Ultrasonic sensor-based motion control for robotic manipulators

A two-level hierarchical control structure is used to achieve motion-control of a robotic manipulator. A highly-directional ultrasonic distance ranging device is utilized to measure features of interest in the workspace of the robot arm. Off-line trajectory planning is combined with online motion guidance by the supervisory controller to formulate and execute the desired path movement. In a demonstration application, the vertical distance from a workpiece surface was measured and utilized to perform online trajectory adjustment for the robot cutting-tool motion. This makes it possible to compensate for factors such as robot performance limitations, inaccurate fixturing and inexact object location. The hardware implementation and control strategy used to provide verification of the concept are presented, along with the experimental results achieved