                       Excerpt from Computer Design
                                April 1992
              NASA EYES RANGE OF FUZZY CONTROL IDEAS IN SPACE
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     NASA has recently reported encouraging research results in a
     number of areas using fuzzy logic.  One of the most advanced 
     projects is a controller for space shuttle proximity operations,
     i.e. maneuvering around or keeping position with respect to 
     another object in space.  Work has been progressing on a fuzzy-
     based translational controller which deals with the parameters 
     of azimuth and angle and their respective rates of change, and 
     the range and rate of change of range with respect to another 
     object.
     
     NASA engineers developed natural language rules to run the 
     controller and are testing it in a multi-vehicle simulation by 
     substituting the fuzzy controller for the simulator's normal 
     human inputs.  The rule base was learned from the experience of 
     human operators and the efficiency of the controller was tuned 
     based on flight profiles recorded from actual missions and 
     simulations.  One of the main advantages in developing the fuzzy
     translational controller were that the engineers did not need to
     construct a detailed mathematical model of the system in 
     advance.  Performance was honed through simulation and 
     experience.
     
     The results of simulations have been encouraging, especially in
     terms of fuel efficiency.   In holding position with respect to
     a target, the fuzzy controller required significantly less
     acceleration (i.e. smaller increments of position change) than
     did the human controlled simulation.  In overall maneuvers, the
     fuzzy controller has shown a 20% to 70% better fuel efficiency
     than the currently used digital auto pilot and the best
     simulation runs of human pilots.
     
     NASA is also exploring other applications of fuzzy control in
     space.  Among the projects being considered are the use of 
     inexpensive cameras for constant tracking of objects around the 
     space station, fuzzy control can contribute to collision 
     avoidance systems, robot arm control and traffic management.   
     At the great distance of interplanetary space where it can take 
     20 minutes to send a signal and receive an answer, robotic 
     systems will have to operate quasi-independently. A fuzzy 
     controller on an unmanned Mars rover vehicle is expected to help
     the rover avoid obstacles and identify and collect soil samples 
     based on imprecise sensor input and only partially known 
     conditions.
     

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