally, the simulation results verify the effectiveness and validity of the proposed sliding mode speed controller.

RTCP (rotation tool center point), which is one of the necessary functions for high-grade CNC machine tools, can effectively decrease nonlinear errors caused by the motion of the rotation axis and improve the accuracy of the machinery. Based on the characteristic that the cutting tool tip point is relative to the manufacturing workpiece, the RTCP trajectory is proposed to conveniently measure the displacement of the tool tip point. The scheme is utilized to study the dynamic performance of machine tools, and a simulation that shows the relationship between the tool tip error trajectory and the factors influencing the dynamic performance of the machine tool is presented based on the servo system model. Then, the experiment is carried out, and the tool tip point error variation is found to be consistent with the simulation result. This study provides theoretical support for dynamic performance detection of five-axis CNC machine tools.

A maintenance interval optimization model for wind turbine gearbox considering the maximization component profit per unit time was presented in this paper. First, the principle and configuration of gearbox were introduced, and the failure characteristic is analyzed as well as the failure rate distribution of components in gearbox. Then, the concept of component income coefficient λ and element utilizing rate per unit time U(t) were given. λ describes the proportion that component takes up the total income of wind turbine electric power sale，and U(t) represents the average income per unit time to wind turbine electric power sale during 0~t. Based on above two concepts the model of optimizing maintenance interval was proposed. Last, the paper used the proposed method to evaluate wind turbine gearbox maintenance interval in an actual wind farm. The simulating results indicates that the component profits per unit time for gears, intermediate speed shaft bearings and high speed shaft bearings increases by 16.88%, 30.26% and 32.59% respectively.

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