Some robot applications require the highest possible accuracy – close to the robot’s repeatability, i.e. typically < 0.1mm – which
robot-cell calibration alone cannot achieve, especially in the case of external dynamic forces (e.g. the pressure exercised by drilling).
The required accuracy should be achieved not just at the robot’s final resting position (as is the case in Robot Guidance – see “Robot
Guidance for Part-to-Part Variation”), but along the entire path followed by the robot’s TCP.
Adaptive Robot Control with the
DynaGuide™ system is the solution for these kinds of applications. A measurement sensor continuously track the robot’s TCP while it
moves along the desired path, and any deviation from that path is instantly compensated. Typical sensors used for such application
are external 3D or 6DOF measurement systems, the latter type of system allowing the actual measurement targets on the end-effector
to be physically located remotely from the TCP. The calculated compensation is generally applied at the TCP’s level for each point
along the path.
Adaptive Robot Control can be performed ‘upfront’ at the initial setup of the robot-cell only, or ‘throughout production’.
In the latter case, the used measurement system (typically an external 3D or 6DOF device) needs to be operating on the plant floor
with a line of sight of the robot’s TCP at all times during the production process: this might make the entire process prohibitively
expensive and might not always be feasible. With upfront Adaptive Control, the measurement system is used at setup only, therefore
not only reducing overall cost but also allowing measurement of the TCP in potentially different conditions than when in production
(e.g. when the part might obstruct view of the TCP). Of course, upfront Adaptive Control is only possible if the initial robot programs
will not need to be changed later on throughout production (no change in fixture location, no constantly changing parts, etc.); a
Temperature Compensation solution should generally also be implemented in such cases.
Adaptive Robot Control benefits from robot-cell
calibration for the same reasons as Robot Guidance – i.e. accurate displacement, minimum collisions, and quick crash recovery – with
the additional benefit of maximizing the efficiency of the compensation process at the TCP for each point along the path. Indeed,
making the robot as accurate as possible at initial setup, minimizes the magnitude of the compensation to be applied at the TCP, which
in turn allows points be compensated at a lower frequency, while minimizing the need for possible iterations – therefore altogether
improving cycle time.
The DynaGuide system is a highly sophisticated software package, integrating several key technologies: it can
interface with multiple measurement sensors, automatically communicates with virtually any robot controller, incorporates robot-cell
calibration, interacts with standard PLC’s, and can populate customer’s data servers. ‘Scripts’ (which have been pre-defined or can
be created from scratch) define what sensor data to use for what purpose, what calculation to perform based on the measurement data,
what tolerance level to accept, what sequence of operations to follow, etc. The DynaGuide system includes both an Adaptive Robot Control
solution as well as a Robot Guidance one (see “Robot Guidance for Part-to-Part Variation”).