Apparatus and method of distributing object handling

Details Apparatus and method of distributing object handling Apparatus and method of distributing object handling

1999-11-24

2001-08-21

Cuchlinski, Jr., William A. (Department: 3661)

Data processing: generic control systems or specific application

Specific application, apparatus or process

Robot control

C700S246000, C700S248000, C700S252000, C700S260000, C700S261000, C700S251000, C700S262000, C700S263000, C700S264000, C318S567000, C318S568100, C318S568120, C701S201000, C701S301000, C901S001000, C901S007000, C901S046000

Reexamination Certificate

active

06278907

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of Invention
This invention is directed to apparatus and methods of distributed object handling.
2. Description of the Related Art
A traditional media handling system can move media, such as a sheet, from one location to another location along a path, while performing one or more operations on the sheet, such as inversion, image transfer or fusing. As shown in
FIG. 1
, a traditional media handling system
100
includes a controller
110
that controls multiple actuators
130
, which perform operations on the sheet while moving the sheet along a paper path
140
.
Typically, timing signals are used to coordinate the operations and sheet movement. For example, the sheet can be fed into the path
140
at a certain time according to a timing signal. The sheet can then move through the path
140
, past various position sensors within a certain time window, and arrive at a transfer station at a specific time.
SUMMARY OF THE INVENTION
However, this traditional media handling system
100
is subject to the problem that when any temporal error in the operations beyond a certain tolerance is detected and flagged to the controller
110
, the machine containing the traditional media handling system
100
is shut down. The traditional media handling system
100
does not include any feedback control. Thus, the actuators
130
need to be precisely manufactured, which is expensive. Also, because of this lack of feedback control, the traditional media handling system
100
does not perform well when subjected to different types of media, and has problems maintaining accuracy and reliability at high speeds.
A modular object handling system can overcome these problems via a more control-centric design, which can be accomplished by adding more controls. The use of control strategies, beyond the simple timing of the traditional media handling system
100
, can also allow a wider range of objects, such as a wider range of media types, to be handled at higher speeds.
For example, a modular object handling system that includes a multi-level control architecture can provide advantages over the traditional media handling system
100
discussed above. This modular object handling system can include a system controller that coordinates the functions and/or the operations of individual module controllers, which in turn control corresponding actuators, to provide a desired system function, such as transporting objects along a path. In particular, the system controller can download an overall trajectory for each object to the module controllers. The module controllers can control their respective actuators to maintain each object on its planned trajectory while in that module.
The system controller performs the overall trajectory planning by taking the constraints of each of the module actuators into account. The trajectories planned by the system controller can then be provided as functions in distance-time space, such as cubic splines.
Deviations from an object's desired trajectory typically occur during the operation of the modular object handling system. For minor deviations, all control can be left to the individual module controllers, since they may not be concerned with other module controllers or whether the overall control criteria are satisfied. However, the system controller is concerned with satisfying the overall control criteria. Thus, the system controller may constantly monitor the location of the objects and contemporaneously redetermine the objects' trajectories using various control techniques to make up for such deviations.
However, continuously replanning trajectories by accessing complex trajectory re-determining techniques can be difficult to accomplish in real time. In fact, depending on the equipment and software involved, it may be necessary to resort to approximate determinations and heuristics to identify the effects of deviations and to replan the deviating trajectories in real time.
Thus, instead of continuously replanning the deviating trajectories, it may be desirable to use predetermined trajectories and trajectory envelopes to encode the various combinations of system constraints and task requirements. The trajectory envelopes can denote regions around other trajectories to indicate control criteria of interest, such as control and collision boundaries. By comparing the current state of an object with the predetermined trajectory envelopes, the system controller can quickly determine the extent to which the current state satisfies the control criteria.
For example, instead of continuously checking the distance between objects and re-determining the trajectories to avoid collisions, a predetermined collision envelope around the desired trajectory can be used. The predetermined collision envelopes are determined such that, as long as the objects are within their collision envelopes, the objects will not collide. A control envelope can similarly be used to determine other control criteria, such as whether the object will reach its target on time to accomplish a task requirement. This modular object handling system simplifies on-line determinations to merely include a comparison between a particular trajectory and the corresponding trajectory envelope, or between a current object position and a trajectory envelope.
The systems and methods discussed above predetermine a trajectory, as well as well as at least one predetermined trajectory envelope that is associated with the trajectory, for each object moving along the path. However, if the predetermined trajectory envelope is large and/or an the object deviates a large amount from the predetermined trajectory, then an unnecessarily large amount of energy may be exerted in attempting to place that object back on that object's predetermined trajectory.
To avoid this, multiple trajectories, as well as trajectory envelopes associated with each of the multiple trajectories, can be determined for each object. The apparatus and methods of the invention can then monitor the status of each object, and switch between the multiple predetermined trajectories in order to actively improve energy usage efficiently. The apparatus and methods can also modify the trajectories of other objects to avoid collisions with the object whose trajectory was originally switched.
These and other features and advantages of this invention are described in or are apparent from the following detailed description of various exemplary embodiments of the systems and methods according to this invention.


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Behera et al., Neuro-adaptive Hybird Controller for Robot-Manipulator Tracking Control, 1996, IEEE, pp.270-275.*
Canny, On Computability of Fine Motion Plans, 1989, IEEE, pp. 177-182.

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