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In order to solve the problems of wear, lubrication and complex structure of digital oil-free scroll compressor, an oil-free scroll compressor driven by magnetic force is proposed in this paper. The new scroll compressor is driven by electromagnetic force, without anti-rotation mechanism and motor, which reduces mechanical contact, so as to achieve the goal of low wear and oil-free. Back pressure device provides variable axial magnetic force to reduce the vibration of the compressor and ensure that the compressor works under the optimum force. The mathematical model of back pressure device and driving force is established and verified by finite element method. The results are in good agreement. The closed-loop step response of the new compressor is simulated. The gas force is decomposed and analyzed. The analysis, calculation and simulation results show that the back pressure device and the driving device meet the requirements of the compressor.

The establishment of the analytical model of the rotor eccentric surface-mounted permanent magnet synchronous motor (SPMSM) with unequal magnetic poles structure will be beneficial to calculating the magnetic field and studying noise characteristics quickly. Based on the equivalent surface current (ESC) method and equivalent boundary method, the analytical model of the rotor eccentric SPMSM with unequal magnetic poles structure is proposed. During the modeling process, the magnetic field produced by a permanent magnet (PM) is obtained using the ESC method, and the effect on the air gap magnetic field, which arised from stator, is replaced with the concentric current sheet (CCS) magnetic field. And, the analytical results of the magnetic field are confirmed by FEM. According to the analytical model of the SPMSM, the effect on the noise characteristics, which resulted from rotor eccentricity, is researched. Moreover, the experiments of noise comparison are done. The results validate the validity of noise characteristic research. Then, the analytical model of the SPMSM is further verified.

The adjustment times of the attitude alignment are fluctuated due to the fluctuation of the contact force signal caused by the disturbing moments in the compliant peg-in-hole assembly. However, these fluctuations are difficult to accurately measure or definition as a result of many uncertain factors in the working environment. It is worth noting that gravitational disturbing moments and inertia moments significantly impact these fluctuations, in which the changes of the peg concerning the mass and the length have a crucial influence on them. In this paper, a visual grasping strategy based on deep reinforcement learning is proposed for peg-in-hole assembly. Firstly, the disturbing moments of assembly are analyzed to investigate the factors for the fluctuation of assembly time. Then, this research designs a visual grasping strategy, which establishes a mapping relationship between the grasping position and the assembly time to improve the assembly efficiency. Finally, a robotic system for the assembly was built in V-REP to verify the effectiveness of the proposed method, and the robot can complete the training independently without human intervention and manual labeling in the grasping training process. The simulated results show that this method can improve assembly efficiency by 13.83%. And, when the mass and the length of the peg change, the proposed method is still effective for the improvement of assembly efficiency.

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