Abstract:The inertial platform is required to have the function of all attitudes in the background of vehicle flexible flight. The three axes platform does not have this function based on the traditional knowledge that the inner frame angle isn’t allowed to be the value close to ?90?, so nails are clenched to the inner frame in order to limit the inner frame angle. To properly depict the movement rules of three axes platform, the shortage in the process of traditional kinematic model is pointed out. Both a new kinematic model and a non-singular all attitude servo loop are given in this paper. Also, a new all attitude decoupling method of servo loop is proposed, which can solve the problem of the moment coupling and moment of inertia coupling. Finally, a new magnitude-adjusted control method based on H∞ control theory is given to adapt to the change of moment of inertia. The simulation results show that the magnitude-adjusted control method can improve the performance of servo loop distinctively relative to the fixed parameter control method.