Closed-Loop Control of Micro-Accelerometers Using LabVIEW FPGA
Keywords:Sigma-Delta; LabviewFPGA; Closed-Loop Control; Accelerometer
This application note describes a method to design a closed-loop control of a micro-accelerometer, using the LabVIEW (short for Laboratory Virtual Instrumentation Engineering Workbench) environment from National Instruments (NI) and a field-programmable gate array (FPGA). This document is intended for researchers:
who wish to implement an application-specific I/O device using an NI FPGA-based data acquisition (DAQ) module, and/or
are interested in microsystems, control systems, and FPGA-based signal processing.
This application note explains how to design:
an open-loop accelerometer model using a LabVIEW VI (Virtual Instrument),
a closed-loop accelerometer model with electrostatic force using a LabVIEW VI,
a system that includes a closed-loop accelerometer, a capacitive-based signal pick-off that converts displacement to capacitance, a readout circuit that converts capacitance to voltage, and a first-order Sigma-Delta (ΣΔ) oversampling converter, and
a feedback loop, implemented on a FPGA-based DAQ module, which minimizes the displacement of the accelerometer’s proof mass and centers its position. This feedback loop includes a proportional integral derivative (PID) controller, a low pass filter and an oversampling ΣΔ digital to analog converter (SD-DAC).