PATH PLANNING WITH OBSTACLE AVOIDANCE AS APPLIED TO A CLASS OF SPACE-BASED FLEXIBLE MANIPULATORS

The present study is a natural extension to the earlier work carried out by the authors in the area of nonlinear control of flexible structures using the Feedback Linearization Technique (FLT). This procedure accounts for the complete nonlinear dynamics of the system. It develops a rather innovative approach to path planning for a 2-link flexible manipulator, with a specified target and several arbitrarily positioned obstacles. It is important to point out that the presence of link vibrations makes the problem st least an order of magnitude more complicated rendering the conventional algorithms developed for rigid systems virtually of little use. The problem involves generation of regions (contours) representing spheres of influence around the finite size obstacles, with various degrees of permissible penetrations during path planning to the target. To begin with, equations of motion of an orbiting flexible manipulator, undergoing planar slewing maneuvers, are obtained accounting for a shift in the center of mass during maneuvers. Next, a composite control procedure, involving the FLT together with active vibration suppression using piezo-electric actuators, is developed which promises high degree of tracking accuracy. Depending on the performance requirement of the mission, penalty functions are assigned for a given performance index pertaining to the flexible dynamics of the systems. This permits global improvement of the manipulator operation. Finally, effectiveness of the collision avoidance scheme is illustrated through several examples of increasing complexities.