Flight motion simulator performance improvements from advanced data acquisition

Advances in inertial guidance testing place increasing demands upon accuracy, resolution, and response of motion-based test tables and simulators. These test tables are typically controlled via closed-loop servomechanisms utilizing precision axis position transducers (e.g. Inductosyns(R)(1), resolvers, optical encoders, etc.) to measure axis motion. A new method of acquiring data from these transducers provides greater resolution, repeatability, and accuracy of axis position measurements, enabling more precise control of the axis. The enhanced data acquisition method has been implemented in the Carco Advanced Servo Controller And Decoding Electronics (CASCADE), and is based upon the delta-sigma data conversion process found in high-end data conversion products. Analog signals from the transducer (typically in the form of quadrature sinusoids) are sampled and digitized at a high rate using a high-speed, high-accuracy, medium-resolution data converter. These samples are processed digitally using FPGA and DSP technology to produce a high-accuracy, high-resolution axis measurement at a lower sample rate. The resulting axis measurement provides superior accuracy resulting from the minimization of analog signal processing stages and the errors (offset, gain errors, etc.) that they introduce.