It is possible, perhaps you could have an arm attach to the vertical post of the tower. Have a pneumatic cylinder raise the arm when you are ready to hang. Have a FP powered winch to pull the other end of the robot up towards the arm, and have the pneumatic cylinder also pull the robot back up to the arm.
the arm concept is demonstrated here
http://www.youtube.com/watch?v=9TToKIpXpVI