Improved Position Accuracies of Multi-Axis Motion Test Simulators

In addition to mechanical alignments, precision machine interfaces, and accurate readout transducers, the servo controller is a key component in producing reliable and improved position accuracies. Sub-arc-second accuracies are possible by transducer interpolation and axis calibration. This level of position accuracy is less than a fraction of an inch in angular attitude heading error in one mile of travel. To achieve this accuracy with reliability and repeatability, a new generation of servo controller is needed: one that uses the latest in digital sampling techniques to improve signal fidelity by eliminating noise-prone feedback signals. Position feedback signals consist of a random and a deterministic error. New digital sampling techniques can reduce random errors, while manipulation of stored position calibration data within the controller’s memory can reduce deterministic errors. These techniques have produced a position accuracy of 0.05 arc-seconds and a position resolution of 0.01 arc-seconds. This improved position accuracy relates to an improvement in other specifications as a 0.02% rate error over a one-degree interval.