Sensor guided motions are online motions, which means that they do not completely follow a pre-planned trajectory, but are to some extent determined by measurements of one or more sensors. In many cases, modifying a pre-planned trajectory based on online measurements of a sensor is desirable. For example, consider a workpiece that is specified to have a flat surface. To let a robot perform operations on this surface, a linear motion should be perfectly suited. However, due to fabrication tolerances, the flat surface may be uneven to some extent. It might be desirable to compensate these unforeseen unevenness by using an appropriate sensor to measure them and perform online correction of the robot’s motion based on the sensor measurements.
In other cases, motion of a robot may be determined completely based on sensor measurements. Consider an application where a robot should follow the movements of a human’s arm, which is tracked by a 3D camera. The arm motion is in general unforeseeable, which raises the need for the robot to perform its following motion completely online.
The Robotics API provides support for both scenarios. This is based heavily on its Sensor model . The first part of this section will explain how to modify pre-planned motions by sensor measurements, while the second part covers mechanisms for completely sensor based motions.