An Airborne Design of Inertial Stabilized Platform for Cold Atom Gravimeter

The airborne absolute gravity measurement based on the cold atom gravimeter can obtain absolute gravity information of the Earth, which is an important way to study geological changes of the Earth. At present, the dynamic absolute gravity measurement system of a cold atom gravimeter based on an inertial stabilized platform has been applied to the ocean mapping experiment. For the purpose of further conducting experiments on airborne absolute gravity measurement, considering features such as the confined space within the aircraft, high flight velocity, and strong turning maneuverability, an airborne inertial stabilized platform design for cold atomic gravimeters is proposed in this article, which optimizes the structure of the platform and the control algorithm based on the design of the shipborne inertial stabilized platform. The airborne inertial stabilized platform adopts a two-axis, three-frame structure, and the probe of the gravimeter and the inertial navigation system (INS) are integrated into a single structure, which facilitates assembly and maintenance. Then the volume and weight of the airborne inertial stabilized platform are greatly reduced. The control system adopts a compound control algorithm of terminal sliding mode and linear extended observer, which ensures fast response and reduces overshoot at the same time. In order to verify the accuracy of the dynamic absolute gravity measurement system, a fixed-point dynamic absolute gravity measurement experiment is carried out in the laboratory, the accuracy of which is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.9\times {10}^{-{6}}$ </tex-math></inline-formula> Gal. Then, an airborne absolute gravity measurement experiment is conducted in Hebei Province. During the flight, the root mean square (rms) of the steady-state accuracy of the inertial stabilized platform is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.0084\times {10}^{-{3}}$ </tex-math></inline-formula> rad in roll and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.0205\times {10}^{-{3}}$ </tex-math></inline-formula> rad in pitch. The accuracy of absolute gravity measurement is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times {10}^{-{3}}$ </tex-math></inline-formula> Gal in this flight. The flight experiment results show that the inertial stabilized platform provides reliable horizontal attitude accuracy for the dynamic absolute gravity measurement of the cold atom gravimeter.