Study On The Structural Design And Control Methods Of Sanwiched Maglev Nano‐positioning Platform

To meet the needs of the experimental requirements of nano-manufacturing, the assembly and measurements of micro-nano devices, the research and application of micro-nano-electromechanical systems, and to provide a basic research platform for the study on fibre alignment, semiconductor detection, and nano-CMM, a large-stroke high-precision nano-manufacturing platform for nano-processing, assembly measurements and large-scale production is urgently needed with the transition from traditional manufacturing industry to nano-manufacturing industry. The present research was based on a large-stroke two-dimensional magnetic nano-positioning platform with a sandwiched coplanar structure double driven by Halbach magnet array and plane coil. This platform was not only able to perform large stroke two-dimensional movements, detect kinematic accuracy with a nano-precision laser interferometer and make a control loop, but also improve control quality by equipping eddy current damping control system. Plane coils were used to optimize vertical positioning accuracy. Nonlinear control theory was employed for decoupling control on XY direction. The thesis contents are as follows.(1) The Design of System and StructureBecause the mechanical structure has a great effect on the systematic accuracy of precision motion and measurement system, the analysis and optimization of the whole mechanical structure were required to meet the needs of large stroke nano-positioning. The large-stroke two-dimensional magnetic nano-positioning platform in this thesis used a double-driven sandwich-structured electromagnetic system in which a coplanar structure was made from the simultaneous working on the moving platform by the drives from X and Y directions. The coplanar structure can eliminate the effect caused by Abbe error. In this way the motion platform was split into moving platform and working platform, refining platform’s functions and reducing the size. The symmetric moving platform and working platform were flexibly connected to overcome the asymmetric heat distribution in working condition, ensuring the nano-positioning accuracy.(2) Studies on Driven Modes and Electromagnetic Heat of Maglev Positioning PlatformThe platform in the thesis was based on a permanent magnetic linear motor double-driven by Halbach magnet array and plane coil. One set of two same-direction suction-type linear motors above the platform and one set of other-direction repulsion type linear motors below the platform worked together to suspend the positioning platform and drive its non-contact, non-friction and non-abrasion movement. To eliminate the effect of geometric precision error of winding coils on the vertical positioning accuracy, a high flatness which was almost impossible to achieve by traditional loop coil production was required for the coil plane. In this thesis, a design theory to study plane coils which were used to build the stator windings on linear motors was put forward and various researches and experiments were carried out on the workability of plane coils, the feasibility of multi-layer coils, and design and manufacturing technology of reflux lines, which greatly helped to achieve the high flatness precision of coils and establish design theory of plane coils. In addition, the analyses of coil structure, electromagnetic field distribution, driving current, heat generation were carried out to optimize coil parameters. Based on driving ability, analysis of the numbers and distribution of magnetic arrays and coils were conducted. The equations of vertical suspension force and horizontal driving force were analyzed by finite element method, optimizing the electromagnetic system’s parameters and determining the ideal operating point.(3) Studies on the Permanent Magnetic Eddy Current DamperThe large stroke maglev nano two-dimensional positioning platform can be considered a no damping system with small damping ratio and much control difficulty. To overcome this disadvantage, non-contact permanent magnetic eddy current dampers were attached to the maglev positioning platform to improve the control and stability of the system. Because of the outstanding properties, Nd-Fe-B permanent magnets were chosen to build the eddy current dampers. Analytical method and finite element method were used to analyze the dampers. It was proposed to regard the permanent magnetic eddy current dampers as an un-modeled interference term to simplify the system control.(4) Studies on Control SystemMaglev system is a non linear strong coupling system in which the non linearity and coupling interact with each other. To study the double-layer-driven sandwiched electromagnetic system, non linear control theory was suggested to analyze the non linear decoupling control of the maglev system. Linear approximation based on Taylor expansion and exact linearization based on differential geometry were carried out to provide discretization method of feedback linearization control law and to point out the relationship between exact linearization based on differential geometry and space vector control method. Accurate decoupling control was achieved by the combination of exact feedback linearization and modern control theory. The control systems of Maglev positioning platform were built based on double DSP+FPGA. Differential geometrical exact linearization was combined with PID control and sliding mode control to be put into loop positioning control.The studies on large stroke two dimensional magnetic nano-positioning platform, electromagnetic relationship and control system has proved that this sandwiched coplanar maglev positioning platform double-driven by Halbach magnetic arrays and plane coils is a feasible system.