One typical issue to deal with in various robotic applications is the variation from part to part of the location of the fixture holding the part the robot is operating on; another typical case is simply the variation of (the location of) the part itself within the fixture. So, while robot calibration can accurately compensate, at the launch of the production line, for errors in the ‘metrological chain’ formed by the robot, the end-effector, the fixture, and optionally external axes and/or a positioner, that metrological chain is ‘broken’ the minute the part and/or the fixture move relative to their initial location during the calibration process.
‘Robot Guidance’ is the logical way to address such situations where a robot’s final resting position needs to be accurately located relative to the part – despite the varying location of each such part – with less concern of the path leading to that final resting position. A typical example in the automotive industry is the assembly of a door within a door opening on a car body. The DynaGuide™ system provides such a Robot Guidance solution.
Based on the measurement of some datum (or ‘reference’) points on the part, the location of that part relative to the robot coordinate frame is adjusted accordingly. The measurements can be provided by different types of sensors, depending on many factors, such as the kind of datum feature on the part to measure, the allowed cycle time, the sensor’s cost, its ruggedness to withstand plant floor conditions, etc. Furthermore, such sensor can be either mounted at the end of the robot (typically then a single sensor is carried by the robot to each datum feature sequentially), or mounted fixedly on the floor (multiple sensors are then typically used, each sensor measuring one datum feature).