Compliance Strategies For Robotic Ground Servicing Of The Shuttle

In contrast to manufacturing robotic applications, many Kennedy Space Center robotic applications require a combination of heavy lift capacity, real-time vision for course positioning of the robot arm and real-time compliance for the final precise positioning of the robot end-effector. Moreover, for some applications, this must be accomplished in a dynamic environment. The design requirements for launch pad robotic applications are more stringent than the requirements for robots operating in a microgravity environment because the lack of gravity relaxes the heavy load and dynamic constraints to a large degree. The compliance of a robotic system is the ability of the robot to adjust the position when external forces are applied to the robot end effector. That is, the robot arm alters its motion in response to the external forces such that the insertion forces are minimized and the probability of the robot harming itself or mating components is minimized. This paper reviews the various compliance strategies that are available to KSC engineers with an emphasis on those techniques currently under evaluation at the KSC/RADL. The compliant strategies are divided into passive and active approaches. Passive compliance is purely a mechanical technique, whereas active requires the interpretation of the output of transducers and interaction with the robot controller