Behaviour based visual servo controller for satellite capture

Abstract

Unmanned space servicing requires an ability to capture a free-floating satellite, replace a module and deploy the satellite using a robotic arm. As direct teleoperation from the ground is not possible due to limitations of the communication link (delay, bandwidth and intermittence) the servicers will therefore have to operate with a certain degree of autonomy. The need for autonomy is particularly high for operations in dynamic or uncertain environments, conducted in proximity between a servicer and the satellite and involving contact. Capturing of a free-floating satellite requires integrating estimating motion of the satellite using on-board sensors and closed loop control of the manipulator. This is quite a challenging task as such operations are performed in zero gravity when both satellites are moving independently in all 6 degrees of freedom, and motion of the arm induces motion of the servicer. Failed capture may cause the target satellite to spin and delay another capture attempt, as the satellite stabilisation might be required. If the satellite cannot be controlled from the ground this may lead to abandoning the servicing and loss of the satellite.