Data processing: generic control systems or specific application – Specific application – apparatus or process – Robot control
Reexamination Certificate
1999-05-28
2001-04-10
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Robot control
C700S250000, C700S260000, C700S261000, C700S262000, C414S217000, C414S744500, C414S744600, C414S935000, C414S936000, C414S937000, C318S568210
Reexamination Certificate
active
06216058
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to robotic manipulators and, more particularly, to a method and means for the reliable and numerically efficient generation of constrained time-optimum trajectories for the simple and compound or blended moves of single-arm, dual-arm, and multi-arm robotic manipulators.
2. Prior Art
Single-arm, dual-arm, and multi-arm, i.e., single end effector, dual end effector, and multi end effector, robotic manipulators are used in various types of transport apparatus in embodiments well known in the prior art. Examples of typical transport apparatus including such embodiments are described in U.S. Pat. Nos. 4,730,976, 5,180,276, 5,404,894, 5,431,529, 5,647,724, 5,655,060, 5,765,983, and in pending U.S. application Ser. No. 09/163,844, the latter having an assignee in common with this application, and the disclosures of all of which are incorporated herein by reference. In an embodiment such as used with a substrate transport apparatus, the transport arms have the end effectors mounted thereon for carrying substrates, such as semiconductor wafers or flat panel displays, through suitable trajectories for processing. The substrate is typically held by means of frictional force between the substrate and the end effector, which force may be supplemented or accompanied by a vacuum or electrostatic holddown in some applications. Therefore, the substrate will slide if the inertial force at the substrate exceeds the holding force securing it to the end effector, so that the transfer time is limited by the magnitude of this holding force. Furthermore, additional constraints, such as limited velocity and jerk, are typically required for safe operation and trajectory tracking reasons. Accordingly, a computationally efficient system that calculates a transfer trajectory without causing the substrate to slide and without violating prescribed constraints is required for maximum substrate throughput levels. In an existing approach, e.g., refer to U.S. Pat. No. 5,655,060, a backward trajectory (backward from the end position of the move) and a forward trajectory (forward from the start position of the move) are calculated iteratively and blended. However, the present state of the available methods, in this exemplary approach and other embodiments, for achieving iterative trajectory generation with the known multi-arm robotic manipulators is fraught with problems. For example, generally among these methods the existence of a reliable solution to the iterative computation is not guaranteed and the calculations are computationally demanding and time consuming, leading to delays, especially in the abort function. Suboptimal acceleration profiles and defective trajectory profiles cause acceleration tracking difficulties and throughput loss. Trajectories change drastically for small variations in departure and destination positions. A large memory is required to store trajectory points, and different settings are required for different arms/speeds.
A number of typical defects that occur with existing trajectory generation in substrate transport apparatus are illustrated in the acceleration vs. time profiles in
FIGS. 1-10
, with the defects being indicated by circles. Specifically,
FIGS. 1-6
variously show radial extension of the arms and
FIGS. 7-10
show rotational movement. It will be seen that the smoothness of the acceleration profiles is interrupted at the portions of the curves indicated by the circles.
Another drawback of the existing approach, typified by that in U.S. Pat. No. 5,655,060, is that individual moves must be executed sequentially with no provision for blending simple moves into a single trajectory to create a single smooth transfer path. The sequential execution requires stops between the individual moves and increases the overall travel time.
Problem to be Solved
Thus, there is a need in the art for an approach that will achieve trajectory generation in multi-arm robotic manipulators with reliable and numerically efficient calculation of time-optimum trajectories having easy-to-track or continuous acceleration profiles for controlling the movement of the multi-arms of the manipulators. There is also a need for an approach that generates trajectories for simple moves that can be blended to create a smooth non-stop transfer path, and a method to achieve this blending.
Objects
It is accordingly an object of the present invention to provide a method and means for the reliable and numerically efficient generation of time-optimum trajectories with easy-to-track or continuous acceleration profiles for controlling the simple movement of multi-arm robotic manipulators, such as an extension and retraction move along a straight line, or a rotary move following a circular arc, with velocity, acceleration, and jerk constraints.
It is another object of the invention to provide a system for the reliable and numerically efficient generation of time-optimum trajectories with smooth acceleration profiles for controlling the movement of multi-arm robotic manipulators in a substrate transport apparatus, such as, but not limited to, an extension and retraction move along a straight line, or a rotary move following a circular arc, with velocity, acceleration, and jerk constraints on the arm-mounted end effector carrying a substrate.
It is a further object of the invention to provide a system for the reliable and numerically efficient generation of time-optimum trajectories for simple and blended moves of multi-arm robotic manipulators, such as, but not limited to, an extension and retraction along a straight line or a rotary move following a circular arc, with velocity, acceleration, and jerk constraints.
It is also an object of the invention to provide a system and method for generating trajectories for simple moves of multi-arm robotic manipulators, which moves can be blended to create a smooth non-stop transfer path.
SUMMARY OF THE INVENTION
The present invention is directed to providing a method and means for the reliable and numerically efficient generation of time-optimum trajectories with easy-to-track or continuous acceleration profiles for simple and blended moves of multi-arm robotic manipulators, such as, but not limited to, an extension and retraction move along a straight line or a rotary move following a circular arc, with velocity, acceleration, jerk, and in some cases jerk rate, constraints. A time-optimum trajectory is understood to be the set of the position, velocity, and acceleration profiles which describe the move of a selected end effector along a given path in the shortest time possible without violating given constraints, with a special case being an optimum abort trajectory, which brings the moving arm into complete rest in the shortest time. More particularly, the invention involves firstly identifying the set of fundamental trajectory shapes which cover all possible combinations of constraints for a given category of moves, e.g., a move along a straight line or along a circular arc; next, decomposing the fundamental shapes into segments where a single constraint is active; and, then, determining the time optimum paths in the segments. As a result, a unique design of time-optimum trajectories is produced based on a set of pre-defined trajectory shapes.
The invention also involves the blending of simple moves into a single trajectory by decomposing trajectories of the individual moves into their orthogonal components and overlapping them for a given time interval, which results in a non-stop move along a smooth transfer path.
REFERENCES:
patent: 4218172 (1980-08-01), Freund
patent: 5647724 (1997-07-01), Davis, Jr. et al.
patent: 5655060 (1997-08-01), Lucas
Chen et al., “Time-Optimal Control of Two-Degree of Freedom Robot Arms”, IEEE., pp. 1210-1215, 1988.*
Bobrow et al., “Minimum-Time Trajectories for Two Robots Holding the Same Workpiece”, IEEE. pp. 3102-3107, 1990.*
Ghalia et al., “A Robust Trajectory Tracking Control of Industrial Robot Manipulators Using Fuzzy Logic”, IEEE., pp. 268-271, 1995.
Elmali Hakan
Hosek Martin
Brooks Automation Inc.
Cuchlinski Jr. William A.
Marc McDieunel
Perman & Green LLP
LandOfFree
System of trajectory planning for robotic manipulators based... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with System of trajectory planning for robotic manipulators based..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and System of trajectory planning for robotic manipulators based... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2550371