Control of a double-cascade electromechanical system subject to perturbations

The control of a precision turntable mounted on an orbital spacecraft and designed to reduce the apparent acceleration of a container with a gravitationally sensitive load fixed on the platform is investigated. The platform is modelled by an electromechanical system consisting of three rigid bodies successively connected via electrical motors. All the bodies are able to rotate about a common axis. It is assumed that in the drive bearings there is friction, the parameters of which are unknown and variable, and the torques created by the friction are comparable in magnitude with the acceleration to be reduced. A feedback control law is proposed, which, within a finite time interval, ensures the specified motion of the container relative to the platform.