Sensor-based path planning and motion control for a robotic system for roadway crack sealing

This paper discusses a path planning and control method developed for robotic application in roadway crack sealing. Filling and scaling of roadway cracks is a tedious operation subject to poor working conditions. Application of autonomous robotics to this operation requires a path planning system that can take data representing roadway cracks from an external sensor, extract connected crack paths, and link paths together to form the Cartesian motion for the robotic system used to seal the crack. Since the operation is performed in an on-line fashion, the path planning system has to perform kinematic computations based on dead-reckoning data to update the crack profile as the crack sealing vehicle is moving. Stringent requirements are placed on the controller by the errors inherent in the global path generation, along with the fact that to avoid kinematic singularities, the manipulator used is kinematically redundant. The system developed uses a robust controller known as the simplified Cartesian computed torque (SCCT) to guide the end-effector along with a compliance loop to move the desired trajectory over the crack, while also addressing kinematic redundancy through application of the weighted generalized inverse Jacobian, The contributions of this paper are on developing practical applications of image processing techniques to extract path locations and determine the appropriate Cartesian end-effector paths, as well as the development of a simple but robust compliant redundant robot controller, all for use in the unstructured environment encountered in highway maintenance operations, The system described has been implemented as part of a prototype automated crack sealing machine. Sample results for actual highway data are included.