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A DSP-based controller for a linear actuator system with sub-angstrom resolution and 15-millimeter travel range

We have designed and tested a new digital signal processor (DSP)-based closed-loop feedback controller for a linear actuator system with sub-angstrom resolution and 15-mm travel range. The linear actuator system consists of a laser Doppler encoder with multiple-reflection optics [1], a high-stiffness weak-link mechanism with high driving sensitivity and stability [2], and a Texas Instruments TMS320C40 DSP-based controller for high-performance closed-loop feedback control. In this paper, we discuss the DSP-based controller design, as well as recent test results yielding step sizes below 50 picometers obtained with the atomic force microprobe setup.