Compensation of friction effects in gyro-stabilized motion platforms

A frequent problem encountered in the stabilization of gyro-stabilized motion platforms is the disturbance rejection associated with moving components. Due to relative motion of adjacent components, friction is induced by the destabilizing force from the base motion to the stabilized object, degrading its motion accuracy. Hence, a compensation of frictional effects is necessary in order to obtain a highly precise stabilization performance. In this paper, applications of both single-state disturbance observer and well-known LuGre friction model on gyro-stabilized motion platforms is presented to compensate for friction. The compensation techniques are described for a generalized control system and simplified for a specific case. The success of these techniques is validated via experiments and simulations by constructing a block diagram of the system stabilization loop. An added disturbance observer yields a similar improvement in the stabilization performance as the LuGre friction model does at low frequencies. However, the performance of disturbance observer degrades as the frequency of disturbances increases although it still improves the overall stabilization performance of the system.