Real-Time Control for a Zero Gravity Robotic End Effector

The ability to easily manipulate objects in a zero gravity environment will play a key role in future space activities. Emphasis will be placed on robotic manipulation. This will serve to increase astronaut safety and utility in addition to several other benefits. It is the aim of this research to develop control laws for the zero gravity robotic end effector designed by engineers at NASA Goddard. A hybrid force/position controller will be used. Sensory data available to the controller are obtained from an array of strain gauges and a linear potentiometer. Applying well known optimal control theoretic principles, the control which minimizes the transition time between positions is obtained. A robust force control scheme is developed which allows the desired holding force to be achieved smoothly without oscillation. In addition, an algorithm is found to determine contact force and contact location.