Scalable motion control system

• US 20070010898A1
• Filed: 07/11/2005
• Published: 01/11/2007
• Est. Priority Date: 06/08/2005
• Status: Active Grant

• Current Assignee: Brooks Automation Ltd. (United Kingdom) (Azenta, Inc.)
• Original Assignee: Brooks Automation Incorporated (Azenta, Inc.)
• Inventors: Caveney, Robert, Beale, Stuart, Hofmeister, Christopher, Hosek, Martin, Coady, Matthew, Ives, Mark, Botev, Roumen, Moura, Jairo
• Granted Patent: US 7,904,182 B2
• Time in Patent Office: Days
• US Class Current: 700/2
• CPC Class Codes: G05B 19/4148 characterised by using several processors for different functions, distributed (real-time) systems G05B19/4141 takes precedence
• CPC Class Codes: G05B 19/4185 characterised by the network communication
• CPC Class Codes: G05B 2219/31207 Master sends global files to autonomous controllers, feedback of process status
• CPC Class Codes: G05B 2219/33277 Distributed system with host as leader, host with multiple of agents
• CPC Class Codes: Y02P 90/02 Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

Abstract

A control system includes a clustered architecture having a master controller, a central control section including one or more first remote controllers under direct control of the master controller, and a distributed control section including a cluster controller controlled by the master controller. The cluster controller controls the activities of one or more second remote controllers. Each of the first and second remote controllers are utilized to drive one or more axes.

Claims

1. A control system comprising:

a clustered architecture having a master controller;

a central control section including one or more first remote controllers under direct control of the master controller;

a distributed control section including a cluster controller controlled by the master controller, wherein the cluster controller controls the activities of one or more second remote controllers;

wherein each of the first and second remote controllers are utilized to drive one or more axes.

2. The system of claim 1, further comprising circuitry for generating a trajectory for the one or more axes in terms of a position, velocity, and acceleration for each point of a plurality of points on the trajectory, and for calculating inverse dynamic models of the axes to determine a gain value and a feedforward term for each point on the trajectory for each axis.

3. The system of claim 1, further comprising:

circuitry for synchronizing nodes of the control system by issuing a start message including a time stamp indicating the time the message was sent to each node; and

circuitry for compensating for a difference between a time indicated by the time stamp and a time a high resolution clock was updated at each node.

4. The system of claim 1, further comprising extensions to a communication protocol for communicating among the master controller, the first remote controllers, the cluster controller and the second remote controllers, wherein the extensions provide a specific usage scheme and message format.

5. The system of claim 4, wherein at least one of the first or second remote controllers include a control port and a data port, wherein messages received by the control port identify a type of message received by the data port.

6. The system of claim 1, further comprising a distributed event capture capability, wherein one or more remote controllers operate to record and notify other remote controllers of a time of a trigger event.

7. The system of claim 6, wherein the other remote controllers buffer predetermined data points and interpolate among the buffered data points to determine a value at the trigger event time.

8. The system of claim 1, further comprising a wireless communication network through which two or more network nodes communicate.

9. The system of claim 1, wherein a network node of the control system operates to:

calculate an operating parameter value for an end effector of an axis; and

generate a motion profile for an individual joint of the axis such that a motion profile for the end effector does not exceed the operating parameter value.

10. The system of claim 1, wherein a first network node of the control system operates to issue a periodic message and a second network node of the control system is disabled if the message is not received within a time period.

11. The system of claim 1, wherein circuitry of the control system operates to:

determine if power has been lost to a system axis;

apply a trajectory to the axis that brings the axis to a zero velocity within a predetermined time period; and

remove power from the axis at the end of the predetermined time period.

12. The system of claim 1, wherein the master controller operates to issue a start message including a time stamp indicating the time the message was sent, and each network node of the control system operates to update a clock using the time stamp, and compensate for a difference between a time indicated by the time stamp and a time the clock was updated.

13. A method of operating an axis of a control system comprising:

generating a trajectory for the axis in terms of a position, velocity, and acceleration for each point of a plurality of points on the trajectory; and

calculating an inverse dynamic model of the axis to determine a gain value and a feedforward term for each point.

14. The method of claim 13, comprising grouping the position, velocity, acceleration, gain value, and feedforward term for each point into a frame.

15. The method of claim 14, comprising interpolating between two consecutive frames to obtain an instantaneous position, instantaneous velocity, instantaneous feedforward term and instantaneous gain value utilized to control the axis.

16. A method of synchronizing nodes on a network comprising:

issuing a start message including a time stamp indicating the time the message was sent;

updating a high resolution clock using the time stamp; and

compensating for a difference between a time indicated by the time stamp and a time the high resolution clock was updated.

17. The method of claim 16, wherein compensating for a difference comprises compensating for a propagation delay of the start message.

18. A message set for communicating among nodes of a control system comprising:

an action message for exchanging commands and command responses;

an event message for reporting data relating to a predetermined event to a master controller;

a string message for providing a serial message channel between a remote controller and the master controller; and

a data port message for sending data to a network node.

19. The message set of claim 18, wherein the data port message further comprises a position, velocity, time, feedforward and gain (PVTFG) message having:

a timestamp;

a commanded position; and

a commanded velocity, wherein the PVTFG message provides time-stamped trajectory set point data to one or more control system nodes.

20. The PVTFG message of claim 19, further comprising a feed forward term.

21. The PVTFG message of claim 19, further comprising a gain term.

22. The PVTFG message of claim 19, further comprising a torque limit term.

23. The message set of claim 18, wherein the data port message further comprises a status message having:

a status word;

an actual position term;

an term indicating certain I/O device states;

a timestamp;

a commanded position; and

an actual velocity term.

24. The message set of claim 18, further comprising a trace message for sending time stamped, sampled data to the master controller.

25. A method of obtaining axis data at the time of an event, comprising:

buffering data at one or more axis nodes;

recording time information of a triggering event occurring at a triggering event node of the one or more axis nodes; and

processing the buffered data to determine a set of values at a time period indicated by the recorded time information.

26. The method of claim 25, comprising sending the recorded time information to the one or more axis nodes.

27. The method of claim 26, comprising processing the buffered data at the one or more axis nodes.

28. The method of claim 27, further comprising sending the set of values to a node controller operating to control the one or more axis nodes.

29. The method of claim 25, comprising sending the recorded time information to a node controller operating to control the one or more axis nodes.

30. The method of claim 29, comprising sending the buffered data to the node controller and processing the buffered data at the node controller.

31. The method of claim 25, comprising sending the recorded time information to the one or more axis nodes from the triggering event node.

32. The method of claim 25, wherein sending the recorded time information to the one or more axis nodes comprises sending the recorded time information to a node controller operating to control the one or more axis nodes and then to the one or more axis nodes from the node controller.

33. The method of claim 25, further comprising sending the set of values to a node controller operating to control the one or more axis nodes.

34. A control system comprising:

a plurality of nodes organized in a clustered architecture; and

a wireless communication network through which two or more of the nodes communicate.

35. The control system of claim 34, wherein the plurality of nodes includes groups of kinematically coupled axes.

36. The control system of claim 34, wherein the plurality of nodes includes one or more axis end effectors.

37. The control system of claim 34, wherein the plurality of nodes includes one or more loadports.

38. The control system of claim 34, wherein the wireless communication network provides one or more secure connection protocols.

39. The control system of claim 34, wherein the one or more secure connection protocols includes a CIP protocol.

40. The control system of claim 34, wherein the one or more secure connection protocols includes a Bluetooth protocol.

41. The control system of claim 34, wherein the one or more secure connection protocols includes an 802.x wireless protocol.

42. A method for controlling an axis of a control system comprising:

calculating an operating parameter value for an end effector of the axis;

generating a motion profile for an individual joint of the axis such that a motion profile for the end effector does not exceed the operating parameter value.

43. The method of claim 42, wherein the operating parameter value is a maximum velocity.

44. The method of claim 42, wherein the operating parameter value is a maximum torque.

45. A method for controlling an axis comprising:

calculating a velocity and a torque for a position of the axis;

predetermining a first maximum time period during which an axis velocity may exceed the calculated velocity;

predetermining a second maximum time period during which an axis torque may exceed the calculated torque;

disabling the axis if the first or second maximum time period is exceeded.

46. The method of claim 45, comprising disabling the axis if the calculated velocity exceeds a predetermined maximum velocity.

47. The method of claim 48, comprising disabling the axis if the calculated torque exceeds a predetermined maximum torque.

48. The method of claim 45, comprising disabling the axis upon failure to receive a periodic communication from the axis.

49. The method of claim 45, comprising disabling the axis upon failure to receive a periodic communication from an axis controller.

50. A method of verifying the integrity of data transmitted over a control system network comprising:

storing operating parameters at a node on the network; and

verifying that commands received through the network do not cause operations of the node that exceed the operating parameters.

51. The method of claim 50, comprising disabling the node if the commands cause operations of the node to exceed the operating parameters

52. The method of claim 51, wherein the operating parameters include a maximum axis velocity.

53. The method of claim 50, wherein the operating parameters include an axis velocity error.

54. The method of claim 50, wherein the operating parameters include a time during which a maximum velocity may be exceeded.

55. The method of claim 50, wherein the operating parameters include a maximum axis torque.

56. The method of claim 50, wherein the operating parameters include a time during which a maximum torque may be exceeded.

57. A method of verifying the integrity of a control system network comprising:

issuing a periodic message; and

disabling one or more nodes of the control system network if the message is not received within a time period.

58. The method of claim 57, wherein the message is a position velocity time message frame.

59. The method of claim 57, wherein the message is issued by a network controller and the one or more nodes are disabled if a first node of the one or more nodes does not receive the message.

60. The method of claim 57, wherein the message is issued by the one or more nodes and the one or more nodes are disabled if a network controller does not receive the message.

61. The method of claim 57, comprising removing power from selected ones of the one or more nodes if the message is not received within a time period.

62. A method of maintaining the integrity of a control system network comprising:

assigning nodes of the network into zones such that motion in a first zone is isolated from motion in zones other than the first zone; and

controlling the zones so that events of the first zone do not effect the operation of zones other than the first zone.

63. The method of claim 62, comprising disabling the first zone and routing work designated for the first zone to a zone other than the first zone.

64. A method of bringing an axis to a controlled stop comprising:

determining if power has been lost to a system including the axis;

applying a trajectory to the axis that brings the axis to a zero velocity within a predetermined time period; and

removing power from the axis at the end of the predetermined time period.

65. The method of claim 64 wherein the predetermined time period is determined by calculating a time remaining before power is lost to the axis.

66. A method for compensating for synchronization delays in a control system comprising:

determining a delay between a network node issuing a message and a network node receiving the message; and

using the determined delay to adjust trajectory data for the receiving node.

67. The method of claim 66, wherein the delay is determined by assuming a fixed delay.

68. The method of claim 66, wherein the delay is determined by counting a number of network nodes through which a message passes before arriving at the receiving node.

69. The method of claim 66, wherein the delay is determined by measuring a time for a message to travel from the issuing node to the receiving node.

70. A method of operating a robot comprising:

recording an idle time of the robot;

determining performance characteristics of the robot upon exceeding an idle time threshold;

directing the robot to perform a warm up exercise if the determined performance characteristics do not meet a specification.

71. An application program interface for a motion control system comprising:

a standardized set of interface conventions for exchanging information among components of the motion control system; and

a generalized command set that provides general commands to perform operations and specific arguments to identify particular components and actions for performing the operations.

72. The application program interface of claim 71, wherein the command set includes a command for picking material from a material source location using a robot, comprising:

an argument specifying the primary actor for the pick operation;

an argument specifying an actor index, usually the tip to be used for the pick operation;

an argument specifying a device currently holding the material; and

an argument specifying an index into the device holding the material.

73. The application program interface of claim 71, wherein the command set includes a command for placing material to a material destination location using a robot, comprising:

an argument specifying a primary actor for the place operation;

an argument specifying an actor index;

an argument specifying a destination object; and

an argument specifying an index into the destination object.

74. The application program interface of claim 71, wherein the command set includes a command for moving a robot to a specified material source for a pick operation, comprising:

an argument specifying a primary actor for the pick operation;

an argument specifying an actor index;

an argument specifying a the material source currently holding a material; and

an argument specifying an index into the material source.

75. The application program interface of claim 71, wherein the command set includes a command for moving a robot to a specified material source for a place operation, comprising:

an argument specifying a primary actor for the place operation;

an argument specifying an actor index;

an argument specifying a destination object; and

an argument specifying an index into the destination object.

76. The application program interface of claim 71, wherein the command set includes a command for moving a substrate from a material source to a destination, comprising:

an argument specifying a primary actor to be used for moving the substrate;

an argument specifying an actor index;

an argument specifying the material source;

an argument specifying an index of the material source;

an argument specifying a destination object; and

an argument specifying an index of the destination object.

77. The application program interface of claim 71, wherein the command set includes a command for mapping a resource using a mapping device, comprising:

an argument identifying the mapping device; and

an argument identifying the resource to be mapped.

78. The application program interface of claim 71, wherein the command set includes a command for initializing a resource, comprising an argument specifying a resource to initialize.

79. The application program interface of claim 71, wherein the command set includes a command for initializing a resource based on a strategy, comprising an argument specifying a recipe for accomplishing the strategy.