Automated Collision Free Path Planning

NASA Langley Research Center, Hampton, Virginia

The Automated Structures Assembly Laboratory (ASAL) has successfully assembled and disassembled a 102-member truss structure, including the placement of 12 hexagonal reflector-type panels on the top surface, using a semi-automated system which requires operator attention only when a problem is encountered which the automated system cannot resolve. The system software data base has also been reconfigured so that the system assembles and disassembles a truss beam. The automated assembly system employs commercially available knowledge-based expert systems to plan the assembly, monitor its operation, and assist the operator during error recovery. It also uses a expert system tools plan the sequence of assembly operations and collision-free paths for the robotic manipulator.

During the development and initial operation of the automated structural assembly program, it was shown that the planning of collision-free paths was tedious, time-consuming, and error-prone. Factors contributing to this situation include the complex paths and tight clearances imposed by the truss structure and large, cumbersome end effector necessary to carry the truss struts as well as the limited visibility and poor lighting conditions. Any need for on-line paths due to unexpected situations created critical safety problems for the operator. These considerations led to the development of an automated planner which used knowledge of the truss, end effector, and manipulator arm geometry to generate collision-free paths in an on-line mode. The automated planner uses a computer-generated graphics simulation to allow the operator to preview and approve the paths or even adjust or refine path segments while guaranteeing freedom from collisions. The automated planner saved a significant amount of human resources while enhancing the safety and reliability of the automated assembly operation. Automated path planning tools hold the potential for major cost savings for system setup, programming, and operation for automated commercial or manufacturing applications.

Technology areas:

1. Knowledge-based expert system for planning collision-free automated system operations in unstructured environments
2. Computer-generated graphics techniques for visualizing actions of complex expert systems and for easier interaction with their planning activities

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Maintained by: Dave Lavery
Last updated: May 10, 1996