"Autonomous on-orbit services, such as capturing, refueling, and repair and refurbishment
of an on-orbit satellite using a robot mounted on service satellite, will be one of the important
components of the space missions in future. The main objective of capturing faulty satellites/debris
is to avoid their possible collision with a working satellite in the same orbit. Use of space robots
boosts the reliability, safety, and ease of execution of operations. Driven by this motivation, an
attempt has been made in this work to develop a framework for impact modeling of a multi-arm
robotic system mounted on a servicing satellite while the capture of tumbling orbiting objects. A
robotic system with multiple arms would be capable of capturing multiple objects simultaneously.
Further, when the satellite is in broken state or does not have provision for grapple and tumbling,
the interception is very difficult. In such cases, interception using multi-arm robotic system can
be appealing as this will increase the probability of grasp in comparison to the single-arm robot.
In this work, three phases of the capturing operation, namely, approach, impact, and post-impact
have been modeled. In the approach phase, the robot is traveled from its initial configuration to the
desired configuration. It is essential that at the time of interception the velocity of the end-effector
should be equal to that of the point to be grasped in order to avoid any impact. Hence, the main
objective in approach phase is to move end-effector from point-to-point with desired final velocity.
But in practice, there will be a non-zero relative velocity between the end-effector and the grapple
point, leading to an impact. In the impact phase, a framework is developed to estimate the changes
in the generalized velocities caused by the impact. In post-impact phase, these velocities are used as
an initial condition for the post impact dynamics simulations. Efficacy of the framework is shown
using a dual-arm robot mounted on a servicing satellite performing capturing operation for two
objects, in the case of open-loop impact and for the single object, in the case of closed-loop impact.
The effects of relative velocity and angle of approach on the impact forces have been investigated.
i"