Beyond bandwidth in precision linear motor motion stage control: A systems perspective with experimental illustrations

초록

Increasing feedback bandwidth remains an effective and often essential route for improving precision linear-motor stage performance; however, its marginal benefit becomes increasingly constrained when structural flexibility, metrology limits, timing uncertainty, and environmental drift dominate the residual error budget. In advanced motion systems, attainable precision therefore depends increasingly on how precision authority is distributed across control, mechanics, timing infrastructure, metrology, and environmental management. This issue is especially relevant to semiconductor and display manufacturing, where nanometer-level positioning must be achieved under high acceleration and high-throughput operation. Under such conditions, structural flexibility, support-path dynamics, sensor-placement constraints, and implementation delay limit servo bandwidth and settling performance. Advanced control methods, including disturbance observers, robust and multivariable control, and feedforward, preview, and learning control, can improve tracking performance without relying solely on higher loop gain. Their practical benefit, however, is constrained by implementation factors such as time synchronization, network jitter, loop partitioning, cable and electromagnetic interference, and thermal-and humidity-induced measurement drift. This paper presents a systems perspective on these developments by synthesizing recent literature through a three-stage interpretive framework: gain-centric feedback control, architecture-centric structured servo design, and toward system-centric precision engineering. A conceptual Precision Authority Allocation Map (PAAM) is introduced as a design-oriented synthesis tool for relating dominant error sources to candidate mitigation authority across control, mechanics, infrastructure, metrology, and environment. Representative experimental illustrations on a linear-motor stage are used to ground the discussion of Era I and Era II, whereas the system-centric interpretation is supported primarily by the broader literature on integrated precision platforms. From this perspective, next-generation precision motion design is increasingly shaped by integrated system interactions rather than by feedback bandwidth alone.

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