Multiple block look ahead is an invaluable tool for smoothing trajectory paths. By examining the path commands that are immediately following the one being executed, the motion control can optimise acceleration/deceleration to enable motion transitions without judder.
A practical example of the benefit of multi block look ahead is clear;y demonstrated in machine tool controls. When for example, a milling cutter reaches a tight curve in the components machining geometry, rapid deceleration occurs, leaving distinct machining marks on the cut surface. With a look ahead function, the cutting tool path velocity can be adjusted immediately prior to meeting the dramatic path direction change and thereby smooth out the turn. It’s not unlike braking in a car in adequate time before a sharp bend compared with braking at the very last minute before screeching into the corner.
Any time when it is difficult to create the fastest trajectory, that respects machine limits, look ahead is useful. This task is difficult when there is a complex path or complex machine geometries ( such as robot arms ).