Design of supper low disturbance torque air bearing table with active compensation

As the output moments of reaction wheels for micro-satellites and nano-satellites are the same as the disturbance moment of an Air Bearing Table (ABT), the attitude dynamic simulation and ground test of the micro-satellites and nano-satellites can not be implemented directly by the ABT. To solve the problems, an active compensation ABT with a supper low disturbance moment was designed and developed. The disturbance moment of the ABT was analyzed and three kinds of methods to reduce the disturbance moment were proposed. Firstly, the viscous damping moment was reduced by optimizing design; Then, the vertex moment was reduced by setting sloping slant orifices to generate an active vertex to balance the inherent vertex of the air bearing, and to reduce the inherent vertex moment. Finally, the swing characteristics of air bearing was used to implement high precise balance adjustment and to reduce the gravity induced moment. A measuring device of micro-moment was designed and the remaining vertex moment was measured and the measuring results were used to direct the compensation of the vertex moment and gravity induced moment. Experimental results indicate that the disturbance moment of the ABT is smaller than 5×10^-5 Nm, which is less than the minimum output moment (1×10^-4 Nm) of the reaction wheel. Obtained results satisfy the requirements of the ground simulation of attitude dynamics and the control of micro-satellites and nano-satellites.