Trajectory planning and motion control strategies for a planar three-degree-of-freedom robotic arm

• US 20030108415A1
• Filed: 07/15/2002
• Published: 06/12/2003
• Est. Priority Date: 07/13/2001
• Status: Active Grant

• Current Assignee: Brooks Automation Ltd. (United Kingdom) (Azenta, Inc.)
• Original Assignee: Brooks Automation Incorporated (Azenta, Inc.)
• Inventors: Hosek, Martin, Elmali, Hakan
• Granted Patent: US 6,643,563 B2
• Time in Patent Office: Days
• US Class Current: 414/783
• CPC Class Codes: B25J 9/1664 characterised by motion, path, trajectory planning
• CPC Class Codes: G05B 2219/39246 Control position and orientation of handled object
• CPC Class Codes: G05B 2219/40513 Planning of vehicle and of its manipulator arm
• CPC Class Codes: H01L 21/67739 into and out of processing chamber
• CPC Class Codes: Y10S 700/90 Special robot structural element
• CPC Class Codes: Y10T 74/20317 including electric motor

Abstract

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. 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, determining a motion path for movement of the end-effector of robotic arm toward predetermined location with specified orientation, and generating motion profiles for translational and rotational components of movement of the end-effector of robotic manipulator along the motion path. 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 predetermined location with the specified orientation.

Claims

1. 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, the method comprising the steps of:

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;

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;

generating motion profiles 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; and

converting the motion profiles 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.

2. The method of claim 1, wherein determining the motion path comprises defining a set of points along the motion path for movement of the reference point on the end-effector through the points.

3. The method of claim 2, wherein determining the motion path comprises generating straight line legs between the points to create a substantially continuous path.

4. The method of claim 3, wherein generating the motion profiles includes generating a motion profile for each leg.

5. The method of claim 4, wherein generating the motion profiles along the straight line legs of the motion path includes specifying a set of constraints for each of the legs.

6. The method of claim 5, wherein specifying a set of constraints includes defining maximum velocities, accelerations, jerks and jerk rates for translational and rotational movement of the end-effector for each of the legs.

7. The method of claim 4, wherein generating the motion profiles along the straight line legs of the motion path includes the steps of:

decomposing each leg into a translation of the reference point with respect to each leg to determine the length of each leg; and

determining the rotation of the end-effector with respect to the reference point for each leg to calculate the angular increment of the rotation for each leg.

8. The method of claim 3, wherein generating the motion profiles includes synchronizing the translational and rotational components for each leg so that the translational and rotational components of movement of the end-effector begin at the same time.

9. The method of claim 3, wherein generating the motion profiles includes synchronizing the translational and rotational components of each leg so that the translational and rotational components of movement of the end-effector end at the same time.

10. The method of claim 9, wherein synchronizing includes adjusting the constraints for each leg.

11. The method of claim 4, wherein generating the motion profile for each leg includes decomposing a leg into a plurality of sub legs which can be fully or partially overlapped if constraints associated with the links or actuators of the robotic manipulator are exceeded.

12. The method of claim 1, wherein the step of selecting the reference point includes selecting a center of the substrate holding area on the end-effector as the reference point.

13. The method of claim 1, wherein determining the motion path includes determining whether the predetermined location has a non-radial orientation with respect to the robotic manipulator, and if so, designating a via point so as to be able to generate motion path containing straight-line legs.

14. The method of claim 1, wherein generating the motion path comprises selecting one of at least two different paths for obstacle avoidance and throughput optimization of the robotic manipulator.

15. The method of claim 14, wherein selecting one of at least two different paths comprises selecting a single-leg path or a two-leg path for a leg of the selected path between a retracted position of the robotic manipulator and a via point.

16. An apparatus for movement of at least one substrate to a predetermined location with a specified orientation, comprising:

a robotic manipulator having a plurality of joint actuators and at least one end-effector for holding at least one substrate, wherein the at least one end-effector is independently rotatable with respect to the remaining robotic manipulator;

a controller connected to the robotic manipulator for generating motion profiles for movement of a substrate holding area of the end-effector along a desired motion path, wherein the controller is programmed for forming the motion profiles from a combination of a translation of the reference point along the motion path and rotation of the end-effector with respect to the reference point, the reference point on the end-effector being offset from a wrist of the robotic manipulator; and

wherein

the controller is adapted to determine a joint motion profile for each of the joint actuators of the robotic manipulator for implementing the motion profiles for movement of the end-effector to the predetermined location with the specified orientation.

17. The apparatus of claim 16, wherein the robotic manipulator includes at least two end-effectors.

18. A method for moving a substrate with a robotic manipulator to a predetermined location with a specified orientation, the method comprising the steps of:

providing the robotic manipulator with a plurality of joint actuators and an end-effector for holding the substrate at an end of the robotic manipulator;

providing a first controller in communication with the robotic manipulator for determining the desired joint motion profiles and desired commanded torques for the joint actuators associated with the first controller;

providing a second controller in communication with the robotic manipulator for determining the desired joint motion profiles and desired commanded torques for the joint actuators associated with the second controller;

generating with the first controller nodal points of motion profiles in the first controller for translation and rotation of the end-effector along the motion path;

transmitting the nodal points from the first controller to the second controller; and

initiating a synchronized run-time calculation of the motion profiles in the first controller and in the second controller based on the generated nodal points in the first controller and in the second controller, wherein the run-time calculation in the first controller and in the second controller are performed separately of each other.

19. The method of claim 18, further comprising determining the joint motion profiles for the joint actuators associated with the second controller in accord with the run-time calculation of the motion profiles for translation and rotation of the end-effector at the second controller and independent of the first controller.

20. The method of claim 18, further comprising determining the joint motion profiles for the joint actuators associated with the first controller in accord with the run-time calculation of the motion profiles for translation and rotation of the end-effector at the first controller and independent of the second controller.

21. The method of claim 18, wherein determining the desired commanded torques for the joint actuators associated with the first controller and with the second controller includes accounting for dynamic coupling between members of the robotic manipulator without sharing of run-time data between the first controller and the second controller.

22. An apparatus for moving a substrate with a robotic manipulator to a predetermined location with a specified orientation, the apparatus comprising:

an end-effector for holding the substrate at an end of the robotic manipulator, wherein the robotic manipulator has a plurality of joint actuators;

a first controller in communication with the robotic manipulator for determining the desired position of the joint actuators associated with the first controller;

a second controller in communication with the robotic manipulator for determining the desired position of the joint actuators associated with the second controller;

wherein the first controller is adapted to generate nodal points of the motion profiles in the first controller for translation and rotation of the end-effector along the motion path, and to transmit the nodal points from the first controller to the second controller; and

a communication line connecting the first controller and the second controller for transmitting nodal points from the first controller to the second controller, wherein the first controller and the second controller separately perform run-time calculation of the motion profiles based on the generated nodal points in the first controller and in the second controller, and the run-time calculation is initiated synchronously.

23. The apparatus of claim 22, wherein the second controller is coupled with the robotic manipulator for controlling the end-effector and minimizing the length of signal lines between the second controller and the joint actuator associated with the second controller and with the end-effector.

24. The apparatus of claim 22, wherein the second controller determines the positions of the joint actuators associated with the second controller in accord with the run-time calculation of the motion profiles at the second controller, and wherein the first controller determines the positions of the joint actuators associated with the first controller in accord with the run-time calculation of the motion profiles at the first controller.

25. A method for moving substrate between two points with a robotic arm having a distributed control system, a plurality of joint actuators for moving the robotic arm, and an end-effector for removeably retaining the substrate, the method comprising the steps of:

generating motion profiles with a main controller coupled to the robotic arm for controlling at least one from the plurality of the joint actuators associated with the main controller;

generating the motion profiles with a remote controller coupled to the robotic arm for controlling at least one other from the plurality of joint actuators associated with the end-effector; and

executing the motion profiles in the main controller and the motion profile in the remote controller separately from each other, wherein the executing is synchronously initiated.

26. A robotic arm with a distributed control system and an end-effector for moving substrate between two points, comprising:

joint actuators coupled to the robotic arm for controlling the position and orientation of the robotic arm;

a main controller for generating motion profiles for controlling at least one joint actuator associated with the main controller from the joint actuators coupled to the robotic arm;

a remote controller for generating the motion profiles for controlling at least one other joint actuator associated with the end-effector from the joint actuators coupled to the robotic arm, wherein the substrate is removeably attached to the end-effector; and

wherein the main controller and remote controller each execute their motion profiles separately from each other, wherein the execution is synchronously initiated.

27. The robotic arm of claim 26, further comprising:

a software module implemented in the main controller and in the remote controller for generating the motion profiles, wherein the motion profiles are a translation of a reference point between two points and rotation of the end-effector with respect to the reference point, wherein the reference point is selected on the end-effector for determining the position of the end-effector along a motion path.