# Assembly Concept

Assembly: Applications where one part needs to be assembled onto another part in a fixed relative pose. In these applications, the poses of both parts are detected by the vision system, and then based upon the assembly requirement, the necessary movements are communicated to the motion system(s).

There are two ways to define two parts' relationship when they are assembled: using paired features and using golden pose.

- Using Paired Features

  When two parts resemble in profile, and should be assembled center to center, then one of them can directly use the other's features as target pose to form a one-one relationship between features of the two parts. The assembly goal in this mode is to minimize the overall position differences between paired features in a least square sense. Before the pose computation, it is required to select and establish the features that are paired between the two parts.

  Here is an example:

  Part A is a film on stage, Part B is a panel on another stage or a stationary platform. The two parts share similar profiles, and the assembly position is center to center. First, the vision system and motion systems are calibrated, and a common coordinate system is established.

  Second, in run time, the vision system detects the feature positions of Part B and Part A. And third, the vision system calculates the position difference between Part A and Part B based on paired features and the compute pose motion device should move to. Following which, the motion system moves either Part A or Part B or both to make them ready to be assembled.

- Using Golden Pose

  This mode is used when these two parts to be assembled are quite different from each other that they can not be paired together. Additionally, even if one-on-one correspondences between their features can be established, but the assembly requirements does not center the two parts together, then the 'Golden Pose' mode is employed.

  Here is an example:

  Part A is a battery on stage, Part B is a metal housing on another stage or a stationary platform. Both parts are rectangular, but their final assembly position is not center to center so the mode should be Using Golden Pose.

  First, the vision system and motion systems are calibrated, which establishes a common coordinate system.

  Then, secondly during train time, both Part A and Part B are placed at desired positions manually, and their features are extracted and trained as golden poses. When they are assembled at their own golden poses, their relative position is exactly as per the application requirements.

  In the third step, during run time, both Part A and Part B's current pose to golden pose differences are calculated by vision system. Following which, the motion system moves either Part A or Part B or both, such that when assembled, Part A and Part B achieve the expected trained relative position.