Study of an attitude sensing system for precise pointing hexapod

A newly designed attitude sensing system is proposed to realize 3 Euler angles measurement of precision pointing hexapod. The attitude sensing system consists of biaxial inclinometer and laser displacement sensors. Due to the measurement of irrelevant degree of freedom (DOF) is avoided, the complexity and cost of the attitude sensing system is relatively low in comparison with ordinary 6 DOF measurement systems of hexapod. The attitude sensing system´s mathematical model for Euler angles calculation is deduced. Attitude sensing system hardware is developed. To verify the sensing system´s rationality, precise pointing hexapod close-loop pointing control experiment based on the designed system is carried out. The experimental results show that hexapod´s attitude control errors are scale of sub-milliradians which decrease one order of magnitude compare with open-loop one. While, the offline calculation shows that hexapod´s accumulated 3 DOF linear displacement errors after long term movement are in small level which can be negligible in pointing.