Relation and influence of all kinds of unbalance torques of three degrees of freedom air-bearing spacecraft simulator caused by gravity

To improve three degrees of freedom air-bearing simulation accuracy and reduce the influence of unbalance torque caused by gravity, a method for calculating and compensating elastic unbalance torque is proposed. After computational model of static, plastic, gravity gradient and total unbalance torque being established, the relation and influence among all kinds of unbalance torque cause by gravity are analysis. It is discovered by contrast that static unbalance torque plays an important role when the platform mass center is far away from the rotation center. With the mass center approaching to rotation center, elastic unbalance torque is gradually becoming the main factor affecting the air-bearing platform balance. Then closing the distance between mass center and rotation center has nothing to do on reducing the unbalance torque, which shows that elastic unbalance torque is the main limiting factor for improving platform accuracy. The principle for mutual compensation between static unbalance torque and elastic unbalance torque is proposed and the compensation algorithm with automatic balancing system is provided. Experimental results have demonstrated application of the compensation method is an important channel for reducing unbalance torque.