Data processing: generic control systems or specific application – Specific application – apparatus or process – Robot control
Reexamination Certificate
2002-07-15
2003-11-04
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Robot control
C700S247000, C700S248000, C700S249000, C700S250000, C700S258000, C700S259000, C700S260000, C700S261000, C700S262000, C700S263000, C700S264000, C700S900000, C414S754000, C414S777000, C414S757000, C414S814000, C701S023000, C074S490030
Reexamination Certificate
active
06643563
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a robotic manipulator and, more particularly, to planning, optimizing and controlling movement of a robotic manipulator.
2. Brief Description of Related Developments
Manufacturing technology for semiconductor integrated circuits (IC) and flat panel displays (FPD) includes processing of substrates such as silicon wafers or glass panels. The manufacturing technology typically includes a cluster tool which consists of a circular vacuum chamber with robot stations, such as load locks and process modules, connected radially at the circumference of the chamber in a star pattern. The cluster tool is serviced by a robot which is located at the center of the chamber and cycles the substrates from the load locks through the process modules and back to the load locks. In this process, the robot arm rotates, extends and retracts radially in a horizontal plane.
In order to position the substrate to a given point in the plane of operation, the robot arm needs to be capable of a planar motion with two degrees of freedom (DOF). Since the robot stations are connected radially to the chamber, the orientation of the end-effector needs to be kept radial regardless of the position of the robot arm. Typical arm designs include telescoping, scara and frogleg mechanisms. Examples of typical transport apparatus including such embodiments are described in U.S. Pat. Nos. 4,730,976, 4,715,921, 5,180,276, 5,404,894, 5,647,724, and 5,765,983, which are hereby incorporated by reference herein. In many applications, the robot arm is mounted on a vertical lift drive which provides an additional degree-of-freedom required for servicing stations at different vertical levels.
Typical drawbacks of the radial star pattern of the tool design include a relatively large footprint and inconvenient geometry for interfacing other processes in the factory. As a result, cluster tools with robot stations arranged in a non-radial manner have been introduced. A typical example is an atmospheric transfer module which serves as an interface between standardized load ports serviced by an external transportation system and load locks of a conventional vacuum cluster tool. In order to access non-radial stations, the robot arm needs to be capable of positioning the end-effector to a given point with a specified orientation, i.e., providing three degrees of freedom in the plane of operation. A conventional 2DOF robot manipulator cannot access non-radial stations.
A planar three-degree-of-freedom (3DOF) robotic arm refers to a mechanical device that can position a payload in the plane of operation to a given point with a specified orientation. A typical example of such a mechanism is a planar three-link manipulator, or robot arm, comprising an upper arm, forearm and end-effector that are coupled and actuated through revolute joints. The revolute joints are referred to as the shoulder, elbow and wrist joints, respectively. An alternative is a four-link design, as typified by U.S. Pat. No. 5,789,890, which is hereby incorporated by reference herein.
In order to move the end-effector of the robot arm from its initial location to a specified destination position, a path along which the robot end-effector moves is determined. The generation of the path is an objective of trajectory planning. Examples of trajectory generation are described in U.S. Pat. Nos. 5,655,060 and 6,216,058, which are hereby incorporated by reference herein. Trajectory planning calculates motion profiles for robot actuators (motors) which drive the robot arm so that a smooth motion of the end-effector along the desired path is achieved. The motion profiles are typically generated in terms of position, velocity and acceleration of the robot actuators, and are fed to the robot motion controller as reference control inputs. Path planning for typical pick-place robotic manipulators depends primarily on the geometry of the robot workspace and the particular task performed. However, the motion profiles may be constrained by, for example, the speed-torque characteristics of the robot actuators, maximum allowable acceleration of the end-effector to prevent payload slippage, or maximum allowable velocity to comply with safety-related requirements.
In order to keep the substrate near the original position at the entrance of the station while aligning the end-effector with the desired access path when the robotic manipulator is under manual control or in a station teaching mode, rotational motion of the end-effector with respect to the wrist joint of the robotic arm is required. However, the rotational motion of the end-effector with respect to the wrist joint can move the substrate from the original position near the entrance of the work station. An iterative approach involving repeated translations of the robotic manipulator is required to keep the substrate near the original position at the entrance of the work station while aligning the end-effector with the desired access path. This requires repeated attempts and more time to move the end-effector of the robotic arm to its desired position and orientation.
The trajectory planning must be completed before the robot arm can be moved. Therefore, the more complex the calculations for determining the path and generating the motion profiles, and the greater the number of calculations required, the more time is required to move the robot arm. Alternatively, more powerful and more expensive controllers can be employed. In addition, since the motion profiles are calculated at equally spaced time instants before the motion of the robotic manipulator starts, a large amount of data associated with the motion profiles must be stored in the controller, resulting in large memory requirements and expensive memory components.
Once the motion profiles have been generated, motion control determines commanded torques for the robot actuators so that the robot actuators track the desired motion profiles. Typical centralized control architectures are not suitable for robotic manipulators with actuators installed in the robotic arm because a large number of long signal wires must be fed through the links, joints and slip-rings of the robotic arm, which translates to high assembly costs and reliability risks. Typical distributed control approaches either run independent joint-based feedback loops, which do not account for dynamic coupling between links and other members of the robotic manipulator and, therefore, provide limited trajectory tracking performance, or utilize high-speed communication networks to share run-time data, which is technically difficult to implement for robotic arms with slip-rings at the joints due to noise, communication bandwidth and reliability related issues.
SUMMARY OF THE INVENTION
The present invention is directed to a method for moving a substrate to a predetermined location with a specified orientation with a robotic manipulator, the robotic manipulator having a plurality of joint actuators and an end-effector for holding the substrate, wherein the end-effector is independently rotatable with respect to the remaining robotic manipulator. In one embodiment, the method comprises selecting a reference point on the end-effector for determining a position of the end-effector, wherein the reference point is offset from a wrist of the robotic manipulator, and determining a motion path for movement of the reference point on the end-effector of the robotic arm toward a predetermined location with a specified orientation. Motion profiles are generated for translation of the reference point on the end-effector along the motion path and rotation of the end-effector with respect to the reference point. The motion profiles are converted into joint motion profiles for each of the joint actuators of the robotic manipulator for implementing the movement of the end-effector to the predetermined location with the specified orientation.
The present invention is directed to an apparatus for movement of a substrate to a predetermined location with a
Elmali Hakan
Hosek Martin
Brooks Automation Inc.
Cuchlinski Jr. William A.
Marc McDieunel
Perman & Green LLP
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