Due to advantages such as high speed, high accuracy, low maintenance and high reliability, permanent magnet synchronous motor (PMSM) servo systems have been employed in many fields. In some cases, for example, speed fluctuations caused by load mutation would restrict the control stability, thereby limiting the usefulness of PMSM in high-precision applications. The speed regulation problem of PMSM servo control systems is discussed in this paper. A sliding mode disturbance control is developed in the vector control system to improve tracking performance of the PMSM system in order to suppress the speed fluctuations. The integration of sliding mode control and the proportional plus integral (PI) control can improve the performance of the closed-loop system and attenuate disturbances to a great extent. The proposed method can effectively improve the robustness and response speed of the system. Simulation and experimental analyses are conducted to demonstrate the superior properties of the proposed control method.

Purpose Precision active vibration isolation system (AVIS) is crucial for the mechanical processing equipment in the field of precision manufacturing. Working reliability and efficiency of the system directly influence operating condition of the equipment and the quality of work pieces. Design/methodology/approach A complete structure of the AVIS includes two parts: the excitation part and the passive vibration isolation system (PVIS). The excitation part consists of voice coil motors (VCMs). In this paper, the working process of AVIS is studied particularly via linear simplification on the decoupling model and the mechanical dynamic equations to solve the vibration problem, and they are validated by the experiments. Findings According to dynamic analysis and experiment on an AVIS on different reference points, the VCMs are used as actuators in the AVIS to excite the PVIS, and the performance characteristics of the whole AVIS is well reflected by the amplitude–frequency curves, the bode diagrams and the power spectral density curves. Originality/value This study has provided a way for obtaining the inner structure and working condition of the AVIS, which are essential to better control of the AVIS and to further study it in precision manufacturing application.

A permanent magnet synchronous linear motor (PMSLM) is a linear drive mechanism that converts electric energy into mechanical energy. PMLSMs have been deployed widely in modern precision industrial manufacturing. In this study, an air-gap magnetic field model of a rectangular permanent magnet array in a PMSLM is developed based on the Biol-Savart theorem and the molecular circulation model. Furthermore, an analytical expression for the magnetic field distribution of the air-gap space is derived. Ansoft and experimental measurement are used to model the PMSLM and calculate the magnetic induction intensity and validate the analytical model. The relation between the air-gap magnetic field of a PMSLM and the geometrical dimension of the permanent magnet is analyzed.

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