Real-time NURBS curve trajectory generation for a robot using an open-architecture controller

The gap between well-developed CAD systems which provide designers with tools for defining two- and three-dimensional curves and the fact that conventional CNC systems only support the function of straight-line and circular interpolation indicates a need for developing general interpolators for parametric curves such as NURBS (Non-Uniform Rational B-Spline). The Open-Architecture Control (OAC) system method provides a convenient platform to implement real-time interpolation.; This dissertation deals with the issues of real-time parametric curve trajectory generation for a robot using an OAC system. An MEI PCX/DSP motion controller with its host computer, a 90MHz Pentium PC, is used to perform an open-architecture control for a 6-D industrial robot. All necessary hardware connection and software development are included. Using the OAC system as a testbed, a real-time NURBS curve interpolator was developed, implemented and tested; sample runs were conducted; the resulting trajectories were measured by reading the robot's encoders; and the end-effector's vibration was measured by using an accelerometer. The results from the real-time interpolation motion were analyzed, discussed and compared with those from point-to-point approximation motion. The real-time parametric curve interpolator's feasibility, advantages and related issues are also discussed.