Field of the Invention
The present invention relates to technologies for grasping with a robot hand a workpiece the three-dimensional position and orientation of which are recognized from among bulk workpieces, based on information about measurement by a sensor.
Description of the Related Art
In recent years, bulk picking technologies have been developed in which an individual object is identified from among a pile of workpieces by use of a vision system and then the three-dimensional position and orientation of the identified object are recognized to grasp the object with a hand attached to a robot in production lines in factories, etc. To realize continuous grasp operations of the robot in a short period of time in the foregoing technologies, it is important to preferentially select a workpiece that is graspable in a surface layer of the bulk where interference with a neighboring object is less likely to occur.
Japanese Patent Application Laid-Open No. 2000-304509 discusses a method in which positional information about relative positions of a plurality of workpieces in the bulk is acquired and an overlapping state of the workpieces is acquired from the positional information to preferentially select a workpiece located in an upper area.
In the method discussed in Japanese Patent Application Laid-Open No. 2000-304509, the workpieces are rearranged in descending order according to their positions and orientations, and a workpiece located in a high position is preferentially selected. However, in a case where a region to be used as a reference for the position and orientation of a workpiece is different from a region that is to be grasped with a hand, or in a case where a workpiece with a longitudinal shape is graspable by grasping any of a plurality of regions that are significantly different in a longitudinal direction, it is not possible to preferentially select a workpiece that is graspable in a surface layer of the bulk. For example, FIG. 5 illustrates an example in which workpieces having a long shape in a particular direction are stored in bulk (five workpieces in this example) in a pallet. In FIG. 5, detected workpieces are specified by solid lines and referred to as workpieces A and B. Further, each of the workpieces is graspable by grasping either one of the regions referred to as target regions 1 and 2. In this case, the workpiece A can be grasped without interference with other objects in the surface layer of the bulk if the workpiece A is grasped by grasping the target region 1. However, in a case where a height based on the position and orientation of a workpiece is used as a reference, the workpiece B, which is more likely to interfere with a neighboring object, is selected. This decreases processing efficiency.