Precision motion control is becoming increasingly more important in the areas of nanotechnology. Lithography, for one, is requiring greater precision as transistor density continues to increase. Permanent magnet synchronous linear motors (PMSLM) are among the most prevalent in precision machines due to their long-range travel, high force density, and high precision and accuracy. Lack of mechanical coupling needed, versus rotary motors, and in conjunction with an air bearing eliminate many disturbances such as backlash and friction. We extend optimal minimum power commutation for a single n-phase Halbach linear motor to multiple linear motor systems, such as the Sub-Atomic Measuring Machine (SAMM), having four 6-phase halbach linear motors and Multi-Alignment and Positioning System (MAPS), having four 3-phase halbach motors. A Halbach linear motor produces an independent levitation force along with the thrust force. A new optimal commutation algorithm is proposed where minimum power is desired subject to a heat symmetric solution. Minimizing the temperature gradient, will also minimize deformation across the system and would be beneficial in nano-manufacturing systems such as MAPS. The heat symmetric solution is not closed-form and a second-order cone programming (SOCP) problem needs to be solved at each servo cycle. We develop our own SOCP solver that will iterate to a solution within a phase cycle of 110/xs and implement on Delta Tau's Power PMAC real-time control system.
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